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UCL dissertation focusing on the environmental impacts of rare earth oxide production in two Chinese mines.
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Production of rare earth oxides
Assessment of the environmental impacts in two Chinese mines
Dissertation for the Master of Science in
Environmental Systems Engineering
A l ä n d j i B O U O R A K I M A
S u p e r v i s o r : J u l i a S T E G E M A N N
University College London
Department of Civil, Environmental & Geomatic Engineering London, United Kingdom, September 2011
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Abstract
The recent interest in environmental friendly technologies has created a significant increase in the demand of rare earths. Rare earths are indeed used in many applications (e.g. car electric batteries, rechargeable batteries, energy saving light bulbs) because of their specific properties. As such, it was interesting to shed a light on the environmental cost of producing these rare earths.
Thus, this study aims at determining the different environmental impacts from producing rare earth. It appraises the impacts from the mining of virgin ore until the production of rare earth oxides (which is the most commonly used and produced form of rare earth). This study focuses on two Chinese deposits (Bayan Obo and Maoniuping) that account for 70% of the world production of rare earths.
After two literature reviews describing firstly the rare earth market and then the processes used in the two deposits, the emphasis is laid on the life cycle assessment methodology. Based on both data collected in the literature reviews and personal estimations, the life cycle assessment is carried out using a standardised methodology.
As a result, the environmental impacts of producing rare earth oxide are assessed regarding the following categories: global warming, acidification, eutrophication, radioactive waste generation, land use and toxicity in wastewaters.
To conclude, on the one hand this study provides an extensive analysis of rare earths in general, then it describes in detail the two biggest mines presently in operations. On the other hand, the life cycle assessment methodology provides results concerning six different impact categories. These results are potentially generalizable since it appraises generic processes to this industry. This study can be useful to whoever is trying to measure the environmental impacts of a product that contains rare earth oxides.
Keywords: rare earths, rare earth oxide, life cycle assessment, Chinese rare earths,
Bayan Obo, Baotou, Maoniuping, environmental impacts.
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Acknowledgement
I would like to thank Julia Stegemann whose help was invaluable to me. She gave me the proper advices at the proper times and helped me to design this study from the beginning to the end. Thanks to her, I have enjoyed carrying out this study.
I also would like to express my thanks to Marie for her support.
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Table of contents
1. Introduction ....................................................................................................... 15 1.1. Background information ............................................................................. 15 1.2. Aim of the study ......................................................................................... 16 1.3. Objectives ................................................................................................... 16 1.4. Approach .................................................................................................... 16
2. Information on rare earth elements .................................................................... 17 2.1. How rare are rare earths? ............................................................................ 17 2.2. Description of the main rare earth minerals ............................................... 18 2.3. Description of the rare earth reserves ......................................................... 22 2.4. Historical production of rare earth oxide .................................................... 22 2.5. Description of the main applications of the rare earth elements ................ 24
3. Production of rare earth elements ...................................................................... 27 3.1. World production of rare earth elements .................................................... 27 3.2. Chinese production of rare earths ............................................................... 27 3.3. Prospective other productions .................................................................... 30
4. Scope refining .................................................................................................... 32 5. Bayan Obo deposit ............................................................................................ 32
5.1. Description of the deposit ........................................................................... 32 5.2. Composition of the original ore .................................................................. 32 5.3. Description of the beneficiation process .................................................... 32 5.4. Composition of the mixed rare earth concentrate ....................................... 34 5.5. Processing of the mixed rare earth concentrate .......................................... 34 5.6. Obtaining of rare earth oxides .................................................................... 34
6. Maoniuping deposit ........................................................................................... 37 6.1. Description of the deposit ........................................................................... 37 6.2. Composition of the original ore .................................................................. 38 6.3. Description of the beneficiation process .................................................... 38 6.4. Processing of the mixed rare earth concentrate .......................................... 40 6.5. Obtaining of rare earth oxides .................................................................... 40
7. Life cycle assessment methodology .................................................................. 42 8. Goal definition and scope .................................................................................. 42
8.1. Goal of the life cycle assessment ................................................................ 42 8.2. Level of specificity ..................................................................................... 43
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8.3. Display of results ........................................................................................ 43 8.4. Scope of the life cycle assessment .............................................................. 43 8.5. Guideline to life cycle assessment methodology ........................................ 43
9. Process Modelling: ............................................................................................ 43 9.1. Bayan Obo deposit ..................................................................................... 43 9.2. Maoniuping deposit .................................................................................... 51
10. Life Cycle inventory ........................................................................................ 57 10.1. Input of chemicals, energy and explosives ............................................... 57 10.2. Air emissions ............................................................................................ 57 10.3. Output of wastes and chemicals ............................................................... 57
11. Life Cycle Impact Assessment ........................................................................ 62 11.1. Global Warming ....................................................................................... 62 11.2. Acidification ............................................................................................. 63 11.3. Eutrophication .......................................................................................... 64 11.4. Radioactive waste generation ................................................................... 64 11.5. Land use ................................................................................................... 65 11.6. Toxic chemical discharge in wastewater .................................................. 65
12. Life Cycle Interpretation ................................................................................. 67 12.1. Identification of the significant issues ...................................................... 67 12.2. Completeness, sensitivity and consistency of data ................................... 68 12.3. Conclusions of the life cycle assessment .................................................. 70
13. Conclusion ....................................................................................................... 74
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List of figures
Figure 1: Relative abundance of chemical elements in the Earth's crust (Haxel 2002) ..... 17 Figure 2: Concentrations of rare earth elements in the Earth’s crust (Tyler 2004) ........... 18 Figure 3: Contents of the main rare earth elements in bastnaesite for two mines
(Kingsnorth 2010) ............................................................................................. 19 Figure 4: Contents of the main rare earth elements in monazite for three deposits
(Kingsnorth 2010) ............................................................................................. 20 Figure 5: Contents of the main rare earth elements in xenotime (Kingsnorth 2010) ........ 20 Figure 6: Contents of the main rare earth elements in Chinese ionic clays (Kingsnorth
2010) .................................................................................................................. 21 Figure 7: Breakdown of the economically viable rare earth resource (USGS 2011) ........ 22 Figure 8: Global production of rare earth oxide (USGS 2010) ......................................... 23 Figure 9: World production of rare earth oxides from 1950 to 2000 (Haxel 2002) .......... 23 Figure 10: Global rare earth consumption in 2006 (Roskill 2007) .................................... 24 Figure 11: Global production of rare earth oxides in 2010 (USGS 2011) ......................... 27 Figure 12: Breakdown of rare earth oxide-content at Bayan Obo (Crédit Suisse 2011) ... 28 Figure 13: Bastnaesite content of rare earth elements at Maoniuping (Spooner 2005) ..... 29 Figure 14: Ionic clay content of rare earth elements at Longnan (Crédit Suisse 2011) ..... 29 Figure 15: Distribution of the Chinese production of rare earths in 2010 ......................... 30 Figure 16: Composition by weight of the mixed bastnaesite-monazite concentrate
(Wang et al. 2002) ............................................................................................. 34 Figure 17: Composition of a tonne of rare earth oxides produced from Bayan Obo ore
(Spooner 2005) .................................................................................................. 37 Figure 18: Composition of the ore in Maoniuping’s mineral (Zhu et al. 2000) ................ 38 Figure 19: Composition of a tonne of rare earth oxides produced from Maoniuping ore
(Spooner 2005) .................................................................................................. 40 Figure 20: Beneficiation process in Bayan Obo for one tonne of original rock ................ 47 Figure 21: Beneficiation process in Maoniuping for one tonne of original rock ............... 51 Figure 22: Separation factor of rare earths in the Ln(III)-HCl-EHEHPA system (Sato
1989) .................................................................................................................. 83 Figure 23: Separation flowsheet for bastnasite (Yan et al. 2006) ...................................... 83 Figure 24: Relative proportion of light rare earth elements in Bayan Obo concentrate
(Spooner 2005) .................................................................................................. 85 Figure 25: Relative proportion of light rare earth elements in Maoniuping concentrate ... 87
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List of tables
Table 1: Categorisation of rare earth elements (Hedrick 2010) ........................................... 15 Table 2: Beneficiation process in Bayan Obo ...................................................................... 33 Table 3: Processing of mixed rare earth concentrate in Bayan Obo .................................... 35 Table 4: Separation and refining processes in Bayan Obo .................................................. 36 Table 5: Beneficiation process in Maoniuping .................................................................... 39 Table 6: Processing of rare earth concentrate in Maoniuping ............................................. 41 Table 7: Summary of the mining and comminution processes modelling ........................... 46 Table 8: Summary of the beneficiation modelling .............................................................. 46 Table 9: Summary of the stoichiometric coefficients in Bayan Obo ................................... 50 Table 10: Summary of the beneficiation modelling in Maoniuping .................................... 53 Table 11: Summary of the mining and comminution processes modelling in Maoniuping 53 Table 12: Summary of the stoichiometric coefficients in Maoniuping ............................... 56 Table 13: Required inputs for the different stages ............................................................... 58 Table 14: Emission to the air during processes in Bayan Obo ............................................ 59 Table 15: Outputs discharged .............................................................................................. 59 Table 16: Impact indicator for global warming ................................................................... 62 Table 17: Impact indicator for acidification ........................................................................ 63 Table 18: Impact indicator for eutrophication ..................................................................... 64 Table 19: Impact indicator for radioactive waste generation ............................................... 64 Table 20: Impact indicator for land use ............................................................................... 65 Table 21: Impact indicator for toxicity in wastewater ......................................................... 66 Table 22: Assumptions analysis ........................................................................................... 69 Table 23: Calculation of the chemical inputs for Bayan Obo .............................................. 88 Table 24: Calculation of the chemical outputs for Bayan Obo ............................................ 89 Table 25: Calculation of the chemical inputs for Maoniuping ............................................ 91 Table 26: Calculation of the chemical outputs for Maoniuping .......................................... 92 Table 27: CO2 emissions for mining operations ................................................................. 94 Table 28: CO2 emissions from electricity use ..................................................................... 94 Table 29: Calculation of the SO2 emissions ........................................................................ 95 Table 30: Acidification potential characterisation factors (Azapagic 2011) ....................... 95 Table 31: Acidification potential of different chemicals ..................................................... 95 Table 32: Eutrophication potential characterisation factors (Azapagic 2011) ..................... 96 Table 33: Eutrophication potential of different chemicals .................................................. 96
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Table 34: Activity in waste slag ........................................................................................... 97 Table 35: Activity in wastewater ......................................................................................... 97
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List of abbreviations
GWh gigawatt-hour (109 Wh)
kWh kilowatt-hour (103 Wh) MWh megawatt-hour (106 Wh)
Mt megatonne (106 t) LCA life cycle assessment
LCI life cycle inventory LCIA life cycle impact assessment
REE(s) rare earth element(s) REO(s) rare earth oxide(s)
t tonne tpd tonne per day
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1. Introduction 1.1. Background information
Rare earth elements (abbreviated as REE, also called rare earth metals) are a group of 17 chemical elements. They are all part of the third column of the periodic table and possess therefore similar chemical and physical features (Hedrick 2000).
They are divided into two groups: light REEs and heavy REEs. Table 1 gives information on REEs and the group to which they belong.
Table 1: Categorisation of rare earth elements (Hedrick 2010)
Chemical element Abbreviation Atomic Number Category
Scandium Sc 21 None 1
Lanthanum La 57
Light REEs
Cerium Ce 58
Praseodymium Pr 59
Neodymium Nd 60
Promethium Pm 61
Samarium Sm 62
Europium Eu 63
Gadolinium Gd 64
Yttrium Y 39
Heavy REEs
Terbium Tb 65
Dysprosium Dy 66
Holmium Ho 67
Erbium Er 68
Thulium Tm 69
Ytterbium Yb 70
Lutetium Lu 71
1 Scandium has physical properties that make it impossible to classify as either light
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REEs have become topical because they are found in many technological applications of daily life and notably many green technologies such as wind turbines, recyclable batteries, electric vehicles or compact fluorescent lamps (see 2.5).
Since these elements are common in modern life, this report considers the impacts of extracting and producing REEs.
REEs exist in several forms (rare earth chlorides, metals, carbonates, oxides, etc.). However, only rare earth oxides (and rare earth metal to a lesser extent) are of interest for industrial applications (Kingsnorth 2010).
1.2. Aim of the study The aim of this study is to assess some of the environmental impacts related to the
production of rare earth oxides (REOs).
1.3. Objectives The objectives of this study are as follows: - describe precisely the rare earth market (e.g. production, applications) - select the most representative mines - refine the scope of the study - develop a model representing the processes taking place in these mines - determine a suitable method for measuring the impacts - assess both quantitatively and qualitatively the environmental impacts
1.4. Approach In order to complete the objectives, the study was decomposed into several parts.
Firstly, an extensive literature review was carried out with the aim of collecting information on REEs, their minerals, the REE market and their applications. Based on this literature review, it was possible to define the scope of the study and single out two mines for the next step.
Secondly a further literature review was conducted to describe and understand the processes to produce REO. This second literature review was used to help build models representing these processes.
Thirdly, life cycle assessment was applied to the models developed in the previous section using data extracted from the literature.
Finally, the results were discussed.
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2. Information on rare earth elements 2.1. How rare are rare earths?
Although they are called rare earths, some of these elements are quite abundant in the Earth’s crust (Ce is the 25th most abundant elements in the Earth’s crust) and the scarcest of them (Tm and Lu) are even 200 times more abundant than gold (Hedrick 2000; Haxel 2002).
One REE, promethium, is a radioactive element with a half-life of 17.7 years for its main isotope. As a result, it does not exist naturally.
Figure 1 and Figure 2 illustrate the abundance of REEs both relatively to other elements and quantitatively.
Figure 1: Relative abundance of chemical elements in the Earth's crust (Haxel 2002)
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Figure 2: Concentrations of rare earth elements in the Earth’s crust (Tyler 2004)
2.2. Description of the main rare earth minerals According to Kanazawa and Kamitani, around 200 different types of rare earth
minerals have been reported (Kanazawa and Kamitani 2006). However, in practice, the extraction of REEs relies primarily on four different minerals:
• Bastnaesite • Monazite • Xenotime • Ion adsorption clays
This is notably due to their high contents of REO. These four minerals account for 90% of economic production of REEs (Roskill 2007).
2.2.1. Bastnaesite Bastnaesite is a fluorocarbonate with the following formula: ReFCO3
2. The grade of REES in bastnaesite is up to 75%3.
Bastnaesite is the primary source of light REO (primarily lanthanum, cerium, praseodymium and neodymium oxides) and accounts for more than 80% of the overall amount of REO in the world (Kanazawa and Kamitani 2006; Roskill 2007; Naumov 2008).
Figure 3 illustrates the abundance of the main REEs in bastnaesite.
2 From this point on, the symbol Re represents a rare earth atom. 3 The grade of a mineral is defined as the mass fraction of the REEs in the ore.
0
10
20
30
40
50
60
70
Concentration in the Earth's crust (ppm
)
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Figure 3: Contents of the main rare earth elements in bastnaesite for two mines (Kingsnorth 2010)
2.2.2. Monazite Monazite is a rare earth phosphate that contains up to 70% REEs (formula: RePO4).
With bastnaesite, it represents the most important source of light REEs. Until 1965, monazite was the main source of REEs.
It was historically produced as a by-product of sand exploitation. However, nowadays, the production of REEs from monazite has been considerably reduced because of radioactivity caused by thorium and radium impurities (ThO2 has a concentration of 6-7% in monazite produced from mineral sand operations) (Roskill 2007; Naumov 2008; Kingsnorth 2010).
Figure 4 illustrates the abundance of the main REEs in monazite.
0
10
20
30
40
50
60
Lanthanum Cerium Praseodymium Neodymium
% among rare earth elementss in
bastnaesite
USA, Moutain Pass
China, Baiyun Obo
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Figure 4: Contents of the main rare earth elements in monazite for three deposits (Kingsnorth 2010)
2.2.3. Xenotime Xenotime is a phosphate which is composed primarily of yttrium (YPO4). This
mineral contains generally around 55% of REO. Moreover, it contains a particularly high rate of heavy REEs which makes it valuable.
This mineral occurs usually in rocks that also contain uranium and thorium. Historically, it was produced as a by-product of tin mining in Malaysia, Indonesia and Thailand (Alex et al. 1998; Roskill 2007)
Figure 5 illustrates the abundance of the main REEs in xenotime.
Figure 5: Contents of the main rare earth elements in xenotime (Kingsnorth 2010)
0
5
10
15
20
25
30
35
40
45
50
Lanthanum Cerium Praseodymium Neodymium Samarium
% among rare earth elements in monazite
Mt Weld, Australia
India
Guandong, China
0
10
20
30
40
50
60
70
% among rare earths in xenotime
Lahat Perak, Malaysia
Guangdong, China
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2.2.4. Ion Adsorption Clays These minerals are peculiar to the Jiangxi province of southern China. They are the
result of the weathering of two minerals: xenotime and apatite. Although they have a very small content of REEs (0.05% to 0.2%) (Kanazawa and
Kamitani 2006), these clays are particularly interesting because they contain relatively high contents of heavy REEs compared to other rare earth minerals. (Roskill 2007; Kingsnorth 2010).
Another advantage of these minerals is that they can be easily mined and processed4. Besides, they contain very few radioactive elements (Kanazawa and Kamitani 2006).
However, as illustrated in the following figure, even though they come from the same geographical area, their contents of REEs vary significantly.
Figure 6 illustrates the abundance of the main REEs in ionic clays.
Figure 6: Contents of the main rare earth elements in Chinese ionic clays (Kingsnorth 2010)
4 The processing of ion adsorption clays does not require any milling and REOs are
produced by a simple method (Kanazawa and Kamitani 2006).
0
10
20
30
40
50
60
70
% among rare earths in ionic clays Xunwu, Jiangxi, China
Lognan, Jiangxi, China
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2.3. Description of the rare earth reserves In 2011, it was estimated that the total recoverable resource amounts approximately
140 Mt (USGS 2011). The economically viable reserves of REEs are summarised in Figure 7.
Figure 7: Breakdown of the economically viable rare earth resource (USGS 2011)
2.4. Historical production of rare earth oxide REOs were first produced in the 1880s with the mining of monazite in Sweden and
Norway. Their first industrial application was in the Welsbach incandescent lamp mantle in 1884. The production of REOs in the USA began in 1903 with the mining of monazite in South Carolina.
Over the first half of the last century, the production remained quite low. It then increased due to the discovery of new applications such as catalysts to crack crude oil into petroleum.
Until the 1960s, the production of REEs from placer monazite took mainly place in the southeast of the USA. It was then abandoned due to its high content of thorium (Hedrick 2000).
Then, the production moved to a major deposit located at Mountain Pass, California. This mine was in operation from 1965 until the mid 1990s and over this period only bastnaesite was processed in Mountain Pass. At Mountain Pass, the reserves of REEs are still over 20 million tonnes with an average grade of rare earth minerals of 8.9% (Castor and Hedrick 2006).
Through the 1990s, China’s exports grew importantly causing American production to be undercut. Most of the Chinese production comes from Bayan Obo deposit (Inner Mongolia, China) which represents the largest known REE resource in the world. In this
Australia 1.6 Mt 1%
Brazil 48,000 t 0%
China 55 Mt 48%
Commonwealth of Independent
States 19 Mt 17%
India 3.1 Mt 3%
Malaysia 30,000 t 0%
United States 13 Mt 12%
Other countries 22 Mt 19%
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mine, both bastnaesite and monazite are processed (Castor and Hedrick 2006; Hurst 2010).
Figure 8 illustrates the growth in the production of REOs over the 20th century.
Figure 8: Global production of rare earth oxide (USGS 2010)
Figure 9 illustrates the great periods of REE exploitation from 1950.
Figure 9: World production of rare earth oxides from 1950 to 2000 (Haxel 2002)
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Production (tonne)
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2.5. Description of the main applications of the rare earth elements This section is entirely based on the two following works:
- Roskill 2007 - Schüler et al. 2011
Figure 10 describes the world demand of REEs in 2006.
Figure 10: Global rare earth consumption in 2006 (Roskill 2007)
2.5.1. Magnets There are two main kinds of rare earth magnets: neodymium-iron-boron magnets
and samarium-cobalt magnets. Neodymium-iron-boron (Nd2Fe14B) magnets are the strongest available magnets. In addition to neodymium, they comprise other REEs: praseodymium (30% the amount of neodymium) and dysprosium (3% the amount of neodymium).
This market is growing very quickly since its average annual growth was 25% between 1986 and 2006. This growth is driven by three main applications: electric motors for hybrid and electric vehicles, generators in wind turbines and computer hard disks.
Moreover, several other applications requires neodymium magnets such as: - loudspeakers, earphones and microphones - MRIs scanners - electric bicycles
Catalyst 21%
Glass, Polishing, Ceramics 25%
Metal Alloys 17%
Magnets 20%
Phosphors 9%
Other 8%
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2.5.2. Catalyst REEs are used as catalysts in the automobile industry, petroleum refinery and
chemical processing. REEs are use for the following applications: - automotive catalysts and diesel additives (cerium) - fluid cracking catalyst for the petroleum industry (cerium, lanthanum) In the automobile industry, cerium is used to:
- reduce nitrogen oxide into nitrogen and water - oxide CO to CO2
2.5.3. Glass, polishing, ceramics
2.5.3.1. Glass polishing Thanks to its specific properties of physical and chemical abrasion cerium is
massively used to produce high-quality glass for the following markets: - mirrors - televisions and monitors - panel displays - glass platters in hard disks This sector represents 13% of the global REE consumption. Its growth rate follows
that of plasma displays, LCDs and computer monitors.
2.5.3.2. Glass additives REEs are used as glass additives for the following applications:
- colouring of glass (cerium for yellow and brown, neodymium for red, erbium for pink)
- decolouring of glass (cerium) - UV-resistant glass (e.g. for glass bottles, sunglasses, solar cells) (cerium) - optical lenses, filters or coating (lanthanum, gadolinium, praseodymium) This sector represents 12% of the global REE consumption. The growth of this
market is mainly driven by the growth in optical applications (e.g. digital cameras, security cameras, mobile phones).
2.5.3.3. Ceramics REEs are used in ceramics for the following applications:
- ceramic capacitors and semiconductors (lanthanum, cerium, praseodymium, neodymium)
- superconductors (yttrium) - dental ceramics (cerium) - refractory materials (cerium, yttrium) - laser (yttrium) This sector represents 5% of the global REE consumption.
The growth of electronics results in an increase of the demand of REEs for ceramic uses.
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2.5.4. Metal alloys REEs are used in metal alloys for different applications. They bring new properties
to the metal they are mixed with. They can be used in: - pyrophoric alloys (cerium, lanthanum) - high-performance alloys to improve their performances (lanthanum, cerium,
yttrium) - solid state storage of hydrogen in metallic matrixes - scandium-aluminium alloys used in military aviation - lanthanum-nickel alloys in Ni-MH batteries
2.5.5. Phosphors and luminescence REEs are inserted into crystals of various natures in order to give them
luminescence properties. Depending on the wavelength expected, it is possible to choose between cerium, samarium, europium, gadolinium, terbium, dysprosium, erbium, thulium or lutetium.
As a result, these REEs are used in mainly two fields: energy saving lighting and display technologies. They are found in the following applications
- compact fluorescent lamps (energy saving lamps) - fluorescent tubes - LEDs and OLEDs - electroluminescent foils - plasma displays - LCDs
The growth in this sector is driven by: - the general growth in the lighting demand (7% per year from 2004 to 2011) - the replacement of incandescent bulbs in many countries by among other
compact fluorescent lamps and halogen lamps - the growth of the LED market - the replacement of cathode-ray tubes by plasma displays and LCDs
2.5.6. Other Many other applications require REEs: - agricultural use of REEs in phosphate fertiliser (cerium, lanthanum) - Ni-MH batteries (lanthanum, cerium, neodymium, praseodymium) - solid oxide fuel cell electrolytes (yttrium) - neutron absorbers in nuclear reactors (europium, gadolinium) - waste water treatment (cerium)
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3. Production of rare earth elements 3.1. World production of rare earth elements
Since the end of the 1990s, China has been the main producer of REEs in the world. In 2010, its official production amounted to 130,000 tonnes of REOs while the second and third largest producers (respectively India and Brazil) produced, respectively, 2,700 tonnes and 550 tonnes of REOs (USGS 2011).
As a result, the main REE mines and processing plants are to be found in China.
Figure 11 summarises the global production of REEs:
Figure 11: Global production of rare earth oxides in 2010 (USGS 2011)
3.2. Chinese production of rare earths The Chinese production of REEs takes place in three different areas: Inner
Mongolia, Sichuan province, and seven southern provinces.
3.2.1. Inner Mongolia Inner Mongolia houses the largest deposit of REEs in the world, namely Bayan Obo
deposit. It accounts for 80% of the Chinese reserve of REEs (Crédit Suisse 2011; Schüler et al. 2011).
However, it appears that the precise amount of the REO resources contained in this deposit varies according to the measurement method: the reserve ranges from 28 million tonnes of REO (USGS classification) to 44 million tonnes (Chinese classification) (Crédit Suisse 2011). The definitions of the different classifications are given in Appendix 1.
In Bayan Obo, REOs are produced as a by-product of iron ore whose reserve amounts to 1.46 billion tonnes (Spooner 2005; Roskill 2007).
The REOs mined in Bayan Obo are composed primarily of light REEs that represent 97% of the whole rare earth minerals. The rare earth minerals are concentrated in two different minerals: bastnaesite and monazite (there is about 2.5 as much bastnaesite as monazite) (Huang et al. 2005; Crédit Suisse 2011).
China 130,000 t 97%
India 2,700 t 2%
Brazil 550 t 1%
Malaysia 350 t 0%
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Figure 12 illustrates the composition of rare earth mineral in Bayan Obo’s ore.
Figure 12: Breakdown of rare earth oxide-content at Bayan Obo (Crédit Suisse 2011)
This deposit is owned by one state-owned company called Baotou Steel Rare Earth Group Hi-Tech Co, Ltd (Baotou Rare Earth). It is a fully integrated company (from mining operations to the production of REOs).
Besides, the Chinese Ministry of Land and Resources has decided to restructure the industry of REE production in Inner Mongolia. As a result, Baotou Rare Earth will soon become the only company extracting and producing REEs from the Bayan Obo deposit (Crédit Suisse 2011; Global Times 2011).
In 2010, Baotou Rare Earth produced 62,400 t of REO (Crédit Suisse 2011).
3.2.2. Sichuan province The second largest deposit of bastnaesite mineral in China is located in the county
of Mianning (Sichuan Province). This deposit is called Maoniuping after the name of a surrounding city.
It is estimated to contain 3% of Chinese reserves of REO. This represents 1.56 Mt of REOs according to the Chinese classification (Crédit Suisse 2011; Schüler et al. 2011).
In this deposit, rare earth minerals are contained almost exclusively in bastnaesite (Tse 2011).
Since Bayan Obo’s ore is composed of approximately 70% bastnaesite, the content of REEs in the Maoniuping’s ore is quite similar to Bayan Obo’s.
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Figure 13 illustrates the composition in REEs of the bastnaesite in Maoniuping:
Figure 13: Bastnaesite content of rare earth elements at Maoniuping (Spooner 2005)
The REO production in Maoniuping accounts for 24% of China’s total production, i.e., approximately 31,200 tonnes, in 2010 (Crédit Suisse 2011; Tse 2011; Wong and Li 2011).
As in Bayan Obo, the mining operations are controlled by a single company named Jiangxi Copper (JXC Group) (Crédit Suisse 2011).
3.2.3. Southern Provinces The seven southern provinces that contribute to the production of Chinese REEs
are: Jiangxi, Guangdong, Fujian, Guangxi, Hunan, Yunnan and Zhejiang. They represent the majority of China’s production of heavy REEs (Crédit Suisse 2011).
In these provinces, REEs are found in ionic clays which are composed at 90% of heavy REEs. Figure 14 illustrates the content of ionic clay.
Figure 14: Ionic clay content of rare earth elements at Longnan (Crédit Suisse 2011)
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The production of REEs from Chinese ionic clays was approximately 36,000 tonnes in 2010 representing 28% of the China’s REE production (Crédit Suisse 2011; Tse 2011).
3.2.4. Summary of Chinese rare earth production Figure 15 was drawn to summarise the information in the previous sections. It
shows the distribution of the REE production between the different Chinese regions.
Figure 15: Distribution of the Chinese production of rare earths in 2010
Light REEs account for 72% of Chinese REE production. Since Chinese production amounted to 97% of the global production, light REEs represented at least 70% of the REEs produced globally in 2010.
As a result, since the production of light REEs from bastnaesite takes place only in Bayan Obo and in Sichuan province, these two regions will be subsequently analysed.
3.3. Prospective other productions In response to the introduction of quotas by the Chinese government and the
increase in REE prices, western companies have launched important projects that aim at supplementing the Chinese production. Among these projects, two are particularly significant because:
• they are both very large (production > 20,000 tonnes of REOs per year) • they are in the final stages of development and, are planned to open in the
next two years
3.3.1. Mount Weld, Australia Mount Weld is located in southwestern Australia. This deposit is own by Lynas
Corporation Ltd which is an Australian REE mining company. Mount Weld is estimated to include 1.4 Mt of REO contained mainly in monazite (i.e. composed primarily of light REEs) (Crédit Suisse 2011).
Bayan Obo 48%
Maoniuping 24%
Southern Provinces 28%
30
purification of REEs) will be carried out in Malaysia by a subsidiary of Lynas (Lynas Malaysia).
The production will start at 11,000 t of REO p.a. and increase up to 22,000 t of REO p.a (British Geological Survey 2011; Schüler et al. 2011).
3.3.2. Mountain Pass, USA Mountain Pass is the deposit from which the REEs were historically produced for
several years. It was undercut by the Chinese production in the 1990s and was not operating since then. Mountain Pass contains 4.3 Mt of REO in bastnaesite minerals.
It is now own by a company named Molycorp which plans to reopen the mines in 2012. Like Lynas in Australia, Molycorp will produce 20,000 t p.a. when operating at full capacity. Thanks to the existing facilities, the mining and the processing will be carried out on the same site (Hurst 2010; British Geological Survey 2011; Crédit Suisse 2011; Schüler et al. 2011).
31
4. Scope refining To limit the scope of this project, it was decided to focus only on the production of
light REEs since they account for the majority of world REE production. Since Chinese production represented 97% of 2010 global production, it was
decided that concentrating on this production would give an accurate perspective of the present environmental impacts of producing light REOs.
Finally, as explained in section 3.2.4, China’s light REEs come only from two deposits: Bayan Obo and Maoniuping. As a result, the scope of the study was defined to the assessment of environmental impacts of producing light REO in both Bayan Obo and Maoniuping deposits.
5. Bayan Obo deposit 5.1. Description of the deposit
The Bayan Obo deposit (Inner Mongolia, China) is located 80 km south of the Mongolian border.
The principal ore minerals are bastnaesite and monazite (rare earth minerals), pyrochlore (Nb), magnetite and hematite (Fe) (Campbell and Henderson 1997).
In Bayan Obo, REEs were produced from more than twenty sites since the beginning of the mining in 1957. The two largest deposits are the Main and East ore bodies with a REE grade of 5.14% and 5.18% respectively5. The Bayan Obo ore is hosted in dolomite (Castor and Hedrick 2006).
The mining operations are carried out using electric shovels and rail haulage at a rate of 15,000 tonnes of rock per day from the two large open pits (Castor and Hedrick 2006).
5.2. Composition of the original ore Baotou’s rock is complex and its composition varies significantly from one place to
another. Therefore it is not possible to give the composition of this ore in general. However, it is possible to look at some specific elements (Drew et al. 1990; Castor and Hedrick 2006):
- iron: average grade of 35% - REOs: average grade of 6% - niobium: average grade of 0.13% - fluorite (CaF2): average grade of 9% - barium oxide (BaO): average grade of 2.4%
5.3. Description of the beneficiation process The beneficiation process is described in Table 2. For each stage of this process, a
description is given as well as the sources of the information.
5 These grades are surprisingly lower than the average rare earth grade (6%), this
may be because in Bayan Obo, REO are produced as a by-product of iron.
32
Tab
le 2
: Ben
efic
iatio
n pr
oces
s in
Bay
an O
bo
Stage
Purpose
Process d
escriptio
n Re
ference
Crushing
• C
rush
ing
of 9
0% o
f the
re
sulti
ng p
artic
les t
o <
74 µ
m
• Th
e or
e is
cru
shed
and
gro
und
in a
mill
o S
chül
er e
t al.
2011
o
Che
ng e
t al.
2007
o
Guy
et a
l. 20
00
o R
en e
t al.
1997
o
Dre
w e
t al.
1990
Bulk
flotatio
n6
• Se
para
tion
of ra
re e
arth
min
eral
s an
d th
e ga
ngue
from
the
othe
r va
luab
le m
iner
als
• R
ecov
ery
of si
licat
es a
nd ir
on m
iner
als (
mag
netit
e Fe
3O4 a
nd h
emat
ite F
e 2O
3) fr
om th
e bo
ttom
of t
he
flota
tion
cell
for i
on b
enef
icia
tion
and
niob
ium
reco
very
•
pH re
gula
tion
by N
a 2C
O3
• D
epre
ssan
t act
ion
by N
a 2Si
O3
• C
olle
ctio
n of
rare
ear
th m
iner
als a
nd g
angu
e by
so
dium
salt
of o
xidi
sed
petro
leum
(par
affin
soap
)
o G
upta
and
Kris
hnam
urth
y 20
05
Thickening
• R
emov
al o
f the
surp
lus p
araf
fin
soap
and
des
limin
g at
5 µ
m
- o
Hou
t, et
al.
1991
o
Gup
ta a
nd K
rishn
amur
thy
2005
Selective
rare earth
flotatio
n6
• Se
para
tion
of ra
re e
arth
min
eral
s fr
om c
alci
te (C
aCO
3), f
luor
ite
(CaF
2) a
nd b
arite
(BaS
O4)
m
iner
als
• pH
regu
latio
n by
Na 2
CO
3 •
Dep
ress
ant a
ctio
n by
Na 2
SiF 6
and
Na 2
SiO
3 •
Col
lect
ion
of ra
re e
arth
min
eral
s by
hydr
oxam
ic a
cid
(par
affin
soap
)
o G
upta
and
Kris
hnam
urth
y 20
05
o R
en, e
t al.
2003
o
Fer
ron,
et a
l. 19
91
Cleaning
• C
once
ntra
tion
of ra
re e
arth
m
iner
als
• Th
icke
ning
, filt
erin
g an
d dr
ying
of t
he re
sulti
ng sl
urry
o
Gup
ta a
nd K
rishn
amur
thy
2005
o
Brit
ish
Geo
logi
cal S
urve
y 20
10
o W
ang,
et a
l. 20
10
6 The
flot
atio
n pr
oces
s is d
escr
ibed
furth
er in
App
endi
x 2
33
5.4. Composition of the mixed rare earth concentrate Figure 16 illustrates the composition of the mixed rare earth concentrate obtained
after the beneficiation process.
Figure 16: Composition by weight of the mixed bastnaesite-monazite concentrate (Wang et al. 2002)
5.5. Processing of the mixed rare earth concentrate
5.5.1. Hydrometallurgy: acidic method An acidic method is used to process 90% of the product of Bayan Obo. It consists in
the roasting and leaching of the concentrate with sulphuric acid (Schüler et al. 2011).
Table 3 summarises the hydrometallurgy processes at Bayan Obo.
5.5.1. Separation and refining Table 4 describes the processes of separation and refining leading to the production
of REOs.
5.6. Obtaining of rare earth oxides A tonne of REOs produced in Bayan Obo is composed as described in Figure 17.
REO 60.94%
ThO2 0.18%
Fe2O3 4.82%
F 6.96%
P2O5 8.22%
SiO2 1.28%
CaO 5.11%
CO2 11.91%
MnO 0.48%
34
Tab
le 3
: Pro
cess
ing
of m
ixed
rar
e ea
rth
conc
entr
ate
in B
ayan
Obo
Stage
Purpose
Process d
escriptio
n Re
ference
Sulpha
tising
roastin
g
• R
emov
al o
f CO
2, ph
osph
ate
and
fluor
ide
• C
onve
rsio
n of
rare
ea
rth m
iner
als i
nto
rare
ea
rth su
lpha
tes
• M
ixin
g of
rare
ear
th c
once
ntra
te a
nd 9
8% su
lphu
ric
acid
(H2S
O4)
in a
rota
ry k
iln a
t 500
°C fo
r 4 h
ours
. •
Rea
ctio
ns fo
r bas
tnae
site
: R
eFC
O3
ReF
O +
CO
2 2
ReF
O +
3 H
2SO
4R
e 2(S
O4)
3 +2
HF
+2 H
2O
• R
eact
ions
for m
onaz
ite:
2 R
ePO
4 + 3
H2S
O4
Re 2
(SO
4)3 +
2 H
3PO
4
o S
chül
er, e
t al.
2011
o
Hua
ng, e
t al.
2005
o
Gup
ta a
nd K
rishn
amur
thy
2005
o
Ngu
yen,
et a
l. 20
02
o W
ang,
et a
l. 20
10
Removal of
impu
rities
• R
emov
al o
f im
purit
ies
• D
ecan
tatio
n of
the
mix
ture
to re
mov
e th
e so
lid
• Fi
ltrat
ion
and
leac
hing
with
wat
er
• O
btai
ning
of a
pur
e ra
re e
arth
sulp
hate
solu
tion
o T
odor
ovsk
y, e
t al.
1993
o
Ros
kill
2007
o
Sch
üler
, et a
l. 20
11
o K
ul, e
t al.
2008
o
Ngu
yen,
et a
l. 20
02
o G
upta
and
Kris
hnam
urth
y 20
05
Carbon
ate
precipita
tion
• Se
lect
ive
prec
ipita
tion
and
reco
very
of t
he ra
re
earth
sulp
hate
s int
o ca
rbon
ate
prec
ipita
te
• R
insi
ng o
f rar
e ea
rth su
lpha
tes w
ith b
icar
bona
tes
NH
4HC
O3 i
n an
aci
d so
lutio
n:
Re 2
(SO
4)3+
6 N
H4H
CO
3 R
e 2(C
O3)
3 + 3
(NH
4)2S
O4
+ 3
CO
2 + 3
H2O
o N
guye
n, e
t al.
2002
o
Sch
üler
, et a
l. 20
11
o K
ul, e
t al.
2008
o
Abr
eu a
nd M
orai
s 201
0
Acid
leaching
• Tr
ansf
orm
atio
n of
rare
ea
rth c
arbo
nate
pr
ecip
itate
into
rare
ear
th
chlo
rides
• R
insi
ng w
ith h
ydro
chlo
ric a
cid
(HC
l) •
Tran
sfor
mat
ion
to ra
re e
arth
chl
orid
es:
Re 2
(CO
3)3 +
6 H
Cl
2 R
eCl 3
+ 3
H2C
O3
o S
chül
er, e
t al.
2011
o
Hua
ng, e
t al.
2005
35
Tab
le 4
: Sep
arat
ion
and
refin
ing
proc
esse
s in
Bay
an O
bo
Step
Pu
rpose
Process d
escriptio
n Re
ference
Solven
t Extractio
n7
• Se
para
tion
of R
EEs
from
eac
h ot
her
• Th
e liq
uid-
liqui
d ex
tract
ion
is c
arrie
d ou
t usi
ng 2
-et
hylh
exyl
phos
phon
ic a
cid
mon
o-2-
ethy
lhex
yl e
ster
(als
o na
med
HEH
(EH
P), E
HEH
PA o
r P 5
07) i
n a
HC
l med
ium
. •
Com
plex
atio
n re
actio
n:
Re3+
+ 3
(HX
) 2
ReX
6H3 +
3 H
+ H
X re
ferr
ing
to P
507
o S
chül
er, e
t al.
2011
o
Fon
tana
and
Pie
trelli
200
9 o
Sat
o 19
89
Precipita
tion
• Se
para
tion
of ra
re
earth
com
plex
es fr
om
the
solv
ent
• Th
e se
para
ted
rare
ear
th so
lutio
n is
pre
cipi
tate
d by
am
mon
ium
bic
arbo
nate
(NH
4)H
CO
3 or o
xalic
aci
d C
2H2O
4 •
Che
mic
al re
actio
ns:
2 R
eCl 3
+ 3
C2H
2O4
Re 2
(C2O
4)3 +
6 H
Cl
o Q
iu, e
t al.
2010
o
Sch
üler
, et a
l. 20
11
Prod
uctio
n of
REO
• O
xida
tion
of th
e pr
ecip
itate
• Th
e pr
ecip
itate
s are
hea
ted
in o
rder
to o
xidi
se th
em in
to
REO
•
Oxi
datio
n re
actio
n:
Re 2
(C2O
4)3 +
3/2
O2
Re 2
O3 +
6 C
O2
8 o
Sch
üler
, et a
l. 20
11
7 The
solv
ent e
xtra
ctio
n pr
oces
s is d
escr
ibed
furth
er in
App
endi
x 3
8 The
oxi
datio
n re
actio
ns d
epen
d on
the
rare
ear
th c
once
rned
: -
for L
a, N
d an
d Sm
: Re 2
(C2O
4)3 +
3/2
O2
Re 2
O3 +
6 C
O2
- fo
r Ce:
Ce 2
(C2O
4)3 +
2 O
2 2
CeO
2 + 6
CO
2
- fo
r Pr:
3 Pr
2C2O
4 + 1
1/2
O2
Pr 6
O11
+ 6
CO
2
36
Figure 17: Composition of a tonne of rare earth oxides produced from Bayan Obo ore (Spooner 2005)
6. Maoniuping deposit 6.1. Description of the deposit
Maoniuping deposit is located at 22 km southwest of the Mianning county town (Sichuan Province, China). The soil is composed mainly of granite (K-feldspar granite and alkali feldspar granite).
Among rare earth minerals, bastnaesite is the most important in this deposit (Wu et al. 1997). The average grade of REEs in this deposit is about 4%. This deposit contains also manganese (Mn) (2-10%), lead (Pb) and aluminium (Al) among other minerals (Zhu et al. 2000).
Maoniuping is the second largest deposit of light REEs in China after Bayan Obo (Xu et al. 2003).
CeO2 512.8 kg
La2O3 235.4 kg
Pr6O11 51.2 kg
Nd2O3 184.2 kg
Sm2O3 16.4 kg
37
6.2. Composition of the original ore Figure 18 illustrates the composition of the ore in Maoniuping deposit.
Figure 18: Composition of the ore in Maoniuping’s mineral (Zhu et al. 2000)
6.3. Description of the beneficiation process The process of beneficiation in Maoniuping is described in Table 5.
Al2O3 16.3
BaO 1.89
CaO 1.3
CO2 3.77
F 1.29 Fe2O3
11
H2O 6.22
K2O 3.78
MgO 3.03
MnO 3.89
Na2O 0.4
P2O5 0.64
Pb 1.97
Rare earths 4.34
SiO2 36
SO3 3.9
TiO2 0.28
38
Tab
le 5
: Ben
efic
iatio
n pr
oces
s in
Mao
niup
ing
Step
Pu
rpose
Process d
escriptio
n Re
ference
Crushing
• R
educ
tion
of th
e si
ze o
f the
par
ticle
s so
as to
incr
ease
the
surf
ace
of re
actio
n
• Th
e or
e is
cru
shed
and
gro
und
in a
mill
o
Sch
üler
, et a
l. 20
11
o Z
hu, e
t al.
2000
Gravity
sepa
ratio
n •
Sepa
ratio
n an
d re
cove
ry o
f cer
tain
va
luab
le m
iner
als
- o
Sch
üler
, et a
l. 20
11
o Y
ang
and
Woo
lley
2006
Selective rare
earth flo
tatio
n •
Sepa
ratio
n of
rare
ea
rth m
iner
als f
rom
th
e ga
ngue
- o
Sch
üler
, et a
l. 20
11
Cleaning
• R
ecov
ery
of ra
re
earth
con
cent
rate
• Th
e re
sulti
ng sl
urry
is th
icke
ned,
filte
red
and
drie
d •
The
over
all r
ecov
ery
of R
EEs l
ies b
etw
een
80 a
nd
85%
and
the
conc
entra
te c
onta
ins u
p to
70%
REE
s
o G
upta
and
Kris
hnam
urth
y 20
05
o B
ritis
h G
eolo
gica
l Sur
vey
2010
o
Wan
g, e
t al.
2010
o
Li a
nd Z
eng
2003
39
6.4. Processing of the mixed rare earth concentrate
6.4.1. Hydrometallurgy: acidic method Table 6 summarises the hydrometallurgy processes at Maoniuping.
6.4.2. Separation and refining operations The separation and refining operations in Maoniuping are the same as those in
Bayan Obo (see 5.5.1) (Schüler et al. 2011).
6.5. Obtaining of rare earth oxides A tonne of REOs produced in Maoniuping is composed as described in Figure 19.
Figure 19: Composition of a tonne of rare earth oxides produced from Maoniuping ore (Spooner 2005)
CeO2 510.1 kg
La2O3 296.1 kg
Pr6O11 46.7 kg
Nd2O3 131.8 kg
Sm2O3 15.2 kg
40
Tab
le 6
: Pro
cess
ing
of r
are
eart
h co
ncen
trat
e in
Mao
niup
ing
Step
Pu
rpose
Process d
escriptio
n Re
ference
Sulpha
tising
roastin
g
• R
emov
al o
f CO
2 an
d flu
orid
e •
Con
vers
ion
of ra
re
earth
min
eral
s int
o ra
re e
arth
sulp
hate
s
• Th
e co
ncen
trate
is m
ixed
with
98%
sulp
huric
aci
d (H
2SO
4) in
a ro
tary
kiln
at 5
00°C
for 4
hou
rs
• R
eact
ions
: R
eFC
O3
ReF
O +
CO
2 R
eFO
+ H
2SO
4R
e 2(S
O4)
3 +2
HF
+2 H
2O
o S
chül
er, e
t al.
2011
o
Hua
ng, e
t al.
2005
o
Ngu
yen,
et a
l. 20
02
o W
ang,
et a
l. 20
10
o G
upta
and
Kris
hnam
urth
y 20
05
Removal of
impu
rities
• R
emov
al o
f im
purit
ies
• Th
e m
ixtu
re is
dec
ante
d to
rem
ove
the
solid
•
The
solu
tion
is fi
ltere
d an
d le
ache
d w
ith w
ater
•
A p
ure
rare
ear
th su
lpha
te so
lutio
n is
obt
aine
d (th
is
solu
tion
cont
ains
aro
und
40g/
L of
rare
ear
th
sulp
hate
s)
o T
odor
ovsk
y, e
t al.
1993
o
Ros
kill
2007
o
Sch
üler
, et a
l. 20
11
o K
ul, e
t al.
2008
o
Ngu
yen,
et a
l. 20
02
o G
upta
and
Kris
hnam
urth
y 20
05
Sulpha
te
precipita
tion
• Se
lect
ive
prec
ipita
tion
and
reco
very
of t
he ra
re
earth
sulp
hate
s int
o su
lpha
te p
reci
pita
te
• R
EEs a
re le
ache
d w
ith so
dium
sulp
hate
s (at
pH
1.5
) •
Prec
ipita
tion
reac
tion:
R
e3+ +
Na+ +
2 S
O42-
N
aRe(
SO4)
2
o N
guye
n, e
t al.
2002
o
Sch
üler
, et a
l. 20
11
o K
ul, e
t al.
2008
o
Abr
eu a
nd M
orai
s 201
0
Acid Leaching
• Tr
ansf
orm
atio
n of
ra
re e
arth
car
bona
te
prec
ipita
te in
to ra
re
earth
chl
orid
es
• R
are
earth
car
bona
tes a
re le
ache
d w
ith
hydr
ochl
oric
aci
d (H
Cl)
• Th
e ca
rbon
ates
are
tran
sfor
med
to ra
re e
arth
ch
lorid
es
• C
hlor
inat
ion
reac
tion
NaR
e(SO
4)2 +
HC
l R
eCl 3
+ N
a+ + 3
H+ +
2 S
O42-
o S
chül
er, e
t al.
2011
o
Hua
ng, e
t al.
2005
41
Life Cycle assessment (LCA)
7. Life cycle assessment methodology A cradle-to-gate methodology rather than full cradle-to-grave life cycle assessment
(LCA) was used since it allowed restriction of the scope of this study. The cradle to gate approach defines the boundaries as “from raw material to factory gate”. In this case, it was indeed from raw material to REO output, without consideration of the fate of the numerous products made with REEs.
In conformity with LCA methodology, this LCA is composed of the following sections:
- Goal and Scope definition - Life Cycle Inventory - Life Cycle Impact Assessment - Life Cycle Interpretation
Firstly, the goal and scope section exposes the reasons why the LCA is carried out as well as defines the boundaries of the LCA.
Secondly, the life cycle inventory aims at determining the inputs and outputs of material or energy that are required by the different processes. This phase is based on a meticulous modelling of these processes.
Thirdly, the life cycle impact assessment classifies and characterises the results of the life cycle inventory to come up with a quantitative estimate of environmental impacts.
Finally, the life cycle interpretation draws conclusion on the LCA based on the three first steps. It helps analysing the results as well as the gaps in the study.
8. Goal definition and scope 8.1. Goal of the life cycle assessment
The goal of the LCA is to establish baseline information for the processes taking place in the two biggest deposits of light REEs and resulting in the production of REO. This baseline consists of energy and chemical requirements, waste generation and pollution.
This study should be looked at as starting points for people aiming at: - carrying out the full life cycle assessment of lanthanum, cerium,
praseodymium or neodymium products - studying the environmental impacts of a product containing these REEs - studying the two deposits that are scrutinised here - carrying out a similar study for a different mineral - gaining knowledge about REEs The intended audience is whoever is interested in the requirements and impacts of
producing REOs.
42
8.2. Level of specificity Although this study focuses precisely on two mines, it uses specific data when
available and average data otherwise. Due to the lack of available information, a high level of accuracy is not to be expected. The results should rather be considered as giving realistic orders of magnitude of the energy and chemical consumption, waste generation and pollution emissions.
8.3. Display of results Throughout the LCA, the results are expressed “per tonne of REOs” (except where
otherwise stated). This means that the amounts are estimated for a final production of one tonne of REO.
8.4. Scope of the life cycle assessment The study is not a full life cycle assessment, it is composed of two stages: raw
material acquisition and materials manufacture. It focuses on the mining, beneficiation and refining operations to obtain REOs. These boundaries are in accordance with the scope defined in section 4.
Besides, the study takes into consideration only primary activities that contribute to extracting and transforming the mineral. It does not considerate activities that contribute to making the primary activities possible.
8.5. Guideline to life cycle assessment methodology In order to carry out this study according to international standards, a main
guideline was followed as meticulously as possible:
- Life cycle assessment: principles and practice by the U.S. Environmental Protection Agency (Curran 2006)
9. Process Modelling: The processes described in the previous sections were modelled in order to calculate
the amount of inputs and outputs required by the production of REOs.
In order to simplify the understanding, the processes of Bayan Obo were firstly modelled and then the processes of Maoniuping were modelled.
9.1. Bayan Obo deposit The calculations are explained in Appendix 4.
9.1.1. Mining On the one hand, there are two different kinds of inputs: energy to fuel the
machinery and explosives. On the other hand, there are two different types of outputs: valuable minerals and waste rocks.
Before modelling the mining operation, consideration is given to the mining rate. The results and assumptions are summarised in Table 7.
43
9.1.1.1. Mining rate The mining rate is the rate of rock extraction, it is expressed in tonnes per day (tpd).
Assuming that mining rate in the Bayan Obo deposit increased proportionally to the REO production, the mining rate of 15,000 tonnes per day (tpd) in 2006 (Castor and Hedrick 2006) can be used to estimate the mining rate in 2010.
As a result, it is estimated that the Bayan Obo mining rate was about 16,200 tpd in 2010.
9.1.1.2. Energy requirement
Due to a lack of public data, it was not possible to estimate the energy consumption of the mining operations directly.
However, the order of magnitude of the energy consumption is provided in the Mining Engineering Handbook, which estimates that surface mining operations require 5 to 10 kWh per tonne of rock handled (Nilsson 1992).
Thus, considering 7.5 kWh per tonne of rock handled (middle figure between 5 and 10 kWh), it is estimated that the annual quantity of energy consumed in the mining operations amounts to 44.3 GWh.
Assuming that the mining operations are carried out with machinery (trucks, shovel…), this amount of energy is provided with fuel.
9.1.1.3. Explosives input In the same document, Nilsson estimates that surface mining operations requires
0.14 to 0.23 kg of ammonium nitrate/fuel oil (ANFO)9 per tonne of blasted rock (Nilsson 1992).
Assuming that the mining operations requires 0.2 kg of ANFO per tonne of blasted rock, the annual quantity of ANFO for the mining operations is about 1,180 tonnes.
9.1.2. Comminution This stage of the operations does not require any input but energy to grind and crush
and the rock to be ground and crushed. The only output is the crushed rock. The energy requirements are estimated based on a similar rare earth mining project.
This project takes place in Thor Lake (Northwest territories of Canada), it is supposed to start the production not before 2014. The company Avalon Rare Metals is carrying out this project (Eriksson and Olsson 2011).
Avalon Rare Metals has estimated that 6 MW are necessary in average for the 2,000 tpd milling operations (comminution, beneficiation and hydrometallurgy) (Cox et al. 2011).
As a result, it is estimated that the comminution, beneficiation and hydrometallurgy operations in Bayan Obo require 426 GWh per year.
The results and assumptions of the mining and comminution sections are summarised in Table 7.
9 ANFO is an explosive composed of ammonium nitrates (NH4NO3) and oil.
44
9.1.3. Beneficiation During the production of concentrated bastnaesite, several different chemicals are
used to obtain the right froth flotation. Unfortunately, it was not possible to identify the different chemicals nor to determine how long these solutions can be used before being discarded.
However, two main other inputs have been identified for this stage: energy for the chemical reactions and mined minerals. The outputs are of three different types:
- rare earth concentrate - other valuable minerals (such as those containing Fe or Nb) - tailings
Assuming a full recovery and high selectivity of the magnetic minerals (Fe and Nb) thanks to the magnetic separation roll, the beneficiation process is described in Figure 20.
45
Tab
le 7
: Sum
mar
y of
the
min
ing
and
com
min
utio
n pr
oces
ses m
odel
ling
Stage
Type
Qua
ntity
Assumptions
Mining
Min
ing
rate
16
,200
tpd
o p
ropo
rtion
ality
to R
EO o
utpu
t o
Bay
an O
bo re
pres
ente
d 48
% o
f th
e pr
oduc
tion
in 2
006
(as i
n 20
10)
En
ergy
requ
irem
ent
44.3
GW
h pe
r yea
r o
min
ing
rate
ass
umpt
ion
Ex
plos
ives
1,
180
tonn
es p
er y
ear
o m
inin
g ra
te a
ssum
ptio
n
Comminution, Ben
eficiatio
n an
d Hy
drom
etallurgy
Ener
gy re
quire
men
t 42
6 G
Wh
per y
ear
o p
ropo
rtion
ality
to T
hor L
ake
proj
ect
Tab
le 8
: Sum
mar
y of
the
bene
ficia
tion
mod
ellin
g
Stage
Type
Qua
ntity
Assumptions
Bene
ficiatio
n R
are
earth
con
cent
rate
pro
duce
d 13
9,00
0 to
nnes
per
yea
r o
75%
eff
icie
ncy
of th
e su
bseq
uent
stag
es
o 6
0% re
cove
ry o
f REE
s
W
aste
rock
gen
erat
ed
9.8
tonn
es p
er to
nne
of ra
re e
arth
co
ncen
trate
pro
duce
d
o F
ull r
ecov
ery
and
perf
ect
sele
ctiv
ity o
f Fe
and
Nb
min
eral
s
46
Figure 20: Beneficiation process in Bayan Obo for one tonne of original rock
As a consequence, the processing of one tonne of original ore results in the production of:
- 351 kg of iron and niobium (recovered to be later refined) - 60 kg of mixed rare earth concentrate - 589 kg of tailings
Considering the production of REO in 2010 (62,400 t) and assuming a 75% efficiency of the overall subsequent stages (Schüler et al. 2011), it is estimated that 139,000 tonnes of mixed-rare earth concentrate were produced that year.
The results and assumptions of the beneficiation process are summarised in Table 8.
9.1.4. Hydrometallurgy and separation of rare earths This stage was described in section 5.5. It is composed of several successive
chemical reactions.
Fe 350 kg 35%
Rare Earth 60 kg 6%
Nb 1.3 kg 0%
Gangue 588.7 kg 59%
35.1 %
6 %
58.9 %
Magnetic minerals
Tailings
Rare earth concentrate
Rare Earth 36 kg 60%
Gangue 24 kg 40%
Fe 350 kg 100%
Nb 1.3 kg 0%
Rare Earth 24 kg 4%
Gangue 564.7 kg 96%
47
For both deposits, the overall recovery rate of the separation and refining processes is considered to be 75% (Schüler et al. 2011). It is considered that the five different chemical reactions each have the same recovery rate rR:
!! = !. 75! = 94.4%
Considering that the bastnaesite/monazite ratio was 5:2 (71.4% of bastnaesite and 28.6% of monazite in Bayan Obo’s rare earth mineral) (Huang et al. 2005), each chemical reaction was scrutinised to estimate how much of every chemical is required per rare earth atom. This is described in the following section:
Chemical reactions
For bastnaesite: ReFCO3 ReFO + CO2
2 ReFO + 3 H2SO4 Re2(SO4)3 + 2HF+2 H2O
For monazite: 2 RePO4 + 3 H2SO4 Re2(SO4)3
+ 2 H3PO4
Re2(SO4)3+ 6 (NH4)HCO3 Re2(CO3)3 +3 (NH4)2SO4 + 3 CO2 + 3 H2O
Re2(CO3)3 + 6 HCl 2 ReCl3 + 3 H2CO3
ReCl3 + 3(HX)2 ReX6H3 + 3 HCl
ReX6H3 + 3 HCl ReCl3 + 3(HX)2
Acidic roasting
Carbonate
precipitation
Acid leaching
Solvent extraction
3/2 H2SO4 Heat
0.71 CO2 0.71 HF 0.71 H2O 0.29 H3PO4
3 (NH4)HCO3 3/2 (NH4)2SO4 3/2 CO2 3/2 H2O
3 HCl 3/2 H2CO3
ReFCO3 RePO4
Re2(SO4)3
Re2(CO3)3
ReCl3
Heat 3 (HX)2 3 (HX)2
48
The stoichiometric coefficients for the hydrometallurgy process are summarised in Table 9.
9.1.5. Refining Likewise, the estimation of the amounts of necessary chemicals for the refining
process was carried out based on the different chemical reactions.
Chemical reactions
2 ReCl3 + 3 C2H2O4 Re2(C2O4)3 + 6 HCl
Re2(C2O4)3+ 3/2O2 Re2O3+ 6 CO2 for La, Nd & Sm
Re2(C2O4)3+ 2 O2 2 ReO2 +6 CO2 for Ce
3 Re2(C2O4)3+11/2O2Re6O11+18CO2 for Pr
The stoichiometric coefficients for the refining process are summarised in Table 9.
9.1.6. Stripping ratio The stripping ratio is the ratio between the mass of waste rock that is generated and
the mass of mineral that goes for further processing. The calculation of the stripping ratio is composed of three steps.
Firstly, the yearly mass (mY) recovered in Bayan Obo deposit in 2010 is calculated from the mining rate of the mine:
!! = 16,250 ∗ 365 = 5.93 10! !"##$% Then, the mass of mineral (mM) that is processed is calculated from the rare earth
grade of the mineral rate (6%), the production of REO in 2010 (62,400 t), the beneficiation recovery (60%) and the recovery during subsequent processes (75%):
!! = !"# !"#$%&'(#)!"#!
!"#"$%&%'(%)#!"#$%"!& ∗ !"#$%$%&!"#$%"!& ∗ !"#$ !"#$ℎ!"#$%= 2.31 10!!"##$%
Finally, the mass of waste recovered (mWaste) is calculated:
!!"#$% = !! −!! = 3.62 10! !"##!" As a result, the stripping ratio in Bayan Obo is estimated:
!"#$%%$&' !"#$% =!!"#$%
!!= 1.57
For each tonne of mineral that is processed in the early stages, 1.57 tonne of waste are recovered.
Precipitation
Oxidation
3 HCl 3/2 C2H2O4
Re2(C2O4)3
3 CO2 Heat 0.93 O2
Rare earth oxide
ReCl3
49
Table 9: Summary of the stoichiometric coefficients in Bayan Obo
Stage Chemical Type: Input/Output (I/O)
Stoichiometric coefficient
Hydrometallurgy H2SO4 I 1.5
Hydrometallurgy (NH4)HCO3 I 3
Hydrometallurgy HCl I 3
Hydrometallurgy CO2 O 2.21
Hydrometallurgy H2O O 2.21
Hydrometallurgy H2CO3 O 1.5
Hydrometallurgy H3PO4 O 0.29
Hydrometallurgy (NH4)2SO4 O 1.5
Hydrometallurgy HF O 0.71
Refining C2H2O4 I 1.5
Refining O2 I 0.93
Refining HCl O 3
Refining CO2 O 3.75
50
9.2. Maoniuping deposit The calculations are explained in Appendix 5.
9.2.1. Beneficiation The rocks mined in Maoniuping lead to three different outputs: - A mix of aluminium, iron, manganese and lead which is separated at the gravity
separation step - A bastnaesite concentrate containing 70% of REEs (Schüler et al. 2011) - Tailings In order to estimate the amount of tailings, it is assumed that the gravity separation
recovers only and completely the four elements cited above (Al, Fe, Mn, Pb). Besides, the recovery of REEs during the flotation process is considered of 85%
(see Table 5). Figure 21 illustrates the distribution among the three types of outputs.
Figure 21: Beneficiation process in Maoniuping for one tonne of original rock
Rare earths minerals 43.4 kg 4%
Mn 38.9 kg 4%
Pb 19.7 kg 2%
Al 163 kg 16%
Fe 110 kg 11%
Gangue 625 kg 63%
33.1%
5.3%
Mineral recovery
Al 163 kg 49%
Fe 110 kg 33%
Mn 38.9 kg 12%
Pb 19.7 kg 6%
Rare earth
minerals 36.9 kg 70%
Gangue 15.8 kg 30%
Gangue 609.2 kg 99%
Rare earth
minerals 6.5 kg 1%
61.6%
Tailings
Rare earth concentrate
51
As a consequence, the processing of one tonne of original ore results in the production of:
- 331 kg of valuable minerals (Al, Pb, Mn, Fe) - 50 kg of bastnaesite concentrate - 619 kg of tailings Considering the production of REO in 2010 (31,200 t) and assuming a 75%
efficiency in the subsequent stages (Schüler et al. 2011), it is estimated that 59,400 t of bastnaesite concentrate were produced that year.
The results and assumptions of the beneficiation process are summarised in Table 10.
52
T
able
10:
Sum
mar
y of
the
bene
ficia
tion
mod
ellin
g in
Mao
niup
ing
Stage
Type
Qua
ntity
Assumptions
Bene
ficiatio
n B
astn
aesi
te c
once
ntra
te p
rodu
ced
59,4
00 to
nnes
per
yea
r o
75%
eff
icie
ncy
of th
e su
bseq
uent
st
ages
o
70%
reco
very
of R
EEs
Bene
ficiatio
n W
aste
rock
gen
erat
ed
11.7
tonn
es p
er to
nne
of ra
re e
arth
co
ncen
trate
pro
duce
d o
Ful
l rec
over
y an
d pe
rfec
t se
lect
ivity
of A
l, Pb
, Mn
and
Fe
Tab
le 1
1: S
umm
ary
of th
e m
inin
g an
d co
mm
inut
ion
proc
esse
s mod
ellin
g in
Mao
niup
ing
Stage
Type
Qua
ntity
Assumptions
Mining
Min
ing
rate
7,
100
tpd
o S
ame
strip
ping
ratio
as B
ayan
O
bo
o B
enef
icia
tion
proc
ess
assu
mpt
ion
(see
Ta
ble
10)
Mining
Ener
gy re
quire
men
t 21
.6 G
Wh
per y
ear
o D
itto
Mining
Expl
osiv
es
576
tonn
es p
er y
ear
o D
itto
Comminution, Ben
eficiatio
n an
d Hy
drom
etallurgy
Ener
gy re
quire
men
t 20
8 G
Wh
per y
ear
o P
ropo
rtion
ality
to T
hor L
ake
proj
ect
53
9.2.2. Mining and comminution The mining and comminution are described subsequently to the beneficiation
because the data already calculated help determining the requirements.
9.2.2.1. Stripping ratio It is assumed that the stripping ration in Maoniuping is equal to that in Bayan Obo.
Thus, the stripping ratio in Maoniuping is considered to be 1.57 (see 9.1.6).
9.2.2.2. Energy requirement for mining operations The energy requirements for the mining operations at Maoniuping were calculated
similarly as for Bayan Obo. The stripping ratio assumption makes it possible to calculate the total amount of
rock handled and thus the amount of energy required for the mining operations: 21.6 GWh are annually required to power the mining operations.
Once again, assuming that the mining operations are carried out with machinery (trucks, shovel…), this amount of energy is provided with fuel.
9.2.2.3. Explosives input Based on the estimation of Nilsson, it is calculated that the annual amount of ANFO
used in Maoniuping deposit accounts for 576 tonnes.
9.2.2.4. Comminution Like for Bayan Obo, it is estimated that the comminution, beneficiation and
hydrometallurgy operations in Maoniuping require 208 GWh per year. The results and assumptions of the beneficiation process are summarised in
Table 11.
54
9.2.3. Hydrometallurgy and separation of rare earths In Maoniuping, the process is simplified by the fact that only bastnaesite is
processed. Similarly than for Bayan Obo, the flows were estimated from the analysis of the chemical reactions.
The stoichiometric numbers of the hydrometallurgy process are summarised in Table 12.
ReFCO3 ReFO + CO2
2 ReFO + 3 H2SO4 Re2(SO4)3 + 2 HF +2 H2O
Re2(SO4)3+Na2SO42NaRe(SO4)2
2 NaRe(SO4)2 + 6 HCl 2 ReCl3 + Na2SO4 + 3 H2SO4
ReCl3 + 3(HX)2 ReX6H3 + 3 HCl
ReX6H3 + 3 HCl ReCl3 + 3(HX)2
9.2.4. Refining The refining process and chemical reactions are the very same as in Bayan Obo
(see 9.1.5).
The stoichiometric numbers of the refining process are summarised in Table 12.
Acidic roasting
Sulphate
precipitation
Acid leaching
Solvent extraction
3/2 H2SO4 Heat
1 CO2 1 HF 1 H2O
ReFCO3
Re2(SO4)3
½ Na2SO4
NaRe(SO4)2
3 HCl ½ Na2SO4
3/2 H2SO4
ReCl3
Heat 3 (HX)2 3 (HX)2
55
Table 12: Summary of the stoichiometric coefficients in Maoniuping
Stage Chemical Type: Input/Output (I/O)
Stoichiometric coefficients
Hydrometallurgy H2SO4 I 1.5
Hydrometallurgy Na2SO4 I 0.5
Hydrometallurgy HCl I 3
Hydrometallurgy HF O 1
Hydrometallurgy CO2 O 1
Hydrometallurgy H2O O 1
Hydrometallurgy H2SO4 O 1.5
Hydrometallurgy Na2SO4 O 0.5
Refining C2H2O4 I 1.5
Refining O2 I 0.93
Refining HCl O 3
Refining CO2 O 3
56
10. Life Cycle inventory Thanks to the estimation of the model and some data in various articles, it is
possible to carry out the Life Cycle Inventory. In this section, every figure is expressed per tonne of REOs produced.
Calculations for Bayan Obo (respectively Maoniuping) can be found in Appendix 6 (respectively Appendix 7)
The composition of one tonne of REOs in Bayan Obo (respectively Maoniuping) is described in Figure 17 (respectively Figure 20).
10.1. Input of chemicals, energy and explosives Table 13 inventories the necessary inputs.
10.2. Air emissions Bayan Obo air emissions are listed in Table 14.10
10.3. Output of wastes and chemicals Table 15 inventories the different wastes rejected when producing a tonne of REOs.
10 For Maoniuping processes, not enough data was found concerning air emissions to proceed to the same description.
57
Tab
le 1
3: R
equi
red
inpu
ts fo
r th
e di
ffer
ent s
tage
s
Type
of inp
ut
Stage
Inpu
t Ba
yan Obo
Mao
niup
ing
Chem
ical
Hyd
rom
etal
lurg
y H
2SO
4 67
7 kg
67
8 kg
Chem
ical
Hyd
rom
etal
lurg
y N
H4H
CO
3 1,
091
kg
-
Chem
ical
Hyd
rom
etal
lurg
y N
A2S
O4
- 32
7 kg
Chem
ical
Hyd
rom
etal
lurg
y H
Cl
504
kg
505
kg
Chem
ical
Ref
inin
g C
2H2O
4 62
2 kg
62
3 kg
Chem
ical
Ref
inin
g O
2 13
8 kg
11
1 kg
Chem
ical
Sepa
ratio
n P
507
Unk
now
n U
nkno
wn
Explosive
Min
ing
AN
FO
19 k
g 18
.5 k
g
Energy
Min
ing
Fuel
71
0 kW
h 69
2 kW
h
Energy
Com
min
utio
n, B
enef
icia
tion
and
Hyd
rom
etal
lurg
y El
ectri
city
6.
83 M
Wh
6.67
MW
h
58
Tab
le 1
4: E
mis
sion
to th
e ai
r du
ring
pro
cess
es in
Bay
an O
bo
Stage
Emission
Qua
ntity
Re
ference
Milling
Dus
t 13
kg
o H
urst
201
0
Milling
Dus
t con
tain
ing
ra
dioa
ctiv
e pa
rticl
es
1 kg
o
Sch
üler
, et a
l. 20
11 11
Acidic ro
astin
g W
aste
gas
es (i
nc. H
F, S
O2,
SO3)
9,
600
to 1
2,00
0 m
3 o
Sch
üler
, et a
l. 20
11
Tab
le 1
5: O
utpu
ts d
isch
arge
d
Type
of inp
ut
Stage
Outpu
t Ba
yan Obo
Mao
niup
ing
Waste
Min
ing
Was
te ro
ck
58.2
t 56
t
Waste
Ben
efic
iatio
n W
aste
slag
20
.4 t
21.8
t
Waste
Ben
efic
iatio
n R
adio
activ
e w
aste
slag
1.
4 t
300
kg
Waste
Ben
efic
iatio
n A
mou
nt o
f ThO
2
in w
aste
slag
14
.2 k
g 10
kg
11 A
ccor
ding
to S
chül
er, e
t al.,
the
Chi
nese
Min
istry
of
Envi
ronm
enta
l Pro
tect
ions
est
imat
es th
at th
e am
ount
of
thor
ium
con
tain
ing
dust
em
itted
eac
h ye
ar is
abo
ut 6
1.8
tonn
es (0
.99
kg p
er to
nne
of R
EO p
rodu
ced
with
an
annu
al o
utpu
t of 6
2,40
0t) (
Schü
ler,
et a
l. 20
11).
59
Type
of inp
ut
Stage
Outpu
t Ba
yan Obo
Mao
niup
ing
Waste
Aci
dic
roas
ting
and
acid
le
achi
ng
Was
tew
ater
75
m3
12
-
Waste
Sepa
ratio
n an
d re
finin
g Th
O2 i
n w
aste
wat
er
0.6
kg
0.26
Chem
icals
Hyd
rom
etal
lurg
y C
O2
423
kg
192
kg
Chem
icals
Hyd
rom
etal
lurg
y H
2O
173
kg
78 k
g
Chem
icals
Hyd
rom
etal
lurg
y H
2CO
3 34
6 kg
-
Chem
icals
Hyd
rom
etal
lurg
y H
2SO
4 -
640
kg
Chem
icals
Hyd
rom
etal
lurg
y H
3PO
4 12
4 kg
-
Chem
icals
Hyd
rom
etal
lurg
y (N
H4)
2SO
4 86
1 kg
-
Chem
icals
Hyd
rom
etal
lurg
y N
A2S
O4
- 32
7 kg
Chem
icals
Hyd
rom
etal
lurg
y H
F 62
kg
87 k
g
Chem
icals
Sepa
ratio
n N
H4H
CO
3 61
kg
-
Chem
icals
Sepa
ratio
n H
Cl
28 k
g 28
kg
Chem
icals
Sepa
ratio
n H
2SO
4 38
kg
-
12 (H
urst
201
0)
60
Type
of inp
ut
Stage
Outpu
t Ba
yan Obo
Mao
niup
ing
Chem
icals
Sepa
ratio
n H
2SO
4 38
kg
-
Chem
icals
Ref
inin
g C
O2
760
kg
575
kg
Chem
icals
Ref
inin
g H
Cl
476
kg
477
kg
Chem
icals
Ref
inin
g C
2H2O
4 35
kg
35 k
g
61
11. Life Cycle Impact Assessment In order to conduct this Life Cycle Impact Assessment, different impact categories
were defined: - Global Warming - Acidification - Eutrophication - Radioactive waste generation - Land use - Toxicity in wastewater For each of these categories, the LCI results were classified and assigned to one or
several category. The calculations of the following sections are all included in Appendix 8.
11.1. Global Warming
11.1.1. Classification The following elements were identified as taking part to global warming: - CO2 emitted during chemical processes - CO2 emitted during production of electricity - CO2 emitted when burning fuel for mining
The carbon emissions are quantified in this section.
11.1.2. Characterisation Table 16 summarises the impact indicators concerning global warming.
Table 16: Impact indicator for global warming
Classification Unit Bayan Obo Maoniuping
Emissions from chemical reactions kg of CO2 1,180 770
Emissions from fuel burning kg of CO2 170 170
Emissions from electricity use kg of CO2 5,100 5,000
Overall emissions kg of CO2 6,450 5,940
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11.2. Acidification
11.2.1. Classification The following elements were identified as taking part to the acidification
phenomenon: - Sulphur Dioxide (SO2) - Hydrochloric acid (HCl) - Hydrofluoric acid (HF) - Ammonia (NH3)
11.2.2. Characterisation Table 17 summarises the impact indicators concerning acidification.
Table 17: Impact indicator for acidification
Classification Unit Bayan Obo Maoniuping
SO2 (gas) kg of SO2 24.8 640
HCl kg of SO2eq 444 444
HF (gas) kg of SO2eq 99 139
NH3 kg of SO2eq 115 -
Atmosphere acidification potential
kg of SO2eq 124 779
Wastewater acidification potential
kg of SO2eq 559 444
63
11.3. Eutrophication
11.3.1. Classification The following elements were identified as taking part to the acidification
phenomenon: - Ammonia - Phosphate
11.3.2. Characterisation Table 18 summarises the impact indicators concerning eutrophication.
Table 18: Impact indicator for eutrophication
Classification Unit Bayan Obo Maoniuping
Phosphates kg of H3PO4 124 -
Ammonia kg of H3PO4eq 304 -
Discharge in wastewaters kg of H3PO4eq 428 -
11.4. Radioactive waste generation
11.4.1. Classification The following types of radioactive waste were identified:
- Radioactive waste slag - Radioactive wastewater
11.4.2. Characterisation Table 19 summarises the impact indicators concerning radioactive waste generation.
Table 19: Impact indicator for radioactive waste generation
Classification Unit Bayan Obo Maoniuping
Activity of waste slag Bq 5.1 107 3.6 107
Specific activity of waste slag Bq/kg 3.6 104 1.25 105
Activity of wastewater Bq 2.1 106 9.3 105
Specific activity of wastewater m3 2.9 104 -
64
Classification Unit Bayan Obo Maoniuping
Radioactivity discharge Bq 5.3 107 3.7 107
11.5. Land use
11.5.1. Classification The following elements were identified as taking part to land use: - waste rock - wastewater
11.5.2. Characterisation Table 20 summarises the impact indicators concerning land use.
Table 20: Impact indicator for land use
Classification Unit Bayan Obo Maoniuping
Waste rock m3 20.4 23.8
Wastewater m3 75 -
Overall volume required
m3 95.4 23.8
11.6. Toxic chemical discharge in wastewater In this section, the different sources of toxicity are listed. Their toxicity is described
in Appendix 9.
11.6.1. Classification The following elements were identified as potential toxic elements discharged in
wastewaters: - Oxalic acid - Ammonium bicarbonate - Ammonium sulphates - Sodium sulphates - Sulphuric acid
65
11.6.1. Characterisation Table 21 summarises the impact assessments concerning discharge of toxic
chemicals in wastewaters.
Table 21: Impact indicator for toxicity in wastewater
Classification Unit Bayan Obo Maoniuping
Oxalic acid kg 35 35
Ammonium bicarbonate kg 61 -
Ammonium sulphates kg 861 -
Sodium sulphates kg - 327
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12. Life Cycle Interpretation 12.1. Identification of the significant issues
This section aims at identifying the data elements, the assumptions that contribute the most to the results of the LCI and LCIA. It is also focused on determining whether there are anomalies in the results or not.
12.1.1. Contribution analysis
12.1.1.1. Model The process modelling is the keystone of this LCA. This modelling helped
described what are the different stages. As a consequence, the results depend directly on this model, it represents a significant contributor.
The chemical reactions were described based on a literature review, they play an essential role in the calculation of results.
The beneficiation process was not described in much detail. As a result it is not possible to estimate the inputs and outputs necessary to its operations.
Seven impact categories were defined in the LCIA. As a result, only impacts from these categories were discussed.
12.1.1.2. Data
Throughout the LCA, the 2010 productions of both Bayan Obo and Maoniuping deposits have been extensively used.
Concerning the data, a significant issue was the very low availability of data concerning Maoniuping’s deposit contrary to Bayan Obo’s deposit.
12.1.1.3. Assumption A few assumptions are significant to the results of the LCA: - it is assumed that the daily mining rate is proportional to the REO output of
a deposit, as a result it is estimated that the daily mining rate was 16,250 tpd in 2010. This figure is used numerous times throughout the LCA.
- for the energy calculations (for the comminution, beneficiation and hydrometallurgy operations), it is assumed that the two Chinese mines can be compared to a Canadian mining project. This represents the most of the energy requirements.
- the hydrometallurgy and refining operations are assumed to have a 75% efficiency. Besides, it was assumed that each chemical step had a efficiency of 94.4%
- the chemical reactions were assumed to take place with stoichiometric quantities
- it is assumed that the chemicals used are neither recovered nor recycled, they all end up in wastewater
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12.2. Completeness, sensitivity and consistency of data
12.2.1. Completeness check For each mine, the data calculated in the LCI and LCIA are consistent with both the
goal and the scope of the LCA. The data cover every primary activity identified in the model of the processes.
However, within the primary activities, results are sometimes not complete due to a lack of data.
12.2.1.1. Raw material For this matter, the data are as complete as possible.
12.2.1.2. Energy The following energy requirements were not considered due to a lack of data: - energy consumed during refining operations (e.g. rare earth oxidation) - energy consumed during the transport of the ores As a consequence, it is likely that the energy consumption and the carbon emissions
are higher than calculated.
12.2.1.3. Chemical inputs and outputs The following chemical inputs and outputs were not considered due to a lack of
data: - chemicals used during the beneficiation process and notably the froth
flotation and the associated discharge/recovery - chemicals used for the separation of REEs such as P507 - chemicals used alongside chemical reactions (e.g. solvents, catalysts,
pH regulators)
As a result, their flows are unknown.
12.2.1.4. Water consumption
The water consumption was not estimated for any of the two mines due to a lack of data on this matter.
12.2.1.5. Environmental releases
The releases that were described and quantified are only those that were documented in the literature. Therefore, it is likely that other unidentified releases to air or water happen during these operations.
12.2.2. Sensitivity check The sensitivity of the assumptions is described in Table 22.
12.2.3. Consistency check All the assumptions described in section 12.1.1.3 are found to be consistent with the
goal and scope of the study.
On the contrary, the process modelling described in section 12.1.1.1 is found to be inconsistent with the goal of the study. Leaving the beneficiation process unresolved
68
makes that the results do not describe correctly the necessary flows to achieve REOs. Due to this inconsistency, it is likely that several different chemical inputs and outputs are neglected as well as some environmental releases.
12.2.4. Limitations of the study In this section, the level of confidence in the assumptions is discussed as well as
their sensitivity.
Table 22: Assumptions analysis
Assumptions Level of confidence (low/medium/high)13 Implications and sensitivity
Mining rate assumption medium
The results are proportional to the mining rate. So it is not likely that the results will
change drastically because of this assumption.
Proportionality to Thor Lake
project low
This assumption neglects any economy of scales which is likely to be the case in reality.
A significant change in this assumption is likely to change considerably the global
warming impact assessment.
75% efficiency of the
hydrometallurgy and refining processes
high
This data is based on the literature and is therefore reliable. If it were to change, it
would cause the chemical inputs and outputs to change inverse proportionally.
Recovery rate of the
beneficiation process in both
mines
high This data is based on the literature. It is a
sensitive data because it helped to calculate wastes, radioactive wastes as well as land use.
Full recovery and perfect
selectivity of Fe and Nb minerals in Bayan Obo
low This assumption is not very sensitive since a difference would slightly change the amount
of waste rock produced.
Full recovery and perfect
selectivity of Al, Pb, Mn and Fe in Maoniuping
low This assumption is not very sensitive since a difference would slightly change the amount
of waste rock produced.
13 These are personal assessments.
69
Assumptions Level of confidence (low/medium/high)13 Implications and sensitivity
Same stripping ratio in Maoniuping as Bayan Obo
low This assumption is sensitive since a slight
change is likely to lead to significant differences in many categories
12.3. Conclusions of the life cycle assessment This life cycle assessment was carried out in order to provide information about the
production of REOs and estimate the energy and material flows necessary to it. The conclusion of this study is divided into two sections: analysis where the results are discussed and opinion where the study in itself is discussed.
12.3.1. Analysis
12.3.1.1. Global warming For both deposits, the CO2 emissions related to the production of a tonne of REO
are about 6 tonnes. This is a considerable ratio, that has to be taken into account when studying
products that contains REEs. Finally, the emission of both Maoniuping and Bayan Obo operations in terms of
CO2 appear to be quite similar.
12.3.1.2. Acidification potential The acidification potential (when producing a tonne of REOs) appears to be
significant since hundreds of kilograms of SO2eq are released both in the atmosphere and wastewater.
Besides, the operations in Maoniuping and Bayan Obo seem to have a comparable acidification potential.
12.3.1.3. Eutrophication potential The eutrophication potential of Maoniuping is nil. This is due to the absence of
monazite in Maoniuping’s ore. On the contrary, the operations in Bayan Obo generate a significant amount of
phosphate (or phosphate equivalent) since over 400 kg of phosphate equivalent are generated when producing a tonne of REOs.
12.3.1.4. Radioactive waste generation
Both operations generate significant radioactivity. Although this radioactivity is already occurring in the virgin ore, the result of these processes is to concentrate radioactive materials.
Therefore, the radioactive wastes have a higher radioactivity than natural ore. According to the UK regulation, they can be classified as low level radioactive waste
70
(European Commission 1998). Thus, they need to be disposed of carefully in order to avoid spilling this radioactive concentrate out.
Although the wastewaters appear to be less radioactive than the waste slag, it is necessary to build secure impoundment, to prevent radioactive material from percolating into the soil and polluting ground waters.
12.3.1.5. Land use
Although the volume of waste generated per tonne of REO does not seem too important, the accumulation of all these wastes through decades of functioning have created massive stockpiles of waste.
As an example, some figures are given below concerning Bayan Obo deposit:
- surface of the tailing impoundment: 11 km2 (roughly 65 million m3) (Schüler et al. 2011)
- surface of the open pit mines (including all orebodies): 8.13 km2 (Wu 2010) - surface of the waste rock storages: 5.6 km2 (estimated from an aerial picture
of Bayan Obo deposit)
12.3.1.6. Discharge of toxic chemicals Discharge of toxic chemicals is a serious issue in both Maoniuping and Bayan Obo.
Much chemicals end up in wastewater and disposing toxic chemical in a pond may result in toxicity infiltrating into soils or evaporating in the air.
Both deposits reject oxalic acid which appears to be potentially the most toxic chemical discharged in the ones that were identified in this study.
A newspaper report by Simon Parry describing the effects of the “lake of toxic waste” is quoted in Appendix 10.
12.3.2. Discussions on the life cycle assessment
12.3.2.1. Scope definition The scope was defined in concordance with two ideas:
- the assessment of the environmental impacts of the production of REOs represents a comprehensive purpose as this is the first step in the production of every REE of any form
- the scope took into consideration the time available for this study
Consequently, although the study could have encompassed the production of rare earth metals or even rare earth products, it is estimated that the scope was the best compromise possible.
12.3.2.2. Assumptions Several assumptions were made throughout this LCA. Although most of them are
based on literature, some assumptions were identified as critical as they are sensitive and do not have a high level of confidence:
- the assumption on the stripping ratio in Maoniuping was made in order to enable further calculations. It has a low level of confidence and a high sensitivity
71
- the proportionality to the Thor Lake project neglects any economy of scale. This assumption appears to be critical in the calculation of the global warming impacts although it does not have a high level of confidence.
12.3.2.3. Process modelling
The results of both Maoniuping and Bayan Obo are really close. This can be explained with two reasons:
- the model for Maoniuping lacked several data and therefore numerous assumption were based on Bayan Obo information
- the two deposit are very similar in terms of ore and rare earth content and composition
The process modelling is likely to be a faulty part of this LCA. It was chosen taking into account the availability of information and data. Thus they result more from an obligation than a choice. Besides, the process modelling is the keystone of the whole LCA. Therefore, if this study is to be improved, it would be interesting to:
- describe the beneficiation operations in more details - model or find information on the consumption of water throughout the
production of REOs - find more precise information on Maoniuping’s operations - describe more meticulously the chemical steps, chemical reactants and
conditions
12.3.2.4. Life cycle inventory In the life cycle inventory, attention was paid to chemical inputs and outputs, air
emissions and waste generation. These categories were selected based on the available information.
However, it would have been interesting to also focus on the water consumption since it is likely to be a significant in beneficiation and hydrometallurgy processes. Besides, the operation in Bayan Obo takes place in an arid environment. Therefore, the impacts of abstracting water can be important.
12.3.2.5. Life cycle impact assessment Only six categories were chosen for the LCIA since it takes into account the
description carried out in the life cycle inventory. However, if it had been possible, this LCIA could also have focuses on other midpoint impacts:
- soil toxicity (modelling of the infiltrations) - stream toxicity (modelling of the infiltrations) - water use (water consumption modelling) Further studies could get down to assessing these impacts.
12.3.2.6. Acquisition of information The LCA of this study relies only on information found in literature and
assumptions. It would be certainly useful to have a look at other kinds of information such as LCA software database, governmental or industrial documentations. Since the latter is almost exclusively in Chinese, it would be to through it with a native Chinese speaker in order to collect other primary data.
72
12.3.2.7. Specificity of the life cycle assessment This study was focused on two Chinese mines that were described in details.
However, general assumptions were made, and only very generic processes were scrutinised.
As a result, it is likely that the results can be generalised to some extent to other rare earth projects both in China and abroad.
73
13. Conclusion The aim of this study was to assess some of the environmental impact of producing
rare earth oxides. More specifically, attention was given to two Chinese mines which account for 70% of the global rare earth production.
Thus, after a description of the operations in these both mines, it was decided to carry out a life cycle assessment methodology to these mines in order to evaluate the environmental impacts related to the following categories: global warming, acidification, eutrophication, radioactive waste generation, land use and toxicity in waste waters.
This life cycle assessment was composed of several phases: firstly the processes taking place in the two mines were described in details. Secondly, a life cycle inventory listed every input and output flows necessary to the operations. Thirdly, the impacts related to the above categories were assessed and expressed in a same unit. Finally, the life cycle interpretation helped to analysed the results.
It appeared that the production of rare earth oxides in these two mines is associated with a high environmental cost. In addition to CO2 emissions, the processes generates massive amount of waste slag (some of which is radioactive) and wastewater that have to be dealt with properly. The waste management has to be strict in order to avoid radioactive or toxic run-offs.
As a result, it emerged that the low economical cost of Chinese rare earth production goes along a significant environmental cost that should definitely be taken into consideration when producing and consuming rare earth elements.
The introduction of quotas in Chines exportation is possibly a political sign that Chinese authorities do not want to bear alone the responsibility of supplying the world with rare earth elements and try to share that environmental burden with other countries.
74
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Appendix
Appendix 1: USGS and Chinese classification
1. Different classifications a. USGS
USGS defines the reserve as “the part of the reserve base which could be economically extracted or produced at the time of determination”. The reserve base being “the part of an identified resource that meets specified minimum physical and chemical criteria related to current mining and production practices […] The reserve base includes those resources that are currently economic (reserves), marginally economic (marginal reserves) and some of those that are currently subeconomic (subeconomic resources)” (USGS 2011).
b. Chinese classification
According to Tse, “the Chinese reserve classification system best approximates reserves as defined in the U.S. Bureau of Mines and U.S. Geological Survey (1980) in USGS Circular 831”(Tse 2011). In this document, reserves are defined as “that portion of an identified resource from which a usable mineral or energy commodity can be economically and legally extracted a the time of determination” (USGS 1980).
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Appendix 2: Description of the flotation processes
The flotation process consists in mixing the ore with chemicals to make the bastnaesite/monazite hydrophobic.
Then air is injected through the agitated slurry (mix of ore and water) to produce froth. Since the rare earth ores is hydrophobic, it is attracted to air bubbles and thus stays at the surface of the mixture. Waste material sinks to the bottom of the container and can be removed (EPA 1994).
There are six broad types of flotation reagents (Fuerstenau et al. 2007): - the frother is added to control bubble size and froth stability - the collectors are surface-active reagents that impart hydrophobicity to minerals - the activators enhance collector adsorption onto a specific mineral - depressants are reagents that prevent collector adsorption to unwanted mineral
surfaces - modifiers modify the flotation environment - flocculants are added to assist dewatering of the flotation concentrates
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Appendix 3: Description of the solvent extraction process
The solvent extraction of REEs in EHEHPA follows a mere observation: the bigger the atomic number of the REE the more stable the resulting complex.
Figure 22 shows how the separation factor between two REEs matches with that principle (Hao et al. 1995).
Figure 22: Separation factor of rare earths in the Ln(III)-HCl-EHEHPA system (Sato 1989)
As a result, the process to separate REEs from each other uses that principle. It is composed of several steps as described in Figure 23.
Figure 23: Separation flowsheet for bastnasite (Yan et al. 2006)
The machine used for the solvent extraction is a mixer settler extractor (Zhong et al. 2010) (Zhong 1995).
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Appendix 4: Calculations for the Bayan Obo processes modelling
2. Mining a. Mining rate
Chinese production of REOs increased by 8.3% between 2006 and 2010 (from 120,000 to 130,000) (USGS 2006 ; USGS 2011), it is assumed that Bayan Obo’s production increased similarly. As a result, the mining rate in 2010 is 8.3% bigger than the one in 2006:
15,000 ∗ 1.083 ≈ 16,200 !"# b. Energy requirement
Calculation of the annual energy consumption for the mining operations:
- daily energy consumption: 16,200 ∗ 7.5 !"ℎ = 121.5 !"ℎ
- annual energy consumption: 121.5 ∗ 365 ≈ 44.3 !"ℎ
c. Explosives input Calculation of the annual amount of ANFO required:
- daily requirements: 16,200 ∗ 0.2 !" = 3,240 !" - annual requirements: 365 ∗ 3.24 ≈ 1,180 !"##$%
3. Comminution
Considering that the power requirements of Bayan Obo are proportionally equal to those estimated for the Thor Lake project, the average power was estimated:
- average power requirement:
6 ∗16,2002,000 = 48.6 !"
- annual amount of energy: 48.6 ∗ 8,760 ≈ 426 !"ℎ
4. Beneficiation
Calculation of the results displayed in Table 8: - since the annual output is 62,400 t and considering that the concentrate contains
60% of REEs and that the subsequent steps have an overall efficiency of 75%. The amount of rare earth concentrate produced is:
62,4000.75 ∗ 0.6 ≈ 139,000 !"##$%
- the amount of waste rock generated per tonne of rare earth concentrate is
calculated taking into account that 589 kg of waste rock are generated when producing 60 kg of rare earth concentrate. As a result, the amount of waste rock produced per tonne of rare earth concentrate is:
58960 ∗ 1! = 9.8 ! !" !"#$% !"#$
5. Hydrometallurgy and refining The stoichiometric quantities were calculated directly from the models exposed in
sections 9.1.4 and 9.1.5.
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6. Stoichiometry The stoichiometric coefficients are calculated directly from the chemical reactions,
however, the stoichiometric coefficient for O2 in the refining process needs to be explained.
This calculation is based on the relative proportion of light REEs at this stage. This proportion is illustrated in Figure 24:
Figure 24: Relative proportion of light rare earth elements in Bayan Obo concentrate (Spooner 2005)
As a result, knowing that the stoichiometric coefficient for La, Nd and Sm is 0.75, 1 for Ce and 1.8 for Pr, it is possible to calculate the overage coefficient:
0.24+ 0.18+ 0.02 ∗ 0.75+ 0.51 ∗ 1+ 0.05 ∗ 1.8 = 0.93
Ce 51%
La 24%
Pr 5% Nd
18%
Sm 2%
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Appendix 5: Calculations for the Maoniuping processes modelling
1. Beneficiation Calculation of the results displayed in
Table 10: - since the annual output is 31,200 t and considering that the concentrate contains
70% of REEs and that the subsequent steps have an overall efficiency of 75%. The amount of bastnaesite concentrate produced is
31,2000.75 ∗ 0.7 ≈ 59,400 !"##$%
- the amount of waste rock generated per tonne of rare earth concentrate is
calculated taking into account that 619 kg of waste rock are generated when producing 52.7 kg of bastnaesite concentrate. As a result, the amount of waste rock produced per tonne of rare earth concentrate is:
61952.7 ∗ 1! = 11.7 ! !! !"#$% !"#$
2. Mining and comminution
a. Mining rate calculation Since bastnaesite concentrate represents 5.3% of all the rock processed in
beneficiation, it is possible to calculate the amount of rock processed in the beneficiation from the amount of bastnaesite concentrate produced:
59,4000.053 = 1.12 10! !"##$%
The stripping ratio being 1.57, it is possible to calculate the annual amount of rock excavated in the mining operations: 1.12 10! ∗ 1+ 1.57 = 2.88 10! !"##$%
As a result, the mining rate is:
2.88 10!
365 = 7,900 !"#
b. Energy requirements for mining
- Annual energy requirements: 2.88 10! ∗ 7.5 !"ℎ = 21.6 !"ℎ c. Explosives
Thanks to the annual amount of rock handled and Nilsson’s figure it is possible to calculate the annual amount of explosive required: 2.88 10! ∗ 0.2 = 576 10! !" = 576 !
3. Comminution
Considering that the power requirements of Maoniuping are proportionally equal to those estimated for the Thor Lake project, the average power was estimated:
- average power requirement:
6 ∗7,9002,000 = 23.7 !"
- annual amount of energy: 23.7 ∗ 8,760 ℎ!"#$ ≈ 208 !"ℎ
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- Stoichiometry
The stoichiometric coefficients are calculated directly from the chemical reactions, however, the stoichiometric coefficient for O2 in the refining process needs to be explained.
This calculation is based on the relative proportion of light REEs at this stage. This proportion is illustrated in Figure 25.
Figure 25: Relative proportion of light rare earth elements in Maoniuping concentrate
As a result, knowing that the stoichiometric coefficient for La, Nd and Sm is 0.75, 1 for Ce and 1.8 for Pr, it is possible to calculate the overage coefficient:
0.3+ 0.13+ 0.01 ∗ 0.75+ 0.51 ∗ 1+ 0.05 ∗ 1.8 = 0.93
Ce 51%
La 30%
Pr 5%
Nd 13%
Sm 1%
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Appendix 6: Calculation of the life cycle inventory data for Bayan Obo
1. Molar quantity Firstly, the molar quantity contained in one tonne of REOs is calculated.
Considering that one tonne of REOs is composed as in Figure 17. It is calculated that it contains 4,346 moles of the different REOs.
2. Input of consumed product a. Chemicals
Thanks to the above molar quantity and the stoichiometric coefficients modelled in section 9.1. It is possible to calculate the stoichiometric amount for each chemical input, these results are given in Table 23.
Table 23: Calculation of the chemical inputs for Bayan Obo
Chemical Stoichiometric coefficient
Molar mass (g/mol)
Minimum required mass (stoichiometric quantities)
Required mass (94.4%
efficiency)
H2SO4 1.5 98 639 kg 677 kg
NH4HCO3 3 79 1,030 kg 1,091 kg
HCl 3 36.5 476 kg 504 kg
C2H2O4 1.5 90 587 kg 622 kg
O2 0.93 32 104 kg 111 kg
b. Explosives
To calculate the amount of explosive used per tonne of REOs, the annual amount of ANFO used (1,180 t) is merely divided by the annual oxide output of Bayan Obo (62,400t).
c. Energy
The energy requirements for the production of a tonne of REOs are calculated similarly than for the explosives: with a simple division of the energy inputs described in section 9.1. 3. Output of wastes and chemicals
a. Wastes From section 9.1.6, the annual amount of waste rock generated in Bayan Obo can be
calculated: 2.31 10! ∗ 1.57 = 3.63 10! !"##$% As a result, per tonne of REOs produced, the amount of waste rock generated is
3.63 10! ∗62,400 = 58.2 !"##$%
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b. Waste slag The waste slag is the rock discharged after the beneficiation process. The amount of
rock discharged at this stage is: 2.31 10! ∗ 0.589 = 1.36 10! !"##$% Hence, the amount of waste slag generated per tonne of REO produced is 21.8
tonnes. Among this waste slag it is possible to distinct between radioactive and non-radioactive waste slag.
The radioactive waste slag amounts to 1.4 tonnes (Xu and Peng 2009). As a result, the non radioactive waste slag amounts to 20.4 tonnes.
c. Thorium oxide in wastewater and waste slag According to Chen, the thorium oxide content in Bayan Obo ore is 0.04%. As a
result, the amount of ThO2 processed each year in the comminution and beneficiation steps is equal to (Chen et al. 2003):
2.3 10! ∗ 0.04% = 925 !"##$% According to Figure 20, 95.9% of the processed thorium oxide ends up in waste slag
and 4.1% ends up in rare earth concentrate. As a result, the annual amount of ThO2 that ends up in waste slag is equal to:
925 ∗ 0.959 = 887 !"##$%
Consequently, the amount of thorium oxide that ends up in waste slag per tonne of REOs produced is equal to:
88762,400 = 14.2 !"
Similarly, it is calculated that the amount of ThO2 that ends up in wastewater for each tonne of REO is equal to 0.6 kg.
d. Chemicals H2SO4, NH4HCO3, HCl and C2H2O4 outputs result from the fact that each reaction
was considered to have a 94.4% efficiency. Therefore, even if all the rare earth molecules are processed, some of these chemicals remain in the solution and are discharged in wastewater. What remains in solution is the amount of chemical that is in excess so that all the rare earth molecules are transformed.
The other chemical outputs are calculated similarly than for the chemical inputs (see Table 23).
Table 24: Calculation of the chemical outputs for Bayan Obo
Chemical Stoichiometric coefficient Molar mass (g/mol) Stoichiometric
output
CO2 2.21 44 423 kg
H2O 2.21 18 173 kg
H2CO3 1.5 53 346 kg
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Chemical Stoichiometric coefficient Molar mass (g/mol) Stoichiometric
output
H3PO4 0.29 98 124 kg
(NH4)2SO4 1.5 132 861 kg
HF 0.71 20 62 kg
CO2 3 44 574 kg
HCl 3 36.5 476 kg
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Appendix 7: Calculation of the life cycle inventory data for Maoniuping
1. Molar quantity Firstly, the molar quantity contained in one tonne of REOs is calculated.
Considering that one tonne of REOs is composed as in Figure 18. It is calculated that it contains 4,353 moles of the different REOs.
2. Input of consumed product a. Chemicals
Thanks to the above molar quantity and the stoichiometric coefficients modelled in section 9.2. It is possible to calculate the stoichiometric amount for each chemical input, these results are given in Table 25.
Table 25: Calculation of the chemical inputs for Maoniuping
Chemical Stoichiometric coefficient
Molar mass (g/mol)
Minimum required mass (stoichiometric quantities)
Required mass (94.4%
efficiency)
H2SO4 1.5 98 640 kg 678 kg
Na2SO4 0.5 142 309 kg 327 kg
HCl 3 36.5 477 kg 505 kg
C2H2O4 1.5 90 587 kg 623 kg
O2 0.93 32 104 kg 111 kg
b. Explosives
To calculate the amount of explosive used per tonne of REOs, the annual amount of ANFO used (576 t) is merely divided by the annual oxide output of Maoniuping (31,200t).
c. Energy
The energy requirements for the production of a tonne of REOs are calculated similarly than for the explosives: with a simple division of the energy inputs described in section 9.2. 3. Output of wastes and chemicals
a. Wastes From section 9.2, the annual amount of waste rock generated in Bayan Obo can be
calculated.
The annual amount of rock handled is 365 ∗ 7,900 !"# = 2.88 10!!"##$% (see Appendix 5 for the mining rate calculation).
The annual amount of bastnaesite concentrate is 59,400 tonnes (see 9.2.1).
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Since the mining ratio is 1.57, the amount of waste rock generated is:
2.88 10! ∗1.57
1.57+ 1 = 1.76 10!!"##$%
As a result, per tonne of REOs produced, the amount of waste rock generated is:
1.76 10!
31,200 = 56 !"##$%
b. Waste slag The waste slag is the rock discharged after the beneficiation process. The amount of
rock discharged at this stage is: 1.12 10! ∗ 0.616 = 6.91 10! !"##$% (1.12 106 tonnes being the amount of rock processed).
Hence, the amount of waste slag generated per tonne of REO produced is 22.1 tonnes. Among this waste slag it is possible to distinct between radioactive and non-radioactive waste slag.
The radioactive waste slag amounts to 300 kg (Xu and Peng 2009). As a result, the non radioactive waste slag amounts to 21.8 tonnes.
c. Thorium oxide in wastewater and waste slag According to Xu and Peng, the amount of thorium oxide that ends up in waste slag
per tonne of REOs produced is 10 kg (Xu and Peng 2009). From Figure 21, it is calculated that 97.5% of the ThO2 goes into waste slag and
2.5% into rare earth concentrate (and then in wastewater). As a result, the amount of ThO2 in wastewater is estimated to be 0.26 kg per tonne of REOs produced.
d. Chemicals H2SO4 and C2H2O4 outputs result from the fact that each reaction was considered to
have a 94.4% efficiency. Therefore, even if all the rare earth molecules are processed, some of these chemicals remain in the solution and are discharged in wastewater. What remains in solution is the amount of chemical that is in excess so that all the rare earth molecules are transformed.
The other chemical outputs are calculated similarly than for the chemical inputs (see Table 23).
Table 26: Calculation of the chemical outputs for Maoniuping
Chemical Stoichiometric coefficient Molar mass (g/mol) Stoichiometric
output
CO2 1 44 192 kg
H2O 1 18 78 kg
H2SO4 1.5 98 640 kg
Na2SO4 0.5 142 327 kg
HF 1 20 87 kg
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Chemical Stoichiometric coefficient Molar mass (g/mol) Stoichiometric
output
CO2 3 44 575 kg
HCl 3 36.5 505 kg
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Appendix 8: Calculation of the life cycle impact assessment data
1. Global warming a. Emissions from chemical reactions
These data come directly from the life cycle inventory in section 10. b. Emissions from fuel burning in the mining operations
Firstly, the amount of energy necessary for the mining phase is into a volume of gasoline. This is done based on gasoline energy density (35 MJ/L) (Tribal Energy and Environmental Information 2011).
Then, the emission of CO2 is calculated considering that the combustion of gasoline generates 2.38 kg CO2 per litre (EPA 2005).
Results are displayed in Table 27.
Table 27: CO2 emissions for mining operations
Baotou Maoniuping
Mining energy (kWh) 710 kWh 692 kWh
Equivalent amount of gasoline (L) 73 71
Emissions of CO2 (kg) 174 169
c. Emissions from electricity use
Assuming that the processes of comminution, beneficiation and hydrometallurgy are completely powered with Chinese electricity, it is possible to calculate the amount of CO2 generated during theses stages.
In average, the Chinese electricity produces 745 g of CO2 per kWh (International Energy Agency 2010).
Results are displayed in Table 28.
Table 28: CO2 emissions from electricity use
Baotou Maoniuping
Required energy (MWh) 6.83 6.67
Emissions of CO2 (tonne) 5.1 5.0
2. Acidification
a. SO2 calculation The sulphur dioxide is produced during the acidic roasting where the following
reaction takes place: 2 H2SO4 2 SO2 + 2 H2O + O2
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Assuming that all the sulphuric acid that is not consumed during the acidic roasting produces sulphur dioxide, it is possible to estimate the quantity of SO2 is rejected. The calculations are exposed in Table 29.
Table 29: Calculation of the SO2 emissions
Baotou Maoniuping
Excess of H2SO4 (kg) 38 640
Quantity of moles 388 6531
SO2 emitted (kg) 25 418
b. Characterisation factor
In order to express both HCl, HF and NH3 in a same unit, the characterisation factor developed by Azapagic was used (Azapagic 2011). It helped to convert these chemicals into SO2eq. The characterisation factors are described in Table 30.
Table 30: Acidification potential characterisation factors (Azapagic 2011)
Chemical Acidification Potential (vs. SO2)
SO2 (sulphur dioxide) 1
HCl (hydrogen chloride) 0.88
HF (hydrogen fluoride) 1.6
NH3 (ammonia) 1.88
Thus, it is possible to express the data calculated in the LCI into SO2eq regarding their acidification potential. The results are exposed in Table 31.
Table 31: Acidification potential of different chemicals
Baotou Maoniuping
HCl discharge (kg) 504 505
HCl acidification potential (kgSO2eq)
444 444
HF discharge (kg) 62 87
HF acidification potential (kgSO2eq)
99 139
NH3/NH4+ discharge (kg) 61 -
95
Baotou Maoniuping
NH3 acidification potential (kgSO2eq)
115 -
3. Eutrophication a. Characterisation factor
In order to express ammonia and phosphate in a same unit, the characterisation factor developed by Azapagic was used (Azapagic 2011). It helped to convert these chemicals into H3PO4eq. The characterisation factors are described in Table 32.
Table 32: Eutrophication potential characterisation factors (Azapagic 2011)
Chemical Acidification Potential (vs. SO2)
Phosphate 1
Ammonia 0.33
Nitrates 0.42
Thus, it is possible to express the data calculated in the LCI into H3PO4eq regarding their eutrophication potential. The results are exposed in Table 33.
Table 33: Eutrophication potential of different chemicals
Baotou Maoniuping
Phosphate discharge (kg) 124 -
Phosphate eutrophication potential (kgH3PO4eq)
124 -
Ammonia discharge (kg) 922 -
Ammonia eutrophication potential (kgH3PO4eq
304 -
4. Radioactive waste generation
a. Radioactive waste slag The radioactivity is calculated from the following formula:
!"#$%"&'$($') = !!"#$% ∗!" (2)!!
!
where:
- Natoms is the number of radioactive atoms - t1/2 is the half life (14.05 billion years for ThO2)
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Calculations are exposed in Table 34.
Table 34: Activity in waste slag
Baotou Maoniuping
Radioactive waste slag discharge 1.4 t 300 kg
Amount of ThO2 in waste slag (kg) 14.2 kg 10 kg
Activity (Bq) 5.1 107 3.6 107
Specific activity (Bq/kg) 3.6 104 1.25 105
b. Radioactive in wastewater Similarly as for the previous section, the quantity of thorium in wastewater was
estimated. The calculations are displayed in Table 35.
Table 35: Activity in wastewater
Baotou Maoniuping
Amount of ThO2 in wastewater (kg) 0.6 0.26
Activity (Bq) 2.1 106 9.3 105
Specific activity (Bq/m3) 2.9 104 -
5. Land use The data are given in Table 15.
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Appendix 9: Toxic chemicals in wastewater
1. Oxalic acid According to Cindy Hurst in a report for the Institute for the Analysis of Global
Security (Hurst 2010): “Oxalic acid is poisonous and potentially fatal if swallowed. It is also corrosive and causes severe irritation and burns to the skin, eyes, and respiratory tract, is harmful if inhaled or absorbed through the skin, and can cause kidney damage.”
2. Ammonium bicarbonates In the same report, Hurst writes that (Hurst 2010):
“The potential health hazards of ammonium bicarbonate include: Irritation to the respiratory tract if inhaled, irritation to the gastrointestinal tract if ingested, redness and pain if it comes in contact with the eyes, and redness, itching, and pain if it comes in contact with the skin.”
3. Ammonium sulphates The company DSM reports that (DSM 2010):
“Ammonium sulphate has a low hazard profile. […] Ammonium sulphate has been tested for several toxicological endpoints (for example, acute toxicity, irritation, repeated dose toxicity). Based on experimental data for analogue substances, no additional adverse health effects are anticipated for the ammonium sulphate. […] Ammonium sulphate has a low bioaccumulating potential. It has been tested for ecotoxicity. Based on these tests there is no need to classify this substance.” 4. Sodium sulphates
According to the International Programme on Chemical Safety of the World Health Organisation (International Programme on Chemical Safety 2000):
“The Committee considered that the results of the published studies in experimental animals do not raise concern about the toxicity of sodium sulfate. The compound has a laxative action, which is the basis for its clinical use. The minor adverse effects reported after use of ingested purgative preparations containing sodium sulfate may not be due to the sodium sulfate itself.”
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Appendix 10: Report on the lake of toxic waste in Baotou (Parry 2011)
“When we finally break through the cordon and climb sand dunes to reach its brim, an apocalyptic sight greets us: a giant, secret toxic dump, made bigger by every wind turbine we build.
The lake instantly assaults your senses. Stand on the black crust for just seconds and your eyes water and a powerful, acrid stench fills your lungs.
For hours after our visit, my stomach lurched and my head throbbed. We were there for only one hour, but those who live in Mr Yan’s village of Dalahai, and other villages around, breathe in the same poison every day.
Retired farmer Su Bairen, 69, who led us to the lake, says it was initially a novelty – a multi-coloured pond set in farmland as early rare earth factories run by the state-owned Baogang group of companies began work in the Sixties.
‘At first it was just a hole in the ground,’ he says. ‘When it dried in the winter and summer, it turned into a black crust and children would play on it. Then one or two of them fell through and drowned in the sludge below. Since then, children have stayed away.’
As more factories sprang up, the banks grew higher, the lake grew larger and the stench and fumes grew more overwhelming.
‘It turned into a mountain that towered over us,’ says Mr Su. ‘Anything we planted just withered, then our animals started to sicken and die.’
People too began to suffer. Dalahai villagers say their teeth began to fall out, their hair turned white at unusually young ages, and they suffered from severe skin and respiratory diseases. Children were born with soft bones and cancer rates rocketed.
Official studies carried out five years ago in Dalahai village confirmed there were unusually high rates of cancer along with high rates of osteoporosis and skin and respiratory diseases. The lake’s radiation levels are ten times higher than in the surrounding countryside, the studies found.
Since then, maybe because of pressure from the companies operating around the lake, which pump out waste 24 hours a day, the results of ongoing radiation and toxicity tests carried out on the lake have been kept secret and officials have refused to publicly acknowledge health risks to nearby villages.”
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