Recommendation of Process Routes for the Production of Potash

University of Birmingham

Department of Chemical Engineering

ACADEMIC YEAR 2015 / 2016

Design Project Task 01

RECOMMENDATION OF PROCESS ROUTES FOR THE PRODUCTION OF

POTASH

Student Name : Mohamad Daniel Bin Yaacob Student ID : 1615568 Module Title : Design Project Module Code : 17133 Lecturer : Dr. Phillip Robbins Submission Date : 6th October 2015

Design Project Task 01 Prepared By: Mohamad Daniel bin Yaacob Student ID: 1615568

1

INTRODUCTION Potash represents a wide variety of mined and manufactured salts, all of which contain the element potassium in a water soluble form. Within the industry, the term potash is used to refer to potassium chloride, as well as potassium sulphate, potassium nitrate and potassium oxide. Neuendorf, Mehl and Jackson (2005) noted that potash, ranging up to 90%, is principally used within the agriculture sector as a fertilizer or plant nutrient, as it is a source of soluble potassium. Canpotex (2015) elaborated that potassium is one of the three primary plant nutrients required for sustainable plant growth and maturation, with the other two being fixed nitrogen and soluble phosphorus. Having no known substitutes, potash essentially helps to improve crop yields, in addition to adding flavour, colour, and texture. The remainder of global potash capacity is used for industrial purposes, such as the manufacture of glass, textiles, pharmaceuticals and even food processing. SOURCES OF POTASH Although potassium is one of the most common elements on Earth, its concentration within the Earths crust is relatively low and it only accumulates on certain minerals and rock salts, forming rocks. Garrett (1996) specified that even though various minerals contain traces of potassium, sylvinite and carnallite are the two with the highest concentration and is most commonly mined for potash processing. The formation of these mineral ores are due to the displacement of crustal blocks millions of years ago, engulfing dried up lagoons with remnants of crystallized salt. As potash is found in various ores and salts, mining differs in many aspects and involves several types of unique mining techniques. In general, there are currently three main techniques for the development of potash deposits. Conventional underground mining accounts for nearly 80% of global potash capacity, while 8% is produced by underground water dissolution of salt deposits through leaching. The remaining 12% is obtained by harvesting natural brines from potassium rich water bodies such as salt lakes, typically using solar evaporation. The International Plant Nutrition Institute (2010) described the conventional mining method as being done through the use of vertical shafts, drilled to the depths of the potash ore deposits. Lifts are installed to provide access for equipment, workers, and the extraction of the ore. Ore veins could be extracted through several methods, with each method adapted to the specific geologic formation of the area. Some of these methods include continuous machine mining and the blast method. Underground leaching is done by injection of heated brine (a salt and water solution), through holes drilled from the surface to the bottom of the mineral bed. The resulting potash-rich brine is pumped to surface ponds or crystallizers for extraction and further processing. This method is used in areas where the mining process is impossible due to mountains and geological conditions. As noted from Infopotash (2015), sulphate salts are extracted through the evaporation of natural brines, such as the Dead Sea, the Caspian Sea, or the Great Salt Lake in the United States. Special artificial tanks are dug close to the sources of natural brines and when the water in these tanks evaporates, the remaining salt present on the surface is then collected with earthmovers. The resulting raw material undergoes mechanical cleaning and is sent for further processing.


2

PRODUCTION OF POTASH Sylvinite is a mixture of potassium chloride (KCl) and sodium chloride (NaCl) crystals, also known as sylvite and halite, and is the easiest to process amongst the other potash ores. As such, it is mined and refined in the greatest quantities to extract KCl. The current report shall focus on the treatment and processing procedures for sylvinite ores. The International Institute of Environment and Development (2002) indicates that generally, the processes used to treat potash ores are dependent on the characteristics and composition of the ore and global market requirements. Otherwise, the processes follow a certain series of steps, which are crushing and grinding; desliming; separation; debrining and drying; and compaction. CRUSHING AND GRINDING In crushing and grinding, the ores are fed into a system of rod mills and screens to liberate the different minerals within the ore from each other. This step is done to reduce the ore into smaller uniform sizes for ease of further enrichment, as well as to give adequate yields and purity of the final product. Potashcorp (2013) noted that varying degrees of clay and impurities are present on the surface of the ores, which may come as a deciding factor on the production process for potash. As such, clay particles present on the ores are separated using agitation machines, while smaller particles of clay and impurities are removed using an additional system of size separators. DESLIMING The desliming stage is considered critical, as a virtually slime-free product is necessary to feed the potash separation stage, in order to minimize reagent costs and to improve potash recovery. After crushing and grinding, the potash ores are rinsed and fed into agitation tanks or scrubbers that are filled with saturated brine solution to further remove insoluble minerals that my still be attached to the ore. Perucca (2003) suggested that a secondary desliming stage may also be introduced to improve the efficiency of the process. The secondary stage can be accomplished with the aid of specialized equipment such as hydro-separators, cyclones, and thickeners. While desliming may be effective for ores containing about 4% insoluble slimes or less, Parekh and Miller (1999) depicted that ores containing large quantities requires an alternative method to remove the impurities from the ore. These methods include hot leaching or even flotation. SEPARATION o HALURGICAL SEPARATION

The halurgical method is used for treatment of sylvinite ores, as well for solutions obtained by underground dissolution and for natural reservoirs with high mineral content. Tarantseva, Firsova, and Palicheva (2015) described that the process consists of extracting soluble substance from the sylvinite ore by means of a solvent and is based on the varying degrees of solubility of KCl and NaCl in water at different temperatures. At normal temperatures the solubility of potassium and sodium chlorides is almost the same. As temperatures increase, the solubility of sodium chloride is almost unchanged, while the solubility of potassium chloride increases dramatically. During cooling of saturated solution, KCl crystallizes from the solution and is sent to the next stage of process.


3

o FLOTATION SEPARATION

Belaruskali (2015) described that the processing of ore by flotation is based on the difference in surface properties between minerals through the addition of reagents to selectively separate the desired mineral. During flotation, process reagents (long-chained amines and a frother) are added to the crushed and deslimed mixture, which is then passed to an agitation and aerated flotation cell where compressed air bubbles carries the potash to the surface. The surface minerals are then mechanically skimmed from the solution, while the insoluble salt slurry on the bottom is discarded.

There are also several types of advancing and upcoming flotation techniques within the ore processing industry, with some of the well-known methods being film flotation, oil flotation, and foam flotation; the latter being the most widely used within the global potash industry.

o CRYSTALLIZATION SEPARATION

Typically used in conjunction with solution mining, the crystallization process is based on the fact that KCl has a higher crystallization temperature compared to NaCl. The crushed and deslimed ore is mixed with hot water while agitating the solution at high temperatures to selectively dissolve sylvite from halite. NaCl is then cooled to a temperature where KCl crystallizes, thus separating itself from the NaCl that remains in the solution in the brine. The KCl is then separated from the brine and the brine, consisting of undissolved NaCl and insolubles are later removed in clarifiers. Elementals Minerals Limited (2015) noted that crystallization is also used as a side process to recover potash fines generated during crushing and scrubbing. These are usually too fine to be efficiently compacted and are therefore upgraded by crystallization to a standard size material, amenable to be sold as white product or to be processed further and compacted as a premium product.

o ELECTROSTATIC SEPARATION

Electrostatic separation is a dry process in which the minerals are separated using their different electrical conductivities. Bulatovic (2015) explains that the process involves preheating the potash ore to about 400 500 C, followed by utilizing an electrostatic generator, where it provides static charge to the minerals that passes through the generator. In this case, the non-conductive KCl particles are separated from charged NaCl particles. Although Kogel et al. (2006) states that electrostatic separation has proved to be a low cost, high volume process compared to conventional separation methods, Bulatovic argues that the method has only been tested within the pilot plant scale and has yet been introduced to the plant scale.


4

o HEAVY MEDIA SEPARATION

Heavy media separation relies heavily on the difference in specific gravity between sylvite and halite to selectively float and remove the lighter sylvite particles. Finely ground magnetite is added to the brine saturated with KCl and NaCl and is recovered from the rinse solution through magnetic separators. Harrison (1972) suggested that the efficiency of the magnetic separation step could be improved by separating the wash solution in a hydrocyclone for several stages, where the contaminant free solution is treated conventionally in magnetic separators and the contaminants are recycled to the rinse screens or other suitable separation devices.

The United Nations Environment Programme (2001) reports that although extensively examined, heavy media separation has limited commercial applications. Furthermore, maintenance costs are higher compared to conventional methods due to abrasive properties of magnetite.

DEBRINING AND DRYING After the separation stage, the potash concentrate is transferred to screen bowl centrifuges, which separates potash from the brine. The damp potash is then moved to either rotary or fluidized bed dryers to remove any excess moisture. The resulting dry mixture contains various sizes that are separated by huge mesh screens into different grade potash products based on the latest global market demand. COMPACTION The compaction stage is a common and essential stage within the production process of potash with the capability to increase the mean size distribution of dry, particulate KCl. The potash is sized and separated through a system of oscillating screens, in effect shifting through the different sized crystals. Any undersized crystals are pressed together then crushed and screened again. This compaction process is repeated until the potash granules achieve a constant size. Table 1.0: Comparisons between Separation Processes for the Production of Potash

Separation Process

Component Recovery

Capital Cost Energy Intensity

Final Product Grading

Additional Remark

Halurgic 95 98% High High Standard (White) Fine

Equipment corrosion; frequent maintenance required

Flotation 85 87%

Low Low Standard (Pink) Granular

Larger insoluble particles remain with product; decreasing purity

Crystallization 62.5% High High Coarse Granular

Generally utilized as supplementary stage for processes

Electrostatic

- Low High Standard (White) Granular

Further research required for plant scale implementation

Heavy - Media

50% High Low Coarse Granular

Equipment wear and tear; more frequent maintenance required

Sources: United Nations Environment Programme (2001); Kogel et al (2006); Garrett (1996); Perucca (2003); Belaruskali (2015); Uralkali (2015) APPENDIX A illustrates the simplified process flow diagrams for different separation methods for the production of potash ores.


5

CONCLUSION Currently, world potash production is dominated by ten major companies, with some of the major players being Uralkali, Potash Corporation (PotashCorp), and Belaruskali. These companies have been heavily involved within the potash market for decades and has since grown to be well established organizations; having access to low cost long-life deposits and processing technologies. As such, entry into the potash business is challenging because quality potash ore deposits are very limited and plant development duration is estimated to take a minimum of five to seven years. However, the growing global demand for potash, long term pricing stability, and the high supply visibility makes potash a strong investment strategy across the fertilizer industry. In terms of processing technologies for potash ores, the treatment of sylvinite ores has not changed much over the years. The majority of new technology present today consists of improvements on established classical process methods. Nonetheless, the flotation separation method proves to be the most widely used across the potash processing industry. To increase the efficiency of the overall process and to achieve high pure component recovery, flotation is supplemented with several other separation processes such as crystallization or electrostatic separation.


6

APPENDIX A - Simplified process flow diagrams for different separation methods for the production of potash ores. x Flotation Separation x Halurgical Separation with Crystallization Supplement Source: Uralkali. (2015). Investor Presentation: Maximising Global Opportunity.


7

REFERENCES [1] Belaruskali (2015) Processing of Potash Ore. [Online] Retrieved 3 October 2015, from http://www.kali.by/en/production/technology/enrichment_technology/ [2] Bulatovic, S. (2015) Handbook of Flotation Reagents: Chemistry, Theory and Practice: Volume 3: Flotation of Industrial Minerals. Vol. 3, 1st ed. (p. 160). Elsevier. [Online] Retrieved from https://books.google.co.uk/books?isbn=0444530835 [3] Canpotex.com (2015) Products. [Online] Retrieved 1 October 2015, from http://www.canpotex.com/what-we-do/products [4] Elementals Minerals Limited (2015) About Potash. [Online] Retrieved 3 October 2015, from http://www.elementalminerals.com/Projects/Potash [5] Garrett, D. (1996) Potash: Deposits, Processing, Properties and Uses. 1st ed. (p. 212). London: Chapman & Hall. [Online] Retrieved from https://books.google.co.uk/books?isbn=9400915454 [6] Harrison, M. (1972) Method for Treatment of Heavy Media. [Online] Retrieved 3 October 2015, from https://www.google.com/patents/US3638791 [7] Infopotash.com (2015) How Potash is Mined Today. [Online] Retrieved 1 October 2015, from http://infopotash.com/en/where-potash-comes-from/how-potash-is-produced-nowadays/ [8] Infopotash.com (2015) How is Potash Processed. [Online] Retrieved 1 October 2015, from http://infopotash.com/en/where-potash-comes-from/production/chemical-enrichment/ [9] International Institute of Environment and Development (2002) Potash Case Study (p. 8 - 9). [Online] Retrieved from http://pubs.iied.org/pdfs/G00557.pdf [10] International Plant Nutrition Institute (2010) Potassium Fertilizer Production and Technology 1st ed. (p. 11 - 14). Georgia, USA. [Online] Retrieved from http://www.ipni.net [11] Jasinski, S.M. (2015) Potash - Mineral Commodity Summaries (p. 122 - 123). United States Geological Survey. [Online] Retrieved from http://minerals.usgs.gov/minerals/pubs/commodity/potash/ [12] Kogel, J., Trivedi, N., Barker, J., & Krukowski, S. (2006) Industrial Minerals & Rocks: Commodities, Markets, and Uses. 7th ed. (p. 735 - 736). Littleton, Colorado, USA: Society for Mining, Metallurgy, and Exploration, Inc. [Online] Retrieved from https://books.google.co.uk/books?isbn=0873352335 [13] Neuendorf, K., Mehl, J., & Jackson, J. (2005) Glossary of geology. 5th ed. (p. 799). Alexandria, Va.: American Geological Institute.


8

[14] Parekh, B., & Miller, J. (1999) Advances in flotation technology. Littleton, CO: Society for Mining, Metallurgy, and Exploration. [Online] Retrieved 1 October 2015, from https://books.google.co.uk/books?isbn=0873351843 [15] Perucca, C. F. (2003) Potash Processing in Saskatchewan A Review of Process Technologies. CIM Bulletin. [Online] Retrieved 2 October 2015, from http://technology.infomine.com/ [16] Potashcorp (2015) PotashCorp Video Tour. [Online] Retrieved 1 October 2015, from http://minetour.potashcorp.com/ [17] Potashcorp (2013) The Potash Journey. Retrieved 1 October 2015, from http://potashcorp.com/library [18] Strathdee, G., Haryett, C., Douglas, C., Senior, M., & Mitchell, J. (1982) The Processing of Potash Ore by PCS. Saskatchewan, Canada: Potash Corporation of Saskatchewan. [Online] Retrieved from https://ttutm.files.wordpress.com/2013/12/processing-of-potash-ore.pdf [19] Tarantseva, K., Firsova, O., & Palicheva, A. (2015) Study of Equipment Corrosion Resistance in the Production of Potash by a Halurgical Method. Chem Petrol Eng, 51(1-2), 49-53. http://dx.doi.org/10.1007/s10556-015-9997-z [20] Tippin, R.B. (1999) Silicate Mineral and Potash Flotation (p. 11). Colorado: Minerals Research Laboratory. [Online] Retrieved from http://portal.ncdenr.org/web/lr/mrl [21] United Nations Environment Programme (2001) Environmental Aspects of Phosphate and Potash Mining 1st ed. (p. 12 -13). Paris: United Nations Publication. [Online] Retrieved 3 October 2015, from https://www.elaw.org/ [22] Uralkali. (2015). Investor Presentation: Maximising Global Opportunity. [Online] Retrieved 3 October 2015, from http://www.uralkali.com/investors/presentations/ [23] Uralkali. (2015). Potash Production Methods. [Online] Retrieved 3 October 2015, from http://www.uralkali.com/buyers/production/methods/

Documents

Recommendation of Process Routes for the Production of Potash