Expert opinion on BAT-associated emission levels (BAT-AELs ... · PDF fileExpert opinion . on . BAT-associated emission levels ... final draft [1] BAT-associated emission levels (BAT

Prof. Dr.-Ing. A. Kather: BAT-AELs for Hg emissions from lignite-fired PC boilers 31.08.2016

1

Expert opinion

on

BAT-associated emission levels (BAT-AELs)

for

mercury emissions to air

from

existing lignite-fired power plants

with pulverised combustion (PC) boilers

in the

LCP BREF review process

Prof. Dr.-Ing. Alfons Kather

Hamburg University of Technology

Institute for Energy Systems

28 July 2016


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Contents

Summary

1 Separate mercury BAT-AELs for plants with FBC and with PC boiler

2 Assessment of Hg emissions of lignite-fired plants with PC boiler reported in the frame of the LCP BREF review

2.1 BAT-AELs for lignite-fired plants with PC boiler derived from LCP BREF review

2.2 Influence of Hg content in the fuel

3 Assessment of Hg emissions of US lignite-fired plants used in the split views of the LCP BREF as evidence of very low Hg emission values

3.1 Inadmissible evidence for lignite-fired Southern Co units

3.2 Contradictory evidence for lignite plant Oak Grove 1

3.3 Emission limit values according to US MATS

3.3.1 Conversion of the US ELV into European concentration values

3.3.2 US 30-day rolling average value as comparative value for the discussion of the European yearly average emission value

4 Proposal for new Hg BAT-AELs for existing lignite-fired power plants with PC boiler


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Summary

The BAT-associated emission levels (BAT-AELs) to air for mercury (Hg) from existing lignite- fired power plants with a total rated thermal input (MWth) ≥ 300 are set in the LCP BREF final draft [1] between < 1 and 7 µg/Nm3 on a yearly average basis. Although the capture mechanism for Hg is quite different in Fluidised Bed Combustion (FBC) and Pulverised Combustion (PC) boilers, the same emission levels are proposed for power plants with FBC and PC boilers. Similar to the BAT-AELs for NOx and SO2 this should be changed and separate BAT-AELs for Hg should be set for power plants with FBC and PC boilers.

According to the document “Review of the best available techniques (BAT) Reference document for large combustion plants (LCP BREF) - Assessment of split view rationales”, section 11.15 [2], CAN Europe explains a BAT-AEL of < 1 μg/Nm3 for Hg emissions of lignite-fired plants (existing and new) on the basis of

- Plant no.18-2V reported in the LCP BREF review This plant is equipped with a bubbling FBC and additionally with a bag filter, a filter technology which none of the lignite-fired PC plants of the LCP BREF review is equipped with. Plant 18-2V therefore displays technology, which by far is not representative for the assessment of Hg emission values of lignite-fired plants with PC boiler.

- Southern Co units in the US This plant is not yet in operation. Furthermore, it is an Integrated Gasification Combined Cycle (IGCC) plant – using a gasification technology, which is also not at all representative for the assessment of Hg emission values for lignite-fired plants with PC boiler.

- Power plant Oak Grove in the US The average emission values during the three months of the third quarter of 2015 were 2.5 µg/Nm3 for unit 1 and 3.1 µg/Nm3 for unit 2 [7]. Therefore, these plants cannot be cited as evidence for Hg values of < 1 μg/Nm3 in lignite-fired plants with PC boiler.

None of these plants provide evidence for a BAT-AEL of < 1 μg/Nm3 for Hg emissions of lignite-fired plants with PC boiler and thus there is no evidence for footnote 2 in table 10.9 of the LCP BREF final draft [1]: “The lower end of the BAT-AEL range can be achieved with specific mercury abatement techniques.”

The US emission limit value (ELV) for lignite-fired plants is at least 5 µg/Nm³. The lowest reported emission value of lignite-fired PC boilers in the LCP BREF review is 2.6 µg/Nm³ for plant 23 V. However the actual continuous Hg measurements in plant 23 V show values of 20 - 25 µg/Nm3. Therefore, there is not one lignite-fired plant with PC boiler in the world with yearly average Hg emissions of < 1 µg/Nm³.

In summary it is not understandable how the EIPPCB could derive a BAT-AEL of < 1 μg/Nm3 at the lower end of the range for Hg emissions of existing lignite-fired plants with PC boiler from the LCP BREF review or from the information about US plants.


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Taking into account

• that the converted US emission limit values for lignite-fired power plants are between 5.0 and 5.6 µg/Nm³,

• that none of the lignite-fired power plants with PC boiler in the LCP BREF review has reported values of less than approximately 3 µg/Nm³,

• that the three lowest values of approximately 3 µg/Nm³ in the LCP BREF review are based on very large uncertanties,

• that only the best performing lignite-fired plants with PC boiler were reported by many European countries,

• that there is a very large uncertainty for the continuous measurement of Hg (up to +/- 6 µg/Nm3 for example according to 13. BImSchV in Germany), and

• that there are very large spreads in Hg content of the different lignites

the range for the new BAT-AEL for Hg emissions of existing lignite-fired power plants with PC boilers should be set between 5 and 9 µg/Nm³ if the Hg content of the lignite is less than 0.22 mg/kg (dry basis). Higher mercury contents in the fuel than 0.22 mg/kg have to be taken into account within the approval process of the affected plant.


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1 Separate mercury BAT-AELs for plants with FBC and with PC boiler

The capture mechanisms for NOx and SO2 are quite different in Fluidised Bed Combustion (FBC) and Pulverised Combustion (PC) boilers. Therefore, in the LCP BREF final draft [1] BAT-associated emission levels (BAT-AELs) for NOx (in table 10.3) and SO2 (in table 10.5) are divided into AELs for plants with FBC boilers and with PC boilers.

As with NOx and SO2 control, Hg control is quite different in FBC and PF boilers. Similar to the capture of Hg with activated carbon, Hg is absorbed in FBC boilers due to the large carbon content in the bed material of the combustor. This leads to much lower Hg emissions in FBC boilers than in PC boilers. This can be seen in Figure 1 where the reported Hg emissions of the LCP BREF review for lignite-fired plants with FBC boiler are marked with ellipses.

Figure 1 Hg emissions of lignite-fired plants according to LCP BREF review; plants with FBC are marked with ellipses [3]

This kind of Hg capture mechanism cannot be used or retrofitted in PC boilers, so the control of Hg has to be achieved with other technologies in PC boilers. For this reason, separate Hg BAT-AELs for plants with FBC and PC boilers should be decided upon in LCP BREF.


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At this place it should be mentioned that in Figure 5.31 of the final draft of the LCP BREF document [1] the four lignite-fired power plants with highest Hg emissions in Figure 1 were eliminated, although these are the only plants equipped with continuous measurement. Furthermore, the emission values of the power plants 18-1V and 18-2V have been eliminated for the derivation of BAT-AELs for the pollutant SO2 in Figure 5.33 of the final draft of the LCP BREF document. It is not understandable why, for each pollutant, different plants out of the data collection were chosen as basis for the derivations of BAT-AELs. A reasonable procedure for the derivation of BAT-AELs would take into account the whole number of installations with comparable techniques reported during the data collection.


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2 Assessment of Hg emissions of lignite-fired plants with PC boiler reported in the frame of the LCP BREF review

In section 11.15 of the document “Review of the best available techniques (BAT) Reference document for large combustion plants (LCP BREF) - Assessment of split view rationales” [2] CAN Europe explains a BAT-AEL of < 1 μg/Nm³ for Hg emissions with the following argument:

“Collected data show several existing coal and lignite power plants achieving yearly averages below 1 μg/Nm3 (see Coal and/or lignite combustion – mercury emissions document, tables 1 and 2, plants 211V, 1005V, 77V, 156V, 462V, 267V, 268V, 662V, 224V, 286V, 689, 81V, 685V, 547V, 379V, 253V, 18-2V).”

In this list of plants there is only one lignite-fired plant – 18-2V. This plant is equipped with a bubbling FBC and therefore with an advantageous Hg capture mechanism due to the high carbon content in the bed material. Additionally, the plant is equipped with a bag filter, which is much more favourable for Hg capture than an ESP. But none of the lignite-fired plants with PC boiler of the LCP BREF review is equipped with this filter technology. Plant 18-2V is therefore a technology which by far is not representative for the assessment of Hg emission values of lignite-fired plants with PC boiler. In summary it can be stated that the plant no. 18-2V as an argument for a BAT-AEL of < 1 μg/Nm³ for lignite-fired plants with PC boiler is not valid.

Figure 2 Hg emissions of lignite-fired plants according to LCP BREF review; for plants with a total rated thermal input (MWth) ≥ 300; without plants with FBC boilers [3]


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After removing the reported Hg emission values of the plants with FBC boilers and plants with a total rated thermal input of less than 300 MWth in Figure 1, the reported emission values of the lignite-fired plants with PC boiler are shown in Figure 2. There are only three plants with reported Hg emission values of around 3 µg/Nm³. Two of these plants (130 VC and 137 VC) have reported estimated Hg emission values without addition of measurement uncertainties as requested by IPPCB. The third plant (23 V) has reported an Hg concentration which is based on one measurement per year. From the EXCEL sheet with the data collection of plant 23 V [4] during the LCP BREF review it can be seen that this plant uses lignite, which has the highest reported amount of Hg (of 0.225 mg/kg dry basis) among the lignite-fired power plants in the data collection. This high Hg content in the fuel results in a high Hg concentration in the raw flue gas of approximately 60 µg/Nm3. The reported emission value of 2.6 µg/Nm3 would therefore require an Hg capture rate of more than 95 %. Without any additional specific mercury abatement techniques this is an impossible value and should be scrutinised. To clarify this contradiction the author of this expert opinion contacted the operator of plant 23 V and got the following information:

“I checked the data on 23-V power plant with following result. The measurements have so far been conducted once a year and the results vary significantly. As you can see below the reference year 2011 is with the lowest measured concentration in last 5 years despite the rather stable content of mercury in fuel.

23 V - Hg measurement 2011 2012 2013 2014 2015

Hg in emissions [µg/m3] 2,6 3,8 7,1 9,5 6,02

Hg in fuel [mg/kg] 0,210 0,205 0,205 0,178 0,182

These days the continuous measurement of the 23-V emissions has been tested. The still not validated results do show significant deviation from historic values – they are in the level of about 20-25 micrograms/m3.”

The plant operator had already pointed out these uncertainties in section 11.18.3 of the document “Review of the best available techniques (BAT) Reference document for large combustion plants (LCP BREF) - Assessment of split view rationales” [2]:

“There is an enormous variability of the Hg in emissions due to natural conditions (Hg and halogen content in fuel) and abatement parameters within the span of the last years across the portfolio of the combustion plants in CZ and Euroheat & Power members' countries.”

This shows that the collected data for the lignite-fired plants with PC boiler in the LCP BREF review is very uncertain. Even if this uncertain data is taken into account, all lignite-fired plants with PC boiler are far above the value of 1 µg/Nm³.


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2.1 BAT-AELs for lignite-fired plants with PC boiler derived from LCP BREF review

There is no strict regulation to derive BAT-AELs. Schönberger, who was working for the European IPPC Bureau, has shown how to define BAT-AELs in his paper “Integrated pollution prevention and control in large industrial installations on the basis of best available techniques – The Sevilla Process” [5]. Following this philosophy the best third of all installations, defined as the best performing installations, should be taken as potential range to conclude BAT (see Figure 3).

Figure 3 Potential range to conclude on BAT as shown in [5]

Applying this philosophy to the reported plants of the LCP BREF review for lignite-fired plants with PC boiler would lead to a BAT-AEL of 7 µg/Nm3, as shown in Figure 4. The author of this expert opinion was involved in the selection of the German reference plants for the data collection in 2011-2013 to determine BAT. From this experience he knows that at the beginning of this selection only the best plants were chosen to be reported to the LCP BREF process. Likely, other countries followed this procedure during their selection process so that finally many countries reported only the best performing installations while not so well performing plants were left out. Maybe this is the reason why only three non-German lignite-fired plants with PC boiler are reported for the data collection (see Figure 1). This would mean that the non-reported lignite-fired plants from Poland, Greece, Czech Republic, Hungary etc. show higher Hg emission concentrations. This might be the reason why EURACOAL proposes an upper end of Hg BAT-AEL range of 20 µg/Nm3 in their split views. These reflections show that there are good arguments to shift the ratio of 1/3 in Figure 4 to a higher value.


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Figure 4 BAT-AEL for lignite-fired plants with PC boiler when applying the 1/3 philosophy as definition for BAT

If only the plant 23V would be corrected to the values determined during continuous measurement of around 20 µg/Nm3, the derived BAT-AEL value would be 9 µg/Nm3

(Figure 4b).

Figure 4b BAT-AEL for lignite-fired plants with PC boiler when applying the 1/3 philosophy as definition for BAT and adjustment of plant 23V


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2.2 Influence of Hg content in the fuel

According to table 5.1 in [1] the Hg content on dry basis of lignite ranges from 0.03 mg/kg to 0.22 mg/kg. The highest value of 0.22 mg/kg leads to Hg concentrations in the raw flue gas of around 60 µg/Nm3. To reach an Hg emission value of 1 µg/Nm3 it would be necessary to achieve a capture rate of more than 98 %, which is nearly impossible. With a technically reasonable capture rate of 80 %, the achievable emission value would be 12 µg/Nm3.

Taking into account

- the very large uncertainness of the three lowest reported values in Figure 4, - that only the best lignite-fired plants with PC boiler were reported by many countries, - that there is a very large uncertainty for the continuous measurement of Hg (up to

+/- 6 µg/Nm3 for example according to 13. BImSchV in Germany), and - that there is very large spread in Hg content of the different lignites

an upper end of the BAT-AEL range of 9 µg/Nm3 seems to be reasonable if the Hg content of the lignite is less than 0.22 mg/kg (dry basis).


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3 Assessment of Hg emissions of US lignite-fired plants used in the split views of the LCP BREF as evidence of very low Hg emission values

In section 11.15 of the document “Review of the best available techniques (BAT) Reference document for large combustion plants (LCP BREF) - Assessment of split views rationales” [2] CAN Europe explains a BAT-AEL of < 1 μg/Nm3 with the further argument:

“Evidence provided by CAN Europe / Greenpeace and EEB to the TWG showing emission values below 1 μg/Nm3 in coal and lignite power plants in the USA (see “MATS proposal reconsideration MACT floor spreadsheet - non-low rank virgin coal Hg”, “MATS proposal reconsideration MACT floor spreadsheet - low rank virgin coal Hg” and “MACT Floor Analysis-Coal HG” and “Best performance examples for SO2, NOX, PM & Hg control in coal and lignite-fired power plants”, in particular lignite plants Oak Grove 1 and Southern Co units).”

As evidence for lignite-fired power plants, the “lignite plants Oak Grove 1 and Southern Co units” are mentioned by CAN Europe.

3.1 Inadmissible evidence for lignite-fired Southern Co units

The only “lignite-fired Southern Co unit”, which can be found on the internet and in literature is the Kemper Project which is scheduled to go into operation in the third quarter of 2016. In http://www.bizjournals.com/atlanta/news/2016/04/04/southern-co-s-kemper-power-plant-costs-rise-yet.html can be read:

“During March 2016, Mississippi Power has continued to conduct repairs and modifications to the refractory lining inside each of the gasifiers and to inspect and evaluate the need for additional refractory work, which could impact the projected in-service date and/or the related cost estimate for the Kemper IGCC,” the company said in the filing. “Mississippi Power’s previously disclosed projected in-service date for the Kemper IGCC is during the third quarter 2016.”

Thus, one of the two US plants for very low Hg emission values mentioned by CAN Europe has never been in operation. Furthermore the Kemper plant is an IGCC plant – a technology which is not at all relevant to the assessment of Hg concentrations of lignite-fired plants with PC boiler. Therefore, the question has to be raised how a plant with a totally different technology, which is not even in operation until today, can be used as evidence for an Hg BAT-AEL of < 1 μg/Nm3 for lignite-fired power plants with PC boiler.

3.2 Contradictory evidence for lignite plant Oak Grove 1

At

http://www.powermag.com/luminants-oak-grove-power-plant-earns-powers-highest-honor/

the following statement can be found:

http://www.bizjournals.com/atlanta/news/2016/04/04/southern-co-s-kemper-power-plant-costs-rise-yet.html

http://www.bizjournals.com/atlanta/news/2016/04/04/southern-co-s-kemper-power-plant-costs-rise-yet.html

http://www.bizjournals.com/profiles/company/us/ms/gulfport/mississippi_power_co/2764788

http://www.powermag.com/luminants-oak-grove-power-plant-earns-powers-highest-honor/


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“Luminant used remnants of the ill-fated Twin Oaks and Forest Grove plants (which were mothballed more than 30 years ago) to build the new two-unit 1,600-MW Oak Grove Plant. Though outfitted with equipment from those old plants, Oak Grove also sports an array of modern air quality control equipment and is the nation’s first 100% lignite-fired plant to adopt selective catalytic reduction for NOx control and activated carbon sorbent injection technology to remove mercury.”

The one hour average Hg emission values in lb/TBtu of both units are shown in Figure 5. The average emission values during the third quarter 2015 are 2.5 µg/Nm3 (2.0 lb/TBtu) for unit 1 and 3.1 µg/Nm3 (2.5 lb/TBtu) for unit 2. These plants are far away from having Hg concentrations of < 1 µg/Nm3.

Figure 5 Hourly average Hg emission values (HAV) of the Oak Grove units [7]

3.3 Emission limit values according to US MATS

As the emission limit values (ELV) defined in the US MATS and also Hg emission values of US plants are often discussed, a proper conversion of the US MATS Hg ELV into European concentration values will be shown in the following.


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3.3.1 Conversion of the US ELV into European concentration values

Figure 6 shows the conversion of US 30-day rolling average emission limit values for Hg into European concentration values for different gross electrical efficiencies. This conversion has often been performed in the wrong manner by multiple authors in the past. The correct conversion was published in [6] in December 2015. From Figure 6, it can be seen that the lowest Hg emission limit value for lignite-fired plants in the US is 5 µg/Nm3, or 4 lb/TBtu. The US emission limit value that would apply to modern German lignite-fired power plants - built in the last 15 years with a gross electrical efficiency of 46 % - is 0.013 lb/GWh, which corresponds to 5.6 µg/Nm3. Based on these US emission limit values, no US lignite-fired plant is operated with Hg concentrations of < 1 µg/Nm3.

Figure 6 US 30-day rolling average emission limit values for Hg converted into European concentration values, HHV = higher heating value, LHV = lower heating value, fuel quality according to M-19 [8]


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3.3.2 US 30-day rolling average value as comparative value for the discussion of the European yearly average emission value

To show that the US 30-day rolling average value can be taken as a comparative value for the discussion of the European yearly average emission value, the emission values of the two units of the lignite-fired power plant Coal Creek are shown in Figure 7. Beside the hourly average values (measured) the 30-day rolling average values (calculated) are shown. It can be seen that both units are operated in a way that the common 30-day rolling average value (red dots) is just below the permitted emission limit value of 4 lb/TBtu, such that the difference between the 30-day rolling average values and the yearly average value would be very small.

The reason for the small difference between 30-day rolling and yearly average values is that the technology, which has to be installed to meet such a low ELV, can be adjusted relatively exactly to meet the ELV. In summary, it can be stated that the US 30-day rolling average ELV can be taken as a comparative value for the discussion of the European yearly average ELV.

Figure 7 Hourly average values (HAV) and 30-day rolling average values of the two 605 MWel units of the power plant Coal Creek after retrofitting a pulverized activated carbon plant; hourly average values according to EPA‑Air Market Program Data [7]


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4 Proposal for new Hg BAT-AELs for existing lignite-fired power plants with PC boiler

Taking into account

• that the converted US emission limit values for lignite-fired power plants are between 5.0 and 5.6 µg/Nm³,

• that none of the lignite-fired power plants with PC boiler in the LCP BREF review has reported values of less than approximately 3 µg/Nm³,

• that the three lowest values of approximately 3 µg/Nm³ in the LCP BREF review are based on very large uncertainties,

• that only the best performing lignite-fired plants with PC boiler were reported by many European countries,

• that there is a very large uncertainty for the continuous measurement of Hg (up to +/- 6 µg/Nm3 for example according to 13. BImSchV in Germany), and

• that there are very large spreads in Hg content of the different lignites

the range for the new mercury BAT-AEL for existing lignite-fired power plants with PC boiler should be set between 5 and 9 µg/Nm³.

As the Hg content in the lignite is the key parameter for the Hg concentration in the raw flue gas and thus also for the Hg emissions to air, the proposed BAT-AELs range of 5 to 9 µg/Nm3 is based on the input data gained within the LCP BREF revision process with Hg contents of up to 0.22 mg/kg (dry basis). Higher mercury contents in the fuel than 0.22 mg/kg have to be taken into account within the approval process of the affected plant.

(Prof. Dr.-Ing. Alfons Kather)

References

[1] Best Available Techniques (BAT) Reference Document for Large Combustion Plants; Final draft (June 2016)

[2] Review of the best available techniques (BAT) Reference document for large combustion plants (LCP BREF) - Assessment of split view rationales; 22.06.2016


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[3] LCP BREF review – Data collection carried out in 2011 – 2012 at European levels. Coal and/or lignite combustion Hg emission

[4] Questionnaire for collecting plant-specific data for the review of the BAT Reference Document (BREF) on Large Combustion Plants (LCP) 23 V, March 2012

[5] Schoenberger, H: Integrated pollution prevention and control in large industrial installations on the basis of best available techniques – The Sevilla Process; Journal of Cleaner Production 17 (2009) 1526–1529

[6] Kather, A., Klostermann, M.: Grenzwerte für Quecksilberemissionen aus Kohlekraftwerken; VGB Powertech 12-2015

[7] United States Environmental Protection Agency - Air Markets Program Data - Mercury and Air Toxics Standards (MATS), accessed on 25-05-2016, https://ampd.epa.gov/ampd/

[8] CFR Title 40 -- Protection of Environment; Revised as of July 1, 1991, CHAPTER I -- ENVIRONMENTAL PROTECTION AGENCY, SUBCHAPTER C -- AIR PROGRAMS PART 60 -- STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES § 60. Appendix A to Part 60 -- Test Methods [PART I OF VII] 40 CFR 60. Appendix A to Part 60 Method 19

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Expert opinion on BAT-associated emission levels (BAT-AELs ... · PDF fileExpert opinion . on . BAT-associated emission levels ... final draft [1] BAT-associated emission levels (BAT