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Title: EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS

Abstract

CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), evaluated the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)-wet flue gas desulfurization (FGD) combination or a spray dyer absorber-fabric filter (SDA-FF) combination. In this program CONSOL determined mercury speciation and removal at 10 bituminous coal-fired facilities; at four of these facilities, additional tests were performed on units without SCR, or with the existing SCR bypassed. This project final report summarizes the results and discusses the findings of the body of work as a whole. Eleven Topical Reports were issued (prior to this report) that describe in great detail the sampling results at each of the ten power plants individually. The results showed that the SCR-FGD combination removed a substantial fraction of mercury from flue gas. The coal-to-stack mercury removals ranged from 65% to 97% for the units with SCR and from 53% to 87% for the units without SCR. There was no indication that any type of FGD system was more effective at mercury removal than others. The coal-to-stack mercury removalmore » and the removal in the wet scrubber were both negatively correlated with the elemental mercury content of the flue gas and positively correlated with the scrubber liquid chloride concentration. The coal chlorine content was not a statistically significant factor in either case. Mercury removal in the ESP was positively correlated with the fly ash carbon content and negatively correlated with the flue gas temperature. At most of the units, a substantial fraction (>35%) of the flue gas mercury was in the elemental form at the boiler economizer outlet. After passing through the SCR-air heater combination very little of the total mercury (<10%) remained in the elemental form in the flue gas; this was true for all SCR catalyst types and sources. Although chlorine has been suggested as a factor affecting the mercury speciation in flue gas, coal chlorine was not a statistically significant factor affecting mercury speciation at the economizer exit or at the air heater exit. The only statistically significant factors were the coal ash CaO content and the fly ash carbon content; the fraction of mercury in the elemental form at the economizer exit was positively correlated with both factors. In a direct comparison at four SCR-equipped units vs. similar units at the same sites without SCR (or with the SCR bypassed), the elemental mercury fractions (measured at the ESP outlet) were lower, and the coal-to-stack mercury removals were higher, when the SCR was present and operating. The average coal-to-stack mercury removal at the four units without an operating SCR was 72%, whereas the average removal at the same sites with operating SCRs was 88%. The unit mercury mass balance (a gauge of the overall quality of the tests) at all of the units ranged from 81% to 113%, which were within our QA/QC criterion of 80-120%.« less

Authors:
Publication Date:
Research Org.:
Consol Energy Inc
Sponsoring Org.:
USDOE
OSTI Identifier:
893601
DOE Contract Number:
FC26-02NT41589
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; AIR HEATERS; BOILERS; CARBON; CATALYSTS; CHLORIDES; CHLORINE; COAL; DESULFURIZATION; ECONOMIZERS; ELECTROSTATIC PRECIPITATORS; FLUE GAS; FLY ASH; HEATERS; MASS BALANCE; MERCURY; POWER PLANTS; REMOVAL; SAMPLING; SCRUBBERS; SELECTIVE CATALYTIC REDUCTION

Citation Formats

J.A. Withum. EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS. United States: N. p., 2006. Web. doi:10.2172/893601.
J.A. Withum. EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS. United States. doi:10.2172/893601.
J.A. Withum. Tue . "EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS". United States. doi:10.2172/893601. https://www.osti.gov/servlets/purl/893601.
@article{osti_893601,
title = {EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS},
author = {J.A. Withum},
abstractNote = {CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), evaluated the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)-wet flue gas desulfurization (FGD) combination or a spray dyer absorber-fabric filter (SDA-FF) combination. In this program CONSOL determined mercury speciation and removal at 10 bituminous coal-fired facilities; at four of these facilities, additional tests were performed on units without SCR, or with the existing SCR bypassed. This project final report summarizes the results and discusses the findings of the body of work as a whole. Eleven Topical Reports were issued (prior to this report) that describe in great detail the sampling results at each of the ten power plants individually. The results showed that the SCR-FGD combination removed a substantial fraction of mercury from flue gas. The coal-to-stack mercury removals ranged from 65% to 97% for the units with SCR and from 53% to 87% for the units without SCR. There was no indication that any type of FGD system was more effective at mercury removal than others. The coal-to-stack mercury removal and the removal in the wet scrubber were both negatively correlated with the elemental mercury content of the flue gas and positively correlated with the scrubber liquid chloride concentration. The coal chlorine content was not a statistically significant factor in either case. Mercury removal in the ESP was positively correlated with the fly ash carbon content and negatively correlated with the flue gas temperature. At most of the units, a substantial fraction (>35%) of the flue gas mercury was in the elemental form at the boiler economizer outlet. After passing through the SCR-air heater combination very little of the total mercury (<10%) remained in the elemental form in the flue gas; this was true for all SCR catalyst types and sources. Although chlorine has been suggested as a factor affecting the mercury speciation in flue gas, coal chlorine was not a statistically significant factor affecting mercury speciation at the economizer exit or at the air heater exit. The only statistically significant factors were the coal ash CaO content and the fly ash carbon content; the fraction of mercury in the elemental form at the economizer exit was positively correlated with both factors. In a direct comparison at four SCR-equipped units vs. similar units at the same sites without SCR (or with the SCR bypassed), the elemental mercury fractions (measured at the ESP outlet) were lower, and the coal-to-stack mercury removals were higher, when the SCR was present and operating. The average coal-to-stack mercury removal at the four units without an operating SCR was 72%, whereas the average removal at the same sites with operating SCRs was 88%. The unit mercury mass balance (a gauge of the overall quality of the tests) at all of the units ranged from 81% to 113%, which were within our QA/QC criterion of 80-120%.},
doi = {10.2172/893601},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Mar 07 00:00:00 EST 2006},
month = {Tue Mar 07 00:00:00 EST 2006}
}

Technical Report:

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  • CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP) - wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of catalystmore » degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on Hg speciation and the efficacy of different FGD technologies for Hg capture. This document, the second in a series of topical reports, describes the results and analysis of mercury sampling performed on a 330 MW unit burning a bituminous coal containing 1.0% sulfur. The unit is equipped with a SCR system for NOx control and a spray dryer absorber for SO{sub 2} control followed by a baghouse unit for particulate emissions control. Four sampling tests were performed in March 2003. Flue gas mercury speciation and concentrations were determined at the SCR inlet, air heater outlet (ESP inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process stream samples for a mercury balance were collected to coincide with the flue gas measurements. Due to mechanical problems with the boiler feed water pumps, the actual gross output was between 195 and 221 MW during the tests. The results showed that the SCR/air heater combination oxidized nearly 95% of the elemental mercury. Mercury removal, on a coal-to-stack basis, was 87%. The mercury material balance closures for the four tests conducted at the plant ranged from 89% to 114%, with an average of 100%. These results appear to show that the SCR had a positive effect on mercury removal. In earlier programs, CONSOL sampled mercury at six plants with wet FGDs for SO{sub 2} control without SCR catalysts. At those plants, an average of 61 {+-} 15% of the mercury was in the oxidized form at the air heater outlet. The principal purpose of this work is to develop a better understanding of the potential Hg removal ''co-benefits'' achieved by NOx, and SO{sub 2} control technologies. It is expected that this data will provide the basis for fundamental scientific insights into the nature of Hg chemistry in flue gas, the catalytic effect of SCR systems on Hg speciation and the efficacy of different FGD technologies for Hg capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize Hg removal.« less
  • CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dryer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2)more » evaluate the effect of catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the seventh in a series of topical reports, describes the results and analysis of mercury sampling performed on a 1,300 MW unit burning a bituminous coal containing three percent sulfur. The unit was equipped with an ESP and a limestone-based wet FGD to control particulate and SO2 emissions, respectively. At the time of sampling an SCR was not installed on this unit. Four sampling tests were performed in September 2003. Flue gas mercury speciation and concentrations were determined at the ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process stream samples for a mercury balance were collected to coincide with the flue gas measurements. The results show that the FGD inlet flue gas oxidized:elemental mercury ratio was roughly 2:1, with 66% oxidized mercury and 34% elemental mercury. Mercury removal, on a coal-to-stack basis, was 53%. The average Hg concentration in the stack flue gas was 4.09 {micro}g/m{sup 3}. The average stack mercury emission was 3.47 Ib/TBtu. The mercury material balance closures ranged from 87% to 108%, with an average of 97%. A sampling program similar to this one was performed on a similar unit (at the same plant) that was equipped with an SCR for NOx control. Comparison of the results from the two units show that the SCR increases the percentage of mercury that is in the oxidized form, which, in turn, lends to more of the total mercury being removed in the wet scrubber. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NOx, and SO{sub 2} control technologies. It is expected that this data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal.« less
  • CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{submore » 2} control technologies. It is expected that this data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the tenth in a series of topical reports, describes the results and analysis of mercury sampling performed on two 468 MW units burning bituminous coal containing 1.3-1.7% sulfur. Unit 2 is equipped with an SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO{sub 2} emissions, respectively. Unit 1 is similar to Unit 2, except that Unit 1 has no SCR for NOx control. Four sampling tests were performed on both units in January 2005; flue gas mercury speciation and concentrations were determined at the economizer outlet, air heater outlet (ESP inlet), ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process samples for material balances were collected with the flue gas measurements. The results show that the SCR increased the oxidation of the mercury at the air heater outlet. At the exit of the air heater, a greater percentage of the mercury was in the oxidized and particulate forms on the unit equipped with an SCR compared to the unit without an SCR (97.4% vs 91%). This higher level of oxidation resulted in higher mercury removals in the scrubber. Total mercury removal averaged 97% on the unit with the SCR, and 87% on the unit without the SCR. The average mercury mass balance closure was 84% on Unit 1 and 103% on Unit 2.« less
  • CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{submore » 2} control technologies. It is expected that these data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the ninth in a series of topical reports, describes the results and analysis of mercury sampling performed on Unit 1 at Plant 7, a 566 MW unit burning a bituminous coal containing 3.6% sulfur. The unit is equipped with a SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO{sub 2} emissions, respectively. Four sampling tests were performed in August 2004 during ozone season with the SCR operating; flue gas mercury speciation and concentrations were determined at the SCR inlet, SCR outlet, air heater outlet (ESP inlet), ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Three sampling tests were also performed in November 2004 during non-ozone season with the SCR bypassed; flue gas mercury speciation and concentrations were determined at the ESP outlet (FGD inlet), and at the stack (FGD outlet). Process samples for material balances were collected during the flue gas measurements. The results show that, at the point where the flue gas enters the FGD, a greater percentage of the mercury was in the oxidized form when the SCR was operating compared to when the SCR was bypassed (97% vs 91%). This higher level of oxidation resulted in higher mercury removals in the FGD because the FGD removed 90-94% of the oxidized mercury in both cases. Total coal-to-stack mercury removal was 86% with the SCR operating, and 73% with the SCR bypassed. The average mercury mass balance closure was 81% during the ozone season tests and 87% during the non-ozone season tests.« less