Jeffrey S. Thompson

LONG-TERM DEMONSTRATION OF SORBENT ENHANCEMENT ADDITIVE TECHNOLOGY FOR MERCURY CONTROL

Long-term demonstration tests of advanced sorbent enhancement additive (SEA) technologies have been completed at five coal-fired power plants. The targeted removal rate was 90% from baseline conditions at all five stations. The plants included Hawthorn Unit 5, Mill Creek Unit 4, San Miguel Unit 1, Centralia Unit 2, and Hoot Lake Unit 2. The materials tested included powdered activated carbon, treated carbon, scrubber additives, and SEAs. In only one case (San Miguel) was >90% removal not attainable. The reemission of mercury from the scrubber at this facility prevented >90% capture.

PILOT-SCALE EVALUATION OF THE IMPACT OF SELECTIVE CATALYTIC REDUCTION FOR NOx ON MERCURY SPECIATION

Full-scale tests in Europe and bench-scale tests in the United States have indicated that the catalyst, normally vanadium/titanium metal oxide, used in the selective catalytic reduction (SCR) of NO{sub x}, may promote the formation of Hg{sup 2+} and/or particulate-bound mercury (Hg{sub p}). To investigate the impact of SCR on mercury speciation, pilot-scale screening tests were conducted at the Energy & Environmental Research Center. The primary research goal was to determine whether the catalyst or the injection of ammonia in a representative SCR system promotes the conversion of Hg{sup 0} to Hg{sup 2+} and/or Hg{sub p} and, if so, which coal types and parameters (e.g., rank and chemical composition) affect the degree of conversion. Four different coals, three eastern bituminous coals and a Powder River Basin (PRB) subbituminous coal, were tested. Three tests were conducted for each coal: (1) baseline, (2) NH{sub 3} injection, and (3) SCR of NO{sub x}. Speciated mercury, ammonia slip, SO{sub 3}, and chloride measurements were made to determine the effect the SCR reactor had on mercury speciation. It appears that the impact of SCR of NO{sub x} on mercury speciation is coal-dependent. Although there were several confounding factors such as temperature and ammonia concentrations in the flue gas, two of the eastern bituminous coals showed substantial increases in Hg{sub p} at the inlet to the ESP after passing through an SCR reactor. The PRB coal showed little if any change due to the presence of the SCR. Apparently, the effects of the SCR reactor are related to the chloride, sulfur and, possibly, the calcium content of the coal. It is clear that additional work needs to be done at the full-scale level.

Cryogenic trapping of oxidized mercury species from combustion flue gas

Abstract To further understand the speciation and partitioning of mercury species in combustion systems, it is necessary to be able to identify and quantitate the various forms of oxidized mercury. Currently accepted methods for speciating mercury (Ontario Hydro Method, EPA Method 29, MESA Method) only separate elemental and oxidized forms of mercury at best, and they are expensive. This paper describes research on the application of cryogenics to the sampling and separation of oxidized forms of mercury from combustion flue gas. This research has resulted in the development and demonstration of a prototype cryogenic sampling device for the determination of oxidized mercury in flue gas. Preliminary results are encouraging, as they show that mercuric chloride and mercuric oxide can be effectively separated through the prototype device. Further development, refinement, and application of this device are expected to generate data that are critically needed to develop effective control technologies for mercury.

Subtask 4.24 - Field Evaluation of Novel Approach for Obtaining Metal Emission Data

Over the past two decades, emissions of mercury, nonmercury metals, and acid gases from energy generation and chemical production have increasingly become an environmental concern. On February 16, 2012, the U.S. Environmental Protection Agency (EPA) promulgated the Mercury and Air Toxics Standards (MATS) to reduce mercury, nonmercury metals, and HCl emissions from coal-fired power plants. The current reference methods for trace metals and halogens are wet-chemistry methods, EPA Method (M) 29 and M26A, respectively. As a possible alternative to EPA M29 and M26A, the Energy & Environmental Research Center (EERC) has developed a novel multielement sorbent trap (ME-ST) method to be used to sample for trace elements and/or halogens. Testing was conducted at three different power plants, and the results show that for halogens, the ME-ST halogen (ME-ST-H) method did not show any significant bias compared to EPA M26A and appears to be a potential candidate to serve as an alternative to the reference method. For metals, the ME-ST metals (ME-ST-M) method offers a lower detection limit compared to EPA M29 and generally produced comparable data for Sb, As, Be, Cd, Co, Hg, and Se. Both the ME-ST-M and M29 had problems associated with high blanks for Ni, Pb, Cr, and Mn. Although this problem has been greatly reduced through improved trap design and material selection, additional research is still needed to explore possible longer sampling durations and/or selection of lower background materials before the ME-ST-M can be considered as a potential alternative method for all the trace metals listed in MATS.

VALIDATION OF MERCURY CEMS WHEN COFIRING BIOMASS AT MADISON ELECTRIC'S BLOUNT STATION

The state of Wisconsin has been concerned about mercury deposition into its lakes and streams and has been evaluating strategies to reduce mercury emissions. As part of this effort, the Blount Station, owned and operated by Madison Gas and Electric Company (MGE), has undergone a project to evaluate the effects and potential mercury emissions reduction of cofiring preconsumer waste. MGE owns and operates the Blount Generating Station located in central Madison, Wisconsin. At present, Blount operates with nine boilers and six turbine generators. The two largest boilers at Blount produce 400,000 pounds of steam per hour at 950 F and 1250 psi. These larger boilers, MGEs Boiler Nos. 8 and 9, have the capability of cofiring both paper and plastic. MGEs Blount Generating Station was one of the first electric generating stations in the United States to retrofit its existing steam boilers to successfully burn refuse-derived fuel and other alternate fuels including waste paper and wood. It is the No. 9 boiler that was the focus of this project to determine the effect of cofiring PDF (plastic- and paper-derived fuel) on speciated mercury emissions. The project was laid out to compare four different fuel combinations: (1) coal feed only, (2) coal with plastic, (3) coal with paper, and (4) coal with paper and plastic. The design was to run the boiler for 2 days at each condition, thus allowing four samples to be taken at each condition. This plan was aimed at getting at least three representative samples at each condition and allowed for difficulties in sampling and boiler operation. The following objectives were accomplished as part of the project to determine the effects of cofiring PDF on mercury emissions and speciation at MGE Blount Station: Successfully completed all of the mercury sampling for each of the four boiler/PDF conditions using the Ontario Hydro (OH) mercury speciation method; Determined mercury concentrations at the stack location using mercury continuous emission monitors (CEMs) for each of the four boiler/PDF conditions; Calculated the overall mercury mass balance for each of the runs; Determined chlorine concentrations at the stack location using EPA Method 26A for each of the four boiler/PDF conditions; and Calculated speciated mercury flow to determine removal and/or transformations before its exiting the unit at the stack for each of the four boiler/PDF conditions.