INTERIM FINAL TECHNICAL REPORT November 1, 2000 through October 31, 2001

Transcription

1 INTERIM FINAL TECHNICAL REPORT November 1, 2000 through October 31, 2001 Project Title: ROLE OF COAL CHLORINE AND FLY ASH ON MERCURY SPECIES IN COAL COMBUSTION FLUE GAS ICCI Project Number: 00-1/2.2C-2 Principal Investigator: R.M. Statnick, CONSOL Energy Inc., Research & Development Other Investigators: J. A. Withum, CONSOL Energy Inc., Research & Development Project Manager: K. Ho, ICCI ABSTRACT The purpose of this project is to determine the role of coal chlorine on the oxidized/elemental mercury mole ratio. Several investigators have suggested that high coal chlorine (>0.3 wt.%) concentration produces very high oxidized/elemental mercury mole ratios. However, the data show wide scatter. In this study, two coals that contain high coal chlorine concentrations will be evaluated and the oxidized/elemental mercury mole ratio compared to the existing CONSOL database of eight boilers. During proposal preparation, one of the host-sites was purchasing a coal with a > 0.3 wt % chlorine concentration. The other host-site was purchasing a coal with ~ 0.2 wt % chlorine concentration. Since the utilities purchase the lowest cost fuel and the chlorine concentration in the coal could change over the year period between proposal submission and field testing, the actual coal chlorine concentration could vary from the proposal information. The tests will be conducted on two Illinois coal-fired boilers. The elemental and oxidized mercury flue gas concentration will be determined using the Ontario Hydro sampling method. The sampling program consists of four sampling locations: flue gas inlet to the air preheater, heated combustion air from the air heater, and two locations in the flue gas from the air preheater. CONSOL has shown that a F temperature gradient exists at the air preheater exit. The lowest flue gas temperatures occur just as the air preheater baskets enter the flue gas side from the air side of the air preheater. In addition to the flue gas mercury sample, a daily coal sample will be collected on each sampling day. All preparations for the sampling program have been completed: equipment was ordered, site visit conducted, sampling plan developed, and fabrication of specialized sampling probes and filters. The field sampling program began on October 29, 2001 and is scheduled for completion on November 9, 2001.

2 EXECUTIVE SUMMARY CONSOL R&D is conducting a series of flue gas mercury (Hg) measurements at two Illinoisbased coal-fired utility sites to determine the factors that influence Hg speciation and the role of coal chlorine in this process. Speciated Hg measurements will be obtained at the inlet and two locations at the outlet of the air preheater and the preheated combustion air exiting the air side of the preheater at plants burning high chlorine content Illinois coal. CONSOL will obtain and analyze coal and ash samples from each location. These data will be used to assess the factors that influence Hg speciation in coal combustion flue gas. The form of Hg in the flue gas is important when considering control options and costs. The Clean Air Act Amendments of 1990 (CAAA) required the Environmental Protection Agency (EPA) to evaluate the impact of anthropogenic mercury (Hg) emissions on human health and welfare, determine whether air pollutants emitted form coal-fired boilers should be regulated, and evaluate the impact of hazardous air pollutants on recreational and economic uses of the Great Lakes, Chesapeake Bay, and estuaries. EPA has issued a notice that regulations to control Hg emissions from coal-fired utilities will be promulgated by At present, there is no proven Hg control technology applicable to coal-fired utility systems. Pilotscale testing has identified the injection of activated carbon at reduced flue gas temperatures is a potential Hg control technology. A detailed cost evaluation performed by DOE resulted in Hg control costs ranging from $25,000 to $75,000 per pound of mercury removed for this control technique. Using the low figure of $25,000 per pound of Hg removed and an estimated Hg-in-coal concentration of 0.1 µg/g (ppm by weight basis) results in a Hg control cost of ~$5/ton of coal. Clearly, Hg control costs will be high and will place an additional economic burden on the use of Illinois coal as a primary energy source. As a direct result of SO 2 reduction required by Title IV of the CAAA, the Illinois coal industry lost markets and employment. The Illinois coal industry is being challenged by western, low-sulfur compliance coal. The use of this coal is based on the economic advantage of fuel switching over the cost of an FGD system. Prior testing by CONSOL and other research groups demonstrated that conventional wet FGD systems for SO 2 control operating in conjunction with an ESP for particulate control are capable of removing ~65% of the flue gas Hg. Controlling Hg with the existing FGD system has no impact on FGD operating costs; the cost effectiveness of FGD Hg control is $0/pound of Hg removed. This could be an economic incentive to install FGD systems for combined SOx/Hg control and would allow for the continued and expanded use of Illinois coals. The ESP-FGD system removes 80-90% of the oxidized mercury and essentially none of the elemental mercury. Understanding the impact of coal chlorine on the mechanism of mercury oxidation could lead to optimization of mercury removal by the ESP-FGD system. During coal combustion, the mercury contained in the coal is volatilized in the flue gas in its elemental and oxidized forms. It is speculated that the amount of mercury in these forms is dependent on coal source, coal chemistry, and combustion conditions. Though not fully

3 understood, it has been observed that the combustion of eastern bituminous coals results in a greater oxidized mercury fraction, while the combustion of western coals results in a greater fraction of elemental mercury. It is speculated, but not confirmed, that the coal chlorine concentration is the key factor influencing mercury speciation. This speculation is based on the observation that western coals are generally very low in chlorine, while eastern coals, specifically Illinois basin coals, contain higher concentrations of chlorine. Utility testing conducted by CONSOL and others has shown that the oxidized mercury generated during the combustion of eastern bituminous coals is effectively removed by wet scrubbers. Our testing also has shown that the elemental mercury generated from the combustion of western coals is sometimes removed with the fly ash. These data indicate that knowledge of mercury speciation is required to develop cost-effective control technologies. The scientific community has evidence that suggests high chlorine coal yield more oxidized mercury. Data suggest that coal containing > 0.3 wt % chlorine could yield > 90 % of the coal mercury reporting as oxidized mercury. However, the percentage of oxidized mercury vs. coal chlorine concentration data have significant scatter. The proposed program will investigate mercury speciation in the flue gas at two Illinois-based utility sites, firing high chlorine (> 0.2%) coal. While selecting host sites, one boiler was selected because the coal contained > 0.3 wt % chlorine at the time the proposal was written. Since coal contracts are negotiated annually and coal chlorine concentration can vary within the seam, the actual coal chlorine concentration will be determined using the coal fired during the sampling period. Speciated flue gas measurements will be made at the air preheater inlet and outlet and at the air preheater combustion air exit. Coal and ash samples will be obtained and analyzed. CONSOL will evaluate the data to determine the factors influencing mercury speciation. This information will be valuable to the scientific community and to the utility industry in the development and implementation of cost effective mercury control technology. The mechanism for mercury speciation could lead to breakthroughs in the development of control strategies. For example, if slight changes in the coal chlorine concentration can shift Hg speciation to the oxidized form, wet FGD will remove a higher percentage of the flue gas Hg. Additional breakthroughs in mercury control may occur once the scientific community identifies the factors that influence mercury speciation.

4 1 OBJECTIVES The objective for the proposed work is to develop fundamental information regarding the impact of coal chlorine on mercury speciation in coal combustion systems. This information is needed to develop cost-effective mercury controls beneficial to the Illinois coal market. Specific Technical Objectives of the program are: Determine the flue gas mercury speciation at two Illinois-based utilities at the inlet of the air preheater, the combustion air exit of the air preheater, and two flue gas temperatures at the outlet of the air preheater. Collect an analyze coal, ESP ash, and if available, air preheater deposit samples representative of the flue gas sampling period. Correlate the observed mercury speciation with analytical and operating data to identify factors that influence mercury speciation, specifically the role of coal chlorine. Identify the role of the air preheater in mercury speciation and removal. INTRODUCTION AND BACKGROUND As a result of the 1990 Clean Air Act Amendments (CAAA), the U.S. Environmental Protection Agency (EPA) revised the human daily mercury intake standard (rfd). Subsequently, the environmental community sued the EPA and the Federal District Court issued an order requiring EPA to propose mercury control regulations by 2003 and to promulgate the regulations by EPA issued a Mercury Information Collection Request that required utilities to determine the mercury concentration in all coal purchased for one year. In addition, a number of individual boilers were identified that were required to measure the mercury concentration at the inlet and exit of existing control equipment (e.g. ESP s, FGD s, fabric filters, etc). These results have been published and discussed at a number of meetings. One of the parameters that seems to influence the controllability of flue gas mercury is speciation. The oxidized form is more readily collected in ESP s and wet or dry FGD s. Potential mercury regulations threaten the Illinois coal industry because additional control costs would make switching to Power River Basin coal or natural gas more likely. If a method can be identified to increase the oxidized fraction of flue gas mercury, then the Illinois coal industry would be less affected by mercury regulations. Some Illinois coals contain high chlorine contents (greater than 0.2%). Coal chlorine is a factor that influences the amount of oxidized mercury that reports to the control equipment; the higher the coal chlorine, the greater the oxidized mercury fractions. A second factor that influences mercury removal is flue gas temperature. The lower the flue gas temperature is, the more mercury is removed in the ESP with the fly ash.

5 2 The results of this program will provide the Illinois coal industry with valuable information to evaluate no or low cost options to comply with the 2003 proposed regulations. EXPERIMENTAL PROCEDURES TEST PLAN This study will evaluate the effect of coal chlorine concentration and air preheater flue gas exit temperature on mercury speciation and removal. This study will evaluate mercury speciation with various Illinois coals, containing up to 0.3% to 0.4% chlorine and evaluate the effect of two flue gas temperatures on mercury speciation and removal. The study will be conducted at two full-scale Illinois utility boilers firing Illinois coal. The mercury speciation and concentration will be determined at four locations: The flue gas inlet to the air preheater The combustion air exiting the air preheater The low temperature flue gas side of the air preheater exit The high temperature flue gas side of the air preheater exit In addition, a daily coal and fly ash samples will be obtained during each daily mercury sampling period. If available, a sample will be obtained of air preheater deposits. State of the art sampling and analysis procedures will be used for the flue gas, combustion air, and solids samples. TEST FACILITIES The sampling program will be conducted at two Illinois utility boilers firing Illinois coal. The first boiler is a tangentially-fired unit and is equipped with a horizontal Ljungstrum air preheater. The unit is firing a high chlorine Illinois coal (about 0.35%). During the test program, we expect that it will continue to fire the same coal; however due to the nature of coal, the actual chlorine content during the sampling period may vary. The second boiler is a wall-fired unit. It is also equipped with a horizontal Ljungstrum air preheater. This unit is firing a medium chlorine content coal (about 0.2%). Again, during the test program, we expect that the unit will continue to fire the same coal; however, due to the nature of coal, the actual chlorine content during the sampling period may vary.

6 3 DAILY TEST PLAN The daily test plan is shown below: Time Activity Prepare sampling trains Establish boiler load Begin coal sampling Empty fly ash hoppers Conduct gas sampling at air preheater exit and inlet Recover gas sample solutions Obtain ESP hopper ash sample Obtain coal sample Clean equipment for next day activities Pack samples for transport Leave for motel The daily test schedule will be followed each test day except for the first and last day. On the first day, the activities will be limited to on-site safety training and setting up the equipment and trailer. On the last day, the activity is limited to recovering the equipment and packing the trailer for transport to the next site or home base. TEST PLAN The test plan consists of obtaining a minimum of three flue gas mercury gas samples over a oneweek period and daily coal and fly ash samples. A sample of the air preheater deposits will be obtained when, and if, convenient for the station. The air preheater deposit sample will require the station to go off-line. Ceasing electricity production is a function of load demand and/or station equipment repair requirements. In Figure 1, is a depiction of the generic sampling locations. SAMPLING LOCATIONS, PROCEDURES, AND ANALYTICAL REQUIREMENTS The following contains a discussion of all of the sampling points. Coal Feed to the Boiler. A representative daily, sample of the feed coal will be obtained during each test period. A grab sample from the gravimetric feeder will be obtained every thirty minutes

7 4 and placed into an air-tight bucket. After standard ASTM riffling and sampling, the coal sample will be analyzed for ultimate and proximate analysis, mercury, total chlorine, and major ash elements. ESP Ash. Prior to each test, the ESP hopper will be emptied. During the test period, the ESP hoppers will collect fly ash. After each test, the ESP hoppers will be sampled. The fly ash samples will be sealed in an airtight bucket. The fly ash will be analyzed for mercury and moisture. Flue Gas and Combustion Air Streams. Flue gas samples will be obtained at the air preheater inlet and two locations at the air preheater exit. There is a temperature distribution across the plane of flue gas flow. One side of the duct is 30 to 40 F cooler that the other. A single point combustion air sample will be obtained at the air preheater combustion air exit. These four samples will be obtained using the Ontario-Hydro Method. In this procedure, flue gas or combustion air is extracted from the duct stream. The gas is pulled through a heated glass-lined probe and quartz filter that removes the particulate matter. Total particulate mass loading is obtained from the filter weight gain. Probe and filter temperatures are maintained near the flue gas or combustion air temperatures. The gas exits the filter and is pulled through a series of chilled impingers. The first three impingers are filled with 100 ml of 1.0 N KCl solution. These impingers collect only the oxidized (ionic) mercury. The fourth impinger contains 100 ml of 5-8% H 2 O 2 solution to scrub out SO 2 to protect the permanganate solutions. This solution is analyzed for mercury and any mercury found is accounted as elemental mercury. The fifth and sixth impingers contain acid permanganate solution to collect elemental mercury. The seventh impinger contains silica gel to protect the downstream sample pump and gas meter from moisture. The impinger solutions are analyzed by cold vapor atomic absorption. ANALYTICAL FACILITIES The analytical instrumentation available for this work is located at the CONSOL R&D, South Park, Pennsylvania, facility. The laboratory includes state-of-the-art LECO analyzers for the determination of proximate analyses (moisture, ash, volatile matter, and fixed carbon), carbonhydrogen-nitrogen analysis, heating value (Btu), and sulfur content. The laboratory is equipped with a Parr model 1261 Btu analyzer. The ash elemental, trace elements, and water samples will be analyzed through a combination of techniques and instruments including a Dionex Model DX 100 and 4000i ion chromatographs, Thermo Jarrell Ash model 61 ICP-AES and a Thermo Jarrell Ash model IRIS/AP ICP-AES, Sciex model 250 ICP-MS, Jerome model 301 mercury analyzer, a UNICAM model 929 AA spectrometer with Hg concentrator and vapor attachment, and a Perkin Elmer model 5000 AAS with a Perkin Elmer MHS-20 Hydride Attachment. The sampling and preparation equipment (grinders, riffles, screens, mills, pulverizers, etc.) are also housed at this facility.

8 5 The CONSOL R&D Technical Services field test team maintains state-of-the-art EPA-style stack sampling equipment for the measurement of effluents from coal-fired combustion systems. Specialized equipment included in this equipment list that will be used during the field sampling program are the following: $ complete Ontario Hydro stack sampling systems and associated auxiliary components $ drying ovens $ analytical balances $ top loading balances $ electronic manometer for low flow characterization $ United Sensor 3-dimensional pitot probe and console $ Teledyne electrochemical gas analyzers $ hand-held digital temperature readouts $ aneroid barometers $ a variety of glass and stainless steel nozzles $ a variety of glass-lined probes for gas sampling $ a variety of pitot probes for velocity determination RESULTS AND DISCUSSION The mercury test program originally scheduled for spring was delayed until October-November, Task 1, Site Specific Sampling Plan, was completed. CONSOL negotiated the site access agreement, conducted a site visit, and developed a site specific sampling plan and sampling equipment modification list. Task 2, Equipment Preparation was completed. CONSOL ordered sampling equipment needed to conduct the field program, calibrated the pitot tubes and dry test meters, and packed the equipment and supplies into the mobile laboratory. Task 3, Field Sampling is about half completed. All of the equipment has been obtained, cleaned, calibrated, packed and shipped to Illinois. The first week sampling program was completed between October 29 and November 2, The second test program will be completed between November 5 through 9, CONCLUSIONS AND RECOMMENDATIONS No conclusions are available at this time. The November January period will provide sufficient time for sample analysis, data reduction, and report writing within the current contract schedule.

9 6 DISCLAIMER STATEMENT This report was prepared by Robert M. Statnick, CONSOL Inc., with support, in part by grants made possible by the Illinois Department of Commerce and Community Affairs through the Office of Coal Development and Marketing and the Illinois Clean Coal Institute. Neither Robert M. Statnick, CONSOL Inc., nor any of its subcontractors nor the Illinois Department of Commerce and Community Affairs, Office of Coal Development and Marketing, Illinois Clean Coal Institute, nor any person acting on behalf of either: (A) (B) Makes any warranty of representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately-owned rights; or Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed in this report. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring; nor do the views and opinions of authors expressed herein necessarily state or reflect those of the Illinois Department of Commerce and Community Affairs, Office of Coal Development and Marketing, or the Illinois Clean Coal Institute. Notice to Journalists and Publishers: If you borrow information from any part of this report, you must include a statement about the State of Illinois' support of the project.