EPA/600/D-85/253 October 1985 TECHNOLOGIES FOR CONTROLLING POLLUTANTS FROM COAL COMBUSTION Wade H. Ponder Assistant to the Laboratory Director Air and Energy Engineering Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Research Triangle Park, NC 27711 AIR AND ENERGY ENGINEERING RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U S. ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NC 27711 ------- NOTICE This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorse- ment or recommendation for use. ------- -1- Summary Sulfur dioxide, nitrogen oxides, and particles are the predominant pol- lutants emitted from the combustion of coal. One goal of current R&D activi- ties is to reduce the costs for controlling these pollutants. Several technologies have the capability to reduce emissions of one or more of these pollutants. Some of the technologies are currently available. Others will be available over the next 5-10 years, depending on market factors. One problem associated with most of the currently available technologies is high cost. For example, the capital cost of scrubbers can range as high as 30% of the cost of the power plant. Some of the "advanced technologies" show great promise for more efficient removal of pollutants at lower costs. We are particularly encouraged with the cost saving potential of LIMB, E-SOX, Staged ESP's, and Electrostatic Enhancement of Fabric Filtration which are currently under development by EPA. For example, the application of LIMB (approximately 60% SO2 removal) as a partial substitute for flue gas desulfurization (approximately 90% SO2 removal) may result in cost savings as great as $670 per ton SO2 removed. This estimate is based on a 300 MW utility boiler firing coal which contains approximately 2% sulfur. Our research findings are encouraging. There is good potential for major breakthroughs that will allow acceptable control of coal-related pollutants at reasonable costs. ------- Introduction The Environmental Protection Agency has several programs mandated by Congress to achieve environmental goals related to the combustion of coal. Ihree of these programs are: (1) the National Ambient Air Quality Standards (NAAQS) program which attempts to set goals for ambient air quality which ensure protection of human health and welfare; (2) the New Source Performance Standards (NSPS) program which attempts to reduce future air quality problems by requiring i nstal lation of best emi ssion controls on new or substantially modified pollution sources; and (3) the National Acid Precipitation Assessment Program (NAPAP) which attempts to identify causes and effects of acid precipi- tation in order to provide a scientific basis for decision making by regulators and legislators. The NAAQS and NSPS programs have been in place for some time, and their effects have already been factored into the coal use equation. There are no current or near-term actions contemplated under these programs which would alter coal markets. However, should the Congress pass acid rain legislation, the result could be a significant impact upon future use of coal. At present, the NAPAP program is developing the data base that will improve the ability to make decisions concerning the need for acid rain legislation. Current research efforts are focused on the identification and assessment of acid rain sources and effects and the development of capabi1ities for evaluating control strategies to mitigate these effects. If the research on sources and effects of pollutants brings us to the position of being able to make reasonable, defensible decisions concerning control strategies, a number of control technologies will be considered in the strategies. Some control technologies are currently commercial, and other "advanced technologies" which may help mitigate the adverse effects of pollutant ------- -3- emissions on the environment are being evaluated. At the EPA Office of Research and Development, one of the efforts within NAPAP is to assemble performance and cost data for all applicable control technologies. The technology program is identifying and developing new technologies which may reduce emissions in a more cost-effective manner and wi11 provide this infor- mation to Congress and regulatory agencies in a timely manner to ensure that the chosen strategies and legislation follow the most beneficial route (taking costs into consideration). We at EPA are hopeful that the emission reduction technologies currently being evaluated will meet the dual challenge of reducing emissions and mini- mizing the potential disruption in coal markets. This paper wi11 focus on the status, effectiveness, and costs of the currently available and advanced technologies for controlling sulfur dioxide, nitrogen oxides, particles, and combinations of these pollutants. Technologies for Sulfur Dioxide Control Background Currently, about 25 million tons of SO2 are emitted annually into the atmosphere by various uti1ity and industrial sources in the United States. SO2 has been associated with such environmental concerns as adverse health effects, visibility deterioration, material corrosion, and acid rain. Generally, there are three types of technologies which can reduce the emis- sions of SO2: 1. Pre-combustion technologies which remove the sulfur from the coal before it is burned. 2. Combustion technologies which capture or remove the SO? during the combustion process, 3. Post-combustion technologies which remove the SO? from the combus- tion gases produced when coal is burned. ------- -4- Table 1 summarizes these control technologies for SO2 control. Commercial Technologies Flue Gas Desulfurization - The post-combustion technology known as flue gas desulfurization (FGD) is the only technology which has been used exten- sively by power plants for SO2 control. To date, more than 120 FGD instal- lations control SO2 emissions from about 53,000 MW of power plant capacity. By the year 2000, there will be approximately 215 FGD units controlling over 106,000 MW of power plant capacity. Some FGD processes produce a waste byproduct and some produce a saleable byproduct such as sulfur or sulfuric acid. Almost all current and planned FGD installations are the waste-producing type because they are generally less expensive. The most common FGD processes that produce a waste product are those which use a lime or limestone slurry to remove S0£. The lime or lime- stone reagent reacts with the SO2 and produces a waste byproduct. Currently available FGD technology is expensive. Capital costs are typically $200 to $300 per kW of power plant capacity. These costs amount to as much as 20 to 30% of the cost of a new power plant without an FGD system. Thus, for a new, 500 MW power plant priced at $1000/kW ($500 million), the capital costs for FGD would be $200 to $300/kW ($100 to $150 million). FGD costs can be expected to range from about $600 per ton of SO2 removed to more than $1000 per tonJ1) (1) Actual costs will vary depending on site-specific factors. The costs have been determined to be $670/ton of SO2 for the following case: 1. FGD unit installed at a new, 500 MW power plant. 2. The capacity factor is 62.8%; i.e., the plant operates 5500 hr/yr. 3. Coal is fired at a rate of 812 lb/MW-hr. 4. The coal contains 3.36% sulfur. 5. Levelized annual revenue requirement is $41 million (in 1984 dollars). Source: Economics of Nitrogen Oxides, Sulfur Oxides, and Ash Control Systems for Coal-Fired Utility Power Plants, EPA-600/7-85-006, February 1985. ------- -5- Since the early 1970's, EPA's research program has played an important role in upgrading the performance and reliability of the lime and limestone FGD technology. Recently, our Laboratory has demonstrated that the performance and reliability of these FGD processes can be significantly improved by the addition of organic acids to the lime or limestone slurry. This process has produced beneficial results in several full-scale utility applications. We continue to seek lower cost FGD processes with particular emphasis on a spray dryer FGD system which offers the potential for significantly lower capital costs than corresponding wet systems. Physical Coal Cleaning - Physical coal cleaning is generally viewed as a supplement to FGD for SOg control. Coal may be "cleaned" by crushing and washing to remove mineral impurities (i.e., ash), including inorganic compounds containing sulfur. The cleaning processes can reduce the SO2 emissions from the combustion of coal by only 10 to 50%, depending on the composition and characteristics of the coal. Currently, about 30% of coal used in power plants is cleaned. While the cost of coal is increased by 15 to 30% by the cleaning process, part of these costs may be offset by transportation cost savings and reductions in boiler operating costs. Physical coal cleaning costs are likely to be in the range of $300 to $500 per ton of S02 removed.^ (1) Actual costs will vary depending on site-specific factors. The costs have been determined to be $450 per ton of SO2 removed for the following case: 1. Coal cost is $30/ton. 2. Coal cost is increased 25% by cleaning. 3. The cleaning process results in a 25% decrease in SO2 emissions. ------- -6- Advanced (Not Commercial) Technologies Chemical Coal Cleaning - The pre-combustion technology known as chemical ooal cleaning has the potential for removal of both inorganic and organically bound sulfur from coal before it is burned, thereby greatly reducing the emissions of SO2 during combustion. The cost per ton of SO2 removed is higher for chemical coal cleaning than for existing commercial technologies. Chemical coal cleaning costs are likely to be in the range of $800 to $1500 per ton of SO2 removed. ^ Even though the technology is expensive, it may be important in allowing conversion of certain existing oil and gas facilities to coal since the large cost differential between coal and oi1 or gas may be sufficient to justify the relatively high costs of chemical coal cleaning. The research programs that we have conducted in this area and the ongoing research at DOE are important first steps in bringing the technology to commercialization. However, this can be accomplished only with significant involvement of industry, and market factors will be the ultimate determinant of the extent of industrial participation. 0) Actual costs will vary depending on site-specific factors. The cost range specified was calculated from data obtained from the following sources: 1. Evaluation of Physical/Chemical Coal Cleaning and Flue Gas Desulfuri- zation, EPA-600/7-79-250, November 1979. 2. Economic Evaluation of Limestone and Lime Flue Gas Desulfurization Processes, EPA-600/7-83-029, May 1983. ------- -7- Technologies for Nitrogen Oxide Control Background EPA recently estimated that about 20 million tons of nitrogen oxides ire emitted annually from stationary and mobile sources in the United States. The combustion of coal by power plants accounted for nearly 30% of these emissions. The family of nitrogen oxide compounds, including NO, NO2, and other compounds, is usually referred to generically as MN0X." NO2 has been designated by EPA as a criteria pollutant because it produces adverse human health effects. It also contributes to the formation of photochemical oxidants and is an acid rain precursor. N0X control technologies can be divided into two categories: (1) combustion technologies and (2) post-combustion technologies. Table 2 summarizes important N0X control technologies. Commercial Technologies Low Excess Air Firing - For existing coal-fired boilers, one N0X control technique is the reduction of excess air supplied to the burner. This tech- nique, referred to as low excess air firing, can reduce N0X emissions by as much as 20% and has the added benefit of increased boiler efficiency. Capital costs average only about $2/kW. All boilers, however, do not have sufficient flexibility to achieve this level of emission reduction. Staged Combustion (Overfire Air) - A variation of the low excess air approach is to operate the lower burners (utility boilers have multiple rows of burners located on the boiler's vertical walls) at the lowest excess air level possible and provide additional air in the upper regions of the boiler. EPA field tests of 22 pulverized-coal-fired boilers using low excess air combined with staged combustion showed that N0X emission reductions of about 10-40% can be achieved at a cost of about $300 per ton of N0X removed. ------- -8- Reduced load - Utilities sometimes choose to reduce emissions by reducing load. Obviously, this approach is equally applicable to existing or new units. First Generation Burner Technology - The major thrust of EPA's N0X re- duction program is to develop the technology for new low-NOx burners which may be either retrofitted to existing boilers or incorporated into new designs. These burners reduce N0X by delaying the mixing of fuel and air, thereby limiting the availability of free oxygen in the initial burning process. First generation burner technology has already been applied commercially and was the basis for reducing the New Source Performance Standard (NSPS) for N0X in 1979 for coal-fired utility boilers. Costs have been estimated at about $185 per ton of N0X removed. Thermal De-NOx (Ammonia Injection) - This process involves the injection of ammonia into the hot flue gas to reduce NO to N£ and O2, thereby decreasing N0X emissions. The process is commercially offered by the Exxon Research and Engineering Company. The process is expensive; recent estimates are in the range of $600 per ton of N0X removed. Advanced (Not Commercial) Technologies Second Generation Burner Technology - While conventional combustion modi- fications have been used to achieve emissions below NSPS levels, we are exploring advanced combustion techniques to reduce N0X even further. The most promising technique is second generation low-N0x burners. Two such concepts developed under EPA sponsorship are the distributed mixing burner (for wall-fired boilers) and the rich fireball (for tangentially fired boilers). In experimental tests, these techniques have shown the potential to reduce N0X emissions by more than 50% from current NSPS levels for pulverized- coal-fired units. The distributed mixing burner has been installed on an ------- -9- industrial-sized boiler (22 MW) and has achieved up to 70% N0X reductions under optimal conditions. The rich fireball, installed on a 400 MW utility boiler, has achieved up to 50% reduction in N0X emissions in long-term opera- tion. For new boilers, N0X levels of less than 50% of current NSPS levels should be achievable. Although these control systems represent state-of-the-art technologies, no ful1 scale field data exist because market factors and other incentives have not yet generated industrial interest in commercialization of the systems. The costs associated with this technology should be about the same as for first generation low-N0x burners (about $185/ton N0X). Reburning Technology - Studies are underway to reduce N0X emissions by staged introduction of fuels in the firebox. This combustion technology, referred to as reburning, involves the introduction of coal or heavy oil as the first stage fuel and light oil or gas as the second stage fuel. Bench scale tests have shown that the "reburning" of first stage combustion gases during the second stage combustion under chemically reducing conditions results in 50 to 80% N0X reductions. Pi 1 ot scale studies (10 million Btu/hr or 3 MW) to veri fy laboratory findi ngs are underway. Although the Japanese have evaluated this technology on commercial size units, no commercial demon- strations have been conducted in the United States. Cost estimates are approximately $300 per ton of N0X removed. Flue Gas Denitrification - N0X emi ssions from power plants may be reduced by 80 to 90% through the application of selective catalytic reduction (SCR) of N0X in the flue gas with ammonia as the reactant. For the most part, this SCR technology has been developed and commercially applied in Japan. EPA has sponsored pi 1ot scale tests of an SCR process known as the Hitachi Zosen ------- -10- process. These tests show that the process can remove up to 90% of the N0X in flue gases which contain the full loading of particles from a coal-fired boiler. Cost estimates for utilizing SCR are very high—approximately $4000 per ton of N0X removed. Technologies for Particle Control Background Coal-fired power plants are a major source of particle emissions to the atmosphere, and the effect of fine particles on public health and welfare continues to be a major national environmental concern. EPA promulgated both primary (to protect health) and secondary (to protect welfare) National Ambient Air Quality Standards (NAAQS) for Total Suspended Particulate (TSP) in 1971. EPA also set New Source Performance Standards (NSPS) for a number of important sources of particulate matter, including coal-fired power plants. Although these standards and compliance efforts have produced major reduc- tions in the national TSP over the past 10 years, many regions are still unable to meet primary standards. In these regions industries will not only have to retrofit their existing equipment with particle control devices, but they will also have to institute controls on sources of fugitive particles if primary standards are to be met. Additionally, there is increasing concern about the health effects of respirable particles. Atmospheric particles appear to be a factor in a worsen- ing visibility problem in many parts of the country. These and other concerns continue to focus attention on fine particle control technologies. Table 3 summarizes information on important particle control technologies. Essentially all effective approaches involve particle removal subsequent to combustion. ------- -11- Commercial Technologies Electrostatic Precipitators - A portion of the incombustible portion of the coal is emitted from the boiler as particles (sometimes called flyash). Electrostatic precipitators (ESP's) are the most commonly used device for controlling the emission of these particles. An ESP is basically a large box with many rows of metal collection plates positioned parallel to the direction of flue gas flow through the box. High voltage is applied to wires located between these collection plates. The voltage produces an electric discharge (corona) which electrically charges the particles. The charged particles then move to the collection plates as a result of the electric field that exists between the wires and the plates. Conventional ESP's are capable of efficient particle control (greater than 99%). ESP costs are likely to be in the range of $70 to more than $300 per ton of flyash removed. (*) Fabric Filters - Fabric filters (sometimes called baghouses) are the major alternative to ESP's for particle control. These filters work like very large vacuum cleaners. Combustion gases laden with particles are forced through the filters, and the particles are entrapped in the fine mesh structure (!) Actual costs will vary depending on site-specific factors. The costs have been determined to be $80/ton of flyash removed for the following case: 1. ESP is installed on a new, 500 MW power plant. 2. ESP is "cold side"; i.e., it is downstream of the flue gas denitri- fication process. 3. The capacity factor is 62.8%; i.e., the plant operates 5500 hr/yr. 4. Coal is fired at a rate of 812 Ib/MW-hr. 5. The coal contains 15.1% ash of which 80% is flyash. 6. Levelized annual revenue requirement is $12.8 million (in 1984 dollars). Source: Economics of Nitrogen Oxides, Sulfur Oxides, and Ash Control Systems for Coal-Fired Utility Power Plants, EPA-600/7-85-006, February 1985. ------- of the filter. For most particles, the fabric filtration process is very efficient (99.9%), but the filters are very large and expensive to install, operate, and maintain. Costs may be expected to be in about the same range as costs for ESP's ($70-300/ton of particles removed). Advanced (Not Commercial) Technologies The major problems with both ESP's and fabric filters are their high costs and their operational uncertainties. Our research program is directed toward reducing costs by as much as 50% and minimizing the operational uncertainties. EPA engineers have made significant progress toward the achievement of these ambitious goals, and two of the advanced technologies which have resulted from their research are described below. Multi-Stage Electrostatic Precipitator - This advanced ESP system, developed by EPA, consists of a device for precharging the particles followed by a specially designed downstream collector. Pilot test results of the staged ESP concept have been most encouraging and suggest cost savings in the order of 50% for coals with difficult-to-collect ashes. Experience at a larger facility will be necessary before the commercial potential of this technology can be evaluated. Market factors will control the extent and the timing of the commercialization of this technology. Electrostatic Enhancement of Fabric Filtration - The most promising concept for reducing the costs of fabric filters is electrostatic enhancement of the filters. Adding an electric field in the fabric filter allows higher gas flow rates through the filter at a given pressue drop without sacrificing collection efficiency. The increased gas flow allows a drastic reduction in the size of the filter required to get the job done, with a corresponding cost reduction. Our research suggests that both capital and operating costs ------- can be reduced by 30-60% over commercial systems. These findings must be evaluated in some larger-scale tests to verify the research results. At present, the research is still underway. Technologies for Combined Pollutant Control Background In addition to separate controls for SO2, N0X, and particles, several technologies simultaneously remove two or more of these pollutants. These technologies are in various stages of development, and none has been fully commercialized for power plant operation. Table 4 lists four such technol- ogies that are now or have been components of the EPA R&D program. Commercial Technologies Currently, physical coal cleaning is the only commercial technology avail- able for combined control of pollutants from utility boilers. Advanced (Not Commercial) Technologies Limestone Injection Through Multi-Stage Burners (LIMB) - This technology evolved from the EPA-sponsored low-N0x coal burner development work previously discussed. It was recognized that the condition which resulted in reduced N0X might also promote capture of sulfur compounds if sorbents (e.g., limestone) were added. Both retrofit and new applications of the technique to boilers could be a comparatively simple and inexpensive way to reduce SO2 and N0X emissions. The primary objectives of the LIMB R&D program are: (1) for retrofit, 50 to 60% reduction of both N0X and SO2 from uncontrolled levels; (2) for new systems, 70 to 80% N0X reduction and 70 to 90% SO2 reduction from uncontrolled levels; and (3) cost savings of $224 to $670 per ton of SO2 removed (depending on coal sulfur content) compared to flue gas desulfurization (FGD). I would like to emphasize that these are objectives of our research ------- -14- and development program and that many technical uncertainties must be clarified before we can claim achievement of these objectives. Further, LIMB will not serve as full substitution for existing technologies like FGD in those appli- cations where high removal efficiency would be required. The EPA research program has shown that removal efficiencies depend on factors such as coal type, alkali selected, and boiler conditions. However, recent research at the pilot scale has identified techniques that may increase the levels of SO2 removal in the LIMB process. For example, the presence of metal oxides such as MgO, Fe203, and M0O3 shows potential for the promotion of limestone reactivity resulting in increases in SO2 removal efficiency. Research is continuing in an effort to define the mechanisms by which these and other additives promote limestone reactivity so that SO2 removal can be maximized. Our research has also shown that SO2 removal can be enhanced by the use of high surface area sorbents. The high surface area sorbents are produced by the calcination of limestone (CaC03) and dolomitic limestone (CaC03*MgC03) to produce lime (CaO) and dolomitic lime (CaO'MgO). These products can then be hydrated to produce hydrated lime and hydrated dolomitic lime which are also high surface area sorbents. Even though high surface area sorbents are more expensive than limestone, evaluations of the LIMB process using these sorbents suggest that LIMB still may have a cost advantage over FGD for both retrofit and new sources. The first commercial scale demonstration of the LIMB process in the U. S. will be at the 105 MW single-wall-fired unit at the Edgewater Station of the Ohio Edison Company. Long-term testing will begin July 1987. Costs have been projected to be about 50-70% of the costs associated with the use of FGD technology for SO2 control. ------- -15- Approximately 90% of utility boilers are either wall-fired or tangentially fired, and the split between the two types is approximately equal. Because of the substantial differences between the firing systems, technology developed for wall-fired boilers is not directly applicable to tangentially fired boilers. EPA's research program will evaluate LIMB-type technology on such boilers up to the small industrial boiler size category. Fluidized Bed Combustion - Fluidized bed combustion (FBC) is another technology that simultaneously reduces emissions of SO2 and N0X. FBC involves the burning of coal in a bed of limestone that has been fluidized with the combustion air. The limestone in the bed reacts with the SO2 released during the combustion of the coal. The solid material which results from this reaction can be disposed of as a dry solid waste along with the coal ash. Several successful industrial scale (as opposed to utility scale) FBC units are currently in operation. FBC shows promise for removing SO2 from coal combustion at a lower cost per ton of SO2 than conventional flue gas desulfur- ization technologies. Although FBC is generally limited to new units, retro- fit may be cost-effective in select cases where a utility may wish to upgrade the capacity of an older unit. EPA does not have an active R&D program for FBC, but we do monitor developments in this area. TVA, EPRI, and DOE have had important FBC development programs in recent years. Three utility FBC units are currently under construction in the U.S. Electrostatic Precipitator Particle Removal and Spray Dryer S0X Removal Process (E-SOX) - Laboratory and pilot scale experiments have proven the tech- nical feasibility of combining multi-stage ESP technology and spray dryer technology to collect both particles and SO2 in an existing ESP. The process uses the multistage ESP to reduce the space requirement in the ESP for particle removal, and the freed space is converted to a spray dryer by adding suitable ------- -16- spray nozzles. Initial experiments with NagCOj solutions show that the S02 removal efficiency ranges from 50 to 80% with inlet SO2 concentrations up to 1600 ppm. Similar encouraging results have been obtained in experiments with CaO slurry. The process can be retrofitted during a planned outage and has the potential for providing a very low cost option for SO? control with no reduction in the level of particle control. The costs associated with the E-SOX process are expected to be comparable to LIMB costs; i.e., about 50-70% of the costs associated with the use of FGD for SO2 control. Conclusion Table 5 summarizes comparative cost data for all of the technologies discussed. The table indicates that some of the control technologies have the potential for allowing the use of our abundant coal reserves at reasonable costs and without undue environmental degradation. For this reason, the EPA research program will continue to explore the fundamental interactions between combustion products and sorbents in order to increase efficiencies and reduce costs of the control technologies. This work—coupled with related research programs at 00E, TVA, and the private sector (e.g., EPRI)--provides the technical foundation needed should rapid commercialization of the tech- nologies be required in the future to meet energy or environmental incentives. ------- Table 1. Summary of Technologies for SO? Control Description State of Application Development Effectiveness Availability 1. Pre-combustion 1. Physical Cleaning 2. Chemical Cleaning Retrofit Commercial 10-50% SO? removal Current Replace Not Up to 90% After 1990 Oil/Gas commercial SO2 removal (at an energy penalty of approximately 25%) 11. Combustion - Technologies which simultaneously remove SO? and other pollutants during the combustion process are summarized in Table 4. *-4 I III. Post-Combustion 1. Flue gas desulfuri- zation Retrofit/ New Commercial 60-95% S02 removal Note: The higher removal efficiencies may requlre the use of organic acids to enhance F6D. Current ------- Table 2. Summary of Technologies for NO* Control —. II i— ¦ . 1 ¦ nnnjr m .... I m i rnlm— mm ¦ —I Ail ¦ Description State of Application Development Effectiveness Availability I. Pre-combustion - None II. Combustion 1. Low Excess Air Firing Retrofit 2. Staged Combustion (Overfire Air) 3. Reduced Load 4. First Generation Burner Technology 5. Second Generation Burner Technology 6. Reburni ng Technology III. Post-Combustion 1. Thermal De-NOx (Ammonia Injection) 2. Flue Gas Denitrifi- cation (Selective Catalytic Reduction) Retrofit/New Retrofit/New Retrofit/New Retrofit Retrofit/New Retrofit/New Commercial Retrofit/New Commercial Commercial Commercial Demonstration Experimental Commercial Commercial in Japan; pilot scale in U.S. Research data suggest potential Current for up to 20% N0X removal 10-40% NO* removal Current Up to 50% Current Research data suggest potential Current for up to 50% NQX removal Research data suggest potential 1988 for 50-70% N0X removal Research data suggest potential after 1990 for 50-80% N0X removal 40-60% N0X removal Current 80-90% N0X removal 1990 CO I ------- Table 3. Summary of Technologies for Particle Control Description Application State of Development Effectiveness Availability I. Pre-combustion 1. Physical Retrofit Coal Cleaning II. Combustion - None III. Post-combustion 1. Electrostatic Retrofit/ Precipitator New 2. Fabric Retrofit/ Filter New 3. Two-Stage Retrofit/ Electrostatic New Precipitator 4. Electrostatic Retrofit/ Enhancement New of Fabric FiItration Commercial Commercial Commercial Pi lot scale Pi lot scale < 50% 99.5+% 99.5+% 99.5+* 99.5+% Current Current Current 1990 1990 ------- Table 4. Summary of Technologies for Combined Pollutant Control Description Application State of Development Effectiveness Availability I. Pre-combustion 1. Physical coal cleaning II. Combustion 1. LIMB 2. Fluidized Bed Combustion Retrofit/ New Commercial Retrofit/ New New Large scale pi lot; commercial demonstra- tion planned 10-50% S02 < 50% particles Retrofit: 50-60% N0X & SO2 New: 70-80% N0X 70-90% $02 Current 1989 I 0 1 Successful application 90% SO2 to industrial boilers NO* removal uncertain Post-1990 III. Post-Combustion 1. E-S0X Retrofit/ New Pilot 50-80% S02 99% particles 1990 ------- Table 5. Summary of Costs for Pollutant Removal Pollutant Pollutant Removal Removal Removed Technology Costs, $/Ton Efficiency, % SOo Flue Gas Desulfurization 600-1000* 60-95 £» Physical Coal Cleaning 300- 500+ 10-50 Chemical Coal Cleaning 800-1500+ up to 90 N0X Low Excess Air Firing < 10 up to 20 Staged Combustion (overfire air) 300 10-40 Reduced Load - up to 50 Low-NOx Burners 185 up to 50 Second Generation Low-NOx Burners 185 50-70 Reburning 200-300+ 50-80 Thermal De-NOx (ammonia injection) 600 40-60 Flue Gas Denitrification 4000+ up to 90 Particles Electrostatic Precipitator 70-300+ 99.5+ Fabric Filtration 70-300+ 99.5+ Hulti-Stage Electrostatic Precipitator 35-150+ 99.5+ Electrostatic Enhancement of Fabric Filtration 35-150+ 99.5+ so2/nox Limestone Injection Hulti-Stage Burners 50-70% Retrofit: 50-60 of FGD New; 70-80 NO* 70-90 S02 so2/nox Fluidized Bed Combustion < FGD up to 90 S02/Particles E-S0X 50-70% 50-80 S02 of FGD 99 particles ------- |