WET FLUE GAS DESULFURIZATION (FGD) SYSTEMS ADVANCED MULTI-POLLUTANT CONTROL TECHNOLOGY B&W WET FGD SYSTEMS – FLEXIBILITY OF DESIGN AND ADVANCED FEATURES TO MEET CUSTOMER NEEDS When performance counts SINCE 1971, BABCOCK & WILCOX’s (B&W) WET FLUE GAS DESULFURIZATION (FGD) SYSTEMS, OR SCRUBBERS, HAVE OPERATED EFFICIENTLY, ECONOMICALLY AND RELIABLY, HELPING OUR CUSTOMERS MEET PERMIT REQUIREMENTS WHETHER AS A NEW SOURCE OR RETROFIT APPLICATION. CURRENT DESIGNS CAN ACHIEVE MORE THAN 99% REMOVAL OF SULFUR DIOXIDE (SO2). IMPROVEMENTS IN B&W’s WET SCRUBBER DESIGN AND AUXILIARY EQUIPMENT HAVE RESULTED IN SYSTEM AVAILABILITY GREATER THAN 99.5%. MULTI-POLLUTANT CONTROL CAPABILITIES INCLUDE FILTERABLE PARTICULATE, ACID MIST AND MERCURY. 2 3 Current B&W designs are achieving 99% SO2 removal with system availability greater than 99.5%. Controlling oxidation a worldwide leader in supplying and plugging in the tower, allows limestone forced oxidation units, the use of less expensive materials, New wet FGD systems can be and we continue to support this and eliminates the wastewater supplied with either forced technology. discharge stream. This process can oxidation or inhibited oxidation. be utilized with various reagents While limestone forced oxidation — limestone, lime, magnesium- Since the mid-1980s, limestone technology has proven successful enhanced lime, or sodium. forced oxidation has been the in many worldwide installations, leading wet FGD technology. This in some applications, the gypsum beneficial process converts calcium byproduct is no longer marketable, Scope of supply sulfite to calcium sulfate within and wastewater treatment and B&W is a full-scope supplier. In the absorber reaction tank and discharge have become a concern. addition to flue gas absorbers, improves scrubber operation while Therefore, some customers we supply reagent preparation producing a marketable gypsum believe that a dry FGD system is systems, dewatering systems and byproduct. B&W has more than the only option. However, there related system equipment. We also 34,000 MW of commercial units is an alternative: existing wet provide complete construction successfully operating with forced FGD technology with inhibited services through our subsidiary, oxidation, both in situ systems and oxidation. In this process, emulsified Babcock & Wilcox Construction Co., units operating with specialized sulfur, or sodium thiosulfate, is Inc. (BWCC). systems that are separate from added to the reagent feed tank. the absorber reaction tank, The addition of emulsified sulfur B&W employs an experienced most notably on magnesium- reduces the oxidation rate to below staff of design engineers, graphic enhanced lime systems. We are 15%, thus controlling scale deposits designers, project managers, and 2 3 As a full-scope supplier, B&W can provide complete wet FGD systems including reagent preparation, dewatering and other system equipment, as well as a wide range of multi-pollutant control technologies. the industry’s largest network of included improved SO2 removal, smaller boilers feeding one absorber field service engineers, including reduced absorber pump power and three larger units feeding two wet FGD field specialists, to consumption and maintenance absorbers. support project development, costs, reduced limestone project execution, and long-term consumption, the elimination of operation and maintenance. We costly additives, decreased landfill Choice of reagents also conduct extensive research requirements, and the opportunity We have designed FGD systems and development (R&D) activities to to provide a marketable byproduct. using a variety of reagents. While continue product advancement. most of our experience is with Fuel Experience limestone, designs have utilized Experience Our operating experience lime, magnesium-enriched lime, encompasses a complete range and waste soda ash. Limestone- Original Equipment Supply of fuels including bituminous, based systems using organic acid At the time of publication, B&W subbituminous, Powder River Basin enhancement have also been has provided wet FGD systems for (PRB), lignite and brown coals, as provided. a total scrubbed capacity of more well as various coal blends. We have than 43,000 MW. Through licensees also provided systems for heavy oil Advanced design benefits in China and Germany, our wet FGD and Orimulsion fuels. technology has been utilized for an We continue to optimize our FGD additional capacity of more than systems by refining the technology Large, Single Absorbers 77,000 MW. to improve SO removal efficiency, As the technology of wet FGD 2 improve long-term operating systems has improved, typical units reliability, and reduce capital and Upgrades have a single absorber module. maintenance costs. As an indication B&W has also improved the B&W absorber modules have been of our constant efforts to improve performance of more than 13,000 installed on boilers up to 1,300 MW. our designs, we currently have MW of non-B&W wet FGD systems Absorber design and reliability more than 40 patents involving wet by replacing the original absorber allow many utilities to treat the FGD technology. internals with our absorption tray flue gas from multiple boilers with technology, modern spray headers, one absorber. To reduce project and through forced oxidation costs B&W and our licensees have conversions. Benefits have provided systems with two to four 4 B&W’s wet FGD systems operate efficiently, economically and reliably on a variety of worldwide fuels to help our customers meet permitting and operating requirements. 4 The B&W Absorber optimum SO removal. An efficient distribution, which results in zones A proven design for high 2 spray header and nozzle system is of either inadequate or excess slurry SO2 removal used to evenly distribute the liquor, and reactant. With the tray, flue gas B&W’s absorber design features while the tray distributes the gas is uniformly distributed for the most flow. As determined by both physical efficient SO removal. provide the highest levels of SO2 2 removal, reduced operating costs and computer modeling, the gas- and significant reductions in side pressure drop induced by the The tray is rugged and can be used maintenance costs compared to other slurry sprays is not sufficient alone to as a convenient inspection and technologies. These benefits allow our adequately distribute the flue gas at maintenance platform when using customers to stay competitive with the base of the spray zone. In open appropriate planking. Costly and today’s increasingly more stringent spray towers, uniform gas distribution time-consuming scaffolding from the environmental requirements. is not achieved as effectively. bottom of the reaction tank is not required. Absorber design The B&W tray design effectively achieves uniform gas distribution, Our tray design has been proven Our absorber module is a counter- which becomes even more critical through extensive laboratory testing current flow design. Slurry is sprayed in larger diameter spray absorber and modeling and many years of downward from a series of headers towers. Without a tray, some zones successful operation. and nozzles and scrubs the flue gas of the absorber have poor gas as it moves upward through the absorption tray and spray zone. The control system automatically adjusts the feed of fresh reagent to achieve Clean Conical an outlet SO2 emission limit or the Flue Gas Outlet Out required SO2 removal efficiency. Absorber tray system Moisture Interspatial Separators/ Our absorber tray system serves the Spray Mist Eliminators Levels dual purpose of providing gas-liquid SO2 and contact for SO2 absorption and more Flue Gas In uniform distribution of flue gas across the tower. The gas rises through the absorber, contacting a froth of slurry on the tray. This action results in efficient contact of gas and reagent throughout the absorber. Gas Distribution Our absorbers use one or two Trays trays depending upon the fuel and Oxidation Zone specified requirements for SO2 Oxidation removal and operating parameters. Air Supply The tray provides uniform gas distribution and effective gas-slurry contact. Table 1 summarizes the benefits of the B&W tray absorber Slurry tower design. Agitators The slurry and the flue gas must be uniformly distributed across the Recirculation Pumps absorber tower’s cross-section for Forced oxidation system shown. 6 7 a) Wet FGD Without B&W Tray Gas Velocity b) Wet FGD With B&W Tray Magnitude (ft/s) 30 28 Outlet 26 Outlet 24 22 20 18 16 14 10 8 6 4 2 0 Mist Eliminator 2 Mist Eliminator 2 Mist Eliminator 1 Mist Eliminator 1 Spray Header 2 Spray Header 2 Spray Header 1 Spray Header 1 Tray Inlet Inlet Slurry Level Slurry Level High gas velocity in spray area is less effective. Uniform gas distribution through spray zone(s) results in more effective and efficient SO2 removal. B&W uses both advanced numerical modeling and physical modeling to design the most efficient wet flue gas desulfurization systems. TABLE 1 EXAMPLE ABSORBER COMPARISON Unit Size: 617 MW SO2 Inlet: 1,100 ppmdv Reagent: Limestone SO2 Removal: 97.6% 2 Trays 1 Tray Open Tower L/G 56 82 108 P, in. wc 10.2 8.2 7.0 Pump Flow, gpm 34,500 50,000 66,000 B&W’s absorption tray provides uniform Fan/Pump Power, kw 6,470 6,560 7,470 gas flow and maximizes SO2 removal. This photo shows a tray after two years of Power Base +90 +1,000 continuous service. Pump/Header Cost Base +$400k +$700k 6 7 Patented interspatial Patented inlet awning headers B&W’s patented inlet awning design prevents the buildup of deposits in Achieving overlapping spray the absorber inlet flue. The awning coverage with an effective spray deflects the falling slurry away header design is critical for optimal from the inlet, shifting the wet-dry SO removal performance. B&W’s 2 interface out into the absorber patented interspatial header away from the inlet flue. This design technology allows the location provides high reliability and lower of two spray headers at the same maintenance costs.