The TRW project will develop an acid rain precursor control technology for retrofit applications. One of the main objectives of this project is to demonstrate that this slagging combustor technology can result in replacement of oil with coal with no loss in unit capacity while meeting the emission requirements normally achieved when firing with oil. Another key objective is to demonstrate that TRW'S slagging combustor can burn low-sulfur and commercially washed high-sulfur eastern bituminous coals and still satisfy the New Source Performance Standards (NSPS) for utility boilers and thereby provide for control of acid rain precursors. The two sites to be utilized for this project are the Orange and Rock land Utilities Company Lovett Station Unit No.3 located at Stony Point, New York, and TRW's Cleveland, Ohio, industrial demonstration site. The Lovett Station boiler, a commercial operating 69 MWe unit will be retrofitted with four 160 MMBtu/hr combustors and necessary ancillary equipment, including limestone injection and dust collection systems. The slagging combustor system (SCS) at Cleveland, currently installed on a 40 MMBtu/hr industrial boiler, will be modified to demonstrate waste sorbent recycle and flue gas humidification as an approach to reduce sorbent consumption and maximize S02 capture. The waste sorbent recycle system will be used to minimize fresh sorbent requirements for a given level of sulfur capture. It will be used to optimize solid waste recycle rates in order to achieve the lowest overall calcium-to sulfur ratio while meeting NSPS requirements for S02 removal. The humidification system, which will be installed upstream of the baghouse, will be used to determine the cost effectiveness of humidification. The overall thrust of the project at the Cleveland site will be to optimize the process chemistry for S02 removal so as to establish hardware and operating parameters for the utility-scale demonstration at the Lovett Station in New York. At the Lovett plant, limestone will be injected at or near the slagging combustor outlet and recycled lime wastes will be injected into the system as appropriate to enhance sulfur capture and improve overall process economics. A key objective to be accomplished at this site will be to confirm the expected high capture of S02 in the boiler. Additionally, operation of the four 160 MMBtu combustors will demonstrate the operability, reliability, and scale-up of the SCS on a utility-scale boiler. Both sites will use low- and commercially washed high-sulfur eastern U.S. coals in their test programs. Sulfur capture rates of up to 60% and 90% on low- and commercially washed high-sulfur coals, respectively, are expected to be demonstrated. The reduction of NOx emissions to the O.3Ib/MMBtu level will also be demonstrated. Typically, coal-fired boilers produce O.7Ib/ MMBtu of NOx or more.