"Oct. 1989." "EPA/600-S7-89-003."

Major problems facing the conversion of oil - and gas-fired boilers to coal are derating, inorganic impurities in coal, and excessive pollutant formation (NO[subscript x] and SO[subscript x]). To alleviate these problems a combustion system is desired that has a high firing density, separates and retains fly ash, and is adaptable to viable pollution control technologies. The Vortex Containment Combustor (VCC) has been designed and tested with these objectives in mind. An extensive literature review and the testing of two candidate isothermal systems preceded the design and construction of a bench-scale VCC. Coal combustion tests were performed on the VCC to evaluate its performance in terms of ash retention efficiency, coal burnout, combustion stability, and slag and ash deposition. Results were very promising for both retention efficiency and combustion stability. Fuel injector modifications improved internal slag deposition conditions while maintaining acceptable carbon burnout levels. NO[subscript x] control by staging and reburning technologies was evaluated in the VCC, along with sorbent injection for the control of SOb2s emissions. Both staging and reburning were shown to be effective techniques for reducing NO[subscript x] emissions in the VCC. Improvements in the sorbent injection approach are required to obtain an acceptable degree of SOb2s reduction. Based on particle force balance expressions, scaling criteria have been established for the VCC. Also, the effect of scaling on system pressure drop and heat release on retention efficiency has been evaluated. The VCC has performed successfully at bench-scale. Evaluation at a larger scale would be the next step toward bringing the VCC concept to fruition.