Development of a Vortex Containment Combustor for Coal Combustion Systems

摘要

The report describes the development of a vortex containment combustor (VCC) for coal combustion systems, designed to solve major problems facing the conversion of oil- and gas-fired boilers to coal (e.g., derating, inorganic impurities in coal, and excessive formation of NOx and SOx). The system would: have a high firing density, separate and retain fly ash, and be adaptable to viable pollution control technologies. An extensive literature review and tests 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. NOx control by staging and reburning technologies was evaluated in the VCC, along with sorbent injection for the control of SO2 emissions. Both staging and reburning were effective in reducing NOx emissions in the VCC. Improvements in the sorbent injection approach are required to obtain an acceptable degree of SO2 reduction. Based on particle force balance expressions, scaling criteria have been established for the VCC.