Emissions Reduction from MSW Combustion Systems Using Natural Gas. Task 2. Pilot-Scale Assessment of Emissions Reduction Strategies. Final Report August 1987-October 1989

摘要

Pilot-scale assessment of natural gas reburning for NOX reduction from municipal solid waste (MSW) combustors has been completed. The initial study was undertaken to investigate the potential for NOX reduction using reburning at furnace temperatures and residence times consistent with typical MSW combustors. Tests investigated the impacts of reburn zone residence time, stoichiometry, and temperature; amount of natural gas, level of NH3 injection; level of flue gas recirculation; and overall stoichiometric ratio. Up to 70% NOX reduction was achieved with reburning under conditions that simulated the firing of 1,700,000 Btu/h of NSW. Subsequently, testing with actual MSW was undertaken at Riley Stoker Corp. on a 2,500,000 Btu/h pilot-scale MSW combustor that incorporates scaled Takuma Co., Ltd., grates and closely simulates commercial operation. The impacts of firing rate, overall excess air level, grate stoichiometry, reburn stoichiometry, reburn residence time, and overfire air/natural gas/recirculated flue gas flows/distribution/injection locations were investigated. These tests demonstrated NOX reductions of 50% to 70% for natural gas additions of 7% to 15% (of the total fuel higher heating value) while low CO and THC emissions were maintained. Injections of natural gas were also found to significantly stabilize the furnace environment. An economic analysis was performed for retrofit applications and showed reburning to be a cost-effective alternative to other NOX reduction techniques including thermal de-NOX. A field test site has been selected and preliminary engineering for the modifications and test plan have been completed.