OXYGEN-ENRICHED COMBUSTION OF A POWDER RIVER BASIN BLACK THUNDER COAL FOR NO, REDUCTION IN A CYCLONE FURNACE

摘要

Pilot-scale emissions performance results are reported for the combustion of a western sub-pituminous Black Thunder coal with air and oxygen-enriched ail in a cyclone furnace. Unstaged firing ofthe high-moisture and iow-nitrogen content Black Thunder coal at 17% excess air (1.17 stoichiometry) produced 759 ppmv NO_X (1.04 Ib/million Btu) and 27 ppmv CO, Without oxygen enrichment, the lowest cyclone stoichiometry for continuous slag tapping was 0,70. Under this condition and 1.17 overall stoichiometry, the NO_X concentration was 108 ppmv (0.148 1b/million Btu), and the CO level was 24 ppmv. Partial substitution of secondary air flow to the cyclone combustor with oxygen was tested under staged operation using up to 10% O_2 enrichment and at an overall stoichiometry of 1.17. Oxygen enrichment of the cyclone comhustor extended the lower stoichiomctry limit while maintaining good slag tapping, At 1.17 overall combustion stoichiometry, the average NO, concentration was 95 ppmv (0.126 Sb/million Btu), and the average CO was 17 ppmv when the cyclone was staged to 0.66 stoichiometry and enriched with pure oxygen. The optimum emissions results represent 88% NO_x reduction from the uncontrolled operation.