Experimental investigation of NO from pulverized char combustion

ND formation and reduction during pulverized char combustion in the temperature range 850-1150 degreesC have been investigated in fixed-bed combustion experiments. Chars from a high-volatile bituminous coal and an anthracite have been used. Under single-particle conditions the selectivity for NO formation from combustion of char from both fuel types lies in the range 65-100%. The NO formation selectivity under single-particle conditions was observed to he lowest at 850 degreesC, to have values close to 100% at 1050 and 1150 degreesC, and to be independent of O-2, concentration. When conditions deviate from single-particle conditions, net NO formation is significantly lower due to NO reduction taking place simultaneously with NO formation. Rate expressions for NO reduction on char both in the presence and in the absence of O-2 have been determined. For bituminous coal char, these rates are 10-100 times more rapid than values previously reported in literature, but are consistent with reburn-type experiments employing char as Fuel. This discrepancy is mainly attributed to rapid char deactivation prior to measuring of NO reduction rates in previous determinations. Shortly after pyrolysis, the effective NO-char reaction rate for pulverized bituminous coal char in the temperature range 850-1150 degreesC has been found to be given by r(NO) = 6.10(6)m(3)/kg C.s.e(14800/T(K)).[char C].[NO].