Temperature, velocity and species profile measurements for reburning in a211 pulverized, entrained flow, coal combustor

摘要

Nitrogen oxide emissions from pulverized coal combustion have been and will211u001econtinue to be a regulated pollutant for electric utility boilers burning 211u001epulverized coal. Full scale combustion models can help in the design of new 211u001eboilers and boiler retrofits which meet emissions standards, but these models 211u001erequire validation before they can be used with confidence. The objective of this 211u001ework was to obtain detailed combustion measurements of pulverized coal flames 211u001ewhich implement two NO reduction strategies, namely reburning and advanced 211u001ereburning, to provide data for model validation. The data were also compared to 211u001ean existing comprehensive pulverized coal combustion model with a reduced 211u001emechanism for NO reduction under reburning and advanced reburning conditions. The 211u001edata were obtained in a 0.2 MW, cylindrical, down-fired, variable swirl, 211u001epulverized coal reactor. The reactor had a diameter of 0.76 m and a length of 2.4 211u001em with access ports along the axial length. A Wyodak, sub-bituminous coal was 211u001eused in all of the measurements. The burner had a centrally located primary fuel 211u001eand air tube surrounded by heated and variably swirled secondary air. Species of 211u001eNO, NO(sub x), CO, CO(sub 2) and O(sub 2) were measured continuously. Aqueous 211u001esampling was used to measure HCN and NH(sub 3) at specific reactor locations. 211u001eSamples were drawn from the reactor using water quenched suction probes. Velocity 211u001emeasurements were obtained using two component laser doppler anemometry in back-211u001escatter mode. Temperature measurements were obtained using a shielded suction 211u001epyrometer. A series of six or more radial measurements at six or more axial 211u001elocations within the reactor provided a map of species, temperature, and velocity 211u001emeasurements. In total, seven reactor maps were obtained. Three maps were 211u001eobtained at baseline conditions of 0, 0.5 and 1.5 swirl and 10% excess air. Two 211u001emaps were obtained under reburning conditions of 0.78 stoichiometric ratio and 211u001e1.5 swirl and 0.9 stoichiometric ratio and 0.5 swirl. And finally, two maps were 211u001eobtained under advanced reburning conditions both at the same operating condition 211u001eof 1.05 stoichiometric ratio in the reburning zone followed by ammonia injection. 211u001eNumerous effluent measurements were obtained to study the affect of natural gas 211u001einjection location, stoichiometric ratio, and injection velocity on effluent NO. 211u001eFor advanced reburning, effluent measurements were obtained for a similar matrix 211u001eof operating conditions with the additional variable of ammonia nitrogen to 211u001enitrogen in NO or nitrogen stoichiometric ratio (NSR).