Effects of Fuel Properties on Ignition Characteristics of Parallel-Bias Pulverized-Coal Jets

To further understand the bias combustion behavior of new coal used for horizontal bias combustion and obtain its characteristic parameters, combustion experiments were conducted in a 250-kW pilot-scale bias combustion simulator; multiple research measurements of flame spectra, combustion temperatures, and burnout rates of residual solids were used. Bituminous coal from Australia, sub-bituminous coal from Indonesia, and a blend of these coals were tested. The effects of the raw-coal equivalent moisture (RCEM), pulverized-coal fineness (PCF), and coal type on the ignition characteristics of parallel-bias pulverized-coal jets in a reducing atmosphere were investigated. The results indicate that, with decreasing RCEM and PCF, the standoff distance gradually decreased, the flame stability gradually increased, the burnout rate gradually increased, and the ignition characteristics gradually improved. The RCEM had negative effects on ignition in the early stage but positive effects during subsequent combustion. Sub-bituminous coal exhibited a homogeneous-heterogeneous combined ignition mode as the RCEM increased. Bituminous coal changed to homogeneous ignition from homogeneous-heterogeneous combined ignition as the PCF increased. For the sequence bituminous coal, blended coal, sub-bituminous coal, the standoff distance gradually increased, the flame stability gradually decreased, the burnout rate gradually decreased, and the ignition characteristics gradually worsened. When the RCEM of the primary air/pulverized-coal jets reached the moisture content of each raw coal sample, the ignition mode was homogeneous for bituminous coal and a homogeneous-heterogeneous combination for sub-bituminous and blended coals. The ignition characteristics of the blended coal resembled those of sub-bituminous coal, and the burnout characteristics of blended coal resembled those of bituminous coal.