THE INFLUENCE OF BLAST-FURNACE GAS COFIRING ON THE COMBUSTION EFFICIENCY OF PULVERIZED COAL

An experimental study was carried out to identify the parameters contr olling the burnout of coal particles when cofired with blast-furnace g as (BFG) under boiler conditions. The experiments were conducted in a bench-scale furnace with a base-fine coal cofired with various amounts of BFG. Results indicate that the burnout problems with BFG cofiring were due to the cooler flame temperatures and shorter residence times associated with the high inert content of BFG, and due to the fall in oxygen partial pressure for the coal particles because of the early co nsumption by BFG. The data also suggest that the base-line coal is a l ow-reactivity fuel. Five candidate coals were tested, and they indicat ed that a significant improvement in carbon conversion could be achiev ed with more reactive coals. One coal was selected and subsequently te sted in the boiler, and yielded consistent results.