Investigation on Possibility of Further Increasing the Rate of Pulverized Coal Injection without Lowering Unilization of Coal Injected in Blast Furnace

Sampling of burned coal residue directly from the raceway of two Chinese BF reveals that at the current rate of anthracite injection up to 140 kg/tHM or 27% of the total fuel coal could not be burned completely in the raceway although devolatilization and combustion take place early in the blowpipe. This does not interrupt the smooth running of the furnaces.
From laboratory study on kinetics of coal powder combustion in two bench-scale combustion furnaces, one of which preheats the air blast by electrical resistance, the other by plasma torch, rate of combustion is found almost inversely proportional to grain size of coal; it increases with increaseof blast temperature up to 1475℃; oxygen enrichment up to 40% of the blast is very effective;with decrease of coefficient of surplus air to less than. 1.2-1.3 the rate of combustion decreases abruptly, while whirling or rotation of the blast accelerates the combustion rate.
Melting behavior of dropping zone slag mixed with ash of injected coal or partially burned coal residue seems not to be the limiting bottle-neck to high rate of coal injection. Investigation on effect of injection position, angle and shape of coal lance on the two phase gas-solid distribution by shock-wave tube and schlieren method reveals remarkable influence of these factors on uniform distribution of injected coal particles in the combution air stream.