MAXIMUM INJECTION RATE OF PULVERIZED COAL INTO BLAST-FURNACE THROUGH TUYERES WITH CONSIDERATION OF UNBURNT CHAR

Experiments concerning the combustion and consumption of pulverized coal (PC) with high volatile matter content were conducted using an experimental apparatus capable of simulating the heat transfer and reactions in the lower part of the blast furnace. First, the calculating method of PC combustion efficiency in the raceway was proposed and the effects of blast conditions on the efficiency were investigated. Secondly, the calculating method of PC consumption efficiency at the apparatus top was proposed and the effects of blast conditions on the efficiency were investigated. Thirdly, the unburnt char volume accumulating in the apparatus was measured and the limited char volume not causing the permeability deterioration in the apparatus was found. As a result of these analyses, the following conclusion was obtained concerning the maximum PC injection rate: Under the conditions of blast temperature of 1 300-degrees-C, blast humidity of 5 g/Nm3 and oxygen enrichment of 2%, the limit PC injection rate is over 245 g/Nm3 (240 kg/t-pig) in the actual blast furnace that prevents the discharge of char from the furnace top and does not cause the permeability deterioration even when char accumulates in the furnace.