Combustion behavior of granulated and pulverized coal in a PCI rig: combustibility and pressure variation analysis

The effect of the coal volatile matter content and particle size has been investigated in a new lab-scale pulverized coal injection rig (PCI rig) in terms of combustion efficiency and pressure variation. Two coals typically used for blast furnace injection (a high and a low volatile bituminous coal) and their blends experienced combustion under pressurized conditions and extremely high heating rates and short residence times such as those experienced by coal particles in industrial process. Combustion tests were conducted for a low volatile coal prepared in the particle size ranges of 25–75 µm, 105–250 µm and 250–500 µm. Burnouts were lower for the larger particle size sample, but the intermediate particle size sample (105–250 µm) yielded similar conversion to that of the finer sample. The burnouts of the high and low volatile coal, as well as those of their blends were proportional to the volatile matter content of samples in the test conditions. The measurement of pressure variation in the reactor chamber indicated a displacement in the beginning of reactions to longer times as larger was the particle size of coal. The high volatile coal reached the maximum pressure variation earlier than the low volatile one and the combustion of this coal in the blends may have anticipated the reaction of the low volatile coal portion in the blends.