Coal Char Reactivity and Structure - Effects Affecting PCI Operation in Blast Furnace

摘要

Coal injection into the blast furnace is an effective method to reduce BF coke consumption and therefore cokemaking related environmetnal problems. Despite its obvious economic and environmental advantages, some coal related technical problems remain. During operation, pulverised coal is directly injected into the blast furnace through the tuyeres. Since the residence time available for coal pyrolysis and char combustion in the raceway is extremely short (about 20ms). it is likely that unburnt char will be carried from the raceway, especially at high PCI rates. This could lead to accumulation of unburnt char at higher level in the blast furnace which may result in severe operational problems, such as reduced permeability, undesirable gas and temperature distribution and possible handing of the burden. Therefore, keeping the amount of unburnt char in the blast furnace stack under a reasonable level while increasing PCI ratio is always an aim of PCI operation.