Effect of waste and alternative fuels on blast-furnace operation

Abstract

Ninety-eight percent of the pig iron produced in the world is made in blast furnaces. Pig-iron smelting is presently being impacted by a serious shortage of coking coals. Moreover, the production of coke used in the smelting operation has an adverse effect on the environment. One method of partially replacing coke in the smelting operation is to inject hydrocarbons into the blast furnace. The injection of hydrocarbon through the tuyeres alters the mass- and heat-transfer conditions inside the furnace and increases the volume and hydrogen content of the hearth gases and top gases. The hydrogen content of the gases depends on the value of the C/H2 ratio in the fuel that is injected. All these changes decrease the amount of direct reduction that iron undergoes in the furnace. This article presents results from model calculations that took into account the complex effect of injected hydrocarbons on reduction and heat exchange in a blast furnace. The models were used to quantitatively estimate the amount of reduction that takes place and to determine the value of a coefficient which characterizes the replacement of coke by injected fuel. The calculations that were performed make it possible to predict changes in coke consumption in a blast furnace when it is injected with liquid hydrocarbons.