Iron Smelting with Non-Coking Coals in Low Shaft Furnace

抄録

In relation to classical reserves of high grade iron are in India, the reserves of good metallurgical grade of coking coals are extremely limited and that too confined to in the Bengal-Bihar belt. The development of small and medium scale iron and steel plants depends on the exploitation of sub-standard raw materials particularly the fuel unsuitable for conventional smelting in big blast furnaces of a million tonnes integrated iron and steel complex. The Low Shaft Furnace Pilot Plant installed at the National Metallurgical Laboratory, Jamshedpur (India) is designed to operate on sub-standard raw materials and non-metallurgical fuels for iron smelting.
In 5-6 years of extensive and painstaking trials, a great variety of raw materials have been investigated on a comprehensive scale. It has been established that technological, operational and economic considerations preclude the adoption of a single stage process based on the smelting of single component burden of ore-fuel-limestone briquettes. The operational complexities and non-recovery of potential by-products have rendered the direct utilization of non-coking coals for iron smelting as lumpy bedded charge also impractical. The use of low temperature carbonized coke made from noncoking coals has enabled effective furnace operational control and uniformity of pig iron output of consistent composition.
Carbon saturation of pig iron in initial trials was found to be low which depended on the basicity and MgO content of the slag. The effects of changes in the basicity of slag on carbon, silicon of pig iron, sulphur partition and on technical aspects of smelting, flux rate and fuel rate were investigated. The effects of particle size of raw materials and the rate of blowing, on top gas temperature, CO/CO² ratio, fuel rate and dust loss were also comprehensively studied. Dolomite additions were found to improve the slag fluidity but somewhat adversely affected sulphur partition.
It has been established that iron smelting in a low shaft blast furnace with low temperature carbonized coke can be successfully adopted in areas where coking coals reserves were limited.