Use of Coal in Direct Ironmaking Processes
AUTHOR: Anne M Carpenter
DATE: September 2004
The main route for production of iron for steelmaking is via the blast furnace, using metallurgical coke as the reductant. Concerns over the limited resources and high cost of coking coals, and over the environmental impacts of coking and sinter plants are driving steelmakers to develop alternative ironmaking processes that can use non-coking coals to reduce iron ores directly. This report examines some of these alternative ironmaking processes.
It begins by outlining the two major routes of steel production before discussing the utilisation of the alternative iron products in steelmaking, and the likely market opportunities for the technologies. This is followed by a discussion of some direct reduction processes which produce a solid product, and smelting reduction processes where the product is liquid iron. The emphasis is on processes that are in commercial operation or at the demonstration stage. The influence of the raw materials (coal, iron ores and steelmaking wastes) on the performance of the technologies is then described.
Although each of the processes can operate with a wide range of coals, optimum performance is only achieved using coals with a limited range of properties. Energy consumption of the processes and utilisation of the offgas from the smelting reduction technologies are covered. The smelting reduction processes that produce considerable quantities of offgas are reliant on the credits for its fuel value to make the process economically viable. Finally, environmental aspects (emissions, liquid effluents and waste utilisation) are discussed.