Direct smelting processes types

Direct Smelting. Direct smelting processes use coal directly instead of coke. Several processes are under development which effectively divide the functions of the blast furnace into two separate but connected unit operations. First, the iron ore is prereduced in a shaft furnace or a fluidized bed, depending on the process and the type of ore used. Second, the prereduced ore is charged into a molten bath into which coal and oxygen or air are also introduced. The gases leaving the smelter are used to perform the reduction in the prereduction vessel. 

Some cokeless technologies in use or under development include the Japanese direct iron ore smelting (DIOS) process, in which molten iron is produced directly with coal and sinter feed ore, the HIsmelt process, where ore fines and coal are used to achieve a production rate of 8 t/h using ore directly in the smelter, and the Corex process, which has an integral coal desulfurizing step, making it amenable to a variety of coal types.14... 

Sulfur dioxide can be prepared by several methods, the most common of which is the combustion of sulfur or pyrites (FeS2). A variety of furnaces have been developed for carrying out this reaction. Each type of furnace produces sulfur dioxide of different purities. After production, the sulfur dioxide is normally cooled and compressed to convert it to liquid form. Liquid sulfur dioxide is more easily stored and transported than the gaseous form. Sulfur dioxide is also obtained as the byproduct of a number of industrial operations, especially the smelting of metallic ores. Smelting is the process by which a metal is extracted from its ore by heating in air. Since many ores are sulfides, this process often results in the formation of sulfur dioxide, which can be captured as a byproduct of the operation. Finally, sulfur dioxide can be produced by the direct combustion of sulfur itself ... 

Many large smelting operations that produce veiy high concentrations of sulfur dioxide feed the gas stream directly into a sulfuric acid plant The design and operation of acid plants of this type ate not discussed in this text, as they are considered to represent a separation and chemical manufacturing operation, not a gas purification process. On the other hand, the removal of sulfiu dioxide from dilute smelter oif-gas streams and the recovery of unconverted sulfur dioxide finm the acid plant tail gas constitutes gas purification problems and are reviewed in this chapter. 

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