As a metallurgical engineer with extensive experience in the field, I can provide a detailed explanation of why coke is preferred over coal in various industrial processes, particularly in the production of iron and steel.

Coke, a derivative of coal, is a high-carbon content solid fuel with a very low impurity level. It is produced through a process known as destructive distillation, where bituminous coal is heated in the absence of air, causing it to decompose and release volatile gases. This process leaves behind a solid residue, which is coke. The low impurity level of coke is one of its key advantages over coal.

Firstly, the high carbon content of coke makes it an efficient fuel. When coke is burned, it releases a significant amount of energy, which is critical in the high-temperature processes required for smelting, such as the production of iron from iron ore.

Secondly, the low impurity content of coke is essential for maintaining the quality of the final product. When coal is used as a fuel, its higher impurity content can lead to the contamination of the molten iron. These impurities can include sulfur, which can form sulfur dioxide when burned, and various metals that can dissolve into the iron, affecting its properties.

Thirdly, coke serves as a reductant in the blast furnace. The carbon in coke reacts with the iron oxides present in the iron ore, reducing them to metallic iron. This reduction process is essential for the production of iron and cannot be effectively achieved with coal due to its impurities.

Fourthly, the physical properties of coke are also advantageous. Coke is porous and has a high strength, which allows it to maintain its structure in the harsh conditions of the blast furnace. This structural integrity is important for supporting the weight of the materials above and for allowing the passage of gases through the furnace.

Fifthly, the use of coke can improve the efficiency of the smelting process. The high energy release and reductive capabilities of coke can lead to faster smelting times and higher yields, which are economically beneficial for the industry.

Lastly, environmental considerations also play a role. The use of coke can result in less air pollution compared to coal, as it produces fewer harmful emissions when burned.

In summary, coke is used instead of coal primarily due to its high carbon content, low impurity levels, reductive properties, favorable physical properties, and environmental benefits. These factors make coke the preferred fuel and reductant in the smelting of iron and steel.

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Coke is a fuel with very low impurities and high carbon content. Usually coke is obtained by destructive distillation of bituminous-coal. So, if coal is used in smelting instead of coke the higher impurities content of coal will real with the molten iron formed and would result in undesirable products.read more >>