3. What is the main use of coke?

The main use of coke is as a fuel and reducing agent in the production of iron and steel through the process of smelting in a blast furnace. Coke is a porous, hard, and grayish-black solid substance obtained by heating coal in the absence of air to drive off volatile compounds. This process, known as coking or carbonization, produces coke with a high carbon content (typically over 90%).

In the steelmaking process, coke serves several important functions:

1. Fuel: Coke is burned in the blast furnace to provide the high temperatures needed for smelting iron ore into molten iron. It serves as a source of heat energy, allowing the iron ore to be reduced to iron metal through chemical reactions.

2. Reducing Agent: Coke acts as a reducing agent, facilitating the conversion of iron ore (mainly iron oxide, Fe2O3 or Fe3O4) into metallic iron (Fe). In the blast furnace, carbon monoxide (CO) gas is produced by the combustion of coke with oxygen (O2) from the air. The carbon monoxide then reacts with the iron ore, reducing it to iron according to the following reaction: Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g)Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g) This reaction allows the iron to be separated from impurities and formed into molten pig iron.

3. Heat Generation: In addition to serving as a source of heat energy, the combustion of coke also generates carbon dioxide (CO2) gas, which helps to agitate and mix the contents of the blast furnace, ensuring efficient chemical reactions and heat distribution.

4. Chemical Stability: Coke has a high carbon content and is chemically stable at high temperatures, allowing it to maintain its structural integrity and provide consistent fuel and reducing properties throughout the smelting process.

Overall, coke is indispensable in the production of iron and steel, playing a crucial role in providing heat, reducing iron ore, and ensuring the efficient operation of blast furnaces in the steelmaking industry.