What is the main purpose of using coke in the refining of iron-ore?

The main purpose of using coke in the refining of iron ore is to reduce the oxygen content in iron ore, a process known as reduction. When heated in a blast furnace, coke serves as a carbon source that reacts with the iron ore (primarily composed of iron oxides) to remove oxygen. This chemical reaction transforms the iron oxides into molten iron and carbon dioxide.

During this process, the coke undergoes combustion to produce the necessary heat while simultaneously providing the carbon needed for the reduction reaction. The production of carbon dioxide as a byproduct is an essential aspect of this process, indicating the successful removal of oxygen from the iron ore.

The other options do not accurately capture the primary role of coke in this context. Increasing the temperature of the ore does occur as a result of coke combustion; however, that is not its main purpose. Strengthening the iron ore structure is not relevant to the function of coke since the strength of iron ore is not enhanced during the reduction process. Lastly, enhancing the appearance of the iron does not pertain to the function of coke, as its role is strictly related to the chemical transformation during the smelting process, not the aesthetic qualities of the final product.