But to generate the energy to do that, you have to burn them and heat a working fluid.
Steel is mainly an alloy of iron and carbon. No burning off coal’s impurities to make coke, no steel.
Steel seldom has more than 1% carbon. Other alloying components such as chromium can be up to 20%.
Steel, and , I believe, even most iron today is made in electric arc furnaces, where oxygen in injected to burn off excess carbon. Smoke spewing coke ovens using coal went the way of buggy whips.
Iron is crystalline-—adding a small amount of carbon results in formations of only fine grain crystals, bonded by an amorphous iron glue. The grains provide hardness and the reduction of cleavage planes leads to ductility.
The coke is a relatively cheap oxygen removing agent, a reduction agent with more affinity for oxygen than hot iron. The residual carbon is usually too high for the pig iron to be useful without further processing.