Coking coal is a very old practice which involves heating coal up in the absence of air and carbonizing it. Coke used to be used primarily for heating purposes but is now mainly used in the manufacture of steel. This process can be done on the industrial scale or in smaller batches for the hobby metallurgist.
How Is It Done?
To start the coking process, you need an oven capable of handling the heat, over a thousand degrees Celsius, for twelve to fourteen hours. Since you need a way to get the coal into the oven and the coke out of it, you will need very specific types of coke oven doors which can withstand the heat without buckling. This process requires coal with a specific ratio of volatile matter which can be crushed and mixed to get a better ratio. Once the coke has been heated it will need to either be wet or dry drenched to finish the process. Dry drenching involves circulating nitrogen through the chamber to cool the coke. The heat is then removed from the nitrogen by a waste heat boiler and is more environmentally friendly.
Why Do It?
Now that you know how coke cakes are made from coal, it is a good idea to know why. Traditionally, coke was used mainly for heating homes and businesses but has been largely replaced by oil or natural gas. It is also used in the making of steel where coke and iron are put into an oven together where the carbon attaches to the iron to become steel. This is used in both industrial processes and for hobby metallurgists, though coke can be more difficult to come by now than in the past.
Coking coal is a process that has a long history in both heating and steal making. When you are trying to coke coal, you will want to have the right ratio of volatile matter in the coal as well as an oven tough enough to withstand the process and a way to quench the result.