The original coke ovens were being used to convert bituminous coal into industrial use coke. It was suggested that the coke mined was a clean burning fuel but today it is a well-known fact that that is otherwise. It is also possible that if they were being used at all, coke oven doors would not have been effective in containing high pollution levels. That stands to reason, given that today’s available technologies were not known then.
The clean burning coke fuel is still being used in the smelting of iron ore. Hence the term ‘coking’. Originally, the coal was shoveled into the coke ovens. These ovens were insulated with layers of dirt. And then they were ignited. Doors in use then were sealed with bricks and mud. Coal would be let burning with very little oxygen to spare for a few days. Hot temperatures of over three thousand degrees were not uncommon then.
Volatile chunks of coal combusted. Gaseous escape occurred through holes in the oven’s roof. The remaining coke became pure carbon. Its byproduct was termed slag. Slag was an unwanted byproduct and would be laid to waste. But later it became useful for the making of bricks, mixing cement and producing fertilizer. Slag laying near the coking site looks like coarse rocks. They are black or gray in color. Variations of slag come across as a glassy substance which is used to coat bricks inside of the coke oven.
Today’s coke oven doors are essential in order to contain as much of the carbon emissions as possible. This is important because left to filter out into the earth’s atmosphere in the form of gas it becomes extremely damaging to that environment. So true that coke and the ovens that hold it have had a long and dirty history.