Ever heard of a Larry car?

http://cokeovens.com/site/photos/

http://www.wvexp.com/index.php/File:Coke-larry-car.png

used in the process of heating up coal to make coke.

What makes coking coal distinct is that it is a fuel with few impurities. Most grades of coke are from 86 to 93 percent pure carbon and produce a clean intense heat when burned. Coke is made by heating coal in a controlled atmosphere, driving off most of the impurities, and leaving a porous structure strong enough to support the iron ore that coke is often used to heat.

http://www.blackdiamondnow.net/black-diamond-now/2013/03/bee-hive-ovens-and-the-production-of-coking-coal.html