Coal Coke is one of the two outputs of a coke oven. The other is Creosote Oil, which is used in making Wooden Ties, which are used to make Stone Railbeds (Note: This is what they are called in the mod, but this may be a problem with the mod, because stone is not one of the materials used for crafting them, should be called wooden railbeds.) Stone Railbeds are what are used to make most basic rails in the Railcraft mod. Coal Coke itself is just like coal, except that it lasts about 2 times as long and has no EMC value. (Note: Coke Coal will not work in RM or DM furnaces.)
You need to put coal in a Coke Oven. Go pound dirt for 3 minutes, then come back to the oven.
Also can be used in stirling engines.