The usage of the coal is very extensive. For each particular process, there is always a better method to burn some kinds of coals than the others. Each application of the combustion of coal is an individual problem. This problem involves not only the single factor of burning of coal but also the factors of the economy, materials, and manufacture. An efficient burning process is not always the suitable one to be used. On some practical field of coal combustion the testing, or trial method serves very satisfactorily for finding the best firing method. The boiler and furnace testing method applied in the steam power plant is an excellent example. However, there is an important thing in common in all the coal firing processes which is the burning of coal. An understanding of the fundamental characteristics of the coal burning is obviously very helpful to the practical usages, especially to the design of a new process.