Most "coal fired" boilers produced are large watertube units. (smaller units have been produced in the past) Firetube boilers (the other type) are typically Natural gas, propane or Fuel oil fired.
Coal fired boilers are in less demand these days...... Natural gas is cheap, and in the USA, gas burners that will use this fuel and meet NOX emmisions are available.
Babcock & Wilcox, Foster Wheeler and Combustion Engineering are the major US vendors of such boilers. "Pulverized coal" burning units are most often in use, Bear in mind that the boiler and combustion systems MUST BE designed for the type of coal that you intend to use as a fuel...
Many "used" units are available for purchase on the international market..
