... Gas Heater,Oil Fuel Hot Air Furnace Fuel:1.Solid fuel---like coal, coke.2.Liquid fuel---like diesel, heavy oil.3.Gas fuel---like coal gas, natural gas, liquid gas. ... civil buildings. Types:1.Directly Heating FurnaceThe hot-blast air which generated by the fuel will be used to dry or bake ... rate, the better energy-saving effect of the heating furnace. Industrial Oil Gas Heater,Oil Fuel Hot Air Furnace