Drum type boilers and boilers whose drums are not heated outside the fire side are of double drum, single drum and multi drum type, and the drums are of horizontal and vertical type.

The boiler is divided into "boiler" and "boiler". "Boiler" is a pressure part containing water and steam, which heats, vaporizes and separates water from steam. "Boiler" is a place for fuel combustion or other heat release, with combustion equipment, combustion chamber furnace and heat release flue. The heat conversion process is carried out between the boiler and the boiler, and the interface between heat release and heat absorption is called the heating surface. The boiler heats water into steam. In addition to the boiler and furnace, there are other auxiliary equipment such as framework, platform, escalator, combustion, slag discharge, flue duct, pipeline, furnace wall, etc.