The water pipe and the fire pipe are defined by the difference in the medium inside the pipe. The water pipe is the water in the pipe. The water in the pipe is heated by the external flue gas convection / radiation heat transfer. The fire pipe is the smoke in the pipe to heat the flue gas. The medium outside the tube is used to achieve heat exchange. The fire tube boiler has a simple structure, large volume of water and steam, good adaptability to load movement, and lower requirements on water quality than water tube boilers. It is mostly used for production processes and domestic heating in small enterprises. The heating surface is easy to arrange and has good heat transfer performance. It can be used in large capacity and high parameters in the structure. However, higher requirements are imposed on water quality and operating levels.
(1) The water pipe boiler has a wide range of pressure adaptation, which can break the pressure limit and meet the steam supply requirements of 2.5MPa and above. Fire tube boilers are limited by material wall thickness and pressure and are used for pressures below 2.5 MPa.
(2) The fire tube boiler is a shell-shell boiler. Due to the limitations of existing boiler manufacturers’ equipment and tooling, the manufacture of too large fire tube boilers is difficult to penetrate, usually below 35t / h. Water tube structure boilers can realize large-scale boilers, and boilers above 35t / h usually use water tube structures.
(3) The fire tube boiler has the characteristics of compact structure. Under the same output, the size and equipment weight are lower than the fire tube boiler. Due to the shrinkage of the water tube boiler, there is more space for the overlap device, so the water tube boiler takes up the relative flexibility of the boiler room.