In China the largest number of water tube boiler, water and fire tube boiler and combustion boiler are almost the same as the popular boilers in the word except water tube boiler which owns Chinese characteristics. At present the water fire tube boiler still accounts for a large proportion. Through the improvement of technology to further improve, it will still be one of the main forms of industrial boiler in China.

New type water fire tube pot-shell boiler development has experienced twenty-eight years: 1983 at Harbin Institute of Technology after a lot of research, the old type water fire tube pot-shell boiler (the first generation water fire tube boiler) developed into the new type. In 1988 the former Ministry of Machinery Industry Beijing Electric Study on Technology and Economy continued to develop new type. Since 1993, Shengchangzhiguang Boiler Design Research and Development Center has been expanding Varieties. Because this type of boiler has many outstanding advantages, it is possible to be widely used in production and heating in our country, and the annual output and its total capacity are more than any other type of boiler furnace, especially the 40 steam-ton boilers and smaller than 40 steam-ton boilers owns a larger share. In addition, the technology and products have also spread to foreign countries. At present, the capacity of this type of boiler has been developed to 100 steam-ton, the pressure is generally not more than 1.6MPa.

In order to increase the boiler’s capacity and it’s pressure and further improve the boiler’s performance, a combination of thread pipe tube boiler has emerged. The new type water fire tube pot-shell boiler changed the large diameter flat pot-shell into several small diameter vertical pipes.

The combined thread pipe tube boiler continues to use the following advanced technologies which are tested for a long period of practice in manufacturing the new type water fire tube pot-shell boiler:

1、thread pipe tube

Threaded pipe in our country are widely used in new pot-shell boilers (coal, oil - gas, burning biomass), waste heat boiler, stove, and other fields, and it is also widely used on the economizer and air preheater. The reasons for this are: : (1) The efficient heat transfer and simple processing, (2) The threaded pipe covers little dust and the threaded pipe heat transfer performance basically remains unchanged as long as the designed smoke speed is reasonable and operation runs smoothly.

2、The return water ejection

The return water ejection ’s (hot water operated) structure is simple and its flow resistance is small, which can obviously increase the water speed of the heated surface, and the heated surface needs not protecting by cutting power supply. This kind of technology is not only widely used in water and fire tube boiler shell boiler but also is used in water tube boiler.

3、Simple separation of steam and water

Steam and water can be separated by gravity by using a simple structure, which can provide a very low temperature steam. This kind of technology has been widely used and verified by experiments at home and abroad.

4、self-support

Self-support can obviously save steel. This kind of technology can be widely used in new type water fire tube pot-shell boiler and in water tube boiler.