WNS Superheated Steam Boiler is full wet back three-pass shell boiler. The structure of oil/gas fired steam boilers includes water tube type and shell type. Water tube boiler has flexible heating surface arrangement, large heat capacity, strong load adaptability, and big occupation. Shell boilers are mostly industrial boilers with low working pressure, which has good adaptability to load change. The cylindrical furnace has good matching with combustion flame of oil (gas) burners, and furnace fullness is high.

1. Design Parameters of WNS Superheated Steam Boiler

Capacity: 2t/h

Rated pressure: 1.0MPa

Feed water temperature: 20Deg.C

Superheated steam temperature: 260Deg.C

Flue gas temperature: 130Deg.C

Design efficiency: 93%

Design fuel type: diesel

2. Structure of WNS Superheated Steam Boiler

It is difficult to arrange superheater on the shell boiler. Since the exhaust flue gas temperature is only 220~250℃, superheater can only be arranged at furnace outlet or the smoke box between second and third pass. Through communication with user, we know that the steam usage is intermittent. After comparative analysis, we decide to arrange the superheater at the smoke box between second and third pass, The flue gas temperature there is relatively low (400~500℃), and the superheater heat transfer temperature and pressure is relatively small.

The second-pass smoke pipe is bare tube, which reduces the heating area of second pass but increases the heating area of third pass. The superheater adopts spiral finned tubes, which increases the heat transfer area of superheater and makes it more compact.

3. Introduction of WNS Superheated Steam Boiler

The fire tube size is φ60×3. Superheater pipe material is 12Cr1MoVG. When the WNS Superheated Steam Boiler is started, the steam in the superheater is small, so the superheated steam temperature is relatively high. With the increase of evaporation, the heat of saturated steam also increases, and superheated steam temperature will gradually decrease to normal level.

We add external steam-water separator in pipe connecting main steam valve and superheater to improve dryness of saturated steam. After improvement, when the boiler runs at rated load, the superheated steam temperature is above 267Deg.C.