Carbon Steel/Stainless Steel Boiler Heat Exchanger Boiler Superheater and Reheater Tube Coil

                  Carbon Steel/Stainless Steel Boiler Heat Exchanger Boiler Superheater and Reheater Tube Coil

Product Description
 

For large boilers in power stations, superheaters and reheaters account for a big proportion in the total heating surfaces, they are to be arranged in the areas where smoke is with higher temperature. To improve the efficiency of thermal circulation in power stations, it is needed to improve the original parameters f steam gradually, the increase of steam pressure requires the corresponding increase of temperature for superheated steam, or the humidity of large stage exhaust of steam turbine will be too high, which will influence its safety. Thus, the steam flowing through superheaters and reheaters are high temperature steam, their heat transfer performance is quite bad, which determines that tube wall temperatures of superheaters and reheaters are high.

Functions and characteristics of superheater and reheaters

Superheaters and reheaters are important parts for the heating surfaces, used to increase steam temperature, aiming to improve steam enthalpy and further to increase the thermal circulation efficiency for power station.

Superheaters work to heat surnatured steam to superheated steam with a certain tempetature. When boiler loads or other working conditions change, it is necessary to make sure superheated steam temperature to be normal, and within allowable range of temperature variation.

From the thermal circulation in power station, the original parameters of pressure and temperature is higher, the thermal efficiency of circulation is better, or the steam humidity of the steam turbine rear is too high, influencing its safety. While the superheaer steam temperature is limited by metal materials, at present, due to limitation of metal materials, superheated temperature for most power station boilers are still within the range of 540-555 dgrees, and to avoid the steam humidity of blade of steam turbine rear too big, thus middle reheating system is applied.

Functions of reheaters are to heat exhaust of steam turbine high pressure cylinder to the reheated temperature which is close or equal to superheated temperature, and then send them to middle pressure cylinder and low pressure to expand and work to increase the dryness of blace of steam turbine rear. Usually, the pressure of reheated steam is one fifth of that of superheated steam. Application of reheating system can increase the thermal efficiency for power stations by 4-5%.

So far in our country, units with capacity over 125mw all apply one time middle reheating system. Double reheating can increase again the thermal efficiency of circulation by 2%, but the system is very complicated, it is not applied for national units, but it is common for large boilers overseas.

Differences

Workshop