Carbon/Stainless Steel Superheater In Boiler For Natural Circulation Coal - Fired CFB Boilers

For power plant boiler, it is a crutial way to increase thermal economy of thermal power station by improving parameter of superheated steam. The increase of superheated steam parameters are limited by metal materials. The design of superheaters must make sure that the temperature of outer wall of heating surface pipes is lower than allowable temperature of oxidation resistance of steel, and meanwhile make sure its mechanical strength. with the development of metal material used in boilers, pwoer station boilers in our country already generally apply high pressure, high temperature(9.8MPa, 540 degrees) and superhigh pressure parameters(13.7 MPa, 540 and 555 degrees), and have developed subcritical pressure parameters(16.7MPa, 540 and 555 degrees). Now lots of boilers apply supercritical pressure parameters(24.5MPa, 540-570 degrees), and even very few units apply higher pressure and temperture parameters.

Details

• Superheating raises overall efficiency as well as avoids too much condensation in last stages of turbine which avoids blade erosion.

• The heat of combustion gases from furnace is utilised for removal of moisture from steam and to superheat the steam.

• Super-heaters ususlly have several tube circuits in parallel with one or more return bends,connected between headers.

• Heat from the hot gases to the vapour in the surperheater is transferred at high temperatures.

• Therefore promary section of superheater is arranged in counterflow and secondary section in parallel flow to reduce the temp.stressing of the tube wall.

Functions and characteristics

functions of superheaters 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.

Application

use for heating saturated steam, steam temperature could be up to 900 degree C.

Superheater Capacity Upgrades to Increase Power Generation

Send us required technical data, such as steam capacity, presure, required temperature etc. We will design accordingly.

Differences