Alloy Steel Superheater And Reheater For Pulverized Coal Boilers With Natural Circulation

In general, steam heated in high pressure superheater is named superheated vapour, the steam heated by reheater is called reheated vapour. The parameter of reheated steam is relating with economy of thermal circulation. Generally, the pressure of reheated steam is about one fifth of that of superheated steam, and the temperature of the former is almost the same as that of the latter. For example, in our nation for boiler with 125MW, 400t/h, the parmameter for superheated steam is 133.7Mpa and 555 degrees; the inlet and outlet pressure of reheated steam is 2.5/2.35MPa, their temperature is 555 degrees, too.

For boilers with 200MW, 670t/h, the parameter of superheated steam is 13.7MPa, 540 degrees; the inlet and outlet pressures are 2.7/2.5Mpa, and the temperature is also 540 degrees. For subcritical pressure control circulation boilers with 300MW, 600MW, superheated steam parameter is 18.27Mpa, 540 degrees; the inlet and outlet pressures are 3.83/3.63MPa, the temperature is also 540 dgrees. Application of steam reheating system can increase the thermal economy for power stations by 4-5%. In our country, units with capacity over 125MW all apply one time middle reheating system, and overseas, two times middle reheating systems are applied for some units with higher parameters.

Principle

• Principle of superheater is similar to steam generating tubes of boiler.

• The hot gases at high temperature sweep over superheater tubes and raise the temperature of steam which magnitude depends upon exit gas temperature leaving the superheater and gas velocity.

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.

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.

Differences