High-Efficiency Superheater and Reheater for Power Stations

It reheats steam after turbine expansion to improve cycle efficiency.

The Steam Superheater is a coil type heat exchanger which is used to produce superheated steam or to convert the wet steam to dry steam, generated by a boiler. It is different from a boiler in a way that, boiler utilizes both sensible heat as well as latent heat to convert water into steam while superheater utilizes only sensible heat to superheat the steam in order to increase its enthalpy.

The platen superheater is composed of steel pipe with outer diameter of 32 ~ 42mm and header, which is generally suspended at the upper part of furnace or furnace outlet. The number of tubes in each screen is generally 15 ~ 30, which is determined according to the required steam flow rate.

The outside diameter of the pipe is generally 30-60mm. The convection superheater is the most commonly used, and the serpentine tube type is adopted. It has a relatively dense tube group, which is arranged in the flue of 450-1000 ℃ flue gas temperature, and is subject to the transverse and longitudinal erosion of flue gas. The flue gas mainly transfers heat to the pipe by convection, and some of it absorbs heat by radiation.

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. 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.

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.

Superheater is to increase the temperature of the steam above its saturation point.

Reheater is basically a superheater that superheats steam exiting the high-pressure stage of a turbine. The reheated steam is then sent to the low-pressure stage of the turbine. By reheating steam between high-pressure and low-pressure turbine it is possible to increase the electrical efficiency of the power plant cycle beyond 40%. The reheat cycle is used in large power boilers since it is feasible economically only in larger power plants.

• HDB has extensive experience using their remaining useful life analysis system to predict the lifespan of tubes.
• The system measures the oxide and wall thickness of the tube during an on-site non-destructive test and this is used to calculate the remaining useful life.
• HDB developed the oxide measuring technology in 1991 and it is now used as the standard throughout the world.

• The function of the superheater in the thermal power plant is to remove the last traces of moisture (1 to 2%) from the saturated steam coming out of boiler and to increase its temperature sufficiently above saturation temperature.
• The super-heating heating raises overall overall cycle efficiency efficiency as well as avoids too much condensation in the last stages of the turbine which avoids the blade erosion.
• The heat of combustion gases from furnace is utilized for the removal of moisture from steam and to superheat the steam.
• Super-heaters usually have several tube circuits in parallel with one or more return bends, connected between headers.