Clean Energy Steam Boiler Replacement Steam Super heater Reheater power plant boiler
Boiler Replacement Reheater In Design
1. In designs where the reheater surface is kept in a more convective region, it is possible to control the reheater temperature by simple mechanisms like increasing or reducing the flue gases flowing over the sections.
2. As the convective heat transfer coefficient depend more on the mass flow, and in turn the velocity, this method has been adopted by designers successfully. This method is most often used in wall fired units. Here the second pass of the boiler is divided in to two parallel paths up to the economizer. The two parallel paths are so designed to have a normal one third and two third ratio of flow area.
3. The two third ratios of area being adopted for low temperature superheater surface and the one third flow area for the reheater surface. Dampers at the bottom of this flue gas passage are used to control the flow.
4. A set of dampers is kept in the bigger area so that closing of these dampers will divert flue gas to the smaller area side where the reheater surface is. This increases the pickup in the reheater steam and thus the outlet temperature of the reheater is increased.
5. Reducing the flow by opening the damper in the other parallel path will reduce the flue gas flow through the reheater section and thus reduce the reheater steam outlet temperature. Even though the logic of this design is simple, the construction and maintenance aspect suffer considerably when coal and low grade fuels are used.
1. Therefore the number of reheat stages can not be many as the pressure drop will reduce efficiency of thermal cycle.The steam pipes and reheater coils are to be so designed to limit the drop to 2–3%.
2. The control valves in reheat steam path is not desirable.Systems using HP LP bypass require these valves to control steam flow during bypass operation.
3. The efficiency of the Reheat cycle can be improved by increasing the pressure and temperature of steam entering into the turbine. As the initial pressure increases the expansion ratio of the turbine also increases and the steam becomes quite wet at the end of expansion.
The main advantage of reheat cycle is to reduce the specific consumption and consequently reduce the size of the boiler and other auxilaries for the same power.The reheat cycle is preffered for the high capacity above 100 MW plant.
1.Firm structural support
1. Flow blockage by condensed steam 2. Needs slow restart to purge the water that accumulates in the bottom.
supported from above
1.Proper drainage of the condensed steam
1. Lack the structural rigidity, especially in high speed gas flow
Supported from below
1. Proper drainage
2. Good structural rigidity.
1. They do not view the flam directly so they are mainly from the convective type
Usually supported in the vertical gas ducts parallel to the main furnace.