Customized design super heater and reheater for power plant boiler boiler outlet
Reheater Spray System
1. Reheater spray is normally provided at the inlet of reheater in the cold reheat pipe. This is used in boilers only if the first control system provided could not reduce the temperature to the required level.
2. Hence this is also called as emergency injection by many boiler designers. Using the emergency spray in reheater reduces the heat rate as the injection water is tapped before the high pressure heaters in the power generation cycle.
3. Other effects of over spraying in reheater are the same as superheater except that of metal temperature. In reheater the overall steam flow increases with injection in all the sections and so the metal temperature gets controlled.
1. The superheated steam then flows through the main steam piping to the high-pressure turbine. Exhaust steam from the high-pressure turbine is guided to the boiler for reheating and from there to the intermediate and low-pressure turbines.
2. High reheating temperatures improve the output and efficiency of a power plant.
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.