1. The boiler is furnished with reheaters, where the steam is reheated to improve cycle efficiency after high pressure part of the steam turbine. Reheater system increase boiler LP – steam, which is turbine’s IP-steam (IP = IntermediatePressure), temperature after turbine HPcasing.
2. After reheater steam is lead to turbine IP-casing. Steam from the pressure reduction valve after superheater IV is taken to the inlet of the reheater I. The valves are arranged so that the pressure reduction station (S1 LBH10/20 AA201) controls boiler HP –steam pressure, but functioning also as a safety valves of the HP –steam system (in the cold reheater line).
Hot Reheat System
1. Hot reheat steam system has two safety valves, which functions also as pressure controlling device’s. Hot reheat system valves blow first and therefore in some operation situations HP –pressure station valves can be maintain closed.
2. These valves are used for regulating the boiler pressure especially during start ups (or shut down). The start-up steam line is led to atmosphere trough a silencer. The reheat steam enters to reheater IA, which is of similar construction to superheater I and located in the back pass of the boiler after SH II. Reheater IB is after SH I.
3. Reheat steam temperature is maintained at design value typically over load range 60 –100 % of MCR. Compared with feed water spray control by-pass control gives higher plant efficiency. Final reheating takes place in reheater II, which is similar in construction to Intrex superheaters and is located in the return leg. All superheaters and reheaters are fully drainable.
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.