Shell Protection Reheater In Boiler ASME Standard Proper Drainage

Shell Protection erosion shield for the boiler tube and reheater tube ASME standard

Boiler tube and reheater Introduction

1. High pressure steam is expanded in turbine,moisture content of exhaust steam increases, which creates problem at exit end blades. So reheat type turbine is most commonly used for large capacity turbine using high pressure steam.

2. Steam after expanding at HP Turbine is sent to boiler for further heat addition or reheat.This steam is called as Cold reheat.Cold reheat is heated at reheater of the boiler.

3. The reheat steam called as Hot reheat is then sent to IP/ LP Turbine where it expands further. Single and double reheat turbines are commonly used for power generation.

Reheater Function

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.

Main Advantage

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.

Differences

Detailed Picture