Industry High Temperature Reheater In Boiler Alloy Steel 12Cr1MoV GB Standard
High Temperature reheater Introduction
1. Superheaters and reheaters are specially designed to increase the temperature of the saturated steam and to help control the steam outlet temperature.
2. They are simple single-phase heat exchangerswith steam flowing inside and the flue gas passing outside, generally in the cross flow. Superheaters and reheaters are often divided into multiple sections to help control steam temperature and optimize heat recovery, and their heating surfaces can be arranged either horizontally or vertically.
3. The physical design and location of the surfaces is dependent on the desired outlet temperature, heat absorption, fuel ash characteristics and cleaning equipment.
4. The main components are usually manufactured from steel alloys, as both the superheater and reheaters are operated at high temperature. As shown in Table 5.3, the net electrical efficiency is heavily dependent on the outlet temperature of both the superheater and reheater.
Processing
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.
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.
Differences
| Type | Advantages | Disadvantages | Supporting method |
| Pendant-type | 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 |
| Inverted-type | 1.Proper drainage of the condensed steam | 1. Lack the structural rigidity, especially in high speed gas flow | Supported from below |
| Horizontal -type | 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. |
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