The reheater is essentially a Steam Superheater that reheats the low-pressure steam that has done work and reaches a certain temperature. The function of the reheater further improves the thermal efficiency of the power plant cycle and enables the steam temperature of the last stage of the turbine to be controlled. within the allowable range. The reheater is the heater in the boiler that heats the steam from the steam turbine into superheated steam. There are two functions of the reheater: one is to reduce the humidity of water vapor, which is beneficial to protect the turbine blades; the other is to improve the relative internal efficiency and absolute internal efficiency of the steam turbine.
The layout of the reheater follows the layout of the superheater, and there are three types: convection, radiation and semi-radiant. Convective reheater has countercurrent, cocurrent, mixed flow, single tube ring, double tube ring, multi-tube ring, in-line, staggered, vertical, horizontal, parallel to the front wall, perpendicular to the front wall. Convective reheaters are reheaters that primarily absorb convective heat. Radiant reheater refers to a reheater that absorbs radiation from the furnace. Semi-radiant reheater (that is, screen superheater) refers to a reheater that absorbs more radiation in the furnace (radiation heat absorption exceeds 1/2 of the total heat). The material selection principle of the reheater is the same as that of the superheater. Since the cooling capacity of the reheated steam is lower than that of the superheated steam, the design wall temperature of the superheater is generally higher than that of the same temperature grade. The metal pipes of the high temperature reheater are generally made of alloy steel (metal with a total alloying element exceeding 5%) pipes. For example, 12CrlMoV, steel 102, SA213-T91, SA213-TP304, SA213-TP347, etc.
