System General Description
Feed water is heated in the economizer then enters the steam drum. Here, it mixes with the boiler water before flowing into four centralized downcomers (Φ508×55，SA-106C). Each downcomer has distributing headers which connect to 74 pipes (Φ159×18，20G). These pipes take the water to the lower headers at the front, back and both sides of the water wall.The water is heated in the water wall tubes, becoming a steam-water mixture before entering the water wall upper headers.
Upper headers connect to 94 steam-water pipes (Φ159×18，20G), through which the steam water mixture enters the steam drum to be separated by the separator (classifier) in the drum. Saturated steam goes to the penthouse superheater. Saturated water mixes with feed water from the economizer in the drum and enters the downcomers to be recirculated.
Based on steam flow process, the superheating system can be divided into six stages, which are respectively the penthouse superheater (roof, or ceiling, superheater), enclosed wall superheater, primary (low temperature) superheater, large platen superheater, rear platen superheater, and secondary (high temperature) superheater.
The steam reheat system can be divided into three stages respectively based on steam flow process: wall type reheater, intermediate reheater, secondary reheater…
Being heated, saturated steam with a certain temperature and pressure is generated from the demineralized water, which becomes superheated steam or reheated steam with a certain temperature and pressure through high temperature and low temperature superheater. In this way, the exhausted flue gas temperature is decreased, the thermal efficiency is improved and the thermal deviation of steam & water system is reduced.