JPS6488005A - Method of operating once-through boiler - Google Patents

Abstract

PURPOSE: To achieve a stable start by setting the value of a load higher when shifting from a circulation operation to a through flow operation on starting as compared with a normal operation and controlling the amount of recirculation to the fire oven of a combustion gas by the temperature of a water wall part or a cage part. CONSTITUTION: When a control circuit operates, the program setting value of the amount of recirculation gas is given corresponding to the change in the amount of total fuel and the amount of supplied water flow. While the shift of the amount of water supply from the circulation operation to the through flow operation on normal operation is made with a load of X, the shift from the circulation operation to the through flow operation is made by a load of X+α. The amount of recirculation gas of a combustion exhaust gas to a fire oven increases the amount of recirculation gas between a load X and a load X+α along a stating program. However, in this case, depending on how much the temperature of the pipe wall of a water wall part or a boiler water deviates from a prescribed value, the amount of recirculation gas is controlled between upper-limit or lower-limit programs on activation by applying correction for increasing or decreasing, thus preventing the pipe wall temperature of a heat transfer pipe at the water wall part from being overheated.