ONCE-THROUGH BOILER DEVICE AND METHOD OF CONTROLLING COMBUSTION OF ONCE-THROUGH BOILER

PROBLEM TO BE SOLVED: To provide an once-through boiler device that performs stage control of combustion and can perform combustion control smoothly corresponding to a load and a method of controlling combustion of an once-through boiler.SOLUTION: The once-through boiler device includes a pressure detector 33 for detecting vapor pressure and a controller 19 that controls flow amount adjustment means 32 based on vapor pressure detection results from the pressure detector to perform control a fuel supply amount to a burner nozzle 6 such that the combustion load rate of the burner nozzle corresponds to the vapor pressure detection results. The controller can perform combustion control through a stage combustion control mode wherein combustion is controlled by switching a plurality of set combustion load factors and a proportional combustion control mode wherein proportional combustion control is performed corresponding to the combustion load factor within a set combustion load factor. When the vapor pressure to be detected is high load or low load, the stage combustion control is performed. For a middle load, the proportional combustion control is executed.