Patent ID: 8661993

Claim:
A heavy fuel-fired boiler system comprising: a denitration device that removes nitrogen oxide in exhaust gas from a heavy fuel-fired boiler using a heavy fuel; an air preheater that recovers heat in the gas after the nitrogen oxide is removed; an electric precipitator that removes dust while adding ammonia into the gas after heat recovery; a vapor-liquid contact type desulfurization device that removes sulfur oxide in the gas after dust removal; a stack that exhausts the gas after desulfurization to outside; an ash flowability measuring instrument that measures ash flowability on a downstream side of the electric precipitator, the ash flowability indicating a physical property of the gas after dust removal; an air supply unit for supplying air to the heavy fuel-fired boiler; and a controller for adjusting an air feed rate to the boiler based on information of the measured ash flowability so that the ash flowability is within a predetermined threshold and unburned C concentration/S concentration ratio is constant.