COMBUSTION CONDITION DECISION DEVICE, COMBUSTION CONDITION DECISION METHOD, AND COMBUSTION SYSTEM OF COMBUSTION FURNACE

A combustion furnace combustion condition determination device for determining a combustion condition that includes a plurality of combustion control parameters for controlling a combustion device in a combustion furnace, said combustion condition determination device comprising: a pre-combustion fuel component acquisition unit for acquiring a pre-combustion fuel component, which includes a measured value of at least a portion of the fuel components of pre-combustion fuel, which is a fuel supplied to a burner that supplies fuel and air to the interior of the combustion furnace; and a command value determination unit that, on the basis of the pre-combustion fuel component, determines a command value for at least one of the combustion control parameters such that an evaluation subject index, which is the unburnt component in ash generated by combustion of the pre-combustion fuel and/or the NOx concentration of the exhaust gas, satisfies a prescribed criterion.