Powder fuel combustion apparatus and combustion method

A combustion method of combusting a powder fuel by a powder fuel combustion apparatus, comprising:

• a fuel charging step, an igniting step, a gasification combustion step, a direct combustion step, and an ember-ashing step,
• wherein the powder fuel combustion apparatus comprises
• a primary combustion chamber configured to combust the powder fuel in an interior thereof, and a secondary combustion chamber configured to combust a gas discharged from the primary combustion chamber,
• wherein the primary combustion chamber comprises a fuel supply device configured to supply the powder fuel to an interior thereof, a primary air supply port configured to supply air to an interior thereof, and an ignition burner configured to ignite the powder fuel in an interior thereof,
• wherein a bottom portion of the primary combustion chamber comprises an inclined portion inclined to narrow toward a lower direction, a bottom portion air supply port configured to supply air to an interior thereof, an ash outlet provided to a lower position of the inclined portion, and a bottom portion air injection nozzle having a tubular shape and arranged in a vertical direction, the bottom portion air injection nozzle comprising openings formed on an upper end and a lower end thereof, the lower end positioned toward the ash outlet, and having air supplied to an interior thereof,
• wherein the secondary combustion chamber comprises a secondary burner configured to heat an interior thereof, and a secondary air supply port configured to supply combustion air to an interior thereof,
• a primary air supply device configured to supply air to the primary air supply port and the bottom portion air supply port, an injection air supply device configured to supply air to the bottom portion air injection nozzle, and a secondary air supply device configured to supply air to the secondary air supply port, and
• a controller configured to control operation of the fuel supply device, the ignition burner, the secondary burner, the primary air supply device, the injection air supply device, and the secondary air supply device,
• wherein the controller is configured to
• accumulate a predetermined amount of the powder fuel to the primary combustion chamber by the fuel supply device in the fuel charging step,
• heat the interior of the secondary combustion chamber by the secondary burner, and after the interior of the secondary combustion chamber has reached a predetermined temperature, ignite the powder fuel being accumulated using the ignition burner in the igniting step,
• supply an amount of air that is smaller than an amount of air necessary for complete combustion of the powder fuel being accumulated through the primary air supply port, the bottom portion air supply port, and the bottom portion air injection nozzle to generate flammable gas in the primary combustion chamber, introduce the flammable gas to the secondary combustion chamber, and perform complete combustion of the flammable gas by supplying air for secondary combustion through the secondary air supply port in the gasification combustion step,
• activate the primary air supply device and the injection air supply device to supply an amount of air necessary for direct combustion of the powder fuel into the primary combustion chamber through the primary air supply port, the bottom portion air supply port, and the bottom portion air injection nozzle, activate the fuel supply device to supply the powder fuel into the primary combustion chamber and perform combustion of the powder fuel to activate the fuel supply device as a burner, introduce combustion gas discharged from the primary combustion chamber to the secondary combustion chamber, and perform complete combustion of the combustion gas by supplying air for secondary combustion through the secondary air supply port in the direct combustion step, and
• stop supply of fuel by the fuel supply device and perform ember combustion and ashing of the powder fuel remaining in the primary combustion chamber in the ember-ashing step.