Biomass-mixed-firing pulverized coal fired boiler and operation method of the boiler

A method of operating a biomass-mixed-firing pulverized coal fired boiler, comprising the steps of:

• milling a biomass fuel by using a biomass mill;
• supplying a milled biomass fuel to a furnace by using a biomass burner;
• supplying a pulverized coal to the furnace by using a pulverized coal burner;
• burning an unburned component of the biomass fuel contained in ashes discharged at a furnace bottom on a conveyor belt of a dry clinker processing unit, which is provided below the furnace, by supplying a combustion air toward the ashes on the clinker conveyor through combustion air nozzles provided at a bottom end of a transition hopper located between the furnace and the clinker conveyor;
• supplying cooling air to the dry clinker processing unit through cooling air provided on one side face of a casing of the dry clinker processing unit and distinct from the combustion air nozzles,
• wherein an efficiency of combustion in an entire boiler is optimized by controlling both of a flow rate of a combustion air supplied toward an interior of the furnace and a flow rate of the combustion air supplied toward the ashes discharged at the furnace bottom on the clinker conveyor, so that the amount of combustion air supplied over the entire boiler is optimized,
• wherein the combustion air nozzles are located at the transition hopper and are configured to impact air onto the ashes on the clinker conveyor thereby increasing burning of the unburned component of the biomass fuel contained in the ashes.

A biomass-mixed-firing pulverized coal fired boiler, comprising:

• a furnace configured to burn a biomass fuel together with a pulverized coal in a mixed state;
• a pulverized coal burner configured to supply the pulverized coal into the furnace;
• a biomass burner configured to supply the biomass fuel into the furnace;
• a biomass mill configured to mill the biomass fuel to be supplied to the biomass burner;
• a dry clinker processing unit provided below the furnace, the dry clinker processing unit including a clinker conveyor configured to carry ashes discharged from the furnace at a furnace bottom;
• a combustion-air supply unit configured to supply a combustion air toward the ashes on the clinker conveyor through combustion air nozzles arranged such that the combustion air is ejected toward the rear face of the conveyor belt as to burn an unburned component of the biomass fuel contained in the ashes discharged at the furnace bottom on the clinker conveyor;
• a cooling-air supply unit configured to supply a cooling air to the dry clinker processing unit through cooling air intakes, distinct from the combustion air nozzles;
• and
• a combustion-air controller configured to optimize an efficiency of combustion in an entire boiler by controlling both of a flow rate of a combustion air supplied toward an interior of the furnace and a flow rate of the combustion air supplied from the combustion-air supply unit toward the ashes discharged at the furnace bottom on the clinker conveyor, so that the amount of combustion air supplied over the entire boiler is optimized,
• wherein the combustion air nozzles are located at the transition hopper and are configured to impact air onto the ashes on the clinker conveyor thereby increasing burning of the unburned component of the biomass fuel contained in the ashes.