Method and apparatus of controlling combustion in oxyfuel combustion boiler

Abstract

A method and an apparatus of controlling combustion in an oxyfuel combustion boiler are provided which ensure a sufficient furnace heat absorption through prevention of lowering of flame temperature, enabling oxyfuel combustion operations to be performed in a stable manner. A boiler-brought-in oxygen density which is an oxygen density for a total amount of gases introduced into a coal burning boiler is calculated and a flow rate of total recirculating gases is controlled such that the boiler-brought-in oxygen density falls within a predetermined range.

1 . A method of controlling combustion in an oxyfuel combustion boiler where while oxygen fed from an air separation unit is introduced into a coal burning boiler, an exhaust gas in recirculation is introduced as primary and secondary recirculating exhaust gases into a mill and the coal burning boiler, respectively, the pulverized coal pulverized by the mill being transferred by said primary recirculating exhaust gas to a burner for oxyfuel combustion with said oxygen and said secondary recirculating exhaust gas, the method comprising
 measuring a boiler-brought-in oxygen density which is an oxygen density for a total amount of gases introduced into the coal burning boiler and   controlling a flow rate of total recirculating exhaust gases such that the boiler-brought-in oxygen density falls within a predetermined range.   
     
     
         2 . A method of controlling combustion in an oxyfuel combustion boiler as claimed in  claim 1 , wherein the boiler-brought-in oxygen density falls within a range from 25 to 30%. 
     
     
         3 . An apparatus of controlling combustion in an oxyfuel combustion boiler where while oxygen fed from an air separation unit is introduced into a coal burning boiler, an exhaust gas in recirculation is introduced as primary and secondary recirculating exhaust gases into a mill and the coal burning boiler, respectively, the pulverized coal pulverized by the mill being transferred by said primary recirculating exhaust gas to a burner for oxyfuel combustion with said oxygen and said secondary recirculating exhaust gas, the apparatus comprising
 an O 2  density monitor for sensing an O 2  density of oxygen to be introduced into the coal burning boiler,   a flowmeter for sensing a flow rate of oxygen to be introduced into the coal burning boiler,   an O 2  density monitor for sensing an O 2  density of the primary recirculating exhaust gas to be introduced into the mill,   a flowmeter for sensing a flow rate of the primary recirculating exhaust gas to be introduced into the mill,   an O 2  density monitor for sensing an O 2  density of the secondary recirculating exhaust gas to be introduced into the coal burning boiler,   a flowmeter for sensing a flow rate of the secondary recirculating exhaust gas to be introduced into the coal burning boiler,   a flow rate regulator for regulating a flow rate of total recirculating exhaust gases to be introduced into the mill and the coal burning boiler and   a controller for calculating a boiler-brought-in oxygen density which is an oxygen density for a total amount of gases introduced into the coal burning boiler on the basis of the O 2  densities sensed by the respective O 2  density monitors and the flow rates sensed by the respective flowmeters, the controller outputting a flow rate control signal to the flow rate regulator such that the boiler-brought-in oxygen density falls within a predetermined range.   
     
     
         4 . An apparatus of controlling combustion in an oxyfuel combustion boiler where while oxygen fed from an air separation unit is introduced into a coal burning boiler, an exhaust gas in recirculation is introduced as primary and secondary recirculating exhaust gases into a mill and the coal burning boiler, respectively, the pulverized coal pulverized by the mill being transferred by said primary recirculating exhaust gas to a burner for oxyfuel combustion with said oxygen and said secondary recirculating exhaust gas, the apparatus comprising
 an O 2  density monitor for sensing an O 2  density of oxygen to be introduced into the coal burning boiler,   a flowmeter for sensing a flow rate of oxygen to be introduced into the coal burning boiler,   an O 2  density monitor for sensing an O 2  density of total recirculating exhaust gases to be introduced into the mill and the coal burning boiler,   a flowmeter for sensing a flow rate of total recirculating exhaust gases to be introduced into the mill and the coal burning boiler,   a flow rate regulator for regulating a flow rate of the total recirculating exhaust gases to be introduced into the mill and the coal burning boiler and a controller for calculating a boiler-brought-in oxygen density which is an oxygen density for a total amount of gases introduced into the coal burning boiler on the basis of the O 2  densities sensed by the respective O 2  density monitors and the flow rates sensed by the respective flowmeters, the controller outputting a flow rate control signal to the flow rate regulator such that the boiler-brought-in oxygen density falls within a predetermined range.   
     
     
         5 . An apparatus of controlling combustion in an oxyfuel combustion boiler as claimed in  claim 3  or  4 , wherein the boiler-brought-in oxygen density falls within a range from 25 to 30%.