Oxyfuel Boiler System and Method of Controlling the Same

Abstract

The oxyfuel boiler system comprises: an oxygen generator; a coal mill; a burner to burn pulverized coal; an after-gas port to which oxygen generated at the oxygen generator is supplied; a boiler provided with the burner and the after-gas port on its wall; a flue introducing combustion exhaust gas from the boiler to the outside; a recirculation gas supply pipe having an exhaust gas tapping port in the midway of the flue and supplying recirculation exhaust gas to the coal mill, the burner, and the after gas port; and an oxygen supply pipe supplying oxygen from the oxygen generator to the burner and the after-gas port, wherein the exhaust gas tapping port is disposed downstream of a dry dust-removing apparatus arranged in the flue, and there is provided an oxygen controlling apparatus for making a concentration of oxygen to be supplied to the after-gas port lower than that of oxygen to be supplied to the burner.

1 . An oxyfuel boiler system comprising:
 an oxygen generator to separate oxygen from air;   a coal mill to dry and pulverize coal;   a burner to burn the dried and pulverized coal with oxygen generated at the oxygen generator;   an after-gas port to which oxygen generated at the oxygen generator is supplied;   a boiler provided with the burner and the after-gas port on its wall;   a flue introducing combustion exhaust gas from the boiler to the outside;   a recirculation gas supply pipe having an exhaust gas tapping port disposed in the midway of the flue and supplying recirculation exhaust gas to the coal mill, the burner, and the after-gas port; and   an oxygen supply pipe supplying oxygen from the oxygen generator to the burner and the after-gas port,   wherein the exhaust gas tapping port is disposed downstream of a dry dust-removing apparatus arranged in the flue, and   there is provided an oxygen controlling apparatus for making a concentration of oxygen to be supplied to the after-gas port lower than that of oxygen to be supplied to the burner.   
   
   
       2 . An oxyfuel boiler system according to  claim 1 ,
 wherein the exhaust gas tapping port is disposed downstream of the dry dust-removing apparatus and downstream of a moisture removing cooler.   
   
   
       3 . The oxyfuel boiler system according to  claim 1 ,
 wherein the exhaust gas tapping port is disposed downstream of the dry dust-removing apparatus and upstream of a first moisture removing cooler, and   a second moisture removing cooler is provided in the midway of the recirculation gas supply pipe.   
   
   
       4 . An oxyfuel boiler system comprising:
 an oxygen generator to separate oxygen from air;   a coal mill to dry and pulverize coal;   a burner to burn the dried and pulverized coal with oxygen generated at the oxygen generator;   an after-gas port to which oxygen generated at the oxygen generator is supplied;   a boiler provided with the burner and the after-gas port on its wall;   a flue introducing combustion exhaust gas from the boiler to the outside;   recirculation gas supply pipes having two exhaust gas tapping ports disposed in the midway of the flue and supplying recirculation exhaust gas taken in from the respective exhaust gas tapping ports to the boiler; and   an oxygen supply pipe supplying oxygen from the oxygen generator to the burner and the after-gas port,   wherein the oxyfuel boiler system has:   the first exhaust gas tapping port arranged in the flue and disposed downstream of a dry dust-removing apparatus and the second exhaust gas tapping port arranged in the flue and disposed downstream of a moisture removing cooler;   the recirculation gas supply pipe including a first line supplying exhaust gas taken in from the first exhaust gas tapping port to the after-gas port and a second line supplying exhaust gas taken in from the second exhaust gas tapping port to the burner; and   an oxygen controlling apparatus for oxidizer making a concentration of oxygen to be supplied to the after-gas port lower than that of oxygen supplied to the burner.   
   
   
       5 . A method of controlling an oxyfuel boiler system, comprising:
 an oxygen generator to separate oxygen from air;   a coal mill to dry and pulverize coal;   a burner to burn the dried and pulverized coal with oxygen generated at the oxygen generator;   an after-gas port to which oxygen generated at the oxygen generator is supplied;   a boiler provided with the burner and the after-gas port on its wall;   a flue introducing combustion exhaust gas from the boiler to the outside;   a recirculation gas supply pipe having an exhaust gas tapping port disposed in the midway of the flue and supplying recirculation exhaust gas to the coal mill, the burner and the after-gas port; and   an oxygen supply pipe supplying oxygen from the oxygen generator to pipes supplying exhaust gas to the coal mill, the burner and the after-gas port by the recirculation gas supply pipe,   the method comprising the steps of:   taking exhaust gas in from downstream of a dry dust-removing apparatus arranged in the flue; and   making a concentration of oxygen to be supplied to the after-gas port lower than that of oxygen to be supplied to the burner.