Oxyfuel Boiler System and Method of Retrofit of Air Fired Boiler to Oxyfuel Boiler

Abstract

An oxyfuel boiler system, comprising: an oxygen generator to separate oxygen from air; a coal supply unit to dry and pulverize coal; a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer; a boiler provided with the burner; an exhaust gas discharge line to discharge exhaust gas generated in the boiler into environment; an exhaust gas treatment apparatus provided in the exhaust gas discharge line, a CO 2 separator provided downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2 from the exhaust gas; an exhaust gas recirculation line including an exhaust gas tapping port provided in the exhaust gas discharge line to extract a part of the exhaust gas; and an oxygen supply line to supply the oxygen generated at the oxygen generator to the exhaust gas flowing through the exhaust gas recirculation line, wherein the exhaust gas treatment apparatus is provided with at least an SO 3 removing unit and a moisture removing unit; and the exhaust gas tapping port of the exhaust gas recirculation line is disposed downstream of the exhaust gas treatment apparatus and upstream of the CO 2 separator for recirculating a part of the gas extracted from the port to the coal supply unit and/or the boiler.

1 . An oxyfuel boiler system, comprising:
 an oxygen generator to separate oxygen from air;   a coal supply unit to dry and pulverize coal;   a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer;   a boiler provided with the burner;   an exhaust gas discharge line to discharge exhaust gas generated in the boiler into environment;   an exhaust gas treatment apparatus provided in the exhaust gas discharge line,   a CO 2  separator provided downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2  from the exhaust gas;   an exhaust gas recirculation line including an exhaust gas tapping port provided in the exhaust gas discharge line to extract a part of the exhaust gas; and   an oxygen supply line to supply the oxygen generated at the oxygen generator to the exhaust gas flowing through the exhaust gas recirculation line,   wherein   the exhaust gas treatment apparatus is provided with at least an SO 3  removing unit and a moisture removing unit; and   the exhaust gas tapping port of the exhaust gas recirculation line is disposed downstream of the exhaust gas treatment apparatus and upstream of the CO 2  separator for recirculating a part of the gas extracted from the port to the coal supply unit and/or the boiler.   
   
   
       2 . The oxyfuel boiler system according to  claim 1 , wherein
 the exhaust gas extracted from the tapping port is supplied to the oxidizer feed path of the burner and an after-gas port provided in the boiler downstream of the burner.   
   
   
       3 . An oxyfuel boiler system, comprising:
 an oxygen generator to separate oxygen from air;   a coal supply unit to dry and pulverize coal;   a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer;   a boiler provided with the burner;   an exhaust gas discharge line to discharge an exhaust gas generated in the boiler into environment;   an exhaust gas treatment apparatus provided in the exhaust gas discharge line,   a CO 2  separator provided downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2  from the exhaust gas;   a couple of exhaust gas recirculation lines including an exhaust gas tapping port provided in the exhaust gas discharge line to extract a part of the exhaust, respectively; and   an oxygen supply line to supply the oxygen generated at the oxygen generator to the exhaust gas flowing through the exhaust gas recirculation line,   wherein   the exhaust gas treatment apparatus is provided with at least an NO x  removing unit, a heat exchanger, an SO 3  removing unit and a moisture removing unit; and   the exhaust gas tapping port of a first exhaust gas recirculation line is disposed downstream of the SO 3  emoving unit and the moisture removing unit and upstream of the CO 2  separator for recirculating the gas extracted from the port to the coal supply unit, and   the exhaust gas tapping port of s second exhaust gas recirculation line is disposed downstream of the NO x  removing unit and upstream of the heat exchanger for recirculating a part of the gas extracted from the port to the after-gas port disposed downstream of the burner.   
   
   
       4 . The oxyfuel boiler system according to  claim 3 , wherein
 the exhaust gas extracted from the tapping port of the second exhaust gas recirculation line is supplied to the oxidizer feed path of the burner and the after-gas port provided in the boiler downstream of the burner.   
   
   
       5 . A method for retrofitting a pulverized coal firing boiler including:
 a coal supply unit to dry and pulverize coal; a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer; a boiler provided with the burner; an exhaust gas discharge line to discharge exhaust gas generated in the boiler into environment; and an exhaust gas treatment apparatus provided in the exhaust gas discharge line,   the method comprising:   providing an oxygen generator to separate oxygen from air;   providing a CO 2  separator downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2  from the exhaust gas;   providing the exhaust gas treatment apparatus having an SO 3  removing unit and a moisture removing unit, and   providing an exhaust gas tapping port of an exhaust gas recirculation line disposed downstream of the SO 3  removing unit and the moisture removing unit and upstream of the CO 2  separator to mix a part of the exhaust gas extracted from the tapping port with the oxygen separated from the oxygen generator and supply mixture gas to the coal supply unit.   
   
   
       6 . A control apparatus of an oxyfuel boiler system, comprising:
 an oxygen generator to separate oxygen from air;   a coal supply unit to dry and pulverize coal;   a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer;   a boiler provided with the burner;   an exhaust gas discharge line to discharge exhaust gas generated in the boiler into environment;   an exhaust gas treatment apparatus provided in the exhaust gas discharge line,   a CO 2  separator provided downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2  from the exhaust gas;   an exhaust gas recirculation line including an exhaust gas tapping port provided in the exhaust gas discharge line to extract a part of the exhaust gas, and   an oxygen supply line to supply the oxygen generated at the oxygen generator to the exhaust gas flowing through the exhaust gas recirculation line,   wherein   the exhaust gas treatment apparatus is provided with at least an SO 3  removing unit and a moisture removing unit; and   the exhaust gas tapping port of the exhaust gas recirculation line is disposed downstream of the exhaust gas treatment apparatus and upstream of the CO 2  separator for recirculating a part of the gas extracted from the port to the coal supply unit,   the control apparatus comprising:   a device to control a rate of coal supplied to the coal supply unit, a flow rate of the recirculation exhaust gas and a rate of the oxygen supplied by the oxygen supply line in response to a demand signal indicating a load of the boiler.   
   
   
       7 . A method for controlling an oxyfuel boiler system including:
 an oxygen generator to separate oxygen from air;   a coal supply unit to dry and pulverize coal;   a burner having a fuel feed path for feeding pulverized coal supplied from the coal supply unit and an oxidizer feed path for feeding oxidizer;   a boiler provided with the burner;   an exhaust gas discharge line to discharge exhaust gas generated in the boiler into environment;   an exhaust gas treatment apparatus provided in the exhaust gas discharge line,   a CO 2  separator provided downstream of the exhaust gas treatment apparatus in the exhaust gas discharge line to separate CO 2  from the exhaust gas;   an exhaust gas recirculation line including an exhaust gas tapping port provided in the exhaust gas discharge line to extract a part of the exhaust gas, and   an oxygen supply line to supply the oxygen generated at the oxygen generator to the exhaust gas flowing through the exhaust gas recirculation line,   wherein   the exhaust gas treatment apparatus is provided with at least an SO 3  removing unit and a moisture removing unit; and   the exhaust gas tapping port of the exhaust gas recirculation line is disposed downstream of the exhaust gas treatment apparatus and upstream of the CO 2  separator for recirculating a part of the gas extracted from the port to the coal supply unit,   the method comprising:   controlling a rate of the coal supplied to the coal supply unit, a flow rate of the recirculation exhaust gas and a rate of the oxygen supplied by the oxygen supply line in response to a demand signal indicating a load of the boiler.