Method for operating a combustion system and combustion system

Abstract

A combustion system with a burner and a membrane unit including a retentate side and permeate side for separating oxygen from air is provided. The permeate side of the membrane unit is connected to the burner via a line. A heat exchanger is connected in a combustion gas flow such that a hot combustion gas arising from fossil combustion is applied to the primary side of the heat exchanger and air applied to the secondary side of the heat exchanger is heated to a temperature required for operating the membrane unit and fed to the membrane unit. Further, a method for operating the combustion system is provided.

1 .- 26 . (canceled) 
   
   
       27 . A method of operating a combustion system with a burner operated with a fossil fuel, comprising:
 separating oxygen out of air by a membrane at a process temperature;   feeding the separated-out oxygen to the burner for combustion with the fossil fuel, a hot combustion gas being formed;   feeding heat energy to the membrane to maintain the required process temperature, the heat energy being obtained from hot combustion gas in a heat exchange with the air;   feeding heated air to the membrane; and   carrying away the separated-out oxygen away from the membrane via a line.   
   
   
       28 . The method as claimed in  27 , wherein the air is heated in heat exchange with the combustion gas to 700° C. to 1000° C. 
   
   
       29 . The method as claimed in  claim 27 , further comprising:
 cooling down the separated-out oxygen.   
   
   
       30 . The method as claimed in  29 , wherein the separated-out oxygen is cooled in a heat exchange with air, the air being warmed. 
   
   
       31 . The method as claimed in  claim 30 , wherein the warmed air is mixed with the air heated through the heat exchange with the combustion gas, and the mixed heated air is fed to the membrane. 
   
   
       32 . The method as claimed in  claim 27 , further comprising:
 mixing a part of the combustion gas with the oxygen after the heat exchange with the air.   
   
   
       33 . The method as claimed in  32 , wherein the combustion gas-oxygen mixture is fed to the burner for combustion with the fossil fuel. 
   
   
       34 . The method as claimed in  claim 27 , further comprising:
 feeding the air which is at least partially depleted through the removal of oxygen by the membrane to an expander.   
   
   
       35 . The method as claimed in  claim 34 , wherein the expander drives a compressor, the compressor applying compressed air to the membrane on a permeate side. 
   
   
       36 . The method as claimed in  claim 27 , wherein 80 to 100% of the air is fed to a heat exchange with the hot combustion gas, and wherein 0 to 20% of the air is fed to a heat exchange with the oxygen separated out of the air. 
   
   
       37 . A combustion system, comprising:
 a burner;   a line;   a membrane unit including a membrane, a retentate side and a permeate side, for capturing oxygen from air, the membrane unit being connected at the permeate side to the burner via the line; and   a heat exchanger positioned in a stream of combustion gas, wherein
 a hot combustion gas produced from fossil firing is applied to the heat exchanger on a primary side, 
 the air supplied to the heat exchanger is heated to a temperature required for operating the membrane unit on a secondary side and is fed to the membrane unit, and 
 the oxygen separated out in the membrane unit is carried away from the membrane via the line. 
   
   
   
       38 . The combustion system as claimed in  claim 37 , further comprising:
 an oxygen/air heat exchanger arranged in the line between the permeate side and the burner, the oxygen/air heat exchanger being positioned on the secondary side of the retentate side.   
   
   
       39 . The combustion system as claimed in  claim 37 , wherein the air heated to a process temperature in the heat exchanger is mixed with air warmed in the oxygen/air-heat exchanger on the secondary side and is fed to the retentate side. 
   
   
       40 . The combustion system as claimed in  claim 37 , further comprising:
 a fan connected in the line between the permeate side and the burner.   
   
   
       41 . The combustion system as claimed in  claim 37 , further comprising:
 a recirculation line for the combustion gas, the recirculation line being connected to the line via which the permeate side is connected to the burner.   
   
   
       42 . The combustion system as claimed in  claim 37 , further comprising:
 an expander; and   a compressor,   wherein the retentate side is connected with the expander for use of thermal and mechanical energy of a retentate, and   wherein the expander is coupled to the compressor.   
   
   
       43 . The combustion system as claimed in  claim 42 , wherein the compressor is an air compressor to which the air to be separated by the membrane is fed, the air compressor being connected with the retentate side via a further line. 
   
   
       44 . The combustion system as claimed in  37 , wherein the membrane is an oxygen ion-conductive membrane. 
   
   
       45 . The combustion system as claimed in  claim 37 , further comprising:
 a fossil-fired steam generator fired by the burner.   
   
   
       46 . A steam power plant, comprising:
 a steam turbine;   a CO2 separator for separating CO2 out of a combustion gas; and   a combustion system, the combustion system comprising:
 a burner; 
 a line; 
 a membrane unit including a membrane, a retentate side and a permeate side, for capturing oxygen from air, the membrane unit being connected at the permeate side to the burner via the line; and 
 a heat exchanger positioned in a stream of combustion gas, wherein
 a hot combustion gas produced from fossil firing is applied to the heat exchanger on a primary side, 
 the air supplied to the heat exchanger is heated to a temperature required for operating the membrane unit on a secondary side and is fed to the membrane unit, and 
 the oxygen separated out in the membrane unit is carried away from the membrane via the line.