Emissionless Oxyfuel Combustion Process and a Combustion System Using Such a Process

Abstract

A method of combusting carbonaceous fuel in a combustion system. The combustion system includes a source of oxygen and a furnace. The method includes the steps of (a) feeding fuel and combustion gas including oxygen and recycling gas into the furnace for combusting the fuel with the oxygen and producing exhaust gas that includes CO 2 , water and excess oxygen as its main components, (b) conducting the exhaust gas discharged from the furnace into a scrubber so as to remove pollutants from the exhaust gas, (c) dividing the exhaust gas into a first exhaust gas stream and a second exhaust gas stream, and conducting the second exhaust gas stream as a recycling gas stream into the furnace, (d) conducting the first exhaust gas stream into a CO 2 purification and capturing unit (CPU) to produce one or more condensate streams, a purified liquid CO 2 stream and a vent gas stream that includes remaining CO 2 , (e) discharging the purified liquid CO 2 stream from the combustion system, (f) conducting the vent gas stream into an adsorption unit so as to adsorb compounds, including remaining CO 2 , from the vent gas stream to an adsorbing material and to produce a pass-through gas stream, and (g) regenerating the adsorbing material to produce a desorbed gas stream that includes at least a portion of the adsorbed compounds, and conducting at least a portion of the desorbed gas stream into the furnace.

1 . A method of combusting carbonaceous fuel in a combustion system, which combustion system includes a source of oxygen and a furnace, the method comprising the steps of:
 (a) feeding fuel and combustion gas comprising oxygen and recycling gas into the furnace for combusting the fuel with the oxygen and producing exhaust gas comprising CO 2 , water and excess oxygen as its main components;   (b) conducting the exhaust gas discharged from the furnace into a scrubber so as to remove pollutants from the exhaust gas;   (c) dividing the exhaust gas into a first exhaust gas stream and a second exhaust gas stream and conducting the second exhaust gas stream as a recycling gas stream into the furnace;   (d) conducting the first exhaust gas stream into a CO 2  purification and capturing unit (CPU) to produce one or more condensate streams, a purified liquid CO 2  stream and a vent gas stream comprising remaining CO 2 ;   (e) discharging the purified liquid CO 2  stream from the combustion system;   (f) conducting the vent gas stream into an adsorption unit so as to adsorb compounds, including remaining CO 2 , from the vent gas stream to an adsorbing material and to produce a pass through gas stream; and   (g) regenerating the adsorbing material to produce a desorbed gas stream, comprising at least a portion of the adsorbed compounds, and conducting at least a portion of the desorbed gas stream into the furnace.   
     
     
         2 . The method according to  claim 1 , wherein the vent gas stream discharged from the CO 2  purification and capturing unit is at a pressure from about 20 bar to about 40 bar and at a temperature from about −50° C. to about 20° C. 
     
     
         3 . The method according to  claim 1 , wherein the adsorption unit is a pressure swing adsorption unit. 
     
     
         4 . The method according to  claim 1 , further comprising a step of conducting at least a portion the one or more condensate streams into the scrubber. 
     
     
         5 . The method according to  claim 1 , wherein the source of oxygen is an air separation unit and at least a portion of the pass through gas stream is conducted as a feed gas to the air separation unit. 
     
     
         6 . The method according to  claim 1 , wherein the adsorption unit adsorbs more efficiently O 2  than N 2 , and at least a portion of the pass through gas stream is conducted to the atmosphere. 
     
     
         7 . The method according to  claim 1 , wherein at least a portion of one or more of the pass through gas stream and the desorbed gas stream is conducted as a coolant to one or more of the CPU and the source of oxygen. 
     
     
         8 . The method according to  claim 1 , further comprising the step of mixing the desorbed gas stream with the recycling gas stream prior to their introduction into the furnace. 
     
     
         9 . The method according to  claim 1 , further comprising the step of mixing a stream of oxygen from the source of oxygen with one or more of the desorbed gas stream and the recycling gas stream prior to their introduction into the furnace. 
     
     
         10 . A combustion system for combusting carbonaceous fuel, the combusting system comprising:
 a source of oxygen;   a furnace;   means for feeding fuel and a combustion gas comprising oxygen and recycling gas into the furnace for combusting the fuel with the oxygen and producing exhaust gas comprising CO 2 , water and excess oxygen as its main components;   an exhaust gas channel connected to the furnace for discharging the exhaust gas from the furnace;   a scrubber arranged in the exhaust gas channel for removing pollutants from the exhaust gas;   means for dividing the exhaust gas into a first exhaust gas stream and a second exhaust gas stream;   a recycling channel for conducting the second exhaust gas stream as a recycling gas stream into the furnace;   an end portion of the exhaust gas channel for conducting the first exhaust gas stream into a CO 2  purification and capturing unit (CPU) to produce one or more a condensate streams, a purified liquid CO 2  stream and a vent gas stream comprising remaining CO 2 ;   means for discharging the purified liquid CO 2  stream from the combustion system;   an adsorption unit arranged to adsorb compounds, including remaining CO 2 , from the vent gas stream to an adsorbing material and to produce a pass through gas stream;   means for regenerating the adsorbing material to produce a desorbed gas stream, comprising at least a portion of the adsorbed compounds; and   a desorbed gas channel for conducting at least a portion of the desorbed gas stream into the furnace.   
     
     
         11 . The combustion system according to  claim 10 , wherein the adsorption unit is a pressure swing adsorption unit. 
     
     
         12 . The combustion system according to  claim 10 , further comprising means for conducting at least a portion of the one or more condensate streams into the scrubber. 
     
     
         13 . The combustion system according to  claim 10 , wherein the source of oxygen is an air separation unit and the combustion system comprises means for conducting at least a portion of the pass through gas stream as a feed gas to the air separation unit. 
     
     
         14 . The combustion system according to  claim 10 , wherein the adsorption unit comprises adsorption material suitable for adsorbing O 2  more efficiently than N 2 , and at least a portion of the pass through gas stream is conducted to the atmosphere. 
     
     
         15 . The combustion system according to  claim 10 , further comprising means for conducting at least a portion of one or more of the pass through gas stream and the desorbed gas stream as a coolant to one or more of the CPU and the source of oxygen. 
     
     
         16 . The combustion system according to  claim 10 , further comprising means for mixing the desorbed gas stream with the recycling gas stream prior to their introduction into the furnace. 
     
     
         17 . The combustion system according to  claim 10 , further comprising means for mixing a stream of oxygen from the source of oxygen with one or more of the desorbed gas stream and the recycling gas stream prior to their introduction into the furnace.