Carbon dioxide capture from flue gas

Abstract

A method for capturing carbon dioxide from a flue gas includes (i) removing moisture from a flue gas to yield a dried flue gas; (ii) compressing the dried flue gas to yield a compressed gas stream; (iii) reducing the temperature of the compressed gas stream to a temperature T 1 using a first heat exchanger; (iv) reducing the temperature of the compressed gas stream to a second temperarature T 2 using a second heat exchanger stream, where T 2 <T 1 and at least a portion of the carbon dioxide from the compressed gas stream condenses, thereby yielding a solid or liquid condensed-phase carbon dioxide component and a light-gas component; (v) separating purities the condensed-phase component from the light-gas component to produce a condensed-phase stream and a light-gas stream; and (vi) using at least a portion of the condensed-phase stream and/or the light-gas stream in the second heat exchanger.

1 . A method for efficiently separating carbon dioxide from a flue gas of a hydrocarbon processing plant, comprising:
 (i) removing moisture from a flue gas of a hydrocarbon processing plant to yield an at least partially dried flue gas;   (ii) compressing the at least partially dried flue gas to yield a compressed-gas stream, wherein the compressed gas stream includes carbon dioxide;   (iii) reducing the temperature of the compressed-gas stream to a temperature T 1  using a first heat exchanger;   (iv) reducing the temperature of the compressed-gas stream to a second temperature T 2  using a second heat exchanger or using a second heat exchanger in combination with expansion of the compressed-gas stream, wherein T 2 <T 1  and wherein at least a portion of the carbon dioxide from the compressed gas stream condenses, thereby yielding a solid or liquid condensed-phase carbon dioxide component and a light-gas component;   (v) separating the condensed-phase component from the light gas component to produce a condensed-phase stream and a light-gas stream; and   (vi) using at least a portion of the light-gas stream in the second heat exchanger.   
     
     
         2 . A method as in  claim 1 , wherein reducing the temperature of the compressed gas stream in step (iv) includes expanding the compressed gas stream. 
     
     
         3 . A method as in  claim 2 , wherein the expansion of the compressed gas stream is carried out though a valve or a turbine. 
     
     
         4 . A method as in  claim 1 , wherein T 1  is in a range from about 0° C. to about 100° C. 
     
     
         5 . A method as in  claim 1 , wherein T 2  is in a range from about −175° C. to about −100° C.? 
     
     
         6 . A method as in  claim 1 , wherein the first heat exchanger is cooled using water and/or ambient air. 
     
     
         7 . A method as in  claim 1 , wherein the compressed gas stream includes an acid component, the method further comprising condensing at least a portion of the acid component in step (iv) to form a condensed-phase acid component or sulfur compound, wherein the condensed phase acid component or sulfur compound is removed from the compressed gas stream prior to the carbon dioxide condensing. 
     
     
         8 . A method as in  claim 1 , wherein the flue gas includes at least 10% carbon dioxide and at least 10% light gas. 
     
     
         9 . A method as in  claim 1 , wherein the flue gas is an exhaust from a coal fired combustion or gasification process. 
     
     
         10 . A method as in  claim 1 , wherein the compressed gas stream is at a pressure of at least 5 psi. 
     
     
         11 . A method as in  claim 10 , wherein the light-gas stream is compressed and stored in a vessel at a pressure of at least about 10 psi and subsequently expanded to generate power. 
     
     
         12 . A method as in  claim 1 , wherein the compressed gas stream is at a pressure of at least about 2 psi. 
     
     
         13 . A method as in  claim 12 , wherein the light-gas stream is stored in a vessel and subsequently expanded to generate power, wherein the power is generated and placed on a power grid having periods of high power demand and periods of low power demand, wherein the light-gas stream is stored during a period of low power demand and expanded to produce power during a period of high power demand. 
     
     
         14 . A method as in  claim 13 , wherein the light-gas stream is compressed using a compressor driven by an intermittent power source. 
     
     
         15 . A method as in  claim 13 , wherein the intermittent power source is a wind source. 
     
     
         16 . A method as in  claim 1 , wherein the compressed gas stream is below the triple point of carbon dioxide. 
     
     
         17 . A method as in  claim 1 , wherein the condensed-phase carbon dioxide component is separated from the light gas component by allowing the carbon dioxide to condense and precipitate from the compressed gas stream. 
     
     
         18 . A method as in  claim 1 , wherein the condensed-phase carbon dioxide component is separated from the light gas component by aerodynamic separation, filtration, agglomeration and/or by causing the carbon dioxide to condense on a cold surface 
     
     
         19 . A method as in  claim 18 , wherein the carbon dioxide component is accumulated on blocks of frozen carbon dioxide. 
     
     
         20 . A method as in  claim 18 , wherein the carbon dioxide component is accumulated on a mesh. 
     
     
         21 . A method as in  claim 1 , wherein the condensed-phase carbon dioxide component is separated from the light gas component by precipitating the carbon dioxide component on a cooled rotating drum. 
     
     
         22 . A method as in  claim 1 , wherein the condensed-phase carbon dioxide component is separated from the light gas component by precipitating the carbon dioxide on the surface of the second heat exchanger. 
     
     
         23 . A method as in  claim 22 , wherein the surface of the second heat exchanger is substantially free of aluminum. 
     
     
         24 . A method as in  claim 23 , further comprising a third heat exchanger having a second cooled surface for precipitating the carbon dioxide component and the cold compressed gas stream is caused to flow through the first heat exchanger and then the second heat exchanger in an alternating manner, wherein the condensed carbon dioxide component is removed from the first heat exchangers during a period when the cold compressed gas stream is flowing through the second heat exchanger. 
     
     
         25 . A system for efficiently separating carbon dioxide from a flue gas of a hydrocarbon processing plant, comprising
 a flue gas conduit configured to receive a flue gas from a hydrocarbon processing plant;   a compressor in fluid communication with the flue gas conduit, the compressor configured to receive flue gas and compress the flue gas to yield a compressed flue gas;   a first heat exchanger configured to dissipate heat from the compressed gas using a first coolant to yield a partially cooled gas stream;   a second heat exchanger having a coolant chamber and a flue gas chamber, the flue gas chamber having an inlet configured to receive the partially cooled gas stream downstream from the first heat exchanger and configured to dissipate heat to the coolant chamber to yield a cold compressed gas stream in the second flue gas chamber, wherein the coolant chamber is configured to receive the cold compressed gas stream downstream from the second flue gas chamber; and   a third heat exchange and/or a first expansion chamber in fluid communication with the second heat exchanger, the third heat exchanger and/or first expansion chamber configured to cool the cold compressed gas stream to yield a condensed carbon dioxide.   
     
     
         26 . A system as in  claim 25 , wherein the system includes the first expansion chamber and the first expansion chamber includes an expansion valve. 
     
     
         27 . A system as in  claim 25 , wherein the system includes a first expansion chamber and the first expansion chamber includes a turbine. 
     
     
         28 . A system as in  claim 25 , wherein the second heat exchanger is combined with a condenser separator and configured to condense an impurity component and remove the impurity component from the second heat exchanger as a side stream, wherein an outlet to the sidestream is upstream from an outlet for a condensed carbon dioxide stream. 
     
     
         29 . A system as in  claim 25 , further comprising means for separating solid carbon dioxide from the cold compressed gas stream. 
     
     
         30 . A system as in  claim 29 , wherein the means include a cold surface for accumulating solid carbon dioxide that condenses in the first expansion chamber during expansion of the cold compressed gas stream. 
     
     
         31 . A system as in  claim 30 , wherein the cold surface is provided by frozen CO 2 ; a mesh operably coupled to a shaking mechanism; and/or a rotating drum. 
     
     
         32 . A system as in  claim 29 , the means for separating includes a second expansion chamber and a gas-flow distribution switch upstream from the first and second expansion chambers, wherein the gas-flow distribution switch is configured to switch flue gas flow between the first expansion chamber and the second expansion chamber. 
     
     
         33 . A method for efficiently separating carbon dioxide from a flue gas of a hydrocarbon processing plant, comprising:
 (i) removing moisture from a flue gas of a hydrocarbon processing plant to yield an at least partially dried flue gas;   (ii) compressing the at least partially dried flue gas to yield a compressed-gas stream, wherein the compressed gas stream includes carbon dioxide;   (iii) reducing the temperature of the compressed-gas stream to a temperature T 1  using a first heat exchanger;   (iv) condensing one or more impurities in the compressed-gas stream using a third heat exchanger and removing the condensed impurities from the compressed-gas stream to yield a purified condensed gas stream that includes carbon dioxide;   (iv) reducing the temperature of the purified compressed-gas stream to a second temperature T 2  using a second heat exchanger or using a second heat exchanger in combination with expansion of the compressed-gas stream, wherein T 2 <T 1  and wherein at least a portion of the carbon dioxide from the purified compressed gas stream condenses, thereby yielding a purified solid or liquid condensed-phase carbon dioxide component and a light-gas component;   (v) separating the condensed-phase component from the light gas component to produce a condensed-phase stream and a light-gas stream; and   (vi) using at least a portion of the light-gas stream in the second heat exchanger.   
     
     
         34 . A method as in  claim 33 , wherein the one or more impurities are selected from the group consisting of, SO 2 , NO 2 , HCl, or Hg. 
     
     
         35 . A method as in  claim 33 , wherein the concentration of each of the one or more impurities is less than 100 ppm in the purified condensed-flue gas. 
     
     
         36 . A method as in  claim 33 , wherein the concentration of each of the one or more impurities is less than 10 ppm in the purified condensed-flue gas. 
     
     
         37 . A method as in  claim 33 , wherein the concentration of each of the one or more impurities is less than 1 ppm in the purified condensed-flue gas.