Separation of co2 from gas mixtures

Abstract

Processes for separating carbon dioxide from a gas mixture that comprises CO 2 and N 2 that are based upon formation of gas hydrates, and systems useful for implementing such processes, are disclosed.

1 . A system for separation of CO 2  from combustion product or other gas comprising a hydrate formation reactor (HFR) that comprises an outer vessel configured:
 with a plurality of stages arranged with a first stage proximal a first end of the vessel and second and any subsequent stages successively more proximal a second end of the vessel;   one or more gas feed inlets placed at a distance from the first end of the vessel the same as said distance of a stage that is a second or subsequent stage and configured to feed a gas stream into the vessel;   one or more aqueous phase inlets configured to feed an aqueous solution into the first end of the vessel or proximate thereto;   one or more hydrate slurry outlets configured to draw off a hydrate slurry stream from the first end of the vessel or proximate thereto;   one or more gas product outlets configured to draw off a gas product stream from the second end of the vessel or proximate thereto; and   a temperature control system effective to establish a temperature gradient or a series of temperature steps from a first temperature T 1  in a region proximate to the first end of the vessel to a second temperature T 2  in a region proximate to the second end of the vessel, and controlling the temperature at each of the stages, wherein T 1> T 2 ;   
       wherein the gas stream and the aqueous phase flow in a countercurrent manner through the vessel. 
     
     
         2 . The system of  claim 1  that further comprises a solid-liquid separator configured to receive an aqueous hydrate slurry from the hydrate slurry outlet for separation into an aqueous phase product and a solid hydrate. 
     
     
         3 . The system of  claim 2  in which the solid-liquid separator comprises an aqueous phase recirculating line that feeds the aqueous phase product of the solid-liquid separator into the vessel. 
     
     
         4 . The system of  claim 3  in which the recirculating line includes a cooling plant for cooling the aqueous phase liquid product. 
     
     
         5 . The system of  claim 1  that further comprises a hydrate decomposition facility including a hydrate decomposition plant for decomposing a hydrate and a vapor-liquid separator for separating a vapor product from an aqueous phase and that is operably connected to the hydrate formation reactor so as to receive a hydrate slurry from the hydrate slurry outlet of the hydrate formation reactor. 
     
     
         6 . The system of  claim 5 , in which the hydrate decomposition plant comprises a heater for raising the temperature of the hydrate. 
     
     
         7 . The system of system of  claim 5 , in which the hydrate decomposition plant is one that lowers the pressure of a hydrate slurry. 
     
     
         8 . The system of  claim 5 , that further comprises an aqueous phase recirculating line that feeds the aqueous phase product of the vapor-liquid separator into the vessel. 
     
     
         9 . The system of  claim 8 , in which the aqueous phase recirculating line includes a cooling plant for cooling the aqueous phase liquid product. 
     
     
         10 . The system of  claim 1  that further comprises an inlet for adding a hydrate promoter to the gas feed stream. 
     
     
         11 . The system of  claim 2  that further comprises an inlet for adding a hydrate promoter to the gas feed stream. 
     
     
         12 . The system of  claim 8  that further comprises an inlet for adding a hydrate promoter to the gas feed stream. 
     
     
         13 . The system of  claim 3 , wherein the aqueous phase recirculating line includes an input for adding a hydrate promoter to the aqueous phase. 
     
     
         14 . The system of  claim 8 , wherein the aqueous phase recirculating line includes an input for adding a hydrate promoter to the aqueous phase. 
     
     
         15 . The system of  claim 12 , wherein the aqueous phase recirculating line includes an input for adding a hydrate promoter to the aqueous phase. 
     
     
         16 . The system of  claim 13  that further comprises an inlet for adding a hydrate promoter to the gas feed stream. 
     
     
         17 . The system of  claim 1 , in which the product gas outlet(s) are configured to transport the product gas to a storage facility for storing the product gas at a pressure above atmospheric pressure. 
     
     
         18 . The system of  claim 1 , in which the product gas outlet(s) are configured to transport the product gas to a turbine for generating electricity. 
     
     
         19 . A process for purifying CO 2  from a gas comprising N 2 , the process comprising intimately contacting a feed gas stream comprising CO 2  and N 2  gases and an aqueous phase stream in a countercurrent flow to form a CO 2 -rich hydrate in the aqueous phase, a temperature T f  being maintained at a gas feed stage f in the countercurrent flow, a temperature T 2  such that T 2 <T f  being maintained at a stage n>f, and a temperature T 1  being maintained at a stage m≤f such that T 1 ≥T f ;
 wherein: 
 T 2  is in the range from the incipient vapor temperature for CO 2  to the incipient hydrate temperature for CO 2  at the operating pressure of the process, and 
 T 1  is a temperature at or below a temperature of convergence of the incipient CO 2  hydrate formation and incipient CO 2  vapor formation curves at the operating pressure of the process. 
 
     
     
         20 . The process of  claim 19 , further comprising separating the gas phase from the aqueous phase and collecting a hydrate slurry formed in the aqueous phase and comprising hydrate particles enriched in CO 2 . 
     
     
         21 . The process of  claim 20 , further comprising concentrating the hydrate from the hydrate slurry and sequestering the hydrate. 
     
     
         22 . The process of  claim 21 , in which the hydrate is sequestered on the deep ocean floor or buried in the sea floor, or in which the hydrate is encapsulated. 
     
     
         23 . The process of  claim 19 , further comprising collecting a N 2 -rich gas from the gas stream after contact with the aqueous phase. 
     
     
         24 . The process of  claim 20 , further comprising collecting a N 2 -rich gas from the separated gas. 
     
     
         25 . The process of  claim 24  that is conducted at 2200 psia, T 2  is from 31 to 34° F. (−0.5 to 1.1° C.) and T 1  is about 54° F. (12.2° C.). 
     
     
         26 . The process of  claim 24 , in which there are 3 stages and T f  is about 33° F. (0.5° C.), T 1  is about 35° F. (1.6° C.) and T 2  is about 31° F. (−0.5° C.). 
     
     
         27 . The process of  claim 19 , in which the feed gas stream comprises a hydrate promoter. 
     
     
         28 . The process of  claim 19 , in which the aqueous phase stream comprises a hydrate promoter. 
     
     
         29 . The process of  claim 27 , in which the aqueous solution stream comprises a hydrate promoter.