Systems and methods for recovering carbon dioxide from industrially relevant waste streams, especially ethanol fermentation processes, for application in food and beverage production

Abstract

A system for recovering CO2 via liquefaction and purification from a vented CO2 gas stream comprising a compressor; a dehydrator; a scrubber; a refrigerator having one or more stages; and a separation subsystem adapted to ensure non-condensable gas content in the final product meets industry standards. The liquid CO2 product is of sufficient purity to be used in applications requiring beverage-grade CO2. The system can be utilized as a single-brewery installation to reduce venting from ethanol fermenters to an absolute minimum, produce a high purity liquid CO2 product for use in-process or external sales, and offset the purchasing of expensive, industrial CO2 of inferior purity.

What is claimed is: 
     
         1 . An apparatus for recovering via purification and liquefaction of carbon dioxide gas from a vented CO2 waste gas stream, comprising:
 a chassis adapted for installation inside a space-limited production facility;   one or more compressors for compressing the raw CO2 gas stream;   one or more dehydrators for removing water from the compressed CO2 gas stream;   one or more scrubbers containing solid-state adsorbent for deodorizing and purifying the inlet CO2 gas stream;   a refrigerator having one or more stages for lowering a temperature of the dehydrated, deodorized, compressed CO2 stream; and   a separation subsystem system adapted to separate the liquefied CO2 product from any remaining contamination by non-condensable gases, especially oxygen.   
     
     
         2 . The apparatus of  claim 1 , wherein the final oxygen content is less than 30 parts per million. 
     
     
         3 . The apparatus of  claim 1 , wherein the final water content is less than 20 parts per million. 
     
     
         4 . The apparatus of  claim 1 , wherein the liquid CO2 product has no foreign color, taste, or odor. 
     
     
         5 . The apparatus of  claim 1 , wherein the liquid CO2 product meets a beverage-grade standard. 
     
     
         6 . The apparatus of  claim 1 , wherein the one or more compressors compress the raw natural gas stream to a pressure range of 75 psia to 300 psia. 
     
     
         7 . The apparatus of  claim 1 , wherein the chassis is mounted on a cart having one or more wheels. 
     
     
         8 . The apparatus of  claim 1 , wherein the refrigerator further comprises:
 a high-stage refrigeration loop having at least one heat exchanger for lowering the temperature of the dehydrated, deodorized, compressed CO2 gas stream; and   a low-stage refrigeration loop having at least one heat exchanger for further lowering the temperature of the dehydrated, deodorized, compressed CO2 gas stream.   
     
     
         9 . The apparatus of  claim 1 , wherein the refrigerator further comprises:
 an autocascade loop having mixed refrigerants for lowering the temperature of the dehydrated, deodorized, compressed CO2 gas stream.   
     
     
         10 . The apparatus of  claim 9 , wherein the mixed refrigerants are hydrocarbons. 
     
     
         11 . The apparatus of  claim 9 , wherein the mixed refrigerants are nonflammable refrigerants. 
     
     
         12 . The apparatus of  claim 1 , wherein the refrigerator cools the compressed CO2 gas stream to a temperature range of −15° C. to −55° C. sufficient to liquefy the entire CO2 stream in a single heat exchanger. 
     
     
         13 . The apparatus of  claim 1 , wherein one or more of the dehydrators employ a desiccant bed. 
     
     
         14 . The apparatus of  claim 13 , wherein two desiccant beds are employed in alternation, and wherein heat required to dry the two desiccant beds is derived from waste heat from a power generator that drives the compressors and the refrigerator. 
     
     
         15 . The apparatus of  claim 1 , wherein the separation subsystem comprises a phase separator. 
     
     
         16 . The apparatus of  claim 1 , wherein the separation subsystem comprises a liquid storage dewar. 
     
     
         17 . The apparatus of  claim 1 , wherein the separation subsystem comprises one or more cyclones to separate liquids from gasses. 
     
     
         18 . A method for recovering a liquid CO2 product from a vented CO2 gas stream, comprising:
 a compression step for compressing the raw CO2 gas stream utilizing a compressor to a pressure range of 75 to 300 psia;   a dehydration step for removing water from the compressed CO2 gas stream utilizing one or more condensers and one or more desiccant beds;   a deodorizing step for removing trace organic compounds, flavors, and odors from the dehydrated, compressed CO2 gas stream utilizing an appropriate solid-state adsorbent;   a refrigeration step for reducing a temperature of the dehydrated, compressed, deodorized CO2 gas stream utilizing a refrigerator having one or more stages to a temperature range of −15° C. to −55° C.; and   a separation step for driving the non-condensable gas contamination, especially oxygen, in the final liquid CO2 product below relevant purity standards.   
     
     
         19 . The method of  claim 18 , further comprising:
 a transportation step for bringing a mobile CO2 recovery system inside a cramped production craft brewery that is venting fermenter gas; and   a deployment step for connecting said CO2 recovery system to a vented CO2 gas source.   
     
     
         20 . The method of  claim 18 , wherein the final oxygen content is less than 30 ppm. 
     
     
         21 . The method of  claim 18 , further comprising:
 vaporizing the liquid CO2 product to purge tanks, vessels, and lines.   
     
     
         22 . The method of  claim 18 , further comprising:
 vaporizing the liquid CO2 product to carbonate beverages intended for sale.   
     
     
         23 . The method of  claim 18 , further comprising:
 Re-selling the liquid CO2 product to local consumers of high quality CO2.   
     
     
         24 . The method of  claim 18 , wherein the refrigeration step utilizes an autocascade refrigerator having mixed nonflammable hydrocarbon refrigerants. 
     
     
         25 . The method of  claim 18 , wherein the refrigeration step cools the natural gas stream to a temperature range of −37° C. to −43° C. 
     
     
         26 . The method of  claim 18 , wherein two desiccant beds are employed in alternation, and wherein convection required to dry the two desiccant beds is derived from CO2 gas vented from storage. 
     
     
         27 . A system for recovering a vented CO2 gas stream into a liquid CO2 product of sufficient purity for the downstream application, comprising:
 one or more compressors for compressing the vented CO2 gas stream;   a dehydrator subsystem for removing water from the compressed CO2 gas stream;   a deodorizing subsystem for removing trace organic compounds, flavors, and odors from the dehydrated, compressed CO2 gas stream;   a refrigeration subsystem for lowering the temperature of the dehydrated, compressed, deodorized CO2 gas stream to a low temperature, comprising an auto-cascade refrigeration loop having mixed nonflammable hydrocarbon refrigerants; and   a separation subsystem adapted to remove non-condensable contaminants from the liquid CO2 product to meet specific purity standards.   
     
     
         28 . The system of  claim 27 , wherein the dehydration subsystem employs two desiccant beds alternation, wherein convection required to dry the two desiccant beds is derived from CO2 gas vented from the liquid storage dewar. 
     
     
         29 . The system of  claim 27 , wherein the oxygen content in the liquid CO2 product is less than 30 ppm. 
     
     
         30 . The system of  claim 27 , further comprising a chassis for holding system components for brewery installation, said chassis mountable to a cart, an indoor floor, or an outdoor surface. 
     
     
         31 . The system of  claim 27 , wherein the refrigeration subsystem comprises:
 a high-stage refrigeration loop having at least one heat exchanger for lowering a temperature of the dehydrated, compressed CO2 gas stream; and   a low-stage refrigeration loop having at least one heat exchanger for further lowering the temperature of the dehydrated, CO2 natural gas stream.   
     
     
         32 . The system of  claim 27 , wherein the refrigeration subsystem cools the vented CO2 gas stream to a temperature range of −15° C. to −55° C. sufficient to liquefy the entire process stream in a single heat exchanger. 
     
     
         33 . A method for recovering vented CO2 gas, comprising:
 compressing the raw CO2 gas stream to a pressure range of 75 to 300 psia;   reducing a temperature of the CO2 gas stream to a temperature range of −15° C. to −55° C.; and   separating non-condensable gas components from the liquid CO2 product in a phase separator or liquid storage vessel.   
     
     
         36 . The method of claim  35 , further comprising:
 removing water from the raw natural gas stream to achieve a final aqueous content below 20 ppm.