Method for injecting a feed gas stream into a vertically extended column of liquid

Abstract

A process for conversion of syngas to liquid products that serve as surface acting agents uses the gas stream at a relatively low pressure to eliminate the use of a compressor. The process uses a liquid stream as the primary energy input to a gas injector that intensely mixes gas and the liquid with reduced compression costs while the presence of the liquid product maintains the gas-liquid dispersion as it flows downward to build a static pressure head. The process lowers the required gas pressure by adjusting the elevation of the gas injector such that a conduit receives the gas-liquid dispersion from the outlet of the injector and confines it as it travels downward to enter the bottom of a column of liquid. The liquid product provides a surface acting agent that prolongs the creation and duration of microbubbles in the gas-liquid dispersion.

What is claimed is: 
     
         1 . A process for converting a feed gas stream, comprising at least one of CO or a mixture of CO 2  and H 2 , to a liquid product by contact with a fermentation liquid wherein the liquid product reduces the surface tension of the fermentation liquid, said process comprising:
 retaining an aqueous fermentation liquid comprising a liquid product and microorganisms in a vessel to partially fill the vessel to a height of at least 10 meters;   withdrawing fermentation liquid from said vessel at a withdrawal point and pumping said fermentation liquid as a working fluid to a gas injector having a vertical injector location no lower than the proximate location of the withdrawal point;   passing at least a portion of the feed gas stream into the gas injector at a pressure of not more than 100 kPa gauge;   mixing the feed gas stream with the working fluid in the gas injector and using the pumping of the working fluid as the primary energy input to create a gas-liquid dispersion from the feed gas stream and the working fluid;   downwardly transporting the gas-liquid dispersion from the gas injector in a dispersion conduit having a uniform flow area;   discharging the gas-liquid dispersion from the dispersion conduit into the vessel at a discharge point located at least 10 meters below the gas injector;   converting at least one of CO or a mixture of CO 2  and H 2  to the liquid product in said vessel by contact of the microorganisms with fermentation liquid that contains dissolved feed gas from the gas-liquid dispersion; and,   passing a portion of the fermentation liquid from the vessel to a product recovery zone and recovering a product stream comprising the liquid product from said product recovery zone.   
     
     
         2 . The process of  claim 1  wherein the gas injector receives a first stream of fermentation liquid and a second stream of fermentation liquid is mixed with the gas-liquid dispersion downstream of the gas injector and upstream of the discharge point. 
     
     
         3 . The process of  claim 1  wherein the liquid product comprises alcohol and the fermentation liquid contains alcohol at a total concentration of at least 0.05 wt %. 
     
     
         4 . The process of  claim 1  wherein the gas injection device comprises a venturi-type eductor, a jet injector, or a slot injector. 
     
     
         5 . The process of  claim 1  wherein the vertical injector location is at least 15 meters above the withdrawal point. 
     
     
         6 . The process of  claim 1  wherein the vessel retains an off-gas above the surface of the fermentation liquid, a portion of the off-gas passes to the gas injection device with the feed gas and the ratio of the feed gas and off-gas to the working fluid is from 1/1 to 3/1 actual m 3 /m 3 . 
     
     
         7 . The process of  claim 6  wherein feed gas stream and the off-gas stream enter the gas injector at a pressure greater than atmospheric pressure. 
     
     
         8 . The process of  claim 6  wherein the feed gas stream flows to a first gas injector that receives a first portion of the fermentation liquid and the off-gas stream flows to second gas injector that receives a second portion of the fermentation liquid. 
     
     
         9 . A process for converting a feed gas stream containing CO, CO 2  and H 2  to ethanol, said process comprising:
 partially filling a vessel with an aqueous fermentation liquid comprising ethanol at a concentration of at least 0.05 wt % and microorganisms to a height such that the fermentation liquid creates more than 100 kPa gauge of hydrostatic pressure and off-gas collects above the surface of the fermentation liquid in the vessel;   withdrawing fermentation liquid from said vessel at a withdrawal point located below the surface of the fermentation liquid and pumping said fermentation liquid as a working fluid to a gas injector;   passing at least a portion of the feed gas stream and off-gas from the vessel into the gas injector at a pressure of not more than 40 kPa gauge;   mixing the feed gas stream and off-gas stream with the working fluid in the gas injector and using the pumping of the working fluid as the primary energy input to create a gas-liquid dispersion from the feed gas stream, the off-gas stream and the working fluid;   downwardly transporting the gas-liquid dispersion from the gas injector in a dispersion conduit having a uniform flow area;   discharging the gas-liquid dispersion from the dispersion conduit into the vessel at a discharge point located at least 15 meters below the surface of the fermentation liquid;   converting CO and CO 2  and H 2  to ethanol in said vessel by contact of the microorganisms with fermentation liquid that contains dissolved feed gas from the gas-liquid dispersion; and,   passing a portion of the fermentation liquid from the vessel to an ethanol recovery zone and recovering a product stream comprising ethanol from said product recovery zone.   
     
     
         10 . The process of  claim 9  wherein the vertical injector location is above the surface of the liquid. 
     
     
         11 . The process of  claim 9  wherein the ratio of the feed gas and off-gas to the working fluid is from 1/1 to 3/1 actual m 3 /m 3 . 
     
     
         12 . The process of  claim 9  wherein feed gas stream and the off-gas stream enter the gas injector at a pressure greater than atmospheric pressure. 
     
     
         13 . The method of  claim 9  wherein microorganisms comprises a mono-culture or a co-culture of any of  Clostridium ragsdalei, Butyribacterium methylotrophicum, Clostridium Ljungdahli, Clostridium Coskatii  and  Clostridium Autoethanogenum.