METHOD FOR INJECTING A FEED GAS STREAM INTO A VERTICALLY EXTENDED COLUMN OF LIQUID
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.
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.