Recovery of higher alcohols from dilute aqueous solutions

Abstract

This invention is directed to methods for recovery of C3-C6 alcohols from dilute aqueous solutions, such as fermentation broths. Such methods provide improved volumetric productivity for the fermentation and allows recovery of the alcohol. Such methods also allow for reduced energy use in the production and drying of spent fermentation broth due to increased effective concentration of the alcohol product by the simultaneous fermentation and recovery process which increases the quantity of alcohol produced and recovered per quantity of fermentation broth dried. Thus, the invention allows for production and recovery of C3-C6 alcohols at low capital and reduced operating costs.

What is claimed is: 
     
         1 . A retrofit ethanol production plant comprising:
 a. a feedstock pretreatment unit;   b. one or more fermentation units;   c. one or more liquid-liquid separation vessels; and   d. a beer still;   wherein said retrofit ethanol production plant is configured to produce a C3-C6 alcohol.   
     
     
         2 . The retrofit ethanol production plant of  claim 1 , further comprising a flash tank. 
     
     
         3 . The retrofit ethanol production plant of  claim 1 , where said C3-C6 alcohol is isobutanol. 
     
     
         4 . The retrofit ethanol production plant of  claim 1 , further comprising one or more distillation columns. 
     
     
         5 . The retrofit ethanol production plant of  claim 2 , wherein said flash tank is fluidly coupled to said one or more fermentation units. 
     
     
         6 . The retrofit ethanol production plant of  claim 5 , wherein said flash tank is configured to receive a liquid feed stream comprising said C3-C6 alcohol from said one or more fermentation units. 
     
     
         7 . The retrofit ethanol production plant of  claim 6 , wherein said flash tank is configured to flash vaporize said liquid feed stream comprising said C3-C6 alcohol and provide:
 (i) a vapor stream enriched in said C3-C6 alcohol relative to said liquid feed stream; and   (ii) a liquid stream depleted in said C3-C6 alcohol relative to said liquid feed stream.   
     
     
         8 . The retrofit ethanol production plant of  claim 7 , further comprising a condenser fluidly coupled to said flash tank and configured to receive and condense said vapor stream. 
     
     
         9 . The retrofit ethanol production plant of  claim 8 , wherein said one or more liquid-liquid separation vessels are fluidly connected to said condenser and are configured to receive said condensed vapor stream. 
     
     
         10 . The retrofit ethanol production plant of  claim 7 , wherein said liquid stream depleted in said C3-C6 alcohol is conducted from said flash tank to said one or more fermentation units. 
     
     
         11 . The retrofit ethanol production plant of  claim 9 , wherein said condensed vapor stream forms a C3-C6 alcohol-rich liquid phase and a water-rich liquid phase, and said one or more liquid-liquid separation vessels are configured to separate said C3-C6 alcohol-rich liquid phase and a water-rich liquid phase. 
     
     
         12 . The retrofit ethanol production plant of  claim 11 , wherein said beer still is fluidly coupled to said one or more liquid-liquid separation vessels and said beer still is configured to receive said water-rich liquid phase. 
     
     
         13 . The retrofit ethanol production plant of  claim 12 , wherein said beer still is configured to provide:
 (i) an overhead vapor stream enriched in said C3-C6 alcohol relative to said water-rich liquid phase; and   (ii) a bottoms liquid stream depleted in said C3-C6 alcohol relative to said water-rich liquid phase.   
     
     
         14 . The retrofit ethanol production plant of  claim 13 , wherein said beer still is fluidly coupled to a dryer unit. 
     
     
         15 . The retrofit ethanol production plant of  claim 14 , wherein said dryer unit is configured to receive said bottoms liquid stream and provide:
 (i) a stream comprising dried solids; and   (ii) a vapor stream comprising water.   
     
     
         16 . The retrofit ethanol production plant of  claim 11 , further comprising one or more distillation columns fluidly coupled to said one or more liquid-liquid separation vessels, wherein said one or more distillation columns are configured to receive said alcohol-rich liquid phase. 
     
     
         17 . The retrofit ethanol production plant of  claim 16 , wherein said one or more distillation columns are configured to provide:
 (i) an overhead vapor stream depleted in said C3-C6 alcohol relative to said C3-C6 alcohol-rich liquid; and   (ii) a bottoms liquid stream enriched in said C3-C6 alcohol relative to said C3-C6 alcohol-rich liquid.   
     
     
         18 . The retrofit ethanol production plant of  claim 17 , wherein said bottoms liquid comprises at least 90 wt % C3-C6 alcohol. 
     
     
         19 . The retrofit ethanol production plant of  claim 17 , wherein said bottoms liquid comprises at least 95 wt % C3-C6 alcohol. 
     
     
         20 . The retrofit ethanol production plant of  claim 17 , wherein said bottoms liquid comprises at least 98 wt % C3-C6 alcohol. 
     
     
         21 . The retrofit ethanol production plant of  claim 2 , wherein said flash tank is configured to operate at a pressure of from about 0.025 bar to about 10 bar. 
     
     
         22 . The retrofit ethanol production plant of  claim 1 , wherein the output of the retrofit ethanol production plant is at least about 90% of the C3-C6 alcohol equivalent of the ethanol maximum output of the ethanol production plant before retrofit. 
     
     
         23 . The retrofit ethanol production plant of  claim 1 , wherein the output of the retrofit ethanol production plant is at least about 95% of the C3-C6 alcohol equivalent of the ethanol maximum output of the ethanol production plant before retrofit. 
     
     
         24 . The retrofit ethanol production plant of  claim 1 , further comprising a vent system collection system fluidly coupled to one or more process units in said retrofit ethanol production plant configured to receive one or more vent streams from said one or more process units. 
     
     
         25 . The retrofit ethanol production plant of  claim 24 , wherein said vent system collection system is configured to condense C3-C6 alcohol vapor from said one or more vent streams. 
     
     
         26 . The retrofit ethanol production plant of  claim 24 , wherein said vent system collection system is configured to capture CO2 from said one or more vent streams. 
     
     
         27 . The retrofit ethanol production plant of  claim 1 , configured to operate and produce C3-C6 alcohol continuously. 
     
     
         28 . A retrofit ethanol production plant comprising:
 a. a feedstock pretreatment unit;   b. one or more fermentation units;   c. a flash tank;   d. a liquid-liquid separation vessel;   e. a beer still;   f. one or more distillation columns;   g. a vent collections unit; and   f. a dryer unit;   wherein said retrofit ethanol production plant is configured to produce isobutanol.   
     
     
         29 . A method for constructing the retrofit ethanol production plant of  claim 1 , comprising installing said one or more liquid-liquid separation vessels in an ethanol production plant. 
     
     
         30 . The method of  claim 29 , further comprising installing a flash tank in said ethanol production plant.