Methods for optimizing gas utilization

Abstract

The invention provides for the optimal utilization of gas by a fermentation process, whereby the various components within the gas stream are separated to increase the efficiency of the microorganisms. The invention is capable of tailoring the composition of the gas being used by the fermentation process so as to enhance the production of various products. The invention is capable of applying such controlled separation and utilization of gas to produce different products in two fermentation processes in series. The invention is also capable of applying such controlled separation and utilization of gas to produce one product in a first fermentation process, which may be converted to a different product in a second fermentation process. The invention is additionally capable of mitigating culture inhibition.

1 . A method for optimizing the flow of gas to fermentation processes in series, the method comprising:
 a. separating a gas stream derived from at least one industrial source into a hydrogen rich stream and a hydrogen depleted stream using at least one hydrogen separation module;   b. fermenting at least a portion of the hydrogen rich stream in a first fermentation process using at least one reactor comprising a liquid nutrient medium containing a culture of one or more C1-fixing microorganism to produce a first fermentation product; and   c. fermenting at least a portion of the hydrogen depleted stream in a second fermentation process comprising at least one reactor comprising a liquid nutrient medium containing a culture of one or more C1-fixing microorganism to produce a second fermentation product,
 wherein at least a portion of the first fermentation product is passed to the second fermentation process; and wherein the hydrogen rich stream comprises H 2  and CO at a H 2  to CO ratio from 2:1 to 5:1 and the hydrogen depleted stream comprises H 2  and CO at a H 2  to CO ratio from 0.05:1 to less than 2:1. 
   
     
     
         2 . The method of  claim 1 , wherein the first fermentation product is acetic acid. 
     
     
         3 . The method of  claim 2 , wherein at least a portion of the acetic acid from the first fermentation process is converted to ethanol in the second fermentation process. 
     
     
         4 . The method of  claim 1 , wherein the hydrogen separation module is a pressure swing adsorption process. 
     
     
         5 . The method of  claim 1 , wherein the industrial source is selected from the group consisting of carbohydrate fermentation, gas fermentation, cement making, pulp and paper making, steel making, oil refining and associated processes, petrochemical production, coke production, anaerobic or aerobic digestion, gasification, natural gas extraction, methane reformation, oil extraction, metallurgical processes, for production and/or refinement of aluminium, copper, and/or ferroalloys, geological reservoirs, and catalytic processes. 
     
     
         6 . The method of  claim 1 , wherein at least a portion of the gas stream is comprised of a blast furnace top gas from a metallurgical process. 
     
     
         7 . The method of  claim 1 , wherein at least a portion of a vent gas produced in the first fermentation process is recycled to the hydrogen rich stream. 
     
     
         8 . The method of  claim 7 , wherein at least a portion of the vent gas produced in the first fermentation process is passed through a pressure swing adsorption process prior to being recycled to the hydrogen rich stream. 
     
     
         9 . The method of  claim 1 , wherein at least a portion of a vent gas produced in the second fermentation process is recycled to the hydrogen depleted stream. 
     
     
         10 . The method of  claim 9 , wherein at least a portion of the vent gas produced in the second fermentation process is passed through a pressure swing adsorption process prior to being recycled to the hydrogen depleted stream. 
     
     
         11 . The method of  claim 1 , wherein the C1-fixing microorganism is selected from the group consisting of  Moorella, Clostridium, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter, Methanosarcina , and  Desulfotomaculum.    
     
     
         12 . The method of  claim 1 , wherein the C1-fixing microorganism is  Clostridium autoethanogenum.    
     
     
         13 . A method for optimizing gas flow to a fermentation process, the method comprising:
 a. fermenting at least a portion of a gas stream from an industrial source using at least one reactor comprising a liquid nutrient medium containing a culture of one or more C1-fixing microorganism to produce a fermentation product and a vent gas stream; and   b. recycling at least a portion of the vent gas stream to the bioreactor,
 wherein the recycling of at least a portion of the vent gas stream to the bioreactor reduces and/or mitigates the potential inhibition of the culture. 
   
     
     
         14 . The method of  claim 13 , wherein at least a portion of the vent gas is passed through a pressure swing adsorption process prior to being recycled to the bioreactor. 
     
     
         15 . The method of  claim 14 , wherein the pressure swing adsorption process removes at least a portion of at least one component selected from the group consisting of carbon dioxide, inorganic hydrocarbons, tars, organic nitrogen, and organic and inorganic sulfur from the vent gas stream. 
     
     
         16 . The method of  claim 14 , wherein the pressure swing adsorption process simultaneously removes at least a portion of at least two components selected from the group consisting of carbon dioxide, inorganic hydrocarbons, tars, organic nitrogen, and organic and inorganic sulfur from the vent gas stream.