Volatile organic compound recovery system and method

Abstract

The present invention provides for passive VOC recovery in the fermentation process that does not affect or minimally affects the conditions within the fermentor vessel and does not affect or minimally affects the conditions within the headspace of the fermentor vessel itself while using the production of CO 2 emitted during the fermenting process as the source of driving energy to move a portion of the gaseous/vaporous material in the headspace of the fermentor through an appropriately sized conduit to a chilled surface condensing device to condense the VOCs (principally ethanol) for recovery and to exhaust the CO 2 to the atmosphere or to recover the CO 2 for other uses. The conduit from the headspace of the fermentor to the condenser is sized to provide a flow restriction in a selected range such that the headspace equilibria are not affected while allowing a portion of the gaseous/vaporous material in the headspace to move through the conduit in response to the generation of the CO 2 during the fermentation process.

What is claimed is: 
     
         1 . A method of recovering volatile organic compounds produced as a consequence of yeast-based fermentation processes, comprising:
 providing a condenser coupled with a fermentation vessel;   setting a variable condenser capacity of the condenser based upon a flow of vapors passing from a head space of the fermentation vessel to the condenser via a bleed-off line; and   condensing the vapors with the condenser at the set condenser capacity.   
     
     
         2 . The method of  claim 1 , wherein the step of setting the condenser capacity comprises restricting a flow of a chilled fluid with an on/off valve. 
     
     
         3 . The method of  claim 1 , wherein the step of setting the variable condenser capacity further comprising steps of:
 monitoring the flow of vapors passing from the head space of the fermentation vessel to the condenser via the bleed-off line; and   controlling the flow of vapors at the bleed-off line by operating an electrical controller.   
     
     
         4 . The method of  claim 1 , wherein the step of setting the variable condenser capacity based upon the flow of vapors further comprising steps of:
 monitoring the flow of vapors passing from the head space of the fermentation vessel to the condenser via the bleed-off line;   comparing the flow of vapors to at least one flow set point; and   setting the condenser capacity based on whether the flow of vapors is greater than or less than the at least one flow set point.   
     
     
         5 . The method of  claim 4 , wherein the flow set point comprises a flow rate between 1000 feet per minute and 2000 feet per minute. 
     
     
         6 . The method  claim 4 , wherein the flow set point comprises a target flow corresponding to a desired pressure equilibrium within the head space. 
     
     
         7 . The method of  claim 1 , wherein the condenser comprises a plurality of individual condenser modules, each of the individual condenser modules fluidly coupled to the bleed-off line via a respective damper, and wherein step of setting a condenser capacity based on the monitored flow further comprises:
 monitoring the flow of vapors passing from the head space of the fermentation vessel to the condenser via the bleed-off line   comparing the flow of vapors to at least one flow set point; and   adjusting at least one damper from the plurality of dampers such based on whether the flow of vapors is greater or less than the at least one flow set point, thereby adjusting the amount of the vapor passing through to the respective condenser of the at least one damper.   
     
     
         8 . The method of  claim 7 , wherein the step of setting the condensing capacity further comprises incrementally setting the condensing capacity by changing the at least one damper from an on state to an off state, or from an off state to an on state. 
     
     
         9 . The method of  claim 1 , wherein the condenser comprises a plurality of individually adjustable condensation pathways and wherein the step of setting a condenser capacity further comprises steps of:
 monitoring the flow of vapors passing from the head space of the fermentation vessel to the condenser via the bleed-off line   adjusting an amount of condensation fluid passing through at least one of the condensation pathways based on whether the flow of vapors is greater than or less than the at least one flow set point.   
     
     
         10 . The method of  claim 9 , wherein the flow comprises a flow volume entering the condenser and the flow set point corresponds to an amount of liquid EtOH condensate and CO 2  removed from the condenser. 
     
     
         11 . The method of  claim 1 , wherein the step of setting the variable condenser capacity further comprising steps of:
 monitoring at least one of volume or temperature of a condensate at the condenser; and   controlling a flow of vapors at the bleed-off line by operating an electrical controller   
     
     
         12 . The method of  claim 3 , further comprising maintaining a temperature of the bleed-off line greater than a temperature of the passing vapors. 
     
     
         13 . The method of  claim 3 , wherein the monitored flow comprises at least one of a flow rate, a flow temperature, a flow volume, and a flow pressure. 
     
     
         14 . The method of  claim 1 , wherein the condenser capacity is sufficient to condense at least 35% of passing ethanol vapor into a liquid condensate over a period of time. 
     
     
         15 . A system for recovering volatile organic compounds produced as a consequence of yeast-based fermentation processes, comprising:
 a condenser having adjustable condenser capacity;   a bleed-off line coupled to the condenser at a first end, and configured to be coupled to a fermentation vessel at a second end;   a controller programmed to execute a step of setting a variable condenser capacity of the condenser based upon a flow of vapors passing from a head space of the fermentation vessel to the condenser via the bleed-off line.   
     
     
         16 . The system of  claim 15 , further comprising a flow monitor coupled to the bleed-off line, wherein the flow monitor is configured to monitor a flow of vapors passing through the bleed-off line, the controller is further programmed to execute steps of:
 receiving a measurement from the flow monitor corresponding to the flow of vapors; and   setting a condenser capacity of the condenser based on the monitored flow.   
     
     
         17 . The system of  claim 16 , wherein the controller is programmed to set the condenser capacity of the condenser by executing the steps of:
 comparing the monitored flow to at least one flow set point; and   setting the condenser capacity based on whether the monitored flow is greater than or less than the at least one flow set point.   
     
     
         18 . The system of  claim 17 , wherein the flow set point comprises a target flow corresponding to a desired equilibrium within a head space of the fermentation vessel. 
     
     
         19 . The system of  claim 16 , wherein:
 the condenser further comprises a plurality of individual condenser modules, each of the individual condenser modules fluidly coupled to the bleed-off line via a respective damper, and   the controller is further programmed to set a condenser capacity based on the monitored flow by executing the steps of:   comparing the monitored flow to at least one flow set point; and   adjusting at least one damper from the plurality of dampers such based on whether the monitored flow is greater or less than the at least one flow set point, thereby adjusting the amount of the vapor passing through to the respective condenser of the at least one damper.   
     
     
         20 . The system of  claim 19 , wherein the at least one damper is a bi-state damper, configured to be changed from an on state to an off state or from an off state to an on state. 
     
     
         21 . The method of  claim 15 , wherein:
 the condenser comprises a plurality of individually adjustable condensation pathways; and   the controller is programmed to set the condenser capacity by adjusting an amount of condensation fluid passing through at least one of the condensation pathways based on whether the monitored flow is greater than or less than the at least one flow set point.   
     
     
         22 . The method of  claim 21 , wherein the flow comprises a flow volume entering the condenser and the flow set point corresponds to an amount of liquid ethanol condensate and CO 2  removed from the condenser. 
     
     
         23 . The method of  claim 16 , wherein the monitored flow comprises at least one of a flow rate, a flow temperature, a flow volume and a flow pressure of the passing vapors.