Patent ID: 8512448

Claim:
A multi-stage scrubbing method for improving the yield of ethanol during ethanol production from corn comprising: producing a vent stream from the fermentation of corn mash during ethanol production, the vent stream consisting essentially of carbon dioxide, ethanol and volatile organic compounds; directing the vent stream into a pre-scrubber system comprising a pre-scrubber column; pre-scrubbing and cooling the vent stream with a cooled pre-scrubber fluid distributed by countercurrent flow by a fluid distributor to produce a cooled pre-scrubbed vent stream; directing the cooled pre-scrubbed vent stream from the pre-scrubber system into a main scrubber system comprising a column having a fluid flow capacity that is less than the pre-scrubber column, the main scrubber system being fluidly coupled in series to the pre-scrubber system; recirculating at least a portion of a fluid discharge stream from the pre-scrubber system back into the pre-scrubber system through the fluid distributor; scrubbing the pre-scrubbed vent stream with a main scrubber fluid; and recirculating at least a portion of a fluid discharge stream from the main scrubber system into the pre-scrubber system through the fluid distributor, wherein said multi-stage scrubbing method improves the yield of ethanol from the ethanol production process by about 1.5%.