Treatment of air pollutants emitted from corn-derived ethanol production facilities

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Bangs, Katherine Marie

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Ethanol is widely seen as an environmentally friendly gasoline oxygenate that is renewable and sustainable. As a result, the total annual capacity of ethanol production facilities in the United States is rising rapidly. However, ethanol has environmental issues that may limit its use as a gasoline additive or alternative fuel. The United States Environmental Protection Agency (USEPA) has recently investigated ethanol production facilities for emissions of air pollutants and found that these facilities can be significant sources of volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and odors. The distillers dried grains with solubles (DDGS) dryer stack at ethanol production facilities is the most significant source of VOCs and HAPs at most of these sites. The objective of the project was to investigate the feasibility of utilizing a scrubber/vapor phase bioreactor configuration to treat the VOCs and HAPs released from the DDGS dryer stack during corn-derived ethanol production. Acetic acid was chosen as the representative acid gas and acetaldehyde was chosen as the representative HAP based on reports from the EPA. The research showed that when a caustic solution was used, the scrubber was efficient at removing acetic acid at pH levels above approximately 6.5. In this operating regime the rate of removal was controlled by gas phase mass transfer resistance. In contrast to acetic acid, acetaldehyde passed through the water scrubber rapidly. However, a vapor phase bioreactor was found to be very efficient at removing acetaldehyde, and could be placed downstream of the scrubber. Thus, a hybrid caustic scrubber/vapor phase bioreactor configuration has potential for the treatment of air pollutants from the DDGS dryer stack at ethanol production facilities


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