Process for reducing CO2 emissions and increasing alcohol productivity in syngas fermentation
View Patent ↗A process is provided that is effective for reducing CO 2 emissions, enhancing STY and/or increasing cell density. The process allows for utilization of syngas from different sources by controlling concentration levels of CO, CO 2 and H 2 in syngas provided to the fermentation and by controlling relative concentrations of CO, CO 2 and H 2 in the syngas provided to the fermentation. The process includes providing syngas to a first fermentation zone and fermenting the syngas. If the first fermentation zone off-gas includes about 4 mole % or more CO, then at least a portion of the first fermentor off-gas is provided to one or more subsequent fermentation zones.
1. A process of treating off-gas from a CO fermentation, the process comprising:
providing syngas to a first fermentor;
fermenting the syngas with a bacteria selected from the group consisting of Clostridium ljungdahlii PETC (ATCC 49587), Clostridium ljungdahlii ERI2 (ATCC 55380), Clostridium ljungdahlii C-01 (ATCC 55988), Clostridium ljungdahlii O-52 (ATCC 55889), and mixtures thereof;
generating a first fermentor off-gas; and
providing at least a portion of the first fermentor off-gas to one or more subsequent fermenters, wherein the first fermentor off-gas provided to the one or more subsequent fermenters has 4 mole % or more CO, and 10 mole % or less CO 2 ,
wherein the first fermentor off-gas is blended with an H 2 containing gas in an amount to provide a ratio of H 2 to CO molar ratio of 1.0 or more prior to being supplied to one or more subsequent fermenters,
wherein the process provides an STY of 1.0 gram or more total alcohol/(L·day) and reduces CO 2 emissions 10% or more.
2. The process of claim 1 wherein the first fermentor off-gas is provided to the subsequent fermentors operating in parallel.
3. The process of claim 1 wherein the first fermentor off-gas is provided to the subsequent fermentors operating in series.
4. The process of claim 1 wherein the first and subsequent fermentors are different fermentation zones in a fermentor.
5. The process of claim 1 wherein off-gas from a first fermentor or any subsequent fermentor is supplied to a vent-gas boiler.
6. The process of claim 1 wherein the first fermentor off-gas is blended with a CO-containing gas to provide a gas having 4 mole % or more CO prior to being supplied to the one or more subsequent fermentors.
7. The process of claim 1 wherein the first fermentor off-gas is blended with a CO containing gas in an amount effective for providing, a ratio of H 2 to CO molar ratio of 1.0 or more prior to being supplied to one or more subsequent fermentors.
8. The process of claim 1 wherein the first fermentor is effective for providing an STY of 1.0 gram or more total alcohol/(L·day).