Methods and apparatus for recycling tail gas in syngas fermentation to ethanol
Inventors
Winter, John D. • Hohman, Jerrod
Assignees
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Publication Number
US-12239939-B2
Publication Date
2025-03-04
Expiration Date
Abstract
The invention present provides a method (and suitable apparatus) to convert biomass to ethanol, comprising gasifying the biomass to produce raw syngas; feeding the raw syngas to an acid-gas removal unit to remove at least some CO2 and produce a conditioned syngas stream; feeding the conditioned syngas stream to a fermentor to biologically convert the syngas to ethanol; capturing a tail gas from an exit of the fermentor, wherein the tail gas comprises at least CO2 and unconverted CO or H2; and recycling a first portion of the tail gas to the fermentor and/or a second portion of the tail gas to the acid-gas removal unit. This invention allows for increased syngas conversion to ethanol, improved process efficiency, and better overall biorefinery economics for conversion of biomass to ethanol.
Core Innovation
The invention relates to a method of converting a carbonaceous feedstock to a syngas-fermentation product by integrating syngas production, cleanup, CO2 removal, and biological conversion. The carbonaceous feedstock and an oxidant are passed to a gasifier to produce a raw syngas stream comprising CO, H2, and CO2, and the raw syngas stream is passed to a syngas cleanup unit to produce a first treated syngas stream. The cleanup unit is selected from a cyclone, a centrifuge, a filter, a membrane, and a solvent-based system.
At least a portion of the first treated syngas stream is fed to an acid-gas removal unit selected from a solvent removal unit or a pressure-swing adsorption (PSA) removal unit. This removes at least some of the CO2 to produce a conditioned syngas stream, and at least a portion of the conditioned syngas stream is fed to a fermentor under suitable fermentation conditions in the presence of suitable microorganisms and nutrients. The microorganisms biologically convert one or more of CO, H2, or CO2 to a fermentation product, while generating a tail gas stream comprising at least CO2 and unconverted CO and/or H2.
The core integration recycles fermentation tail gas by recycling at least a first portion of the tail gas to the fermentor, at least a second portion of the tail gas to the acid-gas removal unit, or both. This establishes a closed integration between biological conversion and CO2 removal, and the described systems include corresponding gasifier, syngas cleanup unit, acid-gas removal unit, fermentor, tail gas conduits, and recycle conduits.
Claims Coverage
The independent claim set includes one independent method claim. It contains the core inventive combination of gasification to a CO/H2/CO2 raw syngas, selected cleanup, selected acid-gas removal to condition the syngas, biological conversion in a fermentor to a fermentation product with a CO2-containing tail gas, and recycling split portions of the tail gas to the fermentor and/or to the acid-gas removal unit.
Recycling split portions of fermentor tail gas to fermentor and acid-gas removal unit
recycling at least a first portion of the tail gas to the fermentor, at least a second portion of the tail gas to the acid-gas removal unit, or both.
Gasification and syngas cleanup producing treated syngas from CO/H2/CO2 raw syngas
passing the carbonaceous feedstock and an oxidant to a gasifier to gasify the feedstock and produce a raw syngas stream comprising CO, H2, and CO2, and passing the raw syngas stream to a syngas cleanup unit to produce a first treated syngas stream, wherein the cleanup unit is selected from a cyclone, a centrifuge, a filter, a membrane, and a solvent-based system.
Acid-gas removal conditioning via solvent removal unit or PSA removal unit
feeding at least a portion of said first treated syngas stream to an acid-gas removal unit selected from a solvent removal unit or a pressure-swing adsorption (PSA) removal unit, to remove at least some of said CO2 and produce a conditioned syngas stream.
Biological conversion in fermentor generating tail gas with CO2 and unconverted CO and/or H2
feeding at least a portion of said conditioned syngas stream to a fermentor, under suitable fermentation conditions and in the presence of suitable microorganisms and nutrients to biologically convert one or more of CO, H2, or CO2 to a fermentation product and generate a product stream comprising at least the fermentation product and a tail gas stream comprising at least CO2 and unconverted CO and/or H2.
Overall, the claims cover an integrated syngas-fermentation process in which a CO/H2/CO2 raw syngas is produced by gasification, cleaned by a selected syngas cleanup unit, conditioned by selected acid-gas removal to reduce CO2, and then converted biologically in a fermentor. The fermentation tail gas is split and recycled either to the fermentor and/or to the acid-gas removal unit.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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