Tail gas of gas fermentation to dry gasification feedstock

Inventors

Gao, Allan Haiming • Conrado, Robert John

Assignees

Lanzatech Inc

Abstract

The disclosure provides for the integration of a gas fermentation process with a gasification process whereby tail gas from the gas fermentation process is recycled to a dryer of the gasification process. The tail gas from the gas fermentation process is utilized to generate heat which in turn is used to dry feedstock to the gasification process. The heat is typically used to heat a drying gas, such as air, which is then directly or indirectly contacted with the gasification feedstock to dry the gasification feedstock. Dried gasification feedstock provides improved yield and improved quality of syngas as compared to gasification feedstock that is not dried.

Core Innovation

The invention integrates gas fermentation with gasification by using fermentation tail gas to supply heat for drying a gasification feedstock. A method heats a drying gas, directly contacts the heated drying gas with the gasification feedstock in a dryer to generate a dried gasification feedstock, and then passes the dried gasification feedstock to a gasification process to gasify it into syngas. A portion of the syngas is then fermented in a bioreactor using a microorganism to generate tail gas and a fermentation broth comprising at least one product and microbial biomass comprising the microorganism.

The fermentation broth is sent to a product recovery process to produce a microbial biomass depleted water stream, a crude ethanol stream, a fusel oil stream, and a product stream, with the microbial biomass comprising the microorganism separated from the fermentation broth. At least a portion of the microbial biomass comprising the microorganism is dried and then passed to the gasification process to gasify the dried microbial biomass to generate syngas. At least a portion of a stream selected from the microbial biomass depleted water stream, the crude ethanol stream, the fusel oil stream, and any mixture thereof is also passed to the gasification process.

Tail gas is utilized to provide heat for heating the drying gas, closing the integration loop between fermentation and gasification drying. In the related method, routing the microbial biomass depleted water stream to the gasification process increases the H2:CO ratio of the syngas from the gasification process to at least 2:1. The disclosed approach is aimed at improving syngas yield and quality by drying the gasification feedstock before gasification and by recycling tail-gas heat to the drying step.

Claims Coverage

The independent claims define an integrated method with recurring inventive features: direct drying of a gasification feedstock using heated drying gas, gasifying the dried feedstock to produce syngas for fermentation, recovering products and separating microbial biomass, drying and gasifying the microbial biomass, routing recovery streams to gasification, and using fermentation tail gas to heat the drying gas. Additional claim coverage requires increasing the syngas H2:CO ratio to at least 2:1 and/or recovering at least 92% of energy in the tail gas.

Across the independent claims, the method centers on directly drying a gasification feedstock using heated drying gas, gasifying the dried feedstock to produce syngas that is fermented to generate tail gas and a product-containing fermentation broth, then recovering products while separating microbial biomass, drying and gasifying the microbial biomass and routing recovery streams to gasification, and using fermentation tail gas as heat for the drying step. Dependent variants further require raising syngas H2:CO ratio to at least 2:1 and/or recovering at least 92% of energy in the tail gas for drying.

Stated Advantages

Documented Applications