Fermentation Effluent Recycling in Gasification
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Solution Overview
Problem
Current processes for gasification and gas fermentation face inefficiencies due to the handling of effluents such as biogas and sulfur compounds, which require extensive clean-up and result in solid waste and high energy costs, necessitating an integrated system for effective waste management and energy recovery.
Innovation Solution
The integration of gas fermentation and wastewater treatment processes with gasification, where effluents like biogas, microbial biomass, and clarified water are recycled to enhance the syngas stream's H2:CO ratio and reduce waste, using C1-fixing microorganisms like Clostridium autoethanogenum to produce ethanol and other products, and utilizing these effluents to quench or heat the syngas stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extensive gas clean-up technology is used to remove sulfur from syngas before Fischer-Tropsch process, then catalyst deactivation is prevented, but process complexity and cost increase significantly
Solution Approach 1:
The patent combines the wastewater treatment process with the gasification and fermentation processes by integrating the biogas produced from anaerobic digestion back into the system. The biogas is used as an additional feedstock for gasification or as a heating source, merging waste treatment with resource generation and eliminating the need for separate extensive clean-up systems.
Solution Approach 2:
The system uses its own byproducts to serve its needs. The biogas produced from wastewater treatment is utilized within the same system for energy generation or as feedstock, creating a self-sufficient loop that reduces external dependencies and simplifies the overall process configuration.
2Use of energy by moving object
If biogas is combusted in a biogas engine for electricity and heat production, then energy recovery is achieved, but water vapor and sulfur compounds must be removed first to avoid combustion challenges and engine damage
Solution Approach 1:
Instead of removing water vapor and sulfur compounds from biogas before combustion, the patent directs the biogas to a gasification process where these components are converted into useful syngas components. The water vapor and sulfur compounds that would be harmful in combustion are transformed into valuable chemical feedstocks, converting a liability into an asset.
Solution Approach 2:
Rather than cleaning the biogas before using it in a conventional biogas engine, the patent inverts the approach by using gasification to convert the biogas components into syngas, which is then used for fermentation. This reverses the traditional sequence of cleaning then combusting, achieving energy recovery while eliminating the need for complex removal processes.
3Reliability
If wastewater treatment process includes multiple separate treatment steps for product removal, anaerobic digestion, and biological oxidation, then various components are removed and clarified water is produced, but considerable solid waste is generated
Solution Approach 1:
The gasification unit serves multiple functions: it processes solid waste from wastewater treatment to generate syngas, provides heating for the fermentation process, and converts refractory organic compounds into usable chemical feedstocks. This multi-functionality eliminates the need for separate treatment steps and converts waste into valuable resources.
Solution Approach 2:
Instead of discarding solid waste from wastewater treatment, the patent recovers it by feeding it to the gasification process. The solid waste is converted into syngas, which is then used as feedstock for fermentation, transforming a waste stream into a valuable resource and eliminating disposal costs.
4Productivity
If gasification process converts organic materials into syngas, then waste is reduced and useful product is produced, but extensive clean-up is required to make syngas suitable for subsequent processes
Solution Approach 1:
The system creates a feedback loop where the output of one process becomes the input of another. The syngas from gasification is directly fed to the fermentation process, and the fermentation broth is treated by anaerobic digestion to produce biogas, which is then fed back to gasification. This closed-loop feedback system eliminates the need for extensive intermediate clean-up processes.
Solution Approach 2:
The fermentation process acts as an intermediary that tolerates and processes syngas with varying compositions that would be unsuitable for Fischer-Tropsch. The microorganisms in fermentation can handle a broader range of syngas compositions, serving as a mediator that bridges the gasification process and final product generation without requiring extensive clean-up infrastructure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This integration increases the efficiency of alcohol production, reduces water consumption, decreases waste treatment volumes, and enhances revenue generation by converting biomass into syngas, achieving a higher energy recovery and reduced land requirements for wastewater treatment.
Implementation Method 1
Gas fermentation provides for the biological fixation of gases, including syngas, into one or more product
Implementation Method 2
Gasification is a process that converts organic or fossil fuel-based carbonaceous materials into syngas comprising carbon monoxide, carbon dioxide, and hydrogen
Implementation Method 3
The syngas stream is cooled to a temperature suitable for the fermentation process
Data Source
AI summary
The description describes the integration of a gas fermentation process with a gasification process whereby effluent from the gas fermentation process is recycled to the gasification process. The one or more effluents which can be recycled include a stream comprising microbial biomass, a product stream comprising at least a portion of the at least one fermentation product, a by-product stream comprising fusel oil, and a waste water stream comprising microbial biomass. The stream comprising biomass can be dried before it is passed to the gasification zone. At least a portion of the waste water stream can be passed to the gasification process where one use is to replace at least a portion of the process water. The waste water stream can be further processed to produce a clarified water stream and a biogas stream comprising methane either or both of which can be passed to the gasification process.