Tight Ultrafiltration for Syngas Bioconversion Nutrient Recovery
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Solution Overview
Problem
Commercial-scale anaerobic bioconversion of syngas to oxygenated hydrocarbonaceous compounds faces challenges in nutrient and micronutrient loss, as well as inefficiencies due to the diversion of syngas to non-target compounds like carboxylate anions, which can be toxic to microorganisms, leading to reduced bioconversion efficiency and increased operational costs.
Innovation Solution
Implementing a continuous process that recycles nutrients and micronutrients through tight ultrafiltration, using membranes with a cut-off range of 750 to 8000 Daltons to recover at least 75% of water from the aqueous distillation fraction, thereby reducing the fresh nutrient supply and enhancing syngas conversion efficiency to alkanols, while maintaining safe concentrations for microorganisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If broth is withdrawn at a rate sufficient to maintain alkanol concentrations below toxic levels, then microorganism safety is improved, but nutrient and micronutrient loss increases
Solution Approach 1:
The patent applies the discarding and recovering principle by withdrawing broth that would otherwise be discarded and recovering nutrients and micronutrients through ultrafiltration. The ultrafiltration membrane separates nutrients from the withdrawn broth, allowing their recovery and return to the bioreactor, thus preventing loss while maintaining microorganism safety through controlled withdrawal rates.
Solution Approach 2:
The patent implements feedback by continuously monitoring and adjusting the broth withdrawal rate to maintain alkanol concentrations below toxic levels while recovering nutrients. The system uses feedback control to balance microorganism safety requirements with nutrient conservation, adjusting operational parameters based on real-time conditions.
2Adaptability or versatility
If carboxylate anions are produced as metabolic byproducts, then metabolic pathway flexibility is improved, but bioconversion efficiency deteriorates due to toxicity and diversion from target compounds
Solution Approach 1:
The patent converts the harmful effect of carboxylate anion toxicity into a benefit by using ultrafiltration to selectively remove carboxylate anions from the broth while retaining nutrients and microorganisms. This separates the harmful metabolic byproduct from the beneficial components, allowing continued metabolic flexibility while eliminating the toxic effects that reduce bioconversion efficiency.
Solution Approach 2:
The patent applies the extraction principle by using ultrafiltration to selectively extract carboxylate anions from the fermentation broth. The ultrafiltration membrane separates carboxylate anions based on their molecular size, removing them from the system while retaining larger molecules like nutrients and microbial cells, thus eliminating toxicity without affecting metabolic pathway flexibility.
3Loss of substance
If tight ultrafiltration is used to recover water and nutrients, then nutrient loss is reduced, but process complexity increases
Solution Approach 1:
The patent uses porous ultrafiltration membranes with specific pore sizes to achieve selective separation. These porous materials allow small molecules like water and carboxylate anions to pass through while retaining larger molecules such as nutrients and microbial cells. This single membrane-based approach simplifies the overall process compared to multiple separation stages while effectively reducing nutrient loss.
Solution Approach 2:
The ultrafiltration membrane performs multiple functions simultaneously: it recovers water for recycle, concentrates nutrients for return to the bioreactor, and removes toxic carboxylate anions. This multi-functionality reduces the need for separate unit operations, thereby reducing overall process complexity while achieving comprehensive broth management.
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 approach significantly reduces nutrient and micronutrient loss, enhances bioconversion efficiency, and minimizes adverse effects on microorganisms by recycling water and carboxylate anions, thereby improving the economic viability of commercial-scale syngas fermentation processes.
Implementation Method 1
subjecting at least a portion of the aqueous distillation fraction to ultrafiltration to permeate at least about 75 percent of the water contained in said remaining portion, said ultrafiltration using an ultrafiltration membrane having a cut-off in the range of between about 750 and 8000 Daltons
Implementation Method 2
Anaerobic fermentations of hydrogen and carbon monoxide involve the contact of a gaseous substrate-containing feed with an aqueous fermentation broth containing microorganisms capable of generating oxygenated hydrocarbonaceous compounds
Data Source
AI summary
Continuous processes for the anaerobic bioconversion of syngas to oxygenated hydrocarbonaceous products, in particular lower alkanols, are disclosed in which nutrients, including micronutrients, and lower carboxylate anion are recovered from at least a portion of an aqueous distillation fraction from a distillation unit operation to recover lower alkanols by using a “tight” ultrafiltration membrane. At least about 75 percent of the water permeates the ultrafiltration membrane. The tight ultrafiltration membrane rejects sufficient components that are adverse to the microorganisms used in the bioconversion that continuous fermentation operations over long durations can be achieved.