Methane Fermentation Bioreactor Heat Removal via CO2 Stripping
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Solution Overview
Problem
Current bioprocesses for producing polyhydroxyalkanoates (PHA) from methane-containing gases face challenges due to low methanotroph densities and high heat generation, resulting in low productivity and high costs, making PHA more expensive than conventional polymers.
Innovation Solution
The process involves achieving high methanotroph densities by optimizing methane and oxygen mass transfer rates and integrating heat removal through carbon dioxide stripping and evaporation, allowing for higher productivity while maintaining suitable temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high density of methanotrophs is achieved per unit of bioreactor volume, then PHA productivity per unit volume is improved, but heat generation increases making temperature control difficult
Solution Approach 1:
The patent extracts heat from the bioreactor system by removing carbon dioxide through stripping and utilizing evaporation of water. This separates the heat removal function from the biological conversion process, allowing high cell densities to be maintained without excessive heat accumulation that would otherwise limit productivity.
Solution Approach 2:
The patent changes the physical state and composition parameters of the aqueous medium by continuously stripping carbon dioxide and controlling water evaporation. These parameter changes enable the system to dissipate heat effectively while maintaining optimal conditions for high methanotroph density and PHA production.
2Quantity of substance
If high mass transfer rates of methane are achieved, then methanotroph density is improved, but heat generation and carbon dioxide production increase
Solution Approach 1:
The patent converts the harmful effects of carbon dioxide accumulation and heat generation into beneficial processes. Carbon dioxide stripping is used to remove excess CO2 while simultaneously removing heat through the evaporation of water. The system transforms what would be waste products into mechanisms for thermal management and mass transfer optimization.
Solution Approach 2:
The patent introduces carbon dioxide stripping as an intermediary process between methane consumption and PHA production. This intermediary step manages the byproducts (CO2 and heat) generated by high methanotroph activity, allowing the system to maintain high cell densities without being limited by harmful accumulations.
3Productivity
If carbon dioxide is removed from aqueous medium through stripping, then mass transfer rates of methane and oxygen are improved, but energy consumption increases
Solution Approach 1:
The patent merges the carbon dioxide removal function with the heat removal function into a single integrated process. By stripping CO2 and utilizing evaporation simultaneously, the system achieves both mass transfer improvement and thermal management in one operation, rather than requiring separate energy-intensive cooling and gas stripping systems.
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 enables higher PHA productivity per unit volume of bioreactor with reduced cooling costs, making the production of PHA more economically viable and competitive with conventional polymers.
Implementation Method 1
The fermentation of methane by methanotrophs is well known
Implementation Method 2
Since water is also formed during the metabolic oxidation of methane to carbon dioxide
Implementation Method 3
during the contact with the stripping gas, the evaporation of carbon dioxide and water from the withdrawn aqueous medium results in cooling the aqueous medium
Implementation Method 4
the evaporation of carbon dioxide and water from the withdrawn aqueous medium results in cooling the aqueous medium
Implementation Method 5
a portion of aqueous medium containing carbon dioxide generated by the methanotrophs is withdrawn from the reaction zone and contacted with a stripping gas to remove dissolved carbon dioxide from the withdrawn aqueous medium
Implementation Method 6
These high mass transfer rates support high methanotroph densities
Data Source
Figure 1
AI summary
Processes are provided for enhancing the productivity of fermenters during the metabolic conversion of methane-containing gases to products containing polyhydroxyalkanoate, which products can be used to make, for instance, animal feed or biodegradable, polymeric articles. The processes involve one or both of attenuating the heat generated to grow a population of microorganisms and removal of heat during the fermentation by removal of carbon dioxide.