Anaerobic Digester Hydrogen Transfer via External Mixing
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Solution Overview
Problem
Existing methods for enhancing methane concentration in biogas, such as ex situ and in situ processes, face limitations in hydrogen transfer efficiency and require complex reactor modifications or external treatment systems, particularly at atmospheric pressure.
Innovation Solution
A method and facility that operate an anaerobic digester at self-generated pressures above atmospheric, utilizing an external liquid-gas mixing system to recirculate hydrogen-saturated organic matter and microbubbles, facilitating hydrogen transfer and transformation of CO2 into CH4 without the need for internal reactor modifications or electrolytic systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ex situ biological processes are used to transform CO2 into CH4, then methane concentration in biogas is improved, but the process requires separation from the biodigester and external treatment systems increasing device complexity
Solution Approach 1:
The patent combines the CO2 transformation process with the anaerobic digestion reactor by introducing hydrogen-injecting devices directly into the digester, merging the ex situ biological conversion with the in situ digestion process. This integration eliminates the need for separate treatment systems while maintaining high methane concentration levels.
Solution Approach 2:
Hydrogen serves as an intermediary substance that enables the transformation of CO2 into CH4 within the existing digester environment. By injecting H2 as a mediator, the system facilitates the biological conversion process without requiring complex external treatment infrastructure.
2Device complexity
If in situ processes transform CO2 into CH4 in the digester, then external treatment systems are eliminated, but hydrogen transfer efficiency deteriorates at atmospheric pressure
Solution Approach 1:
The patent changes the pressure parameter by operating the digester at elevated pressure (above atmospheric pressure). This pressure increase enhances hydrogen solubility and transfer efficiency in the liquid phase, directly addressing the productivity limitation of conventional atmospheric pressure systems.
Solution Approach 2:
The system utilizes pressurized hydrogen injection and liquid-phase mass transfer mechanisms to improve hydrogen delivery to microorganisms. By applying pneumatic pressure and optimizing hydraulic conditions, the system achieves efficient hydrogen transfer without requiring complex external treatment equipment.
3Productivity
If pressure is increased to improve hydrogen transfer, then hydrogen dissolution is improved, but the system requires pressurized operation increasing energy consumption
Solution Approach 1:
The digester utilizes the biogas production pressure to maintain the elevated pressure conditions needed for efficient hydrogen transfer. The system is self-sufficient in maintaining pressure, using the natural pressure generated by biogas accumulation rather than requiring continuous external pressurization, thereby reducing energy consumption.
Solution Approach 2:
The system optimizes the pressure parameter to the minimum level required for effective hydrogen transfer, balancing productivity improvement with energy consumption. By operating at moderately elevated pressure rather than high pressure, the system achieves enhanced hydrogen dissolution while minimizing the energy penalty.
4Device complexity
If conventional digestion is used, then the process is simple, but methane concentration remains limited and cannot produce biomethane
Solution Approach 1:
The system performs preliminary hydrogen injection into the digester before the CO2-to-CH4 conversion occurs. By pre-supplying hydrogen to the anaerobic environment, the system prepares the conditions necessary for enhanced methane production, allowing conventional digesters to produce biomethane-quality gas without major modifications.
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 efficient production of methane-enriched biogas by increasing hydrogen transfer and pressure within the digester, allowing for biomethane production without external treatment, and allows for flexible facility sizing and control of hydrogen and carbon dioxide concentrations.
Implementation Method 1
biological processes that are based on the use of hydrogenotrophic microorganisms, which are able to carry out the reaction CO2 + 4H2 → CH4 + 2H2O
Implementation Method 2
utilizing an external liquid-gas mixing system to recirculate hydrogen-saturated organic matter
Implementation Method 3
organic matter is transformed into a gaseous mixture of CH4 (methane) and CO2, which is known as biogas, by means of microorganisms
Data Source
Figure 1
AI summary
The invention relates to a method for obtaining methane-enriched biogas for an anaerobic digester (1) that operates at a self-generated pressure, which is greater than the atmospheric pressure, comprising feeding the digester (1) with organic matter for carrying out anaerobic digestion, extracting an enriched biogas stream (13) through a valve (11); and which further comprises the steps of extracting and recirculating organic matter that is being treated in the digester (1) through a recirculation pipe and a pumping device (14), introducing a recirculation stream (6) which contains organic matter in an external liquid gas mixing system (3) and injecting a hydrogen stream (2), and subsequently injecting a liquid stream of hydrogen-saturated organic matter and microbubbles in a gaseous phase into the digester (1)