Digester Internal Wall Expansions for H2S Elimination
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Solution Overview
Problem
Current methods for in situ air/enriched air/O2 injection in biogas digesters are not optimized for hydrogen sulfide (H2S) elimination, leading to insufficient reaction surfaces and the need for additional activated carbon beds for complete H2S removal.
Innovation Solution
An installation with a digester or post-digester enclosure featuring expansions and hollows on the internal wall of the gas headspace, increasing the surface area for reactions between O2 and H2S, facilitating the action of sulfo-oxidizing bacteria and enhancing H2S elimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air/enriched air/O2 is injected into the gas overhead of the digester for H2S elimination, then H2S removal is achieved, but the reaction surface area is insufficient requiring additional activated carbon beds
Solution Approach 1:
The invention transforms the flat internal wall surface into a three-dimensional structure with expansions and hollows, converting a two-dimensional reaction surface into a multi-dimensional one. This increases the available surface area for sulfo-oxidizing bacteria to act on H2S without increasing the digester volume, effectively adding another dimension to the reaction interface.
Solution Approach 2:
The internal wall is designed with hollows and expansions that create a porous-like structure, increasing the surface area available for bacterial attachment and reaction. This porous structure allows better contact between the oxidation gas, bacteria, and H2S, improving reaction efficiency without requiring additional purification materials.
2Reliability
If activated carbon beds are used for complete H2S removal, then H2S elimination is effective, but device complexity and cost increase
Solution Approach 1:
The invention extracts the H2S elimination function from the external purification system (activated carbon beds) and integrates it into the digester structure itself. By creating reaction-promoting structures on the internal wall, the digester performs partial H2S removal internally, reducing or eliminating the need for separate activated carbon purification systems.
Solution Approach 2:
The digester becomes self-sufficient for H2S elimination by incorporating reaction-promoting structures on its internal wall. The system uses its own structure (internal wall with expansions and hollows) to facilitate the oxidation of H2S, reducing dependence on external purification equipment and simplifying the overall system.
3Reliability
If high dose of O2 is injected for H2S removal, then H2S elimination improves, but the medium becomes acidified
Solution Approach 1:
The invention creates localized reaction zones on the internal wall with expansions and hollows where H2S oxidation occurs. This concentrates the oxidation reaction in specific areas rather than throughout the entire digester volume, allowing controlled H2S removal while minimizing overall acidification of the medium. The reaction occurs locally at the wall surface rather than globally in the bulk liquid.
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
The increased surface area promotes more effective hydrogen sulfide removal, reducing the need for additional purification steps and lowering costs by achieving biogas with hydrogen sulfide levels below 200 ppm.
Implementation Method 1
solid sulfur is formed from H2S and O2 (eq. (1)), produced by sulfo-oxidizing bacteria e.g. Thiobacillus
Implementation Method 2
produced by sulfo-oxidizing bacteria e.g. Thiobacillus
Implementation Method 3
the portion of the internal wall of the enclosure situated at the level of the gas headspace has expansions and/or hollows
Implementation Method 4
the reduction of H2S is also done in part by injecting air/enriched air/O2 into the gas overhead of the digester
Data Source
Figure 1
AI summary
Installation for the production of at least partially desulfurized biogas comprising a digester and/or post-digester of biomass, the digester and/or post-digester comprising: - A chamber comprising the biomass and the gaseous headspace, and - A means for introducing an oxidation gas, characterized in that the portion of the internal wall of the chamber located at the level of the gaseous headspace has expansions and/or hollows.