Gas Injection Mixing for Dry Methanisation Fermenters
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Solution Overview
Problem
Current anaerobic digestion methods for continuous methanation of thick materials with high dry matter content face challenges in effective mixing, leading to sedimentation, dead zones, and inefficient fermentation due to mechanical or gas-based agitation limitations, which result in variable residence times and incomplete degradation.
Innovation Solution
A continuous dry methanation process utilizing a compartmentalized fermenter with sectoral gas injection through multiple chimneys, where gas flow and pressure are adjusted based on viscosity measurements to ensure thorough mixing and homogenization across the fermenter, maintaining favorable pH and temperature conditions for hydrolysis and methanogenesis in separate compartments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical agitation methods (moving blades, worm screw, moving cylinder) are used to mix thick fermenting material, then mixing action is provided, but the methods cannot tolerate backflow of material, create preferential flow paths, and are not suitable for mixing thick materials throughout the volume
Solution Approach 1:
The patent replaces mechanical agitation systems (blades, screws, cylinders) with a gas injection system that uses pressurized gas to create mixing action through bubble formation and rise, eliminating mechanical contact with the thick material while achieving effective mixing throughout the fermenter volume
Solution Approach 2:
The invention uses pressurized gas injection through pipes and injectors to create mixing action in the thick fermenting material. The gas forms bubbles that rise through the material, creating turbulence and mixing without requiring mechanical components that could be clogged by material backflow
2Ease of operation
If gas injection from bottom of tank is used for mixing, then gas flow is provided, but the narrow injector tip creates limited impact on mixing thick materials and cannot resuspend heavy elements at the bottom
Solution Approach 1:
The patent transitions from single-point bottom injection to multi-point injection along the tank length, and from narrow tips to expanded injection openings. This dimensional expansion allows gas to be injected at multiple locations and with greater dispersion, significantly improving mixing efficiency and the ability to resuspend heavy material throughout the fermenter volume
Solution Approach 2:
The gas injection system is divided into multiple injectors distributed along the length of the fermenter, each with multiple injection openings. This segmentation allows the gas flow to be distributed throughout the volume, creating multiple mixing zones and improving overall mixing efficiency compared to a single injection point
3Ease of operation
If significant dilution is used to promote flow and control fermentation phases, then flow is improved, but dry matter concentration decreases and bacterial support becomes insufficient
Solution Approach 1:
The patent replaces dilution-based flow control with gas injection-driven mixing and flow. The pressurized gas creates turbulence and mixing action that promotes material movement and fermentation phase control without adding liquid diluent, thereby maintaining high dry matter concentration and sufficient bacterial support
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 ensures thorough mixing and degradation of thick materials, reducing residence times, minimizing sedimentation, and optimizing fermentation efficiency by creating favorable biochemical environments for bacterial activity, resulting in improved biogas production and reduced residual liquid effluents.
Implementation Method 1
injecting, via at least one chimney which descends through at least one said compartment, pressurized gas near the bottom of the compartment, so as to create, by the rise of the injected gas through the thick material, an upward movement in the thick material around the chimney
Implementation Method 2
create, by the rise of the injected gas through the thick material, an upward movement in the thick material around the chimney
Implementation Method 3
sectoral mixing, at a high, adjustable gas flow rate
Data Source
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AI summary
The device for continuous dry methanisation, in a fermenter comprising a closed tank, comprises: - a means (110) for fermenting thick material comprising at least 17 % dry matter, in at least one compartment of said tank, and - a means (108) for injecting, via at least one chimney that descends through at least one of the compartments, pressurised gas close to the bottom of the compartment, configured to create, by the rising of the injected gas through the thick material, a convective movement in the thick material around the chimney, stirring the material, in particular that which is found at the bottom of the compartment. In embodiments, the tank comprises a first compartment into which the thick material is introduced and a second compartment into which the hydrolysed thick material flows after hydrolysis and acidogenesis in the first compartment, methanogenesis taking place in the second compartment.