Biogas Separation Device Using Vacuum Pump and Static Mixer
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Solution Overview
Problem
Current biogas separation technologies, such as water washing, are costly and inefficient for small-scale methanization units, limiting methane and carbon dioxide recovery rates and purity, especially due to high water regeneration pressure and CO2 dilution issues.
Innovation Solution
A device with a washing column, counter-current liquid-gas absorption, and a regeneration circuit including a static mixer and vacuum pump for desorption, along with a cyclone-type cylindrical separator for intermediate pressure expansion, optimizing desorption pressure and enhancing methane and carbon dioxide recovery and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water washing with high pressure is used to absorb CO2, then CO2 absorption efficiency is improved, but methane purity is limited and energy consumption increases
Solution Approach 1:
The invention divides the separation process into two distinct stages: absorption stage (CO2 removal) and desorption stage (CH4 recovery). The absorption column operates at high pressure for efficient CO2 absorption, while the desorption column operates at low pressure for high-purity methane recovery. This segmentation allows each stage to be optimized independently, resolving the contradiction between absorption efficiency and methane purity.
Solution Approach 2:
The system dynamically switches between absorption and desorption modes by controlling the operation of two separate columns. While one column is absorbing CO2, the other is desorbing methane, and vice versa. This dynamic operation allows the system to maintain high CO2 absorption efficiency while simultaneously achieving high methane purity in the recovered gas stream.
2Productivity
If stripping column is used for water regeneration, then CO2 desorption is achieved, but system complexity and investment costs increase
Solution Approach 1:
The invention merges the desorption function into the same column used for absorption, but operates it in alternating cycles. The bottom of the absorption column serves as the inlet for the desorption column, eliminating the need for a separate stripping column. This integration reduces the total number of columns from three (absorption column, stripping column, and flash tank) to two, simplifying the system while maintaining regeneration efficiency.
Solution Approach 2:
The system uses periodic action by alternating between absorption and desorption modes in two columns. Column 1 absorbs CO2 while Column 2 desorbs methane, then they switch roles. This periodic operation allows water regeneration to be achieved efficiently without requiring a continuous third column for stripping, thereby reducing system complexity.
3Ease of operation
If atmospheric pressure desorption is used, then equipment simplicity is maintained, but methane recovery rate is limited to 90%
Solution Approach 1:
The system dynamically adjusts pressure conditions by using a vacuum pump during the desorption phase to create low-pressure conditions (below atmospheric pressure). This dynamic pressure control allows the desorption column to operate at reduced pressure, significantly improving methane recovery rate from 90% to over 95%, while maintaining equipment simplicity through the use of a single vacuum pump rather than complex pressure control systems.
4Productivity
If multiple columns are used for CO2 absorption and regeneration, then separation efficiency is improved, but operational costs and energy consumption increase
Solution Approach 1:
The system performs preliminary action by pre-cooling the biogas before it enters the absorption column. This pre-cooling enhances the solubility of CO2 in the washing water, improving absorption efficiency without requiring additional high-pressure compression stages. The precooler uses the cold water from the bottom of the absorption column, creating a heat exchange that reduces energy consumption while maintaining separation efficiency.
Solution Approach 2:
The system maintains continuity of useful action by recycling the cold water from the bottom of the absorption column back to the top as washing water. This continuous circulation creates a heat exchange process that pre-cools incoming biogas and pre-heats the washing water, improving CO2 absorption efficiency while minimizing energy consumption. The alternating operation of two columns ensures continuous separation without interruption.
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 solution achieves high methane and carbon dioxide recovery rates and purity, reducing operational costs and energy consumption, making it economically and environmentally viable for small-scale agricultural biogas processing.
Implementation Method 1
separation zone comprising means for bringing into contact, by counter-current circulation, the biogas and a liquid solution capable of selectively absorbing the gaseous constituent soluble therein
Implementation Method 2
depression means positioned at the outlet of the static mixer and configured to create, at the outlet, a pressure between 0.01 and 0.8 bar allowing the desorption of the soluble gaseous constituent
Implementation Method 3
said tank comprising an outlet for evacuating the absorbent solution towards a regeneration circuit comprising a static mixer
Data Source
Figure 1
AI summary
The invention relates to a device for separating methane and carbon dioxide contained in biogas produced by methanization. The device comprises a liquid-gas absorption scrubbing column (CL) and a static mixer regeneration circuit (MS). Between the outlet of the scrubbing column (CL) and the static mixer (MS), the device includes a pressure regulator (GLCC) with a cyclone-type cylindrical separator. The gas outlet of said regulator (GLCC) is fed with the biogas into the inlet of the scrubbing column (CL). The regeneration circuit includes a separation tank at the outlet of the static mixer. The regeneration circuit is characterized in that said regeneration circuit further comprises a vacuum pump (PV) for removing the CO2 separated from the regenerated liquid into a separation tank (CS) at the outlet of the static mixer (MS).