Two-Step Amine Absorption for Biogas Upgrading
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Solution Overview
Problem
Current biogas upgrading processes face challenges in optimizing operational and capital costs while achieving low carbon dioxide and hydrogen sulphide levels, often resulting in significant energy consumption and methane loss due to non-selective absorption and inefficient regeneration methods.
Innovation Solution
A biogas upgrading method involving two absorption steps with differing pressures, where the biogas stream is first absorbed at a lower pressure to remove a significant portion of carbon dioxide and hydrogen sulphide, followed by a second absorption step at higher pressure to further purify the gas, with the regenerated liquid streams being reused to reduce energy consumption and increase absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical absorption agents are used to remove carbon dioxide and hydrogen sulphide, then the gas purity is improved, but the energy consumption for regeneration increases
Solution Approach 1:
The absorption process is divided into two distinct steps: a first absorption step using a first absorption agent, and a second absorption step using a second absorption agent. This segmentation allows each step to be optimized independently, with the first step handling bulk removal and the second step providing polish purification, thereby reducing the total energy required for regeneration compared to a single high-performance absorption system.
Solution Approach 2:
The invention changes the parameters of the absorption process by using different absorption agents with different characteristics in different steps. The first absorption agent is optimized for bulk CO2 and H2S removal, while the second absorption agent is optimized for achieving low emission levels. This parameter change allows the system to achieve high gas purity with reduced regeneration energy consumption.
2Manufacturing precision
If the liquid to gas ratio in the absorber is increased to lower carbon dioxide and hydrogen sulphide content, then the gas purity is improved, but the operational costs increase
Solution Approach 1:
The absorption process is segmented into two steps with different liquid to gas ratios. The first absorption step uses a higher liquid to gas ratio to efficiently remove the bulk of CO2 and H2S, while the second absorption step uses a lower liquid to gas ratio to achieve final purification. This segmentation optimizes operational costs by avoiding the high costs associated with maintaining excessively high liquid to gas ratios throughout the entire process.
Solution Approach 2:
The first absorption step applies excessive action by using a high liquid to gas ratio to remove the majority of contaminants, achieving more than enough purification for the final product. The second step then applies only the necessary minimal action to achieve the final emission levels. This partial/excessive action approach reduces operational costs by avoiding the continuous high-cost operation of maintaining excessively high liquid to gas ratios.
3Manufacturing precision
If the degree of regeneration of the amine solution is increased to achieve lower carbon dioxide and hydrogen sulphide limits, then the gas purity is improved, but the utility demand increases
Solution Approach 1:
The regeneration process is segmented into two corresponding absorption steps. Each absorption step has an associated regeneration step that is optimized for its specific requirements. The first regeneration step handles the bulk regeneration with lower energy demand, while the second regeneration step provides targeted regeneration with minimal energy consumption. This segmentation reduces the total utility demand compared to a single high-degree regeneration system.
Solution Approach 2:
The invention changes the parameters of the regeneration process by using different regeneration conditions for different absorption agents. The first absorption agent is regenerated under conditions optimized for its specific performance characteristics, while the second absorption agent is regenerated under conditions optimized for achieving low emission levels with minimal energy consumption. This parameter change allows the system to meet gas purity limits with reduced overall utility demand.
4Device complexity
If a single absorption step is used to remove carbon dioxide and hydrogen sulphide, then the process simplicity is maintained, but the methane loss increases
Solution Approach 1:
The absorption process is segmented into two steps with different absorption agents. The first absorption step uses an agent optimized for bulk CO2 and H2S removal with minimal methane absorption, while the second absorption step uses an agent optimized for achieving low emission levels. This segmentation reduces methane loss by avoiding the excessive methane absorption that would occur in a single step designed for high purification, while maintaining reasonable process complexity through the two-step structure.
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 method enhances energy efficiency and reduces operational costs by achieving high purity biogas with similar or reduced energy consumption, while minimizing methane loss and optimizing the circulation rate of absorption liquids.
Implementation Method 1
absorbing carbon dioxide, and hydrogen sulphide if present, from the biogas stream into the first liquid absorption stream
Implementation Method 2
increasing the pressure of the first gas effluent, to obtain a pressurized biogas stream
Implementation Method 3
regenerating the first liquid effluent and the second liquid effluent in a regeneration system, thereby obtaining a regenerated absorption stream
Data Source
AI summary
The present invention relates to a method for upgrading biogas, i.e. a method for removing carbon dioxide and/or hydrogen sulphide from biogas. Particularly the invention relates to a method for upgrading biogas by absorption in two absorbers, where the gas effluent of the first absorber is pressurized and fed to the absorber of the second absorption step and wherein the liquid effluents of the two absorbers are regenerated to form a regenerated absorption stream, which is then provided in two absorption streams which is fed to the absorber of the first and second absorption steps respectively. It also relates to a system for performing the method.