Modular Biogas CO2 Absorption Risers for Lower-Cost Separation
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Solution Overview
Problem
Existing biogas separation systems, such as water wash processes, are cumbersome and costly due to the need for large, corrosion-resistant stainless steel vessels and substantial weight, requiring significant capital expenditures.
Innovation Solution
A biogas separation system utilizing a series of absorption risers with inlets and outlets at the top for installation below grade, allowing for flexible configurations in series, parallel, or combined connections, using chemical or biological liquid absorbents to separate carbon dioxide from methane, with optional recirculation and regeneration of the absorbent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water wash process is used with elevated pressure and reduced temperature, then carbon dioxide solubility in water is enhanced, but substantial vessel height and weight are required
Solution Approach 1:
The patent divides the single large water wash vessel into multiple smaller vessels arranged in series. Each vessel provides a portion of the total contact time and absorption capacity, eliminating the need for one extremely tall and heavy vessel while achieving the same carbon dioxide removal efficiency.
Solution Approach 2:
Instead of increasing vessel height vertically, the patent distributes the absorption function across multiple vessels arranged horizontally or in stacked configurations. This transforms the problem from a vertical dimension constraint to a horizontal or modular arrangement, reducing individual vessel weight while maintaining total treatment capacity.
2Reliability
If stainless steel vessels are used for corrosion resistance, then hydrogen sulfide and carbonic acid corrosion is prevented, but capital expenditure increases
Solution Approach 1:
By segmenting the system into multiple smaller vessels, the patent reduces the amount of expensive stainless steel required per vessel and overall. Each smaller vessel requires less corrosion-resistant material while the series arrangement maintains the same total corrosion protection capability.
Solution Approach 2:
The patent allows for the use of less expensive materials in the divided vessel system, as the reduced size and distributed configuration enables easier replacement and maintenance of individual vessels, effectively treating them as more replaceable components rather than a single permanent installation.
3Quantity of substance
If large volume of absorbent liquid is used, then carbon dioxide absorption capacity is increased, but vessel size and foundation requirements increase
Solution Approach 1:
The patent distributes the absorbent liquid volume across multiple smaller vessels rather than concentrating it in one large vessel. This segmentation maintains the total absorbent volume and associated absorption capacity while reducing the footprint and foundation requirements of each individual vessel.
Solution Approach 2:
The patent transitions from a single large-volume vessel requiring substantial foundation area to multiple smaller vessels that can be arranged in space-efficient configurations, effectively trading vertical or concentrated horizontal space for distributed space, reducing overall foundation requirements.
4Loss of time
If tall vessels are constructed for sufficient contact time, then carbon dioxide absorption is adequate, but system complexity and capital expenditure increase
Solution Approach 1:
The patent achieves the required contact time by segmenting the absorption process into multiple vessels in series, where each vessel contributes a portion of the total contact time. This modular approach simplifies individual vessel design and construction while maintaining the cumulative contact time needed for adequate carbon dioxide removal.
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 system reduces the physical footprint and material costs while enhancing flexibility and efficiency in producing purified methane and carbon dioxide streams, allowing for cost-effective and adaptable biogas separation.
Implementation Method 1
carbon dioxide and hydrogen sulfide are many times more soluble in water than methane... As the biogas rises through the water, the carbon dioxide, hydrogen sulfide, and other water-soluble trace constituents are absorbed into the water
Data Source
AI summary
A system for separating carbon dioxide from a biogas stream includes a first pipe and a second pipe extending within the first pipe. A first inlet at a first end of the second pipe receives the biogas stream, and a second inlet at a first end of the first pipe receives a liquid absorbent. The biogas stream is dispensed from the second pipe into the first pipe to mix with the liquid absorbent, separating the carbon dioxide from the biogas stream. A first outlet is in fluid communication with the first pipe to deliver a purified biogas stream. A first end of a third pipe extends from the first pipe and a second end of the third pipe extends into a mixed liquid absorbent stream within the first pipe. A second outlet, in fluid communication with the first end of the third pipe, delivers the mixed liquid absorbent stream.