Biogas Purification via Membrane and PSA Integration
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Solution Overview
Problem
Current biogas purification methods face challenges in efficiently removing carbon dioxide, hydrogen sulfide, and oxygen to meet pipeline specifications, leading to high energy consumption and operational costs.
Innovation Solution
A combined membrane gas separation and pressure swing adsorption (PSA) process is integrated to remove acid gases and oxygen from biogas streams, optimizing membrane staging and PSA operation to enhance methane recovery and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional biogas purification methods (absorption, cryogenic separation, or single membrane separation) are used to remove carbon dioxide and meet pipeline specifications, then carbon dioxide removal is achieved, but energy consumption increases and operational costs rise
Solution Approach 1:
The biogas purification process is divided into multiple membrane separation stages, each targeting specific impurity removal. The first stage removes bulk carbon dioxide, while subsequent stages progressively reduce other impurities, allowing efficient separation without requiring energy-intensive single-stage processes
Solution Approach 2:
The system dynamically adjusts operating parameters including pressure ratios, flow rates, and stage configurations based on feed gas composition variations. This dynamic optimization enables the membrane system to maintain high purification efficiency while minimizing energy consumption across different operating conditions
2Manufacturing precision
If multiple impurities (carbon dioxide, hydrogen sulfide, oxygen, nitrogen) are removed to meet pipeline specifications, then biogas quality improves, but device complexity increases
Solution Approach 1:
The membrane separation system is designed to simultaneously remove multiple impurities (carbon dioxide, hydrogen sulfide, oxygen, and nitrogen) in a single integrated process. The membrane material and configuration are optimized to provide universal separation capability for all target impurities, eliminating the need for multiple separate treatment units
Solution Approach 2:
The patent combines multiple separation functions into a unified membrane system where different membrane layers or stages work together to remove various impurities. This merging of functions into a single system reduces overall device complexity compared to using separate units for each impurity removal
3Loss of energy
If high methane recovery is achieved through optimized membrane staging, then energy consumption reduces, but device complexity increases
Solution Approach 1:
The membrane system is segmented into multiple stages with each stage optimized for specific separation objectives. This segmentation allows progressive methane recovery optimization across stages, reducing the need for excessive compression and reprocessing that would increase energy consumption
Solution Approach 2:
The system incorporates feedback mechanisms where the output of each membrane stage informs the operation of subsequent stages. This feedback optimization ensures that methane recovery is maximized at each stage while avoiding unnecessary processing, thereby reducing overall energy consumption without requiring excessive system complexity
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 integrated process effectively removes multiple contaminants, achieving high methane recovery and low energy consumption, while meeting pipeline specifications for biogas quality.
Implementation Method 1
passing the first effluent stream into a first membrane separation unit, wherein a membrane removes a portion of carbon dioxide, oxygen and nitrogen from the first effluent stream
Implementation Method 2
passing the sixth effluent stream to a pressure swing adsorption separation unit containing an adsorbent selective for removal of oxygen and nitrogen from a mixture of methane and carbon dioxide
Data Source
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AI summary
A system and method for generating renewable natural gas from raw biogas streams, such as biogas from landfills or biogas from controlled anaerobic digestion of biomass, provides for the efficient removal of acid gases and other impurities, including oxygen and nitrogen from biogas. The biogas is treated in a multi-stage membrane gas separation system integrated with a pressure swing adsorption system to generate pipeline-specification renewable natural gas. The combined system provides for efficient acid gas removal while simultaneously limiting oxygen carryover into the product stream.