Multi-Stage Adsorption System for Methane Purification
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Solution Overview
Problem
Current methods for purifying methane-bearing feed gas to meet pipeline or liquefaction standards are inefficient, costly, and complex, particularly when dealing with mixtures containing carbon dioxide, nitrogen, oxygen, and water vapor, as they require multiple units and high energy input, and struggle with achieving high purity and recovery while maintaining operational safety.
Innovation Solution
A multi-stage adsorption system employing pressure swing adsorption (PSA) and temperature swing adsorption (TSA) stages, where waste products from later stages are used to regenerate adsorbents in earlier stages, simplifying the process and improving efficiency by combining bulk separation and purification steps within the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple separate units are used for bulk separation and purification of methane-bearing feed gas, then separation purity can be achieved, but device complexity and capital cost increase significantly
Solution Approach 1:
The patent combines bulk separation and purification functions into a single integrated adsorption unit with multiple adsorbent beds arranged in series. The first bed contains adsorbent for bulk removal of CO2 and H2O, while the second bed contains adsorbent for purification to meet pipeline or LNG specifications. This merging eliminates the need for separate units for each function, reducing capital cost and system complexity while maintaining the required separation purity through the sequential action of different adsorbents.
Solution Approach 2:
The single integrated unit is segmented into multiple adsorbent beds with different adsorbent materials optimized for specific functions. The first bed uses adsorbent selective for bulk removal of particular components (CO2 and H2O), while the second bed uses adsorbent optimized for final purification. This segmentation allows each portion of the system to specialize in a specific separation task, achieving high overall purity without requiring multiple completely separate units.
2Manufacturing precision
If conventional separation methods are used to meet pipeline or LNG standards, then product purity is achieved, but energy consumption increases due to multiple units and high energy input
Solution Approach 1:
The adsorption system operates continuously with multiple beds in different phases of the adsorption-desorption cycle. While one bed is performing adsorption to remove impurities, other beds are being regenerated by desorption. This continuous operation eliminates idle time and ensures that the system is always producing purified methane at the required purity level, maintaining continuous useful action without energy-wasting interruptions or startup/shutdown cycles.
Solution Approach 2:
The system uses periodic pressure swing adsorption where beds are cyclically switched between adsorption and desorption modes. During adsorption, impurities are removed from the methane stream; during desorption, the adsorbent is regenerated by reducing pressure and purging with light product gas. This periodic action allows regeneration to occur without interrupting product production, as multiple beds are staggered in their cycles, reducing overall energy consumption compared to continuous regeneration methods.
3Use of energy by moving object
If waste products from later stages are used to regenerate adsorbents in earlier stages, then energy consumption is reduced, but process complexity increases
Solution Approach 1:
The system uses its own waste products (light product gas from later purification stages) to regenerate the adsorbents in earlier bulk separation stages. The light product gas, which would otherwise be wasted or require energy-intensive compression for disposal, is redirected to purge and regenerate the first adsorbent bed. This self-service approach converts a waste stream into a useful regeneration medium, reducing external energy requirements while the integrated control system manages the complex flow patterns.
Solution Approach 2:
Instead of discarding the light product gas from later stages, the system recovers and reuses it for adsorbent regeneration in earlier stages. The light product gas contains minimal impurities and is ideal for purging adsorbent beds during regeneration. This recovery and reuse eliminates the need to vent or flare the gas, converting a potential waste product into a valuable resource that reduces the energy required for external regeneration methods.
4Productivity
If multiple adsorption stages are implemented for high purity methane production, then methane recovery is enhanced, but system complexity and operational difficulty increase
Solution Approach 1:
The system dynamically switches the role of each adsorbent bed between adsorption and desorption modes based on a predetermined cycle sequence. The control system automatically manages the complex switching of multiple beds, opening and closing valves to direct flows according to the optimal sequence. This dynamic operation maximizes methane recovery by ensuring each bed operates at peak efficiency during its adsorption phase while maintaining continuous production, without requiring manual intervention despite the operational 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 system effectively produces a methane-rich product meeting pipeline or liquefaction standards with reduced complexity and energy consumption, enhancing methane recovery and operational safety by leveraging waste products for adsorbent regeneration, thus offering a cost-effective solution for small-scale LNG production.
Implementation Method 1
a first stage that operates by pressure swing adsorption (PSA), a second stage that operates by temperature swing adsorption (TSA), and a third stage that operates by pressure swing adsorption (PSA)
Implementation Method 2
a second stage that operates by temperature swing adsorption (TSA)
Implementation Method 3
using a portion of the waste product that is generated in the third stage, from which the methane-rich product gas also flows, to regenerate adsorbent in the second stage, and to use a portion of the waste product that is generated in the second and third stages to regenerate adsorbent in the first stage
Data Source
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Figure 3~4
Figure 5~6
AI summary
Methane product gas is produced from landfill gas and gob gas either by a three-stage process of PSA-TSA-PSA or PSA-PSA-PSA, or a two-stage process of PSA-PSA.