Methane-Rich Gas Purification Using Staged Cooling and CO2 Condensation
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Solution Overview
Problem
Current methods for purifying methane-rich biogas, such as landfill gas and digester gas, are inadequate in removing contaminants like moisture, H2S, SO2, halogens, and siloxanes, leading to inefficient energy use and increased maintenance costs, with no effective solution for achieving natural gas quality.
Innovation Solution
A process involving two cooling steps, pressurization, and the use of a catalyst/adsorbent like SOXSIA™, which removes contaminants through condensation and adsorption, followed by reactivation and regeneration, to produce a high-quality methane stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification methods (activated carbon filters, molecular membrane filters, silica-gel) are used to remove contaminants, then some contaminants are removed, but the gas quality does not reach natural gas level and regeneration/disposal costs are high
Solution Approach 1:
The patent applies parameter changes by systematically adjusting temperature and pressure conditions through multiple cooling steps. The gas is cooled to progressively lower temperatures (-25°C, then -60°C, finally -80°C) at controlled pressure levels (1-10 bar), transforming the physical state of contaminants to enable their separation. This multi-stage parameter adjustment achieves natural gas quality (≥90% methane) while enabling cost-effective contaminant removal and recovery.
Solution Approach 2:
The patent exploits phase transitions of contaminants at different temperature and pressure conditions. By cooling the biogas through multiple stages, water condenses, CO2 transitions from gas to liquid, and siloxanes undergo phase changes that enable their separation. These phase transitions occur at specifically controlled temperatures and pressures, allowing efficient removal of contaminants while maintaining methane in the gas phase for recovery.
2Ease of operation
If single-step cooling or simple filtration is used, then the process is simple, but contaminants like moisture, H2S, SO2, halogens, and siloxanes are not sufficiently removed
Solution Approach 1:
The patent segments the purification process into three distinct cooling stages, each targeting specific contaminants at different temperature levels. The first stage removes water and heavy hydrocarbons at -25°C, the second stage removes CO2 and additional contaminants at -60°C, and the third stage achieves final purification at -80°C. This segmentation allows each stage to be optimized for specific contaminant removal while maintaining overall process simplicity and modularity.
3Manufacturing precision
If cryogenic distillation and membrane separation are used to produce fuel-grade methane, then gas quality improves, but the process complexity and equipment requirements increase
Solution Approach 1:
The patent replaces complex mechanical separation systems (cryogenic distillation columns, membrane separation units) with a simpler thermal-based approach using sequential cooling stages. Instead of relying on complex distillation mechanics or membrane transport, the method uses temperature and pressure control to induce phase transitions and enable gravitational/sedimentation-based separation. This substitution achieves comparable methane purity (≥90%) with significantly reduced equipment 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 process achieves a methane content of up to 90 mole % and removes >99% moisture, >95% siloxanes, and >98% particulates, resulting in a gas quality comparable to natural gas, reducing maintenance and energy costs while allowing for efficient energy production.
Implementation Method 1
pressurising said methane containing gas stream (A) and subsequently cooling it, whereby a stream comprising condensed contaminants (C) and a methane comprising stream (B) are obtained
Implementation Method 2
feeding said methane comprising stream (B) to an adsorption unit and/or a catalytic conversion unit, whereby the concentration of contaminants in stream (B) is further decreased
Implementation Method 3
cooling the methane comprising stream (B) to a temperature which is sufficient to condensate CO2 from said stream (B)
Data Source
AI summary
The invention is directed to processes and apparatuses for gas treatment, in particular for the purification of methane rich gas streams, such as gas obtained from the conversion from organic matter (“biogas”). In accordance with the present invention there is provided an apparatus and a process for producing a purified methane comprising gas stream (P) from a methane containing gas stream (A), comprising the steps of: (a) pressurising said methane containing gas stream (A) and subsequently cooling it, whereby a stream comprising condensed contaminants (C) and a methane comprising stream (B) are obtained; (b) optionally feeding said methane comprising stream (B) to an adsorption unit and/or a catalytic conversion unit, whereby the concentration of contaminants in stream (B) is further decreased; and (c) cooling the methane comprising stream (B) to a temperature which is sufficient to condensate CO2 from said stream (B), whereby said purified methane comprising gas stream (P) is obtained.