8-ring Zeolite Gas Separation for Methane Recovery
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Solution Overview
Problem
Conventional gas separation techniques, such as pressure swing adsorption (PSA) and temperature swing adsorption (TSA), are inefficient in removing CO2, N2, and H2S from natural gas, especially at high pressures, resulting in low recovery of methane and high operational costs.
Innovation Solution
The use of 8-ring zeolites with a Si:Al ratio of 1:1 to 1000:1, preferably DDR, Sigma-1, and ZSM-58, in swing adsorption processes to selectively adsorb CO2, N2, and H2S, utilizing structured adsorbent contactors with parallel flow channels to enhance selectivity and recovery through rapid cycle pressure swing adsorption (RCPSA) and partial pressure swing adsorption (PPSA) technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PSA or TSA processes are used to remove CO2, N2, and H2S from natural gas, then gas separation can be achieved, but methane recovery is low and operational costs are high
Solution Approach 1:
The patent employs 8-ring zeolites with specific Si:Al ratios (1:1 to 1000:1) that possess controlled pore structures and molecular sieve characteristics. These porous materials selectively adsorb CO2, N2, and H2S molecules while allowing methane to pass through, achieving high methane recovery (>95%) by exploiting the size and affinity differences between gas molecules and the zeolite pore structure.
Solution Approach 2:
The patent utilizes rapid cycle pressure swing adsorption (RCPSA) and partial pressure swing adsorption (PPSA) technologies that dynamically change pressure parameters to enhance separation efficiency. By rapidly cycling between high pressure (adsorption phase) and low pressure (desorption phase), the system achieves both high methane recovery and reduced operational costs through optimized process parameters.
2Reliability
If conventional adsorbents are used in PSA processes, then gas separation is possible, but selectivity for CO2, N2, and H2S removal is insufficient
Solution Approach 1:
The patent employs 8-ring zeolites with specifically engineered Si:Al ratios (1:1 to 1000:1) that create localized active sites within the pore structure. These localized regions exhibit enhanced affinity for CO2, N2, and H2S molecules through electrostatic interactions and hydrogen bonding, achieving high selectivity while maintaining overall removal efficiency through the distributed pore network.
Solution Approach 2:
The patent utilizes composite zeolite structures combining silica and alumina in specific ratios to create materials with tailored pore characteristics and surface properties. This composite approach allows simultaneous optimization of selectivity for acid gas removal and productivity for methane recovery by balancing hydrophobicity, pore size, and adsorption capacity.
3Quantity of substance
If high pressure operation is used to increase adsorption capacity, then more gas can be processed, but methane recovery decreases
Solution Approach 1:
The patent implements rapid cycle pressure swing adsorption with cycle times optimized to maintain high adsorption capacity while preserving methane recovery. The periodic switching between adsorption (high pressure) and desorption (low pressure) phases ensures that CO2, N2, and H2S are selectively removed without excessive methane adsorption, achieving >95% methane recovery even at high feed pressures through controlled cyclic operation.
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 approach significantly improves the recovery of methane to over 95% and efficiently removes CO2, N2, and H2S from natural gas, even at high pressures, reducing operational costs and equipment size compared to conventional methods.
Implementation Method 1
PSA processes rely on the fact that under pressure gases tend to be adsorbed within the pore structure of the microporous adsorbent materials or within the free volume of a polymeric material. The higher the pressure, the more gas is adsorbed. When the pressure is reduced, the adsorbed gas is released, or desorbed.
Implementation Method 2
Different molecules can have different affinities for adsorption into the pore structure or open volume of the adsorbent. This provides one mechanism for the adsorbent to discriminate between different gases.
Implementation Method 3
zeolites and some types of activated carbons, called carbon molecular sieves, may utilize their molecular sieve characteristics to exclude or slow the diffusion of some gas molecules into their structure. This provides a mechanism for selective adsorption based on the size of the molecules
Implementation Method 4
Either of these mechanisms can be employed to selectively fill the micropore structure of an adsorbent with one or more species from a multi-component gas mixture. The molecular species that selectively fill the micropores or open volume of the adsorbent are usually referred to as the 'heavy' components and the molecular species that do not selectively fill the micropores or open volume of the adsorbent are usually referred to as the 'light' components.
Data Source
AI summary
The removal of one or more of the gases CO2, N2 and H2S from gas mixtures containing at least one of said gases with use of an 8-ring zeolite having a Si:Al ratio from about 1:1 to about 1000:1. The preferred gas mixture is a natural gas feedstream and the preferred 8-ring zeolite is DDR.