Asymmetric Membrane Plasticization for H2S Methane Separation
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Solution Overview
Problem
Existing membranes used for removing CO2 and H2S from natural gas feed streams have limitations in H2S/methane selectivity, leading to suboptimal gas treatment processes from both economic and performance perspectives.
Innovation Solution
The use of asymmetric hollow fiber membranes or asymmetric film composite membranes that include a porous layer and a nonporous skin layer, which plasticize during operation due to exposure to condensable gases with high critical temperature, thereby enhancing H2S/methane selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer membranes (polyimide or cellulose acetate) are used for CO2 and H2S removal, then the membranes can operate at normal conditions, but the H2S/methane selectivity is limited resulting in suboptimal gas treatment performance
Solution Approach 1:
The patent applies parameter changes by utilizing the plasticization effect of the membrane polymer matrix when exposed to condensable gases with high critical temperature (such as CO2 and H2S) at elevated pressures. This changes the physical state and free volume of the polymer, thereby enhancing gas separation performance. The membrane is operated at pressures where plasticization occurs, transforming the membrane from a rigid state to a more flexible, permeable state that improves H2S/methane selectivity while maintaining acceptable productivity
Solution Approach 2:
The patent employs asymmetric hollow fiber membranes or asymmetric film composite membranes that include a porous layer and a nonporous skin layer. This composite structure combines the advantages of both layers: the porous layer provides mechanical strength and supports the selective nonporous skin layer, which performs the actual separation function. The composite material approach enables the membrane to achieve both structural integrity and enhanced separation performance under operating conditions
2Reliability
If membrane plasticization is induced by exposure to condensable gases with high critical temperature, then H2S/methane selectivity is enhanced, but the membrane structure undergoes physical changes
Solution Approach 1:
The patent applies the dynamics principle by intentionally utilizing the dynamic plasticization behavior of the membrane polymer matrix. Rather than preventing physical changes, the invention embraces the reversible transformation of the membrane from a glassy, rigid state to a rubbery, flexible state when exposed to condensable gases at elevated pressures. This dynamic state change is reversible and occurs in response to operating conditions, allowing the membrane to adapt its properties to maximize separation performance while maintaining long-term stability through reversible transitions
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 plasticized membranes achieve a H2S/methane selectivity of 7 to 40 at 35°C and 45 bar, significantly improving the efficiency of acid gas removal from natural gas.
Implementation Method 1
The asymmetric hollow fiber membrane or the nonporous skin layer of the asymmetric film composite membrane plasticizes during the method by exposure to condensable gases with high critical temperature under the operating conditions
Implementation Method 2
passing a natural gas feed including methane and hydrogen sulfide (H2S) through a membrane at normal operating conditions
Data Source
AI summary
Disclosed is a method for removing hydrogen sulfide from natural gas. The method includes passing a natural gas feed including methane and hydrogen sulfide (H2S) through a membrane at normal operating conditions. The membrane is an asymmetric hollow fiber membrane or an asymmetric film composite membrane including a porous layer and a nonporous skin layer. The asymmetric hollow fiber membrane or the nonporous skin layer of the asymmetric film composite membrane plasticizes during the method by exposure to condensable gases with high critical temperature under the operating conditions. The membrane preferentially removes H2S over methane from the natural gas feed at a H2S/methane selectivity of from 7 to 40 when measured at 35° C. and 45 bar.