PSA Tail Gas Membrane Sequencing for H2 Recovery and CO2 Separation
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Solution Overview
Problem
Conventional methods for hydrogen (H2) recovery from PSA tail gases are limited by high CO2 concentrations, leading to reduced H2 enrichment rates and inefficient overall recovery processes.
Innovation Solution
Employing two PSA columns to separately treat H2-containing streams and using CO2 selective membranes to first recover CO2 from the first PSA tail gas before mixing it with a second PSA tail gas, followed by H2 recovery using an H2 selective membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to recover H2 from PSA tail gases with high CO2 concentrations, then the process can handle the gas stream, but the H2 enrichment rate is reduced and recovery efficiency is lowered
Solution Approach 1:
The gas treatment process is divided into distinct stages: first CO2 separation using a CO2 selective membrane, then H2 recovery using an H2 selective membrane. This segmentation allows each membrane to be optimized for its specific function, with the CO2 selective membrane handling the high CO2 concentration stream first, followed by H2 selective membrane processing of the CO2-lean stream, thereby achieving high H2 recovery efficiency despite initial high CO2 concentrations
Solution Approach 2:
CO2 is removed from the PSA tail gas stream before H2 recovery operations begin. The CO2 selective membrane performs preliminary CO2 separation, creating a CO2-lean rejected gas stream that is then suitable for efficient H2 recovery in the second membrane unit. This preliminary CO2 removal action enables subsequent high-efficiency H2 enrichment
2Productivity
If larger membrane area is used to handle high CO2 concentrations, then CO2 separation efficiency improves, but the overall process complexity and cost increase
Solution Approach 1:
The separation process is segmented into two sequential membrane units with distinct functions. The first CO2 selective membrane handles CO2 separation from the high CO2 concentration PSA tail gas, while the second H2 selective membrane handles H2 recovery from the CO2-lean stream. This segmentation distributes the separation task across two specialized units rather than requiring one large multi-functional membrane system, optimizing both efficiency and complexity
Solution Approach 2:
The CO2 selective membrane acts as an intermediary unit that processes the high CO2 concentration stream before it reaches the H2 selective membrane. By introducing this intermediate CO2 removal stage, the system protects the H2 selective membrane from being overloaded by high CO2 concentrations, allowing it to operate efficiently with smaller area while achieving high H2 recovery
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
Improves overall H2 recovery efficiency by reducing the membrane area required and enhancing the heating value of the final tail gas, while achieving high CO2 recovery and H2 purity.
Implementation Method 1
separating CO2 from the first PSA tail gas using a CO2 selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas
Implementation Method 2
separating the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas
Implementation Method 3
performing a first pressure swing adsorption (PSA) process generating a first H2-product gas and a first PSA tail gas from a first feed gas
Data Source
AI summary
A method of treating a gas stream that includes: performing a first pressure swing adsorption (PSA) process generating a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas including a residual H2 and CO2; separating CO2 from the first PSA tail gas using a CO2 selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas; performing a second PSA process generating a second H2-product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas including another residual H2; mixing the CO2-lean rejected gas and the second PSA tail gas to generate a mixed tail gas; and separating the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas.