Helium Purification from Methane with Integrated Nitrogen Rejection
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Solution Overview
Problem
Existing methods for purifying helium from methane/nitrogen mixtures using membrane and pressure swing adsorption (PSA) technology result in a residue gas mixture with similar proportions of methane and nitrogen, lacking a cost-effective membrane-based solution for nitrogen rejection.
Innovation Solution
A process integrating helium and nitrogen membrane separation units with PSA, where the helium membrane residue is further processed through nitrogen membrane units, producing a helium-rich product and a fuel gas stream with a higher heating value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If membrane and PSA technology are used to purify helium from methane/nitrogen mixtures, then helium purification is achieved, but the residue gas remains a mixture of methane and nitrogen in similar proportions as the feed gas
Solution Approach 1:
The process segments the residue gas treatment into two distinct membrane separation stages: a first nitrogen membrane separation unit that reduces nitrogen content, and a second nitrogen membrane separation unit that further purifies the gas. This segmentation allows progressive nitrogen rejection while maintaining methane concentration, transforming the single-stage residue into a multi-stage purification pathway.
Solution Approach 2:
The invention extracts nitrogen from the residue gas stream using nitrogen-selective membrane separation units. The nitrogen permeate is separated and removed from the system, while the methane-rich retentate is retained and can be reused as fuel gas or further processed. This extraction principle directly addresses the nitrogen content problem in the residue gas.
2Manufacturing precision
If nitrogen is rejected from the residue gas, then fuel gas quality improves, but additional membrane separation units are required
Solution Approach 1:
The nitrogen membrane separation units serve multiple functions: they reject nitrogen to improve fuel gas quality, produce a helium-enriched stream that can be recycled to the helium separation unit, and generate a methane-rich permeate suitable for fuel gas applications. This multi-functionality justifies the additional equipment by delivering multiple benefits from a single process addition.
Solution Approach 2:
The process merges the nitrogen rejection function with the existing helium purification workflow by integrating the nitrogen membrane units into the residue gas handling system. The nitrogen permeate stream is combined with or redirected to fuel gas products, while the retentate is recycled back to the helium separation unit, creating a unified multi-functional system.
3Ease of manufacture
If the residue gas is discarded, then the helium purification process is simple, but valuable methane is wasted
Solution Approach 1:
Instead of discarding the residue gas, the invention recovers valuable methane by separating it from nitrogen using nitrogen-selective membrane units. The methane-rich permeate stream is recovered and directed to fuel gas products, while the nitrogen is rejected. This recovery principle transforms waste methane into a valuable by-product while maintaining process efficiency.
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 achieves high-purity helium production and generates a valuable fuel gas stream with enhanced heating value, enhancing the efficiency and economic viability of helium purification.
Implementation Method 1
introducing the feed gas stream into a first helium membrane separation unit, thereby producing a first helium membrane permeate and a first helium membrane residue
Implementation Method 2
introducing at least part of the first residue into a first nitrogen membrane separation unit thereby producing a first nitrogen membrane permeate stream
Implementation Method 3
introducing a stream derived from the first helium membrane permeate into a hydrogen PSA unit thereby producing a helium rich product stream
Data Source
AI summary
A process to purify helium from a feed gas stream containing a mixture of at least nitrogen, methane and helium including introducing the feed gas stream into a first helium membrane separation unit, thereby producing a first helium membrane permeate and a first helium membrane residue; introducing at least part of the first residue into a first nitrogen membrane separation unit thereby producing a first nitrogen membrane permeate stream; introducing a stream derived from the first helium membrane permeate into a hydrogen PSA unit thereby producing a helium rich product stream. Wherein a stream derived from the first nitrogen membrane permeate stream exits the system as a fuel gas product stream. Wherein the feed gas stream has a higher heating value, and wherein the first nitrogen membrane permeate stream has a higher heating value at least 5% higher than the higher heating value of the feed gas.