Helium Purification via Membrane and PSA Segmentation
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Solution Overview
Problem
Current methods for helium purification from streams containing high CO2 and nitrogen/methane concentrations are inefficient, as they either require large adsorption beds or result in significant CO2 venting, which is environmentally detrimental, and do not effectively manage low helium levels and high CO2 concentrations.
Innovation Solution
A process combining partial condensation, gas separation membranes, and pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA) to separate helium from CO2 and other components, with integrated heat exchanger and membrane stages to achieve high helium purity while minimizing CO2 emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PSA technology is used to purify helium from streams with high CO2 and nitrogen/methane concentrations, then helium purity can be achieved, but large adsorption beds are required which reduces process efficiency and increases device complexity
Solution Approach 1:
The purification process is divided into multiple stages: first a membrane separation unit pre-concentrates helium from the feed stream, then the concentrated stream is fed to PSA units for final purification. This segmentation allows each unit to operate optimally - the membrane handles bulk separation reducing the load on PSA beds, while PSA achieves high purity. The result is smaller adsorption beds compared to using PSA alone on low-concentration feeds.
Solution Approach 2:
The membrane separation unit performs preliminary concentration of helium before the stream enters the PSA units. By pre-concentrating helium and removing some CO2 and nitrogen/methane upfront, the subsequent PSA beds receive a feed with higher helium content, requiring smaller bed volumes to achieve the same purity level. This preliminary action reduces the overall device complexity.
2Manufacturing precision
If cryogenic separation is used to remove CO2 from helium streams, then CO2 can be separated, but significant CO2 venting occurs which is environmentally detrimental
Solution Approach 1:
Instead of venting CO2 to atmosphere as in traditional cryogenic processes, the patent recovers CO2 by condensing it from the membrane permeate stream using a heat exchanger. The CO2 is condensed at temperatures below its critical point and collected as liquid CO2 product. This recovery approach eliminates harmful emissions while maintaining effective CO2 separation from the helium stream.
Solution Approach 2:
The patent converts the harmful CO2 emission into a beneficial outcome by condensing and recovering CO2 as a saleable liquid product. The CO2 that would normally be vented is instead captured through heat exchange condensation and sold as a commodity, turning an environmental liability into an economic asset while achieving complete CO2 separation from helium.
3Ease of manufacture
If membrane separation is used to concentrate helium, then cost effectiveness is improved, but only limited enrichment is achieved requiring multiple stages
Solution Approach 1:
The process uses a segmented approach where membrane units perform the bulk enrichment at low cost, followed by PSA units for final high-purity production. The membrane stage handles the majority of separation work efficiently and economically, while the PSA stage provides the final purification boost. This segmentation allows the system to achieve high productivity and purity without requiring excessive membrane stages.
Solution Approach 2:
The patent changes operational parameters by using the membrane permeate stream (containing concentrated helium and CO2) as feed to the PSA units instead of using raw feed or using membrane retentate. This parameter change optimizes the input composition for PSA, improving its efficiency and reducing the number of stages needed while maintaining cost effectiveness.
4Quantity of substance
If CO2 concentration in feed stream is high, then the process must handle significant CO2 loads, but traditional methods require large equipment or result in CO2 venting
Solution Approach 1:
The patent recovers CO2 from the membrane permeate stream by condensing it in a heat exchanger. The condensed CO2 is collected as liquid product and can be sold or sequestered. This recovery approach allows the process to handle high CO2 loads efficiently without requiring oversized equipment, as the CO2 is continuously removed and recovered rather than accumulated or vented.
Solution Approach 2:
The high CO2 load in the feed stream, which would normally be a burden requiring large equipment or venting, is converted into a beneficial liquid CO2 product through condensation and recovery. The CO2 that would be waste is instead captured and sold, reducing equipment size requirements while adding economic value to the process.
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 helium purity of at least 70 mol % (often 98-99.9 mol %) while reducing CO2 emissions by reinjecting it for geological sequestration, enhancing the efficiency and environmental sustainability of helium purification.
Implementation Method 1
The feed stream is partially condensed, in one or more steps, in order to obtain at least one helium-rich gas stream and at least one CO2-rich liquid stream
Implementation Method 2
At least a fraction of the compressed permeate stream is introduced into a heat exchanger at which the introduced at least one fraction of the compressed stream is partially condensed to produce a gaseous permeate stream and a liquid permeate stream
Implementation Method 3
At least a fraction of the gaseous permeate stream is further purified in at least one pressure swing adsorption unit to obtain a purified helium stream containing at least 70 mol % helium
Data Source
AI summary
A method and system for purification of helium and CO2 from a stream containing at least Helium, CO2, nitrogen or methane uses a combination of cryogenic, membrane and adsorption technologies.