Continuous Separation
When the specified feed conditions and pressure difference are maintained, membrane separation operates continuously and is well suited to continuous gas supply or treatment.
Membrane Technology
Gas Separation Membrane Technology
Gas separation membranes use differences in the rates at which gas components permeate a polymer membrane to achieve continuous separation under a pressure difference. Because individual components pass through the membrane at different rates, a feed gas can be divided into permeate and non-permeate streams.
This behavior is generally described by the solution-diffusion mechanism. Gas molecules first dissolve into the membrane material and then diffuse through it at different rates. The combined differences in solubility and diffusivity give the membrane its selectivity.
Mairui applies polysulfone hollow-fiber membrane technology to nitrogen generation, oxygen enrichment, CO₂ / CH₄ separation and gas dehumidification. Module design, potting, factory inspection, performance verification and system integration are developed around the actual operating conditions of each project.
Separation Principle
How Membrane Separation Works
Polymer gas separation membranes generally operate through a solution-diffusion mechanism. Under pressure, gas molecules first dissolve into the polymer membrane material and then diffuse through the membrane at different rates. The combined differences in solubility and diffusivity create selectivity between the components in a gas mixture.
Faster-permeating components pass preferentially to the lower-pressure side and form the permeate stream. Slower-permeating components continue through the module and become enriched in the non-permeate stream.
Either the permeate or non-permeate stream may serve as the product, depending on the separation objective. Nitrogen generation typically uses the nitrogen-rich non-permeate stream, while oxygen enrichment uses the oxygen-enriched permeate stream. Product-specific flow paths and performance information are provided on the corresponding product pages.
Module Structure
Inside the Hollow Fiber Membrane Module
Mairui nitrogen, oxygen-enrichment, CO₂-separation and gas-dehumidification modules all use polysulfone hollow-fiber membranes. The hollow-fiber geometry provides a large effective membrane area within a relatively compact module volume, supporting efficient gas contact and continuous separation.
Once potted into a module, the hollow fibers work together with potting materials, seals, end components, housing and process connections to form an installable gas separation element. Module design involves more than membrane area alone; gas distribution, pressure drop, sealing integrity, housing construction and system connections must also be considered. Module and flow-path configuration therefore vary with the separation duty.
- Polysulfone Hollow Fibers
- Potting Material
- Seals
- Housing & End Components
Engineering Characteristics
Why Membrane Separation?
The following points describe engineering characteristics of the membrane separation process; they do not mean that every project will achieve the same economics or performance. Technology selection must still consider purity, flow, pressure, recovery, operating profile and site conditions.
Modular Configuration
System capacity can be adjusted through module quantity, parallel arrangement and process configuration, allowing the design to be scaled to different project duties.
Compact System Layout
Hollow fibers provide a large effective membrane area within a limited volume, supporting relatively compact membrane banks and system layouts.
No Moving Parts Inside the Membrane Module
The membrane module itself contains no moving parts. Routine maintenance is primarily associated with feed-gas pretreatment, valves, instruments and other system auxiliaries.
No Phase Change in the Membrane Separation Step
The membrane step relies on pressure difference and selective permeation rather than liquefaction or phase change. Total system energy demand still depends on compression, pretreatment and operating conditions.
Product Stream Selected by Separation Duty
Different applications may use either the permeate or non-permeate stream as the product. Nitrogen generation uses the nitrogen-rich non-permeate stream, while oxygen enrichment uses the oxygen-enriched permeate stream.
Integration with Pretreatment and Controls
Membrane modules can be integrated with filtration, drying, cooling, monitoring and control functions to form systems tailored to the feed gas and product requirements.
Applicable to Multiple Separation Duties
With the appropriate module and process design, selective permeation can be applied to air separation, CO₂ / CH₄ separation, water-vapor removal and other defined separation duties.
Performance Factors
What Determines Membrane Performance?
Feed Gas Composition
The proportions of the gas components, together with moisture, oil, particles and other contaminants, influence the separation duty, membrane selection, pretreatment scope and resulting product performance.
Feed Pressure
The pressure difference across the membrane is an important permeation driving force. Changes in feed pressure can affect product flow, separation performance and the required membrane area.
Feed Temperature
Temperature changes gas solubility and diffusion behavior within the polymer membrane and must therefore be considered together with pressure, feed composition and product requirements.
Product Specification
Higher purity, higher target concentration or lower dew-point requirements generally change the available product flow and may affect module quantity, recovery and process configuration.
Membrane Area & Process Arrangement
Module quantity, parallel arrangement, multi-stage separation and recycle configuration jointly affect system capacity, product specification and recovery. A complete system cannot be assessed from a single module rating alone.
Feed Gas Quality
Stable, clean feed gas that meets the specified design conditions is essential for continuous membrane operation. The contaminants and inlet conditions that require control depend on the gas source, module and separation duty.
Membrane performance data are meaningful only when the corresponding feed composition, pressure, temperature, product specification and test conditions are defined. Comparing flow, purity, concentration or dew point without those conditions can lead to incorrect conclusions.
Pretreatment
Why Pretreatment Matters
Membrane modules require stable, clean feed gas that meets the specified design conditions. Free liquid, oil, particles, moisture and application-specific contaminants can affect the long-term operation of the membrane modules, valves, instruments and process piping. Pretreatment scope must therefore be determined from the gas source, operating pressure, temperature and separation duty.
Depending on the project, pretreatment may include filtration, cooling, liquid removal, drying and treatment of specific contaminants. Its purpose is to provide suitable inlet conditions for membrane separation and maintain consistent system operation. Pretreatment supports the membrane process; it does not replace the membrane’s selective separation function.
Pretreatment is therefore not a fixed equipment list. Compressed air, biogas, natural gas and other industrial gases differ significantly in composition and contaminants, so the appropriate treatment scheme can only be defined after feed-gas analysis and operating boundaries have been confirmed.
System Integration
From Membrane Modules to Membrane-Based Systems
A membrane module becomes part of a practical gas separation system only when it is matched to the actual operating conditions and process arrangement. Mairui evaluates feed composition, capacity, pressure, temperature and product requirements to determine module quantity, membrane-bank arrangement, flow paths, staging and recycle configuration.
Building on membrane module design, potting, factory inspection and performance verification, Mairui integrates the membrane banks with the required pretreatment, piping, valves, monitoring and control functions to form a project-specific membrane-based gas separation system. The final supply scope is defined by the customer’s existing facilities, site interfaces and project responsibilities.
- Module-to-duty matching
- Membrane-bank and process configuration
- Pretreatment and control integration
- Project boundary and site interfaces
Engineering Data & Resources
Engineering Data & Resources
Technical principles are best understood together with actual operating conditions and engineering data. The following resources connect to Mairui’s published product performance and process information without duplicating detailed specifications on this page.
FAQ
Membrane Technology FAQ
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