Analysis of Membrane Separation Decarbonization Technology for Natural Gas

Membrane separation is a key process in the field of natural gas decarbonization. It achieves the separation of components such as CO₂ and CH₄ through the selective permeation of gas components by membrane materials. The core advantages and technical details are as follows:

Membrane separation depends on the solubility difference or diffusion rate difference of gases in the membrane material:

If the permeability of the membrane to CO₂ is much higher than that to CH₄ (such as in polyimide membranes), CO₂ will preferentially permeate to the downstream of the membrane (permeation side), while CH₄ will remain upstream (reflux side), thereby achieving CO₂ enrichment and CH₄ recovery.

The selectivity of membrane materials (the permeation ratio of CO₂ to CH₄) is a core indicator of separation efficiency. Highly selective membranes can significantly reduce energy consumption and equipment scale.

The membrane separation system needs to be collaboratively optimized from dimensions such as pretreatment, membrane materials, process design, and operating parameters to ensure stable operation:

• dewatering: Oil mist and liquid water are removed through a cyclone separator and a coalescing filter to prevent membrane fouling.
• dehydrocarbonation: If the natural gas contains C₅+ heavy hydrocarbons, a condensation separator (cooled to -20 to 0℃) is required to reduce the adsorption/clogging of hydrocarbons on the membrane.
• desulfurization: If H₂S is present, solid adsorbents (such as iron oxide) or amine pretreatment should be prioritized to prevent H₂S from corroding the membrane material.

• polyimide (PI) film: With high CO₂/CH₄ selectivity (α≈30 to 50) and high-temperature resistance (≤100℃), it is the mainstream choice in industry.
• cellulose acetate (CA) membrane: resistant to hydrocarbon contamination, but with relatively low selectivity (α≈20-30), suitable for scenarios with high hydrocarbon content.
• New hybrid matrix membrane (MMM): Nanoparticle doping enhances separation efficiency, in the research and development stage.