Activated Carbon for Oil Vapor Removal

Activated Carbon for Oil Vapor Control in PSA Air Preparation

In Pressure Swing Adsorption (PSA) nitrogen generation systems, ensuring the purity of compressed air is critical to the stability and performance of the overall process. One key step in the air preparation stage is the removal of oil vapor, typically introduced through oil lubricated compressors. Even in small concentrations, these vapors can affect gas quality and lead to long term system inefficiencies if not addressed.
To support consistent and efficient operation of the Carbon Molecular Sieve (CMS) bed, activated carbon is commonly integrated as a pre filtration media to capture and retain these vapor phase hydrocarbons from the incoming air stream.

Role of Activated Carbon in the PSA Air Preparation Process

Activated carbon functions through adsorption, a physical process by which non polar molecules such as oil vapors and VOCs are retained within the porous structure of the carbon. This process occurs without chemical reaction and is especially effective at ambient temperatures and under variable pressure conditions typical in PSA systems.

In CMS based PSA units, activated carbon is used specifically to:

• Remove oil vapor and volatile organic compounds (VOCs)
• Prevent vapor phase hydrocarbons from reaching the CMS layer
• Maintain gas stream consistency before nitrogen separation

Its placement in the air treatment train typically after coalescing filters and before the dryer or CMS tower is critical to intercepting fine oil particles that bypass earlier filtration stages.

Why Oil Vapor Removal Supports CMS Performance

Carbon Molecular Sieve materials are designed to selectively adsorb oxygen from compressed air, enabling nitrogen production with purities up to 99.9999%. However, for CMS to perform as designed, the feed air must be stable and free of interfering contaminants.

Oil vapors do not directly deactivate CMS but can lead to gradual surface coating, changes in mass transfer dynamics, and inconsistent pressure equalization, which over time may result in:

• Irregular nitrogen recovery rates
• Longer cycle times
• Accumulation of residues in the CMS bed structure

By intercepting these contaminants before they enter the CMS chamber, activated carbon acts as a protective barrier, preserving CMS integrity and system reliability across extended operating cycles.

Integration into PSA Systems

Activated carbon is part of a multi stage air preparation process, which generally follows this flow:

1. Particulate Filtration (removal of dust and solid particles)
2. Coalescing Filtration (removal of liquid phase oil and water aerosols)
3. Activated Carbon (adsorption of oil vapor and VOCs)
4. Drying / Desiccant Stage (removal of H₂O and CO₂)
5. Gas Separation Stage (CMS for nitrogen generation)

This configuration ensures that the CMS bed receives clean, dry, and hydrocarbon free air, allowing the system to achieve designed nitrogen purity and production efficiency.