VPSA biogas upgrading systems, 450–4.000 Nm³/h

VPSA systems convert biogas into biomethane, a renewable gaseous fuel that replaces natural gas. The plants process 450–4.000 Nm³/h of raw biogas from agricultural facilities, organic waste treatment plants and wastewater treatment works. Gas conditioning and adsorption separation form an integrated, automated process.

Biomethane is used for filling cylinders at 250–300 bar, injection into public gas grids and supply in liquefied form. Cylinder filling requires additional compression; liquid biomethane requires liquefaction. The high-pressure compressor, grid injection unit and liquefaction plant are supplied separately.

VPSA stands for Vacuum Pressure Swing Adsorption. Pressurised biogas passes through a solid adsorbent: CO₂ is retained on its surface and in its pores, while methane-enriched gas leaves the vessel. The pressure is then reduced, and vacuum pumps remove the retained CO₂. This restores the adsorbent's capacity for the next purification cycle.

The adsorption vessels operate alternately: some purify the gas while others regenerate. Coordinated cycles provide a continuous biomethane stream. Automatic control adjusts cycle duration as raw gas flow changes and maintains the specified product quality. Regeneration allows the adsorbent to be reused without replacement after every cycle.

Cooling the raw biogas condenses water vapour; the liquid is separated and drained. A blower feeds the gas to the subsequent purification stages. Reheating before the activated carbon filters prevents condensation within the filter media.

Activated carbon removes hydrogen sulphide. A lead filter and a polishing filter connected in series provide two-stage treatment. Switching pipework allows their operating order to be reversed. After desulphurisation, the gas is cooled again to remove moisture before compression.

A screw compressor produces the pressure required for adsorption separation. Dry compression prevents contact between the process gas and compressor lubricating oil. Cooling after compression removes heat and condenses water vapour. Subsequent reheating prepares the gas for the adsorption module. An inlet buffer vessel stabilises the flow to the compressor.

Vacuum regeneration releases the retained CO₂ and restores the adsorbent's working capacity. Separation uses a solid adsorbent without scrubbing water or an amine solution. Condensate formed during cooling is drained separately. Compression and evacuation create the alternating pressure levels within the adsorption vessels.

The CO₂-rich stream leaves through a separate gas line. An optional CO₂ purification and liquefaction plant can be added to produce a second marketable product alongside biomethane. CO₂ recovery and liquefaction equipment is supplied separately from the main upgrading system.

The plant operates automatically. A touchscreen displays the process diagram, operating parameters and equipment status. Programmed sequences handle start-up and shutdown; the event log records warnings and faults with dates and times. Operating-hour counters support maintenance planning for the compressor, pumps and auxiliary equipment.

Remote access provides monitoring, diagnostics and control. Functions include alarm and warning notifications, historical data access and operating parameter adjustment. The safety circuit combines the emergency stop with equipment protection signals.

Modular construction with factory assembly and testing reduces work on site. Equipment is housed in containers with service openings for inspection and maintenance. Thermal and acoustic insulation, ventilation and lighting support equipment operation; gas alarms and fire detection complement the safety system. Containerisation simplifies module transport and installation at existing biogas plants.

The water dew point of biomethane is below −65 °C. The H₂S content after gas conditioning is less than 3 ppm.