Upgrading PSA

The SmartCycle^® PSA upgrading plant, from the manufacturer ETW Energietechnik, has been designed to purify a biogas with a composition of 50-65% CH₄ and the rest CO₂. The CO₂ content, along with other contaminants, is separated by a pressure swing adsorption (PSA) system from the main gas stream, thus producing a product gas (biomethane) with natural gas quality. The biomethane produced can be injected into the natural gas network or compressed to CNG. CH₄ concentration can be set up to 99%. The CO₂ stream can be used directly or liquefied for transport.

Pressure Swing Adsorption (PSA) is a widely applied physical process in the gas industry to purify different gas streams for a variety of industrial applications. The simplicity and especially the flexibility of this process, to automatically adapt to changing inlet gas conditions, makes the PSA process the choice of thousands of operators around the world. The highest actual run times (> 99%) coupled with the lowest energy consumption (<0.252 kWh / Nm³) ensure the best plant performance among landfill gas enhancement technologies.

Each of the compounds that compose the biogas stream has a different adsorption potential, allowing for the purification of CH₄. CO₂ is adsorbed on a molecular sieve while CH₄ is concentrated.

The PSA SmartCycle^® system automatically synchronizes the adsorption and desorption of different columns, which guarantees the continuous production of high-quality biomethane, even if the quality of the incoming biogas or its flow rate is varied. The only adjustable parameter is the cycle time. The system is self-regulating and fully automatable.

In addition to the PSA system described, a nitrogen rejection unit (RNU) integrated in the PSA system is included to remove the nitrogen content from the biogas (typically present in biogas from landfills). CH₄ is recovered in the NRU at about 10 mbar and buffer storage at higher pressure is available.