Integrated ptsa/membrane method and system for h2s and co2 removal from biogas

A biogas upgrading system based upon PTSA and gas separation membranes, comprising:

• a source of raw biogas comprising methane, CO2, water, VOCs, and H2S;
• a main compressor including a suction inlet in fluid communication with the source and receiving a stream of raw biogas from the source;
• a PTSA unit comprising two or more adsorbent beds each of which is selective for water, VOCs, and H2S over CO2 and for H2S over methane, the PTSA unit being in downstream fluid communication with the main compressor and receiving a stream of a PTSA feed gas therefrom, the PTSA unit being adapted and configured to adsorb water, VOCs, and H2S from the PTSA feed gas and produce a PTSA product gas deficient in water, VOCs, and H2S in comparison to the PTSA feed gas;
• a first gas separation membrane stage comprising one or more gas separation membranes selective for CO2 and O2 over methane, a feed gas inlet of the first gas separation membrane stage being in downstream fluid communication with the PTSA unit, the first gas separation membrane stage being configured and adapted to separate the PTSA product gas into a first stage permeate gas stream and a first stage retentate gas stream;
• a second gas separation membrane stage comprising one or more gas separation membranes selective for CO2 and O2 over methane, a feed gas inlet of the second gas separation membrane stage being in downstream fluid communication with the retentate outlet of the first gas separation membrane stage and receiving the first stage permeate gas stream therefrom, the second gas separation membrane stage being adapted and configured to separate the first retentate gas stream into a second permeate gas stream and a second retentate gas stream, wherein:
• the PTSA unit is in fluid communication with the permeate gas outlet of the first gas separation membrane stages so as to receive a flow of the first stage permeate gas for use as a thermal regeneration gas to thermally regenerate and desorb water, VOCs, and H2S that was adsorbed upon the adsorbent beds from the PTSA feed gas stream;
• and
• the PTSA unit is in fluid communication with the permeate gas outlet of the second gas separation membrane stage so as to receive a flow of the second permeate gas stream for use as a cool down stream for cooling one or more adsorbent beds after thermal regeneration thereof;
• and
• a treatment unit in downstream fluid communication with the PTSA unit so as to receive a waste gas from the PTSA comprised of the thermal regeneration gas and water, VOCs, and H2S, the treatment unit being adapted and configured to either oxidize or burn the VOCs contained in the waste gas.