Abstract: A stream of raw biogas is feed to an upstream-most compression stage of a multi-stage compression unit to produce a feed gas for separation by a gas separation membrane-based purification unit into a methane-enriched product gas stream, one or more recycle gas streams, and one or more waste gas streams. The methane-enriched product gas stream is compressed by a downstream or downstream-most compression stage of the multi-stage compression unit to produce a stream of product compressed natural gas.

Abstract: The invention relates to a method for utilizing low-quality tail gas derived from a pressure swing adsorption system or membrane system, which is used to upgrade biogas, as a beneficial fuel for the facility and/or digester boiler.

Abstract: A natural gas stream derived from a landfill and containing impurities including siloxane impurities is purified by a PSA process to produce a methane-rich product stream which is substantially free of siloxane impurities. A methane-rich vent stream having a pressure less than the product stream is formed that is also free of siloxanes and can be used as a fuel stream to run a compressor for the PSA process.

Abstract: The present invention is directed to an improved integrated process for the removal of heavy hydrocarbons, carbon dioxide, hydrogen sulfide, and water from a raw natural gas feed stream. More specifically, the integrated process of the present invention comprises a three step process involving the adsorption of heavy hydrocarbons and water on an adsorbent bed selective for the same, a subsequent aqueous lean amine treatment for the absorptive removal of acid gases, such as carbon dioxide and hydrogen sulfide, and an adsorptive removal of water. The process of the present invention results in a highly purified dry natural gas product stream.

Abstract: The present invention is directed to an improved integrated process for the removal of heavy hydrocarbons, carbon dioxide, hydrogen sulfide, and water from a raw natural gas feed stream. More specifically, the integrated process of the present invention comprises a three step process involving the adsorption of heavy hydrocarbons and water on an adsorbent bed selective for the same, a subsequent aqueous lean amine treatment for the absorptive removal of acid gases, such as carbon dioxide and hydrogen sulfide, and an adsorptive removal of water. The process of the present invention results in a highly purified natural gas product stream.

Abstract: Recovering sulfur from a gas stream containing hydrogen sulfide by oxidizing the gas stream to convert the hydrogen sulfide in the gas stream to sulfur oxide, and thus form a sulfur oxide enriched gas stream. The sulfur oxide enriched gas stream is contacted with a solid, sulfation resistant adsorbent bed at relatively low temperatures to extract the sulfur oxides and retain them as sulfur compounds, thus forming a sulfur oxide depleted gas stream. The adsorbent bed is then contacted with an inert or reducing gas stream to reduce the retained sulfur compounds to sulfur and/or sulfur dioxide and thereby form an enriched sulfur and/or sulfur dioxide bearing stream. The elemental sulfur is recovered and/or the sulfur dioxide bearing stream may be recycled to the Claus unit for further conversion.

Abstract: A pressure swing adsorption process for the separation of nitrogen and/or CO2 from natural gas utilizes two separate pressure swing adsorption stages, the first containing a hydrocarbon-selective adsorbent and the second containing a nitrogen- and/or CO2-selective adsorbent. In the process, the product stream from the first pressure swing adsorption unit contains a natural gas stream having a reduced hydrocarbon content and the product stream from the second pressure swing adsorption unit is a natural gas stream having a reduced nitrogen and/or CO2 concentration. An intermediate pressure stream containing methane from the second pressure swing adsorption unit is used to desorb the hydrocarbons from the first pressure swing adsorption unit. The C3+ hydrocarbons can be separated as liquids from the methane.