Raw biogas from an anaerobic digester is fed to a membrane separation unit that produces methane rich biomethane and a CO2 rich permeate that is recycled to the anaerobic digester where it is mixed with the digestate.

A membrane process is provided for separating light olefins from light paraffins to produce a polymer grade light olefin product stream that is about 99.5 mol % ethylene or propylene. The process involves multiple stages to achieve the high purity product and provides for processing hydrocarbon streams that have differing concentrations of light olefins.

A natural gas refining apparatus including a first separation membrane unit including a first separation membrane; and a second separation membrane unit provided in a subsequent stage of the first separation membrane unit. The second separation membrane unit includes a second separation membrane that allows an amine solution to circulate through the second separation membrane unit, and the natural gas refining apparatus refines raw natural gas containing CO.sub.2 by passing the raw natural gas through the first and second separation membrane units, separating CO.sub.2-rich gas with the first and second separation membranes, and absorbing CO.sub.2 with the amine solution circulating through the second separation membrane unit.

Methods and systems for measuring the concentration of a light gas in a main flow stream are disclosed herein. The methods include calculating a control parameter as a function of the concentration of the light gas in the main flow stream; dividing a portion of the main flow stream to produce a feed stream; and separating the feed stream by selective permeation across a semi-permeable membrane to produce a permeate stream enriched in the light gas and a retentate depleted in the light gas. A ratio of the flow rate of the feed stream to the flow rate of the main flow stream may be increased or decreased according to the control parameter. In addition, an area of the semi-permeable membrane may be increased or decreased according to the control parameter.

This invention relates to a multi-element membrane separator and separation method based on spiral-wound membrane elements. It includes a membrane housing, spiral-wound membrane elements, and baffles on both sides of the membrane housing, designed to secure the spiral-wound membrane elements. The permeate tubes of the spiral-wound membrane elements are connected to the openings in the perforated plates. Sealing rings are respectively provided at the connections of the permeate tubes and the perforated plate openings. This multi-element membrane separator enables a more compact arrangement of membrane elements, reducing the footprint of the membrane separation device. It also reduces the use of materials such as membrane housing, pipelines, and connecting fittings, thereby lowering equipment costs and the difficulty of membrane device assembly.

An apparatus/system for generating a high-purity nitrogen gas using a fuel cell includes; a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; a dehumidification mechanism that reduces moisture or water vapor content in an exhaust gas that is extracted from the fuel cell and has a lower oxygen concentration than air; and a filtering mechanism which includes a filter using fibers having different degrees of permeation for nitrogen and oxygen and converts the exhaust gas having a reduced moisture or water vapor content into a gas having an increased nitrogen concentration. The filter recovery ratio is higher when an oxygen concentration of a gas to be filtered is lower. The dehumidification mechanism is a pump unit including a water seal pump to provide an adiabatic expansion chamber in which the exhaust gas extracted from the fuel cell expands adiabatically.

An apparatus, systems comprising the apparatus, and methods of using and making the apparatus are disclosed, with the apparatus comprising an inlet, at least one oxygen membrane separator in communication with the inlet and in communication with an ambient airflow, with the ambient airflow comprising an ambient oxygen concentration, at least one piezoelectric pump in communication with the at least one oxygen membrane separator, and an outlet for emitting an enhanced oxygen concentration airflow.

Provided is an apparatus/system for generating a nitrogen-enriched gas reliably and stably using a fuel cell. The nitrogen gas generation apparatus/system comprises: a fuel cell configured to operate by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; and a catalyst combustion mechanism configured to cause an exhaust gas that is extracted from the fuel cell and has a lower oxygen concentration than air to react with the fuel gas on a combustion catalyst, and convert the exhaust gas having a lower oxygen concentration than air into a nitrogen-enriched gas having an increased nitrogen concentration.

A membrane process is provided for separating light olefins from light paraffins to produce a polymer grade light olefin product stream that is about 99.5 mol % ethylene or propylene. The process involves multiple stages to achieve the high purity product and provides for processing hydrocarbon streams that have differing concentrations of light olefins.

A system and method for producing hydrogen, including providing hydrocarbon and steam into a vessel to a region external to a tubular membrane in the vessel. The method includes steam reforming the hydrocarbon in the vessel via reforming catalyst to generate hydrogen and carbon dioxide. The method includes diffusing the hydrogen through the tubular membrane into a bore of the tubular membrane, wherein the tubular membrane is hydrogen selective.