An improved method and apparatus for removing acid gases and other impurities from raw biogas streams, such as biogas from landfills or biogas from controlled anaerobic digestion, is disclosed. The method provides efficient generation of high-purity renewable natural gas from raw biogas. The biogas is treated in a multi-stage membrane system integrated with compression equipment. The membrane separation stages are integrated with high-pressure and low-pressure compressors with the low-pressure compressor operating in a defined pressure range. The combined system provides for efficient contaminant removal from raw biogas to generate high-purity methane products with reduced membrane area and compression energy consumption.

A natural gas fueling system supplies methane gas to an engine and includes a filter assembly. The filter assembly includes a gas inlet configured to receive inlet gas and a methane permeable filter configured to separate methane gas and first contaminant gases from the inlet gas. The natural gas fueling system also includes a reformer apparatus configured to convert the first contaminant gases into a reformed gas stream including methane gas. The reformed gas is supplied to the gas inlet and is recirculated through the filter assembly to extract the methane gas from the reformed gas stream.

A method for treating a crude natural gas feed stream comprising methane and having a first carbon dioxide concentration, said method comprising the steps of: subjecting the crude natural gas feed stream to a separation process to provide: a purified natural gas stream having a second carbon dioxide content which is lower than the first carbon dioxide concentration in said crude natural gas stream; and, a carbon dioxide stream comprising carbon dioxide as the major component and methane; recovering the purified natural gas steam; optionally mixing the carbon dioxide stream with make-up methane and/or make-up air; passing the carbon dioxide stream and optional make-up methane or air through a heat exchanger to raise the temperature of the stream to the desired inlet temperature T.sub.1 of an oxidation reactor; optionally mixing the carbon dioxide stream with make-up methane and/or make-up air; passing the heated stream from step (d) and any optional make-up methane and/or air to the oxidation reactor containing an oxidation catalyst, where the methane is oxidised; removing a gas stream including the products of the oxidation reaction from the reactor, said gas stream being at an outlet temperature T.sub.2 which is higher than the inlet temperature T.sub.1; passing the gas stream removed in step (g) through the heat exchanger against the carbon dioxide stream from step (a) to allow the heat to be recovered from the gas stream removed in step (g) and utilised to heat the carbon dioxide stream in step (d); and measuring the outlet temperature T.sub.2 and controlling the inlet temperature T.sub.1 by adjusting the amount of make-up methane and/or air added in step (c) and/or step (e).

A system provides oxygen enriched air to a wastewater treatment aeration system by utilizing a membrane unit coupled with a vacuum-generating device which applies a vacuum to the membrane unit thereby pulling out a flow of permeate having an enriched oxygen component. An aeration blower receives the flow of permeate and pressurizes it for delivery to the wastewater treatment aeration system. The membrane units may be in a variety of configurations, including a shell-less membrane. The membrane unit may also provide a stream of oxygen enriched air to a biogas fired power plant or other flue gas generator.

Disclosed is a purification unit (UE) configured to receive an inflow of biogas (BS) and to separate said received inflow of biogas (BS) into a stream of biomethane (BM), preferably containing at least 90% methane, and a stream of residual gases (GR1), referred to as combustion gases, the methane content of which is greater than 25%.

A process for treating an effluent gas stream arising from a manufacturing operation that produces an olefin or an olefin derivative to recover unreacted olefin. The process involves compressing the effluent gas stream, which comprises an olefin, a paraffin, and a third gas, to produce a first compressed stream, then directing the first compressed stream to a membrane separation pretreatment step. The permeate stream withdrawn from this step is enriched in olefin and is sent to a second compressor, which produces a second compressed stream that is then cooled and condensed. The condensation step produces a liquid condensate and an uncondensed gas stream. The uncondensed gas stream undergoes a second membrane separation step to produce another olefin-enriched permeate stream, which is recirculated within the process prior to the second compression step, and an olefin-depleted residue stream, which may be purged from the process.

A gas chromatographic method for analyzing natural gas and a natural gas upgrading system using the gas chromatographic method for analyzing natural gas. The method includes transporting the natural gas through a chiller, transporting the natural gas from the chiller to at least two gas upgrading membranes, and operating a gas chromatographic system having at least one upstream gas chromatograph and at least two downstream gas chromatographs. The at least one upstream gas chromatograph, the first downstream gas chromatograph, and the second downstream gas chromatograph all operate simultaneously and utilize the same heating oven to heat samples of natural gas.

An aircraft fuel deoxygenation and tank inerting system includes an inert gas source, a fuel deoxygenation system, and an air/fuel heat exchanger. The inert gas source is configured to supply inert gas having an oxygen concentration of less than 3%. The fuel deoxygenation system is adapted to receive fuel from a fuel source and the inert gas from the inert gas source. The fuel deoxygenation system is configured to remove oxygen from the fuel and thereby generate and supply deoxygenated fuel and oxygen-rich purge gas. The air/fuel heat exchanger is adapted to receive compressed air from a compressed air source and the deoxygenated fuel from the fuel deoxygenation system. The air/fuel heat exchanger is configured to transfer heat from the compressed air to the deoxygenated fuel, to thereby supply cooled compressed air and heated deoxygenated fuel.

Natural gas may be purified by removing C.sub.3+ hydrocarbons and CO.sub.2 in respective one or more separation units to yield conditioned gas lower in C.sub.3+ hydrocarbons and CO.sub.2 in comparison to the un-conditioned natural gas. Notably, the feed gas need not be subjected to joule-thomson expansion and molecular sieve dehydration performed by conventional processes. Rather, any water-rich reject stream from the separation unit(s) is dried downstream with a smaller compressor and smaller molecular sieve or gas separation membrane dehydration unit before it may be re-injected deep underground or deep under the sea bed.

Natural gas may be purified by removing C.sub.3+ hydrocarbons and CO.sub.2 in respective first and second gas separation membrane stages to yield conditioned gas lower in C.sub.3+ hydrocarbons and CO.sub.2 in comparison to the un-conditioned natural gas.