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.

The present invention relates to a novel apparatus and to a method of simultaneous separation of multiple gas streams having different compositions by means of gas separation membranes, wherein the respective gas streams supplied to the apparatus and to the method may be subject to fluctuations in their respective volume flow rates and compositions.

An apparatus for separating a gas mixture is provided in the form of a first membrane separation stage, a second membrane separation stage, a first and a second measuring device, and a controller. The first membrane separation stage is imparted with a first membrane area and separates the gas mixture into a first permeate stream and a first retentate stream. The second membrane separation stage is imparted with a second membrane area and is configured to separate the first permeate stream into a second permeate stream and a second retentate stream. The first and the second measuring devices are configured to measure process parameters and generate process control signals. Based on the process control signals, the controller modifies a membrane ratio defined with reference to the first membrane area and the second membrane area.

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.

The present application relates to a membrane separation device. According to the separation device of the present application, components to be separated using a separation membrane having a small area size can be separated with high selectivity and consequently processing efficiency and economical efficiency can be superbly improved; and according to a method for producing an expanded polystyrene which includes the membrane separation device, components to be separated using a separation membrane having a small area size, in particular, a volatile organic compound (VOC), can be separated with high selectivity and consequently processing efficiency and economical efficiency can be superbly improved, and also, by separating and recovering VOC, an effect in preventing environmental pollution caused by global warming is exhibited.

A plant for the membrane permeation treatment of a gaseous feedstream comprised of at least methane and carbon dioxide for producing a methane-enriched gaseous stream, comprises: a first membrane separation unit able to receive the gaseous feedstream and to produce a first carbon dioxide-enriched permeate and a first methane-enriched retentate, a second membrane separation unit able to receive the first retentate and to produce a second carbon dioxide-enriched permeate and a second methane-enriched retentate, a gas-gas ejector able to increase the pressure of the first permeate to a pressure of between 2 and 6 bar, more preferably between 3 and 4 bar, and a third membrane separation unit able to receive the first permeate compressed in the ejector and to produce a third methane-enriched retentate and a third CO2-enriched permeate.

A process for recovering a steam cracking feed from FCC absorber off-gas comprising ethylene, ethane and heavier hydrocarbons and light gases involves removing hydrogen, nitrogen, sulfur species, carbon monoxide/dioxide, methane and other impurities from the off-gas. An absorption zone is upstream of an acetylene selective hydrotreating reactor to remove sufficient hydrogen sulfide that can poison the selective hydrotreating catalyst but leave sufficient sulfur in the feed stream to prevent temperature runaway.

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.

The present disclosure relates to a method for removing carbon dioxide from hydrocarbons, the method comprising the steps of: (a) contacting a feed stream comprising hydrocarbons and carbon dioxide with one or more gas-separation membranes to produce a hydrocarbon-rich retentate gas stream and a permeate gas stream rich in carbon dioxide, the retentate gas stream containing less carbon dioxide relative to the feed stream; and (b) passing at least one of the retentate gas stream or the permeate gas stream through an absorption unit to produce a hydrocarbon-rich gas phase and a liquid absorbent phase containing said carbon dioxide. The present disclosure also relates to a system for doing the same.

Provided are an apparatus for separating and collecting carbon dioxide and a method of separating carbon dioxide, and more particularly, an apparatus and method of selectively separating carbon dioxide from a byproduct gas using a difference in negative pressure and a difference in carbon dioxide concentration between the inside of a separator, which is made of a ceramic-coated porous silicone membrane and in which the byproduct gas flows, and the outside of the separator in which carbon dioxide is collected.