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.

Disclosed is an apparatus and method of preparing synthetic fuel using natural gas extracted from a stranded gas field on land or at sea as a raw material through a compact GTL process or a GTL-FPSO process. A parallel-type gas purification unit for controlling a molar ratio of synthetic gas and a concentration of carbon dioxide in the synthetic gas, in which a CO.sub.2 separation device and a bypass unit are disposed in parallel, is provided and, thus, the gas purification unit may prepare the synthetic gas by a steam carbon dioxide reforming (SCR) reaction using natural gas having different CO.sub.2 contents of various stranded gas fields and then supply the synthetic gas having an optimum composition suitable for a Fischer-Tropsch synthesis.

Carbon dioxide gas in a high-pressure gas to be treated is stably separated using a separation membrane. Upon separating carbon dioxide gas in a high-pressure gas to be treated using a separation membrane module including a separation membrane, a preliminary boosted gas is supplied to the separation membrane module before the supply of natural gas is started to boost a pressure on a primary side of the separation membrane to a preliminary pressure between a stand-by pressure and an operating pressure. Thus, when the supply of a high-pressure gas to be treated is started to increase the pressure of the separation membrane module to an operating pressure, an abrupt decrease in temperature of the gas to be treated can be suppressed.

The invention relates to a method for membrane permeation of a gas flow including methane and carbon dioxide, wherein said gas flow is cooled to a temperature of 0° C. to −60° C. before being fed into a membrane separation unit.

Membrane-based method of washing and deacidification of oils, wherein a stream of oil is conveyed from an oil reservoir along one side of porous hydrophobic membrane, and washing aqueous solution is conveyed along another side of this membrane. The membranes form hollow fibers, and their total surface area and porosity are large enough for efficient removal of fatty acids, water, ions and hydrophilic organic impurities from oil. Membrane pore size is small enough, so that hydrodynamic mixing of oil and aqueous solution does not take place. Additional stabilization of oil/water meniscus in the pores is achieved by transmembrane pressure difference.

Disclosed is a method for removing hydrogen sulfide from natural gas. The method includes passing a natural gas feed including methane and hydrogen sulfide (H2S) through a membrane at normal operating conditions. The membrane is an asymmetric hollow fiber membrane or an asymmetric film composite membrane including a porous layer and a nonporous skin layer. The asymmetric hollow fiber membrane or the nonporous skin layer of the asymmetric film composite membrane plasticizes during the method by exposure to condensable gases with high critical temperature under the operating conditions. The membrane preferentially removes H2S over methane from the natural gas feed at a H2S/methane selectivity of from 7 to 40 when measured at 35° C. and 45 bar.

Methods of reducing acid gas from a stream, comprising contacting the stream with a solvent system comprising a glycerol derivative are described herein. Disclosed herein is a composition comprising a glycerol derivative and an acid gas. A method for sweetening a natural gas stream comprising contacting a solvent system comprising a glycerol derivative with a natural gas stream is described herein.

Disclosed herein is a composite hollow fiber polymer membrane including a porous core layer and a selective sheath layer. The porous core layer includes a polyamide-imide polymer, or a polyetherimide polymer, and the selective sheath layer includes a polyimide polymer, which is prepared from monomers A, B, and C. The monomer A is a dianhydride of the formula ##STR00001##
wherein X.sub.1 and X.sub.2 are independently halogenated alkyl group, phenyl or halogen and R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are independently H, alkyl, or halogen. The monomer B is a diamino cyclic compound without a carboxylic acid functionality and the monomer C is a diamino cyclic compound with a carboxylic acid functionality. The polyimide polymer further includes covalent ester crosslinks. Also disclosed herein is a method of making the composite polymer membrane and a process for purifying natural gas utilizing the composite polymer membrane.

The present invention relates to a method of controlling a gas separation plant, to a plant thus controlled and also to its use for separation of gas mixtures, especially in the processing of biogas or natural gas, or syngas.

An integrated plant to generate chemical grade syngas from a steam biomass reforming in a multiple stage bio reforming reactor for use with either a high temperature or low temperature Fischer-Tropsch synthesis process to produce fuel from biomass is discussed. The first stage has a reactor to cause a chemical devolatilization of a biomass feedstock from the biomass feedstock supply lines into its constituent gases of CO, H2, CO2, CH4, tars, chars, and other components into a raw syngas mixture. A second stage performs further reforming of the raw syngas from the first stage into the chemical grade syngas by further applying heat and pressure to chemically crack at least the tars, reform the CH4, or a combination of both, into their corresponding syngas molecules. The second stage feeds the chemical grade syngas derived from the biomass feedstock to the downstream Fischer-Tropsch train to produce the fuel from the biomass. One or more recycle loops supply tail gas or FT product back into the plant.