In a method for compressing a gas that is to be separated in a low-temperature CO.sub.2 separation unit using at least one partial condensation step and/or at least one distillation step, the gas that is to be separated has a variable composition and/or variable flow rate, the gas that is to be separated is compressed in a compressor to produce a compressed gas and the inlet pressure of the gas that is to be separated, entering the compressor, is modified according to the CO.sub.2 content and/or the flow rate of the gas that is to be separated so as to reduce the variations in volumetric flow rate of the gas that is to be separated entering the compressor.

The invention relates to mixtures comprising molecular hydrogen, hydrocarbons, and nitrogen oxides; to processes for removing at least a portion of the nitrogen oxides therefrom; to equipment useful in such processes; and to the use of such hydrocarbons for, e.g., chemical manufacturing.

Processes and systems for recovering hydrogen may include feeding a gas stream, comprising hydrogen and additional gases, to a pressure swing adsorption (PSA) system and feeding a membrane permeate stream comprising hydrogen to the PSA system. In the PSA system, a portion of the hydrogen may be separated from the additional gases to recover a hydrogen product stream and a PSA tail gas stream comprising unseparated hydrogen and the additional gases. The PSA tail gas stream may be fed to a membrane separation unit for separating hydrogen from the additional gases and to recover (i) the membrane permeate stream comprising hydrogen fed to the PSA system and (ii) a membrane tail gas stream comprising the additional gases. Embodiments herein may additionally include a refrigeration system for partially condensing one or both of the feed gas stream and the PSA tail gas stream, enhancing the efficiency of the membrane separation unit.

Plant and process for the production of liquid methane from a feed gas stream comprising at least methane and carbon dioxide. A feed gas stream is injected into a CO.sub.2 crystallizer in countercurrent fashion against a stream of predominantly liquid methane, thereby crystallizing amounts of carbon dioxide from the feed gas stream. Gaseous methane recovered from the CO.sub.2 crystallizer is liquefied at a liquefaction exchanger.

Plant and process for the production of liquid methane from a feed gas stream comprising at least methane and carbon dioxide. A feed gas stream is injected into a CO.sub.2 crystallizer in countercurrent fashion against a stream of predominantly liquid methane, thereby crystallizing amounts of carbon dioxide from the feed gas stream. Gaseous methane recovered from the CO.sub.2 crystallizer is liquefied at a liquefaction exchanger.

In a method for compressing a gas that is to be separated in a low-temperature CO.sub.2 separation unit using at least one partial condensation step and/or at least one distillation step, the gas that is to be separated has a variable composition and/or variable flow rate, the gas that is to be separated is compressed in a compressor to produce a compressed gas and the inlet pressure of the gas that is to be separated, entering the compressor, is modified according to the CO.sub.2 content and/or the flow rate of the gas that is to be separated so as to reduce the variations in volumetric flow rate of the gas that is to be separated entering the compressor.

The present invention relates to a method for production of H.sub.2 from natural gas, solid fossil fuels or biomass. The method comprises the following steps: reacting natural gas in a reformer or reacting solid fossil fuels or biomass in a gasifier to form syngas, reacting the syngas to form a shifted gas mixture, comprising H.sub.2 and CO.sub.2, in a water-gas-shift (WGS) section, separating the shifted gas mixture into a H.sub.2 gas and a H.sub.2 depleted tail gas mixture or retentate gas mixture in a H.sub.2 separation unit, separating the H.sub.2-depleted tail gas mixture or retentate gas mixture into a CO.sub.2 liquid and a CO.sub.2-depleted tail gas mixture in a CO.sub.2 capture and liquefaction unit, and recycling the CO.sub.2-depleted tail gas mixture from the CO.sub.2 capture and liquefaction unit without recompression to the WGS section and to the reformer or the gasifier. The CO.sub.2-depleted tail gas mixture is at a pressure in the range from 25 to 120 bar when recycled to the WGS section and to the reformer or the gasifier.

An air-sparged hydrocyclone for separating a vapor from a carrier gas is disclosed. The cyclone comprises a porous sparger covered by an outer gas plenum. A cryogenic liquid is injected to a tangential feed inlet at a velocity that induces a tangential flow and a cyclone vortex in the air-sparged hydrocyclone. The carrier gas is injected into the cyclone through the porous sparger. The vapor dissolves, condenses, desublimates, or a combination thereof, forming a vapor-depleted carrier gas and a vapor-enriched cryogenic liquid. The vapor-depleted carrier gas is drawn through a vortex finder and the vapor-enriched cryogenic liquid is drawn through an apex nozzle outlet. In this manner, the vapor is removed from the carrier gas.

The invention relates to a method for treating a mixture in order to separate carbon dioxide and hydrogen from said mixture, in which: i) the mixture is cooled and partially condensed and a first liquid is separated from the rest of the mixture in a first phase separator; ii) a gas from or derived from a gas from the first phase separator is treated in a hydrogen pressure swing adsorption module in order to produce a hydrogen-rich gas and a hydrogen-depleted residual gas; and iii) said hydrogen-depleted residual gas or a gas derived from said depleted gas is cooled and partially condensed and a second liquid is separated from the remaining gas in a second phase separator, separate from the first phase separator, wherein the first and/or second liquid being rich in carbon dioxide. The invention also relates to an installation for implementing such a method.

A hydrocyclone for separating a vapor from a carrier gas is disclosed. The hydrocyclone comprises one or more nozzles. A cryogenic liquid is injected to a tangential feed inlet at a velocity that induces a tangential flow and a cyclone vortex in the hydrocyclone. The carrier gas is injected into the cryogenic liquid, causing the vapor to dissolve, condense, desublimate, or a combination thereof, forming a vapor-depleted carrier gas and a vapor-enriched cryogenic liquid. The vapor-depleted carrier gas is drawn through a vortex finder and the vapor-enriched cryogenic liquid is drawn through an apex nozzle outlet. In this manner, the vapor is removed from the carrier gas.