A process and apparatus for producing a hydrogen-enriched product and recovering CO.sub.2 from an effluent stream from a hydrogen production unit are described. The effluent from the hydrogen production unit, which comprises a mixture of gases comprising hydrogen, carbon dioxide, water, and at least one of methane, carbon monoxide, nitrogen, and argon, is sent to a PSA system that produces at least two product streams for separation. The PSA system that produces at least two product streams separates the gas mixture into a high-pressure hydrogen stream enriched in hydrogen, optionally a second gas stream containing the majority of the impurities, and a low-pressure tail gas stream enriched in CO.sub.2 and some impurities. The CO.sub.2-rich tail gas stream is compressed and sent to a CO.sub.2 recovery unit, where a CO.sub.2-enriched stream is recovered. The CO.sub.2-depleted overhead gas stream is recycled to the PSA system that produces at least two product streams.

A bio-renewable conversion process for making fuel from bio-renewable feedstocks is combined with a hydrogen production process that includes recovery of CO.sub.2. The integrated process uses a purge gas stream comprising hydrogen from the bio-renewable hydrocarbon production process in the hydrogen production process.

A liquefaction system that is configured to use a single methane expander to provide primary refrigeration duty. The liquefaction system can include a first or main heat exchanger and a fluid circuit coupled with the heat exchanger, the fluid circuit configured to circulate a process stream derived from an incoming feedstock of natural gas. The fluid circuit can comprise a compression circuit, methane expander coupled with the compression circuit and the main heat exchanger, a sub-cooling unit coupled with the methane expander, the sub-cooling unit configured to form a liquid natural gas (LNG) product from the process stream, and a first throttling device interposed between the main heat exchanger and the sub-cooling unit. The first throttling device can be configured to expand the process stream to a process pressure that corresponds with the suction pressure internal to the compression circuit.

A method and apparatus for liquefying a natural gas feed stream and removing nitrogen therefrom to produce a nitrogen-depleted LNG product, in which a natural gas feed stream is passed through main heat exchanger to produce a first LNG stream, which is separated to form a nitrogen-depleted LNG product and a recycle stream composed of nitrogen-enriched natural gas vapor, and in which the recycle stream is passed through main heat exchanger to produce a first LNG stream, separately from and in parallel with the natural gas feed stream, to produce a first at least partially liquefied nitrogen-enriched natural gas stream that is separated to provide a nitrogen-rich vapor product.

A process for separating carbon dioxide from a fluid containing carbon dioxide, NO.sub.2, and at least one of oxygen, argon, and nitrogen comprises the steps of separating at least part of the fluid into a carbon dioxide enriched stream, a carbon dioxide depleted stream comprising CO.sub.2 and at least one of oxygen, argon, and nitrogen and a NO.sub.2 enriched stream and recycling said NO.sub.2 enriched stream upstream of the separation step.

Compressed rich natural gas is divided into a cooling gas stream and a fuel gas stream. The cooling gas stream is depressurized. The cooling gas and the fuel gas are then heat exchanged to provide a first cooling step to the fuel gas. The cooled fuel gas continues into a second cooling step in a second heat exchanger, and then flows into a separator vessel where liquids are removed from the bottom of the separator and conditioned fuel gas exits the top of the separator. The conditioned fuel gas from the separator and produced from its influent is depressurized and heat exchanged to provide the second cooling fluid for the second heat exchanger.

Described herein are methods and systems for liquefying natural gas using an open-loop natural gas refrigeration cycle; coil wound heat exchanger units suitable for cooling one or more feed streams, such as for example one or more natural gas feed streams, via indirect heat exchange with a gaseous refrigerant; and methods and systems for removing heavy components from a natural gas prior to liquefying the natural gas using an open-loop natural gas refrigeration cycle.

In a method for separating a mixture containing carbon dioxide, the mixture is cooled in a heat exchanger and partially condensed and a first liquid is separated from the mixture in a first system operating at low temperature comprising at least one first phase separator and a gas from the first system is treated in a membrane system to produce a permeate and a non-permeate, the gas from the first system being divided into two portions, a first portion being sent to the membrane system without being heated and a second portion being heated to at least an intermediate temperature of the heat exchanger and then sent to the membrane system without being cooled.

Provided are an apparatus and method for liquefying natural gas. The apparatus for liquefying natural gas includes a gas compressor configured to receive and compress the natural gas from a natural gas feed stream, a heat exchanging unit configured to cool a high-pressure natural gas passing through the gas compressor through heat exchange, an expansion valve configured to expand the cooled natural gas passing through the heat exchanging unit, a hold-up drum configured to phase-separate a gas-liquid mixture produced by passing through the expansion valve and divide the gas-liquid mixture into a liquefied natural gas and a cryogenic recycle gas having nitrogen content greater than that of the liquefied natural gas so as to discharge the liquefied natural gas and the cryogenic recycle gas, and a bypass line configured to provide the recycle gas discharged from the hold-up drum to the heat exchanging unit.

The invention relates to a refrigeration system that in mode 1 prepares a reservoir of cooled refrigerant before flowing unconditioned gas through the system, and in mode 2, continuously cools feed gas with the prepared refrigerant inventory, extracting natural gas liquids (NGLs) comprising predominantly ethane, propane, butane, and condensate and controlled by a control system without needing ramp up time.