An air separation device can include: a first compressor and a second compressor for compressing feed air; a first refrigerator and a second refrigerator for cooling the feed air; a pre-purification unit for pre-purifying the feed air; a flow rate measuring unit for measuring the flow rate of the feed air; a main heat exchanger for subjecting the feed air to heat exchange; a purification portion into which the feed air led out from the main heat exchanger is fed, and which separates and purifies product nitrogen and/or product oxygen from the feed air; and a compressor control unit for controlling the feed quantity of the feed air in accordance with an increase or decrease in the production quantity of product nitrogen and/or product oxygen.

The ammonia production plant includes a feed gas compression section, a process air compression section, a syngas compression section and a refrigerant compression section. At least two of these compression sections are combined together forming a combined compression train driven by a single driver.

Contemplated plants for flexible ethane recovery and rejection by allowing to switch the top reflux to the demethanizer from residue gas to the deethanizer overhead product and by controlling the flow ratio of feed gas to two different feed gas exchangers. Moreover, the pressure of the demethanizer is adjusted relative to the deethanizer pressure for control of the ethane recovery and rejection.

The method and the device arc used for the cryogenic decomposition of air in a distillation column system for separating nitrogen and oxygen, said system having a first high-pressure column (23), a low-pressure column (25, 26), and three condenser-evaporators, namely a high-pressure column head condenser (27), a low-pressure column bottom evaporator (28), and an auxiliary condenser (29; 228).

Selective recovery of C2 to C4 hydrocarbons is achieved through the use of a converging-diverging nozzle, or de Laval nozzle. The vapor stream comprising C2 to C4 hydrocarbons is fed into an inlet of a de Laval nozzle having a throat. The vapor stream may have an initial temperature of between 0 C. and 100 C., and an initial pressure of between 200 psig and 500 psig. In the de Laval nozzle, the vapor stream expands after passing through the throat of the de Laval nozzle, producing a vapor stream having reduced temperature and pressure. Then, C2 to C4 hydrocarbons condense from the reduced-temperature vapor stream as liquid droplets, which may be recovered. Fractionation of C2 to C4 hydrocarbons by means of a de Laval nozzle is possible; the technique allows selective recovery of a stream enriched in propene from a mixture of propane and propene.

Systems and methods of CO.sub.2 desublimation are presented in which refrigeration content is retained within the system. Most preferably, refrigeration content is recycled by providing the refrigeration content of a CO.sub.2-lean feed gas to the CO.sub.2-containing feed gas and to pre-cooling of a desublimator, and/or by providing refrigeration of effluent of a desublimator in regeneration to a refrigerant in a closed refrigeration cycle for deep-cooling of another desublimator.

A method and a system for feeding a feed gas including methane (CH.sub.4) and carbon dioxide (CO.sub.2) to a cryogenic distillation column are provided herein. The method includes flowing a freeze zone CO.sub.2 vapor stream into a freezing section of the column to produce an overhead stream that exits the column. The method includes heating the overhead stream via a heating component to reduce or prevent solidification of the CO.sub.2 in the overhead stream.

Processes and systems for recovery of a dilute ethylene stream are illustrated and described. More specifically, embodiments disclosed herein relate to processes and systems for separation of a dilute ethylene stream from an offgas or other vapor streams, where the ultra-low temperature refrigeration for the desired separations is provided by the offgas itself, and only moderately-low temperature externally supplied propylene refrigerants (for example, at 40 C. to 15 C.) are necessary.

Helium-containing natural gas is processed with three gas separation stages to produce a natural gas product and a Helium-containing gas that may be injected into the reservoir from which the Helium-containing natural gas is obtained. A permeate from the first gas separation membrane stage is compressed and fed to the second gas membrane stage. The permeate from the second gas separation membrane stage is recovered as the Helium-containing gas that may be injected into the reservoir. The non-permeate from the second gas separation membrane stage is fed to the third gas separation membrane stage. The non-permeate from the first gas separation stage is a natural gas product. A permeate from the third gas separation membrane stage is combined with a non-permeate from the first gas separation membrane stage before it is compressed and fed to the second gas separation membrane stage. A non-permeate from the third gas separation membrane stage is fed to the first gas separation membrane stage along with the Helium-containing natural gas.

Helium-containing natural gas is processed with three gas separation stages to produce a natural gas product and a Helium-containing gas that may be injected into the reservoir from which the Helium-containing natural gas is obtained. A permeate from the first gas separation membrane stage is compressed and fed to the second gas membrane stage. The permeate from the second gas separation membrane stage is recovered as the Helium-containing gas that may be injected into the reservoir. The non-permeate from the second gas separation membrane stage is fed to the third gas separation membrane stage. The non-permeate from the first gas separation stage is a natural gas product. A permeate from the third gas separation membrane stage is combined with a non-permeate from the first gas separation membrane stage before it is compressed and fed to the second gas separation membrane stage. A non-permeate from the third gas separation membrane stage is fed to the first gas separation membrane stage along with the Helium-containing natural gas.