The method for reducing or removing non-volatile impurities in a high-purity oxygen liquid comprises: an oxygen vaporization step for vaporizing a high-purity oxygen liquid obtained from a high-purity oxygen rectification column in an air separation unit for producing the high-purity oxygen liquid; and an oxygen recondensing step for recondensing oxygen gas vaporized in the oxygen vaporization step. This method may also comprise a high-purity oxygen liquid extraction step for extracting a condensate obtained in the oxygen recondensing step.

A batch process for producing a purified, pressurized liquid carbon dioxide stream, includes withdrawing a liquid carbon dioxide stream (A) from a liquid carbon dioxide supply (10); introducing the liquid carbon dioxide stream (A) into a distillation column (B) having packing (C) therein, and stripping volatile impurities from the liquid carbon dioxide stream with the packing; vaporizing the liquid carbon dioxide stream (A) in a sump (D) of the distillation column (B) for providing a carbon dioxide vapor; withdrawing from a vaporized portion (F) of carbon dioxide vapor in the sump (D) a first vapor stream (G) vented from the distillation column (B); withdrawing from the vaporized portion (F) of the carbon dioxide vapor in the sump (D) a second vapor portion (H) vented from the sump into a conduit (I); and introducing the second vapor portion (H) in the conduit (I) into a carbon dioxide vapor feed stream.

Methods and systems for recovering alkene (e.g., C.sub.2-C.sub.4 alkene) gas as well as producing pressurized alkene (e.g., C.sub.2-C.sub.4 alkene) gas from process gas streams including higher concentrations of alkenes are provided herein.

Methods and systems for recovering alkenes (e.g. ethylene, propylene) from process gas streams, including multi-step condensing of the process gas stream, are provided herein.

Methods and systems for recovering alkene (e.g., C.sub.2-C.sub.4 alkene) gas as well as producing pressurized alkene (e.g., C.sub.2-C.sub.4 alkene) gas from process gas streams including lower concentrations of alkenes are provided herein.

An apparatus is provided for maintaining a steady flow rate and pressure of a carbon dioxide stream at high pressure when a low-pressure source of the carbon dioxide varies with time. Liquid level in an accumulator that is sized to accommodate variations in supply rate is controlled by sub-cooling of liquid entering the accumulator and heating in the accumulator, the sub-cooling and heating being controlled by a pressure controller operable in the accumulator.

The extrusion device of a solid film comprises a cell provided with an input opening of a material designed to form the solid film, and an output opening of the solid film from the cell. The device comprises a first heat exchanger for applying a first temperature to the output opening and a second heat exchanger for applying a second temperature in a first zone of the cell distinct from the output opening and a control circuit imposing first and second sets of first and second temperatures. The first set enables a volume of the material in solid phase to be formed. The second set enables a temperature gradient to be generated in the volume so as to generate a pressure forcing extrusion of the solid film via the output opening.

Underwater gas pressurization units and liquefaction systems, as well as pressurization and liquefaction methods are provided. Gas is compressed hydraulically by a rising pressurization liquid that is separated from the gas by a water immiscible liquid layer on top of an aqueous salt solution. Tall vessels are used to reach a high compression ratio that lowers the liquefaction temperature. The pressurizing liquid is delivered gravitationally, after gasification, transport to smaller water depths and condensation. Cooling units are used to liquefy the compressed gas. A cascade of compression and cooling units may be used with sequentially higher liquefaction temperatures, which allow eventual cooling by sea water. The pressurizing liquid, dimensions of the vessels, the delivery unit, the coolants and the implementation of the cooling units are selected according to the sea location, to enable natural gas liquefaction in proximity to the gas source.

Underwater gas pressurization units and liquefaction systems, as well as pressurization and liquefaction methods and gas field development methods are provided. Gas is compressed hydraulically by seawater introduced into vessels and separated from the gas by a water immiscible liquid layer. Tall, possibly vertical helical vessels are used to reach a high compression ratio that lowers the liquefaction temperature. Cooling units are used to liquefy the compressed gas, possibly by a coolant which is itself pressurized by a similar mechanism. The coolant may be selected to be liquefied under surrounding seawater temperatures. The seawater which is used to pressurize the gas may be used after evacuation from the vessels to pressurize intrastratal gas in the production stages and broaden the gas field development.

A method for pressurizing a liquid exiting a phase separator includes opening an inlet control valve, thereby providing a two-phase fluid stream to a phase separator and producing a vapor stream and a liquid stream. Wherein a first liquid control valve prevents the liquid stream from leaving the phase separator. Then closing the inlet control valve and opening the first liquid control valve, thereby withdrawing the liquid stream from the phase separator and introducing the liquid stream into a lock hopper. Wherein, a second liquid control valve prevents the liquid stream from leaving the lock hopper. Then closing the first liquid control valve and then opening a pressurized vapor control valve, thereby providing a pressurized vapor stream to the lock hopper, thereby pressurizing the lock hopper. Then closing the pressurized vapor control valve, and opening the second liquid control valve, thereby withdrawing a pressurized liquid stream from the lock hopper.