An apparatus for producing dry ice includes a supply means (2) for supplying carbon dioxide in the liquid state and a means (20) for the transition of state of the carbon dioxide in the liquid state flowing along the supply means (2). The state transition means (20) brings about the desired solidification of the carbon dioxide in order to produce dry ice and the undesired formation of carbon dioxide in the gaseous state. A system (3) is provided for the collection and recovery of carbon dioxide in the gaseous state. The collection and recovery system (3) collects carbon dioxide in the gaseous state downstream of the state transition means (20) and has a compressor (4) for compressing the carbon dioxide collected by the collection system (3), a heat exchanger (5) that places the carbon dioxide downstream of the compressor (4) and the carbon dioxide upstream of the compressor (4) in thermal communication, and a storage means (6) for storing the carbon dioxide coming from the compressor (4).

Systems and methods are provided for recovering helium from a feed comprising helium, carbon dioxide, and at least one of nitrogen and methane. The feed is separated in a first separator to form helium-enriched stream and a CO.sub.2-enriched stream. The helium-enriched stream is separated in a pressure swing adsorption unit to form a helium-rich product stream and a helium-lean stream. At least a portion of the helium-lean stream is recycled to the first separator with the feed. In some embodiments, a membrane separation unit is used to enhance helium recovery.

The invention relates to the field of power engineering. The technical result consists in a reduction in the amount of energy expended on compressing and liquefying gas, and a simplification of the design of the apparatus. A gaseous medium to be compressed in a pressure exchanger by the action thereon of a gaseous compression medium having a higher pressure and temperature. A portion of the compression medium is pre-compressed to the necessary pressure in a compressor, or, after cooling and condensation, is pressurized by a pump, after which it is heated and evaporated, or gasified, and used as a compression medium. In the case that a compressor is used, the portion of compression medium is drawn off from the high-pressure gaseous medium compressed in the pressure exchanger and is fed by circulating fan or a compressor to a heater and used as a compression medium in the pressure exchanger.

The invention relates to a method for the low-temperature separation of a gas containing CO.sub.2 in order to produce a CO.sub.2-rich fluid, in which method a gas containing CO.sub.2 and at least one component lighter than CO.sub.2 is compressed in a compressor comprising at least two stages, the gas being cooled downstream of at least one of the stages in a cooler and by exchanging heat with air and then being cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature by partial condensation and/or distillation in order to produce a fluid rich in CO.sub.2 and depleted in the component lighter than CO.sub.2 and a gas depleted in CO.sub.2 and enriched in the component lighter than CO.sub.2. The gas depleted in CO.sub.2 is first heated in the first heat exchanger and then in the cooler before being expanded in a turbine.

The invention relates to a method for the low-temperature separation of a feed gas containing CO.sub.2, at least one component lighter than CO.sub.2 and at least one component heavier than CO.sub.2, wherein, in order to produce a CO.sub.2-rich fluid, the feed gas is compressed, the compressed gas being cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature in a first distillation column to produce a liquid that is enriched in CO.sub.2 and depleted in the at least one component lighter than CO.sub.2 and a gas that is depleted in CO.sub.2 and enriched in the at least one component lighter than CO.sub.2, the gas depleted in CO.sub.2 is heated in the first heat exchanger, a first part of the liquid enriched in CO.sub.2 is expanded and sent to a second distillation column in liquid form, a second part of the liquid enriched in CO.sub.2 is vaporized in the first heat exchanger then sent in gas form into the tank of the second distillation column, a liquid depleted in CO.sub.2 and enriched in the at least one heavier component is withdrawn from the second column, and a gas enriched in CO.sub.2 and depleted in the at least one heavier component is withdrawn at the top of the second column as product.

The present invention relates to an apparatus for transferring a fluid, particularly CO.sub.2, from a subcritical gaseous state into a supercritical state, the apparatus comprising a compressor unit, a pump unit, a drive unit and a liquefaction unit, wherein the compressor unit and the pump unit are commonly driven by the drive unit, and wherein the liquefaction unit is provided downstream of the compressor unit and upstream of the pump unit, wherein the compressor unit is configured to compress the fluid from a first subcritical gaseous state to a first predetermined pressure level of a second subcritical gaseous state, wherein the liquefaction unit is configured to reduce the temperature of the compressed fluid in the second subcritical state downstream of the compressor unit to a predetermined temperature level such that the fluid is transferred from the second subcritical gaseous state to a liquid state.

An apparatus for separation of a flow containing at least 95 mol % of carbon dioxide and also at least one impurity lighter than carbon dioxide by distillation comprises a heat exchanger (20), a distillation column (30), expansion means (V3), means for sending the flow to be cooled in the heat exchanger, means for sending the cooled flow to be separated in the distillation column, means for withdrawing at the bottom of the column a liquid flow containing at least 99 mol % of carbon dioxide, means for sending at least a portion (12) of the liquid flow to be cooled in the heat exchanger to form a subcooled liquid (3), means for sending at least a portion of the subcooled liquid to the expansion means to produce a two-phase flow, a phase separator (40) for separating the two-phase flow to form a gas and a liquid, means for sending at least a portion (14) of the liquid from the phase separator to be vaporized in the heat exchanger and means for taking a portion (4) of the liquid from the phase separator.

Processes and systems are provided for treating the tail gas stream of a sulfur recovery plant. The process comprising the steps of treating the compressed tail gas stream in a pre-treatment unit to remove the impurities; separating the dry stream in a first stage membrane unit, the first stage membrane unit comprises a membrane selective to carbon dioxide and hydrogen; reducing a temperature of the cryogenic feed in a cryogenic cooler to produce a cryogenic stream; separating the cryogenic feed in a knock-drum to produce a liquid carbon dioxide and membrane feed; separating the membrane feed in a second stage membrane unit to produce a rubbery membrane permeate and a rubbery membrane retentate, where the second stage membrane unit comprises a membrane selective to carbon dioxide over hydrogen; and treating the rubbery membrane retentate in a hydrogen recovery process to produce a hydrogen product stream and a carbon dioxide lean stream.