The present disclosure relates to systems and methods that provide a low pressure liquid CO.sub.2 stream. In particular, the present disclosure provides systems and methods wherein a high pressure CO.sub.2 stream, such as a recycle CO.sub.2 stream from a power production process using predominately CO.sub.2 as a working fluid, can be divided such that a portion thereof can be expanded and used as a cooling stream in a heat exchanger to cool the remaining portion of the high pressure CO.sub.2 stream, which can then be expanded to form a low pressure CO.sub.2 stream, which may be in a mixed form with CO.sub.2 vapor. The systems and methods can be utilized to provide net CO.sub.2 from combustion in a liquid form that is easily transportable.

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 present disclosure relates to systems and methods useful for providing one or more chemical compounds in a substantially pure form. In particular, the systems and methods can be configured for separation of carbon dioxide from a process stream, such as a process stream in a hydrogen production system. As such, the present disclosure can provide systems and method for production of hydrogen and/or carbon dioxide.

A cryogenic method for capturing carbon dioxide in the gaseous emissions produced from the fossil-energy combustion of solid, liquid, or gaseous fossil fuels in a power generation installation employing an OxyFuel mode of combustion. The method includes: producing essentially pure carbon dioxide under elevated pressure and at near ambient temperatures in a Carbon-Dioxide Capture Component from the carbon-dioxide content of at least a part of the gaseous emissions produced from fossil-energy fueled combustion in the Oxyfuel mode of combustion; separating atmospheric air in an Air Separation Component into a stream of liquid nitrogen and a stream of high-purity oxygen; supplying low temperature, compressed purified air to a cryogenic air separation unit (cold box) within the Air Separation Component; collecting low temperature thermal energy from coolers employed within the Carbon-Dioxide Capture Component and the Air Separation Component; and converting the collected thermal energy to electricity within a Thermal-Energy Conversion Component.

A CO.sub.2 energy storage system includes a storage tank that stores a CO.sub.2 slurry, including dry ice and liquid CO.sub.2, at CO.sub.2 triple point temperature and pressure conditions. The storage system also includes a first pump coupled in flow communication with the storage tank. The first pump is configured to receive the CO.sub.2 slurry from the storage tank and to increase a pressure of the CO.sub.2 slurry to a pressure above the CO.sub.2 triple point pressure. The energy storage system further includes a contactor coupled in flow communication with the first pump. The contactor is configured to receive the high pressure CO.sub.2 slurry from the pump and to receive a first flow of gaseous CO.sub.2 at a pressure above the CO.sub.2 triple point pressure. The gaseous CO.sub.2 is contacted and then condensed by the melting dry ice in the slurry to generate liquid CO.sub.2

A method is provided for separating off acid gases, in particular CO.sub.2 and H.sub.2S, from a hydrocarbon-rich fraction, in particular natural gas. The hydrocarbon-rich fraction is cooled and partially condensed. The resultant CO.sub.2-enriched liquid fraction is separated by rectification into a CO.sub.2-rich liquid fraction and a CO.sub.2-depleted gas fraction. The hydrocarbon-rich fraction is cooled close to the temperature of the CO.sub.2 triple point by means of a closed multistage refrigeration circuit. The refrigerant is a CO.sub.2 fraction of greater than 99.5% by volume. The rectification column is operated at a pressure between 40 and 65 bar. The reboiler of the rectification column is heated by means of a condensing refrigerant substream of the refrigeration circuit that is at a suitable pressure level.

In a method for cooling a flow containing at least 35% carbon dioxide and at least 0.2 ?g/Nm.sup.3 of mercury, the mercury being in liquid and/or gas form, the flow is cooled in a first brazed aluminum plate-fin heat exchanger from a first temperature to a second temperature higher than ?38.6? C. to form a cold flow at the second temperature, and the flow cooled to the second temperature is cooled in a second heat exchanger, which is a tube and shell heat exchanger, to a third temperature lower than ?38.6? C.

A refrigeration system for condensation of carbon dioxide (CO.sub.2) in a flue gas stream, the system includes a refrigeration circuit, a flue gas treatment system that includes a flue gas compressor, a flue gas adsorption drier, and a refrigeration system for condensation of CO.sub.2; and a method for condensation of CO.sub.2 in a flue gas stream using a circulating stream of an external refrigerant.

A process and an apparatus are disclosed for a compact processing assembly to remove carbon dioxide from a hydrocarbon gas stream. The gas stream is cooled, expanded to intermediate pressure, and fed to the top of a mass transfer means. A distillation liquid stream from the mass transfer means is heated in a first heat and mass transfer means to strip out its volatile components and form a bottom liquid product. A distillation vapor stream from the mass transfer means is combined with any vapor in the expanded cooled gas stream, and the combined vapor stream is cooled in a second heat and mass transfer means to partially condense it, forming a condensed stream that is fed to the top of the mass transfer means. A portion of the bottom liquid product is subcooled, expanded to lower pressure, and used to cool the combined vapor stream.

A method and a system for separating components is disclosed. A process liquid stream, containing a first component and a second component, is passed into an expansion device. The process liquid stream is expanded such that the first component and a first portion of the second component vaporize to form a process vapor stream and a second portion of the second component freezes to form a first solid product stream. The first solid product stream passes out of the expansion device. The process vapor stream passes into a direct-contact heat exchanger against a contact liquid stream. The first portion of the second component desublimates into the contact liquid stream as a second solid product stream. The contact liquid stream and the second solid product stream leave the direct-contact heat exchanger as a slurry stream. The process vapor stream leaves the direct-contact heat exchanger as a stripped process vapor stream.