A process for producing liquefied natural gas and liquid carbon dioxide from a natural gas feed gas comprising at least the following steps: Separation of a natural gas feed gas into a CO.sub.2-enriched gas stream and a natural gas stream; Cooling of said natural gas in a heat exchanger; Purification of the in step 1 from compounds containing at least six carbon atoms; At least partial condensation of said gas stream resulting from step 3 to form a two-phase stream; Separation of said two-phase stream resulting from step 4 to form a gas stream and a liquid stream; Condensation of the gas stream resulting from step 5 to form a liquefied gas containing less than 5 ppm by volume of compounds containing at least six carbon atoms; Liquefaction of the CO.sub.2-enriched gas stream resulting from step 1 with a portion of the liquid stream resulting from step 5.

In a process for distilling a gas mixture of CO2 and at least one component lighter than CO2, a partially purified liquid CO2 stream is withdrawn at an intermediate level of the distillation column at least one theoretical plate below the top of the distillation column and at least one theoretical plate above the bottom of the distillation column and the stream extracted at the intermediate level of the distillation column is vaporized by heat exchange with the gas mixture, with which it is then compressed.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

The carbon dioxide recovery apparatus has a dryer having a hygroscopic agent for drying a gas, and a separator for separating carbon dioxide from the gas dried by the dryer and discharging a residual gas from which carbon dioxide has been separated. The recovery apparatus further includes an introduction part for introducing a regeneration gas from outside for regenerating the hygroscopic agent, a regeneration system capable of supplying one of the regeneration gas introduced from the introduction part and the residual gas discharged from the separator to the dryer, and a switching mechanism for switching supply by the regeneration system between the regeneration gas and the residual gas in response to regeneration of the hygroscopic agent.

A device for separating a gas mixture containing at least 35 mol % carbon dioxide and also at least one gas lighter than carbon dioxide, comprising a first phase separator configured to receive a first partially condensed flow from an exchange line; a first phase separator configured to separate the gas phase from the liquid phase; a cooling means configured to receive the gas phase from the first phase separator and cool said gas phase to form a second partially condensed flow. The resulting liquid phase is then sent to a first valve and is expanded to a lower pressure that is at most 300 mbar lower in order to form a first expanded liquid, which is then mixed with a second liquid originating from the second phase separator in a mixing means that is located upstream of a third valve.

In this patent we disclose, for the first time, detailed methods of our newly invented state-of-the-art cryogenic technology for the cost effective energy efficient capture of each known component of entire emissions (nearly 100%) such as carbon dioxide (CO.sub.2), sulfur oxides (SO.sub.x), nitrogen oxides (NO.sub.x), carbon monoxide(CO), any other acid vapor, mercury, steam and unreacted nitrogen from industrial plants (coal and natural gas fired power plants, cement plants etc.), in a liquefied or frozen/solidified form, such that each of the components is captured separately and is industrially useful. This new technology includes a novel NH.sub.3 power plant to generate auxiliary electrical power from the heat energy of the flue gas to further improve the energy efficiency and cost effectiveness of the capture processes. It is the most cost effective of all existing emission capture technologies. It does not require use of any chemicals/reagents/external cryogens, unlike the current technologies. It uses only a fixed amount of water needed for the cooling process which can be used repeatedly. We present detailed methods of operations, together with scientific and economic analysis of the energy needed and cost involved for the said capture in two specific examples, and advantages of the new technology over the existing ones.

In a method for separating a flow containing at least 95 mol % of carbon dioxide and at least one impurity lighter than carbon dioxide by distillation, the flow is cooled to a first intermediate temperature between those of the cold end and the hot end of a heat exchange means in order to form a liquid flow at a first temperature and a first pressure and it is split into at least two to form a first fraction and a second fraction, the first fraction is expanded to the pressure of a distillation column, referred to as second pressure, which is lower than the first pressure, and it is sent to an intermediate level of the distillation column, the second fraction is cooled in the heat exchange means to the cold end thereof, it is expanded to the pressure of the distillation column and is sent to a level of the distillation column above the point of arrival of the first fraction, a liquid flow containing at least 99 mol % of carbon dioxide is withdrawn from the bottom of the column, and a fraction of the liquid flow is pressurized in a pump and sent to the top of the column.

In a purification method, a carbon dioxide-rich gas is cooled in a first brazed aluminum plate-fin heat exchanger, the cooled gas or at least one fluid derived from the cooled gas is sent to a purification step comprising a distillation step, the purification step produces a carbon dioxide-rich liquid which is cooled, then expanded, then sent to a second heat exchanger where it is heated by means of a fluid of the method, the exchanger carrying out an indirect heat exchange only between the carbon dioxide-rich liquid and the fluid of the method, the carbon dioxide-rich liquid at least partially vaporizes in the second exchanger and the vaporized gas formed heats up again in the first exchanger to form a carbon dioxide-rich gas.

A system for removing carbon dioxide from anode exhaust gas that has been compressed to form pressurized anode exhaust vapor includes a feed/effluent heat exchanger configured to cool the anode exhaust vapor to a first predetermined temperature and partially condense carbon dioxide in the anode exhaust vapor; a first vapor-liquid separator configured to receive an output of the feed/effluent heat exchanger and separate liquid carbon dioxide from uncondensed anode exhaust vapor; a feed/refrigerant heat exchanger configured to receive the uncondensed anode exhaust vapor from the first vapor-liquid separator, cool the uncondensed anode exhaust vapor to a second predetermined temperature, and condense carbon dioxide in the uncondensed anode exhaust vapor; a second vapor-liquid separator configured to receive an output of the feed/refrigerant heat exchanger and separate liquid carbon dioxide to form hydrogen rich, uncondensed anode exhaust vapor.

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.