An acid gas purification system is described herein that includes a primary membrane system with a CO.sub.2- and H.sub.2S-enriched permeate stream effluent and a hydrocarbon stream effluent; a first compression stage arranged to receive the CO.sub.2- and H.sub.2S-enriched permeate stream and produce a compressed stream; and a cryogenic separation system to receive the compressed stream, the cryogenic separation system including a cooler followed by a fractionator, wherein the fractionator produces a CO.sub.2- and H.sub.2S liquid stream and a hydrocarbon gas stream.

The present invention is directed to a method, device and system to efficiently liquefy and isolate a gas from a gaseous mixture. In an embodiment of the present invention, separation of gasses from the atmosphere can be carried out using a cooled surface to separate the gasses from the atmosphere. In an alternative embodiment of the present invention, removal of CO.sub.2 from the atmosphere can be carried out by using the method, device and system to efficiently cryogenically separate CO.sub.2 from air and capture the CO.sub.2 from a gaseous mixture using a surface and release the CO.sub.2 lean air into the atmosphere and store the captured liquefied CO.sub.2.

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.

A molten carbonate fuel cell-powered system for capturing carbon dioxide produced by a steam methane reformer system. Tail gas from a pressure swing adsorption system is mixed with exhaust gas from the fuel cell anode, then pressurized and cooled to extract liquefied carbon dioxide. The residual low-CO.sub.2 gas is directed to an anode gas oxidizer, to the anode, to the reformer to be burned for fuel, and/or to the pressure swing adsorption system. Low-CO.sub.2 flue gas from the reformer can be vented to the atmosphere or directed to the anode gas oxidizer. Reduction in the amount of CO.sub.2 reaching the fuel cell allows the fuel cell to be sized according to the power demands of the system and eliminates the need to export additional power output.

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.

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.

A natural-gas purification apparatus includes: a plurality of carbon-dioxide separation units that are arranged in series and separate carbon dioxide, through carbon-dioxide separation membranes, from natural gas pressurized by a compressor, cooled by a cooling unit to liquefy and separate a high-boiling-point hydrocarbon component, and heated by a heating unit; a gas supply pipe that is provided between the plurality of carbon-dioxide separation units through on-off valves and that supplies the natural gas; a compressor that is provided to the gas supply pipe; a cooling unit that liquefies and separates a high-boiling-point hydrocarbon component by cooling the natural gas pressurized by this compressor; and a heating unit that heats the natural gas after the separation of the high-boiling-point hydrocarbon component by this cooling unit.

In a process for separating at least one heavy impurity such as hydrogen sulfide from crude carbon dioxide comprising significant quantities of at least one light impurity such as non-condensable gases, involving at least one heat pump cycle using carbon dioxide-containing fluid from the process as the working fluid, the light impurity is removed from the crude carbon dioxide and carbon dioxide is subsequently recovered from the removed light impurity, thereby improving overall carbon dioxide recovery and efficiency in terms of energy consumption.

A method of capturing carbon dioxide from a steam methane reformer system includes mixing tail gas from the steam methane reformer system with anode exhaust gas from an anode of a molten carbonate fuel cell to form a gas mixture, compressing the gas mixture, cooling the gas mixture, and separating the gas mixture into liquid carbon dioxide and a residual gas mixture.