The present invention is directed to a method and system of separating carbon monoxide from syngas mixtures with low methane content by cryogenic means where a partial condensation cycle is generally employed, and more specifically towards providing a methane slip stream to the feed in order to reduce the potential for any carbon dioxide entering the cold box to freeze, thereby preventing plugging of the cold box heat exchanger.

The invention relates to a method for separating a synthesis gas comprising hydrogen and carbon monoxide by cryogenic distillation, according to which the synthesis gas (1, 5) is cleaned and cooled to a cryogenic temperature, the cooled synthesis gas is separated by a first means (15) in order to produce a hydrogen-depleted liquid (33), the hydrogen-depleted liquid is introduced into the upper part of a stripping column (25) and a hydrogen-enriched gas (27) is drawn off at the head of the stripping column, at least partially condensed and sent back to the upper part of the stripping column.

A method and system for producing liquid air wherein liquid refrigerant is cycled between two core tanks maintained at a temperature sufficient to liquify compressed air passed through condensing tubing in the interior of the core tanks. Liquid refrigerant is cycled by alternating high pressure gas from a high pressure tank to one of the core tanks, which forces liquid refrigerant from this tank through an expansion device to expand a portion of the liquid refrigerant to absorb heat in the other core tank, the resulting refrigerant gas being driven into a low pressure tank. A compression device transfers the refrigerant gas from the low pressure tank to the high pressure tank and maintains the pressure in the high pressure tank. Connections between the low and high pressure tanks and the core tanks are reversed with each cycle.

In a process for separating a mixture containing carbon monoxide, hydrogen and carbon dioxide, the mixture cooled in a heat exchanger is contacted by a stream of liquid methanol at a temperature below 40 C. to produce carbon dioxide enriched methanol and a carbon dioxide depleted gas relative to the cooled mixture, the carbon dioxide depleted gas is cooled in the heat exchanger and is sent to a separation unit to produce a carbon monoxide enriched stream and a hydrogen enriched stream and the streams enriched in carbon monoxide and hydrogen are heated in the heat exchanger by exchanging heat with the mixture.

In a method for producing a gaseous mixture of CO and H.sub.2, a first gas comprising at least 50% CO is compressed in a first compressor to form a first compressed gas cooled to a first temperature and mixes with a second gas comprising at least 50% hydrogen in order to form the gaseous mixture, at least one of the first and second gases originating from a cryogenic distillation separation unit in which a feed gas containing H.sub.2 and CO cools in a first heat exchanger and is separated in at least one distillation column and at least one part of the second gas heats in the separation unit to a third temperature lower than the first temperature and is then sent to mix with the first gas.

In a method for separating a synthesis gas containing carbon monoxide and hydrogen, a synthesis gas flow from a synthesis gas source is compressed in a compressor and separated into at least three gaseous products. If there is insufficient synthesis gas, at least three separation products are recycled in the compressor in order to separate said products.

A method to recover hydrocarbonfractions from refineries gas streams involves a pre-cooled heat refinery fuel gas stream mixed with a pre-cooled and expanded supply of natural gas stream in an inline mixer to condense and recover at least C.sub.3.sup.+ fractions upstream of a fractionator. The temperature of the gas stream entering the fractionator may be monitored downstream of the in-line mixer. The pre-cooled stream of high pressure natural gas is sufficiently cooled by flowing through a gas expander that, when mixed with the pre-cooled refinery fuel gas, the resulting temperature causes condensation of heavier hydrocarbon fractions before entering the fractionator. A further cooled, pressure expanded natural gas reflux stream is temperature controlled to maintain fractionator overhead temperature. The fractionator bottoms temperature may be controlled by a circulating reboiler stream.

One or more specific embodiments disclosed herein includes a method for separating hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream, employing a single heat exchanger, multiple gas-liquid separators, multiple expander/compressor sets, and a rectifier attached to a liquid product drum.

Processes for separating CO.sub.2 from a gas mixture containing one or more of hydrogen, nitrogen, argon, CO, and methane or a combination thereof is described. The processes involve, for example, cooling and partial condensation of the gas mixture, preferably by a single loop refrigeration system with a mixed refrigerant, phase separation of the partially condensed stream, and distillation of the CO.sub.2-rich liquid stream. At least a portion of the liquid CO.sub.2 produced from the processes during the off-peak electricity demand hours can be stored and then heated, vaporized, further heated, and expanded for power generation during the peak electricity demand hours, helping balance the supply and demand of electricity of the electricity grid.

The invention relates to a process for the combined production of hydrogen and carbon dioxide from a hydrocarbon mixture, in which the residual gas of a PSA H.sub.2 (12) is separated by permeation in order to reduce the hydrocarbon content thereof and the hydrocarbon-purified gas is separated at a low temperature to produce a carbon dioxide-rich liquid (22).