The invention relates to a method for membrane permeation of a gas flow including methane and carbon dioxide, wherein said gas flow is cooled to a temperature of 0° C. to −60° C. before being fed into a membrane separation unit.

A method to pre-treat an inlet natural gas stream at gas pressure reduction stations to produce LNG removes water and carbon dioxide from a natural gas stream. The energy required for the process is provided by recovering pressure energy in the inlet gas stream. The process eliminates the conventional gas pre-heating process at pressure reductions stations employing gas combustion heaters. The process provides a method to produce LNG at natural gas pressure reduction that meets product specifications.

A technology liquefies natural gas. The natural gas liquefaction method pre-cools treated natural gas by ethane evaporation, sub-cools liquefied gas using cooled nitrogen as a refrigerant, reduces liquefied gas pressure, separates non-liquefied gas and diverts liquefied natural gas. Before pre-cooling the natural gas is compressed, ethane is evaporated during the multi-stage pre-cooling of liquefied gas with simultaneous evaporation of ethane using cooled ethane as a refrigerant. Ethane generated by evaporation is compressed, condensed and used as a refrigerant during the cooling of liquefied gas and nitrogen, with nitrogen being compressed, cooled, expanded and fed to the natural gas sub-cooling stage. The natural gas liquefaction unit contains a natural gas liquefaction circuit, an ethane circuit and a nitrogen circuit. The natural gas liquefaction circuit includes a natural gas compressor, a cooler unit, ethane vaporizers, a closed-end subcooling heat exchanger, and a separator, connected in series.

A technology liquefies natural gas. The natural gas liquefaction method pre-cools treated natural gas by ethane evaporation, sub-cools liquefied gas using cooled nitrogen as a refrigerant, reduces liquefied gas pressure, separates non-liquefied gas and diverts liquefied natural gas. Before pre-cooling the natural gas is compressed, ethane is evaporated during the multi-stage pre-cooling of liquefied gas with simultaneous evaporation of ethane using cooled ethane as a refrigerant. Ethane generated by evaporation is compressed, condensed and used as a refrigerant during the cooling of liquefied gas and nitrogen, with nitrogen being compressed, cooled, expanded and fed to the natural gas sub-cooling stage. The natural gas liquefaction unit contains a natural gas liquefaction circuit, an ethane circuit and a nitrogen circuit. The natural gas liquefaction circuit includes a natural gas compressor, a cooler unit, ethane vaporizers, a closed-end subcooling heat exchanger, and a separator, connected in series.

Embodiments relate generally to systems and methods for operating a natural gas liquids plant in ethane rejection and in ethane recovery. A natural gas liquid plant may comprise an absorber configured to produce an ethane rich bottom stream and an ethane depleted vapor stream; a stripper fluidly coupled to the absorber configured to, during ethane rejection, fractionate the ethane rich bottom stream from the absorber into an ethane overhead product and a propane plus hydrocarbons product, and configured to, during ethane recovery, fractionate the ethane rich bottom stream into an ethane plus NGL stream and an overhead vapor stream; and an exchanger configured to, during ethane recovery, counter-currently contact the ethane rich bottom stream from the absorber with the ethane depleted vapor stream from the absorber, thereby heating the vapor stream and chilling the ethane rich bottom stream before the ethane rich bottom stream is fed to the stripper.

A method of stripping carbon dioxide from a stream of natural gas to be used in the production of liquid natural gas (LNG) comprises the steps of: passing a stream of natural gas through a stripping column; injecting a stripping agent into the stripping column, the stripping agent stripping carbon dioxide from the stream of natural gas and exiting the stripping column as a liquid phase; passing the stripping agent exiting the stripping column through a regenerator column to generate a carbon dioxide gas stream and a recovered stripping agent stream; and cooling the recovered stripping agent stream using a cryogenic vapour generated in the production of LNG and injecting the cooled, recovered stripping agent stream into the stripping column as the stripping agent.

A method for producing liquefied natural gas (LNG) from a natural gas stream having a nitrogen concentration of greater than 1 mol %. At least one liquid nitrogen (LIN) stream is received at an LNG liquefaction facility. The LIN streams may be produced at a different geographic location from the LNG liquefaction facility. A natural gas stream is liquefied by indirect heat exchange with a nitrogen vent stream to form a pressurized LNG stream. The pressurized LNG stream has a nitrogen concentration of greater than 1 mol %. The pressurized LNG stream is directed to one or more stages of a column to produce an LNG stream and the nitrogen vent stream. The column has upper stages and lower stages. The LIN streams are directed to one or more upper stages of the column.

The present invention is directed to a method and system of separating carbon monoxide from syngas mixtures with high methane content by cryogenic means where a partial condensation cycle is generally employed, and more specifically towards combining the methane-rich liquid exiting the distillation column with a lower-boiling mixture so that the boiling point of the combined stream is lower than the boiling point of the methane-rich liquid.

A technology liquefies natural gas. The natural gas liquefaction method pre-cools treated natural gas by ethane evaporation, sub-cools liquefied gas using cooled nitrogen as a refrigerant, reduces liquefied gas pressure, separates non-liquefied gas and diverts liquefied natural gas. Before pre-cooling the natural gas is compressed, ethane is evaporated during the multi-stage pre-cooling of liquefied gas with simultaneous evaporation of ethane using cooled ethane as a refrigerant. Ethane generated by evaporation is compressed, condensed and used as a refrigerant during the cooling of liquefied gas and nitrogen, with nitrogen being compressed, cooled, expanded and fed to the natural gas sub-cooling stage. The natural gas liquefaction unit contains a natural gas liquefaction circuit, an ethane circuit and a nitrogen circuit. The natural gas liquefaction circuit includes a natural gas compressor, a cooler unit, ethane vaporizers, a closed-end subcooling heat exchanger, and a separator, connected in series.

Described herein are methods and systems for the liquefaction of natural gas to produce a LNG product. The methods and systems use an apparatus for separating a flash gas from a liquefied natural gas (LNG) stream to produce a LNG product and recovering refrigeration from the flash gas. The apparatus includes a shell casing enclosing a heat exchange zone comprising a coil wound heat exchanger, and a separation zone. The heat exchange zone is located above and in fluid communication with the separation zone. Flash gas is separated from the LNG product in the separation zone and flows upwards from the separation zone into the heat exchange zone where refrigeration is recovered from the separated flash gas.