A system for the removal of nitrogen from a liquid natural gas (LNG) stream. The system. comprises a feed heat changer and a stripper column. The heat receives the LNG stream and cools the LNG stream via heat exchange with a stripper column side-draw stream to yield a cooled LNG stream and a heated side-draw stream. The stripper column receives the cooled LNG stream at a first tray and the heated side-draw stream. The stripper column produces the stripper column side-draw stream, a stripper column overhead stream, and a stripper column bottom stream. The stripper column side-draw stream is taken from the stripper column at a second tray. The second tray is at least about 15 feet higher than the feed heat exchanger.

A system for removing nitrogen from a natural gas fluid feed stream includes a main heat exchanger that receives the natural gas fluid feed stream. A distillation column receives a cooled fluid stream from the main heat exchanger and features a return vapor outlet and a side vapor outlet port. The return vapor outlet provides nitrogen vapor to the main heat exchanger which is warmed therein. The side vapor outlet port provides vapor to the main heat exchanger and a reflux compressor receives and compresses the resulting fluid from the main heat exchanger. A reflux aftercooler receives and cools fluid from the reflux compressor, directs cooled fluid to the main heat exchanger and the resulting fluid is directed to a reflux separation device. The reflux separation device has a vapor outlet and a liquid outlet. The vapor outlet of the reflux separation device directs fluid to the main heat exchanger so that fluid is directed to the first reflux inlet port of the distillation column. The liquid outlet of the reflux separation device directs fluid to a second reflux inlet port of the distillation column.

This method envisions cooling the supply flow in a first heat exchanger, separation in a first separation flask in order to produce a light upper flow and a heavy lower flow and dividing the light upper flow into a supply fraction of a dynamic pressure reduction turbine and a supply fraction of a first distillation column. A cooled reflux flow is formed from an effluent from a dynamic pressure reduction turbine, the portion of the effluent being cooled and at least partially liquefied in a heat exchanger. The cooled reflux flow is introduced from the heat exchanger into the first distillation column.

A system and methods for processing a feed gas in a column are provided herein. A method includes feeding a feed gas into a port of a sleeve disposed around at least a portion of a periphery of the column. The sleeve includes a space between an outer wall of the column and an inner wall of the column. The sleeve releases the feed gas into the column through an opening disposed at an opposite end of the sleeve from the port.

A process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C.sub.2 (or C.sub.3) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the tower overhead vapor is directed to an absorbing means and a heat and mass transfer means inside a processing assembly. The outlet vapor from the processing assembly is compressed to higher pressure and cooled, then a portion is substantially condensed in a heat exchange means inside the processing assembly, expanded to lower pressure, and supplied to the heat and mass transfer means to provide cooling. Condensed liquid from the absorbing means is fed to the tower.

A method of cooling an ethylene discharge gas includes the steps of drawing a liquid ethane from a C2 splitter; reducing a pressure of the drawn liquid ethane in a let-down valve to produce a cooled liquid ethane; cooling the ethylene discharge gas with the cooled liquid ethane in a vaporizer, the cooled liquid ethane exiting the vaporizer as an ethane vapor; pressurizing the ethane vapor in a heat pump to produce a heated vapor ethane; and returning the heated vapor ethane to the C2 splitter. The ethylene discharge gas may be from an ethylene refrigerant compressor.

This method comprises cooling the feed natural gas in a first heat exchanger and introducing the cooled, feed natural gas into a first separation flask. It comprises the dynamic expansion of a turbine supply flow in a first expansion turbine and introducing the expanded flow into a separation column. This method comprises removing, at the head of the separation column, a head flow rich in methane and removing a first recirculation flow from the compressed head flow rich in methane. The method comprises forming at least a second recirculation flow obtained from the head flow rich in methane downstream of the separation column and forming a dynamic expansion flow from the second recirculation flow.

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.

Process for extracting nitrogen from a feed stream of natural gas or of biomethane comprising at least nitrogen, methane, CO.sub.2 and/or H.sub.2S, wherein a liquid stream enriched in methane resulting from a cryogenic separation is recovered by pumping the bottom product of one or more of the columns and/or pumping a liquid stream to a pressure P2 greater than 25 bar absolute and preferably greater than the critical pressure of said product.

A process and an apparatus are disclosed for separation of a hydrocarbon gas stream containing methane and heavier hydrocarbons and significant quantities of nitrogen and carbon dioxide. The gas stream is cooled and expanded, then fractionated in a first distillation column into a first overhead vapor and a hydrocarbon liquid stream containing the majority of the carbon dioxide. The hydrocarbon liquid stream is fractionated into a hydrocarbon vapor stream and a less volatile fraction comprised of heavier hydrocarbons. The first overhead vapor is cooled, expanded, and separated into vapor and liquid streams. Both streams are cooled and expanded before feeding a second distillation column that produces a second overhead vapor that is predominantly nitrogen and a bottom liquid that is predominantly methane. The bottom liquid is vaporized and combined with the hydrocarbon vapor stream to form a volatile residue gas fraction containing the majority of the methane.