Abstract: The present invention relates to a process for liquefaction of a nitrogen stream produced by a cryogenic air separation unit. Cold liquid natural gas (LNG) is employed as refrigerant.A critical feature step of the invention is that the temperature of the vaporizing LNG should be maintained at a temperature lower than the critical temperature of the nitrogen stream being liquefied.The process involves compressing the nitrogen stream to at least 350 psi in a multistage compressor wherein interstage cooling is provided by heat exchange against vaporizing LNG. Further cooling and flashing of a portion of the liquid nitrogen stream serves to produce a quantity of liquid nitrogen that is free of hydrocarbon contamination and suitable for recycle to the air separation unit.

Abstract: The present invention is an energy efficient process for the recovery and purification of C.sub.3.sup.+ hydrocarbons from a high pressure natural gas or refinery/petrochemical feed gas containing C.sub.3.sup.+ hydrocarbons and light gases. In the process, the high pressure feed gas is initially cooled by heat exchange with a multi-component refrigerant fluid circulating in a closed-loop cycle thereby condensing a large portion of the C.sub.3.sup.+ hydrocarbons. The non-condensed, remaining gas is work expanded to an intermediate pressure thus providing refrigeration for condensing the remaining C.sub.3.sup.+ hydrocarbons. The condensed C.sub.3.sup.+ hydrocarbon liquid streams are combined and are further purified by distillation in an integrated distillation column. Optically, refrigeration for refluxing the integrated distillation column can be provided by the mixed refrigerant cycle.

Abstract: The present invention is an improvement to a conventional, single column, cryogenic, nitrogen generator which is able to produce nitrogen at near atmospheric pressure. In the improvement, the product nitrogen from the rectifier column is expanded through an expansion turbine to produce refrigeration for the process. Expanding the nitrogen makes it possible for the main air compressor to operate at a much lower pressure and achieve a significant reduction in compression power as compared to conventional waste expander and air expander cycles.

Abstract: The present invention relates to a process to produce large quantities of pure nitrogen and small amounts of high purity oxygen co-product which utilizes a modified single distillation column nitrogen generator. The modification is the addition of a small second column which purifies a portion of the oxygen enriched liquid from the nitrogen generator overhead condenser. Reboiling for the second column is provided by condensing part of the nitrogen overhead from the nitrogen generator. This condensed nitrogen is used as reflux in the nitrogen generator.

Abstract: The present invention is a process for phase separating, dephlegmating and optionally distilling a feed gas stream to recover a light gas product and a heavy hydrocarbon product wherein a predominant amount of the refrigeration for the process is provided by a two temperature and two pressure stage multicomponent closed-circuit refrigeration cycle.