Abstract: A method for cooling a process stream in which one of a plurality of open-loop refrigerant streams is cooled by indirect heat exchange with other of the open-loop refrigerant stream in a refrigerant heat exchanger to yield a cooled primary refrigerant stream. The process stream is cooled by indirect heat exchange with a process refrigerant stream in a separate process heat exchanger, wherein the process refrigerant stream comprises at least a portion of the cooled primary refrigerant stream. The method is particularly useful in large process plants which require multiple parallel heat exchangers to cool the process stream.

Abstract: Plate-and-fin core-type heat exchangers are installed within pressure vessels in a manner which eliminates the need for distributors, collectors, headers, nozzles, and manifolds at the feed inlet, the processed gas outlet, or both the feed inlet and the processed gas outlet of each exchanger core. The heat exchangers can be installed in parallel or in series within a single pressure vessel. Alternatively, the heat exchangers can be installed in pressure vessels which are arranged in series such that multiple liquid product streams can be obtained. The heat exchangers preferably are operated in the condensing mode in which feed gas is cooled and partially condensed. The operation of the heat exchangers is characterized by the cocurrent flow of the condensate and uncondensed feed gas, preferably in the vertical or near-vertical direction. In an alternative embodiment, the heat exchangers are operated such that a feed fluid is cooled without phase change.

Abstract: A method for cooling a process stream in which one of a plurality of open-loop refrigerant streams is cooled by indirect heat exchange with other of the open-loop refrigerant streams in a refrigerant heat exchanger to yield a cooled primary refrigerant stream. The process stream is cooled by indirect heat exchange with a process refrigerant stream in a separate process heat exchanger, wherein the process refrigerant stream comprises at least a portion of the cooled primary refrigerant stream. The method is particularly useful in large process plants which require multiple parallel heat exchangers to cool the process stream.

Abstract: Dephlegmator system without headers, collectors, or distributors at the bottom end of feed circuits in plate and fin exchangers operating in condensing or rectifying service. Each dephlegmator is installed within a pressure vessel, thereby eliminating the need for headers, collectors, or distributors at the bottom end of the feed circuits. In an alternative embodiment of the invention, upper and lower segments of the pressure vessel are isolated by a mid-vessel seal between the vessel and dephlegmator walls, and headers or collectors are not required at the upper and lower ends of the feed circuits.

Abstract: C2 and C3 hydrocarbons, particularly ethylene and propylene, are recovered from refinery or petrochemical plant gas mixtures by cooling and fractionating a feed gas mixture containing these hydrocarbons and lighter components. Refrigeration for the process is provided by a closed-loop gas expander refrigeration process cycle which preferably uses nitrogen as the recirculating refrigerant. Cooling and fractionation may be effected in a dephlegmator.

Abstract: A high purity methane product is recovered from a feed gas mixture containing methane and one or more hydrocarbons heavier than methane by cooling, condensing, and rectifying the feed in a dephlegmator. The high purity methane product, containing at least 98 mole % methane, can be liquefied and stored for use as a fuel for internal combustion engines. A hydrocarbon product containing components heavier than methane is also recovered.Methane recovery and C.sub.2.sup.+ hydrocarbon product purity can be improved by the use of a combined stripping heat exchanger and feed gas cooler. External refrigeration is utilized and can be supplemented in part by autorefrigeration provided by vaporizing dephlegmator liquid.

Abstract: Nitrogen is removed from a pressurized feed gas mixture containing nitrogen and methane by cooling, partial condensation, and rectification in one or more dephlegmators. Autorefrigeration is provided by pressure letdown of selected process streams and external refrigeration is not required.

Abstract: Hydrocarbons are recovered from the product purge gas in an alkene polymerization process by absorption of heavier hydrocarbons from the purge gas by an intermediate hydrocarbon stream to yield a vapor rich in inert gas and alkene monomer. Alkene monomer is condensed and rectified by dephlegmation at low temperatures from the inert gas, flashed and vaporized to provide refrigeration for the condensation step, and recycled to the polymerization process. The intermediate hydrocarbon from the absorption step is recycled to the polymerization process. Optionally a portion of the inert gas is reused for purge gas.