Disclosed herein are processes for producing and separating ethane and ethylene. In some embodiments, an oxidative coupling of methane (OCM) product gas comprising ethane and ethylene is introduced to a separation unit comprising two separators. Within the separation unit, the OCM product gas is separated to provide a C.sub.2-rich effluent, a methane-rich effluent, and a nitrogen-rich effluent. Advantageously, in some embodiments the separation is achieved with little or no external refrigeration requirement.

A method of designing, constructing, and operating a hydrocarbon gas treatment plant is disclosed. A target hydrocarbon production range for a hydrocarbon gas meeting a required product specification is established. A cryogenic distillation column is designed and constructed with a vapor capacity to meet the target hydrocarbon production range. A variable feed refrigeration system is incorporated to cool an inlet feed of the hydrocarbon gas. The variable feed refrigeration system is designed to handle the target hydrocarbon production range and a wide range of contaminant concentrations in the inlet feed. A variable bottoms heating system is incorporated to handle heating duties associated with the wide range of contaminant concentrations in the inlet feed. A variable bottoms pumping system is incorporated to handle liquid flows associated with the wide range of contaminant concentrations in the inlet feed.

The present disclosure provides a method for separating a feed stream in a distillation tower. The method includes operating a controlled freeze zone section in a distillation tower that separates a feed stream at a temperature and pressure at which the feed stream forms a solid in the controlled freeze zone section, wherein the feed stream includes a first contaminant; maintaining a melt tray assembly in the controlled freeze zone section; introducing the feed stream to the controlled freeze zone section; and accumulating a liquid in the melt tray assembly until the liquid is at a predetermined liquid level in the controlled freeze zone section, by: feeding a second contaminant to the controlled freeze zone section; and adding the second contaminant to the melt tray assembly, wherein the liquid comprises the second contaminant.

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

Disclosed herein are processes for producing and separating ethane and ethylene. In some embodiments, an oxidative coupling of methane (OCM) product gas comprising ethane and ethylene is introduced to a separation unit comprising two separators. Within the separation unit, the OCM product gas is separated to provide a C.sub.2-rich effluent, a methane-rich effluent, and a nitrogen-rich effluent. Advantageously, in some embodiments the separation is achieved with little or no external refrigeration requirement.

The present disclosure provides method for clean methane startup of a distillation tower. The method includes maintaining a rectifier section and a lower section in the distillation tower, feeding stream to the lower section, directly feeding methane to at least one of the rectifier section and a rectifier section outlet line of the rectifier section when a contaminant concentration of the contaminant exiting as a vapor in an upper portion of the lower section is outside of a predetermined concentration and introducing the vapor from the lower section to the rectifier section when the contaminant concentration exiting the upper portion of the lower section is within the predetermined concentration.

A method and system for separating fluids in a distillation tower. The method may include feeding a stream to the distillation tower, wherein the stream includes carbon dioxide, reducing a carbon dioxide concentration of the stream received by the rectifier section by feeding a first cryogenic fluid to the controlled freeze zone section and accumulating rectifier section stream in at least one of a holding vessel and a sump of the rectifier section, and terminating reducing the carbon dioxide concentration when the carbon dioxide concentration of the stream travelling from the controlled freeze zone section to the rectifier section is less than or equal to a maximum carbon dioxide concentration. The first cryogenic fluid may comprise a substantially carbon-dioxide-free fluid.

Helium can be recovered from nitrogen-rich natural gas at high pressure with low helium loss by cryogenic distillation of the natural gas after pre-treatment of the gas to remove incompatible impurities and then recovery of natural gas liquid (NGL) from the pre-treated gas by distillation. Overall power consumption may be reduced, particularly if the feed to the helium recovery column system is at least substantially condensed by indirect heat exchange against a first portion of nitrogen-enriched bottoms liquid at first pressure, and a second portion of nitrogen-enriched bottoms liquid at a second pressure that is different from the first pressure.

Overall power consumption in a cryogenic distillation process for recovering helium from nitrogen-rich gases comprising helium may be reduced if the feed to the distillation column system is at least substantially condensed by indirect heat exchange against a first bottoms liquid at first pressure, and a second bottoms liquid at a second pressure that is different from the first pressure.

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.