A process and an apparatus are disclosed for the recovery of components from a hydrocarbon gas stream which is divided into first and second streams. The first stream is cooled, expanded to lower pressure, and supplied to a fractionation tower. The second stream is cooled and separated into vapor and liquid streams. The vapor stream is divided into two portions. A first portion is cooled, expanded to tower pressure, and supplied to the tower at an upper mid-column feed position. The second portion and the liquid stream are expanded to tower pressure and supplied to the tower. After heating, compressing, and cooling, a portion of the tower overhead vapor is cooled, expanded, and supplied to the tower at the top feed position. The quantities and temperatures of the feeds to the tower maintain the overhead temperature of the tower whereby the major portion of the desired components is recovered.

A natural gas pretreatment system includes a heat exchanger having a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet receives a first pressurized gas stream having a first input temperature, and the second inlet receives a second pressurized gas stream having a second temperature. The second temperature is higher than the first temperature. The first outlet outputs the first gas stream; upon exiting the heat exchanger, the first gas stream has a first output temperature higher than the first input temperature. The second outlet outputs the second gas stream; upon exiting the heat exchanger, the second gas stream has a second output temperature lower than the second input temperature. The system further includes a pipeline network operable to receive the first pressurized gas stream.

A method to recover hydrocarbonfractions from refineries gas streams involves a pre-cooled heat refinery fuel gas stream mixed with a pre-cooled and expanded supply of natural gas stream in an inline mixer to condense and recover at least C.sub.3.sup.+ fractions upstream of a fractionator. The temperature of the gas stream entering the fractionator may be monitored downstream of the in-line mixer. The pre-cooled stream of high pressure natural gas is sufficiently cooled by flowing through a gas expander that, when mixed with the pre-cooled refinery fuel gas, the resulting temperature causes condensation of heavier hydrocarbon fractions before entering the fractionator. A further cooled, pressure expanded natural gas reflux stream is temperature controlled to maintain fractionator overhead temperature. The fractionator bottoms temperature may be controlled by a circulating reboiler stream.

Described herein are methods and systems for producing liquefied natural gas (LNG) from a methane-containing synthetic gas (MCSG). An MCSG feed stream may be cooled and partially liquefied using one or more heat exchanger units. A first phase separator and a second phase separator in downstream fluid flow communication with the first phase separator may be used to separate the partially liquefied MCSG stream into a first residue gas stream and first and second feed streams, the first and second feed streams then being fed into a distillation column to produce an LNG stream and a second residue gas stream.

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. A portion of the outlet vapor from the processing assembly is compressed to higher pressure, cooled and substantially condensed in a heat exchange means inside the processing assembly, then 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 system for separating olefinic hydrocarbon and hydrogen in an effluent fluid stream from a dehydrogenation reactor includes a heat exchanger that receives and partially condenses the effluent fluid stream so that a mixed phase effluent stream is formed. A primary separation device receives and separates the mixed phase effluent stream into a primary vapor stream and a primary liquid product stream. A heat exchanger receives and partially condenses the primary vapor stream so that a mixed phase primary stream is formed. A secondary separation device receives and separates the mixed phase primary stream into a secondary vapor stream and a secondary liquid product stream. A heat exchanger receives and warms the secondary vapor stream to provide refrigeration for partially condensing the effluent fluid stream and a heat exchanger receives and warms the secondary vapor stream to provide refrigeration for partially condensing the primary vapor stream. A mixed refrigerant compression system provides refrigerant to a heat exchanger to provide refrigeration.

Systems and methods for controlling a natural gas production system in an upset scenario, and/or during startup of turbo-expander system are disclosed. In one embodiment, a method of operating a Joule-Thomson valve of a natural gas production system includes determining an upset event within the natural gas production system, obtaining a flow rate through at least one expander prior to the upset event, and calculating, based on the flow rate, a percent opening of the Joule-Thomson valve. The method further includes opening the Joule-Thomson valve to the percent opening, controlling the Joule-Thomson valve by a PID controller in a set point tracking mode for a period of time, and controlling the Joule-Thomson valve by the PID controller in an automatic mode.

A heavies removal heat exchanger cools at least a portion of a feed gas stream. A scrubbing section receives the cooled main feed gas stream. A stripping section receives a fluid stream from the scrubbing section. A stripping gas feed expansion device receives a portion of the feed gas stream and is in fluid communication with the stripping section. A side draw vapor line receives a vapor stream from the vapor outlet of the stripping section and is in fluid communication with a reflux stream cooling passage of the heavies removal heat exchanger. A reflux separation device receives fluid from the heavies removal heat exchanger and has a liquid outlet and a vapor outlet. The liquid outlet is in fluid communication with the scrubbing section. A return vapor expansion device receives a vapor stream from the scrubbing section and directs a cooled vapor stream to a return vapor stream warming passage of the heavies removal heat exchanger. The reflux separation device vapor outlet is configured so that fluid passing therethrough joins with fluid that has exited the return vapor expansion device either before or after the fluid that has exited the return vapor expansion device flows through the return vapor stream warming passage of the heavies removal heat exchanger.

Plant and method for liquefying a flow of gas, comprising a cooling circuit which is provided with an upstream end which is intended to be connected to a source of pressurised gas to be liquified and a downstream end which is intended to be connected to a user member, the plant comprising, between the upstream and downstream ends, a set of members which are intended to liquefy the gas and comprise at least one exchanger for cooling the gas, and at least one expansion turbine which is mounted on a rotary axle which is supported by at least one bearing of the gas-static type, the cooling circuit comprising a pressurised gas injection conduit having an upstream end which is intended to receive pressurised gas supplied by the source and a downstream end which is connected to the bearing in order to provide support to the rotary axle, the plant comprising a conduit for recovering the gas which has been used in the bearing, the conduit for recovering the gas comprising an upstream end which is connected to the bearing and a downstream end, characterised in that the downstream end of the conduit for recovering the as is connected to the cooling circuit between the upstream and downstream ends thereof in order to recycle at that location at least a portion of the gas which has been used to support the rotary axle of the bearing with a few to liquefying said gas.

The amount of consumption of gas is reduced when the gas is expanded to be cooled by using a plurality of expansion turbines. A high-pressure expansion turbine includes: a gas supply passage through which bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. A low-pressure expansion turbine includes: a gas supply passage through which the bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. The bearing gas discharged from the gas discharge passage of the high-pressure expansion turbine is supplied to the gas supply passage of the low-pressure expansion turbine.