The method includes the introduction of a feed flow into a first flask, the dynamic; expansion of the gaseous flow issuing from the flask in a turbine, then its introduction into a first purification column. It comprises the production at the head of the first column of a purified gas and the recovery at the bottom of the first column of a liquefied bottom gas, which is introduced, after expansion, into a second column for elimination of the C.sub.5.sup.+ hydrocarbons. The purified head natural gas issuing from the first column is heated in a first heat exchanger by thermal exchange with a feed gas. The method includes the compression of the gaseous head flow of the second column in a compressor before its introduction into a second separator flask.

A system for removing freezing components from a feed gas includes a heat exchanger, a scrub column and a return vapor expansion device. The heat exchanger includes a reflux cooling passage and a return vapor passage. Vapor from the scrub column is directed through the return vapor expansion device, where the temperature and pressure are lowered. The resulting cooled fluid then travels to the return vapor passage of the heat exchanger and is used to cool a vapor stream in the reflux cooling passage to create a reflux fluid stream that is directed to the scrub column.

Certain aspects of a natural gas liquid fractionation plant waste heat conversion to power using dual turbines Organic Rankine Cycle can be implemented as a first heating fluid circuit thermally coupled to first multiple heat sources of a natural gas liquid (NGL) fractionation plant, a second heating fluid circuit thermally coupled to second multiple heat sources of the NGL fractionation plant, and two power generation systems, each including an organic Rankine cycle (ORC). A control system actuates a first set of control valves to selectively thermally couple the first heating fluid circuit to at least a portion of the first multiple heat sources of the NGL fractionation plant, and to actuate a second set of control valves to selectively thermally couple the second heating fluid circuit to at least a portion of the second multiple heat sources of the NGL fractionation plant.

Systems and methods that utilize feed gases that are supplied in a wide range of compositions and pressure to provide highly efficient recovery of NGL products, such as propane, utilizing isenthalpic expansion, propane refrigeration, and shell and tube exchangers are described. Plants utilizing such systems and methods can be readily reconfigured between propane recovery and ethane recovery.

A method for operating a natural gas liquids processing (NGL) system, the system being selectively configured in either an ethane rejection configuration or an ethane recovery configuration, the method comprising, when the NGL system is in the ethane rejection configuration, collecting a reboiler bottom stream that, in the ethane rejection configuration, includes ethane in an amount of less than 5% by volume, and when the NGL system is in the ethane recovery configuration, collecting a reboiler bottom stream that, in the ethane recovery configuration, includes ethane in an amount of at least about 30% by volume.

Certain aspects of natural gas liquid fractionation plant waste heat conversion to simultaneous power and potable water using organic Rankine cycle and modified multi-effect distillation systems can be implemented as a system that includes two heating fluid circuits thermally coupled to two sets of heat sources of a NGL fractionation plant. The system includes a power generation system that comprises an organic Rankine cycle (ORC), which includes (i) a working fluid that is thermally coupled to the first heating fluid circuit to heat the working fluid, and (ii) a first expander configured to generate electrical power from the heated working fluid. The system includes a MED system thermally coupled to the second heating fluid circuit and configured to produce potable water using at least a portion of heat from the second heating fluid circuit. A control system actuates control valves to selectively thermally couple the heating fluid circuit to a portion of the heat sources of the NGL fractionation plant.

A method for removing heavy hydrocarbons from a feed gas by: feeding, into an absorber, a top reflux stream and a second reflux stream below the top reflux stream, wherein the absorber produces an absorber bottom product stream and an absorber overhead product stream; depressurizing and feeding the absorber bottom product stream to a stripper to produce a stripper bottom product stream and a stripper overhead product stream; cooling and feeding a portion of the absorber overhead product stream back to the absorber as the top reflux stream; and pressurizing and feeding the stripper overhead stream back to the absorber as the second reflux stream. A system for carrying out the method is also provided.

The invention relates to a method and system of preparing a lean methane-containing gas stream (22), comprising: feeding a hydrocarbon feed stream (10) into a separator (100); withdrawing from the separator (100) a liquid bottom stream (12); passing the liquid bottom stream (12) to a stabilizer column (200); withdrawing from the stabilizer column (200) a stabilized condensate stream (13) enriched in pentane, withdrawing from the stabilizer column (200) a stabilizer overhead stream (14) enriched in ethane, propane and butane; splitting the stabilizer overhead stream (14) according to a split ratio into a main stream portion (15) and a slip stream portion (16), passing the slip stream portion (16) to a fractionation unit (300) to obtain an ethane enriched stream (17) and a bottom stream enriched in propane and butane (18).

Certain aspects of natural gas liquid fractionation plant waste heat conversion to simultaneous power and cooling capacities using modified Goswami system can be implemented as a system. The system includes a waste heat recovery heat exchanger configured to heat a buffer fluid stream by exchange with a heat source in a natural gas liquid fractionation plant. The system includes a modified Goswami cycle energy conversion system including one or more first energy conversion system heat exchangers configured to heat a working fluid by exchange with the heated buffer fluid stream, a separator configured to receive the heated working fluid and to output a vapor stream of the working fluid and the liquid stream of the working fluid, a turbine and a generator, wherein the turbine and generator are configured to generate power by expansion of a first portion of the vapor stream of the working fluid, and a cooling subsystem including a cooling element configured to cool a process fluid stream from the natural gas liquid fractionation plant by exchange with a condensed second portion of the vapor stream of the working fluid.

A method for separating a hydrogen-containing hydrocarbon mixture (C2minus), which in addition to the hydrogen essentially contains hydrocarbons with two carbon atoms and methane, using a distillation column (10). Fluid (a, c, e) of the hydrocarbon mixture (C2minus) is cooled stepwise at a first pressure level, during which time first condensates (b, d) are separated from the fluid (a, c, e). Fluid (e) from the hydrocarbon mixture (C2minus) which remains gaseous after this is fed at the first pressure level into a C2 absorber (7), to which a liquid reflux (r) is added at the top, while a second condensate (f) is drawn off from the sump of the C2 absorber (7) and a gaseous top stream (g) containing predominantly methane and hydrogen is drawn off at the top of the C2 absorber (7). Fluid of the above-mentioned gaseous top stream (g) from the top of the C2 absorber (7) is cooled to a third temperature level and transferred at the first pressure level into a hydrogen separator (8) in which a methane-rich third condensate (i) is separated from the fluid of the gaseous top stream (g), leaving behind a gaseous, hydrogen-rich stream (h). Fluid of the first condensates (b, d) and fluid of the second condensate (f) is depressurized from the first pressure level to a second pressure level below the first pressure level and fed into the distillation column (10) which is operated at the second pressure level. Fluid (e) of the third condensate (i) which is separated in the hydrogen separator (8) from the fluid of the gaseous top stream (g) from the top of the C2 absorber is used as the reflux (r) added at the top of the C2 absorber (7) and transferred from the hydrogen separator to the C2 absorber solely by gravity. The invention also relates to a corresponding separating unit and a corresponding olefin apparatus.