초록 ▼

A method for cooling a natural gas stream (CxHy) and separating the cooled gas stream into various fractions having different boiling points, such as methane, ethane, propane, butane and condensates, comprises: cooling the gas stream (1,2); and separating the cooled gas stream in an inlet separation

A method for cooling a natural gas stream (CxHy) and separating the cooled gas stream into various fractions having different boiling points, such as methane, ethane, propane, butane and condensates, comprises: cooling the gas stream (1,2); and separating the cooled gas stream in an inlet separation tank (4); a fractionating column (7) in which a methane lean rich fluid fraction (CH4) is separated from a methane lean fluid fraction (C2+Hz); feeding at least part of the methane enriched fluid fraction from the inlet separation tank (4) into a cyclonic expansion and separation device (8), which preferably has an isentropic efficiency of expansion of at least 80%, such as a supersonic or transonic cyclone; and feeding the methane depleted fluid fraction from the cyclonic expansion and separation device (8) into the fractionating column (7) for further separation.

대표청구항 ▼

1. A method for cooling a natural gas stream and separating the cooled gas stream into various fractions having different boiling points, such as methane, ethane, propane, butane and condensates, the method comprising: cooling the gas stream in at least one heat exchanger assembly;separating the coo

1. A method for cooling a natural gas stream and separating the cooled gas stream into various fractions having different boiling points, such as methane, ethane, propane, butane and condensates, the method comprising: cooling the gas stream in at least one heat exchanger assembly;separating the cooled gas stream in an inlet separation tank into a methane enriched fluid fraction and a methane depleted fluid fraction;feeding the methane depleted fluid fraction from the inlet separation tank into a fractionating column in which a methane rich fluid fraction is separated from a methane lean fluid fraction;feeding at least part of the methane enriched fluid fraction from the inlet separation tank into a cyclonic expansion and separation device in which said fluid fraction is expanded and thereby further cooled and separated into a methane rich substantially gaseous fluid fraction and a methane depleted substantially liquid fluid fraction, wherein the cyclonic expansion and separation device operates to recompress said methane rich substantially gaseous fluid fraction to a pressure which is substantially higher than the operating pressure of the fractionating column;feeding the methane rich substantially gaseous fluid fraction directly from the cyclonic expansion and separation device to the at least one heat exchanger assembly to cool the incoming natural gas stream; andfeeding the methane depleted substantially liquid fluid fraction from the cyclonic expansion and separation device into the fractionating column for further separation,wherein the methane rich substantially gaseous fluid fraction and feed from a top outlet conduit of the fractioning column are compressed separately in export compressors to an export pressure,wherein the cyclonic expansion and separation device comprises: a) an assembly of swirl imparting vanes for imposing a swirling motion on the methane enriched fluid fraction, which vanes are arranged upstream of a nozzle in which the methane enriched fluid fraction is accelerated and expanded and thereby further cooled such that centrifugal forces separate the swirling fluid stream into a methane rich fluid fraction and a methane depleted fluid fraction and the cyclonic expansion and separation device further comprises an assembly of swirl imparting vanes which protrude in an at least partially radial direction from a torpedo shaped central body upstream of the nozzle, having a larger outer diameter than the inner diameter of the nozzle, or b) a throttling valve, having an outlet section which is provided with swirl imparting means that impose a swirling motion to the fluid stream flowing through the fluid outlet channel thereby inducing liquid droplets to swirl towards the outer periphery of the fluid outlet channel and to coalesce. 2. The method of claim 1, wherein the natural gas stream is cooled in a heat exchanger assembly comprising a first heat exchanger and a refrigerator such that the methane enriched fluid fraction supplied to an inlet of the cyclonic expansion and separation device has a temperature between −20 and −60 degrees Celsius, and wherein the methane rich substantially gaseous fluid fraction discharged by the cyclonic expansion and separation device is induced to pass through the first heat exchanger to cool the gas stream. 3. The method of claim 2, wherein the heat exchanger assembly further comprises a second heat exchanger in which the cooled natural gas stream discharged by the first heat exchanger is further cooled before feeding the natural gas stream to a refrigerator, and wherein cold fluid from a bottom section of the fractionating column is supplied to the second heat exchanger for cooling the natural gas stream within the second heat exchanger. 4. A system for cooling a natural gas stream and separating the cooled gas stream into various fractions having different boiling points, such as methane, ethane, propane, butane and condensates, the system comprising: at least one heat exchanger assembly for cooling the natural gas stream;an inlet separation tank for separating the cooled natural gas stream having an upper outlet for discharging a methane enriched fluid fraction and a lower outlet for discharging a methane depleted fluid fraction;a fractionating column which is connected to the lower outlet of the inlet separation tank in which column at least some of the methane depleted fraction discharged from the lower outlet of the inlet separation tank is further separated into a methane rich substantially gaseous fluid fraction and a methane lean substantially liquid fluid fraction;a cyclonic expansion and separation device which is connected to the upper outlet of the inlet separation tank, in which device said methane enriched fluid fraction is expanded and thereby further cooled and separated into a methane rich fluid fraction and a methane depleted fluid fraction, wherein the cyclonic expansion and separation device operates to recompress said methane rich substantially gaseous fluid fraction to a pressure which is substantially higher than the operating pressure of the fractionating column;a conduit for feeding the methane rich substantially gaseous fluid fraction directly from the cyclonic expansion and separation device to the at least one heat exchanger assembly for cooling the incoming natural gas stream; anda supply conduit for feeding the methane depleted substantially liquid fluid fraction from the cyclonic expansion and separation device into the fractionating column for further separation,a first compressor for compressing the methane rich substantially gaseous fluid fraction to an export pressure; anda second compressor for compressing feed from a top outlet conduit of the fractioning column to the export pressure,wherein the cyclonic expansion and separation device comprises: a) an assembly of swirl imparting vanes for imposing a swirling motion on the methane enriched fluid fraction, which vanes are arranged upstream of a nozzle in which the methane enriched fluid fraction is accelerated and expanded and thereby further cooled such that centrifugal forces separate the swirling fluid stream into a methane rich fluid fraction and a methane depleted fluid fraction, and the cyclonic expansion and separation device further comprises an assembly of swirl imparting vanes which protrude in an at least partially radial direction from a torpedo shaped central body upstream of the nozzle, having a larger outer diameter than the inner diameter of the nozzle, or b) a throttling valve, having an outlet section which is provided with swirl imparting means that impose a swirling motion to the fluid stream flowing through the fluid outlet channel thereby inducing liquid droplets to swirl towards the outer periphery of the fluid outlet channel and to coalesce. 5. The system of claim 4, wherein the cyclonic expansion and separation device is a throttling valve comprising a housing, a valve body which is movably arranged in the housing such that the valve body controls fluid flow from a fluid inlet channel into the fluid outlet channel of the valve further comprises a perforated sleeve via which fluid flows from the fluid inlet channel into the fluid outlet channel if in use the valve body permits fluid to flow from the fluid inlet channel into the fluid outlet channel, wherein at least some perforations of the sleeve have an at least partially tangential orientation relative to a longitudinal axis of the sleeve, such that the multiphase fluid stream is induced to swirl within the fluid outlet channel and liquid droplets are induced to swirl towards the outer periphery of the fluid outlet channel and to coalesce into enlarged liquid droplets. 6. The system of claim 5, wherein a tubular flow divider is connected to the outlet channel of the throttling valve, in which tubular flow divider liquid and gaseous phases of the fluid discharged by the valve are at least partly separated. 7. The system of claim 4, wherein the system further comprises a feed compressor and an air cooler that are arranged upstream of the at least one heat exchanger. 8. The system of claim 4, wherein the system is provided with temperature control means which are configured to maintain the temperature within an inlet of the cyclonic expansion and separation device between −20 and −60 degrees Celsius. 9. The method of claim 1, wherein the cyclonic expansion device comprises a nozzle and the isentropic efficiency of expansion in the nozzle of the cyclonic expansion device is at least 80%. 10. The system of claim 4, wherein the torpedo shaped body, the assembly of swirl imparting vanes and the nozzle are configured such that the isentropic efficiency of expansion in the nozzle is at least 80%. 11. The method of claim 2, wherein the heat exchanger assembly further comprises a second heat exchanger in which the cooled natural gas stream discharged by the first heat exchanger is further cooled before feeding the natural gas stream to the refrigerator, and wherein cold fluid from a bottom section of the fractionating column is supplied to the second heat exchanger for cooling the natural gas stream within the second heat exchanger. 12. The system of claim 4, wherein the cyclonic expansion and separation device operates to recompress said methane rich substantially gaseous fluid fraction prior to feeding said methane rich fluid fraction to an export compressor.