KR20070012814A - Natural gas liquefaction - Google Patents

Abstract

A process for liquefying natural gas in conjunction with producing a liquid stream containing predominantly hydrocarbons heavier than methane is disclosed. In the process, the natural gas stream to be liquefied is partially cooled, expanded to an intermediate pressure, and supplied to a distillation column. The bottom product from this distillation column preferentially contains the majority of any hydrocarbons heavier than methane that would otherwise reduce the purity of the liquefied natural gas. The residual gas stream from the distillation column is compressed to a higher intermediate pressure, cooled under pressure to condense it, and then expanded to low pressure to form the liquefied natural gas stream. ® KIPO & WIPO 2007

Description

Natural Gas Liquefaction {NATURAL GAS LIQUEFACTION}

The present invention relates to a process for treating natural gas or other methane-rich gas streams to produce liquefied natural gas (LNG) streams with high methane purity and liquid streams containing primarily hydrocarbons heavier than methane. .

Natural gas is typically recovered from drilling wells drilled underground storage layers. Natural gas is generally the main component of methane, ie methane contains more than 50 mol% of natural gas. Depending on the particular underground reservoir, the natural gas also contains relatively smaller amounts of heavier hydrocarbons such as ethane, propane, butane, pentane and the like, and water, hydrogen, nitrogen, carbon dioxide and other gases.

Most natural gas is treated in gaseous form. The most common means for transportation from the wellhead to the natural gas treatment plant and from there to the natural gas consumer is the high pressure gas delivery pipeline. In many cases, however, it has been found necessary and / or desirable to liquefy natural gas for transport or use. For example, remote sites often have no pipeline infrastructure to allow convenient transportation of natural gas to the market. In this case, a much smaller volume of LNG allows for the delivery of LNG using cargo ships and transport trucks compared to gaseous natural gas, thereby significantly reducing the transportation costs.

Another situation that favors the liquefaction of natural gas is for its use as automotive fuel. In metropolitan areas, there are buses, taxis, and truck fleets that can be moved to LNG if there are economical sources of LNG available. Vehicles of these LNG fuels produce significantly less air pollution due to the clean-burning nature of natural gas compared to similar vehicles running on gasoline and diesel engines that burn higher molecular weight hydrocarbons. In addition, when LNG is of high purity (i.e., methane purity is at least 95 mol%), the amount of carbon dioxide ("greenhouse gas") produced by the lower carbon: hydrogen ratio for methane compared to all other hydrocarbon fuels Considerably less.

In general, the present invention relates to liquid streams consisting primarily of hydrocarbons heavier than methane as by-products, for example liquid natural gas (NGL), propane, butane and more composed of ethane, propane, butane and heavier hydrocarbon components. It relates to liquefied natural gas while producing liquefied petroleum gas (LPG) composed of heavy hydrocarbon components, or condensate composed of butane and heavier hydrocarbon components. The production of liquid stream by-products has two important benefits: The resulting LNG is high in methane purity, and the liquid by-product is an expensive product that can be used for many other purposes. Typical analyzes of natural gas streams to be treated in accordance with the present invention show approximate mole percentages of 84.2% for methane, 7.9% for ethane and other C ₂ components, 4.9% for propane and other C ₃ components and 1.0% for isobutane. n-butane is 1.1%, pentane plus is 0.8%, and the remainder consists of nitrogen and carbon dioxide. Sulfur containing gases are also sometimes present.

There are a number of known methods for the liquefaction of natural gas. For example, in an overview of many such processes, Finn, Adrian J., Grant L. Johnson, and Terry R. Tomlinson, "LNG Technology for Offshore and Mid-Scale Plants", Proceedings of the Seventy-Ninth Annual Convention of the Gas Processors Association, pp. 429-450, Atlanta, Georgia, March 13-15,2000 and Kikkawa, Yoshitsugi, Masaaki Ohishi, and Noriyoshi Nozawa, "Optimize the Power System of Baseload LNG Plant", Proceedings of the Eightieth Annual Convention of the Gas Processors Association, San Antonio, Texas, March 12-14, 2001. US Patent No. 4,445,917; US Patent No. 4,525,185; US Patent No. 4,545,795; U.S. Patent 4,755,200; US Patent No. 5,291,736; US Patent No. 5,363,655; US Patent No. 5,365,740; U.S. Patent 5,600,969; US Patent No. 5,615,561; US Patent No. 5,651,269; U.S. Patent 5,755,114; US Patent No. 5,893,274; US Patent No. 6,014,869; US Patent No. 6,062,041; US Patent No. 6,119,479; US Patent No. 6,125,653; US Patent No. 6,250,105 B1; US Patent No. 6,269,655 B1; US Patent No. 6,272,882 B1; US Patent No. 6,308,531 B1; US Patent No. 6,324,867 B1; US Patent No. 6,347,532 B1; And related processes are also disclosed in co-pending US patent application Ser. No. 10 / 161,780, filed June 4, 2002. The methods generally comprise the step of purifying, cooling, condensing and expanding natural gas (by removing water and cumbersome compounds such as carbon dioxide and sulfur compounds). Cooling and condensation of natural gas can be accomplished in a number of different ways. In the "multistage cooling method", heat exchange of natural gas with several refrigerants with successively low boiling points, for example propane, ethane and methane, is used. As an alternative, such heat exchange can be achieved using a single refrigerant by evaporating the refrigerant at several different pressure levels. In the "multicomponent cooling method", heat exchange of natural gas using one or more refrigerant liquids composed of several refrigerant components is used instead of a plurality of single component refrigerants. The expansion of natural gas is isenthalpically (e.g. using Joule-Thomson expansion) and isentropically (e.g. using one-expansion turbine). Can be achieved.

Regardless of the method used for liquefaction of the natural gas stream, it is generally necessary to remove a significant fraction of hydrocarbons heavier than methane before liquefaction of the methane-rich stream. The reasons for this hydrocarbon removal step are numerous, including the need to control the heating value of the LNG stream, and the value of the heavier hydrocarbon components of course as a product. Unfortunately, little attention has been paid to the efficiency of the hydrocarbon removal step so far.

According to the present invention, it has been found that careful integration of the hydrocarbon removal step into the LNG liquefaction process can produce both LNG and individual heavier liquid hydrocarbon products using significantly less energy than prior art processes. . The invention can be applied at lower pressures, but is particularly advantageous when treating feed gases in the range of 400 to 1500 psia [2,758 to 10,342 kPa (a)] or higher.

For a better understanding of the invention, reference is made to the following examples and figures.

Referring to the drawings,

1 is a flow chart of a natural gas liquefaction facility suitable for the co-production of LPG according to the present invention;

2 and 3 are diagrams of alternative fractionation systems that can be used in the process of the present invention;

4 is a pressure-enthalpy state diagram in methane used to illustrate the advantages of the present invention over prior art processes;

5, 6, 7, 8, 9, and 10 are flowcharts of alternative natural gas liquefaction plants suitable for the joint production of liquid streams according to the invention.

In the following description of the figures, a table is provided that summarizes the calculated flow rates for representative process conditions. In the tables presented herein, the values for flow rates (in moles / hour) have been rounded to the nearest integer for convenience. The total flow rate of the streams exemplified in the table contains all non-hydrocarbon components and is therefore generally greater than the sum of the flow rates of the streams in the hydrocarbon components. The temperatures shown are approximate values rounded up to the nearest temperature. Process design calculations performed for the purpose of comparing the processes shown in the figures are based on the assumption that there is no heat leakage from (or from) the process from (or to) the surroundings. The quality of commercially available insulation makes this a very reasonable assumption, which is generally made by those skilled in the art.

For convenience, process parameters have been reported in both traditional British units and in the International System of Units (SI). The molar flow rates shown in the table can be interpreted as pound moles / hour or kilogram moles / hour. The energy consumption rates reported in horsepower (HP) and / or thousand British calorie units / hour (MBTU / Hr) correspond to the specified molar flow rates in pound moles / hour. The reported energy consumption in kilowatts (kW) corresponds to the specified molar flow rate in kilogram moles / hour. The production rate reported in pounds per hour (Lb / Hr) corresponds to the specified molar flow rate in pound moles / hour. The production rate reported in kilograms / hour (kg / Hr) corresponds to the specified molar flow rate in kilograms per hour.

Referring now to FIG. 1, we begin with the description of the process according to the invention, where it is desirable to produce LPG by-products containing most of the propane and heavier components in the natural gas feed stream. In this simulation of the invention, the inlet gas enters the plant as stream 31 at 90 ° F. [32 ° C.] and 1285 psia [8,860 kPa (a)]. If the inlet gas contains a concentrate of carbon dioxide and / or sulfur compounds that do not meet the standards of the product stream, the compound is removed (not illustrated) by appropriate pretreatment of the feed gas. In addition, the feed stream is generally dehydrated to prevent hydrate (ice) formation under cryogenic conditions. Solid desiccants are typically used for this purpose.

Feed stream 31 is cooled in heat exchanger 10 by heat exchange with a refrigerant stream and flashed separator liquid (stream 40a) at -14 ° F [-26 ° C]. Note that in all cases the heat exchanger 10 is representative of a plurality of individual heat exchangers or a single multi-pass heat exchanger, or all combinations of the above (a discussion of whether to use more than one heat exchanger for the indicated cooling service). Depends on a number of factors including but not limited to inlet gas flow rate, heat exchanger size, stream temperature, etc.). Cooled stream 31a enters separator 11 at 23 ° F. [-5 ° C.] and 1278 psia [8,812 kPa (a)], where steam (stream 32) is the condensed liquid (stream 33 )).

The vapor from separator 11 (stream 32) is divided into two streams 34, 36, and stream 34 contains about 42% of the total steam. Although some situations may be advantageous for combining stream 34 and a portion of the condensation liquid (stream 39) to form stream 35, there is no flow in stream 39 in this simulation. The combined stream 35 passes through the heat exchanger 13 in a heat exchange relationship with the refrigerant stream 71e, leading to cooling of the stream 35a and significant condensation. Subsequently condensed stream 35a at −90 ° F. [−68 ° C.] is slightly higher than the operating pressure of fractionation tower 19 (approximately 450 psia) via a suitable expansion device, for example expansion valve 14. [3,103 kPa (a)]) flash is expanded. Part of the stream is evaporated during expansion, leading to cooling of the entire stream. In the process shown in FIG. 1, the expanded stream 35b leaving expansion valve 14 reaches a temperature of -123 ° F. [-86 ° C.]. The expanded stream 35b is cooled at -78 ° F. in the heat exchanger 21 as the heat exchanger 21 provides cooling and partial condensation of the vapor distillation stream 37 rising in the fractionation stage of the fractionation tower 19. -61 ° C.] and further evaporates. The warmed stream 35c is then fed at the upper mid-point feed position of the ethane removal compartment 19b of the fractionation tower 19.

The remaining 58% (stream 36) of the steam from separator 11 enters one expander 15, where mechanical energy is obtained from a portion of the high pressure feed. The machine 15 expands the vapor substantially isotropically from a pressure of about 1278 psia [8,812 kPa (a)] to the tower operating pressure, where one expansion expands the expanded stream 36a to approximately -57 ° F. [-49 C]]. A typical commercially available inflator can recover approximately 80-85% of the theoretically possible work from an ideal isentropic expansion. Recovered work is commonly used to drive centrifugal compressors (eg item 16), which can be used, for example, to recompress the overhead gas (stream 49) of the tower. The expanded and partially condensed stream 36a is fed as feed to distillation column 19 at the lower mid-column feed point. The remainder of the separator liquid (stream 33), stream 40, is flash expanded by the expansion valve 12 slightly above the operating pressure of the ethane eliminator 19, thereby bringing the stream 40 at -14 ° F. [-26]. [C] (stream 40a) and then it cools the incoming feed gas as described earlier. Subsequently, stream 40b, now 75 ° F. [24 ° C.], is introduced into the ethane eliminator 19 at the second lower mid-column feed point.

The ethane eliminator of the fractionation tower 19 is a conventional distillation column comprising a plurality of vertically spaced trays, one or more packed beds, or some combination of trays and packings. As is common in natural gas treatment plants, a fractionation tower may consist of two compartments. The upper compartment 19a is a separator, where the top feed is divided into individual steam and liquid portions thereof, and the steam rising from the bottom distillation or ethane removal compartment 19b is the steam portion of the top feed (if present). Combined to form an ethane eliminator overhead vapor (stream 37) which flows out of the top of the tower. The lower ethane removal compartment 19b contains the tray and / or the fill and provides the necessary contact between the liquid falling downward and the vapor rising upward. The ethane removal compartment also contains one or more reboilers (eg, reboiler 20), which heat and evaporate a portion of the liquid flowing down the column to provide stripping vapor that flows over the column. Liquid product stream 41 exits the bottom of the tower at 213 ° F. [101 ° C.], based on a typical standard of ethane to propane ratio of 0.020: 1 on a molar basis in the bottom product.

Overhead distillation stream 37 leaves the ethane eliminator 19 at −73 ° F. [−59 ° C.] and is cooled and partially condensed in reflux condenser 21 as described earlier. Partially condensed stream 37a enters reflux drum 22 at −94 ° F. [−70 ° C.], where condensation liquid (stream 44) is separated from uncondensed vapor (stream 43). . Condensed liquid (stream 44) is pumped by pump 23 as reflux stream 44a to the top feed point on ethane eliminator 19.

If the ethane removal compartment forms the bottom of the fractionation tower, the reflux condenser 21 may be located inside the tower above the column 19 as shown in FIG. This eliminates the need for reflux drum 22 and reflux pump 23 because the distillation stream is then cooled and separated in the column above the fractionation unit of the column. Alternatively, the use of a dephlegmator (e.g., the condenser 21 in FIG. 3) instead of the reflux condenser 21 of FIG. 1 excludes the reflux drum and the reflux pump and at the same time provides a fractionation stage. To replace that in the upper section of the ethane eliminator column. If the condenser is located at the same plane level in the installation, the condenser is connected to a vapor / liquid separator and the liquid collected in the separator is pumped to the top of the distillation column. The decision of whether to include a reflux condenser inside the column or whether to use a splitter generally depends on the size of the equipment and the requirements on the heat exchanger surface.

Uncondensed steam from stream reflux drum 22 (stream 43) is warmed to 93 ° F. [34 ° C.] in heat exchanger 24, and then a portion (stream 48) is withdrawn to the fuel gas for the plant. (The amount of fuel gas to be withdrawn is largely determined by the fuel required for the engine and / or turbine driving the gas compressor in the installation, such as refrigerant compressors 64, 66, 68 in this embodiment). The remainder of the warmed steam (stream 49) is compressed by a compressor 16 driven by expanders 15, 61, 63. After cooling to 100 [deg.] F. [38 [deg.] C.] in the discharge cooler 25, stream 49b is subjected to -83 [deg.] F. [-64 [deg.] C.] in heat exchanger 24 by interchange with cold steam, stream 43. Further cooled.

Stream 49c is then introduced into heat exchanger 60 and further cooled by refrigerant stream 71d to -255 ° F. [-160 ° C.] to condense and subcool the stream, which is then mechanical energy from the stream. To get into the inflator 61. The machine 61 allows the liquid stream 49d to be substantially isentropically slightly above atmospheric pressure, from a pressure of about 593 psia [4,085 kPa (a)] to an LNG storage pressure (15.5 psia [107 kPa (a)]). Inflate. One expansion cools the expanded stream 49e to a temperature of approximately -256 ° F. [-160 ° C.], which is then directed to an LNG storage tank 62 containing LNG product (stream 50). .

All of the cooling in streams 35 and 49c is provided by a closed cycle cooling loop. The actual fluid of the cycle is a mixture of hydrocarbons and nitrogen, the composition of which is adjusted as necessary to provide the required refrigerant temperature while condensing at a reasonable pressure using the available cooling medium. In this case, condensation with cooling water is assumed, so that a refrigerant mixture consisting of nitrogen, methane, ethane, propane and heavier hydrocarbons is used in the simulation of the process of FIG. 1. The composition of the stream consists of 8.7% nitrogen, 31.7% methane, 47.0% ethane and 8.6% propane in approximate mole percent, with the remainder being heavier hydrocarbons.

Refrigerant stream 71 leaves discharge cooler 69 at 100 ° F. [38 ° C.] and 607 psia [4,185 kPa (a)]. The refrigerant stream enters the heat exchanger 10 and is partially condensed by the expanded refrigerant stream 71f and other refrigerant streams cooled to -34 ° F [-37 ° C] and partially warmed. In the simulation of FIG. 1, the other refrigerant streams above were assumed to be commercial-quality propane refrigerants at three different temperature and pressure levels. The partially condensed refrigerant stream 71a is then introduced into the heat exchanger 13 for further cooling to a -90 ° F. [-68 ° C.] by the partially warmed expansion refrigerant stream 71e, whereby the refrigerant (stream ( 71b)) is further condensed. The refrigerant is condensed and then subcooled to -255 ° F. [-160 ° C.] by expansion refrigerant stream 71d in heat exchanger 60. The subcooled liquid stream 71c enters the work expander 63 where the stream is substantially isentropically from about 586 psia [4,040 kPa (a)] to about 34 psia [234 kPa (a)]. Mechanical energy is obtained from the stream as it expands to pressure. During expansion, part of the stream is evaporated, leading to cooling of the entire stream (stream 71d) to -264 ° F. [-164 ° C.]. Expanded stream 71d is then reflowed into heat exchangers 60, 13, 10, where the stream is evaporated and superheated so that stream 49c, stream 35, and refrigerant (stream 71, 71a, 71b)).

The superheated refrigerant vapor (stream 71g) leaves the heat exchanger 10 at 90 ° F. [32 ° C.] and is compressed to 617 psia [4,254 kPa (a)] in three stages. Each of the three compression stages (refrigerant compressors 64, 66, 68) is driven by a supplemental power source followed by a cooler (discharge coolers 65, 67, 69) for removal of the heat of compression. Compressed stream 71 from the discharge cooler 69 is returned to the heat exchanger 10 to complete this cycle.

A summary of the flow rate and energy consumption rate of the stream in the process shown in FIG. 1 is shown in the table below:

The efficiency of the LNG production process is typically compared using the required "non-power consumption", which is the ratio of total cooling compression power to total liquid production. Published information on specific power consumption in prior art processes in LNG production is available from 0.168 HP-Hr / Lb [0.276 kW-Hr / kg] to 0.182 HP-Hr / Lb [0.300 kW-Hr / kg]. It is believed to be based on an on-stream factor of 340 days per year for LNG production plants. Based on the same, the specific power consumption in the embodiment of FIG. 1 of the present invention is 0.148 HP-Hr / Lb [0.243 kW-Hr / kg], which is 14-23% more efficient than the prior art process. Is improved.

There are two main factors that explain the efficiency improvement of the present invention. The first factor can be understood by examining the thermodynamic properties of the liquefaction process when applied to a high pressure gas stream as contemplated in this embodiment. Since the main constituent of this stream is methane, the thermodynamic properties of methane can be used for the purpose of comparing the liquefaction cycles used in the prior art processes to the cycles used in the present invention. 4 contains a pressure-enthalpy state diagram in methane. In most prior art liquefaction cycles, all gas stream cooling is achieved while the stream is at high pressure (path AB), and then the stream is then expanded to the pressure of the LNG storage vessel (slightly higher than atmospheric pressure) (path BC ). One expander can be used for this expansion step, which can typically recover approximately 75-80% of the theoretically available work in ideal isentropic expansion. For simplicity, complete isentropic expansion is shown in FIG. 4 for path B-C. Even so, the enthalpy reduction provided by this work expansion is very small because the line of constant entropy is nearly perpendicular in the liquid region of the state diagram.

This is in contrast to the liquefaction cycle of the present invention. After partial cooling at high pressure (path A-A '), the gas stream is thermally expanded to medium pressure (path A'-A ") (in addition, full isentropic expansion is indicated for simplicity). Cooling is achieved at medium pressure (path A ″ -B ′), and the stream is then expanded to the pressure of the LNG storage vessel (path B′-C). Since the line of constant entropy slopes less steeply in the vapor region of the state diagram, a significantly greater enthalpy reduction is provided by the first daily expansion step (path A'-A ") of the present invention. The total amount of cooling (sum of paths A-A 'and A "-B') is less than the amount of cooling required for the prior art process (path AB), so that the cooling power (and thus the cooling compression force) required for liquefaction of the gas stream Is reduced.

A second factor explaining the efficiency improvement of the present invention is the excellent performance of hydrocarbon distillation systems at lower operating pressures. The hydrocarbon removal step in most prior art processes is carried out at high pressure, typically using a scrub column using a low temperature hydrocarbon liquid as the absorption stream to remove heavier hydrocarbons from the incoming gas stream. The operation of the scrub column at high pressure is not very efficient because it leads to the co-absorption of a significant fraction of methane and ethane from the gas stream, which is then removed from the absorbing liquid and cooled To be part of the LNG product. In the present invention, the hydrocarbon removal step is carried out at medium pressure, where vapor-liquid equilibrium is much more advantageous, which leads to highly efficient recovery of the heavier hydrocarbons desired in the by-product liquid stream.

Other embodiment

Those skilled in the art will appreciate that the present invention can be modified for use in all types of LNG liquefaction plants to allow co-production of NGL streams, LPG streams, or condensate streams, as best suits the needs at a given plant location. Will recognize.

It will also be appreciated that various process forms may be used to recover the liquid byproduct stream. Rather than producing LPG by-products as described earlier, the present invention provides for the recovery of an NGL stream containing a significant fraction of the C ₂ components present in the feed gas, or the C ₄ and heavier components present in the feed gas. It can be adapted for the recovery of condensate streams containing only bays.

1 shows a preferred embodiment of the present invention under the indicated processing conditions. 5-10 illustrate alternative embodiments of the present invention that may be considered for particular applications. Depending on the amount of heavier hydrocarbons in the feed gas and the feed gas pressure, the cooled feed stream 31a leaving the heat exchanger 10 cannot contain any liquid (either because it exceeds its dew point or , Since this exceeds its cricondenbar), the separator 11 shown in FIGS. 1 and 6 to 10 is not required, and the cooled feed stream is not suitable for expansion devices, for example work expanders. Can be flowed directly to (15). If the incoming gas is richer than what has been described so far, embodiments of the present invention as shown in FIG. 5 can be used. The condensed liquid stream 33 flows through the heat exchanger 18 and is subcooled and then divided into two parts. The first portion (stream 40) flows through expansion valve 12, where the first portion is expanded for flash evaporation when the pressure is reduced to approximately the pressure of distillation column 19. Cold stream 40a from expansion valve 12 then flows through heat exchanger 18, where the stream is partially as it is used for subcooling stream 33, as described earlier. Is warmed up. The partially warmed stream 40b is then further warmed in the heat exchanger 10 and flows to the lower mid-point feed position on the fractionation column 19. The second liquid portion (stream 39), which is still at high pressure, is (1) combined with the portion 34 of the vapor stream from the separator 11, (2) with the substantially condensed stream 35a, or (3) Expanded in expansion valve 17 and then fed to fractionation column 19 or combined with expansion stream 35b at the upper mid-point feed position. Alternatively, the portion of stream 39 may follow any or all flow paths described so far and shown in FIG. 5.

Disposal of the remaining gas stream after recovery of the liquid by-product stream (stream 43 in FIGS. 1 and 6-10) before being fed to the heat exchanger 60 for condensation and subcooling can be accomplished in a number of ways. have. In the process of FIG. 1, the stream is heated, compressed to higher pressure using energy from one or more work expanders, partially cooled in a discharge chiller, and then further cooled in exchange with the source stream. . As shown in FIG. 6, some applications may benefit from compressing the stream to higher pressure, for example using a supplemental compressor 59 driven by an external power source. As illustrated by the equipment indicated by dashed lines in FIG. 1 (heat exchanger 24 and discharge cooler 25), some situations may be achieved by reducing or excluding precooling of the compressed stream before entering the heat exchanger 60. It may be advantageous to reduce the cost of payment of the facility (in terms of increasing the cooling load on the heat exchanger 60 and increasing the power consumption rate of the refrigerant compressors 64, 66, 68). In such a case, the stream 49a leaving the compressor may flow directly to the heat exchanger 24 as shown in FIG. 7, or directly to the heat exchanger 60 as shown in FIG. 8. If one expander is not used to expand some of the high pressure feed gas, a compressor driven by an external power source, such as compressor 59 shown in FIG. 9, may be used instead of compressor 16. The other situation cannot justify the compression of the stream at all, so that the stream is shown in dashed lines in FIG. 10 and in the equipment shown in FIG. 1 (heat exchanger 24, compressor 16 and discharge cooler 25). Flows directly into the heat exchanger (60). If the heat exchanger 24 is not contained to heat the stream prior to the withdrawal of the plant fuel gas (stream 48), the supplemental heater 58, as shown in Figs. Using a utility stream or other process stream to supply, it may be necessary to warm the fuel gas prior to consumption of the fuel gas. This choice should generally be assessed for each application, since factors such as gas composition, plant size, recovery level of the desired by-product stream, and available equipment must all be considered.

According to the invention, cooling of the feed stream and the inlet gas stream into the LNG production compartment can be achieved in a number of ways. 1 and 5 to 10, the inlet gas stream 31 is cooled and condensed by an external refrigerant stream and flashed separator liquid. However, a low temperature process stream can also be used for the supply of part of the cooling to the high pressure refrigerant (stream 71a). In addition, any stream at a lower temperature than the stream (s) being cooled may be used. For example, a side draw of steam from fractionation tower 19 can be withdrawn and used for cooling. The use and distribution of tower liquids and / or vapors in the heat exchange process and the specific arrangement of the heat exchangers in the inlet and feed gas cooling are evaluated for each specific use and the selection of the process stream in a particular heat exchange service. Should be. The choice of cooling source will depend on a number of factors, including but not limited to the composition and condition of the feed gas, the size of the installation, the size of the heat exchanger, the temperature of the potential cooling source, and the like. Those skilled in the art will also appreciate that cooling methods or any combination of the above cooling sources may be used in combination to achieve the desired temperature (s) of the feed stream.

In addition, additional external cooling supplied to the inlet gas stream and to the feed stream to the LNG production compartment can also be achieved in a number of other ways. 1 and 6 to 10, the boiling of single component refrigerant took on a high level of external cooling and the evaporation of the multi component refrigerant took on a low level of external cooling, where the single component refrigerant precooled the multi component refrigerant stream. Was used for. Alternatively, both high level and low level cooling may use a single component refrigerant (ie, "multistage cooling") that has a continuously lower boiling point, or one single component refrigerant of continuously lower evaporation pressure. Can be achieved. Alternatively, both high levels of cooling and low levels of cooling can be achieved using a multi-component refrigerant stream, wherein the individual composition of the stream is adjusted to provide the required cooling temperature. The choice of the method of providing external cooling includes, but is not limited to, the composition and condition of the feed gas, the size of the equipment, the size of the compressor driver, the size of the heat exchanger, the temperature of the ambient heat sink, and the like. It will depend on a number of factors. Those skilled in the art will also appreciate that any combination of the above methods of providing external cooling can be used in combination to achieve the desired temperature (s) of the feed stream.

Condensed liquid stream leaving heat exchanger 60 (stream 49d in FIG. 1, stream 49e in FIG. 6, stream 49c in FIG. 7, stream 49b in FIGS. 8 and 9, and FIG. 10) The subcooling of stream 49a) reduces or eliminates the amount of flash steam that may be generated during expansion of the stream to the operating pressure of the LNG storage tank 62. This generally reduces the specific power consumption in LNG production by eliminating the need for flash gas compression. However, some situations may be advantageous to reduce the installation expense of the facility by reducing the size of the heat exchanger 60 and to remove all flash gas that may be generated using flash gas compression or other means.

Although expansion of the individual streams is shown in a particular expansion device, alternative expansion means may be used where appropriate. For example, conditions may ensure a one expansion of the substantially condensed feed stream (stream 35a in FIGS. 1 and 5-10). In addition, a subcooled liquid stream in which isoenthalpy flash expansion leaves heat exchanger 60 (stream 49d in FIG. 1, stream 49e in FIG. 6, stream 49c in FIG. 7, streams in FIGS. 8 and 9) 49b), and stream 49a in FIG. 10, may be used instead of one expansion, but requires more subcooling in the heat exchanger 60 to avoid the formation of flash steam in the expansion, or otherwise It requires the addition of flash steam compression or other means for removal of the generated flash steam. Similarly, an isenthalpy flash expansion can be used instead of thermal expansion in the subcooled high pressure refrigerant stream leaving the heat exchanger 60 (stream 71c in FIGS. 1 and 6-10), resulting in compression of the refrigerant. The power consumption rate for this is increased.

Although what has been described as what is believed to be the preferred embodiments of the present invention, those skilled in the art can make other additional modifications to the invention without departing from the spirit of the invention as defined by the following claims, for example, by the present invention. It will be appreciated that variations may be made to suit various conditions, types of feed, or other requirements.

The present invention relates to a process for treating natural gas or other methane-rich gas streams to produce liquefied natural gas (LNG) streams with high methane purity and liquid streams containing primarily hydrocarbons heavier than methane. . According to the present invention, careful integration of the hydrocarbon removal step into the LNG liquefaction process enables the production of both LNG and individual heavier liquid hydrocarbon products with significantly less energy than prior art processes. The invention can be applied at lower pressures, but is particularly advantageous when treating feed gases in the range of 400 to 1500 psia [2,758 to 10,342 kPa (a)] or higher.

Claims (78)

In the liquefaction process of a natural gas stream containing methane and heavier hydrocarbon components, (a) said natural gas stream is cooled under pressure to condense at least a portion thereof to form a condensed stream; (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream, (1) treating said natural gas stream in one or more cooling stages; (2) dividing the cooled natural gas stream into at least a first gaseous stream and a second gaseous stream; (3) cooling the first gaseous stream to condense substantially all of it and then expand to medium pressure; (4) directing the expanded substantially condensed first gaseous stream in a heat exchange relationship with a more volatile vapor distillation stream rising from the fractionation stage of the distillation column, thereby warming it; (5) expanding the second gaseous stream to the intermediate pressure; (6) directing said warmed and expanded first gaseous stream and said expanded second gaseous stream into said distillation column, wherein said stream is the majority of said more volatile vapor distillation stream and said heavy hydrocarbon component. Separated into relatively less volatile fractions containing; (7) said more volatile vapor distillation stream is cooled sufficiently by said expanded substantially condensed first gaseous stream to partially condense it, and then separated to volatile containing most of said methane and light components. Forming residual gas fraction and reflux stream; (8) directing the reflux stream into the distillation column as a top feed; Also (9) A process having improvement in cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby forming said condensed stream. In the liquefaction process of a natural gas stream containing methane and heavy hydrocarbon components, (a) said natural gas stream is cooled under pressure to condense at least a portion thereof to form a condensed stream; (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream, (1) treating the natural gas stream in one or more cooling stages to partially condense it; (2) providing a vapor stream and a liquid stream by separating the partially condensed natural gas stream; (3) dividing the vapor stream into at least a first gaseous stream and a second gaseous stream; (4) cooling the first gaseous stream to condense substantially all of it and then expand to medium pressure; (5) directing the expanded, substantially condensed first gaseous stream in a heat exchange relationship with a more volatile vapor distillation stream rising from the fractionation stage of the distillation column, thereby warming it; (6) expanding the second gaseous stream to the intermediate pressure; (7) expanding the liquid stream to the intermediate pressure; (8) directing the warmed and expanded first gaseous stream, the expanded second gaseous stream, and the expanded liquid stream into the distillation column, wherein the stream is the more volatile vapor distillation Separated into a relatively less volatile fraction containing the stream and most of the heavy hydrocarbon component; (9) said more volatile vapor distillation stream is cooled sufficiently by said expanded substantially condensed first gaseous stream to partially condense it, and then separated to volatile containing most of said methane and light components. Forming residual gas fraction and reflux stream; (10) directing the reflux stream into the distillation column as a top feed; Also (11) A process having improvement in cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby forming said condensed stream. In the liquefaction process of a natural gas stream containing methane and heavy hydrocarbon components, (a) said natural gas stream is cooled under pressure to condense at least a portion thereof to form a condensed stream; (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream, (1) treating the natural gas stream in one or more cooling stages to partially condense it; (2) providing a vapor stream and a liquid stream by separating the partially condensed natural gas stream; (3) dividing the vapor stream into at least a first gaseous stream and a second gaseous stream; (4) combining the first gaseous stream with at least a portion of the liquid stream to form a combined stream; (5) cooling the combined stream to condense substantially all of it and then expand to medium pressure; (6) directing the expanded, substantially condensed and combined stream to a heat exchange relationship with a more volatile vapor distillation stream rising from the fractionation stage of the distillation column, thereby warming it; (7) expanding the second gaseous stream to the intermediate pressure; (8) inflate all remaining portions of the liquid stream to the intermediate pressure; (9) directing the warmed, expanded and combined stream, the expanded second gaseous stream, and the expanded remainder of the liquid stream into the distillation column, wherein the stream is the more volatile vapor Separated into a distillation stream and a relatively less volatile fraction containing most of the heavy hydrocarbon component; (10) The more volatile vapor distillation stream is cooled sufficiently by the expanded, substantially condensed combined stream to partially condense it and then separate to separate the volatile residual gas fraction containing most of the methane and light components. And forming a reflux stream; (11) directing the reflux stream into the distillation column as a top feed; Also (12) A process having an improvement in cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby forming said condensed stream. In the liquefaction process of a natural gas stream containing methane and heavy hydrocarbon components, (a) said natural gas stream is cooled under pressure to condense at least a portion thereof to form a condensed stream; (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream, (1) treating the natural gas stream in one or more cooling stages to partially condense it; (2) providing a vapor stream and a liquid stream by separating the partially condensed natural gas stream; (3) dividing the vapor stream into at least a first gaseous stream and a second gaseous stream; (4) cooling the first gaseous stream to condense substantially all of it and then expand to medium pressure; (5) directing the expanded, substantially condensed first gaseous stream in a heat exchange relationship with a more volatile vapor distillation stream rising from the fractionation stage of the distillation column, thereby warming it; (6) expanding the second gaseous stream to the intermediate pressure; (7) cool the liquid stream and then divide it into at least a first portion and a second portion; (8) expanding the first portion to the intermediate pressure and then warming up; (9) inflating said second portion to said intermediate pressure; (10) directing said warmed and expanded first gaseous stream, said expanded second gaseous stream, said warmed and expanded first portion, and said expanded second portion into said distillation column, wherein The stream is separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing most of the heavy hydrocarbon component; (11) said more volatile vapor distillation stream is cooled sufficiently by said expanded substantially condensed first gaseous stream to partially condense it, and then separated to volatile containing most of said methane and light components. Forming residual gas fraction and reflux stream; (12) directing the reflux stream into the distillation column as a top feed; Also (13) A process having an improvement in cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby forming said condensed stream. In the liquefaction process of a natural gas stream containing methane and heavy hydrocarbon components, (a) said natural gas stream is cooled under pressure to condense at least a portion thereof to form a condensed stream; (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream, (1) treating the natural gas stream in one or more cooling stages to partially condense it; (2) providing a vapor stream and a liquid stream by separating the partially condensed natural gas stream; (3) dividing the vapor stream into at least a first gaseous stream and a second gaseous stream; (4) cooling the first gaseous stream to condense substantially all of it; (5) cool the liquid stream and then divide it into at least a first portion and a second portion; (6) expanding the first portion to medium pressure and then warming up; (7) combining the second portion with the substantially condensed first gaseous stream to form a combined stream, and then expanding the combined stream to the intermediate pressure; (8) directing said expanded and combined stream to a heat exchange relationship with a more volatile vapor distillation stream rising from the fractionation stage of the distillation column and thereby warming it; (9) expanding the second gaseous stream to the intermediate pressure; (10) directing the warmed, expanded and combined stream, the expanded second gaseous stream, and the warmed, expanded first portion into the distillation column, wherein the stream is the more volatile vapor Separated into a distillation stream and a relatively less volatile fraction containing most of the heavy hydrocarbon component; (11) said more volatile vapor distillation stream is cooled sufficiently by said expanded combined stream to partially condense it, and then separated to separate volatile residual gas fraction and reflux stream containing most of the methane and light components. To form; (12) directing the reflux stream into the distillation column as a top feed; Also (13) A process having an improvement in cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby forming said condensed stream. The distillation column of claim 1 wherein the distillation column is a bottom compartment of the fractionation column and the more volatile vapor distillation stream is sufficiently cooled in the tower portion above the distillation column to partially condense it and simultaneously separate the volatile residual gas. Fraction and forming the reflux stream, wherein the reflux stream has the improvement of flowing to the top fractionation stage of the distillation column. The distillation column according to claim 2, wherein the distillation column is the lower compartment of the fractionation column and the more volatile vapor distillation stream is cooled sufficiently in the tower portion above the distillation column to partially condense it and simultaneously separate it to separate the volatile residual gas. Fraction and forming the reflux stream, wherein the reflux stream has the improvement of flowing to the top fractionation stage of the distillation column. 4. The distillation column of claim 3, wherein the distillation column is a lower compartment of the fractionation column, and the more volatile vapor distillation stream is sufficiently cooled in the tower portion above the distillation column to partially condense it and simultaneously separate the volatile residual gas Fraction and forming the reflux stream, wherein the reflux stream has the improvement of flowing to the top fractionation stage of the distillation column. The distillation column of claim 4, wherein the distillation column is a lower compartment of the fractionation column, and the more volatile vapor distillation stream is sufficiently cooled in the tower portion above the distillation column to partially condense it and simultaneously separate to separate the volatile residual gas. Fraction and forming the reflux stream, wherein the reflux stream has the improvement of flowing to the top fractionation stage of the distillation column. The distillation column according to claim 5, wherein the distillation column is a bottom compartment of the fractionation column, and the more volatile vapor distillation stream is cooled sufficiently in the tower portion above the distillation column to partially condense it and simultaneously separate to separate the volatile residual gas. Fraction and forming the reflux stream, wherein the reflux stream has the improvement of flowing to the top fractionation stage of the distillation column. The method of claim 1, wherein the more volatile vapor distillation stream is sufficiently cooled in a condenser to partially condense it and at the same time separate to form the volatile residual gas fraction and the reflux stream, after which the reflux stream is condenser. Process with flows from the distillation column to the top fractionation stage. The method of claim 2, wherein the more volatile vapor distillation stream is sufficiently cooled in a condenser to partially condense it and simultaneously separate to form the volatile residual gas fraction and the reflux stream, after which the reflux stream is condenser. Process with flows from the distillation column to the top fractionation stage. The method of claim 3, wherein the more volatile vapor distillation stream is sufficiently cooled in a condenser to partially condense it and simultaneously separate to form the volatile residual gas fraction and the reflux stream, after which the reflux stream is condenser. Process with flows from the distillation column to the top fractionation stage. The method of claim 4, wherein the more volatile vapor distillation stream is sufficiently cooled in a condenser to partially condense it and simultaneously separate to form the volatile residual gas fraction and the reflux stream, after which the reflux stream is condenser. Process with flows from the distillation column to the top fractionation stage. The method of claim 5, wherein the more volatile vapor distillation stream is sufficiently cooled in a condenser to partially condense it and simultaneously separate to form the volatile residual gas fraction and the reflux stream, after which the reflux stream is condenser. Process with flows from the distillation column to the top fractionation stage. The process according to claim 1, wherein the process has the improvement of compressing the volatile residual gas fraction and then cooling under pressure to condense at least a portion thereof, thereby forming the condensed stream. The improvement according to any one of claims 1 to 15, wherein the volatile residual gas fraction is heated, compressed and then cooled under pressure to condense at least a portion thereof, thereby forming the condensed stream. fair. The process of claim 1, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, and C ₂ component. The process of claim 16, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, and C ₂ component. 18. The process of claim 17, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, and C ₂ component. The process of claim 1, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, C ₂ component, and C ₃ component. 17. The process of claim 16, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, C ₂ component, and C ₃ component. 18. The process of claim 17, wherein the volatile residual gas fraction has an improvement containing most of the methane, light component, C ₂ component, and C ₃ component. Apparatus for the liquefaction of natural gas streams containing methane and heavy hydrocarbon components, (1) at least one first heat exchange means for receiving said natural gas stream and cooling it under pressure; (2) dividing means connected to said first heat exchange means to receive said cooled natural gas stream and divide it into at least a first gaseous stream and a second gaseous stream; (3) second heat exchange means connected to said dividing means to receive said first gaseous stream and cool it sufficiently to substantially condense it; (4) first expansion means connected to said second heat exchange means to receive said substantially condensed first gaseous stream and expand it to medium pressure; (5) third heat exchange means connected to said first expansion means to receive and heat said expanded substantially condensed first gaseous stream, said third heat exchange means being further connected to a distillation column to Third heat exchange means for receiving a more volatile vapor distillation stream rising from the fractionation stage of and cooling it sufficiently to partially condense it; (6) second expansion means connected to said dividing means to receive said second gaseous stream and expand it to said intermediate pressure; (7) said distillation column, said distillation column further connected to said third heat exchange means and said second expansion means to receive said heated and expanded first gaseous stream and said expanded second gaseous stream; A distillation column suitable for separating the stream into a more volatile vapor distillation stream and a relatively less volatile fraction containing most of the heavy hydrocarbon component; (8) separation means connected to said third heat exchange means to receive said cooled, partially condensed distillation stream and separate it into a volatile residual gas fraction and reflux stream containing most of said methane and light components, said separation The means further comprises separating means connected to said distillation column to direct said reflux stream into said distillation column as a top feed; (9) fourth heat exchange means connected to said separation means to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fourth heat exchange means suitable for forming; (10) third expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; And (11) suitable for maintaining the overhead temperature of the distillation column to maintain the temperature at which the majority of the heavy hydrocarbon components are recovered in the relatively less volatile fraction to adjust the amount and temperature of the feed stream to the distillation column. Control means Device comprising a. Apparatus for the liquefaction of natural gas streams containing methane and heavy hydrocarbon components, (1) at least one first heat exchange means for receiving said natural gas stream and cooling it sufficiently under pressure to partially condense it; (2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream; (3) dividing means connected to said first separating means to receive said vapor stream and divide it into at least a first gaseous stream and a second gaseous stream; (4) second heat exchange means connected to said dividing means to receive said first gaseous stream and cool it sufficiently to substantially condense it; (5) first expansion means connected to said second heat exchange means to receive said substantially condensed first gaseous stream and expand it to medium pressure; (6) third heat exchange means connected to said first expansion means to receive said heated and substantially condensed first gaseous stream and to heat it, said third heat exchange means being further connected to a distillation column to Third heat exchange means for receiving a more volatile vapor distillation stream rising from the fractionation stage of and cooling it sufficiently to partially condense it; (7) second expansion means connected to said dividing means to receive said second gaseous stream and expand it to said intermediate pressure; (8) third expansion means connected to said first separating means to receive said liquid stream and expand it to said intermediate pressure; (9) said heated and expanded first gaseous stream, said expanded second gaseous stream, and said expansion further connected to said third heat exchange means, said second expansion means, and said third expansion means. Said distillation column containing a purified liquid stream, said distillation column comprising a distillation column suitable for separating said stream into said less volatile vapor distillation stream and a relatively less volatile fraction containing most of said heavy hydrocarbon component; (10) second separation means connected to said third heat exchange means to receive said cooled, partially condensed distillation stream and separate it into a volatile residual gas fraction and reflux stream containing most of said methane and light components, The second separation means further connected to the distillation column to direct the reflux stream into the distillation column as a top feed; (11) fourth heat exchange means connected to said second separating means to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby condensing Fourth heat exchange means suitable for forming an integrated stream; (12) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; And (14) The overhead temperature of the distillation column is maintained at a temperature at which most of the heavy hydrocarbon components are recovered in the relatively less volatile fractions so as to adjust the amount and temperature of the feed stream to the distillation column. Suitable control means Device comprising a. Apparatus for the liquefaction of natural gas streams containing methane and heavy hydrocarbon components, (1) at least one first heat exchange means for receiving said natural gas stream and cooling it sufficiently under pressure to partially condense it; (2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream; (3) dividing means connected to said first separating means to receive said vapor stream and divide it into at least a first gaseous stream and a second gaseous stream; (4) combining means connected to said dividing means and said first separating means to receive at least a portion of said first gaseous stream and said liquid stream and thereby form a combined stream; (5) second heat exchange means connected to said combining means to receive said combined stream and cool it sufficiently to substantially condense it; (6) first expansion means connected to said second heat exchange means to receive said substantially condensed and combined stream and expand it to medium pressure; (7) third heat exchange means connected to said first expansion means to receive and heat said expanded and substantially condensed combined stream, said third heat exchange means being further connected to a distillation column to Third heat exchange means for receiving a more volatile vapor distillation stream rising from the fractionation stage and cooling it sufficiently to partially condense it; (8) second expansion means connected to said dividing means to receive said second gaseous stream and expand it to said intermediate pressure; (9) third expansion means connected to said first separating means to receive all remaining portions of said liquid stream and expand it to said intermediate pressure; (10) expansion of said heated, expanded and combined stream, said expanded second gaseous stream, and said liquid stream further connected to said third heat exchange means, said second expansion means, and said third expansion means. A distillation column containing the remaining portion, wherein the distillation column is a distillation column suitable for separating the stream into a relatively less volatile fraction containing most of the more volatile vapor distillation stream and the heavy hydrocarbon component; (11) second separation means connected to said third heat exchange means to receive said cooled, partially condensed distillation stream and separate it into a volatile residual gas fraction and reflux stream containing most of said methane and light components, The second separation means further connected to the distillation column to direct the reflux stream into the distillation column as a top feed; (12) fourth heat exchange means connected to said second separating means to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fourth heat exchange means suitable for forming a condensation stream; (13) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; And (14) The overhead temperature of the distillation column is adapted to be maintained at a temperature at which the majority of the heavy hydrocarbon components are recovered in the relatively less volatile fractions so as to adjust the amount and temperature of the feed stream to the distillation column. Control means Device comprising a. Apparatus for the liquefaction of natural gas streams containing methane and heavy hydrocarbon components, (1) at least one first heat exchange means for receiving said natural gas stream and cooling it sufficiently under pressure to partially condense it; (2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream; (3) second heat exchange means connected to said first separating means to receive said liquid stream and cool it; (4) first dividing means connected to said second heat exchange means to receive said cooled liquid stream and divide it into at least a first portion and a second portion; (5) first expansion means connected to said first dividing means to receive said first portion and expand it to medium pressure, said first expansion means supplying said expanded first portion to said second heat exchange means; First expansion means for heating said expanded first portion while cooling said liquid stream; (6) second dividing means connected to said first separating means to receive said vapor stream and divide it into at least a first gaseous stream and a second gaseous stream; (7) third heat exchange means connected to said second dividing means to receive said first gaseous stream and cool it sufficiently to substantially condense it; (8) second expansion means connected to said third heat exchange means to receive said substantially condensed first gaseous stream and expand it to said intermediate pressure; (9) third expansion means connected to said second dividing means to receive said second gaseous stream and expand it to said intermediate pressure; (10) fourth expansion means connected to said first dividing means to receive said second portion and expand it to said intermediate pressure; (11) fourth heat exchange means connected to said second expansion means to receive and heat said expanded substantially condensed first gaseous stream, Said fourth heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from the fractionation stage of said distillation column and cool it sufficiently to partially condense it; (12) said heated and expanded first gaseous stream, said expanded second gaseous phase further connected to said fourth heat exchange means, said third expansion means, said fourth expansion means, and said second heat exchange means. The distillation column containing the stream, the expanded second portion, and the heated and expanded first portion, the distillation column may be used to direct the stream to the more volatile vapor distillation stream and the heavy hydrocarbon component. Distillation columns suitable for separation into relatively less volatile fractions containing; (13) second separation means connected to said fourth heat exchange means to receive said cooled, partially condensed distillation stream and separate it into a volatile residual gas fraction and reflux stream containing most of said methane and light components, The second separation means further connected to the distillation column to direct the reflux stream into the distillation column as a top feed; (14) fifth heat exchange means connected to said second separating means to receive said volatile residual gas fraction, said fifth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby condensing Fifth heat exchange means suitable for forming an integrated stream; (15) fifth expansion means connected to said fifth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; And (16) The overhead temperature of the distillation column is maintained at a temperature at which the majority of the heavy hydrocarbon components are recovered in the relatively less volatile fraction to adjust the amount and temperature of the feed stream to the distillation column. Suitable control means Device comprising a. Apparatus for the liquefaction of natural gas streams containing methane and heavy hydrocarbon components, (1) at least one first heat exchange means for receiving said natural gas stream and cooling it sufficiently under pressure to partially condense it; (2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream; (3) second heat exchange means connected to said first separating means to receive said liquid stream and cool it; (4) first dividing means connected to said second heat exchange means to receive said cooled liquid stream and divide it into at least a first portion and a second portion; (5) first expansion means connected to said first dividing means to receive said first portion and expand it to medium pressure, said first expansion means supplying said expanded first portion to said second heat exchange means; First expansion means for heating said expanded first portion while cooling said liquid stream; (6) second dividing means connected to said first separating means to receive said vapor stream and divide it into at least a first gaseous stream and a second gaseous stream; (7) third heat exchange means connected to said second dividing means to receive said first gaseous stream and cool it sufficiently to substantially condense it; (8) combining means connected to said third heat exchange means and said first dividing means to receive said substantially condensed first gaseous stream and said second portion and thereby form a combined stream; (9) second expansion means connected to said combining means to receive said combined stream and expand it to said intermediate pressure; (10) third expansion means connected to said second dividing means to receive said second gaseous stream and expand it to said intermediate pressure; (11) fourth heat exchange means connected to said second expansion means to receive and heat said expanded and combined streams, said fourth heat exchange means being further connected to a distillation column to ascend from the fractionation stage of said distillation column Fourth heat exchange means for receiving the more volatile vapor distillation stream and cooling it sufficiently to partially condense it; (12) further connected to the fourth heat exchange means, the third expansion means, and the second heat exchange means to the heated, expanded and combined stream, the expanded second gaseous stream, and the heated and expanded A distillation column containing a first portion of the distillation column, the distillation column comprising a distillation column suitable for separating the stream into a relatively less volatile fraction containing most of the more volatile vapor distillation stream and the heavy hydrocarbon component; (13) second separation means connected to said fourth heat exchange means to receive said cooled, partially condensed distillation stream and separate it into a volatile residual gas fraction and reflux stream containing most of said methane and light components, The second separation means further connected to the distillation column to direct the reflux stream into the distillation column as a top feed; (14) fifth heat exchange means connected to said second separating means to receive said volatile residual gas fraction, said fifth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby condensing Fifth heat exchange means suitable for forming a stream; (15) fourth expansion means connected to said first fifth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; And (16) suitable for maintaining the overhead temperature of the distillation column to maintain the temperature at which the majority of the heavy hydrocarbon components are recovered in the relatively less volatile fractions so as to adjust the amount and temperature of the feed stream to the distillation column. Control means Device comprising a. The method of claim 24, (1) said distillation column is the lower section of the fractionation column, and said more volatile vapor distillation stream is cooled sufficiently in said fractionation column section above said distillation column to partially condense it, and at the same time separates the volatile residue A gas fraction and the reflux stream are formed, and then the reflux stream flows to the top fractionation stage of the distillation column; (2) said fourth heat exchange means being connected to said fractionation column to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Suitable for forming a condensed stream Device. The method according to claim 25, (1) said distillation column is the lower section of the fractionation column, and said more volatile vapor distillation stream is sufficiently cooled in said fractionation column section above said distillation column to partially condense it, and at the same time separates said volatile residue A gas fraction and the reflux stream are formed, and then the reflux stream flows to the top fractionation stage of the distillation column; (2) said fourth heat exchange means being connected to said fractionation column to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Suitable for forming a condensed stream Device. The method of claim 26, (1) said distillation column is the lower section of the fractionation column, and said more volatile vapor distillation stream is sufficiently cooled in said fractionation column section above said distillation column to partially condense it, and at the same time separates said volatile residue A gas fraction and the reflux stream are formed, and then the reflux stream flows to the top fractionation stage of the distillation column; (2) said fourth heat exchange means being connected to said fractionation column to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof and thereby condensing said Suitable for forming a stream Device. The method of claim 27, (1) said distillation column is the lower section of the fractionation column, and said more volatile vapor distillation stream is sufficiently cooled in said fractionation column section above said distillation column to partially condense it, and at the same time separates said volatile residue A gas fraction and the reflux stream are formed, and then the reflux stream flows to the top fractionation stage of the distillation column; (2) said fifth heat exchange means being connected to said fractionation column to receive said volatile residual gas fraction, said fifth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Suitable for forming the condensed stream Device. The method according to claim 28, (1) said distillation column is the lower section of the fractionation column, and said more volatile vapor distillation stream is sufficiently cooled in said fractionation column section above said distillation column to partially condense it, and at the same time separate and separate said volatile residue A gas fraction and the reflux stream are formed, and then the reflux stream flows to the top fractionation stage of the distillation column; (2) said fifth heat exchange means being connected to said fractionation column to receive said volatile residual gas fraction, said fifth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Suitable for forming a condensed stream Device. The device of claim 24, wherein the device is (1) a condenser connected to said first expansion means to receive said heated substantially condensed first gaseous stream and to heat it, said condenser further connected to said distillation column to provide said more volatile vapor Receives the distillation stream and cools it sufficiently to partially condense it, and at the same time separates it to form the volatile residual gas fraction and the reflux stream, the condenser is further connected to the distillation column and heated A condenser that feeds the expanded first gaseous stream as a feed and the reflux stream as a top feed; And (2) said fourth heat exchange means connected to said condenser to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fourth heat exchange means suitable for forming the condensed stream Device comprising a. The device of claim 25, wherein the device is (1) a condenser connected to said first expansion means to receive said heated substantially condensed first gaseous stream and to heat it, said condenser further connected to said distillation column to provide said more volatile vapor Receives the distillation stream and cools it sufficiently to partially condense it, and at the same time separates it to form the volatile residual gas fraction and the reflux stream, the condenser is further connected to the distillation column and heated A condenser that feeds the expanded first gaseous stream as a feed and the reflux stream as a top feed; And (2) said fourth heat exchange means connected to said condenser to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fourth heat exchange means suitable for forming a condensed stream of water Device comprising a. The device of claim 26, wherein the device is (1) a condenser connected to said first expansion means to receive said heated, substantially condensed combined gaseous stream and heating said condenser, said condenser being further connected to said distillation column to Receives the vapor distillation stream and cools it sufficiently to partially condense it, and at the same time separates it to form the volatile residual gas fraction and the reflux stream, the condenser is further connected to the distillation column to heat the A condenser for supplying the expanded expanded combined stream as a feed and the reflux stream as a top feed; And (2) said fourth heat exchange means connected to said condenser to receive said volatile residual gas fraction, said fourth heat exchange means cooling said volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fourth heat exchange means suitable for forming the condensed stream Device comprising a. The device of claim 27, wherein the device is (1) a condenser connected to said second expansion means to receive said heated substantially condensed first gaseous stream and to heat it, said condenser further connected to said distillation column to provide said more volatile vapor Receives the distillation stream and cools it sufficiently to partially condense it, and at the same time separates it to form the volatile residual gas fraction and the reflux stream, the condenser is further connected to the distillation column and heated A condenser for supplying the expanded first gaseous stream as a feed and the reflux stream as a top feed; And (2) the fifth heat exchange means connected to the condenser to receive the volatile residual gas fraction, the fifth heat exchange means to cool the volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fifth heat exchange means suitable for forming a condensed stream Device comprising a. The device of claim 28, wherein the device is (1) a condenser connected to said second expansion means to receive said heated and combined stream and heating said condenser, said condenser further connected to said distillation column to receive said more volatile vapor distillation stream and Cooling sufficiently to partially condense it, and at the same time separate it to form the volatile residual gas fraction and the reflux stream, wherein the condenser is further connected to the distillation column to supply the heated and expanded combined stream A condenser that supplies water and the reflux stream as a top feed; And (2) the fifth heat exchange means connected to the condenser to receive the volatile residual gas fraction, the fifth heat exchange means to cool the volatile residual gas fraction under pressure to condense at least a portion thereof, thereby Fifth heat exchange means suitable for forming a condensed stream Device comprising a. The device of claim 24, wherein the device is (1) compression means connected to said separation means to receive said volatile residual gas fraction and to compress it; And (2) said fourth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fourth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof Fourth heat exchange means suitable for forming said condensed stream thereby Device comprising a. 27. The device of claim 25 or 26, wherein the device is (1) compression means connected to said second separating means to receive said volatile residual gas fraction and to compress it; And (2) said fourth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fourth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof Fourth heat exchange means suitable for forming said condensed stream thereby Device comprising a. 29. The device of claim 27 or 28, wherein the device is (1) compression means connected to said second separating means to receive said volatile residual gas fraction and to compress it; And (2) said fifth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fifth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof And heat exchange means suitable for forming said condensed stream thereby. Device comprising a. 32. The device of claim 29, wherein the device is (1) compression means connected to said fractionation column to receive said volatile residual gas fraction and to compress it; And (2) said fourth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fourth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof Fourth heat exchange means suitable for forming said condensed stream thereby Device comprising a. The device of claim 32 or 33, wherein the device is (1) compression means connected to said fractionation column to receive said volatile residual gas fraction and to compress it; And (2) said fifth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fifth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof And heat exchange means suitable for forming said condensed stream thereby. Device comprising a. The apparatus of claim 34, wherein the device is (1) compression means connected to the condenser to receive and compress the volatile residual gas fraction; And (2) said fourth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fourth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof Fourth heat exchange means suitable for forming said condensed stream thereby Device comprising a. The device of claim 37 or 38, wherein the device is (1) compression means connected to the condenser to receive and compress the volatile residual gas fraction; And (2) said fifth heat exchange means connected to said compression means to receive said compressed volatile residual gas fraction, said fifth heat exchange means cooling said compressed volatile residual gas fraction under pressure to condense at least a portion thereof And heat exchange means suitable for forming said condensed stream thereby. Device comprising a. The device of claim 24, wherein the device is (1) heating means connected to said separating means to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fourth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fourth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fourth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. 27. The device of claim 25 or 26, wherein the device is (1) heating means connected to said second separating means to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fourth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fourth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fourth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. 29. The device of claim 27 or 28, wherein the device is (1) heating means connected to said second separating means to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fifth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fifth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fifth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. 32. The device of claim 29, wherein the device is (1) heating means connected to said fractionation tower to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fourth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fourth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fourth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. The device of claim 32 or 33, wherein the device is (1) heating means connected to said fractionation tower to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fifth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fifth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fifth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. The apparatus of claim 34, wherein the device is (1) heating means connected to said condenser to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fourth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fourth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fourth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. The device of claim 37 or 38, wherein the device is (1) heating means connected to said condenser to receive said volatile residual gas fraction and to heat it; (2) compression means connected to said heating means to receive said compressed volatile residual gas fraction and to compress it; And (3) said fifth heat exchange means connected to said compression means to receive said compressed heated volatile residual gas fraction, said fifth heat exchange means cooling said compressed heated volatile residual gas fraction under pressure to Fifth heat exchange means suitable for condensing at least a portion, thereby forming said condensed stream Device comprising a. 49. The device of any of claims 24 to 39 or 46, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The apparatus of claim 40, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The apparatus of claim 41, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. 43. The device of claim 42, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The apparatus of claim 43, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 44, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. 46. The apparatus of claim 45, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. 48. The device of claim 47, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 48, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 49, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 50, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 51, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. The device of claim 52, wherein the volatile residual gas fraction contains most of the methane, light component, and C ₂ component. 49. The device of any of claims 24 to 39 or 46, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 41. The apparatus of claim 40, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 42. The device of claim 41, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 43. The apparatus of claim 42, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. The device of claim 43, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 45. The apparatus of claim 44, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. The device of claim 45, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 48. The device of claim 47, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 49. The device of claim 48, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. The device of claim 49, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. 51. The apparatus of claim 50, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. The device of claim 51, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component. The device of claim 52, wherein the volatile residual gas fraction contains most of the methane, light component, C ₂ component, and C ₃ component.

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