RU2620601C2 - Method of obtaining natural gas processed, fraction enriched by c3+ - hydrocarbons, and, optionally, flow enlarged by ethan, and also, installation appropriate for this method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method comprises the following steps: selecting a recycle stream in the upper stream exiting the separation column; establishing a certain heat exchange interaction between the recycle stream and at least one portion of the overhead stream exiting the separation column; repeated administration, after expansion, of the cooled and expanded recycle stream into the isolation column; selecting, in the bottom of the column, the separation of at least one reboiling bottoms stream and providing heat exchange between the re-boiling stream and at least one portion of the feed natural gas and/or with the recycle stream. The re-boiling of the bottom liquid is provided by calories absorbed from the original natural gas stream and/or the recycle stream. The invention also relates to a device.

EFFECT: invention allows to reduce power consumption.

15 cl, 6 dwg, 9 tbl

Description

The present invention relates to a method for the simultaneous production of treated natural gas, a fraction enriched in C ₃ ⁺ hydrocarbons, and, at least in certain production conditions, a stream enriched in ethane from a feed stream of natural gas containing methane, ethane and C ₃ ⁺ - hydrocarbons, where the specified method includes the following stages:

- the natural gas feed stream is cooled and partially condensed in at least one of the heat exchangers located upstream of the process stream to obtain a cooled feed stream;

- the cooled feed gas stream is separated into a liquid stream and a gas stream;

- the liquid stream is expanded and the stream formed from the specified liquid stream is introduced into the column to isolate C ₂ ⁺ hydrocarbons at the first intermediate level;

- a turbine power stream is formed from the gas stream;

- expand the resulting power flow in the dynamic expansion turbine and introduce it into the selection column at the second intermediate level;

- at least one part of the top stream of the recovery column is isolated and compressed to produce natural gas, and the bottom stream of the recovery column is also extracted;

- a liquid stream is introduced at the feed level of the fractionation column equipped with an upper condenser, while under the aforementioned production conditions an ethane-enriched stream is generated from the stream leaving the fractionation column, the fractionation column generating a lower stream intended to form, at least partially, fraction C ₃ ⁺ hydrocarbons;

- the primary reflux stream obtained in the upper condenser is introduced into the fractionation column;

- a secondary reflux stream is obtained from the upper condenser and a secondary reflux stream is introduced into the upper part of the recovery column.

This method is designed to process a natural gas stream in order to extract at least C ₃ ⁺ hydrocarbons from it in order to separate liquids and a controlled amount of C ₂ hydrocarbons from natural gas.

C ₂ and C ₃ ⁺ hydrocarbons are recovered from the source natural gas in order to avoid condensation during gas transportation and / or during certain gas operations. Such condensation can lead to the formation of fluid plugs in transport facilities, which negatively affects production. In addition, these hydrocarbons can be sold with significant commercial profit, which has a beneficial effect on the cost effectiveness of equipment.

Consequently, methods have been developed almost simultaneously extracting all the C ₃ ⁺ hydrocarbons present in the natural gas feed, and a significant proportion of the available ethane in the feed gas.

However, the demand for ethane on the market varies greatly, while the need for a fraction of C ₃ ⁺ hydrocarbons is relatively constant and is associated with significant benefits.

In view of the foregoing, in some cases it is necessary to reduce the production of ethane in the framework of this method by reducing the degree of extraction of this compound in the recovery column. In this case, the degree of extraction of C ₃ ⁺ hydrocarbons is also reduced, which reduces the economic efficiency of the equipment.

In order to overcome this problem, it is known to use double installations, i.e. It is known to include in the secondary block scheme optimized for obtaining C ₃ ⁺ hydrocarbons in the absence of ethane recovery. Such a secondary unit is expensive to operate and maintain.

US patent 7458232 discloses a solution to this problem by using a method that provides optimal recovery of C ₃ ⁺ hydrocarbons, typically more than 99%, and in which, nevertheless, the flexibility of adjusting the degree of ethane extraction, for example, from 2% to 85% depending on the composition of the gas supplied.

In view of the foregoing, the method described in US patent 7458232, is particularly effective and, at the same time, very flexible. However, with increasing ethane recovery, energy consumption also increases as a result of the use of compressors. Therefore, there is always a need to increase plant productivity. This is especially significant in the case of high degrees of ethane extraction.

The purpose of the present invention is to develop a method by which it is possible to flexibly control the degree of ethane extraction, which can be in the range up to 85%, with a marked reduction in the energy consumption of the installation.

In this regard, the purpose of this invention is to install the aforementioned type, characterized in that the process carried out therein includes the following steps:

- select the recycle stream in the upper stream exiting the allocation column;

- establish a heat transfer interaction between the recirculation stream and at least one part of the upper stream exiting the allocation column,

- after expansion, the cooled and expanded recycle stream is reintroduced into the recovery column;

however, this process involves the selection in the cube of the recovery column of at least one cubic stream of re-boiling and providing a certain heat exchange interaction of the cubic stream of re-boiling with at least one part of the source natural gas stream and / or with the recirculation stream, moreover, the re-boiling of the bottled liquid provided by calories absorbed from the source of natural gas stream and / or recycle stream.

The method according to the invention may include one or more of the following features, taken individually or in suitable technically possible combinations:

- at least one part of the upper stream of the recovery column and the recycle stream are introduced into a certain heat exchange interaction with the original natural gas stream and the still boiling bottoms stream;

- a recycle stream leaving the first heat exchanger located upstream of the process, a secondary reflux stream coming from the upper condenser, and an upper stream leaving the recovery column are introduced into a certain heat exchange interaction in the first upper heat exchanger;

- at least one side reflux stream is taken above the bottoms reflux stream, wherein said or each side reflux stream is introduced into heat exchange interaction with at least one part of the natural gas feed stream;

- the ethane-enriched stream is diverted from the intermediate level of the fractionation column located above the feed level of the column and below the upper level of the fractionation column;

- the method includes the following stages:

- divide the feed stream of natural gas into a first feed stream and a second feed stream;

- serves the first source stream to the first heat exchanger located upstream of the process stream;

- introducing at least one part of the second feed stream into an auxiliary dynamic expansion turbine to form an auxiliary reflux stream from the effluent from the auxiliary turbine;

- serves an auxiliary stream of reflux in the allocation column;

- at least one part of the recirculation stream is compressed in an auxiliary compressor associated with the auxiliary turbine;

at least one portion of the overhead stream is compressed in an auxiliary compressor mated to an auxiliary turbine, preferably between a first compressor mated to a first turbine and a second compressor;

- the method includes the step of compressing at least one part of the overhead stream in a first compressor mated to a first turbine, and then the step of compressing a partially compressed overhead stream in a second compressor, wherein the recirculation stream is taken downstream from the second compressor;

at least one secondary recycle stream is taken from the recycle stream, the secondary recycle stream being supplied to the secondary expansion turbine before being reintroduced into the upper stream, preferably upstream from the passage of the upper stream to the first heat exchanger located upstream of the process stream;

- the secondary reflux stream consists of a liquid, gas, or a mixture of liquid and gas originating from the top condenser of the fractionation column;

- the method includes the selection of the bypass stream from the recycle stream, and the bypass stream is re-introduced into the stream located upstream of the first dynamic expansion turbine;

- the liquid stream from the first separator vessel located upstream of the separator is expanded and introduced into the second separator vessel located upstream of the separator vessel to form a liquid fraction and a gas fraction,

moreover, the liquid fraction after expansion is introduced at the first intermediate level of the separation column, the gas fraction is introduced at the upper level of the separation column located above the intermediate level,

moreover, the liquid stream exiting the first separator vessel located upstream of the separator vessel is preferably introduced into a certain heat exchange interaction with the initial natural gas stream to heat it before being introduced into the second separator vessel located upstream of the invention;

- the method includes providing heat exchange between the lower stream flowing from the recovery column and the natural gas feed stream and the boiling stream in the first heat exchanger located upstream of the process stream before it is fed to the fractionation column;

- the gas stream leaving the first separator vessel is separated into a power stream and a reflux stream, while the power stream is designed to power a dynamic expansion turbine, and the reflux stream after cooling, partial or complete condensation and expansion in the valve is introduced together into the recovery column;

- the method includes the step of compressing the bottom stream exiting the separation column in the pump before it is introduced into the fractionation column;

- the method includes the step of cooling the secondary reflux stream by heat exchange with at least one part of the upper stream of the recovery column.

The aim of the present invention is also a facility for the simultaneous production of treated natural gas, a fraction enriched in C ₃ ⁺ hydrocarbons, and, at least in some production conditions, an ethane-enriched stream from a feed stream of natural gas containing methane, ethane and C ₃ ⁺ - hydrocarbons, where the installation contains:

- a cooling and partial condensing unit of a natural gas feed stream, comprising at least one first heat exchanger located upstream of the process stream for receiving a cooled feed stream;

- a unit for separating the cooled feed stream into a liquid stream and a gas stream;

- a column for the allocation of C ₂ ⁺ hydrocarbons;

- an expansion unit of a liquid stream for introducing a stream formed from the liquid stream into the recovery column at a first intermediate level;

- a gas flow forming unit for powering a turbine;

- node expansion of the power stream, including a dynamic expansion turbine, and a node for supplying the expanded power stream to the extraction column at the second intermediate level;

- a separation and compression unit for at least one part of the upper stream of the recovery column to produce natural gas and a separation unit of the lower stream of the recovery column to obtain a liquid stream enriched in C ₂ ⁺ hydrocarbons;

- fractionation column equipped with an upper condenser,

- a liquid flow supply unit at the feed level of the fractionation column, and under the mentioned conditions, an ethane-enriched stream can be obtained from the stream leaving the fractionation column, while a lower stream can be generated in the fractionation column to form at least a portion of fraction C ₃ ⁺ -hydrocarbons;

- a feed unit for the primary reflux stream obtained in the upper condenser into the fractionation column;

- a site for receiving a secondary reflux stream from an upper condenser and a feed unit for a secondary reflux stream to an upper part of a separation column,

and differs in that it includes:

- site selection recirculation flow in the upper stream of the separation column;

- a node for establishing heat transfer between the recirculation stream and at least one part of the upper stream exiting the separation column,

- a re-introduction unit, after expansion, of the recycle stream to the recovery column, wherein the described installation further includes a selection unit in the cube of the recovery column of at least one cubic re-boiling stream and a node for establishing heat exchange between the still boiling bottoms stream and at least one part the natural gas feed stream and / or a recycle stream, wherein reboiling can be achieved by calories absorbed from the natural gas feed stream about gas and / or recirculation flow.

The installation according to the invention may include one or more of the following features, taken individually or in accordance with all technically possible combinations:

- it includes a first heat exchanger located upstream of the process stream, by means of which heat exchange can be established between at least one part of the natural gas feed stream, still boiling stream, optionally side boiling streams, at least one part of the overhead stream and the recycle stream;

- it includes a first heat exchanger located upstream of the process stream, with which it is possible to establish heat exchange between the first part of the original natural gas stream and at least one part of the overhead stream; a second heat exchanger located upstream of the process, different from the first heat exchanger located upstream of the process, by which heat exchange can be established between the second part of the feed gas stream and the still boiling stream flowing from the recovery column, and the third heat exchanger located upstream of the process stream, different from the first heat exchanger located higher in the process flow and from the second heat located higher in the process stream while using the third heat exchanger located upstream of the process stream, a certain heat exchange interaction can be established between at least one part of the recycle stream and at least one part of the overhead stream, the installation preferably including an auxiliary compressor with which it is possible to compress a part of the recycle stream intended for introduction into a third heat exchanger located upstream of the process stream;

- the installation includes a first upper heat exchanger, with which you can provide a certain heat exchange interaction between at least one part of the upper stream, optionally with the reflux stream, and the secondary reflux stream;

- the installation includes a second upper heat exchanger, different from the first upper heat exchanger, and with it you can set a specific heat exchange interaction between the second part of the upper stream and the recycle stream.

The present invention will be better understood after reading the description below, which is given only as an example and contains links to the accompanying drawings, in which:

- FIG. 1 is a functional diagram of a first installation for implementing the first method according to the invention,

- FIG. 2 is a diagram of a second installation similar to that shown in FIG. 1, for implementing the second method according to the invention;

- FIG. 3 is a diagram of a third installation similar to that shown in FIG. 1, for implementing the third method according to the invention;

- FIG. 4 is a diagram of a fourth installation similar to that shown in FIG. 1, for the implementation of the fourth method according to the invention;

- FIG. 5 is a diagram of a fifth installation similar to that shown in FIG. 1, for implementing the fifth method according to the invention;

- FIG. 6 is a diagram of a sixth installation similar to that shown in FIG. 1, for implementing the sixth method according to the invention, the sixth installation being obtained by eliminating bottlenecks in an existing installation.

The first apparatus 11 of the invention depicted in FIG. 1, is intended for the simultaneous production of desulfurized, dry and at least partially decarbonated natural gas from treated feed stream 13 as natural product 15, a fraction of C ₃ ⁺ hydrocarbons and an ethane-enriched stream 19 with a controlled flow rate.

The term “at least partially decarbonized” means that the carbon dioxide content of the natural gas feed stream 13 is preferably 50 ppm or less if the treated natural gas 15 needs to be liquefied. The indicated content is preferably less than 3% if the treated natural gas 15 is sent directly to the gas distribution network.

In addition, the water content is less than 1 ppm, preferably less than 0.1 ppm.

Installation 11 includes a block 21 for the separation of C ₂ ⁺ hydrocarbons and a fractionation block 23 for C ₂ ⁺ hydrocarbons.

Throughout the text that follows, the liquid stream and the pipeline through which it is pumped will be denoted by the same position, the corresponding pressure values represent absolute pressure values, and the corresponding percentages are molar percentages.

Allocating unit 21 of C ₂ ⁺ hydrocarbons comprises sequentially arranged first the upstream heat exchanger 25, the first located the upstream of the separator vessel 27, the first located the upstream turbine 29 conjugated to a first compressor 31, a first upper coil 33 and the column 35 selection, equipped with at least one side circuit 37, 39 re-boiling and side circuit 41 re-boiling.

In this example, column 35 is provided with two side reflux circuits 37, 39.

Block 21 further includes a second compressor 43 driven by an external energy source and a first refrigerator 45 located downstream of the second compressor 43. Block 21 also includes a column cube pump 47.

The fractionation unit 23 includes a fractionation column 61. Column 61 includes in its upper part an upper condenser 63, and in its lower part a boiler 65.

The upper condenser 63 includes a second cooler 67 and a first separator vessel 69 located downstream of the reflux pump 71. Next will be described the first method according to the invention, carried out using the installation 11.

A typical initial molar composition of the feed stream 13 of desulfurized, dry and at least partially decarbonated natural gas is shown in the table below.

More generally, the mole fraction of methane in the feed stream 13 of natural gas lies between 75% and 90%, the mole fraction of C ₂ ⁺ hydrocarbons lies between 5% and 15%, and the mole fraction of C ₃ ⁺ hydrocarbons lies between 1% and 8%.

The feed rate to be processed is, for example, about 38,000 kmol / h.

The natural gas feed stream 13 has a temperature close to room temperature, i.e. substantially equal to 20 ° C., and the pressure is noticeably higher than 35 bar.

In a specific example, the natural gas stream 13 has a temperature of 20 ° C. and a pressure of 50 bar abs.

In the installation of FIG. 1, the natural gas feed stream 13 is cooled and at least partially condensed in a first upstream heat exchanger 25 to form a cooled feed stream 113.

The cooled feed stream 113 is introduced into a first separator vessel 27 located upstream of the process stream, in which separation is performed between the gas phase 115 and the liquid phase 117.

The liquid phase 117, after passing into the expansion valve 119, forms an expanded mixed phase 120, which is introduced at the first intermediate level N1 of the recovery column 35 located in the upper zone of the column, above the side boiling circuits 37 and 39.

By “intermediate level” is meant location, so that the distillation means are located both above and below the specified level.

The gas fraction 115 is separated into a feed stream 121 and a reflux stream 123.

The molar flow rate of the feed stream 121 is preferably higher than the molar flow rate of the reflux stream 123.

The feed stream 121 is expanded in the turbine 29 to achieve a pressure close to the pressure value of the column 35, in order to obtain an expanded feed stream 125. Stream 125 is introduced into the isolation column 35 at a second intermediate level N2 located above the first intermediate level N1.

The reflux stream 123 is partially or completely condensed in the first upper heat exchanger 33, and then expanded in the expansion valve 127 to form an expanded reflux stream 128. The specified stream 128 is introduced into the selection column 35 at the third intermediate level N3 located above the intermediate level N2.

The pressure of the recovery column 35 is, for example, from 12 to 40 bar.

The isolation column 35 produces an upper stream 131, which is heated in the first upper heat exchanger 33 by heat exchange with the reflux stream 123 to obtain a partially heated upper stream 139.

Stream 139 is again heated in a first heat exchanger 25 located higher up in the process stream by heat exchange with the natural gas feed stream 13 to obtain a heated overhead stream 140.

After that, the heated overhead stream 140 is compressed in the first compressor 31 and then in the second compressor 43 in order to obtain a compressed overhead stream 141. The pressure of the stream 141 is higher. 25 bar, for example, equal to 50 bar. Then, stream 141 is cooled in a first refrigerator 45 to produce processed natural gas 15.

According to the invention, the recycle stream 152 is withdrawn in the overhead stream leaving the column 35. In the example illustrated in FIG. 1, the recycle stream 152 is sampled in a compressed heated overhead stream 141 after it has been cooled in the first refrigerator 45.

The ratio of the molar flow rate of the recirculation stream 152 to the molar flow rate of the overhead stream 131 exiting the recovery column 35 is from 0% to 25%.

Then, the recycle stream 152 is supplied to the first heat exchanger 25 located above the process stream for cooling therein by heat exchange with at least one part of the overhead stream 131. In this example, the stream 152 is introduced into the heat exchange interaction with the partially heated overhead stream 139 exiting the overhead exchanger 33, in order to obtain a partially cooled recirculation stream 154.

After this, the stream 154 is introduced into the upper heat exchanger 33 with the aim of cooling in it by heat exchange with the upper stream 131 and the formation after expansion in the valve 156 of a cooled recirculation stream 155.

The cooled recycle stream 155 is fed to the recovery column 35 at a level N5 located above level N3, preferably corresponding to a first stage, starting at the top of the column 35.

Treated gas 15 contains in this example 1.36 mol%. nitrogen, 96.80 mol%. methane and 1.76 mol%. With ₂ hydrocarbons.

In a more general case, the treated gas 15 contains more than 99 mol%. methane present in the feed stream 13 of natural gas, and less than 0.1 mol%. C ₃ ⁺ hydrocarbons present in the composition of the natural gas feed stream.

The treated gas 15 contains a molar fraction of C ₂ hydrocarbons present in the feed stream 13 of natural gas, comprising from 2% to 85%, while this ratio can be adjusted.

Thus, the gas 15 has a content of C ₆ ⁺ hydrocarbons less than 1 h / mn, a water content of less than 1 h / million, preferably less than 0.1 parts / million, and the carbon dioxide content of less than 50 parts / million. Based on the foregoing, the treated gas 15 can be sent directly to the liquefaction line in order to produce liquefied natural gas. It can also be sent directly to the gas distribution network.

In the side boiling circuits 37 and 39, the side boiling streams 161 and 163 are removed from the column 35 and re-introduced into it after heating in the first heat exchanger 25 located above the process stream by heat exchange with at least one part of the natural gas feed stream 13 and at least one part of the recycle stream 152.

Thus, the upper side reflux stream 163 is selected at level N6 located below level N1, for example at the eleventh stage, starting from the top of column 35, and then fed to the first heat exchanger 25. After that, the stream 163 is heated in the heat exchanger 25 and then directed back to column 35 at level N7 located below level N6.

In addition, the lower side reflux stream 161 is taken at level N8 located below level N7, and then fed to heat exchanger 25. After that, stream 161 is heated in heat exchanger 25 and then reintroduced at level N9 located below level N8, for example at the fourteenth step, starting at the top of column 35.

In the bottom boiling loop 41, the liquid bottom boiling stream 165 is recovered near the bottom of the column 35, below the side boiling streams 161, 163.

According to the invention, stream 165 is fed to a first heat exchanger 25 located above the process stream, where it is heated by heat exchange with at least one part of the natural gas feed stream 13 and at least one part of the recycle stream 152. The heated and partially vaporized reflux stream is then reintroduced into column 35.

The bottoms stream 171 enriched in C ₂ ⁺ hydrocarbons is recovered from the bottom of the recovery column 35.

VAT stream 171 contains more than 99 mol%. C ₃ ⁺ hydrocarbons contained in the feed stream 13 of natural gas. It has a methane content of between 9% and 5%.

The bottoms stream 171 is pumped by the pump 47 of the bottoms liquid tank and introduced at the intermediate level P1 of the fractionation column 61.

In the illustrated example, the fractionation column 61 operates at a pressure of from 20 to 42 bar. In this example, the pressure of the fractionation column 61 is at least one bar higher than the pressure of the recovery column 35.

The bottom stream 181 is recovered from the fractionation column 61 in order to obtain a fraction of 17 C ₃ ⁺ hydrocarbons.

The degree of extraction of C ₃ ⁺ hydrocarbons in the method is more than 99%. In any case, the degree of propane recovery is more than 99%.

Ethane-enriched stream 19 is diverted directly to intermediate level P2 located in the upper zone of the fractionation column 61.

In the example illustrated in the figure, this stream contains 1.21% methane, 97.77% ethane and 1.00% propane.

In a more general case, the molar content of ethane in ethane-enriched stream 19 is more than 95%, namely between 96% and 100%.

The number of theoretical plates between the top of the column 61 and the upper level P2 is, for example, from 1 to 7. The level P2 is above the supply level P1.

The second overhead stream 183 is removed from the top of the column 61, and then cooled in a second cooler 67 to obtain a second cooled and at least partially condensed overhead stream 185. The second stream 185 is introduced into a second separator vessel 69 to produce a liquid fraction 187 and a gas fraction 188.

In the example shown in FIG. 1, the entire liquid fraction 187 is pumped by a pump 71 to form a primary reflux stream 190 before refluxing into the fractionation column 61 at an upper level P3 located above level P2.

In this case, the entire gas fraction 188, after cooling in the upper heat exchanger 33 and expansion in the valve 193, forms a secondary reflux stream 192.

In the upper heat exchanger 33, the gas fraction 188 is cooled by heat exchange with the upper stream 131.

In an alternate embodiment shown in dashed lines, the liquid fraction 187 is separated into a primary liquid fraction 189 of reflux and a secondary liquid fraction 191.

The secondary liquid fraction 191, if present, is then mixed with the gas fraction 188 to form a secondary reflux stream 192 after cooling and expansion.

Secondary reflux stream 192 is introduced along with reflux at the upper level N4 of the isolation column 35 located between the upper level N5 and the intermediate level N3.

The degree of ethane extraction and, consequently, the ethane flow rate generated by the installation 11, is controlled by adjusting the flow rate of the recirculation stream 152, adjusting the pressure in the recovery column 35 by means of compressors 43 and 31, while the parameters mentioned are of the variable speed type, on the one hand and with the final adjustment of the flow rate of the secondary reflux stream 192 circulating through the expansion valve 193, on the other hand.

As shown in the table below, the flow rate of an ethane-enriched stream is controlled with little or no effect on the degree of extraction of C ₃ ⁺ hydrocarbons.

In view of the foregoing, the method according to the invention using simple and inexpensive means makes it possible to change and easily adjust the ethane-enriched stream 19 extracted from the source natural gas 13, while maintaining the degree of propane recovery above 99%. The specified result is achieved without any modification of the installation in which this method is implemented.

Values of pressures, temperatures and flow rates in case the degree of ethane recovery is 84.99% are shown in the table below.

When the flow rate of the ethane-enriched stream 19 decreases, the total compression power also greatly decreases.

In addition, the installation 11 according to the invention does not require the use of multi-threaded heat exchangers. Thus, only heat exchangers with pipes and casing can be used.

Treated natural gas 15 contains substantially negligible amounts of C ₅ ⁺ hydrocarbons, for example less than 1 ppm. Therefore, if the carbon dioxide content of the treated gas 15 is less than 50 ppm, this gas 15 can be liquefied without any further processing or fractionation.

In the first method of the invention, the boiling bottoms stream 165 in the first heat exchanger 25 is introduced into a certain heat exchange interaction with the recirculation stream 152, at least one part of the overhead stream 131, with the natural gas feed stream 13 and with the side boiling streams 161, 163.

The specified specific thermal integration of this method is favorable in terms of yield and does not affect the degree of ethane extraction when the last task is relevant.

Thus, when the recirculation stream 152 is introduced into a certain heat exchange interaction with at least one part of the upper stream 131, and when the side boiling stream 165 is introduced into a certain heat exchange interaction with the natural gas feed stream 13, as was unexpectedly discovered by the inventors, a synergistic increased output at the facility 11.

So, in accordance with the table below, there is a 16% increase in yield compared to the installation according to the prior art while maintaining the degree of extraction equal to 85%, while all other conditions are maintained. This very significant increase is achieved while maintaining a very high degree of ethane recovery.

In addition, the combined use of the recirculation of a portion of the heated gas and the integrated still bottom boiling unit 41 connected to the first heat exchanger 25 unexpectedly leads to a larger increase in yield than that observed when performing any one of these steps taken separately.

Thus, if the first method is applied without any recirculated gas stream 152, the achieved yield increase is 9.4%, whereas in the case where the first method 11 is applied without a still boiler connected to the heat exchanger 25, the achieved yield increase is 0 , 2%. In view of the foregoing, the observed increase in yield with the combined use of the above-mentioned features is significantly higher than the sum of individually achieved increase in yield, which demonstrates an unexpected synergistic effect that does not affect the degree of ethane extraction.

Alternatively, the treated gas stream exiting the first compressor 31 can be supplied to the compressor 43 using two equivalent power stages, with an intermediate cooler cooling the gas to the same temperature as the refrigerator 45.

A second installation 201 according to the invention is shown in FIG. 2. The installation 201 differs from the first installation 11 in that it further includes an auxiliary expansion turbine 203 and an auxiliary compressor 205 coupled to the turbine 203. In the first embodiment, the auxiliary compressor 205 is placed between the first compressor 31 and the second compressor 43.

The second method according to the invention is carried out on the second installation 201.

Unlike the first method according to the invention, the natural gas feed stream 13 is separated into a first feed stream 207 and a second feed stream 209.

The molar flow rate of the first feed stream 207 is preferably higher than the molar flow rate of the second feed stream 209.

Further, the first feed stream 207 is introduced into the first heat exchanger 25 so that it is cooled and partially condensed there, and also forms a cooled natural gas stream 113 supplied to the first separator vessel 27.

The second feed stream 209 is introduced into the auxiliary expansion turbine 203 in order to expand thereto until a pressure close to the working pressure of the column 35 is reached and the auxiliary reflux stream 211 is formed. After that, the auxiliary reflux stream 211 is introduced into the first upper heat exchanger 33 so that it is cooled and partially condensed therein, and then fed to the expansion valve 213 to obtain an expanded auxiliary reflux stream 215.

Then, stream 215 is introduced into the recovery column 35 at an upper level N10 located between level N3 and level N4.

In the example illustrated in FIG. 2, the overhead stream 217 exiting the first compressor 31 is introduced at the outlet of the stream from the first compressor 31 to the auxiliary compressor 205 so that the stream is compressed at an intermediate pressure before being combined with the stream directed to the second compressor 43.

Values of pressures, temperatures and flow rates in the case when the degree of ethane recovery is 85.00% are shown in the table below.

The application of the second method according to the invention results in a result similar to that achieved when using the first method, due to the synergy observed when a certain heat exchange interaction of the bottled stream 165 re-boiling with the original stream 13 of natural gas, in combination with the presence of a recirculation stream 152 introduced in a certain heat exchange interaction with at least one part of the overhead stream 131.

Thus, the power consumption during the implementation of the method in the case of using the installation 201 is equal to 37588 kW, i.e. which is 16% more profitable compared with the installation of the existing level of technology.

In an alternative embodiment of FIG. 2, an auxiliary compressor 205 (in the form of dashed lines) is installed downstream of the compressor 43 in order to compress the recirculation stream 152 before leading it into the first heat exchanger 25.

Other than this, this installation and this method are similar to those shown in FIG. 2.

A third installation 221 according to the invention is shown in FIG. 3. In contrast to the apparatus 11 illustrated in FIG. 1, the installation 221 includes a second separator vessel 223 located downstream of the first separator vessel for collecting a liquid phase 117 flowing from the first separator vessel 27.

The third method according to the invention is applied using the apparatus 221. Said third method differs from the first method according to the invention in that the liquid phase 117 is expanded in a static expansion valve 225. This expansion is performed until a pressure is reached above the working pressure of the column 35.

Then, the liquid phase is expanded and introduced into the separator vessel 223 located upstream.

The liquid fraction 227 is recovered in the lower part of the vessel 223 and expands in the valve 229 to form an expanded fraction 231. The expanded fraction 231 is introduced into the isolation column 35 at a level of N1.

The gas fraction 233 is collected in the upper part of the second separator vessel 223 located upstream. The specified fraction 233 is sent to the upper heat exchanger 33 for cooling therein before expansion in the expansion valve 135 in order to obtain an expanded fraction 237.

The expanded fraction 237 is introduced into the isolation column 35 at an intermediate level N11 located between level N2 and level N3.

Values of pressures, temperatures and flow rates in the case when the degree of ethane extraction is 84.99% are shown in the table below:

The method carried out in the third installation 221 according to the invention leads to a total amount of power consumed by the compressors of 35,960 kW, which is 19.7% more profitable compared to the existing method of the prior art.

In addition, it allows you to further increase the yield by 3.9% compared with the first method according to the invention.

In an alternative embodiment of the third method, the liquid phase 117 obtained at the bottom of the first separator vessel 27 is introduced into the first heat exchanger 25 for heating before being fed to the valve 225.

The mixture is expanded in valve 225 before separation in a second separator vessel 223 located upstream.

A fourth installation 241 according to the invention is shown in FIG. 4. Unlike the first And installation, a stream 171 exiting the separation column 35 is passed into the first heat exchanger 25 for heating therein before fractionation is introduced into the column 61.

In view of the foregoing, in the fourth method according to the invention, heating of said bottoms stream 171 is applied after it is passed to pump 47.

With an ethane extraction rate of 85.00%, the total consumption is 34201 kW, which provides a benefit of 23.6% compared with the installation of the existing prior art. In addition, the increase in yield is 8.6% relative to the first method according to the invention.

Values of pressures, temperatures and flow rates in the case when the degree of ethane extraction is 85.00% are shown in the table below:

A fifth apparatus 251 according to the invention is shown in FIG. 5. This installation is intended to implement the fifth method according to the invention.

Unlike the first method according to the invention, the bypass stream 253 is taken in the recirculation stream 152, preferably downstream from the first heat exchanger 25 and upstream from the second heat exchanger 33 for re-introduction into the stream located downstream from the first turbine 29 dynamic expansion.

The flow rate of the bypass stream 253 is, for example, 47% of the total molar flow rate of the recirculation stream 152 taken from the treated stream.

Other than this, the fifth method according to the invention is carried out similarly to the fourth method according to the invention.

In the example shown in FIG. 5, the bypass stream 253 is mixed with the power stream 121 before it is introduced into the turbine 29.

In an alternative embodiment, shown by dashed lines, the fifth installation 251 further includes a secondary dynamic expansion turbine 255 coupled to the secondary compressor 257. In this case, the secondary recirculation stream 258 is withdrawn in the recirculation stream 152 before being introduced into the first heat exchanger 25.

The secondary recycle stream 258 is introduced into the secondary expansion turbine 255 to form an expanded secondary recycle stream 261, which is reintroduced into the partially heated overhead stream 139 exiting the first upper heat exchanger 33.

In addition, the secondary overhead stream 263 is withdrawn in a heated overhead stream 140 exiting the first heat exchanger 25 for supplying to the secondary compressor 257 and obtaining a compressed secondary overhead stream 265.

Then, said stream 265 is reintroduced into the compressed overhead stream, which is at intermediate pressure and exits the first compressor 31, upstream of the second compressor 43.

The power gain achieved in relation to the current state of the art method is in this case about 15.4%, with a total power consumption of 37851 kW.

Values of pressures, temperatures and flow rates in the case when the degree of ethane extraction is 85.00% are shown in the table below:

The sixth installation 271 according to the invention is shown in FIG. 6. This unit 271 is intended to eliminate the bottlenecks of the unit illustrated in US Pat. No. 7,458,232 and initially includes a first heat exchanger 25 located above the process stream, a first separator vessel 27, a recovery column 35, a first upper heat exchanger 33, and a fractionation column 61 equipped with top capacitor 63.

Unlike the first installation 11 according to the invention, installation 271 further includes a second heat exchanger 273 located upstream of the process stream and a third heat exchanger 275 located upstream of the heat exchanger, designed to be arranged in parallel with the first upstream heat exchanger 25.

Installation 271 further includes an auxiliary compressor 277 for compressing the recycle stream 152 and an auxiliary refrigerator 279 for cooling the compressed recycle stream.

In addition, the sixth installation 271 includes a second upper heat exchanger 281, designed to be parallel to the first upper heat exchanger 33, with the aim of introducing at least one part of the upper stream 131 into heat exchange interaction with at least one part of the recirculation stream 152.

The sixth method according to the invention is carried out at the sixth installation 271. In the indicated method, the natural gas feed stream 13 is divided into a first feed stream 207 introduced into a first heat exchanger 25 located upstream and a second feed stream 209 introduced into a second upstream process stream heat exchanger 273.

Then, the first feed stream 207 is cooled in the first upstream heat exchanger 25 to obtain a first cooled feed stream 281 A. In the same way, the second feed stream 209 is cooled in a second upstream heat exchanger 273 to obtain a second cooled feed stream 283 The streams 281A and 283 are mixed to form a chilled stream 113 intended to be introduced into the first separator vessel 27 located upstream of the process stream.

The lateral boiling streams 161,163 are introduced into the first heat exchanger 25 for heating.

Unlike the first method according to the invention, the boiling stream 165 re-boiling is introduced into the second upstream heat exchanger 273 for heating in it by heat exchange with the second feed stream 209.

In addition, unlike the first method according to the invention, the overhead stream 131 exiting the separation column 35 is primarily divided into a first overhead part 285 and a second overhead part 287.

The first part 285 is introduced into the first upper heat exchanger 33 for heating therein by heat exchange with the reflux stream 123, on the one hand, and the secondary reflux stream 192, on the other hand.

The second part 287 is introduced into the second upper heat exchanger 281.

The ratio of the molar flow rate of the first part 285 to the speed of the second part 287 is, for example, from 0 to 20.

Then, the fractions recovered at the outlet of the heat exchangers 33, 281 are mixed again before separation again into the first part 289 of the heated overhead stream and the second part 291 of the heated overhead stream.

The first part 289 is introduced into the first heat exchanger 25 located above the process stream for heating therein by heat exchange with the first feed stream 207, simultaneously with the side boiling streams 161 and 163.

The second part 291 is introduced into the third heat exchanger 275 located upstream of the process stream for heating therein.

After that, the heated parts 289 and 291 are combined together to form the heated overhead stream 140, and then they are supplied to the first compressor 31.

Unlike the first method according to the invention, the recycle stream 152 is taken in the heated overhead stream 140 upstream of the first compressor 31.

The ratio of the molar flow rate of the recirculation stream 152 to the molar flow rate of the overhead stream 131 leaving the column 35 is, for example, from 0% to 25%.

Thereafter, the recycle stream 152 is compressed in the auxiliary compressor 277 until a pressure is reached, for example, above 50 bar, and then cooled in the refrigerator 279 to form a cooled compressed recycle stream 293.

After this, the stream 293 is sequentially introduced into the third heat exchanger 275 located above the process stream, and then into the second upper heat exchanger 281 for cooling therein before expanding in the expansion valve 295 and forming a cooled expanded recirculation stream 297.

Then stream 297 is introduced into the isolation column 35 at the same level as the secondary reflux stream 194.

Thus, in the first heat exchanger 25 located above the process stream, which was initially installed in the plant, part 207 of the natural gas feed stream 13, side refluxing streams 161, 163, and overhead part 289 are introduced into a certain heat exchange interaction.

In the second heat exchanger 273 located upstream of the process stream, a second part 209 of the natural gas feed stream 13 and bottoms reflux stream 165 are introduced into the defined heat exchange interaction. In the third heat exchanger 275 located upstream, a second part 291 of the upper stream 131 and a recycle stream 152 are introduced into the defined heat exchange interaction.

In addition, the installation 271 according to the invention does not require the use of multi-threaded heat exchangers. Thus, only heat exchangers with pipes and casing can be used.

In addition, in the upper part of the column 35, the reflux stream 123, the first part of the upper stream 285 and the secondary reflux stream 192 are introduced into the heat exchange interaction in the first upper heat exchanger 33. In the second upper heat exchanger 281, the second part 287 of the upper stream 131 is introduced into the heat exchange interaction and cooled compressed recycle stream 233.

Installation 271, as illustrated in FIG. 6, provides the opportunity to create conditions for increasing the feed stream by an amount from 0% to 15%, and more preferably at least 10%, by limiting to a minimum the necessary increase in compression power.

Values of pressures, temperatures and flow rates in the case when the degree of ethane extraction is 85.00% are shown in the table below:

In the example illustrated in the figures, ethane-enriched stream 19 is taken directly to fractionation column 61, preferably at the upper level P2 of column 61, as described above.

In addition, the fraction of 17 C ₃ ⁺ hydrocarbons is formed directly by the bottom stream 181 of the column 61.

In an alternative embodiment (not shown), C ₂ ⁺ hydrocarbons are recovered from fractionation column 61 in the bottom stream 181 simultaneously with C ₃ ⁺ hydrocarbons. Then, the bottom stream 181 is introduced into the fractionation column following the downstream stream.

The ethane-enriched fraction 19, like the 17 C ₃ ⁺ hydrocarbon fraction 17, is then obtained in a fractionation column located downstream of the process stream.

Claims (50)

1. A method for the simultaneous production of treated natural gas (15), fraction (17) enriched in C ₃ ⁺ hydrocarbons, and at least in some conditions for the production of ethane-enriched stream (19) from a source stream (13) of natural gas containing methane, ethane and C ₃ ⁺ hydrocarbons, where the specified method includes the following stages: - the natural gas feed stream (13) is cooled and partially condensed in at least one first heat exchanger (25) located upstream of the process stream to obtain a cooled feed stream (113); - the cooled feed gas stream (113) is separated into a liquid stream (117) and a gas stream (115); - the liquid stream (117) is expanded and the stream formed from the liquid stream (117) is introduced into the column (35) of the allocation of C ₂ ⁺ hydrocarbons at the first intermediate level (N1); - from the gas stream (115) form the turbine power stream (121); - expand the power flow (121) in the dynamic expansion turbine (29) and introduce it into the separation column (35) at the second intermediate level (N2); - at least one part of the upper stream (131) of the recovery column (35) is isolated and compressed to produce natural gas (15), and the lower stream of the recovery column (35) is also extracted to obtain a liquid stream (171) enriched in C ₂ ⁺ -hydrocarbons; - a liquid stream (171) is introduced at the power level (P1) of the fractionation column (61) provided with an upper condenser (63), while under the mentioned conditions an ethane-enriched stream (19) is generated from the stream leaving the fractionation column (61), wherein the fractionation column (61) generates a lower stream (181) intended to form, at least in part, a fraction of C ₃ ⁺ hydrocarbons; - the primary reflux stream (190) obtained in the upper condenser (63) is introduced into the fractionation column (61); - a secondary reflux stream (192) is obtained from the upper condenser (63), and a secondary reflux stream (192) is introduced into the upper part of the separation column (35), moreover, the described method is characterized in that it includes the following stages: - from the overhead stream (131, 140, 141) leaving the recovery column (35), a recycle stream (152) is selected; - establish a certain heat exchange interaction between the recirculation stream (152) and at least one part of the upper stream (131) emerging from the column (35) allocation; - after expansion, the cooled and expanded recirculation stream is reintroduced into the separation column (35); however, the described method involves the selection in the cube of the column (35) of the allocation of at least one cubic stream (165) of re-boiling and providing a certain heat exchange interaction between the bottoms stream of boiling and at least one part of the source of natural gas (13) and / or recirculation stream (152), while the re-boiling of bottoms liquid is provided due to calories absorbed from the source stream (13) of natural gas and / or recirculation stream (152). 2. The method according to p. 1, characterized in that at least one part of the upper stream (131) of the separation column (35) and the recirculation stream (152) are introduced into a certain heat exchange interaction with the natural gas feed stream (13) and bottoms stream ( 165) re-boiling. 3. The method according to p. 1, characterized in that the recirculation stream (154) exiting the first heat exchanger (25) located above the process stream, the secondary reflux stream (192) exiting the upper condenser (63), and the upper stream ( 131), leaving the separation column (35), is introduced into a certain heat exchange interaction in the first upper heat exchanger (33). 4. The method according to p. 1, characterized in that at least one side stream (161, 163) re-boiling is selected above the bottoms stream (165) re-boiling, while the specified or each side stream (161, 163) re-boiling is introduced into a specific heat exchange interaction with at least one part of the natural gas feed stream (13). 5. The method according to p. 1, characterized in that the ethane-enriched stream (19) is withdrawn from the intermediate level of the fractionation column (61) located above the feed level of the column (61) and below the upper level of the fractionation column (61). 6. The method according to p. 1, characterized in that it includes the following stages: - the feed stream (13) of natural gas is divided into a first feed stream (207) and a second feed stream (209); - the first source stream (207) is fed into the first heat exchanger (25) located upstream of the process stream; - at least one part of the second source stream (209) is introduced into the auxiliary dynamic expansion turbine (203) to obtain an auxiliary reflux stream (215) from the output stream flowing from the auxiliary turbine (203); - the auxiliary stream (215) of reflux is fed to the separation column (35). 7. The method according to p. 6, characterized in that at least one part of the recirculation stream (152) is compressed in an auxiliary compressor (205), coupled to an auxiliary turbine (203). 8. The method according to p. 6, characterized in that at least one part of the overhead stream is compressed in an auxiliary compressor (205) associated with the auxiliary turbine (203), preferably between the first compressor (31) associated with the first turbine (29) , and a second compressor (43). 9. The method according to p. 1, characterized in that it includes the selection of the bypass stream (253) from the recirculation stream (152), while the bypass stream (253) is re-introduced into the stream located upstream of the first turbine (29) dynamic expansion. 10. The method according to p. 1, characterized in that the liquid stream (117) emerging from the first separator vessel (27) located above the process stream is expanded and introduced into the second separator vessel (223) located above the process stream in order to obtain liquid fraction (227) and gas fraction (233), the liquid fraction (227) after expansion is introduced at the first intermediate level (N1) of the isolation column (35), the gas fraction (233) is introduced at the upper level (N11) of the isolation column (35) located above the intermediate level (N1), the liquid stream (117) exiting the first separator vessel (25) located higher in the process stream is preferably introduced into a certain heat exchange interaction with the natural gas feed stream (13) to heat it before being introduced into the second vessel (223) located higher in the process stream separator. 11. The method according to p. 1, characterized in that it includes the establishment of heat exchange between the lower stream (171) emerging from the column (35) allocation, and the source stream (13) of natural gas and bottoms stream (165) re-boiling in the first located upstream of the heat exchanger (25) before being fed to the fractionation column (61). 12. The method according to p. 1, characterized in that the gas stream (115) emerging from the first vessel (27) of the separator is divided into a stream (121) of power and a stream (123) of reflux, and the stream (121) of power is intended for power dynamic expansion turbines (29), and the reflux stream (123) after cooling, partial or complete condensation and expansion in the valve is introduced into the recovery column (35). 13. Installation (11; 201; 221; 241; 251; 271) for the simultaneous production of treated natural gas (15), fraction (17) enriched in C ₃ ⁺ hydrocarbons, and, in certain production conditions, ethane-enriched stream (19 ), from the feed stream (13) of natural gas containing methane, ethane and C ₃ ⁺ hydrocarbons, including: - a cooling and partial condensing unit of a natural gas feed stream (13) containing at least one first heat exchanger (25) located upstream of the process stream to form a cooled feed stream (113); - a unit for separating the cooled feed stream (113) into a liquid stream (117) and a gas stream (115); - a column (35) for the separation of C ₂ ⁺ hydrocarbons; - a node for expanding the liquid stream (117) and introducing the stream formed from the liquid stream (117) into the separation column (35) at the first intermediate level (N1); - a unit for forming from a gas stream (115) a stream (121) for supplying a turbine; - a node for expanding the power stream (121), including a dynamic expansion turbine (29), and a node for supplying the expanded power stream to the extraction column (35) at the second intermediate level (N2); - a separation and compression unit for at least one part of the upper stream (131) of the recovery column (35) to produce natural gas (15) and a separation unit of the lower stream of the separation column (35) to produce a liquid stream (171) enriched in C ₂ ⁺ -hydrocarbons; a fractionation column (61) provided with an upper condenser (63), - a unit for supplying a liquid stream at the power level (P1) of the fractionation column (61), and under the indicated conditions it is possible to obtain ethane-enriched stream (19) from the stream leaving the fractionation column (61), while in the fractionation column (61) it is possible to produce a lower stream (181) intended to produce, at least in part, a fraction (17) of C ₃ ⁺ hydrocarbons; - a feed unit for the primary stream (190) of reflux obtained in the upper condenser (63) into the fractionation column (61); - a node for receiving a secondary stream (192) of reflux from the upper capacitor (63) and a node for supplying a secondary stream (192) of reflux to the upper part of the separation column (35), characterized in that the described installation includes: - a unit for selecting a recirculation stream (152) from the upper stream (131, 140, 141) of the extraction column (35); - a unit for establishing heat exchange between the recirculation stream (152) and at least one part of the upper stream (131) exiting the separation column (35); a re-introduction unit, after expanding (35), the recycle stream (152) into the recovery column (35), said installation additionally including a selection unit in the cube of the column (35) for separating at least one cubic stream (165) of re-boiling and a heat exchange establishment unit between the still boiling bottoms stream and at least one part of the natural gas feed (13) and / or the recycle stream (152), whereby it is possible to re-boil due to the calories absorbed from the source otok (13) of natural gas and / or recycle stream (152). 14. Installation (11; 201; 221; 241; 251) according to claim 13, characterized in that it includes a first heat exchanger located above the process stream (25), by which it is possible to establish a heat exchange interaction between at least one part of the source a natural gas stream (13), a refluxing bottoms stream (165), optionally side refluxing streams (161, 163), at least one part of the overhead stream (131) and a recycle stream (152). 15. Installation (271) according to claim 13, characterized in that it includes a first heat exchanger (25) located upstream of the process stream, capable of providing heat exchange between the first part of the natural gas feed stream (13) and at least one part of the overhead stream ( 131); a second heat exchanger (273) located upstream of the process, different from the first heat exchanger (25) located upstream of the process, capable of providing heat exchange between the second part of the initial gas stream (13) and the boiling bottoms stream (165) flowing from the column (35 ) separation, and the third heat exchanger (275) located higher in the process flow, different from the first heat exchanger (25) located higher in the process flow and the second heat located higher in the process flow an exchanger (273), the third heat exchanger (275) located upstream of the process stream capable of providing heat exchange between at least one part of the recycle stream (152) and at least one part of the overhead stream (131), the installation (271) preferably including auxiliary compressor (277), with which it is possible to compress part of the recirculation stream (152), intended for introduction into the third heat exchanger (275) located upstream of the process stream.

Images