EA021771B1 - Process for producing a contaminant-depleted hydrocarbon gas stream - Google Patents

Abstract

The invention provides a process for producing a contaminant-depleted gas stream from a contaminated hydrocarbon feed gas stream (1) containing at least 10 vol.% of acidic contaminants, in particular HS and CO, the method comprising the steps of: (a) expanding the contaminated hydrocarbon feed gas stream in an expander (6) to obtain an expanded contaminated hydrocarbon feed gas stream; (b) allowing at least part of the contaminants in the expanded contaminated hydrocarbon feed gas stream to liquefy; (c) separating at least part of the contaminants enriched liquid phase comprising hydrocarbons from the gaseous phase with lowered contaminant content in a first separator (8), thereby obtaining the contaminant-depleted gas stream (17) and a liquid stream (19 ) mainly comprising contaminants and further comprising remaining hydrocarbons; (d) separating remaining hydrocarbons from the liquid stream in a second separator (13), thereby obtaining an overhead stream (14) comprising remaining hydrocarbons and a bottom stream (22) depleted in hydrocarbons; (e) leading the overhead stream comprising remaining hydrocarbons to a point prior step (c); wherein step (d) prior to separating remaining hydrocarbons, further comprises the step of (d1) increasing the pressure (23) of the liquid stream.

Description

FIELD OF THE INVENTION

The invention relates to a method for producing a stream of gaseous hydrocarbons with a low pollution content and with improved hydrocarbon recovery. The invention includes removing acid contaminants from a gaseous hydrocarbon stream, such as a natural gas stream that contains hydrocarbons and acid pollution.

Natural gas streams may contain acid pollution. The best known contaminants are hydrogen sulfide and carbon dioxide (Η ₂ δ and CO ₂ ). Transportation and / or processing of natural gas that contains these contaminants can increase the cost of transportation and / or processing. In addition to the fact that contaminants can exhibit corrosive properties, hydrogen sulfide is toxic, and upon combustion it forms sulfur dioxide, i.e. other contaminant. Moreover, carbon dioxide reduces the calorific value of natural gas. Therefore, it is desirable to remove these contaminants from the natural gas stream, starting from the earliest stage.

State of the art

Methods for producing gas with a reduced content of contaminants by removing contaminants from a natural gas stream are known in the art.

For example, νθ 2006/087332 described a method for removing polluting gaseous components, such as carbon dioxide and hydrogen sulfide, from a natural gas stream. In this method, a contaminated natural gas stream is cooled in a first expander to obtain an increased volume of a gaseous stream having a temperature and pressure such that condensation conditions are achieved for phases containing predominant contaminants, such as carbon dioxide and / or hydrogen sulfide. Then, the gaseous stream with an increased volume enters the first sectional centrifugal separator to ensure separation of the liquid phase enriched in contaminants and the gas phase with a reduced content of contaminants. Then the gas phase with a reduced content of contaminants passes through a re-compression compressor, an intermediate cooler and a second expander into a second centrifugal separator.

The disadvantage of this method is that valuable hydrocarbons are lost as a result of joint condensation and dissolution of hydrocarbons together with a cold stream of acidic liquid waste. Thus, a substantial portion of the valuable hydrocarbons that are produced from a gas well can be lost with the waste stream. In addition, the use of a re-compression compressor, an intermediate cooler and an expander between two centrifugal separators degrades the efficiency of the hydrocarbon separation process, where the hydrocarbon efficiency is a measure of fuel gas consumption and hydrocarbon losses with contaminated liquid flows during the process. The present invention provides a method for improving the recovery of hydrocarbons from a liquid waste stream by a second expansion, which is performed in such a way that the total amount of hydrocarbons lost with the liquid waste stream is unexpectedly reduced to such an extent that it compensates for the necessary energy and investment costs.

SUMMARY OF THE INVENTION

The invention has developed a method for producing a gas stream with a reduced content of contaminants from an initial contaminated stream of gaseous hydrocarbons containing at least 10 vol.% Acid contaminants, in particular Η ₂ δ and CO ₂ , said method comprising:

(a) expanding the original contaminated gaseous hydrocarbon stream in the expander to obtain an increased volume of the original contaminated gaseous hydrocarbon stream;

(b) providing liquefaction of at least a portion of the contaminants in an increased volume of the initial contaminated gaseous hydrocarbon stream to form a dispersion of a liquid phase enriched in contaminants and still containing a small amount of hydrocarbons, and a gas phase with a reduced content of contaminants;

(c) separating at least a portion of the contaminant-rich liquid phase containing hydrocarbons from the gaseous phase with a reduced content of contaminants in the first separator, and thus obtaining a gaseous stream with a reduced content of contaminants and a liquid stream containing mainly contaminants and, in addition, containing the remaining hydrocarbons;

(i) separating the remaining hydrocarbons from the liquid stream in a second separator, and thereby obtaining a distillate stream containing the remaining hydrocarbons and a lower stream depleted in hydrocarbons;

(e) directing the distillate stream containing the remaining hydrocarbons to a point located prior to step (c);

where stage (s) prior to the allocation of the remaining hydrocarbons further comprises the step of:

(i1) increasing the pressure of a liquid stream containing mainly contaminants and, in addition, containing the remaining hydrocarbons to obtain a compressed liquid stream containing mainly contaminants and, in addition, containing the remaining hydrocarbons.

Optionally, the initial contaminated gaseous hydrocarbon stream is cooled to stage (a).

The method according to the invention provides improved hydrocarbon recovery compared to

- 1,021,771 by a known method for producing hydrocarbon gas with a low pollution content. Accordingly, the degree of hydrocarbon recovery is in the range of 1 to 90%.

The term gaseous hydrocarbon feed stream means any gas stream that contains a significant amount of hydrocarbons, especially methane. The term includes a natural gas stream, a associated gas stream, or a methane stream from a coal seam. The proportion of hydrocarbons in such gaseous streams, respectively, is from 10 to 85 vol.% Of the gaseous stream, preferably from 25 to 80 vol.%. In particular, the proportion of hydrocarbons in the natural gas stream is at least 75 vol.% Methane, preferably at least 90 vol.% Of the total hydrocarbon fraction. The proportion of hydrocarbons in the natural gas stream is generally from 0.1 to 20 vol.%, Mainly from 0.1 to 10 vol.% Hydrocarbons C2-C6 or heavier hydrocarbon compounds, and / or contains up to 20 vol.%, mainly from 0.1 to 10 vol.% nitrogen.

Natural gas flows can be available at temperatures from -5 to 150 ° C and pressures from 20 to 700 bar (2-70 MPa). In the method of the present invention, the natural gas stream contains mainly hydrogen sulfide and / or carbon dioxide as acidic contaminants. In addition, it has been found that small amounts of other contaminants may be present, for example, carbon oxysulfide (POPs), mercaptans, alkyl sulfides and aromatic sulfur compounds. The bulk of these components will also be removed in the method according to the invention. Acid pollution can be of natural origin, either partially or completely, as a result of pumping or re-pumping into an underground tank.

The amount of hydrogen sulfide in the gaseous hydrocarbon feed stream is mainly from 1 ppm by volume to 80 vol.%, Preferably above 5 vol.%, More preferably above 10 vol.%, Above 20 vol.% Or even above 25 vol.% and preferably below 50 vol.% calculated on the flow of gaseous hydrocarbon feeds. The amount of carbon dioxide in the gaseous hydrocarbon feed stream is mainly from 5 to 80 vol.%, Preferably above 10 vol.% And below 30 vol.%, Based on the gaseous hydrocarbon feed. The basis for this amount is the total volume of hydrocarbons, hydrogen sulfide and / or carbon dioxide and other components that together make up the flow of gaseous hydrocarbon feedstocks. It is noted that the method according to the invention is particularly suitable for gas streams containing a significant amount of acid contaminants, for example 10 vol.% Or more, mainly from 15 to 90 vol.% Of the gaseous hydrocarbon feed stream.

Natural gas streams extracted from underground formations typically contain water. In order to prevent the formation of gas hydrates in the method of the invention, it is advisable to remove at least a portion of the water. In this regard, the natural gas stream that is used in the method of the invention is preferably subjected to dehydration. This operation can be performed in a conventional manner. A suitable method is described in document UO-L 2004/070297. Other dehydration methods include molecular sieve treatment or glycol drying processes. Basically, water is removed until the amount of water in the natural gas stream is reduced to at most 50 ppm by weight, preferably at least 20 ppm, more preferably at least 1 ppm of water based on the entire flow of natural gas.

Optionally, to step a), the initial contaminated gaseous hydrocarbon stream is cooled in a heat exchanger to form a cooled initial contaminated gaseous hydrocarbon stream. Mainly, the gaseous stream is cooled to a temperature in the range from 0 to 40 ° C, preferably from 3 to 25 ° C, depending on the composition of the stream of gaseous hydrocarbon feed. The heat exchanger mainly uses a medium for heat transfer. Said heat exchange medium may be any available cold medium, in particular a sulfur-free natural gas stream or a liquid solution of acid contaminants.

In step a), the optionally cooled, contaminated feed stream of gaseous hydrocarbons mainly expands in volume from a pressure in the range of 70 to 200 bar to a pressure in the range of 5 to 30 bar. Typically, with this expansion, cooling will occur to a temperature that is sufficient to start liquefying acid contaminants. Preferably, the natural gas stream is cooled by expanding from a temperature in the range of −20 to 50 ° C. to a temperature of from −30 to −80 ° C. The expansion operation is carried out in such a way that solid acid impurities are not formed. This is mainly achieved by carrying out the expansion step in a temperature range of at least 3 ° C, preferably at least 5 ° C above the temperature at which the solidification of acidic contaminants begins. It should be understood that this temperature depends on the type of acid pollution, and the composition of the mixture, and pressure. One skilled in the art will be able to determine the conditions under which the expansion step is necessary.

The expansion process can be carried out by any method known to a person skilled in the art, including methods based on the use of turbo expanders, the so-called Joule-Thomson effect valves and Venturi tubes. Preferably, the gas stream is at least partially cooled during processing in a turboexpander with the release of energy. One of the beneficial effects of using a turboexpander is that in the process of practically isentropic expansion in the turboexpander, optimal cooling per pressure drop occurs, and thus energy is saved by compressing at least a portion of the gas stream with a reduced pollution content. Since the volume of the gas stream with a reduced pollution content is smaller than that of the initial gaseous stream, now that the acid pollution has been removed, the corresponding energy is such that the gas with a reduced pollution content can be compressed to an increased pressure, which is convenient for transporting gas through the pipeline.

In step b), at least a portion of the contaminants in the increased volume of the initial contaminated gaseous hydrocarbon stream can be converted into a liquid to form a dispersion of a contaminated liquid phase, still containing a small amount of hydrocarbons, and a gas phase with a reduced content of contaminants. A gas phase with a reduced pollution content may still contain a significant amount of pollution, usually up to 30%, calculated on the entire gas phase with a reduced pollution content.

The preferred way to achieve the above is to control the residence time of the increased volume gas stream between step (a) and step (c) so that at least a portion of the contaminants can turn into liquid by combining the nucleation and coagulation processes.

Thus, a dispersion of the contaminated liquid phase in the gas phase with a reduced content of contaminants is formed prior to the separation process in the first separator. Preferably, the residence time between the expander and the first separator is in the range from 0.5 to 5 s in order to ensure sufficient nucleation of the phase enriched in contaminants, followed by sufficient coagulation of the droplets to form droplets with a diameter in the micrometer range. Dispersion mainly occurs in an insulated pipe connecting the expander to the first separator.

In step (c), at least a portion of the contaminant-rich liquid phase containing hydrocarbons is separated from the gas phase with a reduced content of contaminants in the first separator.

In step (ά), the remaining hydrocarbons are separated from the liquid stream in the second separator, thereby obtaining a distillate stream containing the remaining hydrocarbons and a lower stream depleted in hydrocarbons.

In step (ά1), which takes place prior to separation in step (ά), the pressure of the liquid stream typically increases above 8 bar (0.8 MPa), preferably above 1.0 MPa and typically below 5.0 MPa, preferably below 2, 0 MPa.

Optionally, step (ά) prior to recovering the remaining hydrocarbons further includes one or more steps:

(ά2) heating, preferably at elevated pressure, a liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons, to obtain a heated liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons;

(ά3) fractionation of a preferably heated and preferably compressed liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons, to obtain a heated liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons. Fractionation can be carried out using a column with plates or a packed column, which may include a boiler at the bottom of the column and / or a refrigerator at the top of the column. Fractionation results in a distillate (upper) stream containing the remaining light hydrocarbons and impurities, and a lower stream enriched in heavier hydrocarbons. The distillate fraction may optionally be cooled and partially condensed to form a dispersion of the condensed liquid phase in the gas phase;

(ά4) reducing the pressure of a preferably heated and preferably compressed liquid stream (from a first separator), or an optionally distilled cooled dispersed phase from a fractionating column that is mainly contaminated and, in addition, containing some of the remaining hydrocarbons, and thus at least a portion is evaporated remaining hydrocarbons.

These optional steps result in a better separation of the remaining hydrocarbons.

The first and / or second separator may be any separators suitable for fraction separation. However, it has been found that two types of separators provide advantages.

One preferred type of separator that can be used as the first and / or second separator is a centrifugal separator containing a bundle of parallel channels that are located inside the rotating tube, parallel to the axis of rotation of the rotating tube.

Another preferred type of separator that can be used as the first and / or second separator is a gas-liquid separator tank containing an inlet pipe for gas / liquid at an intermediate level, an outlet pipe for liquid located below the gas / liquid inlet, and an outlet pipe for gas located above the gas / liquid inlet.

- 3 021771

Preferably, a separator is used, which contains two plates between which there are continuous vortex tubes, each of the holes in one plate at a distance below the coaxial hole in the other plate, with a swirl device provided in each vortex tube to impart a rotational movement to the gas entering the vortex tube. Such a separator is described in document EP-A 48508. The specified separator mainly contains a number of vortex tubes, which are located between two plates in the separating tank. In accordance with the recommendations of EP-B 195464, a separator according to EP-A 48508 with a coagulator, for example a mesh mist eliminator, is expediently provided. Such nets are relatively thin (have significant permeability) and have a relatively large internal surface area. After that, small droplets of liquid will coarsen and drip down the coagulator and thus ensure effective removal of the liquid. If desired, it is also possible to expose the low-pollution hydrocarbon gas to the mesh mist eliminator after exiting the vortex tubes. Therefore, it is advisable that the separator also contains a coagulator before and / or after (upstream) the vortex tubes.

In a preferred embodiment of the method of the invention, the separator includes a housing with an inlet for a cooled stream of natural gas at one end of the housing, a separating element, an exhaust outlet for gas with a reduced content of pollution at the opposite end of the housing, and an output nozzle for pollution after the separating element, where the separating element contains many channels above the part of the housing along the length of its axis, the channels of which are located around the Central axis of rotation. Suitable separators are described, for example, in documents EPB 286160, \ νϋ-Λ 2007/097621, I8-A 5667543 and νΟ-Α 2006/087332. In a preferred embodiment, a separator is provided with a tangential gas inlet. This gives the advantage that the gas is given a swirling motion and thus a preliminary separation of droplets of liquefied acid contaminants and gas is achieved. In this case, the separator is preferably provided with an additional outlet for liquid upstream of the separating element. In addition, a central gas inlet may be provided with a swirl device. Known separators can be obtained in various ways. In one special embodiment of the separator, the channels are formed from corrugated material wound on a shaft or tube. The specified material may consist of paper, cardboard, foil, metal, plastic or ceramic.

Alternatively, the separator consists of a plurality of perforated discs, where perforations in the discs form channels. These channels can be given a different hydraulic diameter and / or they are not parallel to the central axis of rotation. Although certain embodiments of such separators facilitate the arrangement of channels that are not parallel to the central axis of rotation, it is preferable to have parallel channels. The production of parallel channels is simpler, and these channels do not significantly affect the separation in the process.

In most preferred embodiments, a separator is used that includes:

1) a housing comprising a first, second and third separating sections for separating liquid from the mixture, where the second separating section is located below the first separating section and above the third separating section, the respective separating sections are interconnected, and the second separating section contains a rotating element of the coagulator;

2) a tangentially located inlet pipe for introducing the mixture into the first separating section;

3) means for removing liquid from the first separating section;

4) means for removing liquid from the third separation section, and

5) means for removing a gas stream containing a little liquid from the third separation section.

The separator may have few or many channels. The prior art separators contain a number of channels, usually in the range from 100 to 1,000,000, preferably from 500 to 500,000. The diameter of the cross-section of the channels can vary, for example, in accordance with the amount of gas, its amount and nature, the distribution of droplets in size, the amount of contamination and the desired removal efficiency. Typically, the diameter of the channels is from 0.05 to 50 mm, preferably from 0.1 to 20 mm, and more preferably from 0.1 to 5 mm. The term diameter means the doubled radius in the case of a circular cross section or the largest diagonal in the case of any other shape.

The size of the separator and in particular the size of the channels can vary in accordance with the amount of gas to be processed. EP-B 286160 indicates that separators are possible with a circumferential diameter of 1 m and an axis length of 1.5 m. The separator of the present invention can usually have a radial length in the range from 0.1 to 5 m, preferably from 0.2 to 2 m. The length along the axis is suitably from 0.1 to 10 m, preferably from 0.2 to 5 m.

For the method according to the invention, the separator usually rotates at a speed of from 100 to 3000

- 4 021771 rpm at the above temperature and pressure.

In step (e), the distillate stream containing the remaining hydrocarbons is directed to a point located before step b).

Several embodiments of the invention are possible, and in particular step (e).

Without wishing to limit the invention to specific embodiments, preferred methods of carrying out the invention, and in particular step (e), will be illustrated using FIG. 2-4. FIG. 1 does not relate to the present invention (since there is no increase in pressure of the liquid stream 9), but, nevertheless, it illustrates some elements of the present invention.

In the framework of the present description, a single position number is assigned to the pipeline, as well as to the flow passing through this pipeline. The same item numbers refer to the same or similar items.

In FIG. 1 shows a first embodiment where a stream of gaseous hydrocarbon feed is directed through a pipe 1 to a heat exchanger 2, where the stream is cooled. The resulting cooled stream of gaseous hydrocarbon feed is sent through a pipe 3 to a second heat exchanger 4, in which it is further cooled. The resulting cooled stream of gaseous hydrocarbon feed is sent through line 5 to expander 6, where the stream expands. The parts of the gaseous hydrocarbon feed stream with an increased volume in the pipeline 7 are allowed to turn into a liquid with the formation of a dispersion, and this dispersion is sent through the pipeline 7 to the first separator 8, where the separation of the polluted liquid phase containing the remaining hydrocarbons and the gas phase with a reduced content of contaminants . The contaminated liquid phase containing the remaining hydrocarbons is sent from the bottom of the first separator 8 via pipeline 9 to the heat exchanger 2, where heat is exchanged with the incoming gaseous feed stream. Then, the resulting heated liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is routed through line 10 to valve 11, where the remaining hydrocarbons undergo instant evaporation. The resulting stream, containing the contaminated liquid phase and the remaining gaseous hydrocarbons, is sent via line 12 to the second separator 13, where the remaining hydrocarbons are separated. This separation gives a distillate stream containing the remaining gaseous hydrocarbons, which is sent via line 14 to the compressor 15. The resulting compressed stream of the remaining hydrocarbons is sent through line 16 to the first heat exchanger. The flow of hydrocarbons from the first separator 8 with a low content of contaminants is directed through the pipe 17 to the second heat exchanger 4, where it is subjected to heat exchange with a cooled gaseous stream of raw materials. Received after heat transfer, a hydrocarbon stream with a low content of contaminants is sent through a pipe 18 to the compressor 19, where the stream is compressed. Compressed gas with a reduced content of contaminants is sent from the compressor through line 20.

In FIG. 2 shows a second embodiment where a stream of gaseous hydrocarbon feed is directed through a pipe 1 to a heat exchanger 2 in which the stream is cooled. The resulting cooled raw hydrocarbon gas is sent via line 3 to a second heat exchanger 4, where it is further cooled. The resulting cooled stream of gaseous hydrocarbon feed is sent through line 5 to expander 6, where the stream expands. Parts of the expanded stream of gaseous hydrocarbon feedstock in pipeline 7 are allowed to turn into a liquid with the formation of a dispersion, said dispersion being sent through pipeline 7 to a first separator 8, where the separation of the polluted liquid phase containing the remaining hydrocarbons and the gaseous phase with a reduced content of contaminants takes place. The contaminated liquid phase containing the remaining hydrocarbons is sent from the bottom of the first separator 8 via line 9 to the standby pump 23, by means of which the pressure is increased. The resulting compressed stream, enriched in contaminants, is sent via line 24 to the first heat exchanger 2, where the stream is heat exchanged with the incoming feed gas stream. Then, the resulting heated liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is routed through line 10 to valve 11, where the remaining hydrocarbons instantly evaporate. The resulting stream containing the liquid phase, enriched in contaminants, and the remaining gaseous hydrocarbons is sent through a pipe 12 to the second separator 13, where the remaining hydrocarbons are released. The result is a distillate stream containing the remaining gaseous hydrocarbons, which is sent via pipelines 14 and 5 to the expander 6. The hydrocarbon stream from the first low-pollution separator 8 is sent via pipe 17 to the second heat exchanger 4, where it is subjected to heat exchange with a cooled feed gas stream . Received after heat transfer, a hydrocarbon stream with a low content of contaminants is sent through a pipe 18 to the compressor 19, where the stream is compressed. Compressed gas with a reduced content of contaminants from the compressor is sent through line 20.

In FIG. 3 shows a third embodiment in which a stream of gaseous hydrocarbon feed is directed through a pipe 1 to a heat exchanger 2, where it is cooled. The resulting cooled hydrocarbon feed gas is directed through line 3 to a second heat exchanger 4, in which the gas is further cooled. The resulting cooled stream of gaseous hydrocarbon feed is sent through line 5 to the expander 6, in which the stream expands. Parts of the gaseous hydrocarbon feed stream with an increased volume in the pipeline 7 are allowed to turn into a liquid with the formation of a dispersion, and this dispersion is directed through the pipeline 7 to the first separator 8, in which the liquid phase enriched in contaminants and containing the remaining hydrocarbons is separated from the gas phase with a reduced pollution content.

The liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is sent from the bottom of the first separator 8 via line 9 to the standby pump 23, with which the pressure rises. The resulting compressed stream, enriched in contaminants, is sent via line 24 to the first heat exchanger 2, where the stream is heat exchanged with the incoming feed gas stream. Then, the resulting heated liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is routed through line 10 to valve 11, where the remaining hydrocarbons instantly evaporate. The resulting stream, containing a liquid phase enriched in contaminants and the remaining gaseous hydrocarbons, is sent via line 12 to a second separator 13, where the remaining hydrocarbons are released. The result is a distillate stream containing the remaining gaseous hydrocarbons, which is sent through pipelines 14 and 18 to the compressor 19, where the stream is compressed. Typically, a portion of the stream 14 (not shown in FIG. 3) is directed to a position upstream of the first separator 8, as in FIG. 1 and 2.

A low-pollution hydrocarbon stream from the first separator 8 is routed through a pipe 17 to a second heat exchanger 4, where it is heat exchanged with a cooled feed gas stream. Received after heat transfer, a hydrocarbon stream with a low content of contaminants is sent through a pipe 18 to the compressor 19, where the stream is compressed. Compressed gas with a reduced content of contaminants is sent from the compressor through line 20.

In FIG. 4 shows a fourth embodiment in which a stream of gaseous hydrocarbon feed is directed through a pipe 1 to a heat exchanger 2, where the stream is cooled. The resulting cooled feed hydrocarbon gas is sent through a pipe 3 to a second heat exchanger 4, where the gas is further cooled. The resulting cooled stream of gaseous hydrocarbon feed is sent through line 5 to expander 6, where the stream expands. The flow of gaseous hydrocarbon feed with an increased volume in the pipeline 7 is allowed to turn into a liquid with the formation of a dispersion, and this dispersion is sent through pipeline 7 to the first separator 8, in which the liquid phase enriched in contaminants and containing the remaining hydrocarbons is separated from the gas phase with a reduced content pollution.

The liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is sent from the bottom of the first separator through line 9 to the standby pump 23, by which the pressure rises. The resulting contaminant-rich stream is routed through line 24 to the first heat exchanger 2, where it is heat exchanged with the incoming feed gas stream. Then, the resulting heated liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is routed through line 10 to valve 11, where the remaining hydrocarbons instantly evaporate. The resulting stream, containing a liquid phase enriched in contaminants and the remaining gaseous hydrocarbons, is sent via line 12 to a second separator 13, where the remaining hydrocarbons are released. The result is a distillate stream containing the remaining gaseous hydrocarbons, which is sent through pipelines 14 and 7 to the first separator 8. From the first separator 8, a hydrocarbon stream with a low pollution content is sent through pipe 17 to the second heat exchanger 4, where it is subjected to heat exchange with a cooled feed stream gas. Received after heat transfer, a hydrocarbon stream with a low content of contaminants is sent through a pipe 18 to the compressor 19, where the stream is compressed. Compressed gas with a reduced content of contaminants is sent from the compressor through line 20.

In FIG. 5 shows a fifth embodiment in which a stream of gaseous hydrocarbon feed is directed through a pipe 1 to an expander 6, where the stream expands. Parts of the gaseous hydrocarbon feed stream with an increased volume in the pipeline 7 are allowed to turn into a liquid with the formation of a dispersion, and this dispersion is directed through the pipeline 7 to the first separator 8, in which the liquid phase enriched in contaminants and containing the remaining hydrocarbons is separated from the gas phase with a reduced pollution content.

The liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is sent from the bottom of the first separator 8 through a pipe 9 to a pump 23, by means of which the pressure is increased. The resulting contaminant-rich stream is sent via line 24 to the first heat exchanger 1, where it is heat exchanged with the distillate process stream from the fractionation column 26 described below. Then, the resulting heated liquid phase, enriched in contaminants and containing the remaining hydrocarbons, is sent via line 25 to a fractionation column 26 with a boiler 29. In the specified fractionation column 26 with a boiler 29, a distillate stream 27 is obtained, enriched in light components (such as methane, ethane, propane,

- 6 021771

СО ₂ and Η ₂ δ), and the lower stream from the boiler 29, enriched with heavier hydrocarbons (such as propane, butanes, pentanes and higher). Thanks to the pipeline 28, the boiler 29 receives the liquid stream from the column 26, which is heated to instantly evaporate the lighter fraction from the incoming stream. The instantly evaporated lighter fraction is sent back to the column 26 through line 30. The bottom stream is directed from the boiler through line 31. The light distillate fraction is sent through line 27 to heat exchanger 1, where it undergoes heat exchange with the lower stream from separator 8 and causes condensation of the heavier fraction with the formation of a dispersion. This dispersion passes through line 10 to optional valve 11, where the remaining hydrocarbons instantly evaporate. The resulting stream, containing a liquid phase enriched in contaminants and the remaining gaseous hydrocarbons, is sent via line 12 to a second separator 13, where the remaining hydrocarbons are released. The result is a distillate stream containing a gaseous fraction, which is sent via line 14 to the second heat exchanger 2, where it is further cooled. From the heat exchanger 2, the stream is sent through a pipe 32 to the first separator 8. The stream of purified hydrocarbons is sent from the second separator 13 through a pipe 22. A gas stream with a reduced content of contaminants from the first separator 8 is sent through a pipe 17 for heat exchange with a distillate stream from the second separator 13. Then The heated gas stream with a reduced content of contaminants is sent via line 18 to the compressor 19, where it is compressed. Compressed purified gas is sent from the compressor through line 20.

The invention will be illustrated using the following non-limiting examples.

Example 1. Comparative example.

The flow of dried contaminated natural gas (74,660 kmol / h), having the composition shown in table. 1, at a pressure of 88 bar at a temperature of 26 ° C, it is pre-cooled in a heat exchanger to 8 ° C and then expanded with a turboexpander to a pressure of 10 bar. Due to expansion, the gas temperature decreases to -54 ° C and part of the flow condenses. This two-phase stream is separated in a separator with the formation of streams containing vapor and liquid phases, the composition of which is given in table. 1. The steam stream is heat exchanged with the above-mentioned feed gas stream and subsequently compressed to a pressure of 25 bar using a compressor that is driven on the shaft of the above-described turboexpander. Subsequently, the steam is compressed in several stages to a transport pressure of 9.0 bar. The liquid stream formed in the phase separator, which is regarded as a waste stream and which can again be pumped, for example, into an underground tank, is pumped to a pressure of 80 bar before mutual heat exchange with the above-mentioned feed gas stream. From the data table. 1 we can conclude that with the flow of liquid waste 675 kmol / h of valuable hydrocarbons are lost.

Table 1. Compositions of raw materials, expanded steam and liquids

Component Molar fraction in feed gas The molar fraction in the expanded pair Molar fraction in condensed liquid Molar phase fraction 1,0 0.64 0.36 from ₂ 0.709 0.566 0.968 H ₂ 8 0.005 0.004 0.007 ν ₂ 0.005 0.008 0.0001 CH 0.270 0.410 0,020 s ₂ n ₆ 0.010 0.013 0.005

Example 2. According to the invention.

The flow of dried contaminated natural gas (74,660 kmol / h), having the composition shown in table. 2, at a pressure of 88 bar at a temperature of 26 ° C, it is preliminarily cooled in a heat exchanger to 7 ° C and then expanded with a turboexpander to a pressure of 10 bar. Due to expansion, the gas temperature drops to -55 ° C and part of the flow condenses. The expanded stream is combined with a vapor stream (4400 kmol / h) from the hydrocarbon recovery step below, described below. After that, the individual phases in the combined two-phase stream have the composition shown in table. 2. Subsequently, the combined stream is phase separated in a first separator to form steam and liquid streams. The steam stream is mutually exchanged with the above-mentioned feed gas stream and subsequently compressed to a pressure of 25 bar using a compressor that is driven on the shaft of the above-described turboexpander. Subsequently, the steam is compressed in several stages to a transport pressure of 90 bar. The liquid stream obtained in the phase separator is pumped to a pressure of 25 bar before mutual heat exchange with the above-mentioned feed gas stream and is heated to -20 ° C. The specified heated liquid stream expands to a pressure of 10 bar, which causes the evaporation of part (16 mol.%) Of the liquid. Subsequently, a two-phase flow (27570 kmol / h) is phase separated in a second separator. The composition of the obtained liquid and gas are given in table. 3. The vapor stream from the separator is combined with the feed in the first phase separator. The liquid stream is pumped to a pressure of 80 bar and discharged as a waste stream, for example, for re-pumping into an underground tank. From the data table. 3 we can conclude that with the flow

- 7 021771 liquid wastes, only 183 kmol / h of valuable hydrocarbons are lost.

Table 2. Composition of raw materials, expanded steam and liquids

Component Molar fraction in feed gas Molar fraction in a pair of combined * stream Molar fraction in the liquid of the combined * stream Molar phase fraction 1,0 0.64 0.36 SO _g 0.709 0.579 0.969 H ₂ 5 0.005 0.004 0.007 ν ₂ 0.005 0.007 0.0001 SI 0.270 0.397 0.019 from ₂ n „ 0.010 0.013 0.005

* Combined advanced stream and extracted steam stream.

Table 3. Composition of expanded steam and liquids from the hydrocarbon recovery section

Component The molar fraction in the expanded pair Molar fraction in increased fluid volume Gas phase fraction 0.16 0.84 CO ₂ 0.889 0.985 H ₂ 5 0.006 0,0007 ν ₂ 0,0007 0.00001 CH ₄ 0,093 0.0044 C ₂ H ₆ 0.011 0.0035

Example 3. Comparative example.

The flow of dried contaminated natural gas (29960 kmol / h) having the composition shown in table. 4, at a pressure of 88 bar at a temperature of 26 ° C, it is pre-cooled in a heat exchanger to 8 ° C, and then expanded with a turboexpander to a pressure of 10 bar. Due to expansion, the gas temperature decreases to -54 ° C and part of the flow condenses. Then the two-phase stream is subjected to phase separation in the separator with the formation of streams containing steam and liquid, the composition of which is given in table. 4. The steam stream is subjected to mutual heat exchange with the above raw gas stream and subsequently compressed to a pressure of 25 bar using a compressor, which is driven on the shaft of the above turbine expander. Subsequently, the steam is compressed in several stages to a transport pressure of 90 bar.

The liquid stream formed in the phase separator, which is regarded as a waste stream and which can again be pumped, for example, into an underground tank, is pumped to a pressure of 80 bar before mutual heat exchange with the above-mentioned feed gas stream. From the data table. 4, it can be concluded that 449 kmol / h of valuable hydrocarbons are lost with the flow of liquid waste.

Table 4. Compositions of raw materials, expanded steam and liquids

Component Molar fraction in feed gas The molar fraction in the expanded pair Molar fraction in condensed liquid Molar phase fraction 1, about 0.70 0.30 CO ₂ 0,095 0,097 0,089 H ₂ 3 0.332 0,112 0.855 ν ₂ 0.004 0.005 0 SS 0.559 0.777 0.04 s ₂ n ₆ 0.006 0.007 0.004 C ₃ n ₈ 0.002 0.001 0.002 Iso-C ₄ Ny 0,0007 0,0002 0.002 nC ₄ N | o 0,0008 0.0001 0.002

Example 4. According to the invention.

The flow of dried contaminated natural gas (29960 kmol / h) having the composition shown in table. 5, at a pressure of 122 bar at a temperature of 30 ° C, it is preliminarily cooled in a heat exchanger to 11 ° C and then expanded with a turboexpander to a pressure of 14 bar. Due to expansion, the gas temperature decreases to -54 ° C and part of the flow condenses. The expanded stream is combined with a steam stream (1133 kmol / h) from the hydrocarbon recovery step below, described below. After that, the individual phases in the combined two-phase stream have the composition shown in table. 5. Subsequently, the combined stream is phase separated in the first separator to form steam and liquid streams. The steam stream is mutually exchanged with the above-mentioned feed gas stream and subsequently compressed to a pressure of 34 bar using a compressor that is driven on the shaft of the above-described turboexpander, subsequently the gas flows to the next stage in the general chain of separation processes, for example, with solvent treatment .

- 8 021771

The liquid stream obtained in the phase separator is pumped to a pressure of 60 bar, until the heat exchange with the above-mentioned feed gas stream is mutual, and at the same time it is heated to -9 ° C. The specified heated liquid stream expands to a pressure of 14 bar, which causes the evaporation of part (13 mol.%) Of the liquid. Subsequently, a two-phase flow (8769 kmol / h) is phase separated in a second separator. The composition of the obtained liquid and gas are given in table. 6. The vapor stream from the separator is combined with the feed in the first phase separator. The liquid stream is pumped to a pressure of 215 bar and is discharged as a waste stream, for example, for re-injection into an underground tank. From the data table. 6, it can be concluded that only 160 kmol / h of valuable hydrocarbons are lost with the liquid waste stream.

Table 5. Composition of raw materials, expanded steam and liquids

Component Molar fraction in feed gas Molar fraction in paired combined * stream Molar fraction in the liquid of the combined * stream Molar phase fraction 1,0 0.71 0.29 CO ₂ 0,095 0.105 0,086 H ₂ 3 0.332 0.128 0.860 N2 0.004 0.005 0 SND 0.559 0.754 0,036 with ₂ n 0.006 0.007 0.004 C ₃ H ₈ 0.002 0.001 0.004 IZO-SdNyu 0,0007 0,0002 0.002 N-SdN | g, 0,0008 0,0002 0.002

* Combined advanced stream and extracted steam stream

Table 6. Composition of expanded steam and liquids from the hydrocarbon recovery section

Component The molar fraction in the expanded pair Molar fraction in increased fluid volume Gas phase fraction 0.13 0.87 CO ₂ 0.222 0,065 H ₂ 3 0.547 0.908 ν ₂ 0,0002 0 SND 0.214 0.009 s ₂ n ₆ 0.010 0.003 C ₃ n ₈ 0.004 0.004 iso-cdnu 0,0008 0.002 nSdNu 0,0007 0.003

Example 5. Comparative example.

The flow of dried contaminated natural gas (29970 kmol / h) having the composition shown in table. 7 under a pressure of 147 bar at a temperature of 30 ° C is expanded by means of a turboexpander to a pressure of 15 bar. Due to expansion, the gas temperature drops to -46 ° C and part of the flow condenses. Then the two-phase stream is subjected to phase separation in the separator with the formation of streams containing steam and liquid, the composition of which is given in table. 7. The vapor stream is compressed to a pressure of 47 bar using a compressor that is driven on the shaft of the turbine expander described above. Subsequently, the steam is compressed to a transport pressure of 90 bar.

The liquid stream formed in the phase separator, which is regarded as a waste stream and which can again be pumped, for example, into an underground tank, is pumped to a pressure of 215 bar. From the data table. 7 it can be concluded that with the flow of liquid waste, 1,681 kmol / h of valuable hydrocarbons are lost.

Table 7. Compositions of raw materials, expanded steam and liquids from the first separator

Component Molar fraction in feed gas The molar fraction in the expanded pair Molar fraction in condensed liquid Molar phase fraction 1, about 0.66 0.34 CO ₂ 0.21 0.21 0.21 H ₂ 3 0.30 0.13 0.62 ν ₂ 0.017 0,026 0,0004 SND 0.42 0.60 0,054 s ₂ n ₆ 0,026 0,026 0,026 C ₃ n ₈ 0.008 0.003 0.018 iso-cdnu 0.002 0,0002 0, C06 nSdNu 0.002 0,0002 0.006 IZO-S3N12 0.002 0 0.006 n-sznc 0.002 0 0.006 nC ₆ H ₁₄ 0.003 0 0.009 N-S7N1Y 0.012 0 0,034

- 9 021771

Example 6. According to the invention.

The flow of dried contaminated natural gas (29970 kmol / h) having the composition shown in table. 8, under a pressure of 147 bar at a temperature of 30 ° C is expanded by means of a turboexpander to a pressure of 15 bar. Due to expansion, the gas temperature drops to -46 ° C and part of the flow condenses. The expanded stream is combined with a vapor stream (3126 kmol / h) from the hydrocarbon recovery step below, described below. After that, the individual phases in the combined two-phase stream have the composition shown in table. 8. Subsequently, the combined stream is phase separated in a first separator to form steam and liquid streams. The steam stream is mutually exchanged with the distillate stream from the second separator located after the hydrocarbon recovery step described below and subsequently compressed to a pressure of 77 bar by a compressor that is driven on the shaft of the turbine expander described above; then the gas enters the next step in the general chain of separation processes, for example, with solvent treatment.

The liquid stream obtained in the first phase separator is pumped to a pressure of 18 bar until mutual heat exchange with the distillate stream from the fractionation column below, described below, is heated to approximately 1 ° C. The specified stream enters the fractionation column with plates and a boiler, in which at a temperature of 185 ° C a stream (619 kmol / h) is obtained, enriched in heavy hydrocarbons. The composition of this stream is given in table. 9. The distillate flow of the fractionation column with a temperature of about 5 ° C is subjected to heat exchange with the feed stream of the fractionation column, which causes condensation of the heavier components to form a dispersion. The specified dispersion (11090 kmol / h) is subsequently subjected to phase separation in a second separator. The composition of the obtained liquid is given in table. 9. The liquid stream is pumped to a pressure of 215 bar and discharged as a waste stream, for example, for re-injection into an underground tank. From the data table. 9, it can be concluded that only 456 kmol / h of valuable hydrocarbons are lost with the liquid waste stream. The distillate vapor stream from the second separator is heat exchanged with the distillate vapor stream from the first separator and combined with the feed for the first separator.

Table 8. Compositions of raw materials, expanded steam and liquids from the first separator

Component Molar fraction in feed gas Molar fraction in steam combined stream * Molar fraction in the liquid combined stream * Molar phase fraction 1,0 0.64 0.36 CO ₂ 0.21 0.23 0.23 H ₂ 3 0.30 0.13 0.61 ν ₂ 0.017 0.024 0,0004 CH ₄ 0.42 0.58 0.051 C ₂ n ₆ 0,026 0,029 0,028 S _e n " 0.008 0.003 0.018 IZO-S4N10 0.002 0,0003 0.005 H-C4H10 0.002 0,0002 0.005 IZO-S5N12 0.002 0 0.005 N-SzN | ₂ 0.002 0 0.005 n-sbnn 0.003 0 0.008 H-S7N16 0.012 0 0,029

* Combined advanced stream and extracted steam stream

Table 9. Composition of expanded steam and liquids from the hydrocarbon recovery section

Component Molar fraction in the bottom stream of the fractionation column Molar fraction in the liquid stream from the second separator The molar fraction of the gas phase - 0.71 CO ₂ 0 0.17 H ₂ 8 0.002 0.77 ν ₂ 0 0 CH ₄ 0 0.009 s ₂ n ₆ 0 0,020 s ₃ n ₈ 0.005 0,021 IZO-S4N10 0,054 0.003 ns „n ₁₀ 0,066 0.002 IZO-C5H | ₂ 0,080 0.001 HC ₅ N ₁₂ 0,085 0,0009 HC ₆ NC 0.14 0,0004 HC ₇ H ₁₆ 0.56 0,0006

Claims (5)

CLAIM 1. A method of producing a gas stream with a reduced content of contaminants from an initial contaminated stream of gaseous hydrocarbons containing at least 10 vol.% Acid contaminants, in particular Η ₂ δ and CO ₂ , the method comprising the steps of: (a) expanding the original contaminated gaseous hydrocarbon stream in the expander to obtain an increased volume of the original contaminated gaseous hydrocarbon stream; (b) provide liquefaction of at least a portion of the contaminants in an increased volume of the initial contaminated gaseous hydrocarbon stream to form a dispersion of a liquid phase enriched in contaminants and still containing a small amount of hydrocarbons, and a gas phase with a reduced content of contaminants; (c) at least a portion of the contaminant-rich liquid phase containing hydrocarbons is recovered from the gaseous phase with a reduced content of contaminants in the first separator, and thereby a gaseous stream with a reduced content of contaminants and a liquid stream containing mainly contaminants and, in addition, are obtained containing the remaining hydrocarbons; (b) recovering the remaining hydrocarbons from the liquid stream in a second separator, and thereby obtaining a distillate stream containing the remaining hydrocarbons and a lower stream depleted in hydrocarbons; (e) directing the distillate stream containing the remaining hydrocarbons to a point located prior to step (c); wherein step (b), prior to recovering the remaining hydrocarbons, further comprises a step (b1), in which the pressure of the liquid stream containing mainly contaminants and, in addition, containing the remaining hydrocarbons is increased to obtain a compressed liquid stream containing mainly contaminants and, in addition containing the remaining hydrocarbons. 2. The method according to claim 1, in which stage (b) to the allocation of the remaining hydrocarbons further includes one or more stages, in which: (62) preferably, at an elevated pressure, a liquid stream, mainly containing impurities and, in addition, containing remaining hydrocarbons, is heated to obtain a heated liquid stream, mainly containing impurities and, in addition, containing remaining hydrocarbons; (63) fractionating a preferably heated and preferably compressed liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons, to obtain a heated liquid stream, mainly containing impurities and, in addition, containing the remaining hydrocarbons; (64) reduce the pressure of a preferably heated and preferably compressed liquid stream or an optionally distilled cooled dispersed phase from a fractionating column which is mainly contaminated and, in addition, containing a portion of the remaining hydrocarbons, whereby at least a portion of the remaining hydrocarbons is evaporated. 3. The method according to claim 1 or 2, in which in stage (e) the distillate stream is cooled, optionally compressed and combined with the original contaminated stream of gaseous hydrocarbons and the resulting combined stream is sent to stage (a). 4. The method according to claim 1 or 2, in which the distillate stream in stage (e) is directed to the compressor before being fed to the point located before stage (c). 5. The method according to claim 1 or 2, in which the distillate stream from the second separator is combined with the liquid phase enriched in impurities obtained after stage (a), and the combined stream is sent to the first separator. 6. The method according to any one of claims 1 to 5, in which the first and / or second separator is a centrifugal separator containing a bunch of parallel channels that are located inside the rotating tube parallel to the axis of rotation of the rotating tube. 7. The method according to claim 6, in which a vortex gas stream is introduced into the rotating tube. 8. The method according to any one of claims 1 to 7, in which the first and / or second separator is a separation device, including: 1) a housing containing the first, second and third separation sections for separating liquid from the mixture, where the second separation section is located below the first separation section and above the third separation section and the corresponding separation sections are interconnected, the second separation section containing a rotating element of the coagulator; 2) a tangentially located inlet pipe for introducing the mixture into the first separating section; 3) means for removing liquid from the first separating section; 4) means for removing liquid from the third separation section, and 5) means for removing a gas stream containing a little liquid from the third separation section. 9. The method of claim 8, in which the liquid is isolated from the gas phase by moving drops under - 11 021771 by the action of centrifugal force to the inner wall of the first separation section, and using the inner wall, the liquid is removed from the separation device or sent to the liquid collection section, which is located below the third separation section. 10. The method according to claim 9, in which the liquid is separated from the gas phase by moving droplets under the action of centrifugal force to the inner wall of the first separating section and using the inner wall, the liquid is sent to the liquid collection section, which is located below the third separating section. 11. The method according to any one of claims 8 to 10, in which the liquid is separated from the gas phase by moving droplets under the action of centrifugal force to the inner wall of the third separating section and using the inner wall, the liquid is removed from the separation device or output to the liquid collection section, which is located below the third dividing section. 12. The method according to any one of claims 1 to 5, in which the first and / or second separator is a gas-liquid separation tank, which includes a pipe for gas / liquid inlet at an intermediate level, an outlet pipe for liquid, which is located below the inlet pipe gas / liquid and a gas outlet that is located above the nozzle for gas / liquid inlet. 13. The method according to item 12, in which the tank of the gas-liquid separator is usually equipped with a horizontal coagulator located above the gas / liquid inlet and over the entire cross section of the tank, and in the specified tank, the centrifugal liquid separator is located above the coagulator and over the entire cross section of the tank, and the liquid separator comprises one or more vortex tubes. 14. The method according to item 12 or 13, in which the inlet pipe for gas includes access with a supply and distribution unit, elongated horizontally in the separator tank, and the unit is a longitudinal box-shaped structure connected to an inlet pipe for gas and having at least at least one open vertical side with a network of guide vanes located one after the other in the direction of flow. 15. The method according to item 13 or 14, in which the horizontal coagulator contains one or more layers of a mesh, especially a metal or non-metallic mesh, or a combination thereof.