Abstract:
A method is proposed for operating a plant for purifying a high-pressure gas mixture from easily permeating components, which plant comprises membrane gas separating units having a high-pressure chamber and a low-pressure chamber with a selectively permeable membrane therebetween, in which method the low-pressure chamber of at least one membrane gas separating unit is continuously flushed with purified gas mixture (semi-finished product or product), wherein the pressure difference between the aforementioned chambers of the membrane gas separating unit and, likewise, the flow rate of the purified gas mixture used for flushing are maintained so that the amount of each easily permeating component in the product does not exceed the desired values. The proposed method makes it possible to purify a raw material from one or more easily permeating components simultaneously, increase purification efficiency, and provide the possibility of using raw material with a higher content of easily permeating components.

Description:
RELATED APPLICATIONS 
       [0001]    This Application is a Continuation application of International Application PCT/RU2011/000888, filed on Nov. 11, 2011, which in turn claims priority to Russian Patent Applications No. RU 2010146784, filed Nov. 18, 2010, RU 2010146786, filed Nov. 18, 2010, RU 2011103090, filed Jan. 28, 2011, RU 2011103091, filed Jan. 28, 2011, RU 2011116894, filed Apr. 28, 2011, RU 2011116895, filed Apr. 28, 2011, RU 2011119725, filed May 17, 2011, RU 2011127531, filed Jul. 6, 2011, RU 2011127529, filed Jul. 6, 2011 all of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The inventions group relates to the field of gas mixtures separation by selectively permeable membranes (SPMs) and can be applied in gas, oil, chemical and other industrial fields. 
       BACKGROUND OF THE INVENTION 
       [0003]    Majority of tasks on purification of hydrocarbon gas mixtures require simultaneous treatment of a raw material as the HPGM (high-pressure gas mixture) from several components simultaneously, herewith the purification process as a rule has to be carried out without significant pressure loss of the HPGM and with minimum raw material losses (i.e. with maximum product yield, the term product refers to the raw material purified to set parameters). 
         [0004]    For example, natural gas supplied to the main pipelines must correspond with the industrial standards related in this technical field on the limit contents of several components namely, the content of hydrogen sulphide, merkaptans, CO2, water vapours and condensing hydrocarbons. For the moderate climate the limiting mass concentration of hydrogen sulphide in gas mixture per OST 51.40-93 must be no more than 7 mg/m 3 , merkaptans must be no more than 16 mg/m 3 , molar part of CO2 must be no more than 2.5% mole, hydrocarbon dew point must be no higher than minus 2° C., water dew point must be no higher than minus 10° C. The requirements to the limiting contents of water vapours and condensing hydrocarbons are more stringent for regions with cold climate with the same requirements to hydrogen sulphide, merkaptans and CO2: hydrocarbon dew point must be no higher than minus 5.0° C. in summer and minus 10.0° C. in winter, dew point for water must be minus 14° C. in summer and minus 20.0 ° C. in winter. 
         [0005]    Besides high yield of the finished product the gas separation processes must provide as low energy consumption as possible per product unit (the specific energy consumption). Thus it is necessary to minimize the energy consumption at the compressors&#39; actuation (active equipment), heat-exchange (heating and cooling), and also increase the productivity of the passive equipment, first of all the square area unit of a selectively permeable membrane (SPM). 
         [0006]    There&#39;re SPMs with gas separation layer made of silica organic materials with high ratio of water vapours diffusion rate to methane diffusion rate and low ratio of butane, hydrogen sulphide, merkaptans, helium rate to methane diffusion rate. These membranes are efficient only for drying of hydrocarbon mixtures. 
         [0007]    Composite membranes to be used for simultaneous treatment of a raw material (HPGM) from water vapours, acid gases and heavy hydrocarbons have selective layers made of block copolymers, consisting of elastic and rigid blocks, for example, membranes made of polyoxyethylene copolymers with polyamide PEG (PEBAX®), polyester and polymide (Polyactive®) etc. With the certain ratios of elastic and rigid membrane block the above mentioned polymers have high selectivity values with preservation of high enough specific permeability. For example, membranes with the selectivity values α (H 2 O)/(CH 4 )≧280, α (He)/(CH 4 )≧150, α (MS)/(CH 4 )≧65 (where MS—merkaptans sum), α (H 2 S)/(CH 4 )≧40, α (C 6 H 14 )/(CH 4 )≧25 possess specific permeability of methane at a temperature of 25.0° C.−P/1(CH 4 )≧30 l/m  2 h atm. Herewith the selectivity values of this membrane on all components are higher than the corresponding values of selectivity of the best silica organic membranes. For example, membrane selectivity values (specific permeabilities ratio) made of polydimethyle siloxane (Lestosil), compose α (H 2 O)/(CH 4 )≦25, α (He)/(CH4)≦2, α (H 2 S)/(CH 4 )≦8. 
         [0008]    Selective properties of the SPM have decisive significance in the processes of the membrane gas separation. This can be illustrated by the results of numerical modeling of the hydrogen sulphide recovery process from multi-component hydrocarbon mixture represented at  FIG. 1 , from which it leads that at actual pressure differences at the SPM the product yield (purified gas mixture with the required specifications) per hydrogen sulphide (7 mg/m 3  per OST 51.40-93) primarily depends on the selectivity values α (H 2 S)/(CH 4 ), herewith the acceptable yields ≧80% can be achieved only at α (H 2 S)/(CH 4 )&gt;50. Membranes with such selectivity do not exist at the present time. Therefore it is necessary to find approaches to increase the gas separation efficiency and to improve the gas separation plants characteristics for implementation of the less energy-demanding single-stage membrane separation process. One of these methods is flushing or sweeping of a low-pressure chamber of a membrane gas separating module (MGSM LPC) for decreasing of the partial pressure of the undesired component downstream the selectively permeable membrane. 
         [0009]    The method of gas mixtures separation is known from description in the RF Patent for the invention No 2132223, wherein membrane gas separation units (MGSU) with a high-pressure chamber (HPC) and a low-pressure chamber (LPC) are used, separated by the SPM, the raw material (HPGM) goes to the MGSU HPC inlet, and portion of a non-permeate withdrawn from the HPC outlet goes to sweeping of the LPC in the counter-flow direction. The objective of the known technical solution is minimization of the membrane area for single-component purification, i.e. increase of the membrane productivity. However the decrease of the SPM total area proportional to the increase of productivity of the SPM in the plant with certain productivity on the product stripped from one of the components only does not allow to practically obtain the product that would correspond with the requirements on the limiting contents of several non-desired components. Concentrations of non-desired components even though are small, but as a rule differ from each other significantly. If the raw material contains one component in concentration, for example, 0.01 g/m 3 , and another one in concentration, for example, 0.1 g/m 3 , then with comparable selectivity of the SPM to both components, the unit with reduced area of the SPM will not be efficient for stripping of the product from the second component, in comparison with the plant without sweeping, wherein the SPM has larger total square area. 
         [0010]    As the modeling results provided at  FIG. 2  show at the set pressure of the initial gas and set ratio of pressures in the HPC and the LPC of the MGSU b=P(high)/P(low)=20 the sweeping of the LPC with portion of the non-permeate (approximately 15%) increases the product yield (natural gas stripped from hydrogen sulphide) by use of membranes with selectivity of more than 20, herewith at use of membranes with selectivity of less than 20 the yield of the product decreases. The provided results make clear that the LPC sweeping significantly increases the product yield with the required characteristics of hydrogen sulphide. In particular, the product yield increases 80% for actually existing membranes with selectivity α (H 2 S/CH 4 )≈40. Thus the task of the single-stage purification of hydrocarbon mixture from hydrogen sulphide is solved only by membranes with high selectivity and by sweeping of the LPC. 
         [0011]    Relations, given at  FIG. 1 , are universal and apply to any impurity (water, merkaptans, helium, C 5 + etc.), stripped from the hydrocarbon mixture. 
       SUMMARY OF THE INVENTION 
       [0012]    The objective of the invention is to obtain methods and plants for purification of the high-pressure gas mixture simultaneously from several components of different chemical origin, even if the quantative contents in the raw material vary significantly and also to increase the efficiency of this purification process. 
         [0013]    Terms and expressions used in this text have the following meaning. 
         [0014]    A non-permeate denotes non-permeating gas flow stripped from the easily permeating components and enriched with hard permeating components . 
         [0015]    A permeate is the gas flow that permeated enriched with easily permeating components. 
         [0016]    A membrane gas separation module (MGSM) is a plant for the separation (purification) of the HPGM comprising a high-pressure chamber (HPC) and a low-pressure chamber (LPC) with a selectively permeable membrane (SPM) therebetween. 
         [0017]    The term chamber is referred to chambers, sections, channels or any known medium for supply of the gas mixture with high content of easily permeating components at the SPM and collection of the gas mixture permeated through the SPM with decreased content of the easily permeating components. One of the possible particular forms of the MGSM implementation is shown at  FIG. 2  and described in the text below. 
         [0018]    A membrane gas separation unit (MGSU) is a unit comprising at least one MGSM or at least two MGSMs, inputs and outputs of which are interconnected for the mutual feed or withdrawal of the gas mixtures into/from the MGSU and/or for distribution of the intermediate flows of the gas mixtures between the MGSMs inside the MGSU. HPCs and LPCs of different MGSMs in the MGSU can be connected in parallel, in series, parallel-and-in-series and/or in series-and-parallel based on gas flows. 
         [0019]    Head MGSUs in plants comprising several MGSUs refer to the MGSUs at inlet of the HPCs whereof the HPGM is supplied with increased (in relation to flows supplied at inlet of the HPC of other MGSUs) contents of easily permeating components. In other words, if, for example, the plant comprises at least two MGSUs, then the first MGSU in the direction of the purified HPGM flow is the head MGSU. 
         [0020]    Tail MGSUs in plants comprising several MGSUs, refer to the MGSU, wherein the HPGM is supplied with decreased contents of the easily permeating components at the HPC inlet (in relation to flows supplied to the HPC inlet of other MGSUs). In other words, if, for example, the plant comprises at least two MGSUs, then the last MGSU downstream the purified HPGM flow is the tail MGSU. 
         [0021]    A high-pressure chamber (HPC) is a chamber, section and/or any structurally isolated space dedicated mainly for connecting of HPGM, to the SPM of at least one MGSM. 
         [0022]    A low-pressure chamber (LPC) is a chamber, section and/or any structurally isolated space dedicated mainly for collection and takeoff of the gas flow permeated through the SPM of at least one MGSM. 
         [0023]    A sweep gas (or sweep gas flow) is referred to portion of the non-permeate collected at the outlet from the HPC of at least one MGSM and/or MGSU, which is used for sweeping of the LPC of at least one MGSM. 
         [0024]    A discharge flow (discharge gas or discharge) is referred to gas flow taken from the LPC of at least one MGSM and/or MGSU and that is represented by permeate or mixture of permeate and sweep gas. 
         [0025]    A product is referred to gas flow, namely, the non-permeate collected at the outlet from the LPC of at least one MGSM and/or MGSU with the required composition (concerning quality and quantity). 
         [0026]    A semi-finished product is referred to the gas flow, namely, the non-permeate collected at the outlet of the HPC of one or several MGSUs and/or MGSMs except the tail ones. 
         [0027]    A vacuum compressor (VC) is a unit for decreasing of pressure and supply of the gas mixture from its inlet to its outlet at increased pressure. 
         [0028]    A high-pressure gas mixture (HPGM) refers to the gas mixture supplied at the HPC inlet of the MGSM or the MGSU for further treatment from the easily permeating components. 
         [0029]    A selectively permeable membrane (SPM) is a layer of material providing different rates of permeability of different components of the gas mixture of different chemical origin. 
         [0030]    Other terms and expressions have meanings as regular for the context and the given technical field. 
         [0031]    Technical result comprises the possibility of the simultaneous raw material (HPGM) purification from one or several easily permeating components(s) (in particular, helium, hydrogen sulphide, merkaptans, carbon dioxide, water and/or heavy hydrocarbons), increase of the purification efficiency (i.e. ratio between the total area of the SPM in the plant, the productivity of said membrane and the specific energy consumption of the gas separation process); and providing of the possibility of using (treating or preparing) raw material with a higher content of the easily permeating components. 
         [0032]    The above-mentioned technical result is achieved by implementation of the plant operation type for purification of the high-pressure gas mixture (HPGM) from the easily permeating components , comprising membrane gas separating units (MGSUs) with a high-pressure chamber (HPC), with a low-pressure chamber (LPC) and a selectively permeable membrane (SPM) therebetween, wherein the LPC of at least one of the MGSUs is swept with a purified gas mixture (semi-finished product or product), wherein the pressure difference between the aforementioned chambers of this MGSU, and ,likewise, the flow rate of the purified gas mixture used for sweeping, are maintained so that the amount of each easily permeating component in the product does not exceed the desired values. 
         [0033]    Taking the above into account it is clear that the increase of efficiency of purification of the high-pressure gas mixtures is restrained by the limiting selectivity of existing SPMs. Besides, sweeping of the LPC allows to increase product yield only at values of selectivity of the SPM above the certain limit for all components. Herewith high product yield is achievable due to non-linear dependency of the SPM selectivity and any of the components from the operating pressure difference between high- and low-pressure chambers, only due to the selection of the certain pressure difference between the LPC and the HPC and certain ratio of the sweep gas and the permeate flow purified simultaneously from several components of the gas mixture, without increase of the stages number and use of additional active equipment. Also, in some cases, for increase of the gas separation efficiency it may be useful to provide high absolute pressure values in chambers (for example, for increasing difference in the concentration of the permeating components in the gas mixtures at different sides of SPM) together with provision of the certain pressure difference in between the chambers. 
         [0034]    The gas separation is accomplished so that the value of the ratio of specific permeabilities of the SPM (amount of matter or volume of the gas permeated a unit of area of the SPM at a unit of time and at a unit of pressure, mole/m 2  sec Pa or m 3 /m 2  sec Pa) for each easily permeating component to the specific permeability of SPM in relation to all hard permeating components and/or to main hard permeating component exceeded the ratio of pressures in the high-pressure and the low-pressure chambers of the MGSU. 
         [0035]    High-pressure chambers of several membrane gas separating units of the plant can be connected between each other differently, in particular, in series. 
         [0036]    The HPC of at least one additional MGSU may be connected in parallel to the HPC of at least one of the MGSUs or at least one membrane gas separating unit (MGSU) comprises at least two membrane gas separating modules (MGSM), each of them in its turn comprises a high-pressure chamber (HPC), a low-pressure chamber (LPC) and a SPM therebetween herewith inlets and outlets of the LPC and the HPC of said MGSU or inlets and outlets of said MGSMs are interconnected in parallel. 
         [0037]    The gas mixture (discharge flow) from the LPC outlet of at least one of MGSU can be supplied to the HPC inlet of another MGSU by sweeping with semi-finished product of the LPC of both MGSUs. 
         [0038]    For provision of optimum pressure, gas mixtures supplied to the HPC inlet of at least the first of the head MGSU can be preliminarily compressed. 
         [0039]    In one of the particular implementation forms the gas mixture supplied to the HPC inlet can be pre-cooled for example for removal of the excessive heat from the gas compression or for water vapours or hydrocarbons condensation. 
         [0040]    The gas mixtures supplied to the HPC inlet can be preliminarily separated and filtrated for example for condensed moisture and/or mechanical contamination removal. 
         [0041]    The gas mixtures supplied to the HPC inlet can be preliminarily heated for example after pre-cooling and before supply of the gas mixture to the high-pressure chamber of the MGSU. It is preferable when the gas mixture is heated to temperature at which the maximum efficiency of the applied SPM is achieved. 
         [0042]    The gas mixtures supplied to the HPC inlet, may be preliminarily compressed and/or preliminarily compressed, and then cooled and/or preliminarily compressed, then cooled, then separated, and then filtrated and/or preliminarily compressed, then cooled after that separated then filtrated and then heated. 
         [0043]    The pressure decrease below the atmosphere pressure can be provided in the LPC of at least the first of the head MGSU. 
         [0044]    It is preferable when said pressure decrease below the atmosphere pressure is obtained in the LPC of the head MGSU. 
         [0045]    Sweeping can be arranged in particular in such a way so that the purified gas mixture from the HPC outlet of at least one of MGSU is used for sweeping of the LPC of at least one of the preceding MGSU i.e. product or semi-finished product from the HPC outlet of at least one of the MGSU can be used for sweeping of the LPC of at least one or more preceding MGSUs. It can be beneficial for example for decrease of non-production hydraulic losses at the non-permeate throttling from the HPC to the adjoining LPC for the non-permeate pressure relief (sweeping flow) as the non-permeate (sweeping flow) pressure in the tail stages (if the non-permeate is not compressed in between MGSUs) is usually closer to pressure that is necessary to be provided in the LPC than the non-permeate pressure from the head MGSU due to the natural hydraulic losses in the MGSM. Besides it allows to increase the motion force of the separation process in the head MGSUs as in this case the LPC will be swept with more purified non-permeate than the non-permeate from the head MGSUs HPCs. 
         [0046]    Herewith it is preferable when the purified gas mixture from the HPC outlet of at least one MGSU is used for sweeping of the LPC of at least the first of the head MGSUs. 
         [0047]    The pressure of the gas mixture used for the LPC sweeping as a rule is decreased beforehand. The pressure decrease may not be needed if portion of the non-permeate with low pressure at the outlet from the HPC of the MGSU of the tail stages is used as sweep gas. 
         [0048]    The gas mixtures from the outlet of the LPC of at least one MGSU can be directed to the HPC inlet of at least one of the preceding MGSU for the further re-processing thus recycling is provided and emissions are reduced. 
         [0049]    It is preferable when the gas mixtures from the LPC outlet of at least one MGSU are directed to the HPC inlet of at least the first of the head MGSU. 
         [0050]    The pressure of the purified gas mixture before sweeping of the LPC can be decreased by different means, for example, by a throttling unit, a porous body or an orifice. 
         [0051]    If the SPM productivity is influenced not only by the pressure difference between the HPC and the LPC of the MGSU but also by absolute pressure values in the MGSU chambers (gas compression increases components concentration and diffusion rate through the SPM), in this case increase of pressure in the HPC in order to prevent the SPM damage may be compensated by adequate pressure increase in the LPC so that it provides not only high pressure difference between chambers (not exceeding strength limit of the SPM) but also high components concentration in the HPGM. 
         [0052]    The purified gas mixture (sweep gas) can be used for sweeping by a compressor or a vacuum compressor. 
         [0053]    If the MGSU productivity is increased by increase of absolute pressure values not only in the HPC but also in the LPC (at maintaining pressure difference not exceeding the strength limit of the SPM), then sweeping of the LPC with the non-permeate from tail MGSUs by a compressor or a vacuum compressor (if it is needed for increase of the non-permeate pressure from the tail MGSU till the required value) may provide for the additional improvement of the gas separation efficiency. 
         [0054]    Pressure decrease below the atmosphere pressure in the LPC may be obtained by a vacuum compressor. 
         [0055]    Selectively permeable membranes used in the above described method may be accomplished as semi-permeable hollow fibers or flat membranes installed at a frame or spiral-wound membranes. Hollow fiber membranes are preferable. 
         [0056]    The discharge flow can be handled differently. The gas mixture from the LPC outlet (discharge flow) of at least one MGSU can be used for power supply (if the latter contains sufficient amount of flammable hydrocarbons) and/or can be compressed and directed to utilization and/or to storage and/or downhole injected (for example, for increase of productivity) and/or can be re-processed. 
         [0057]    The purified gas mixture from the HPC of at least one MGSU is directed to the consumer. The non-permeate from the outlet of the tail MGSU (with contents of all components not higher than the specified values) or the non-permeate of intermediate MGSUs or their mixture can be used as product depending on the objective. 
         [0058]    It is preferable when the purified gas mixture is directed to the consumer from the HPC of at least one of the tail MGSUs, preferable from the HPC of the tail MGSU. 
         [0059]    In order to increase the raw material processing rate, condensate from separation can be stabilized by dividing into the stabilized gas, hydrocarbon condensate and water. 
         [0060]    Stabilized gas can be used at the HPC inlet of at least the first of the head MGSUs preferably at the HPC inlet of the first MGSU. 
         [0061]    The flows from stabilization can be handled differently. It is preferable that the discharge gas generated during stabilization is directed to utilization, stable hydrocarbon condensate is directed to re-processing or downhole injected and water condensate is downhole injected for maintaining of formation pressure or is directed to utilization. 
         [0062]    The above-described method can be implemented with a plant comprising two MGSUs wherein the HPGM is fed to the HPC of the first MGSU, the gas mixture from the HPC of the first MGSU is fed to the HPC of the second MGSU, the gas mixture from the LPC outlet of the second MGSU is fed to the HPC inlet of the first MGSU, the LPC of the first and the second MGSU is continuously swept with the gas mixture of the HPC of the first and second MGSU correspondingly, the pressure in the LPC of the first and second MGSU is decreased by a vacuum-compressor. 
         [0063]    Alternatively for implementation of the above described method, the LPC of the first MGSU is swept with the gas mixture from the HPC outlet of the first MGSU and/or from the HPC outlet of the further MGSUs and/or pressure in the LPC of the first MGSU is decreased herewith the gas mixture from its outlet (the LPC of the first MGSU) is directed to the HPC inlet of the second MGSU and/or the HPC inlet of further MGSUs. 
         [0064]    The above-described method can also be implemented with a plant comprising two MGSUs wherein the HPGM is supplied to the HPC inlet of the first MGSU, the gas mixture from the HPC outlet of the second MGSU is continuously used for sweeping of the LPC of the first and/or second MGSU and/or the pressure in the LPCs is decreased. 
         [0065]    The above-described method can be implemented with a plant comprising two MGSUs wherein the HPGM is supplied to the HPC of the first MGSU, the gas mixture from the outlet of HPC of the first MGSU is continuously used for sweeping of the LPC of the first MGSU and the other portion of the gas mixture is supplied to the HPC inlet of the second MGSU herewith the pressure is decreased in the LPC outlet of the second MGSU and the gas mixture from the LPC outlet of the second MGSU is directed to the HPC inlet of the first MGSU. 
         [0066]    It is preferable when the flow rate of the purified gas mixture that is used for sweeping of said LPC (flow rate of the sweep gas flow) and/or pressure in the LPC is set so that to provide the compliance of the product with the requirements on contents of each of easily permeating components within implementation of the above-described method. 
         [0067]    It is more preferable when said pressure is set so that to provide the desired degree of purification for each easily permeating component. 
         [0068]    It is even more preferable when the flow rate of the purified gas mixture directed to sweeping (flow rate of the sweep gas flow) is selected so that the product yield with contents of each easily permeating component not increasing the desired values shall be increased by at least the flow rate value of the purified gas mixture dedicated to sweeping. 
         [0069]    The above mentioned technical result is also achieved in the process of functioning of a plant for the purification of the high-pressure gas mixture (HPGM) from easily permeating components, comprising membrane gas separating units (MGSUs) with a high-pressure chamber (HPC), a low-pressure chamber (LPC) and a selectively permeable membrane (SPM) therebetween that is equipped with means of the pressure regulation in the HPC and the LPC, with envisaged possibility to maintain this pressure difference of at least in one of said MGSUs, and means for sweeping of the LPC with the purified gas mixture (semi-finished product or product), herewith said means are designed so that to provide the pressure difference between the HPC and the LPC and flow rate of the purified gas mixture that is used for the LPC sweeping so that the amount of each of the indicated easily permeating components in the product does not exceed the desired values. 
         [0070]    In the preferable implementation form the LPC of at least one MGSU is equipped with the means of pressure decrease. 
         [0071]    In one of the particular forms the LPC of at least one MGSU is equipped with methods of pressure decrease and the sweeping with the purified gas mixture is envisaged as a possibility. 
         [0072]    In another particular form of the HPCs implementation the MGSUs are connected between each other in series, herewith the LPC of at least one of tail MGSUs is connected with the HPC inlet of at least one of the head MGSUs for return of the discharge flow to the process head. It is preferable when the LPC of tail MGSUs are connected with the HPC of the head MGSU. 
         [0073]    In another particular form of implementation the HPC inlet of at least one of MGSUs is connected with the LPC outlet of at least another MGSU via a compressor, a refrigerator, a separator and a filter. This allows to return the discharge flow to the gas separation process after its preliminary purification from easily condensed components. 
         [0074]    In the particular form of implementation inlets and outlets of the HPC of at least two MGSUs can be connected between each other in parallel for example for increase of efficiency of the gas separation stage. 
         [0075]    In the preferable form of the implementation a refrigerator, a separator and a filter are installed at the HPC inlet of the first of MGSUs. This allows to preliminarily purify the high-pressure gas mixture from easily condensing components. 
         [0076]    In more preferable form of implementation said separator is equipped with a condensate stabilization unit with outlets for stabilized gas, for discharge gas, for water condensate and for stabilized hydrocarbon condensate. 
         [0077]    In even more preferable form of implementation the outlet of said stabilization unit for stabilizing gas is connected with the HPC inlet of the first MGSU for return of the stabilized gas to the gas separation process head. 
         [0078]    The above-mentioned technical result is also achieved in the process of application of the above-mentioned method for simultaneous stripping of the high-pressure natural and associated gas of at least two easily permeating components. 
         [0079]    It is preferable when the natural gas is stripped from components selected from a group that includes: water vapour, carbon dioxide, carbon monoxide, hydrogen sulphide, merkaptans and helium. 
         [0080]    The above-mentioned technical result is also achieved in the process of application of the above mentioned method for helium recovery from the high-pressure natural gas. 
         [0081]    The principles of the method implementation are visually explained at the example of particular and concrete options described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0082]      FIG. 1  shows a schedule that illustrates dependency of the gas mixture yield purified till the required contents of easily permeating components and the SPM selectivity. 
           [0083]      FIG. 2  shows a schematic drawing of the MGSM (replaceable cartridge) wherein the sweeping of the inside fiber area is provided by portion of the non-permeate. 
           [0084]      FIG. 3  shows a scheme of a plant with connection of MGSUs in series wherein semi-finished product from the first stage of MGSU is directed to the inlet of the second stage MGSU etc. 
           [0085]      FIG. 4  shows a scheme of a two-stage plant with a compressor at the inlet to the MGSU HPC of the first stage wherein the recycling is provided (return to the gas separation process head) of the discharge flow from the MGSU LPC of the second stage. 
           [0086]      FIG. 5  shows a scheme of a single-stage plant for high-pressure gas mixture purification wherein the sweeping and vacuuming of the membrane gas separation unit LPC is provided. 
           [0087]      FIG. 6  shows a scheme of the single-stage plant for high-pressure natural gas purification from helium wherein the sweeping and vacuuming of the membrane gas separating unit LPC is provided. 
           [0088]      FIG. 7  shows a scheme of a two-stage plant for purification of the high-pressure gas mixture with connection of both stages of MGSUs in series between each other. 
           [0089]      FIG. 8  shows a two-stage scheme for the high-pressure gas mixture purification till parameters of its flow rate with connection of both stages MGSUs between each other in series. 
           [0090]      FIG. 9  shows a two-stage plant scheme for the high-pressure gas mixture purification with connection of stages between each other in series wherein each stage comprises separate membrane gas separating units connected between each other in parallel. 
           [0091]      FIG. 10  shows a two-stage plant for high-pressure natural or associated petroleum gas wherein the discharge flow from the first stage is purified at the second stage. 
           [0092]      FIG. 11  shows a two-stage plant scheme for drying of high-pressure natural or associated petroleum gas wherein the discharge flow of the first stage is purified at the second stage. 
           [0093]      FIG. 12  shows the two-stage plant scheme for drying of high-pressure natural or associated petroleum gas wherein the discharge flow from the first stage is purified at the second stage. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0094]    Taking into account the dependency of the SPM selectivity on pressure difference the yield of the product with required contents of water vapours, merkaptans, hydrogen sulphide and hexane is increased due to sweeping of the LPC with the non-permeate only at such pressure difference that provides a selectivity of no lower than the set value (no lower than 20 for hydrogen sulphide as shown at  FIG. 1 ). Herewith the ratio of the sweep gas flow to the permeate flow is chosen based on the required rating of the most hard-to-remove component. In this case the contents of the other components will correspond with the specified standards. 
         [0095]    Membrane gas separating units may be constructed by combining membrane gas-separating modules (MGSM), shown at  FIG. 2 . The raw material is fed under pressure to the MGSM axial manifold  200  and by ports at the manifold end  202  is introduced into the module inter-fiber space  204  (MGSM HPC). The gas flows along the SPM to the outlet  206 . Most part of the SPM is coated with coating non-permeable for gases  208 . Easily permeating components from the HPC through the SPM permeate to the LPC and migrate to the outlet from the LPC (permeate outlet)  210 . It is preferable when flows of the HPC and the LPC are transported along the SPM by counter-flow. A cap  212 , hermetically fastened at a housing  218  is located at the end of the MGSM opposite the permeate outlet. The cap has an opening  214  for installation of replaceable orifices. The purified gas is supplied inside the fibers (MGSM LPC) through the orifice and is used for sweeping of the MGSM LPC  216 . 
         [0096]    Sweeping leads to decrease of concentration of easily permeating components in LPC, thus increasing the gases partial pressure differences between the HPC and the LPC. The purification process of the HPGM from the easily permeating components is improved because the driving force of the separation process is the gases partial pressure differences at the SPM. At the same time the concentration of hard permeating components along the SPM is changed insignificantly, and the partial pressure difference also decreases insignificantly. Decrease of the partial pressure difference deteriorates the purification process of the HPGM from the hard permeating components. 
         [0097]    The value of the permeate flow for every single fiber at the set pressure difference on it depends only on the temperature of the permeating gas mixture and composition of the permeating gas. The value of the sweep gas flow in the first turn depends on the orifice dimensions (orifice diameter and length), pressure drop on it and hardly depends on the temperature and viscosity of the gas flowing through an orifice. Thus the easiest way to change the ratio of the permeate and the sweep gas flow is by changing the dimensions of the orifice. 
         [0098]    The gas mixture at the outlet from the LPC is the discharge flow. The ratio of this flow to the flow of HPGM (at identical product parameters) determines the efficiency of the purification process. The lower the ratio is the more efficient is the operation of the MGSM. From the above-said it follows that it is necessary to optimize the ratio of the permeate and the sweeping flows for provision of the necessary gas purification from easily permeating components. The ratio between the permeate flow and the sweep gas flow is set at the stage of manufacturing of the MGSMs on the basis of results of the purification process numerical modeling and preliminary testing of the MGSM. 
         [0099]    If product with set contents of all easily permeating components can not be obtained in a single-stage process then more complicated purification schemes are used, in particular schemes with connection of MGSUs in series when the semi-finished product of the first stage is directed to the MGSU inlet of the second stage etc. 
         [0100]    The principal scheme of such MGSU connection is shown at  FIG. 3 . 
         [0101]    As shown at  FIG. 3  the raw material (HPGM) by a pipeline  320  is supplied to the MGSU inlet of the first stage  322 , a semi-finished product from the first stage by a pipeline  324  is supplied to the second stage  326  MGSU inlet, whereof a product  328  with set concentrations of components is directed to the consumer. A permeate  334  from the first  330  and from the second stage  332  is the discharge flow. The number of stages may be more than two. These schemes are often applied if the raw material is under pressure. As matter of actual practice each stage in gas separating units may comprise several connected in parallel MGSMs and/or MGSUs. At set pressure and temperature of the HPGM the number of MGSMs and/or MGSUs in the MGSU of each stage is determined by flow rate of the HPGM and the selection ratio i.e. the ratio of the raw material and product flows. 
         [0102]    The scheme with recycling can be used for example as shown at  FIG. 4  if the raw material is compressed before supply to the MGSU. In line with this scheme the raw material  436  is comingled with the permeate of the second MGSU  452 , is compressed by a compressor  438  and the obtained HPGM by a pipeline  440  is supplied to the inlet of the first MGSU  442  whereof the non-permeate by the pipeline  440  is supplied to the inlet of the second MGSU  446 . The product from the second MGSU  448  is directed to the consumer. The permeate from the first MGSU  450  is utilized and the permeate from the second MGSU  452  is supplied to the compressor inlet. For membrane gas-separating units with recycling (i.e. with the permeate return to the gas separation process head) only the permeate of the head MGSU(s) is the discharge flow (i.e. the first MGSU or several head MGSUs including the first one). 
         [0103]    The discharge flow may be collected for additional treatment at oil petroleum or chemical plants or can be used as auxiliary for example for indoor heating or for heating of intermediate gas flows depending on the discharge flow composition. 
         [0104]    In line with the option represented at  FIG. 4  the permeate is returned to the process head from the second stage  452 . In addition to this permeate of the first stage by a pipeline  454  may be fed to the compressor  438  power supply. In this case the number of MGSUs and/or MGSMs of the first stage and operation conditions are selected in such a way that the permeate flow would correspond with the volume gas flow rate necessary for the compressor supply. 
       EXAMPLE 1 
     Purification of High-Pressure Associated Gas From the Water Vapours at a Single-Stage Plant 
       [0105]    The raw material (the HPGM with a pressure of 60 bar with content of water 0.07% mole, methane 93.6% mole, CO2 2.9 mole, other: hydrocarbons C2-C5) is supplied by the inlet nozzle inside the plant comprising an MGSU with MGSMs connected in parallel on the basis of hollow fibers (structure of MGSM is shown at  FIG. 2  and described above). The raw material is supplied to the MGSM HPC (inter-fiber space). Portion of the gas (permeate) from the HPC permeates through walls to the LPC (internal fibers channels) when passing along the fibers. The product obtained at the outlet from the HPC (non-permeate) is divided into two parts. The main portion is deviated by the corresponding nozzle under a pressure of 59 bar. The less portion (sweep gas flow) is supplied to the chamber above the open part of fibers opposite an outlet nozzle through the orifice in the internal cap, whereof it is directed to the internal fiber channels and is commingled with the permeate that permeated the fiber wall after that the obtained mixture of the permeate and the non-permeate is withdrawn from the LPC by the nozzle under a pressure of 2.0 bar. 
         [0106]    The pressures ratio in chambers was estimated as P(high)/P(low)=30, the specific permeabilities ratio (selectivity) on water and methane P/1(H 2 O)/P/1(CH 4 )=280, thus P/1(H 2 O)/P/1(CH 4 )&gt;P(high)/P(low), the permeate percent in the raw material flow is 4.6%; the percent of product used for sweeping 2.9% from the raw material; contents of water in the residual flow 0.0025% mole, methane 94.6% mole, CO 2  2.4% mole. The contents of water in residual flow without sweeping is 0.03% mole, methane 94.6% mole, CO 2  2.4% mole. 
       EXAMPLE 2 
     High-Pressure Associated Gas Purification From Hydrogen Sulphide at a Single-Stage Plant 
       [0107]    The raw material (HPGM with a pressure of 20 bar and hydrogen sulphide contents of 0.02% mole, methane 88.9% mole, CO 2  3.3% mole, nitrogen 0.2% mole, other: hydrocarbons C 2 -C 5 ) was supplied by an inlet nozzle inside the plant comprising MGSU with MGSMs connected in parallel on the basis of hollow fibers (MGSM structure is shown at  FIG. 2  and described above). Passing along fibers, the high-pressure gas mixture components from a HPC (inter-fiber space) permeate through fiber walls to a LPC (internal fibers channels), herewith the mixture is stripped from easily permeating components, and the product obtained in the result (non-permeate) is divided into two parts. The main portion of the non-permeate is withdrawn by a corresponding nozzle under a pressure of 19 bar. Less portion of the non-permeate (sweep gas flow) through an orifice in the internal cap is supplied to the chamber above the open part of the fibers opposite the outlet nozzle whereof the non-permeate is supplied to the channels inside the fibers and is commingled with the permeate permeated through the fiber wall, thereafter the obtained mixture is deviated by a nozzle under a pressure of 1.2 bar. 
         [0108]    The ratio of pressures in chambers was estimated as P(high)/P(low)=16, the specific permeability ratio (selectivity) per hydrogen sulphide and per methane P/1(H 2   8 )/P/1(CH 4 )=40, herewith P/1(H 2 S)/P/1(CH 4 )&gt;P(high)/P(low); percent of the permeate in the raw material flow is 8.4%, percent of product used for sweeping is 4.5% of the raw material flow, hydrogen sulphide content in product is 0.003% mole, methane—91.1% mole, CO 2 —2.2% mole. Percent of hydrogen sulphide in product without sweeping (MGSMs with blind orifices were used) was estimated as 0.008% mole, methane —1.1% mole, CO 2 —2.2% 
       EXAMPLE 3 
     Purification Of High-Pressure Associated Gas From Hexane at a Single-Stage Plant 
       [0109]    The raw material (HPGM under a pressure of 14 bar with contents of hexane 0.95% mole, methane 70.5% mole, water 0.55% mole) by an inlet nozzle is supplied into the plant comprising an MGSU with MGSMs connected in parallel on the basis of hollow fibers (MGSM structure is shown at  FIG. 2  and described above). The raw material is introduced into a MGSU HPC (inter-fiber space). When passing along fibers the components of the gas mixture from the HPC permeate the fibers wall in a LPC (internal channels of fibers). The product (non-permeate) is divided into two parts. The main portion is withdrawn by a corresponding nozzle under a pressure of 14 bar. The less portion is supplied to the chamber above the open part of fibers through an orifice in the internal cap, opposite the outlet nozzle whereof it is directed to sweeping of the internal fibers channels where it is commingled with the permeate that permeated through the fiber wall. The obtained gas mixture is deviated by a nozzle under a pressure of 1.2 bar. 
         [0110]    The ratio of pressures in chambers of the MGSM was P(high)/P(low)=12.5, the specific permeabilities ratio (selectivity) for hexane and methane P/1 (C 6 H 14 )/P/1 (CH 4 )=25, thus P/1(C 6 H 14 )/P/1(CH 4 )&gt;P(high)/P(low); portion of the permeate is estimated as 11.5% of the raw material flow, the percent of gas passing through an orifice is 4.5% of the raw material flow; hexane content in product is estimated as 0.15% mole, methane 75.5% mole, water 0.08% mole. Without sweeping (MGSM with blind orifices was used) the hexane content in product is estimated as 0.27% mole, methane 75.5% mole, water 0.24% mole. 
       EXAMPLE 4 
     Single-Stage Plant With Sweeping and Vacuuming of the Low-Pressure Chamber of the Membrane Gas Separating Unit for the High-Pressure Gas Mixture Purification 
       [0111]    As shown at  FIG. 5  the plant comprises an MGSU  556  with a HPC  558  and a LPC  560 , with a SPM  562  therebetween. The raw material (HPGM)  564  is supplied to the HPC  558  of the MGSU  556 , the product (non-permeate)  566  is obtained from the HPC outlet, and the discharge flow  568  is taken away from the LPC outlet (mixture of the permeate and the sweep gas), portion of product  570  (sweep gas) is used for sweeping of the LPC  560  after throttling in an orifice  572 , and pressure in the LPC  560  is decreased by a vacuum-compressor  574 , thus providing a possibility to change the pressure ratio of gas flows in the HPC  558  and the LPC  560 . 
         [0112]    If necessary the raw material is separated in a separator  576  and/or filtrated at a filter  578  for condensate and mechanical mixtures removal and also heated in a heat-exchanger  580  before the raw material is supplied to the MGSU  556 . 
         [0113]    The flow rate of sweep gas  570  and pressure difference between the HPC  558  and the LPC  560  are selected from the conditions of maximum product yield and minimum specific energy consumption for the purification process. Thus the increase of the separation efficiency of the LPC with the minimum energy consumption is provided due to sweeping. 
         [0114]    The contents of the non-desired impurities in product may be decreased in two or more times. 
       EXAMPLE 5 
     Purification Of Natural Gas From Helium at Plant Per Example 4 
       [0115]    The raw material namely crude natural gas under a pressure till 10 MPa, containing 0.6% mole helium, is supplied to the MGSU. Before supply of the raw material to the MGSU the raw material is separated and filtrated for removal of condensate and mechanical impurities and then is heated till a temperature of 50° C. The product with contents of helium of 0.1% mole from the MGSU under a pressure of 9.8 MPa is directed to the consumer. Approximately 5% of product (the non-permeate), is directed to the MGSU for sweeping of the LPC. The gas mixture at the outlet of the LPC (discharge flow) with contents of helium 4.5÷5% mole has a pressure of 0.05 MPa, provided by the vacuum compressor that then compresses the gas mixture up to a pressure of 15 MPa. The discharge flow is directed either to utilization to storage, or is downhole injected, or is re-processed. The capacity of vacuum compressor and throttling parameters of the sweep gas are chosen on condition of maintaining of optimum pressure difference in the MGSU chambers. 
       EXAMPLE 6 
     Purification of Natural Gas From Hydrogen Sulphide at the Plant Per Example 4 
       [0116]    The raw material namely natural gas with a pressure of 2.5 MPa and a temperature of 25÷30° C., with 150 mg/m 3  of hydrogen sulphide, is supplied to the MGSU. Preliminarily the raw material is purified from condensate and mechanical impurities. A coalescing-type filter is to be used. The product with the content of hydrogen sulphide no more than 20 mg/m 3  under a pressure of 2.2 MPa is directed to the consumer. The portion of product, approximately 5%, is directed to the MGSU for sweeping of the LPC. The discharge flow collected from the LPC outlet, contains hydrogen sulphide up to 1500 mg/m3 and has a pressure of 0.1 MPa, provided by the vacuum compressor and then the gas mixture flow is compressed till a pressure of 0.2 MPa. 
         [0117]    The capacity of the vacuum compressor and sweep gas throttling parameters are chosen on the basis of maintaining the optimum pressure difference in the MGSU chambers. 
       EXAMPLE 7 
     Purification of Natural Gas From the Water Vapours at the Plant Per Example 4 
       [0118]    The raw material namely natural gas under a pressure of 2.8 MPa and a temperature of 45° C. with 100% relative humidity (per water) is supplied to the MGSU. The raw material is separated and filtrated for removal of condensate and mechanical impurities before supply of the raw material to the MGSU. The product is supplied to the consumer with contents of water no higher than 0.012% mole (that corresponds with the water dew point temperature of minus 10° C. at the above-indicated pressure). The portion of product (sweep gas) approximately 6% is directed to the MGSU for sweeping of the LPC. The discharge flow contains up to 3.0% mole of water. 
         [0119]    The vacuum compressor provides for pressure decrease in the LPC till 0.05 MPa and supply of the discharge flow for the further reprocessing under a pressure of 0.15 MPa. The efficiency of the vacuum-compressor and throttling parameters of the sweep gas are selected on condition of maintaining of the optimum pressure difference in the MGSU chambers. 
       EXAMPLE 8 
     Purification of Natural Gas From Hydrocarbons Containing 4 and More Carbon Atoms at the Plant Per Example 4   
       [0120]    The raw material namely associated petroleum gas under a pressure of 1.6 MPa with contents of hydrocarbons C 4+ 8.0% mole is cooled till temperature of 20° C. in the refrigerator. Then before supply to the MGSU the associated gas is consequently purified from condensate and mechanical impurities in the separator and the coalescing filter. The purified gas is supplied to the inlet of the HPC of the MGSU, and product with contents of hydrocarbons C 4+  with no more than 2.0% mole is directed to the consumer. Portion of product (sweep gas) is directed to the MGSU for sweeping of the LPC. The discharge flow contains 15% mole of C 4+  hydrocarbons. 
         [0121]    The vacuum compressor maintains pressure in the LPC up to 0.04 MPa and supplies the discharge flow for the further re-processing under a pressure of 0.12 MPa. The capacity of the vacuum compressor and natural gas throttling parameters are chosen on condition of maintaining optimum pressure difference in the MGSU chambers. 
       EXAMPLE 9 
     Purification of the High-Pressure Natural Gas From Helium at the Single-Stage Plant With Sweeping and Vacuuming of Low-Pressure Chamber of the Gas Separating Unit 
       [0122]    As shown at  FIG. 6  the plant for purification of natural gas from helium comprises a MGSU  682  with a HPC  684  and a LPC  686 , separated by a SPM  688 . The HPC  684  from one side is connected with a pipeline  690  and with a pipeline  692  from the opposite side. The LPC  686  is connected with a sweeping channel  694 , interconnected with the pipeline  692  and a pipeline  696 , herewith a throttling element  698  is installed in the sweeping channel  694 . A vacuum-compressor  6100  is installed at the pipeline  696  and provides for the possibility of pressure decrease in the LPC  686  and supply of the gas mixture from the LPC  686  to utilization in the storage area or either for downhole injection or for re-processing. The plant can be equipped with a separator  6102  and a filter  6104  installed in series at the supply pipeline  690  for purification of natural gas from condensate and mechanical impurities. A compressor  6106  and a refrigerator  6108  can be installed in series upstream the separator  6102  at the supply pipeline  690 . Besides it may be equipped with a heater  6110 , installed at the supply pipeline  690  directly upstream the MGSU  684 . The plant may be equipped with a condensate stabilization unit  6112 , connected by its inlet with the condensate outlet of the separator  6102  and with three outlets , the first of which is connected to a pipeline  6114  of gas discharge to utilization or flaring, the second one is connected to a pipeline  6116  for the hydrocarbon withdrawal to the further reprocessing or for downhole injection and the third one is directed to a pipeline  6118  for water condensate removal. 
         [0123]    The raw material i.e. high-pressure natural gas with helium contents of 0.2÷1.0% mole, is supplied to the HPC  684  of the MGSU  684  by the pipeline  690 . Preliminarily the raw material is purified from condensate and mechanical impurities in the separator  6102  and the filter  6104 , the latter can be of a coalescing type. The raw material temperature before supply to the MGSU  682  may be increased in the heater  6110 . In case of the raw material low-pressure the raw material is preliminarily compressed in the compressor  6106  and then cooled in the refrigerator  6108 . Preliminarily purified raw material is supplied to the HPC  684  of the MGSU  682  whereof a product with helium contents of 0.1% mole is directed to the consumer by a pipeline  692 . Portion of product (sweep gas) from the pipeline  692  per a channel  694  with a throttling element  698  is directed to the LPC  686 . The discharge flow with contents of helium 1.5÷5.0% mole is deviated from the LPC  686  by a pipeline  696  by the vacuum-compressor  6100  ensuring pressure decrease in the LPC  686  and supply of the discharge flow to utilization, to storage, for the downhole injection or for the further reprocessing. The capacity of the vacuum compressor  6100 , the throttling element  698  parameters in the channel  694  and the gas mixture pressure in the pipeline  696  are selected on condition of maximum for the applicable MGSU  682  rate of the purified gas recovery, and correspondingly minimum energy consumption of the purification process. 
         [0124]    The condensate from the separator  6102  is directed either directly to utilization for example by downhole injection for maintaining of the formation pressure or is supplied to the condensate stabilization unit  6112  if available at the plant. In the latter case three flows derive from the condensate stabilization unit  6112  namely gas is discharged for utilization or flaring by the pipeline  6114 , the hydrocarbon condensate is deviated for the further reprocessing or for downhole injection by the pipeline  6116  and the water condensate is deviated by the pipeline  6118 . 
         [0125]    The vacuum compressor  6100  and the channel  694  with the throttling element  698  provide for the stable and efficient operation of the MGSU  682  that allows to increase the rate of helium recovery and decrease the energy consumption for the purification process. Stable operation of the MGSU  682  is also provided by means for the preliminary purification of the natural gas, i.e. the separator  6102 , the filter  6104  and the heater  61   10 . Besides the plant design provides for the natural gas purification wastes utilization. 
       EXAMPLE 10 
     The High-Pressure Gas Mixture Purification at a Two-Stage Plant With Stages Connected in Series 
       [0126]    HPGM by a pipeline  7120  is supplied to a HPC  7124  of the first MGSU  7122 ; the semi-finished product (non-permeate) from the HPC  7124  of the first MGSU  7122  is supplied to a HPC  7128  of the second MGSU  7126  as shown at  FIG. 7 ; the permeate  7152  from a LPC  7130  of the first MGSU  7122  is utilized, product  7132  (non-permeate) is collected at the outlet of the HPC of the second MGSU  7126 , the permeate  7154  from a LPC  7134  of the second MGSU  7126  is supplied to a raw material pipeline  7136 , the portion of the semi-finished product is deviated (sweep gas) from the outlet of the first MGSU  7122  and through a throttling element  7138  is deviated to sweeping of the LPC  7130  of the first MGSU  7122 , herewith the pressure is decreased in the LPC  7134  of the second MGSU  7126  by a vacuum compressor  7140 . 
         [0127]    The capacity of the vacuum compressor  7140  is selected so that to provide for the maximum pressure difference at a SPM. The amount of the sweep gas is chosen on condition of the maximum gas separation efficiency. 
         [0128]    The discharge flow from the LPC  7134  of the second MGSU is sucked and compressed by the vacuum compressor  7140 . Then for purification of the HPGM from condensate and mechanical impurities the HPGM is cooled  7144 , separated  7146  and is filtrated  7148  before the direct supply of the HPGM to the HPC  7124  of the first MGSU  7122 . The condensate flow from a separator  7146  is directed to a condensate stabilization unit  7150  with four outgoing flows the first whereof as the gas flow of stabilization  7156  is supplied to the raw material flow for reprocessing, the second discharge gas flow  7158  is directed for utilization, the third stable hydrocarbon condensate  7160  is directed to the further reprocessing or downhole injected, the fourth water condensate flow  7162  is directed to the downhole injection for maintaining of the formation pressure or is directed to the utilization. 
         [0129]    The efficient separation of the gas mixture and increase of the efficiency of the method in the whole is provided by sweeping of the LPC  7130  of the first MGSU  7122  and maintaining of the decreased pressure in the LPC  7134  of the second MGSU  7126 . 
       EXAMPLE 11 
     The High-Pressure Gas Mixture Purification at the Two-Stage Plant With Stages Connected in Series Till Parameters of its Consumption 
       [0130]    As shown at  FIG. 8  the plant of the multi-stage HPGM purification comprises a compressor  8164  and two MGSUs  8166  and  8168  connected in series with high-and low-pressure chambers  8170  and  8172 , separated by a SPM  8174 . The inlet of the compressor  8164  is connected with a pipeline for the raw material supply  8176 , and outlet is connected by a pipeline  8178  of the HPGM supply with the inlet to a HPC MGSU  8166 , the MGSU HPC outlet  8166  is connected by a pipeline  8180  with the inlet of a HPC MGSU  8168 . The outlet of the HPC of the MGSU  8168  is connected with a pipeline  8182  of the purified gas mixture supply to the consumer. A LPC of the MGSU  8166  is connected with a pipeline  8184 , and a LPC of the MGSU  8168  is connected by a pipeline  8186  with the pipeline  8176 . The plant is equipped with vacuum compressors  8188  and  8190 , herewith the vacuum compressor  8188  is installed at the pipeline  8184 , and the vacuum compressor  8190  is installed at the pipeline  8186 . The MGSUs  8166  and  8168  are equipped with channels  8192  and  8194  for sweeping of the LPCs  8172 . The channels  8192  and  8194  are designed so that to provide a possibility to supply portion of the purified gas mixture from the HPCs  8170  of the MGSUs to the LPCs  8172 . The channels  8192  and  8194  are equipped with throttling elements  8196 , for example, an orifice for withdrawal portion of the product or semi-finished product from the HPC  8170  of the MGSU. 
         [0131]    The channels  8192  and  8194  may be implemented in the structure of the corresponding MGSU itself. The first and second sweeping channels  8192  and  8194  can be arranged by pipelines herewith the pipeline of the first sweeping channel  8192  is connected with the deviating non-permeate flow of the pipeline  8180  from the first MGSU  8166  at one end and to the low-pressure chamber  8172  at another end and pipeline of the second sweeping channel  8194  is connected to the pipeline  8182  of the purified gas mixture supply to the consumer by one end and to the low-pressure chamber  8172  of the second MGSU  8168  by another end. 
         [0132]    The plant can be equipped with a refrigerator  8198 , a separator  8200  and a filter  8202  installed at a pipeline  8178  in series for purification of natural gas from condensate and mechanical impurities. 
         [0133]    In addition, the plant may be equipped with a condensate stabilization unit  8204  with one inlet  8206  and four outlets  8208 ,  8210 ,  8212  and  8214 . The inlet  8206  of the condensate stabilization unit  8204  is connected with a pipeline  8216  of condensate removal from the separator  8200 . The first outlet  8208  of the condensate stabilization unit  8204  is connected by a pipeline  8218  of the gas stabilization flow supply with a pipeline  8176  of the raw material supply for reprocessing. The second outlet  8210  is connected with a pipeline  8220  of the gas mixture flow discharge to utilization. The third outlet  8212  is connected with a pipeline  8222  of the stable hydrocarbon condensate takeoff to further reprocessing or to downhole injection, and the fourth outlet  8214  is connected with a pipeline  8224  of water condensate takeoff for downhole injection in order to maintain formation pressure or to utilization. 
         [0134]    By the pipeline  8176  of the raw material supply, for example, feed natural or associated gas, the gas mixture under a pressure, for example, 0.12÷0.15 MPa is supplied to the compressor inlet  8164 . The HPGM under a pressure of ,for example, 2.5 MPa from the compressor  8164  outlet is supplied by the pipeline  8178  to the LPC  8170  of the first MGSU  8166 . The non-permeate from the HPC of the first MGSU  8166  by the pipeline  8180  is directed to the LPC  8170  of the second MGSU  8168 . The non-permeate with reduced impurities contents, for example, heavy hydrocarbons, water and carbon dioxide, from the second MGSU  8168  is directed to the pipeline  8182  for supply to the consumer. From the LPC  8172  of the first MGSU  8166  the permeate under the membrane  8174  with increased contents of impurities, for example, heavy hydrocarbons, water and carbon dioxide, is directed to utilization. From the LPC  8172  of the second MGSU  8168  the permeate is directed by a pipeline  8186  to the pipeline  8176  of the raw material supply. Certain portion of the non-permeate is continuously withdrawn from the high-pressure chambers  8170  to the LPC  8172  of the relevant MGSU for sweeping, herewith the pressure is decreased in the LPC  8172  of each MGSU  8166  and  8168  by the vacuum compressors  8188  and  8190  in each MGSU  8166  and  8168  through the sweeping channels  8192  and  8194  with the throttling elements  8196 . The sweeping of chambers  8172  and decrease of pressure therein leads to increase of the gas separation efficiency. The capacity of the vacuum compressors  8088  and  8190  is chosen on condition of provision of the maximum value of pressure ratio at the gas separating membrane  8174  of the membrane modules  8166  and  8168 . The amount of gas to sweeping is chosen on condition of provision of the maximum gas separation efficiency in the MGSUs  8166  and  8168 . In some cases, a refrigerator  8198 , a separator  8200  and a filter  8202  are installed in series upstream the direct supply of the high-pressure gas mixture to the high-pressure chamber  8170  of the first MGSU  8166  at the high-pressure pipeline  8178 , that allows to remove condensate and mechanical impurities from the gas mixture. The condensate flow from the separator  8200  by the pipeline  8216  of condensate take-off is directed to the inlet  8216  of the condensate stabilization unit  8204 . From the first outlet  8208  of the condensate stabilization unit  8204  at the pipeline  8218  the flow of stabilized gas is fed to the pipeline  8176  of the raw material supply, where the flows are commingled. The gas mixture flow is discharged to utilization by the pipeline  8220  from the second outlet  8210  of the condensate stabilization unit  8204 . The stabilized hydrocarbon condensate is deviated for the further reprocessing or for downhole injection from the third outlet  8212  by the pipeline  8222 , and the water condensate that may be used for downhole injection to maintain formation pressure or to the utilization is deviated from the fourth outlet  8214  by the pipeline  8224 . 
         [0135]    Thus the efficient separation of the gas mixture is provided and the efficiency of the plant in general is increased by sweeping of the LPC and maintaining decreased pressure therein. 
       EXAMPLE 12 
     The High-Pressure Gas Mixture Purification at a Two-Stage Plant With Stages Connected in Series, Each of the Stages Comprising Membrane Gas Separating Units Connected Between Each Other in Parallel 
       [0136]    As shown at  FIG. 9  a multi-stage gas mixture purification plant comprises a compressor  9226 , the first MGSU  9228  and the second MGSU  9230  with HPCs and LPCs  9232  and  9234 , separated by SPMs  9236 . The compressor  9226  inlet is connected with a pipeline  9238  of raw material supply, and outlet is connected with a pipeline  9240  with a HPC  9232  inlet of the first MGSU  9228 , the outlet whereof is connected by a pipeline  9242  with a HPC  9232  inlet of the second MGSU  9230 . The outlet of the HPC  9232  of the second MGSU  9230  is connected with a pipeline  9244  for supply of the purified gas mixture to the consumer. The LPC  9234  of the first MGSU  9228  is connected with a pipeline  9246  for the permeate removal for the further reprocessing or utilization, and the LPC  9234  of the second MGSU  9230  is connected by a pipeline  9248  with the raw material supply pipeline  9238 . The plant is equipped with additional membrane units  9250  and  9252  with high-and low-pressure chambers  9254  and  9256 , separated by a selectively permeable membrane  9258 , herewith units  9250  are connected to the first membrane unit  9228  in parallel, and units  9252  are connected to the second membrane unit  9230  in parallel, and to two additional vacuum compressors  9260  and  9262 , herewith the first additional vacuum compressor  9260  is installed in the pipeline  9246 , the second vacuum compressor  9262  is installed in the pipeline  9248 . Each unit  9228 ,  9230 ,  9250  and  9252  is equipped with channels  9264  that are provided for a possibility of the continuous supply of the portion of the permeate for sweeping from the HPCs  9232  and  9254  to the LPCs  9232  and  9256  correspondingly. 
         [0137]    There can be more additional membrane units  9250  connected to the first MGSU  9228  than additional MGSUs  9252  connected to the second MGSU  9230 . The number of MGSUs installed in parallel is selected on condition of provision of the most optimum gas separation process at each stage and most efficient operation of the whole plant in general. 
         [0138]    Each channel  9264  for sweeping of LPCs  9234  and  9256  may have a throttling element  9266 , for example, an orifice, for provision of collection of the exact certain portion of the non-permeate from the HPCs  9232  and  9254 . The channels  9264  for sweeping can be envisaged in the structure itself of the relevant MGSU or by pipelines arrangement. 
         [0139]    The plant can be equipped with a refrigerator  9268 , a separator  9270  and a filter  9272  in a pipeline  9240  installed in series for purification of natural gas from condensate and mechanical particles. 
         [0140]    In addition the plant can be equipped with a condensate stabilization unit  9274 , with one inlet  9276  and four outlets  9278 ,  9280 ,  9282  and  9284 . The inlet  9276  of the condensate stabilization unit  9274  is connected with a pipeline  9286  of the condensate removal from the separator  9270 . The first outlet  9278  of the condensate stabilization unit  9274  is connected with a pipeline  9288  of feed gas flow stabilization with the raw material supply pipeline  9238  for return to the purification. The second outlet  9280  is connected with a pipeline  9290  of the gas mixture flow discharge to utilization. The third outlet  9282  is connected with a pipeline  9292  of the stable hydrocarbon condensate removal for the further reprocessing or for downhole injection, and the fourth outlet  9284  is connected with a pipeline  9294  for the water condensate removal for downhole injection to maintain the formation pressure or to utilization. 
         [0141]    Raw material (for example, feed natural or associated gas), is supplied to the compressor inlet  9226  by the pipeline  9238 . Downstream outlet from the compressor  9226  the gas mixture goes by a pipeline  9240  via the refrigerator  9268 , the separator  9270 , the filter  9272  installed in series and is introduced into the high-pressure chambers  9232  and  9254  of the first MGSU  9228  and additional MGSUs  9250  connected to it in parallel. The non-permeate above a membrane  9236  of the first MGSU  9228  through the membrane  9256  of additional MGSUs  9250  is directed to the HPCs  9232  and  9254  of the second MGSU  9230  and the additional MGSU  9252  by the pipeline  9242 . The non-permeate from the HPCs  9232  and  9254  of the second MGSU  9230  and the additional MGSU  9252  with decreased content of impurities, for example, heavy hydrocarbons, water and carbon dioxide, is directed to the pipeline  9244  for supply to the consumer. The permeate with increased contents of impurities, for example, heavy hydrocarbons, water and carbon dioxide from the LPCs  9234  and  9256  of the first MGSU  9228  and the additional MGSUs  9250  under the membrane  9236  and  9258  is directed to utilization by the pipeline  9246 . The permeate from the LPCs  9234  and  9256  of the second MGSU  9230  and the additional MGSUs  9252  is directed to the raw material supply pipeline  9238  by the pipeline  9248 . Certain portion of the permeate is continuously removed from each of MGSUs  9228  and  9230  and in each of the additional MGSUs  9250  and  9252  by sweeping channels  9264  with the throttling elements from the HPCs  9232  and  9254  to the LPCs  9234  and  9256  of the relevant MGSU for sweeping, herewith the pressure is decreased in the LPCs  9234  and  9256  of the MGSUs  9228  and  9230  and additional MGSUs  9250  and  9252  by the vacuum compressors  9260  and  9262 , installed in the pipeline  9246  and  9248 , correspondingly. Sweeping of the LPCs  9234  and  9256  and decrease of pressure in them lead to increase of the gas separation efficiency. The capacity of the vacuum compressors  9260  and  9262  is chosen on condition of provision of maximum ratio of pressures at the membranes  9236  and  9258  of the MGSUs  9228  and  9230  and the additional MGSUs  9250  and  9252 . The amount of sweep gas is chosen on the basis of provision of the maximum gas separation efficiency in the MGSUs  9228  and  9230  and the additional MGSUs  9250  and  9252 . 
         [0142]    The condensate flow from the separator  9270  by a pipeline  9286  of condensate removal is directed to the inlet  9276  of the condensate stabilization unit  9274 , providing a possibility of condensate separation to the components. From the first outlet  9278  of the condensate stabilization unit  9274  by the pipeline  9288  the stabilized gas flow is deviated to the pipeline  9238  of the raw material supply. The gas mixture flow from the second outlet  9280  of the condensate stabilization unit  9274  by the pipeline  9290  is discharged to utilization. Stable hydrocarbon condensate from the third outlet  9282  is deviated to the further purification by the pipeline  9292 , or is downhole injected, and the fourth outlet  9284  is used for the water condensate that may be used for downhole injection to maintain the formation pressure or for utilization, the water condensate is deviated by the pipeline  9294 . 
         [0143]    Herewith the provision of the plant with the additional membrane modules  9250  and  9252  and carrying out of sweeping in all MGSUs  9228 ,  9230 ,  9250  and  9252  of the LPCs  9234  and  9256  and simultaneous maintaining of the decreased pressure in them provide for the capacity increase and efficient separation of the gas mixture. 
       EXAMPLE 13 
     Purification of Natural and Associated High-Pressure Petroleum Gas at a Single-Stage Plant Wherein the Permeate Obtained From the First Stage is Purified at the Second Stage 
       [0144]    As shown at  FIG. 10  the plant of the fuel gas purification from natural or associated petroleum gas comprises a compressor  10296  and a MGSU  10298  with high-and low-pressure chambers  10300  and  10302 , separated by a SPM  10304 , the compressor inlet  10296  is connected with a raw material supply pipeline  10306 , and outlet is connected with a pipeline  10308  (via a separator  10310  and a filter  10312 ) with the HPC inlet  10300  of the MGSU  10298 , outlet whereof is connected with a pipeline  10314  of the purified fuel gas to consumer, herewith the LPC  10302  of the MGSU  10298  is connected with a pipeline  10316 , and the plant is equipped with a channel  10318  that provides for continuous supply of the portion of the non-permeate from the HPC  10300  of the MGSU  10298  to the LPC  10302  for sweeping and additionally with a compressor  10320 , a separator  10322 , a filter  10324  and a MGSU  10326  with high- and low-pressure chambers  10328  and  10330 , separated by a membrane  10332 , herewith inlet of the additional compressor  10320  is connected by a pipeline  10316 , and outlet is connected by an additional high-pressure pipeline  10334  via the additional separator  10322  and a filter  10324  with the HPC  10328  inlet of the additional MGSU  10326 . The HPC  10328  outlet of the additional MGSU  10326  is connected by a pipeline  10336  with the high-pressure gas mixture pipeline  10308  at the section between the filter  10312  and the MGSU  10298 , and the LPC  10330  of the additional MGSU  10326  is connected to a pipeline  10338 . The channel  10318  for sweeping may be equipped with a throttling element  10340 , for example, an orifice. The channel  10318  for sweeping may be provided in the MGSU  10298  itself or by pipelines arrangement. The plant may be equipped with two refrigerators  10342  and  10344 , the first refrigerator  10342  is installed in the high-pressure pipeline  10308  between the compressor  10296  and the separator  10310 , and the second refrigerator  10344  is installed in the additional high-pressure pipeline  10334  between the additional compressor  10320  and the additional separator  10322 . The plant can be also equipped with a condensate stabilization unit  10346  with two inlets  10348  and  10350  and four outlets  10352 ,  10354 ,  10356  and  10358 , herewith the first inlet  10348  of the condensate stabilization unit  10346  is connected with condensate discharge pipeline  10360  from the separator  10310 , and the second inlet  10350  is connected with a condensate takeoff pipeline  10362  from an additional separator  10332 , herewith the first outlet  10352  of the condensate stabilization unit  10346  is interconnected with a pipeline  10364  and then connected with the feed gas stabilization supply pipeline  10316  for the re-processing, the second outlet  10354  is connected with pipeline  10366  of the gas mixture flow discharge to utilization, the third outlet  10356  is connected with a stabilized hydrocarbon condensate removal pipeline  10368  to further re-processing or to downhole injection, the fourth outlet  10358  is connected with a pipeline  10370  of the water condensate removal for downhole injection to maintain the formation pressure or to utilization. 
         [0145]    The raw material (natural or associated petroleum gas) by the pipeline  10306  is supplied to the inlet of compressor  10296 . From the compressor  10296  outlet the compressed gas by the pipeline  10308  via the refrigerator  10342 , the separator  10310 , the filter  10312  is directed to the LPC  10300  of the MGSU  10298 . The gas mixture is preliminarily purified in the separator  10310  and the filter  10312  from the water and heavy hydrocarbons condensate and mechanical impurities. The gas mixture flow to the MGSU  10298  is divided into two flows: the non-permeate flow above the membrane  10304  and the permeate flow under the membrane  10304 . The non-permeate flow above the membrane  10304  with low contents of water vapours and heavy hydrocarbons is directed by the pipeline  10314  to the consumer, herewith portion of the non-permeate is continuously deviated by the channel  10318  to the LPC  10302  for sweeping that increases gas separation efficiency in the MGSU  10298 . The throttling element  10340 , for example, an orifice provides for the removal of the certain non-permeate portion from the HPC  10300 . From the LPC  10302  the gas mixture with increased contents of water vapours and heavy hydrocarbons by the pipeline  10316  is directed to the additional compressor  10320  inlet, that from one side compresses the gas mixture and from the other side decreases pressure in the LPC  10302  of the MGSU  10298 , thus providing the necessary ratio of pressures at the membrane  10304 , close to optimum value for efficient gas separation. The gas mixture from the additional compressor  10320  via the additional refrigerator  10344 , the separator  10322  and the filter  10324  is supplied by the additional high-pressure pipeline  10334  to the LPC  10328  of the additional MGSU  10326 , wherein the gas mixture is divided into two flows: the non-permeate flow above the membrane  10332  and the permeate flow under the membrane  10332 . The non-permeate flow enriched with methane is deviated by the pipeline  10336  to the pipeline  10308  at its section between the filter  10312  and the MGSU  10298 , and the permeate flow with large content of water vapours and low content of heavy hydrocarbons is deviated to utilization by the pipeline  10338 . 
         [0146]    If the plant is equipped with the gas stabilization unit  10346  from the separator  10310  and the additional separator  10322  the condensate is supplied by pipelines  10360  and  10362  to inlets  10348  and  10350 . In the condensate stabilization unit  10346  the condensate is divided into four flows. From the first outlet  10352  of the condensate stabilization unit  10346  the stabilized gas flow is transported by the pipeline  10364  to the pipeline  10316 . The flow of the gas mixture from the second outlet  10354  of the condensate stabilization unit  10346  by the pipeline  10366  is directed to utilization. The third outlet  10356  is dedicated to deviation of the stable hydrocarbon condensate to further re-processing or for downhole injection by the pipeline  10368 , and the fourth outlet  10358  is dedicated to deviation of the water condensate that can be used for downhole injection to maintain the formation pressure or to the utilization by a pipeline  10370 . 
         [0147]    Sweeping of the LPC with the purified gas mixture allows to increase the gas separation efficiency and to decrease the purified gas loses. 
       EXAMPLE 14 
     Drying of Natural or Associated High-Pressure Petroleum Gas at a Two-Stage Plant Wherein the Discharge Flow From the First Stage is Purified at the Second Stage 
       [0148]    The plant for drying of natural gas comprises two MGSUs  1   1372  and  1   1374  with high- and low-pressure chambers  1   1376  and  1   1378 , separated by a selectively permeable membrane  11380 , a compressor  11382 , a refrigerator  11384  and a separator  11386  as shown at  FIG. 11 . The inlet of the high-pressure chamber  11376  of the first MGSU  11372  is connected with a pipeline for raw material supply  11388 , and outlet is connected with a pipeline  11390 . The LPC  11378  inlet of the first MGSU  11372  is connected with the first channel  11392  of sweeping, and outlet is connected with the first pipeline  11394 , connected to the compressor  11382  inlet, an outlet whereof is connected by a pressure pipeline  11396  (where a refrigerator  11384  and a separator  11386  are connected in series), with the HPC  11376  inlet of the second MGSU  11374 , the outlet whereof is connected with a pipeline  11398 . The low-pressure chamber  11378  of the second MGSU  11374  is connected by a pipeline  11400  with a pipeline  11394  and the second sweeping channel  11402 , providing for the continuous supply of portion of the non-permeate from the second MGSU  11374  to the LPC  11378 . The first channel  11392  for sweeping is designed with a possibility of provision of continuous supply of portion of the non-permeate from the first MGSU  11372  to the LPC  11378 . The pipeline  11398  from the second MGSU  11374  is connected to the outlet pipeline  11390 . 
         [0149]    The channels  11392  and  11402  for sweeping have a throttling element  11404 , for example an orifice. 
         [0150]    The plant can be equipped with an additional separator  11406  and two filters  11408  and  11410 , herewith the additional separator  11406  and the first filter  11408  are installed in series in the supply pipeline  11388 , and the second filter  11410  is installed in the pressure pipeline  11396  between the separator  11386  and the second MGSU  11374 . 
         [0151]    The plant may be equipped with additional membrane modules (not shown at  FIG. 11 .), herewith at least one additional MGSU is connected in parallel to each of the membrane modules  11372  and  11374 . The plant may be equipped with a condensate stabilization unit  11412 , with two inlets  11414  and  11416  and four outlets  11418 ,  11420 ,  11422  and  11424 , herewith each of inlets  11414  and  1   1416  of the condensate stabilization unit  1   1412  is connected with corresponding pipelines  1   1426  and  1   1428  of the condensate removal from the additional separator  1   1406  and the separator  1   1386 , the first outlet  1   1418  of the condensate stabilization unit  1   1412  is connected to a gas stabilization flow supply pipeline  1   1430 , connected to the pipeline  1   1400 , the second outlet  1   1420  is connected to the pipeline  1   1432  of the gas mixture flow discharge to utilization, the third outlet  1   1422  is connected to the pipeline  1   1434  of the stable hydrocarbon condensate discharge to further re-processing or for downhole injection, the fourth outlet  1   1424  is connected with the pipeline  1   1436  of the water condensate discharge for downhole injection for maintaining of formation pressure or to utilization. 
         [0152]    The raw material natural gas by the pipeline  1   1388  is supplied to the high-pressure chamber  1   1376  of the first MGSU  1   1372 . The separator  1   1406  and the filter  1   1408 , installed in the supply pipeline  1   1388  can be used for preliminarily drying of natural gas. Natural gas in the first MGSU  1   1372  at the membrane  1   1380  is divided into two flows i.e. to the permeate flow under the membrane  1   1380 , and to the non-permeate; herewith the non-permeate contains no moisture in any significant amount. The non-permeate above the membrane  1   1380  from the HPC  1   1376  of the first MGSU  1   1372  is directed to the outlet pipeline  1   1390 , whereof it is directed to the consumer. From the low-pressure chamber  1   1378  of the first MGSU  1   1372  the permeate with large contents of moisture is transported by the pipeline  1   1394  to the inlet of the compressor  1   1382 , herewith the chamber  1   1378  is continuously swept with portion of the non-permeate from the first MGSU  1   1372 , supplied by the channel  1   1392 . From the outlet of the compressor  1   1382  the gas flow by the pipeline  1   1396  is directed to the refrigerator  1   1384  and then to the separator  1   1386 , wherein the gas flow is stripped of moisture and condensate. Then the gas flow via the filter  1   1410  gets to the LPC  1   1376  of the second MGSU  1   1374 . From the HPC  1   1376  of the second MGSU  1   1374  the non-permeate above the membrane  1   1380  is directed by the pipeline  1   1398  to the outlet pipeline  1   1390 . The gas mixture with large contents of moisture is supplied by the pipeline  1   1400  to the pipeline  1   1394  from the LPC  1   1378  of the second MGSU  1   1374 . The sweeping of the LPC  1   1378  of the second MGSU  1   1374  is accomplished by supply of the non-permeate from the second MGSU gas flow by the channel  1   1402 . The throttling elements  1   1404 , for example, orifices installed in the channels  1   1392  and  1   1402 , provide for the necessary flow rate of gas flow to sweeping. 
         [0153]    If the condensate stabilization unit  1   1412  is available the flows from the separators  1   1406  and  1   1386  are transported to inlets  1   1414  and  1   1416  by the pipelines  1   1426  and  1   1428  correspondingly. The gas stabilization flow from the outlet  1   1418  is directed by the pipeline  1   1430  to the pipeline  1   1400 . The gas mixture flow from the pipeline outlet  1   1420  is directed to utilization by the pipeline  1   1432 . The hydrocarbon condensate connected to the third outlet  1   1422  is deviated to the further processing or for downhole injection by the pipeline  1   1434 , and the water condensate connected to the fourth outlet  1   1424  from the condensate stabilization unit  1   1412  is deviated by the pipeline  1   1436  for downhole injection for maintaining of the formation pressure or to utilization. 
         [0154]    Sweeping of the LPC  1   1378  of the MGSU  1   1372  with drying the non-permeate flow from the first MGSU  1   1372  allowed to direct the gas flow dried in the second MGSU  1   1374  to the consumer that lead to increase of the plant capacity. Besides it gave an opportunity to carry out drying of the natural gas with higher content of the initial water and heavy hydrocarbons not only from water but also from heavy hydrocarbons. 
       EXAMPLE 15 
     Drying of High-Pressure Natural or Associated Petroleum Gas at a Two-Stage Plant Wherein the Discharge Flow From the First Stage is Purified at the Second Stage 
       [0155]    As shown at  FIG. 12  the plant for drying of the natural gas comprises two MGSUs  12438  and  12440  with a HPC  12442  and a LPC  12444 , separated by a SPM  12446 , channels  12448  and  12450  of sweeping of the LPC  12444 , a compressor  12452 , a refrigerator  12454 , a separator  124560  and a discharge pipeline  12458 . Inlet of the HPC  12442  of the first MGSU  12438  is connected with a supply pipeline  12460 , and the outlet is connected with an outlet pipeline  12462 . The LPC  12444  inlet from the first MGSU  12438  is connected with the first sweeping channel  12448 , and the outlet is connected with a pipeline  12464 , connected to the compressor  12452  inlet. The compressor  12452  outlet is connected with a pressure pipeline  12466  (with the refrigerator  12454  and a separator  12456  installed in series) with the HPC  12442  inlet of the second MGSU  12440 , the outlet whereof is connected to a pipeline  12468 . The LPC  12444  of the second MGSU  12440  is connected by a pipeline  12470  with a pipeline  12464  and with the second channel  12450  for sweeping, providing continuous supply of portion of the non-permeate from the HPC of the second MGSU  12440 . This plant is also equipped with two shut-off regulating devices  12472  and  12474 , herewith the first shut-off regulating device  12472  was installed at the pipeline  12470 , the second shut-off regulating device  12474  is installed at a discharge pipeline  12458 , that is connected with the pipeline  12470  at the section between the first shut-off regulating device  12472  and the second MGSU  12440 . The first sweeping channel  12448  provides for the possibility of continuous supply of some non-permeate from the first MGSU  12438  to the LPC  12444 , and the pipeline  12468  from the second MGSU  12440  is connected to the outlet pipeline  12462 . 
         [0156]    The plant can comprise throttling elements  12476  in the sweeping channels  12448  and  12450  for example an orifice. 
         [0157]    The plant can be equipped with an additional separator  12478  and two filters  12480  and  12482 , herewith the additional separator  12478  and the first filter  12480  are installed in series in the supply pipeline  12460 , and the second filter  12482  is installed in a pressure pipeline  12466  between the separator  12456  and the second MGSU  12440 . 
         [0158]    The plant can be equipped with additional membrane modules (not shown at  FIG. 12 ), herewith at least one additional MGSU is installed in parallel to each of the membrane modules  12438  and  12440 . The plant can be equipped with a condensate stabilization unit  12484 , with two inlets  12486  and  12488  and four outlets  12490 ,  12492 ,  12494  and  12496 , herewith each of inlets  12486  and  12488  of the condensate stabilization unit  12484  is connected to condensate withdrawal pipelines  12498  and  12500  from the relevant separators  12478  and  12482 , the first outlet  12490  of the condensate stabilization unit  12484  is connected to a pipeline  12502  of the gas flow stabilization supply, connected by the pipeline  12470 , the second outlet  12492  is connected to a pipeline  12504  of the gas mixture flow deviation to utilization, the third outlet  12494  is connected to a pipeline  12506  of stable hydrocarbon withdrawal for further re-processing or for the downhole injection, the fourth outlet  12496  is connected with the discharge pipeline  12508  of water condensate for downhole injection for maintaining of the formation pressure or to utilization. 
         [0159]    The raw material natural gas is supplied to the high-pressure chamber  12442  of the first MGSU  12438  by the supply pipeline  12460 . The separator  12478  and the filter  12480  installed in the supply pipeline  12460  can be used for preliminarily drying and purification of natural gas from mechanical impurities. Natural gas in the first MGSU  12438  is divided into two flows at the membrane  12446  i.e. to the permeate under the membrane  12446  and to the non-permeate, herewith the non-permeate does not contain any moisture in any significant amount. From the HPC  12442  of the first MGSU  12438  the non-permeate above the membrane  12446  is transported to the pipeline  12462  whereof it is directed to the consumer. The gas flow with large content of moisture from the LPC  12444  of the first MGSU  12438  is supplied by the pipeline  12464  to the compressor inlet  12452 , herewith the chamber  12444  is swept by continuous supply of portion of the non-permeate from the first MGSU  12438  by the channel  124486 . From the compressor outlet  12452  gas flow by the pressure pipeline  12466  is directed to the refrigerator  12454  and then to the separator  12456  wherein moisture is removed from the gas flow. Then gas flow via the filter  12482  goes to the HPC  12442  of the second MGSU  12440 . The non-permeate above the membrane  12446  from the HPC  12442  of the second MGSU  12440  is directed by the pipeline  12468  to the outlet pipeline  12462 . The permeate with large content of moisture from the LPC  12444  of the second MGSU  12440  is supplied by the second pipeline  12470  by the open the shut-off regulating device  12472  to the pipeline  12464 , herewith the shut-off regulating device  12474 , installed in the discharge pipeline  12458 , is closed. In case of decreasing of the quality of the drying natural gas due to excess of moisture in the permeate from the second MGSU  12440 , it is periodically discharged by the pipeline  12458 , herewith the shut-off regulating device  12472  is to be closed for a short period and the shut-off regulating device  12474  is to be open. Thus the moisture content in the permeate from the MGSU  12440  is decreased. The sweeping of the LPC  12444  of the second MGSU  12440  is accomplished by supply of portion of the non-permeate from the second MGSU  12440  by the channel  12450 . The throttling elements  12476 , for example, orifices, installed in the channels  12448  and  12450 , provide for necessary flow rate of the sweep gas. 
         [0160]    If the condensate stabilization unit  12484  is available, condensate is supplied by the pipelines  12498  and  12500  from the separators  12478  and  12456  to its inlets  12486  and  12488 . Stabilized gas is directed from the outlet  12490  by the pipeline  12502  to the pipeline  12470 . The gas mixture is directed to utilization from the outlet  12492  by the pipeline  12504 . Stable hydrocarbon condensate is taken off by the pipeline  12506  connected to the third outlet  12494  for the further reprocessing or downhole injection, and by a pipeline  12508 , connected to the fourth outlet  12496 , water condensate is deviated from the condensate stabilization unit  12484  for downhole injection for maintaining formation pressure or to utilization. 
         [0161]    Sweeping of the LPC  12444  of the MGSU  12438  with the dried non-permeate from the HPC of the MGSU  12438 , and provision of possibility of periodical discharge of non-specification gas flow from the low-pressure pipeline  12470  allowed to direct gas flow dried at the second MGSU  12440  also to the outlet pipeline to the consumer that lead to increase of efficiency of gas drying in the plant. Besides, it provided a possibility to carry out drying of gases mixture not only from water but also from heavy hydrocarbons, herewith the dried gas mixture can have higher content of the initial water and heavy hydrocarbons.