WO2001004537A1

WO2001004537A1 - A method and arrangement for impelling a non-conducting fluid in a pipeline

Info

Publication number: WO2001004537A1
Application number: PCT/NO2000/000233
Authority: WO
Inventors: Kjetil Naesje
Original assignee: Applied Plasma Physics As
Priority date: 1999-07-07
Filing date: 2000-07-07
Publication date: 2001-01-18
Also published as: AU5580000A

Abstract

The invention relates to a method and a device for propelling a non-conducting fluid in a pipeline (10), where at least one and preferably several pump devices (11) of traditional type are employed, mounted at intervals along the pipeline. In addition fluid is propelled in at least a section (1) of the pipeline by means of ion migration, resulting from the establishment of electric fields between electrodes which are provided in the pipeline.

Description

A method and arrangement for impelling a non-conducting fluid in a pipeline

The present invention relates to a method and a device for propelling a substantially non-conducting fluid in a pipeline. A well-known problem in the field of transport of fluids in pipes and pipelines is that this kind of transport can be expensive and energy- demanding due amongst other reasons to pressure loss on account of friction between fluid and pipeline. In the case of transport over substantial distances the pressure losses have to be overcome by means of pump devices arranged at intervals along the pipeline.

There is therefore a great need to provide a solution in which fluids, particularly non-conducting fluids, are propelled in a cost-effective manner when flowing in pipes. "Substantially non-conducting fluid" should be understood here to refer to all types of essentially dielectric or insulating fluids, including gases, liquids and multiphase fluids, and generally all fluids which are characterized by having poor electrical conductivity. If the fluid also contains electrically conductive components, such as water, the content thereof should be relatively low for the fluid to be specially suitable for use with the method.

There is a particular need to provide a solution of the above-mentioned kind, which is suitable for transport of gases, liquids and multiphase fluids containing petroleum products and hydrocarbons.

At the same time there is a need to prevent deposits and/or precipitation of components during transport of such fluids, which can occur particularly if there is a temporary break in the fluid flow.

When using traditional pump devices for transport of fluids in pipes, a flow profile is usually created which is characterized in that the flow rate is greatest in the middle of the pipe cross section, and least on the outer edge of the pipe cross section, near the pipe walls.

From other fields methods and devices are known for propelling fluid, especially non-conducting fluid, through pipes by means of so-called electrostatic pumps or ion drag pumps. In such pumps an electric field is established between electrodes mounted successively in the fluid's direction of flow, and the electrodes are so designed that the electric field results in a formation of ions in the fluid which is greater at one electrode than at the other. An ionic migration is thereby initiated, which further leads to a movement of fluid through the pipe. An example of such an ion drag pump is illustrated in US-A-3.398.685. In one embodiment the pump consists of pairs of electrically connected electrodes, mounted successively in the liquid's direction of flow, where voltage of opposite polarity is applied to successive electrodes, and where the electrodes are designed as cylindrical narrow portions through which the liquid flows. In a second embodiment the electrodes consist of spirals which are mounted on the outside of an insulating cylinder, mounted axially inside a cylindrical, insulating pump space.

Such ion drag pumps can provide electrostatic pumping of non-conducting liquids without the use of movable parts. However, they have several weak points. They have relatively low efficiency, and have not been shown to be suitable for areas of application where the volume flow is great, such as for example in the transport of gas or oil products.

When using electrostatic pumps or ion drag pumps where the electrodes are mounted on the outer edge of the flow cross section, a fluid flow can be provided with a flow profile which is characterized in that the flow rate is greatest in the outer edge of the pipe cross section, and least in the middle of the pipe cross section.

According to the present invention it is an object to provide a method and a device for propelling a non-conducting fluid in a pipeline, which combine and reinforce the advantages of traditional pump solutions and ion drag pumping.

This object is achieved by means of the features which will be apparent from the following, independent claims 1 and 11 respectively.

Further advantages are achieved with the features indicated in the dependent claims.

The invention will now be described in further detail with reference to the accompanying drawings, in which fig. la illustrates a profile for flow rate in pipes where traditional pump transport is employed, fig. lb illustrates a profile for flow rate in pipes with electrostatic pumping based on ion drag, fig. 1 c illustrates a profile for flow rate in pipes which can be achieved with the present invention, fig. 2 is a principle drawing in block diagrammatic form of a pipeline where a method and a device are employed according to the invention, and fig. 3 illustrates a first embodiment of a cross section of a section of a pipeline, viewed from the side, equipped with means for ion drag, for use in the method and a device according to the invention.

Fig. 4 illustrates a second embodiment of a cross section of a section of a pipeline, viewed from the side, equipped with means for ion drag, for use in a method and a device according to the invention.

Figure la illustrates how the flow rate can be distributed over a cross section of a pipe in which a fluid is transported, when the fluid is pumped through the pipe with traditional pump devices. The flow rate is greatest at the middle of the pipe cross section, and least near the pipe's walls, due amongst other things to friction between pipe walls and fluid. Figure lb illustrates how the flow rate can be distributed over a cross section of a pipe in which a fluid is transported, when the fluid is pumped through the pipe by the inside of the pipe being provided with equipment for electrostatic ion drag, and where electrodes are provided for ion drag near the pipe wall, as is the case in the method according to the invention.

With a method or device such as that in the present invention, where the use of traditional pumps is combined with devices for electrostatic ion drag mounted in pipe sections between the pumps, not only an ordinary increase in pump output is achieved as can normally be expected when several pumps are provided in succession. The different characteristics of the two propulsion principles are found to complement each other in a manner which provides a total effect which is more noticeable than the sum of the individual effects. While the traditional pump devices provide a fluid movement with a high rate of flow near the middle of the pipe cross section, but which is restricted by frictional forces near the pipe wall, propulsion solutions based on electrostatic ion drag to a great extent have opposite and compensating characteristics. The fluid movement achieved by means of electrostatic ion drag, as illustrated in fig. lb, can be considered as a liquid wall which moves at great speed. When one or more pump devices are further provided along the pipeline, thus producing traditional flow rate profiles as illustrated in fig. la, an effect is created where the pump device or pump devices are based on a fluid flow which is characterized by such a "movable liquid wall".

Figure 1 c therefore illustrates how the flow rate can be distributed over a cross section of a pipe in which a fluid is transported, when the fluid is pumped through the pipe by means of both traditional pumps and equipment for electrostatic ion drag, where ion dragging electrodes are mounted near the pipe wall.

Fig. 2 illustrates in a block diagrammatic manner a pipeline 10 which is equipped with both traditional pump devices 1 1 , mounted at intervals along the pipeline, and where a section 1 of the pipeline is also provided with internal equipment for electrostatic ion drag. The normal downstream direction for the fluid flow during operation is indicated by N.

Each of the traditional pump devices 11 may be any type which produces on its downstream side a flow profile in the pipeline where the flow rate is greatest in an area at the middle of the pipe cross section, and least near the pipe's walls. Examples of types of such pump devices are positive displacement pumps and rotodynamic pumps, including rotary pumps, sliding vane pumps, screw pumps, centrifugal pumps and piston pumps. The pump devices may be hydraulically, electrically, pneumatically or magnetically operated.

The section 1 of the pipeline which is provided with means for ion drag may be of a considerable length, for example several hundred metres, or even several kilometres. The section therefore does not appear in the form of an isolated pump, but as a segment of a pipeline which, distributed along its length, is equipped to provide special pump characteristics. A complete pipeline may consist of an arbitrary number of traditional pumps 11 and an arbitrary number 1 of pipe sections with ion drag. Between each pump 1 1 there may be located one or more sections 1 with means for ion drag. Fig. 2 also shows that the section 1 of the pipeline is connected via an electrical connection 13 to a suitable voltage supply 12, in order to provide the necessary electric fields between the electrodes in the pipeline section 1.

The section 1 with means for ion drag constitutes a substantial percentage of the length of the pipe distance between two traditional pumps 1 1. The percentage is preferably more than 50%, more preferably more than 80%, and specially preferred at least 95% of the length of the pipe section between two pumps 1 1. The advantage of having this section form as large a percentage as possible of the pipe distance between the pumps is to increase the combination effect of the two propulsion principles represented by traditional pumps and ion migration.

Figure 3 illustrates a first embodiment of a cross section of a section of a pipeline 1 , viewed from the side, which is provided internally with a device for electrostatic ion drag.

At least the internal part 3 of the pipeline's walls is made of a non-conducting material, preferably a plastic/artificial fibre material such as, for example, teflon, composite or a polyester material. The walls of the pipeline are preferably entirely composed of a non-conducting material. The material must have an appropriate physical strength, adapted to pressure and flow conditions during operation, and be chemically and physically resistant to the environment within and outside the pipeline. The material may advantageously be of the reinforced type, for example fibre glass-reinforced polyester.

In the interior of the pipeline two spiral electrodes 4, 5 are mounted. The spiral electrodes are preferably made of a conducting material of great durability. A suitable material is stainless steel. Alternatively, they may be made of a semi-conducting material or a material with slightly reduced conductivity, particularly where the electrodes also have to be arranged to develop heat energy. Specific parts of the electrodes, and particularly parts of the surface, may advantageously be made of materials with special properties, as described below. The electrodes may be hollow or solid, depending on technical considerations related, for example, to strength, weight and cost considerations.

The electrodes are preferably mounted at regular intervals in the pipeline's longitudinal direction, inside and in the vicinity of the pipe wall 3. The electrodes are kept separate from one another and from the pipe wall with suitable attachment devices (not illustrated). In one embodiment the attachment devices may consist of distance or suspension components which are preferably electrically insulated from the pipe wall, and which moreover are designed so as to offer the least possible flow resistance for the fluid. The attachment devices are electrically insulating, and may advantageously consist of the same material as the interior of the pipe wall 3. In a special case the attachment devices may be integrated in the pipe wall, forming at least two, preferably three, and possibly more longitudinal projections on the inside of the pipe wall, produced as a part of and of the same material as the interior of the pipe wall.

When a non-conducting or dielectric fluid is exposed to an electric field between a first and a second pole with opposite polarity, the formation of ions can occur round the poles. If the density of the ion formation is greater at the first pole than at the second pole, an ion migration will occur from the first pole to the second pole. This ion migration will cause the surrounding mass also to be set in motion, resulting in a movement or a tendency to movement of the total mass in a defined direction.

The term pole here should be understood as a specific part of an electrode, and particularly the part of an electrode which leads to the ion migration between the electrode concerned and a second, corresponding electrode.

Between the two electrodes 4, 5, an electric field is established by a voltage being impressed on the electrodes. The electrodes 4, 5 are thereby connected to a first 8 and second 9 connecting point respectively on a voltage source. In order to supply sufficient charge, the voltage source should preferably have a voltage level of between lkV and 150kV. In some cases even higher voltage levels may be relevant. This will vary according to the kind of fluid being transported in the pipeline 1 , the diameter of the pipeline 1 , the fluid's flow rate, the material and design of the electrodes, the distance between them, etc., and must be adapted to suit the individual case. The voltage which is supplied to the electrodes will preferably be a direct voltage, but it may also be relevant to employ voltage pulses. An overlaying of a direct voltage with voltage pulses (ripple) could influence the fluid's ionic properties, thus giving the system better efficiency at lower voltages. The choice of voltage levels together with pulse duration and frequency will again depend on the characteristics of the various remaining parts of the system, such as, for example, fluid and pipeline, and a person skilled in the art must therefore select the values which are most effective in each case.

According to the electrode device which forms part of the invention, greater density of ion formation is obtained at a first pole than at a corresponding second pole by designing the poles in such a manner that the first pole has a sharper or more pointed part or edge compared with the second pole. When the fluid comes into contact with the sharper or more pointed part or edge, high density ion formation occurs. The second pole, which has a more rounded, blunter or flatter part, is mounted at a suitable distance from the first pole, resulting in ion migration and thereby mass movement or a tendency to mass movement.

In the embodiment in fig. 3 each of the spiral electrodes has a cross section which has a first, more pointed or sharper part 6 and a second, blunter, more rounded or flatter part 7. Both electrodes have the more pointed or sharper part mounted in the same direction N in the pipe. This direction is the fluid flow's normal downstream direction.

More specifically, the spiral electrodes' cross section in the embodiment in fig. 1 is guttiform, and the electrode's sharper end is facing in the direction of the downstream fluid flow.

When voltage is impressed on the electrodes, the electrodes will form pairs of corresponding poles, facing each other and with opposite polarity, where the first pole is composed of the sharper or more pointed end of one of the electrodes, and where the second pole is composed of the blunter, more rounded or flatter part of the second electrode. When they are connected to a voltage or power supply, each of these pairs of poles establishes an electric field through the fluid, the field direction depending on the sign of the potential difference between the two poles. At the first pole, which is composed of the sharper or more pointed end 6 of one of the electrodes, a high density of ion formation will occur, and the ions formed will tend to be accelerated towards the associated, blunter, more rounded or flatter part 7 of the pole with opposite polarity. The movement of ions results in surrounding fluid also having a tendency to move in the same direction. A tendency is thereby created for acceleration or movement of the total fluid in the direction from sharper poles towards blunter poles or receptor poles, i.e. in the pipeline's downstream direction N.

This tendency to movement of fluid may result in the fluid being actively moved, if the tendency is strong enough compared with the losses which have to be overcome. It may result in the transport of the fluid being assisted, thus completely or partly offsetting other pressure loss, with the result that the need for pumping with traditional pumping stations along the pipeline is reduced.

The receptor pole, i.e. the blunter, more rounded or flatter part 7 of the electrodes, is advantageously designed in such a manner that at least a part of the surface consists of a partly conducting or semi-conducting material. In a preferred embodiment the main part of the electrode is made of stainless steel, while the surface is covered with a semi-conducting material or partly conducting material, preferably teflon (polytetrafluoroethylene, PTFE) with regulated conductivity, i.e. with added electrically conductive impurities in order to give the resulting material a specific conductivity. The partly conducting material has resistivity of the order of 10²-10¹² Ωcm, more preferably in the range 10⁶-10¹⁰ Ωcm, and specially preferred in the range 10⁷- 10⁹ Ωcm. An advantage of this is that better control is obtained of the ion migration from the corresponding, ion-generating pole, i.e. the sharper or more pointed part 6 of the corresponding electrode. If the receptor part's surface was a good conductor, an ionization of the fluid would occur in the zone around the receptor pole, which could reduce the efficiency of the device or the method. According to the invention such ionization can be prevented by at least covering a part of the receptor pole 7 by a semiconducting material.

The contribution of ion drag to fluid propulsion has been shown to be greatest when the electrodes are impressed with a voltage which is close to a limit for flashover. If such a flashover occurs, the partly conducting material helps to ensure that the electrodes or the device is not otherwise damaged, since the material distributes energy released by the flashover over a greater area. The partly conducting material also contributes to tolerance of local short circuits, which may occur if conductive liquids, e.g. water, particularly salt water, or conductive particles should appear inside the pipeline and come into contact with the electrodes.

Another effect which has been shown to be advantageous is that the partly conducting material gives rise to a power development when current is passed through the material as a result of the ion migration. This power development leads to a partial heating in the vicinity of the pipe wall and in the outer parts of the fluid flow, further contributing to reduced viscosity near the pipe wall and thereby reduced resistance to the movement of fluid and increased contribution to the propulsion of the fluid in the pipeline.

The use of a partly conducting material is particularly relevant in the embodiment of the invention where the electrodes are mounted partly integrated within the pipe wall, as illustrated in figure 4.

In an alternative operating condition the electrodes may be employed as elements for heat supply to the fluid near the pipe wall or to the actual pipe wall. By placing the electrodes in or near the pipe wall, while at the same time letting the electrodes conduct electricity and emit energy in the form of heat, a heating of the fluid and the pipe wall is achieved. Energy supply of this kind can be used as a power medium for maintaining a controlled temperature in the fluid, which is advantageous in order to avoid deposits in the event of a break in the flow. For example, by this means the precipitation of materials with a low melting point can be prevented, thereby preventing a common problem in the transport of oil and/or gas.

A particularly advantageous consequence of the method and the device according to the invention is that the fluid flow which is formed, especially when the electrodes are placed in the outer edge of the pipe cross section or in the vicinity of the pipe wall, has a velocity profile which has complementary and to some extent opposite characteristics compared with the flow rate profile for a pipe flow produced by a traditional pump. The flow rate will be greatest near the pipe wall and least near the middle of the pipe cross section. Consequently, it is particularly favourable to employ the method and the device according to the invention in combination with traditional pump solutions which on their own give the greatest flow rate in the middle of the cross section and least flow rate near the pipe walls.

In figure 4 a section of a second embodiment is illustrated, where the electrodes are still spiral in shape, but where the electrodes 24, 25 are mounted partially integrated within the pipe wall, and in such a manner that the ion-generating, sharper part is in the form of an edge 26 which projects in towards the interior of the pipe, and which preferably only just projects in towards the interior of the pipe. The blunter, more rounded or flatter receptor part is composed here of a flatter part 27, partly or preferably completely in alignment with the interior of the pipe wall 23. Here the electrodes are composed of at least two different materials, the electrode part which is depicted with a triangular cross section and of which the edge 26 forms a part consisting of a material with good conducting properties, preferably a metal material such as stainless steel, while the flatter part 27 consists at least in the surface of a partly conducting or semi-conducting material of a previously mentioned type. For each electrode these two parts are arranged close to each other and in electrical contact. Between each electrode there is an insulating material, indicated by rectangular cross sections as at 30 in the figure. The cylindrical part, which is composed of the electrodes with associated insulation material between, is mounted inside an outer pipe part 21 with a filler material 29 between, so that the electrodes form an integrated part of the pipe wall. The advantages of the partly conducting material are similar to those mentioned in the description of the embodiment in fig. 3. As an alternative to the illustrated embodiments where each electrode has a more pointed or sharper part and a blunter, more rounded or flatter part, the ion dragging effect can be achieved by providing each electrode with a first pole with a smaller area exposed to fluid in the pipe, and a second pole with a larger area exposed to fluid in the pipe. By this means the problem is avoided of the sharp edge which projects into the pipe from the pipe wall, leading to some degree of mechanical restriction in the fluid flow. A further advantage which is achieved by a pipe wall of this kind without internal rough spots is that the pipe is easier to clean physically ("plugging").

As an alternative to the spiral design in fig. 3 the electrodes may be provided in the form of connected rings or cylinders. In this case the device comprises at least one pair, and preferably a large number of pairs, of annular or cylindrical electrodes, where each electrode in each pair is electrically connected to the first or the second of two electrical conductors which are arranged longitudinally in connection with the pipe wall, preferably within or outside the pipe wall, or possibly in other suitable parts of the structure. The electrical conductors may advantageously be placed in longitudinal cavities within the actual pipe wall. In one embodiment the annular or cylindrical electrodes may be placed on the inside of the pipe wall, near the pipe wall. In one embodiment they have a guttiform cross section with the pointed, ion- generating end placed downstream of the fluid flow's main direction. In this case the rings are secured with suitable attachment means at a suitable distance apart from one another and from the pipe wall, in the same way as the attachment means described for the embodiment with spiral electrodes.

As an alternative to the spiral design in fig. 4, annular or cylindrical electrodes may be mounted completely or partly integrated with the inside of the pipe wall, and in such a manner that the ion-generating, sharper part is in the form of an edge mounted in towards the interior of the pipe, and where the blunter, more rounded or flatter receptor part is composed of a flatter part, completely or partly in alignment with the pipe wall. In both of the last-mentioned cases the receptor part may advantageously be made of a partly conducting material at least in a part of the surface.

The method and the device according to the invention permit the use of substantially longer, continuous lengths of the pipeline between each pump device, thus providing considerable advantages in the transport of, for example, oil and/or gas. In cases where there has previously been a need for pump devices installed at intervals of a few hundred metres along the pipeline, with the invention intervals of several kilometres may be sufficient between each pump device.

Since the pressure drop in the pipe lengths is reduced, it is possible to manage with less voluminous and powerful pump devices. Furthermore, the pressure required on the downstream side of the pump device will be reduced, thus permitting the use of composite and plastic materials for construction of the pipe, with resulting advantages with respect to construction, cost and investment. The method and the device according to the invention further provide the possibility of obtaining higher total flow rates than with the prior art.

Claims

PATENT CLAIMS

1. A method for propelling a substantially non-conducting fluid in a pipeline, wherein at least one pump is employed, and preferably several pumps arranged at intervals along the pipeline, which pumps provide a fluid flow with a flow profile where the flow rate is substantially greater in the middle of the pipeline's cross section than on the outer edge of the cross section, characterized in that the fluid flow in at least a section of the pipeline is also propelled by means of ion migration, resulting from the establishment of electric fields between electrodes which are mounted in the pipeline.

2. A method according to claim 1, characterized in that the ion migration results from the establishment of electric fields between at least two electrodes which are mounted in contact with the fluid in the interior of the pipeline, in the vicinity of or in direct connection with the inside of the pipe wall.

3. A method according to claims 1-2, characterized in that two successive first and second electrodes form an electrode pair, and that the electric field is the result of the application of a voltage between each electrode pair.

4. A method according to claim 3, characterized in that the ion migration is the result of each electrode being designed with a more pointed or sharper part and a blunter, more rounded or flatter part, where more pointed or sharper parts are mounted substantially in the same direction in the pipeline, the more pointed or sharper part of the first electrode in each pair substantially generating ions in the fluid, while the blunter, more rounded or flatter part of the second electrode in each pair substantially receives ions from the fluid.

5. A method according to claims 1-4, characterized in that at least one of the electrodes is made of a semi- conducting material or a partly conducting material in at least a part of the surface.

6. A method according to claims 1-5, characterized in that two electrodes are mounted in the vicinity of or in direction connection with the interior of the pipe wall, which electrodes are substantially spiral-shaped.

7. A method according to claims 1-5, characterized in that the electrodes are in the form of rings or cylinders, where each electrode is electrically connected to the first or second of two electrical conductors which are arranged longitudinally in connection with the pipe wall, where the electrical connection is designed in such a manner that two successive electrodes have opposite polarity.

8. A method according to claims 1-7, characterized in that the electrodes are designed with a guttiform cross section and mounted with the pointed end downstream of the main direction of the fluid flow.

9. A method according to claims 1 -7, characterized in that the electrodes are completely or partly integrated in the pipe wall, where the ion-generating, more pointed or sharper part is composed of an edge mounted partly inwardly towards the interior of the pipe, and where the blunter, more rounded or flatter part is composed of a flatter part, completely or partly in alignment with the pipe wall.

10. A method according to claims 1 -9, characterized in that the section of the pipeline where electrodes are mounted for propelling the fluid by means of ion migration constitutes at least 50% of the distance between pumps along the pipeline.

11. A device for propelling a substantially non-conducting fluid in a pipeline, wherein at least one pump is employed, and preferably several pumps arranged at intervals along the pipeline, which pumps provide a fluid flow with a flow profile where the flow rate is substantially greater in the middle of the pipeline's cross section than on the outer edge of the cross section, characterized in that the device comprises electrodes mounted in at least a section of the pipeline, where electric fields are established between the electrodes, resulting in ion migration leading to propulsion of the fluid.

12. A device according to claim 11, characterized in that it comprises at least two electrodes, mounted in contact with the fluid in the interior of the pipeline, in the vicinity of or in direct connection with the inside of the pipe wall.

13. A device according to claims 1 1-12, characterized in that two successive first and second electrodes form an electrode pair, and that the electric field is the result of the application of a voltage between each electrode pair.

14. A device according to claim 13, characterized in that the ion migration is the result of each electrode being designed with a more pointed or sharper part and a blunter, more rounded or flatter part, where more pointed or sharper parts are mounted substantially in the same direction in the pipeline, the more pointed or sharper part of the first electrode in each pair substantially generating ions in the fluid, while the blunter, more rounded or flatter part of the second electrode in each pair substantially receives ions from the fluid.

15. A device according to claims 1 1-14, characterized in that at least one of the electrodes is made of a semiconducting material or a partly conducting material in at least a part of the surface.

16. A device according to claims 1 1-15, characterized in that it comprises two electrodes in the vicinity of or in direction connection with the interior of the pipe wall, which electrodes are substantially spiral-shaped.

17. A device according to claims 1 1-15, characterized in that the electrodes are in the form of rings or cylinders, where each electrode is electrically connected to the first or second of two electrical conductors which are arranged longitudinally in connection with the pipe wall, where the electrical connection is designed in such a manner that two successive electrodes have opposite polarity.

18. A device according to claims 1 1-17, characterized in that the electrodes are designed with a guttiform cross section and mounted with the pointed end downstream of the main direction of the fluid flow.

19. A device according to claims 11 -17, characterized in that the electrodes are completely or partly integrated in the pipe wall, where the ion-generating, more pointed or sharper part is composed of an edge mounted partly inwardly towards the interior of the pipe, and where the blunter, more rounded or flatter part is composed of a flatter part, completely or partly in alignment with the pipe wall.

20. A device according to claims 11-19, characterized in that the section of the pipeline where electrodes are mounted for propelling the fluid by means of ion migration constitutes at least 50% of the distance between two pumps along the pipeline.