WO2012023859A1

WO2012023859A1 - Method and device for attraction of a substance having dipolar properties onto an object surface in a distillation process

Info

Publication number: WO2012023859A1
Application number: PCT/NO2011/000225
Authority: WO
Inventors: Harald Nes RISLÅ
Original assignee: Viking Heat Engines As
Priority date: 2010-08-18
Filing date: 2011-08-16
Publication date: 2012-02-23
Also published as: NO20101159A1

Abstract

An apparatus (3) for distilling fluid, in which, in a container (30), one or more condensing units (321) is/are arranged, and in which, in an operating state, the at least one condensing unit (321) is arranged in an electric field (2), the electric field (2) being non-uniform and concentrated in a direction towards the condensing unit(s) (321). A method of distilling fluid by the use of an apparatus in accordance with the invention is described as well.

Description

METHOD AND DEVICE FOR ATTRACTION OF A SUBSTANCE HAVING

DIPOLAR PROPERTIES ONTO AN OBJECT SURFACE IN A DISTILLATION PROCESS

An apparatus for distilling fluid is described, characterized by there being one or more condensing units arranged in a container, and the at least one condensing unit being

arranged, in an operating state, in an electric field, the electric field being non-uniform and concentrated in a direction towards the condensing unit(s).

Also, a method of distilling fluid is described, in which a raw fluid is carried into a container containing one or more condensing units, in which a non-uniform electric field concentrated in a direction towards the condensing unit(s) is created, and dipolar molecules are provided from the raw fluid, and by means of electrostatic force the molecules are concentrated at the condensing unit(s), the dipolarity of the molecules providing a charge potential relative to the condensing unit(s) large enough to move the molecules towards the condensing unit(s).

There are huge amounts of water on the earth. Still, large parts of the world suffer water shortages because much of the water that is available is not of such quality that it can be used by human beings, animals or other organisms. The major part of the accessible water on the earth is in the form of salt water in the vast oceans. Generally, land-based organisms cannot utilize sea water as they are not adapted to the high salt concentration of salt water. Further, much of the fresh water is unavailable for human use, as large parts exist in the form of ice, and other major portions are contaminated with contaminating substances or dangerous micro-organisms. In large parts of the world there are therefore shortages in clean drinking water and fresh water for other purposes for human beings.

Various solutions for providing clean water exist. Minerals, contamination or micro-organisms may be removed by means of filters, or contaminated water may be distilled to give clean fresh water.

Among the established technologies, there are, among others, the multi-stage flash (MSF) distillation, multiple-effect distillation (MED) , vapour-compression (VC) distillation, reverse-osmosis (RO) desalination and low-pressure/low- temperature (LPLT) distillation, also called vacuum

distillation, also often described within the art of water desalination as low-temperature thermal desalination (LTTD) . Technologies such as MSF and MED and, moreover, several of the other technologies require large amounts of quality energy per unit of fresh water produced. MSF typically requires 25 kWh per cubic metre. RO is among the most energy- efficient ones, with energy consumption down towards 2.5 kWh per cubic metre in the largest plants. RO plants are

therefore also among the most widely-used plants. Still, several of the existing RO plants are of a smaller scale, and in general they have energy consumption that is much higher, for example up towards 20 kWh or more per produced cubic metre at the smallest plants. In addition, quality energy in the form of electricity, for example, is required for RO systems. Therefore, in cases in which smaller amounts of water are to be produced than in the large industrial plants, it will be disadvantageous in terms of energy to make use of this technology. There are other technologies that may be used as well, but in general they are more energy- intensive, require higher process temperatures or have other drawbacks which make them less suitable in situations in which the supply of quality energy is limited or expensive.

In such cases it may be favourable to consider LPLT

distillation, as this principle enables utilization of heat at low temperatures, which is cheap and easily available many places in the world. For example, in regions with great shortages of fresh water, there is often much irradiance as well. In other places, there may be much waste heat available from different activities. In cases like these, in which larger amounts of low-grade heat (for example, at lower temperatures such as 40-90 °C) are available, LPLT

distillation can be used as one of the few alternatives for fresh water production, in which the low-grade heat is included as the most important energy source. The reason for this is that at lower pressures the boiling point of water is lower as well and, theoretically, boiling may occur right down towards 0 °C, depending on the pressure level. For example, at an absolute pressure of 23 millibars, the boiling point of water is just 20 °C. This also works the other way round; by vapour/liquid equilibrium in a closed vacuum tank containing some water at 20 °C, a pressure of approximately 23 mbars will be achieved at equilibrium. In an LPLT process, vacuum is created in a closed container (evaporator chamber) , and relatively warm water (for example 50 °C) will be boiled so that some of the water will enter the gaseous state, whereas minerals, micro-organisms et cetera will remain in the residual water, also called brine. A condenser, which is actually a liquid/gas heat exchanger, communicates with the evaporator chamber, and by circulating a cold medium (for example 20 °C) in a closed circuit in the condenser, the heat of the vapour may be carried away, and the vapour will be condensed back into clean water.

One of the greatest problems with LPLT distillation is that the low pressure causes the density of the vapour to be very low, and thereby the thermal conductivity is low as well, which conventionally makes large condenser units be required, as the cooling surface in them must be considerable for the rate of condensation to be high. Therefore, the condensers often constitute a considerable part of the costs of an LPLT plant .

Another problem with conventional LPLT distillation is that the vapour temperature in the condenser unit will always be lower than the input temperature of the supply water, as the reduction in pressure owing to the vacuum will also lead to the temperature of the vapour being lowered because of the adiabatic expansion occurring in the remaining vapour as a chilled surface condenses away the vapour present. The vapour pressure that will be achieved in such a process will, in other words, be somewhere between the vapour pressures of water at the input temperature and condenser temperature, respectively. Thereby the vapour temperature will also be somewhere between the temperature of the supply water and that of the condenser surface, respectively, but never as high as the input temperature. This results in just a minor portion of the heat available in the supply water being recoverable, because the vapour will not be able then to heat the cooling water in the condenser as high as up towards the input temperature .

The negative effects of vapour at low density and adiabatic temperature reduction may be counteracted by forcing the gas molecules towards the condensing surface by supplying kinetic energy, for example by increasing the pressure or by setting the gas into motion towards the condensing surface. The first method is ruled out in a process using evaporation of water under low pressure, as the process will then stop. Setting the gas molecules into a more vigorous motion is not

considered to be particularly effective either, by the very fact that the molecule density is not changed by such energy supply .

It is common knowledge that a thin, falling water jet is attracted to an electrically charged glass rod or its equivalent. This is owing to the fact that the water molecules (H₂0) , like many other molecules, have a non-uniform

distribution of positive and negative charges on the

different atoms of which the molecule is composed. Water molecules (in vapour form) have a dipolarity of about 1.85 debyes (D) . The dipolar properties of water are illustrated in the figures 1-3.

From WO 2008/088211 A2 , a method and device for purifying a liquid comprising liquid particles and residual particles are known, the method comprising the steps of a) heating the liquid to be cleaned of residual particles, b) carrying the liquid in the form of liquid droplets into a purification space, c) applying a similar electric charge to the liquid droplets and to the condensation surface, d) evaporating the liquid particles in the purification space, condensing the evaporated liquid particles so that they form a condensate on the condensation surface while, because of their having the same charge as the condensation surface, the liquid particles are repelled. The condensate and the unevaporated droplets are carried away in separate drains.

From GB 827425, a vapour-to- liquid-phase apparatus is known, which includes condensation-core-producing means and heat transfer means to bring about condensation of vapour into liquid. The condensation-core-producing means create

condensation cores by evaporating an electrode substance by means of a flame arc.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to the prior art.

The object is achieved through features which are specified in the description below and in the claims that follow.

By utilizing precisely the dipolar properties of the water, it is possible to increase the density of water vapour if it is within a so-called non-uniform electric field. In a nonuniform electric field (as opposed to a uniform electric field) , forces will be created on molecules with dipolar properties, whereby they will then be attracted towards the source of the electric field if the strength of the electric field increases towards it. By electrically charging a heat exchanger surface, an electric field will be created around it. If the geometry and arrangement of the surface are of such a design that the field is non-uniform, water molecules will be attracted to the surface if the field strength of the electric field is highest near the surface. Because of the increased attractive forces in towards the surface of the heat exchanger, the pressure and density of the vapour will increase as well. This, in turn, may provide higher heat transmission as the increased density will result in the thermal conductivity of the vapour being higher.

An apparatus is provided, comprising a container provided with a chamber in which a non-uniform electric field is created. Vapour is carried into this field, in which one or more condenser units are arranged. The vapour may be provided from an external evaporator or by evaporating raw fluid which has been brought into the chamber, for example by evaporation from an internal water volume or from water particles being formed by raw water being injected through one or more nozzles .

The container in which the condensation takes place may exhibit any pressure, as the principle of the invention may be applied to different stages of multi-stage distillation processes, even where atmospheric pressure or overpressure is used, but the invention is particularly suitable in negative pressure distillation in which the condensation takes place in a negative pressure container.

The container is provided with barriers creating liquid collection around the condensing unit(s), directing the condensed water to the drain and keeping it separated from the injected raw water, water vapour and brine run-off, that is to say raw-water drops forming precipitation on the surfaces in the evaporation chamber.

Preferably, the barriers also form drop catchers that prevent drops of injected water from mixing with the condensed water.

Non-condensable gases are carried out of the apparatus through a suitable port in the container.

The voltage supply may be an ordinary DC voltage source but may also be a static generator, for example a Van de Graaff generator or the like.

In one embodiment, the condenser surface itself is not electrically charged. If, for example, an electric field is created between two metal plates by an electric potential difference having been established between them, the field between them will be substantially uniform apart from at their outer boundaries, at which the field will extend somewhat outwards, as it is illustrated in figure 4. A nonuniform field is created by placing one or more or more physical objects in the field between the metal plates. Such an object may be, for example, a metal pipe, a spiral of a pipe, a number of pipes between the metal plates or any other arrangement of a number of objects. The electric field in towards an object will be deflected towards it, so that the strength of the electric field will increase the closer one gets to the object. If, for example, pipes are used, they may be part of the condenser, and even if the pipes will not have a net electric charge, forces are created between the pipes and the vapour, which will, in turn, lead to an increased rate of condensation on the pipes.

There are several possible arrangements in which a nonuniform electric field that may contribute to increasing the rate of condensation of vapour onto a condenser surface can be created.

In a practical embodiment, a cylindrical condensation tank may be made, formed out of an electrically conductive

material, and an electrically conductive pipe of a smaller diameter which is positioned concentrically inside it. This electrically conductive pipe may be insulated or uninsulated. A series of pipes is arranged in the annular space in the tank, the pipe arrangement constituting the actual condenser, as it is shown in figure 17. In the pipe arrangement,

hereinafter also called the condenser, a cooling liquid may be circulated. An electric potential difference is created between the tank and the central pipe. Because of the

influence of the condenser on the electric field that will then arise in the tank, the field will be deflected towards the central pipe (shown in figure 18) , and a fluid with dipolar properties will be attracted and condensed onto the condenser, but at a higher rate than if the electric field was not present. The rate of condensation increases because of increased heat transmission. This embodiment may also include an assembly of several electrodes and condenser units as described above.

A cooling medium may often be electrically conductive, in particular if water containing minerals and ions is used. In another embodiment, the condenser is connected to earth through the cooling medium, and the condenser has the

character of an electrode with a potential equal to the earth potential. To avoid potential differences through the cooling medium and thereby a risk of an electric shock, it will be advantageous in an embodiment like that to provide an

effective earth connection by connecting an electrical conductor between the condenser and the earth of the system.

In yet another embodiment, a condensation tank is formed out of an electrically insulating material, and an electrically insulated condenser object is charged electrically, whereupon water vapour will be attracted and condensed at a higher rate than if the condensing unit was not charged.

In a further embodiment, the condensation tank is formed out of an electrically insulating material, in which two

electrically insulated condenser objects are charged

electrically, with opposite or equal charges, whereupon water will be attracted and condensed onto both, but again at a higher rate than if the condensing units were not charged.

Other configurations, in which a non-uniform (deflected) electric field is created, the field strength increasing in towards the condensing units, can be used as well. In a first aspect, the invention relates more specifically to an apparatus for distilling fluid, in which one or more condensing units are arranged in a container, characterized by the at least one condensing unit being arranged, in an operating state, in an electric field in the condensing chamber, the electric field being non-uniform and

concentrated in a direction towards the condensing unit(s) .

The container may be arranged to be able to maintain an internal negative pressure.

The container may form a vapour chamber, in which, in an upstream portion, a raw-fluid inlet is arranged, and a condensing chamber, in which a downstream portion contains the at least one condensing unit.

The electric field may be provided by an electric DC voltage source being connected to one or more of the container, a centre electrode and one or more of the condensing units.

The electric DC voltage source may be a static generator.

The raw- fluid inlet may include one or more drop-producing injection nozzles.

The condenser may include a fluid barrier separating the upstream portion of the vapour chamber from the downstream portion of the condensing chamber.

A drop catcher may form a boundary of the vapour chamber towards one or more vapour ports forming each a passage between the vapour chamber and the condensing chamber.

In a second aspect, the invention relates more specifically to a method of distilling fluid, in which a raw fluid is carried into a container containing one or more condensing units, characterized by the method including the further steps of:

a) creating a non-uniform electric field in the container, concentrated in the direction towards the condensing unit(s); b) providing dipolar molecules from the raw fluid;

c) concentrating the molecules at the condensing unit(s) by- electrostatic force, a net force great enough to move the molecules towards the condensing unit(s) being applied to each dipolar molecule in the non-uniform field.

The method may be practised by a negative pressure in the container .

The method may include the further step of :

providing the electric field by connecting an electric DC voltage source to one or more of the container, a centre electrode and one or more of the condensing units .

The method may include the further step of:

providing fluid particles in drop form in the vapour chamber by injecting raw fluid through one or more injection nozzles .

The method may include the further step of:

keeping the raw fluid and the condensate separated by means of a fluid barrier which surrounds the vapour chamber and is fluid-tight at least in a bottom portion.

The method may include the further step of :

impeding the movement of fluid particles in drop form from the vapour chamber to the condensing chamber by

directing the fluid vapour through a drop catcher arranged in a downstream portion of the vapour chamber.

The raw fluid may be contaminated water or salt water.

In what follows, an example of a preferred embodiment is described, which is illustrated in the accompanying drawings, in which:

Figure 1 shows schematically a water molecule, H₂0

(dihydrogen monoxide molecule) , it being illustrated that the water molecule is

asymmetrical, thereby forming the basis for an electric dipole with a dipole distance 1 ;

Figure 2 shows a simplified model of the dipole depicted as two equally large, opposite point charges connected by a rod;

Figure 3 shows a net force which will be applied to a water molecule which is in a non-uniform electric field;

Figure 4 shows schematically a uniform electric field, in which a potential difference has been applied to two electrically conductive plates (usually metal) ;

Figure 5 shows schematically a non-uniform electric field, in which, between the two energized plates,

respectively a conductor and an insulator are placed in the resulting electric field;

Figure 6 shows schematically a non-uniform electric field created between a metal pipe and a metal plate;

Figure 7 shows schematically a non-uniform electric field created between a metal pipe and two metal plates flanking it;

Figure 8 shows schematically a non-uniform electric field created between two metal pipes;

Figure 9 shows schematically a classic example of a coaxial arrangement, in which a pipe is arranged coaxially in a larger pipe and a symmetrical but still nonuniform electric field is created in an annular space between the pipes;

Figure 10 shows a more complex way of creating a non-uniform electric field, as pointed conductive objects are arranged on the surface of an electrical conductor;

Figures 11a and lib illustrate how a water molecule is

attracted to an increasing electric field in a coaxial assembly, the dipolar properties of the water being illustrated in figure lib in the form of a simplified rod/ball representation of the molecule ;

Figures 12-14 show one-dimensionally indefinitely repeatable arrangements of the basic arrangements shown in figures 5, 6 and 7, respectively;

Figures 15-16 show a two-dimensionally indefinitely

repeatable arrangement of the basic arrangements shown in figures 5 and 7, respectively;

Figures 17a and 17b show, respectively, a radial section, indicated by a-a in figure 17b, and an axial section, indicated by b-b in figure 17a, through an embodiment of an electrostatic vacuum condenser;

Figure 18 show a possible distribution of the electric field that will form in the condenser shown in figures 17a and 17b;

Figures 19a and 19b show the direction of force on water

molecules by alternative electrode set-ups;

Figure 20 show a complex arrangement consisting of several electrode arrangements as shown in figure 19b; Figures 21a and 21b show more complex assemblies of possible electrostatic condenser solutions; and

Figure 22 shows an alternative embodiment of the condenser according to the invention in an axial section.

In figures 1-3, the reference numeral 1 indicates a water molecule formed by one hydrogen atom H and two oxygen atoms O. A dipole distance, that is to say the statistical distance between the opposite charges, is indicated by the distance 1 in figures 1 and 2. Viewed statistically, the water molecule 1 is most positive in the regions around the hydrogen atoms H and most negative around the oxygen atom O, as the oxygen atom O has a greater tendency to attract the negatively charged electrons than the hydrogen atoms H have.

In addition to the dipole distance 1, a dipole has a

particular dipole moment which is the product of the electric charge and the dipole distance, and in the case of a molecule (as opposed to a number of free charges or ions having different ion numbers), the dipole moment is constant.

Thereby the dipole moment of the water molecule 1 is constant and is 6.2 x 10^"30 Cm (coulomb metres) . This is very small because the electric elementary charge (the charge of an electron or a proton) is small in itself (measured in

coulombs) and, also, the statistical separation distance 1 between the asymmetrical charges of the water molecule 1 is very small, only 0.0039 nm, or 3.9 x 10^-12 m. The vectorial direction of the dipole moment always goes from a negative charge towards a positive one.

A net force F will be applied to a water molecule 1 which is in a non-uniform electric field 2 (see figure 5) . If the same molecule is placed in a uniform electric field 2a (see figure 4) , the net force exerted on the molecule 1 will be 0. The moment, on the other hand, does not have to be 0, depending on the rotation/direction of the molecule 1. The reason why a non-uniform electric field 2 will result in a net force F on the molecule 1 is that the separation between the

statistically negative and positive charges results in the side that is the closest to the stronger part of the electric field experiencing greater attraction, or repulsion, because the gradient of the non-uniform electric field 2 suggests that the field strength is greater in some places than in others, and thereby there will also be greater forces exerted on the side of the dipole that is in an area in which the electric-field strength is greater.

Figure 4 shows a classic example in which a potential

difference is applied to two electrically conductive plates 30, 31, usually formed out of a metal, a uniform electric field 2a thus being created between them. It should be noted that the electric- field lines at the ends of the metal plates 30, 31 deflect outwards, thereby forming non-uniform

subfields 2b, but, in practice, it may be said that as long as one is well within the outer limits of the metal plates 30, 31, the field 2a may be counted as uniform. The uniform field is indicated by the field lines being parallel and having the same distance from each other.

A method for creating a non-uniform electric field 2 between two energized metal plates 30, 31 is placing a conductor 321 or an insulator 322 in the resulting electric field, as illustrated in figure 5. The conductive or insulating objects 321, 322 will then attract the electric- field lines in such a way that they are condensed, the field gradient increasing in towards them. As for the insulator 322, the electric field 2 will pass through it, whereas for the conductor 321, it will follow its outside, as the electric field internally in electrical conductors will always be 0 according to Faraday (ref. Faraday's cage).

Figure 6 shows a non-uniform electric field 2 between a metal pipe 321 and a metal plate 30. The electric- field strength will, in this case, increase in towards the metal pipe 321, and this is illustrated by the field lines becoming_. condensed in towards it. In this case, the pipe 321 is positively charged relative to the metal plate 30. This may be done, for example, by connecting a voltage generator / voltage source 38 (see figure 17b) to the two objects 30, 321, wherein a positive electrode (not shown) is connected to the metal pipe 321, and a negative electrode (not shown), often defined as earth, is connected to the plate 30.

In figure 7, which shows a variant of the device in

accordance with figure 6, a pipe 321 with a positive electric potential is arranged between two negative metal plates 30, 30, and the electric- field lines extend towards the pipe 321 from both plates 30, 30. In this way a non-uniform electric field 2 covering a larger area than in the embodiment

according to figure 6 may be achieved.

Figure 8 shows a classic example of a non-uniform electric field 2 created between two metal pipes 321 with opposite electric potentials. It is worth noting that the electric field 2 between the pipes 321 is condensed towards both pipes 321, and the lowest field strength is found halfway between the pipes 321. This means in practice that dipole molecules 1 will be attracted to both pipes 321, but always to the pipe 321 which is the nearest, as the position-dependent field strength will be highest here.

Figure 9 shows a classic example of a coaxial arrangement, in this case a pipe 31, hereinafter also called centre electrode, inside a larger pipe 30. A symmetrical, but still non-uniform, electric field 2 is created in an annular space between the pipes 30, 31. The field strength increases in towards the centre electrode 31. This can be seen visually by the field lines in towards the centre electrode 31 being convergent .

A more complex way of creating a non-uniform electric field is shown in figure 10. On the surface of an electrical conductor (for example a plate or a pipe 30, 31) with

projecting, pointed, conductive objects 302, in this case metal needles or pointed conical metal spikes. This principle has been suggested inter alia in US 2001/0029842 Al which deals with an air dehumidifier, in which the water in the air will be attracted to the strong electric field that arises around the pointed objects on the metal surface, onto/from which it is thus intended to condense and fall into a

collector .

The figures 11a and lib illustrate how a net force is applied to a water molecule 1 in the non-uniform electric field 2 in a coaxial assembly. Figure lib illustrates the dipolar properties of the water in the form of a simplified rod/ball representation of the molecule 1. It is pointed out that, visually, it has not been taken into account that the forces on the molecules do in fact increase with the proximity to the centre electrode 31, as, for simplicity, all the power symbols have been drawn with equal lengths. Actually, the forces F increase the closer the dipoles 1 are to the centre electrode 31. Figure 11a only gives an illustration of the directions of the forces F.

The arrangements shown in figures 12-14 may be termed one- dimensionally indefinitely repeatable because they have been repeated only along one longitudinal direction/axis , from left to right, or vice versa, in the figures 12-14.

The arrangements shown in figures 15 and 16 can be termed two-dimensionally indefinitely repeatable because they have been repeated along two longitudinal directions/axes, as shown in the figures 15 and 16 in the X and Y directions.

The figures 12-16 show that electrode arrangements may be extended, so that condensers of different sizes may be achieved, according to whatever the need may be. This idea may also be extended into including three-dimensionally repeatable arrangements.

A practical embodiment of an electrostatic condenser 3 is shown in figure 17a in a radial section and in figure 17b in an axial section. Arranged concentrically in a tubular closed condenser tank 30, there is a centre pipe 31 which is electrically isolated from the condenser tank 30 and is provided with an electrically conductive middle portion 31a which is connected to a voltage source 38 via a wire 311 which has been extended into the condenser 3 through a pressure-tight nipple 312. Thereby the centre pipe 31 forms an inner electrode. The condenser tank 30 may be constituted by, for example, a metal pipe or a plastic pipe whose ends are closed with electrically insulating end covers 301 that hold the centre pipe 31 fixed at the same time. If the condenser tank 30 is formed out of a metal pipe, this will have to be earthed and will then function as an outer electrode as well. The distribution of the electric field 2 created within the condenser tank 30 will then be different than if this consists of a plastic pipe, which is an

insulator. A vapour inlet 35 and a condensate outlet 33 are arranged in the condenser tank 30. A condensation arrangement 32 including several condensing units 321 which are formed of continuous cooling pipes 321a, 321b, is arranged in the annular space in the condenser tank 30 and is provided with a cooling-liquid inlet 321c and a cooling-liquid outlet 321d and is connected to a plant (not shown) for the circulation of cooling liquid. If a metal pipe is used as the condenser tank 30, the condensing units 321 may be formed out of earthed cooling pipes 321a or electrically insulated cooling pipes 321b, and an electric-field distribution as indicated in figures 12 and 13 will be achieved.

The centre pipe 31 is provided with radial cut-outs 315 for vapour pressure balancing between the annular space of the condenser 3 and the interior of the centre pipe 31.

The condenser 3 is provided with an outlet 34 for evacuating non-condensable gases.

A bottom portion 313 of the centre pipe 31 forms a fluid barrier 312 between the vapour chamber 37 and the condensing chamber 371.

Figure 18 shows the distribution of the electric field 2 which is formed in the condenser 3 described above and shown in figures 17a and 17b. On a larger scale, a section of the field 2 is shown as well, in which it is indicated how the forces F are applied to the water molecules 1 in consequence of the water molecules 1 being in the non-uniform electric field 2. The field that is shown in figure 18 is basically conditional on the condensing units 321 being formed out of cooling pipes 321b electrically insulated against the cooling liquid, so that it will not have any connection to earth via an electrically conductive, non-pure cooling liquid. Such insulation may be carried out by applying an electrically insulating layer (not shown) to the inside of the cooling pipe 321b, for example. Another way of providing this is using an electrically non-conductive cooling liquid. Figure 19a shows a section of the field 2 which will form in the condenser 3 described above if the cooling pipe 321a is earthed. In that case, most of the field lines will terminate in the cooling pipe 321a, instead of passing via this and in to the external wall 30 of the condenser 3, as shown in figure 18.

Figure 19b shows a section of the field 2 which will form in the condenser 3 described above if two separate cooling pipes 321a are used in the condenser 3, the two being of opposite polarities. The field lines will then extend from the

positive pipe to the negative pipe 321a and terminate here. In this way an electric field 2 can be created that is more or less independent of other physical components in the condenser 3.

Figure 20 shows a complex arrangement consisting of several electrode arrangements in accordance with figure 19b.

Figure 21a shows a solution in which several intermediate pipes 30' are arranged concentrically in the annular space between the condenser tank 30 and the centre electrode 31, and in which the cooling pipes 321b, which are arranged in the annular space formed by the intermediate pipes 30' and the centre electrode 31, do not have the function as

electrodes but only as condensing objects for the electric fields 2 that will form between the, in this case, concentric electrodes 30, 30', 31. The concentric electrodes 30, 30', 31 in this arrangement have alternatingly opposite polarities in a radial direction. Every other electrode 30, 30' in this arrangement is also earthed, that is to say that one set of electrodes 30, 30' is defined with an electric potential equalling the earth potential .

Figure 21b shows a solution in which the cooling pipes 321a are earthed and function as electrodes. There are also several concentric non-earthed electrodes formed by- intermediate pipes 30' which will then be of an opposite polarity relative to the cooling pipes 321a. For safety reasons, the outer wall/pipe of the condenser tank 30 will have to be earthed, but will, basically, not have a function as an electrode.

Figure 22 shows an axial section through an exemplary

embodiment of the condenser 3 in which the centre pipe 31 (the centre electrode) forms a vapour chamber 37 which is provided, in an upstream portion, with a raw-fluid inlet 35 including injection nozzles 351 and being connected to an evaporator (not shown) via a vapour line 352, and also, in a downstream portion, is provided with several vapour ports 315 forming connections to an upstream portion of the annular space outside the centre pipe 31. The annular space forms a condensing chamber 371 which is provided with a condensate drain 33 including several condensate outlets 331 connected to a condensate line 332. A lower portion of the centre pipe 31 forms a fluid-tight barrier 312 between the raw water and the condensate. At the lower edge of the vapour ports 315, the centre pipe 31 is provided with a drop catcher 314 arranged to inhibit the movement of raw-water drops through the vapour ports 315 and into the condensing chamber 371. In the condensing chamber 371, several condensing units 321 are arranged, provided with condensing surfaces 322 to improve the condensation efficiency. Electrical conductors and electrical insulation means are not shown, as, with respect to the provision of an electric potential and field

influence, the condenser 3 may be built in accordance with the principles described above.

Alternatively, the exemplary embodiment shown may be connected directly to an external evaporator (not shown) without the use of injection nozzles 351. The vapour chamber 37 and the condensing chamber 371 may be a continuous volume without defined barriers, as raw fluid and vapour are already effectively separated in the external evaporator. This entails that the task of the centre pipe 31 as a fluid barrier is eliminated, and the form of the centre pipe 31 as a mere electrode can be changed substantially in relation to what is shown in figure 22.

The condenser 3 is meant to operate at pressures lower than atmospheric pressure, at vacuum, that is. Before the process is started, air and other non-condensable gases are evacuated by means of a vacuum pump (not shown) which is connected to the gas outlet 34. The vacuum pump continues pumping after the process has started, as water always contains a certain amount of non-condensable gases. These must be removed because they prevent efficient heat transmission between the water vapour to be condensed and the condensation arrangement 32 of the condenser 3.

Chilled cooling liquid is circulated through the cooling pipes 321a, 321b. The cooling liquid absorbs as much as possible of the heat of the incoming water vapour through the wall of the cooling pipes 321a, 321b, so that the water vapour is condensed into liquid form.

The condensable dipolar water vapour is carried into the condenser 3 via the vapour inlet from the external evaporator (not shown) . The water vapour will condense into liquid when it gets into contact with the cold condensing units 321.

In a preferred embodiment, the system operates under vacuum all the time, as it is possible, by lowering the pressure, to lower the boiling point of the liquid, for example salty raw water, and then it will be possible to utilize the thermal energy stored in the liquid which would not otherwise be utilizable if the system had operated under normal

atmospheric pressure.

As this condenser 3 is also meant to function as a condenser in a water treatment system, for example a water desalination system, it is also possible in such a case to implement an evaporator part (not shown) in the centre pipe 31 of the condenser 3 instead of introducing vapour from an external evaporator. The inlet 35 then carries raw water which is to be purified into the condenser 3, it being atomized by means of the injection nozzles 351. The raw water may also be carried into the condenser 3 without atomization, as the raw water will boil by low temperature in the negative pressure container 30. A residual-fluid drain 36 is arranged in the lower portion of the centre pipe 31 to drain the brine from the centre pipe 31 of the condenser. The raw water may be taken directly from a water source or be conveyed via the condensation arrangement 32 in which it is utilized as a cooling liquid in order thereby to be supplied with thermal energy.

To maintain a desired pressure, the system must have more pressure-adjusting means (not shown) , known per se, than the pump, not shown, connected to the gas outlet 34, as the pressure should also be controlled relative to the other inlets 35 and the outlets 33, 36 of the system. The extended pressure system is not a subject of this application, which focuses mainly on the exploitation of electrostatic

principles to increase the rate of condensation.

When the process is up and running, that is to say that the desired pressure has been established, circulation of cooling water has started and vapour is being generated in the external evaporator not shown, an external high-voltage generator 38 (see figure 17b) is activated. This may provide voltage of up to several tens of kilovolts or even higher. The high-voltage generator 38 has an earth connection which is connected to a common earthing bus in the system. In addition, one or more components 30, 31, 321 in the condenser 3 is/are earthed as well, so that the whole system is

referenced against a common electric potential. It will be natural to earth the condenser tank 30, the outer pipe that is, and possibly also the condensation arrangement 32, so that there is no risk of an electric shock when the outer portions of the condenser is touched. The high-voltage generator 38 has one or more outputs (not shown) for high- voltage electrodes. A high-voltage output on the high-voltage generator 38 is connected to the centre electrode 31 of the condenser 3 by means of a high-voltage cable 311 which may be inserted through a pressure-tight nipple 311a (see figure 17b) . The polarity of the electrode may be negative or positive relative to the common earthing bus of the system. The case is, in fact, that the electrode polarity must often be specified when industrial high-voltage generators are purchased. It is assumed that in the exemplary embodiments discussed, the polarity is positive, and earth will then be negative relative thereto.

When the electrode formed on the centre pipe 31 is energized, a characteristic electric field will form between the centre pipe 31 and earthed components in the system. The aim is here to create non-uniform electric fields, the strength of the field increasing in towards the condensing units 321, so that dipolar gas molecules 1 that are to be condensed will be attracted towards them. In this way the heat transmission between the gas and the condensing units 321 will be enhanced in that all the individual forces F acting from the gas molecules in towards the condensing units 321 increase. The practical result of this will be that the local pressure and also the local density of the gas molecules in the immediate vicinity of the condensing units 321 will increase, and then the heat transmission will increase as well. A fluid of high density has a higher thermal capacity per unit of volume than the same fluid at a lower density. The important result of this is that the heat transmission can be increased without an increase in the size of the heat-exchanger surfaces 322 of the condenser 3 being required, and thereby the cost and size characteristics of the system may be improved. In addition, a higher temperature is achieved in the vapour at the

condensing surface 322, and thereby better energy

transmission could be achieved as more heat may be absorbed by the cooling water in consequence of the greater

temperature difference.

Even though, to a large extent, the treatment of water has been described in the above, the invention also includes the condensation of other fluids with dipolar molecules through gas concentration by means of non-uniform electric fields.

Claims

P a t e n t c l a i m s

1. An apparatus (3) for fluid distillation, in which there are one or more condensing units (321) arranged in a container (30), c h a r a c t e r i z e d i n that, in an operating state, the at least one condensing unit (321) is arranged in an electric field (2) , the

electric field (2) being non-uniform and concentrated in a direction towards the condensing unit(s) (321) .

2. The apparatus in accordance with claim 1,

c h a r a c t e r i z e d i n that the container (30) is arranged to enable the maintenance of an internal negative pressure.

3. The apparatus in accordance with claim 1,

c h a r a c t e r i z e d i n that the container (30) forms a vapour chamber (37) in which, in an upstream portion, a raw-fluid inlet (35) is arranged, and also a condensing chamber (371) in which a downstream portion contains the at least one condensing unit (321) .

4. The apparatus in accordance with claim 1,

c h a r a c t e r i z e d i n that the electric field (2) is provided by an electric DC voltage source (38) being connected to one or more of the container (30) , a centre electrode (31) and one or more of the condensing units (321) .

5. The apparatus in accordance with claim 4,

c h a r a c t e r i z e d i n that the electric DC voltage source (38) is a static generator.

6. The apparatus in accordance with claim 1,

c h a r a c t e r i z e d i n that the raw- fluid inlet (35) includes one or more dro -producing

injection nozzles (351) .

7. The apparatus in accordance with claim 1,

c h a r a c t e r i z e d i n that the condenser (3) includes a fluid barrier (312) which separates the upstream portion of the vapour chamber (37) from the downstream portion of the condensing chamber (371) .

8. The apparatus in accordance with claim 7,

c h a r a c t e r i z e d i n that a drop catcher (314) forms a boundary of the vapour chamber (37) towards one or more vapour ports (315) forming each a passage between the vapour chamber (37) and the

condensing chamber (371) .

9. A method of distilling fluid, in which a raw fluid is carried into a container (30) containing one or more condensing units (321) , c h a r a c t e r i z e d i n that the method includes the further steps of:

a) creating a non-uniform electric field (2) in the container (30) , concentrated in the direction towards the condensing unit(s) (321);

b) providing dipolar molecules (1) from the raw fluid;

c) concentrating the molecules (1) at the condensing unit(s) (321) by electrostatic force, as a net force great enough to move the molecules (1) towards the condensing unit(s) (321) is applied to each dipolar molecule (1) in the non-uniform field (2) .

10. The method in accordance with claim 8,

c h a r a c t e r i z e d i n that the method is practised by a negative pressure in the container (30) .

11. The method in accordance with claim 9,

c h a r a c t e r i z e d i n that the method

includes the further step of :

providing the electric field (2) by connecting an electric DC voltage source (38) to one or more of the container (30) , a centre electrode (31) and one or more of the condensing units (321) .

12. The method in accordance with claim 9,

c h a r a c t e r i z e d i n that the method

includes the further step of :

providing fluid particles in drop form in the vapour chamber (37) by injecting raw fluid through one or more injection nozzles (351) .

13. The method in accordance with claim 9,

c h a r a c t e r i z e d i n that the method

includes the further step of :

keeping the raw fluid and the condensate separated by means of a fluid barrier (312) which surrounds the vapour chamber (37) and is fluid-tight at least in a bottom portion (313) .

14. The method in accordance with claim 9,

c h a r a c t e r i z e d i n that the method

includes the further step of :

inhibiting the movement of fluid particles in drop form from the vapour chamber (37) into the

condensing chamber (371) by directing the fluid vapour through a drop catcher (314) arranged in a downstream portion of the vapour chamber (37) .

15. The method in accordance with claim 9,

c h a r a c t e r i z e d i n that the raw fluid is contaminated water or salt water.