DD225350A5 - METHOD AND DEVICE FOR LARGE-FLOATING DISTRIBUTION AND DISTRIBUTION OF ELECTRICALLY CONDUCTIVE FLUIDS - Google Patents

Abstract

1. Process for the large-area application and distribution of electrically conductive liquids having a specific resistance of < 10**4 OMEGA . m, in which a high voltage is applied to the liquid, characterised in that the liquid is allowed to issue from a nozzle or capillary at such a low rate of flow that, immediately downstream of the nozzle or capillary, it forms a cohesive filament of liquid which then disintegrates into individual drops and in that, by means of the high voltage relative to earth which is applied to the filament of liquid, the drop size is stabilised and a conical distribution of drops (cone of drops) is produced whose apex angle depends on the level of the voltage.

Description

63 992/17

Method and device for large-area deployment and distribution of electrically conductive liquids

Field of application of the invention

The invention relates to a method and a device for dispensing and distributing electrically conductive liquids having a specific resistance Z 10 · 2 · m, in particular of aqueous pesticide solutions.

Characteristic of the known technical solutions

The spraying of liquids, in particular of solutions or dispersions under the action of electric fields, is known from various fields of technology. Examples include the coating with paints in the automotive industry and the large-scale application of pesticides in agriculture. Plant protection products are sprayed in a known manner as dispersions in water in F _o rm of suspensions or emulsions using nozzles or rotary atomizers on the plant stands to be treated and deposited with more or less good success on the leaves of the plants, mainly on the top of the freestanding leaves ,

However, in order for the pesticides to be optimally effective, it is necessary that the underside of the leaves and the stems are also hit by the sprayed preparation. When spraying outdoors often a portion of the spray is driven off by the wind and carried to other plants that should not be treated. Furthermore, a large part is due to sinking to the earth

lost ground or by drift. For this reason, a method has been specified in which the dissolved preparation is electrostatically atomized at a high-voltage-carrying electrode, wherein the resulting, very fine aerosol droplets are unipolar highly charged. With this method, the liquid can be deposited more effectively on earthed objects, since the plants attract the charged droplets as a counter electrode to the sputtering electrode. However, the method has the disadvantage that only organic liquids whose specific electrical resistance is in a certain range (approx ·2 · m to 10 · m), can be electrostatically atomized and separated. In particular, aqueous solutions can not be processed because of the too high surface tension and because of the too low specific resistance (_f '~ = 5.7 $ ί · m).

Another disadvantage is that the highly charged, very fine droplets are deposited, especially in dense plant stands only on the outer parts of the plants, but not penetrate into the electrically shielded inner parts of the stocks. Furthermore, the charging height of the drops can not be controlled in a simple manner, since only a high charge of the liquid at the edge of the spray electrode initiates the atomization effect. In reducing the electrode voltage, only the sputtering process goes into dripping of the liquid.

Practical experience in the application of pesticides results in the following requirements:

1. Aqueous, non-combustible formulations are preferable to organic liquids.

2. Drop sizes should be in the range of 100 - 250 / um.

3. The penetration depth of the liquid drops in the plant population should be adjustable. The term "penetration depth" is understood here to mean the area which, viewed from above, is detected during the spraying process, ie from the tip of the plant. The penetration depth could z. B. be varied by changing the drop size or by changing the drop charge. Heavy, uncharged drops fall by the shortest route to the ground. In contrast, lightweight, highly charged droplets are deflected the most out of the trajectory of the free fall and by the most prominent ^T plant rush tightened. Both extreme cases are undesirable.

Object of the invention

The aim of the invention is a method which allows the targeted adjustment of the ratio of head loading to drop mass, since in this way the zones between the uppermost and the lower layers of the stocks can be detected.

Explanation of the essence of the invention

The object of the invention is to devise a process for the large-area distribution of aqueous liquids and the apparatus required for this purpose, the above-mentioned conditions being met.

This object is achieved erfindungsgeinäß characterized in that the liquid with such a small flow

speed out of a nozzle or capillary that it forms a continuous liquid thread immediately behind the nozzle or capillary, which then decomposes into individual drops and that stabilized by applying an electrical voltage to the liquid thread, at least 500 V to earth, the drop size and a spray or rain cone is generated whose opening angle depends on the height of the voltage.

Preferably, the flow rate, taking into account the dimensions of the nozzle or the capillary on the operating pressure so that the length of the continuous liquid thread behind the outlet opening 2 to 100 mm, preferably 5-20 mm, is. Practically, this is achieved for a few millimeters long capillary at a liquid pressure of 0.1 to 10 bar, preferably 1 to 3 bar.

Eg it has been found that one can control the Sindringtiefe of the droplets in dense plant populations by changing the fluid pressure.

The device for carrying out the spraying process is characterized by a multiplicity of flow-connected nozzle elements which consist of capillaries, wherein each of the capillaries is surrounded by a concentric protective sheath which is at the same electric potential as the capillaries, and by a high-voltage generator, whose high-voltage side output is conductively connected to the liquid flowing through the capillaries. The protective sheath is closed on one side by a bottom plate and forms a ^ bottom, the bottom of which is broken by the capillary.

The liquid to be distributed is supplied by a reservoir connected to the capillary. The spray point, d. H. the end of the capillary is inside the pot. The necessary to maintain the flow form is generated by a pump that holds the reservoir to positive pressure.

The inside diameter of the capillaries is suitably in the range of 50 to 500 μm. The nozzle elements are interchangeably inserted in a carrier and each nozzle element is surrounded by a ring of elastic material which is fastened on one side to the carrier and on the opposite side Side has a bore through which the provided with a collar projecting collar protective jacket is passed.

The entire device can be built to save space. In particular, a portable sprayer can be realized, which operates on this principle. D _emen -fc _S p _recn end there is a further development of the invention in that a support is provided, on which the nozzle elements are arranged and the carrier is attached to a rod-shaped holder having a battery-powered high voltage generator, an air pump for generating the form to the Capillaries and a reservoir for the liquid to be distributed.

The invention achieves the following advantages:

a) It has been found that with the new method aqueous solutions, as well as salt solutions and aqueous suspensions and emulsions spray easily and precipitate on target objects. As is known, such liquids can not be atomized by purely electrostatic means.

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b) The drop charge or charge / mass ratio of the drops is determined by the magnitude of the applied voltage and can be adjusted within wide limits. This results in the possibility - to control the spray characteristic of the electrical voltage. This advantage, which is of great importance for the application of crop protection formulations, can likewise not be achieved in the known purely electrostatic processes for the atomization of liquids.

c) Another advantage is that only relatively low liquid pressures are required. The necessary pre-pressure can be generated by means of pumps of simple design.

d) The inventive method can be realized with little equipment. In particular, the device can be constructed so compact and space-saving that now portable, easy-to-use sprayers for aqueous pesticide formulations are available.

e) Because in the "^" learn emerge relatively large droplets with a tight t _r opfengrößenspektrum, v / Ground harmful aerosols or, Fog (persons inhalation hazard) avoided.

Ausführungsbeiapiel

The invention will be described in more detail below with reference to embodiments and drawings, wherein the principle and the basic physical conditions of the new method will be explained in more detail below. Show it:

Pig. 1: the disintegration of a liquid thread in drops after exiting a capillary;

Pig. 2: the generation of a rain cone by applying an electrical voltage to the liquid thread;

Pig. 3a, b: the control of the Sindringtiefe the rain cone in the treatment of plant stocks;

Pig. 4a, b: the control of the Sindringtiefe the rain cone by changing the direction;

Pig. 5a, b: a possibility for increasing the space charge density at the destination by a plurality of directional rain cones;

Pig. β: schematically a complete portable distribution device;

Pig. 7: the at the Vorrichtlag according to Pig. 6 used carriers with nozzle elements and

Pig. 8: a single nozzle element.

As is known, a Wasaerstrahl emerging at a low speed from a simple perforated nozzle or capillary disintegrates in a defined manner in T _rO pfen certain size, The still coherent at the exit point smooth jet part or Plüssigkeitsfaden shows after a short initial path periodically recurring restrictions, which become increasingly large From the outlet opening deepen until it finally comes to the separation of individual drops whose diameter is directly related to the diameter of the contiguous beam part.

This process is shown in FIG. From the capillary with a diameter of 100 μm, a liquid jet 2 (ζ, for example water) with a velocity V = 6 m / sec. ejected, the shape of which initially remains cylindrical over a distance of a few cm in length, but then shows constrictions 3 at the surface, which repeat themselves at equal intervals and thereby deepen, until finally individual drops 4 "detach from the beam.

The lower range limit for the velocity of the outflowing liquid is reached when at the outlet opening no coherent liquid thread more forms, but drips the liquid. The upper limit for the exit velocity of the liquid is given when the laminar flow turns turbulent and the decay into droplets of equal size is replaced by a sputtering process, whereby a broad scattering of droplet sizes occurs. The disintegration of a liquid filament into droplets described herein is described as "natural jet decay".

The diameter d of the drops 4 in natural jet decay can be determined from the Strahldurchmesaer D and the distance of the constrictions bzv /. calculate the decay wavelength A. according to the following formula:

d = r 1.5 D ² Λ. = 1.89 D.

In practice, Λ = 4.5 D can be set for the wavelength. In addition to the T _rO pfen 4 with the constructed to be determined diameter d is additionally formed with a very small volume fraction of secondary S _a tellitentröpfchen 5, the diameter d z. B, where d = 0.2 d. Tracked

the drops thus produced on their trajectory, z. B. over the plug distance of 1 m, it is found that a large part of the drops is converted by recombination into larger drops 6 and 7. Instead of the expected droplet sizes d = 198 / μm, droplets whose size is in the range from 190 to SOO / μm, ie. H. far outside the desired range. The process of recombination of the drops on the flight path can be detected photographically.

Surprisingly, it has been found that it is possible to prevent the recombination to larger drops when an electrical voltage to earth is applied to the continuous part of the electrically conductive liquid thread. The drops are then preserved in their original size and reach the catcher unchanged, even if it is far away. In addition, a wide open cone (rain cone) of electrically charged droplets, which can be selectively deposited on earthed objects. This process is shown in FIG. The flow conditions are the same as in the jet disintegration of FIG. 1, but with a voltage of 10 kV against 3 rde, which is applied to the continuous liquid thread 2. The capillary is au3 electrically conductive material, eg. B. metal, and has a ratio of length to diameter of about 50: 1. The liquid pressure at the capillary is set to values of 0.1 to 10 bar, preferably in the range of 1 to 3 bar. Under these conditions, a continuous liquid thread with a length of 2 to 100 mm, preferably 5 to 20 mm results at the capillary. Instead of capillaries, it is also possible to use simple perforated nozzles whose jet diameter ranges from 50 μm to 500 μm, preferably in the case of jet generation

between 100 / um and 200 / um. The ratio between the length and width of the hole nozzle is z. B, 3: 1 ·

The high voltage in the range of 10 to 50 kV, which is supplied by the high-voltage device 8, is applied via the capillary 1 to the continuous liquid thread 2. Due to the voltage and the electric field caused thereby, a high-density electrical charge is induced on the surface of the conductive liquid thread, with the highest density of surface charge occurring at the end of the liquid thread, approximately at point 9. The detaching threads 4 and 5 take over part of this surface charge. An essential role is played by the fact that it is a conductive liquid whose specific resistance is <10 .Q, .m. Down the resistance is no limit. The liquid can be readily conductive.

In contrast to the trajectory of the uncharged droplets in the first section according to FIG. 1, which deviates only slightly from the original beam direction, the electrically charged droplets according to FIG. 2 show clearly divergent trajectories. The light satellite drops 5 leave the main trajectory immediately after formation and then move towards the next grounded body in the environment. The normal drops formed from the bulk of the effluent liquid later disengage and increase their mutual distance. This results in the formation of the above-mentioned rain cone 10 with the opening angle OL% ^ the drops remain even over routes of 1 m length and more in their original size. The effect of the electric field is thus based on two effects,

namely the prevention of recombination into larger drops and the formation of a cone due to the electrostatic repulsion, the change in the polarity of the charge has no effect on these effects. Depending on the height of the discharge velocity at the capillary (liquid pressure) possible in the permitted range, the jet thickness and the electrical voltage, the opening angle of the rain cone can be set small or large. This gives the possibility for a targeted separation of the droplets. By setting the Richtimg example, a plant stock can be sprayed either flat, the charged droplets preferably reach the upper parts of plants, or it is steeply sprayed; then the droplets are first deposited in the deeper parts of the stock. The penetration depth of the droplets can therefore be adapted to the respective requirements of the plant stands.

In Pig. 3a, b it is shown how the penetration depth of the droplets into dense plant stands can be controlled by changing the liquid pressure in the nozzle and the associated transporting speed. In the partial image a, water is ejected from a nozzle 9 with the clear width d = 100 / μm at a pressure of P ₁ = 0.6 bar with a mean discharge velocity V ₁ = 5.6 m / s. The beam is at a voltage of -15 kV, which is maintained by the high voltage device 10. Below the nozzle are two plants 11 and 12 of a larger plant population. The height of the plants is 0.5 m. The distance from the plant tip to the nozzle is 0.3 m. The rain cone 13 opens above the plants 11 and 12. At the low kinetic energy of the liquid thread, the drops are rapidly braked by the air friction and by Coulomb's forces in the water

The upper parts of plants 11 and 12 are quantitatively precipitated. In the sub-picture b is for the same voltage, but with the pressure of 3 bar and the exit velocity Vp = s 16.8 m / s is sprayed out of the nozzle 14, ^T he effective deceleration of the drop motion only occurs in the lower part of the plants 15 and 16 according to which the electrostatic forces of attraction predominate and cause the drops to deposit in this area. The cone 17 is less widely opened than the cone 13. In both cases (a and b), the droplet size and the charge remain almost the same, so that the tendency for selective deposition after the deceleration of the falling speed is maintained.

According to Fig. 4a, the nozzle or the capillary 18 is arranged above the plant population 19 so that the exiting Plüs3igkeitsfaden initially runs horizontally. The high voltage generator is omitted here. The generated rain cone 20 is decelerated by the air resistance and then settles at a lower speed in the upper parts of the plants of the stock 19, so that only a small penetration depth is achieved. According to Pig. 4b, the beam direction is rotated 90 ° to the first position; d. H. the capillary 21 is arranged vertically here. The high voltage source is, as in Pig. 4a, not shown. The rain cone falls from the capillary 21 into the plant stock 22 at a higher speed than in the arrangement according to Pig. 4a, since gravity acts in the same direction. This results in a larger Sindringtiefe. The precipitate is then preferably in the lower parts of the individual plants. It is clear that with other positions of the nozzles between these two extreme positions 18 and 21, the penetration depth can vary as desired. So you have it in hand, the penetration depth of the rain cone into dense plant

To control states by changing the ejection direction of the liquid. Moving a series of such nozzles parallel to the ground over a field (drawn arrows), so large plantings can be sprayed.

By simultaneously using a plurality of nozzle elements, the space charge generated by the drops can be concentrated in the immediate vicinity of the target object. Thus, according to Fig. 5a by a plurality of parallel oriented nozzles 25, a space charge cloud 23 with high. Charge density built up in front of the target object 24. Fig. 5b shows another way to build up a high space charge density by means of a plurality of nozzles 26. The nozzles are here oriented so that the extension of the liquid filaments, d. h "cross the initial directions of the rays at the location of the space charge 27, whereby a strong precipitation field at the target object 28 is formed. The nozzles are placed here at a greater distance from each other and the beam directions concentrated in one point of the room.

Fig. 6 shows a complete liquid distribution device, which is so compact and handy that it can be operated as a portable device by one person. It consists of a head 29, the liquid filter 30, the liquid valve 31, the reservoir 32 for the liquid to be distributed, a high voltage generator 33, a battery housing 34 and an air pump 35. All parts are taken up by a rod-shaped holder 36 made of insulating material , The grounding of the electrical system is provided by a grounding cable 37, the free end of which lies on the ground or is in electrical connection with the object to be treated.

In order to put the device into operation, one pumps with the air

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Pump 35 air into the container 32, which is partially filled with the liquid. In this case, "a part of the volume remains free, for example, 30% for the compressed air (air cushion) .The pressure in this volume is increased to 2 to 3 bar, whereby the valve 38 prevents the liquid from flowing back Switching on the high voltage generator 33 via the switch 39, which closes the primary circuit, set under high voltage of, for example, 50 kV When opening the valve 31, the liquid flows through the distributor head 29 and is applied over a large area in the manner indicated above.

The distributor head 29 is shown in FIG. In principle, it consists of a plurality of fluidically parallel nozzle elements which are connected via the line 44 to the liquid container 32. For generating thin liquid jets are very good short capillary tubes, but very sensitive to contamination and damage in direct contact with other objects, such. As plants are. For this reason, the capillary is protected by a concentric jacket here. Although the formation of an electric field is suppressed by the shielding effect of the jacket at the same potential of the protective mantle, there is no impairment of the spraying process. The contiguous first section of the liquid thread, which projects beyond the edge of the protective jacket, namely because of the conductivity of the liquid is the substitute for a tip electrode, at the outside of the cylinder, the field that is required for the charging of the drops.

According to Fig, 7, the capillary 47 is inserted into the bottom plate of a pot 48 and thus forms a nozzle member 40, the

is pressed into corresponding holes of the distributor head 29. Airch the protruding edge 42 (collar of the pot 48), the immersion depth is limited. The free end of the capillaries 47 immersed in the Plüssigkeitskanal 43, which in turn is connected to the supply pipe 44.

Since the capillaries 47 can easily become contaminated during prolonged use by deposits (incrustations), a device for the simple rapid change of the nozzle elements 40 is required. For this purpose, each nozzle element 40 is surrounded by a ring ^ 5 of elastic material whose circumference is greater than the circumference of the support 41 for the Düsenelemeiite. The ring 46 is pierced at its top (Pig · 7) and bolted to the carrier 41 at the opposite side (46). Through the hole in the elastic ring, the nozzle member 40 is now inserted into the carrier 41 such that the collar 42 of the pot 48 protrudes beyond the bore and thus forms a stop (see ^ Pig. 8). To replace a Düaenelementes 40 one prints the ring 45 together (arrows Pig. 8). As a result, the ring 45 is deformed and exerts on the nozzle member a force which is large enough to pull it out of the anchorage in the carrier 41. Subsequently, a new nozzle element can be inserted through the bore in the ring 45 and inserted into the corresponding opening of the carrier 41. The replacement can be done by hand without the use of tools.

The diameter of the elastic ring 45 is 5 to 50 mm, preferably 10 to 30 mm. The length of the carrier as well as the packing density of the nozzle members 40 can be adapted to the needs. The latter is limited only by the mutual contact of the components.

There is a maximum for the magnitude of the electric charge of the drops, which is reached when the electric field strength in the vicinity of the jet approaches assumes a value above which a corona discharge begins. The height of the optimum operating voltage depends on the dimensions of the apparatus. It must therefore be determined experimentally. For a single nozzle element with 100yum capillary width and far away counter electrode (at least 0.5 m), the optimum operating voltage is about 10 kV. The upper limit for the operating voltage is approx. 50 kV.

A major advantage of the device described, compared with known devices for generating electrically charged spray, is that in the immediate vicinity of the high-voltage nozzle unit no counter electrode is required with ground potential. This circumstance allows the use of very long Isolierstrecken between the live parts of the arrangement, malfunction due to humid air or contamination of the insulators can thus be largely excluded. Furthermore, it is important that only very small currents flow (order of magnitude / UA), so that the battery used for the power supply has a long life and the high voltage generator can have a high internal resistance. In this way, a danger to people by high voltage is avoided.

Claims (9)

invention claim 1. A method for large-scale spreading and distribution of electrically conductive liquids having a resistivity of <10 g, in particular of aqueous pesticide solutions or dispersions, characterized in that it is possible to leak the liquid at such a low flow rate from a nozzle or capillary in that it forms a coherent liquid thread immediately behind the nozzle or capillary, which subsequently breaks up into individual drops and that the drop size is stabilized by applying an electrical voltage to the liquid thread, at least 500 V to earth, and a conical droplet distribution (rain cone) is produced whose opening angle depends on the height of the voltage. 2. The method according to item 1, characterized in that the flow rate due to the dimensioning of the nozzle or capillary and the selected operating pressure is adjusted so that the length of the continuous liquid thread behind the outlet opening 2 to 100 mm, preferably 5 to 20 mm. 3. The method according to item 1 to 2, characterized in that the liquid pressure of the nozzle or capillary to V / erte of 0.1 to 10 bar, preferably 1 to 3 bar, is set. 4. The method according to item 3, characterized in that the penetration depth of the rain cone is controlled in dense plant stands by changing the fluid pressure. 5 «Device for carrying out the method according to the points 1 to 4, characterized by a plurality of flow-parallel-connected nozzle elements (40) consisting of capillaries (47), each capillary (47) by a concentric protective jacket (48) is surrounded which is at the same electrical potential as the capillaries (47) and by a high voltage generator whose high voltage side output is connected to the fluid flowing through the capillaries (47). 6. The device according to item 5, characterized in that the protective jacket is closed on one side by a bottom plate and forms a pot, the bottom of which is broken by the capillary (47) which is connected on the one hand with a reservoir (32) for the liquid and on the other inside the pot ends. 7. Device according to items 5 to 6, characterized in that the inside diameter of the capillaries (47) is in the range of 50 to 500 / um, 8. The device according to item 5 to 7, characterized in that the nozzle elements (40) are exchangeably inserted in a carrier (41) and each nozzle element (40) of a% ng (45) of elastic material is looped around, on the one Side is fixed to the support (41) and on the opposite side has a bore through which the with a bore projecting collar (42) provided protective jacket (48) is passed. 9. Device according to item 5 to 8, characterized in that the carrier (41) with the nozzle elements (40) a rod-shaped holder (36) is mounted, which includes a battery-powered high voltage generator (33), an air pump (35) for generating the pre-pressure at the capillaries (47 and a reservoir (32) for the liquid to be distributed. - 4 pages drawings -