EP1667798B1 - Assembly of an electrodynamic fractionating unit - Google Patents

Abstract

The fractionation plant has an electrical energy store coupled on the output side to 2 electrodes, respectively held at a reference potential and supplied with a pulsed HV under control of an output switch, the electrode ends held at a given relative within a reaction vessel containing a process fluid in which the process material is immersed, so that a reaction zone is provided between them. The electrical energy store, the electrodes and the electrode leads and the reaction vessel are fully enclosed by an electrically-conductive housing connected to earth, the wall thickness of the housing matched to the penetration depth corresponding to lowest component of the Fourier spectrum of the pulsed electromagnetic field.

Description

The invention relates to the construction of an electrodynamic fractionation plant (FRANKA = Fr action at position Ka rlsruhe) for fragmenting, grinding or suspending a brittle, mineral process material.

• Dem Energiespeicher, also der Einheit zur Erzeugung eines HV-Impulses, häufig oder meist der aus der Hochspannungsimpulstechnik bekannte Marx-Generator, und dem anwendungsspezifischen, mit einer Prozessflüssigkeit angefüllten Reaktions-/Prozessgefäß, in das der blank liegende Endbereich einer mit dem Energiespeicher verbundenen Hochspannungselektrode völlig eingetaucht ist. Ihr gegenüber befindet sich die Elektrode auf Bezugspotential, meist der als Erdelektrode fungierende Boden des Reaktionsgefäßes in zweckmäßiger Ausgestaltung. Erreicht die Amplitude des Hochspannungspulses an der Hochspannungselektrode einen ausreichend hohen Wert, so erfolgt ein elektrischer Überschlag von der Hochspannungs- zur Erdelektrode. Abhängig von den geometrischen Gegebenheiten und der Form, insbesondere der Anstiegszeit des Hochspannungsimpulses, erfolgt der Überschlag durch das zwischen den Elektroden positionierte, zu fragmentierende Material und ist damit hoch wirksam. Überschläge nur durch die Prozessflüssigkeit erzeugen allenfalls Schockwellen darin, die wenig wirksam sind.

All previously known systems which have been developed by means of powerful high-voltage discharges, in particular the electrodynamic method, for fragmentation, for removal, for drilling or for similar purposes for the processing of mineral materials, consist of the following two main components:

• The energy storage, so the unit for generating a high-voltage pulse, often or usually known from the high-voltage pulse Marx generator, and the application-specific, filled with a process liquid reaction / process vessel, in which the blank lying end of a connected to the energy storage high-voltage electrode completely immersed. Opposite the electrode is at reference potential, usually acting as the ground electrode bottom of the reaction vessel in an appropriate embodiment. If the amplitude of the high-voltage pulse at the high-voltage electrode reaches a sufficiently high value, an electrical flashover occurs from the high-voltage electrode to the earth electrode. Depending on the geometric conditions and the shape, in particular the rise time of the high-voltage pulse, the flashover occurs due to the material to be fragmented positioned between the electrodes and is thus highly effective. Flashovers only by the process liquid produce at most shockwaves in it, which are less effective.

The electrical circuit consists during the high voltage pulse from the energy storage C of the high voltage electrode connected thereto, the gap between the high voltage electrode and the bottom of the reaction vessel and the return line from the bottom of the vessel to the energy storage. This circuit includes the capacitive, ohmic and inductive components C, R and L, which influence the shape of the high-voltage pulse (see FIG. 6 ), ie, both the slew rate and the further time course of the discharge current and thus the pulse power coupled into the load and, as a result, the efficiency of the discharge with regard to the material fragmentation. In the ohmic resistance R of this temporarily existing circuit, the electrical energy amount Ri ^{2 is converted} into heat during the time of the discharge current pulse. This amount of energy is thus no longer available for the actual fractionation.

This circuit represents a conductor loop, which is traversed by a very short period of very large currents, about 2 - 5 kA. Such a structure generates intense electromagnetic radiation, thus represents a radio station high radiation power, and must be screened to avoid interference in the technical environment with technical effort. In general, such a system must be shielded by protective devices such that touching the live components during operation is not possible. This quickly leads to a comprehensive protection structure beyond the actual payload.

All known to date systems in which the electrodynamic process is used, have an open structure, ie the modules of such a system are connected by electrical lines together (see FIG. 6 ).

In the fragmentation of stony good, such as in the WO 96/26 010 described, connecting lines between the electrical energy storage and the spark gap can be seen, which form current-carrying loops during the HV pulse.
Equipment for the removal of material ( DE 197 36 027 C2 ), for drilling in rocky rock ( US 6,164,388 ) or for inerting ( DE 199 02 010 C2 ) show each simple electrical lines to the high voltage electrode.

The US 3,604,641 A discloses an electrodynamic fractionation with a rechargeable electric energy storage, at the output of two electrodes are connected, one of which is at a reference potential and the other via an output switch on the energy storage pulse-like high voltage can be acted upon, a reaction vessel, which is filled with a process fluid, in which the process material is immersed and in which the two blank lying electrode ends face, and the high voltage electrode is surrounded by an insulating jacket, wherein the energy storage including output switch, the electrodes, including leads and the reaction vessel are completely in an encapsulation, the electrode on reference potential on the capsule wall is connected to the ground side of the energy store and the high voltage electrode is connected in the shortest path to the output switch on the energy store.

The invention has for its object to build a FRANKA system in their circuit during the high voltage pulse so that both the inductance and the ohmic resistance of the discharge circuit remains limited to a minimum and at the same time the technical effort to shield against electromagnetic radiation and to ensure Touch safety is limited to a minimum effort.

The object is achieved by a structure of the fractionation according to the characterizing features of claim 1.

The energy storage together with its output switch, the latter usually usually operated in self-breakdown or triggered spark gap, the electrodes including the supply line and the reaction vessel are in compliance with the electrical isolation distance to areas of different electrical potential completely in a volume with electrically conductive wall, the encapsulation. The existing between the enclosure and the built-in modules volume is minimized and thus limits the inductance of the system to the unavoidable minimum. This consideration of electrophysics allows the typical shortest rise time for the discharge pulse.

On the one hand, the wall thickness is at least equal to the penetration depth of the lowest component of the Fourier spectrum of the pulsed electromagnetic field, thus being decisively influenced by it. On the other hand, the mechanical strength requires a minimum wall thickness. The necessarily larger wall thickness from one or the other of the two conditions is observed during construction.

In this complete encapsulation, the electrode is connected to reference potential via the capsule wall with the ground side of the energy store. The rest of the power supply via the energy storage and the components to be temporarily placed at high voltage potential is central to encapsulation.

This encapsulated construction allows for an electrophysically and operationally advantageous construction, the features of which are further specified in subclaims 2 to 9.

Depending on the mode according to claim 2, the capsule wall has a removable area for the batch (batch) operation or access for the continuous introduction (claim 3). For repairs, the capsule is anyway partially open.

According to claim 3, at least one outwardly directed tube-like nozzle made of conductive material for the feed and at least one other for the removal are attached to the capsule wall for the continuous processing of Fragmentiergut. Because of the electrical shielding to the outside these are dimensioned in length and clear width such that at least the high-frequency high-frequency components in the spectrum of the electromagnetic field generated by the high voltage pulse does not escape through these nozzles or in these nozzle to the opening in the environment at least on the legally required measure be weakened.

The energy storage and the reaction vessel are spatially separated in the enclosure. According to claim 4 sits in the one inner end wall region of the energy storage and in the other end wall region of the reaction vessel or is formed thereof.

The encapsulation is a closed tubular structure and has according to claim 5 has a polygonal or round cross-section. The encapsulation may be stretched but also angled at least once. The shape is determined constructively by the installation project. The simplest form is the stretched one.

Consequently, the electrode lying at reference potential is centered in the end wall of the reaction vessel and the high-voltage electrode is centered at a distance from (claim 6). The high voltage electrode is connected directly to the output switch of the energy storage. This output switch is in the case of a Marx generator as energy storage the output spark gap. This results in any form of encapsulation of the electrically favorable and isolation appropriate expedient coaxial structure, with which the requirement of the encapsulation and thus the system typical smallest inductance is met.

In the installation of the system is not limited according to claim 7. The electrical energy store together with the output switch sits in relation to the reaction vessel in the enclosure spatially above or at the same height or spatially below.

Depending on the nature of the fragment to be fragmented according to claim 8, the electrode reference potential, usually ground electrode, centric part of the forehead or sieve bottom or ring or rod electrode.

According to claim 9, the energy storage device is separated from the reaction vessel by a protective wall, so that the reaction space is separated liquid-tight from the region of the energy store.

The high voltage pulse between the high voltage electrode and the bottom of the reaction vessel, or the current from one to the other electrode converts the introduced electrical energy into different energy components of another kind, i.a. also in mechanical energy, in the end mechanical waves / shockwaves. The high-voltage electrode is sheathed electrically insulated in its jacket area up to the end area, projects completely into the process liquid with this end area.

The completely shielded outward structure of energy storage or pulse generator and process reactor in a common electric conductive housing has several advantages over the conventional, open manner of construction:

the inductance of the discharge circuit is reduced to the unavoidable minimum;
the ohmic losses in the high voltage pulse circuit are also limited to an unavoidable minimum;
minimum inductance and minimum ohmic resistance of the pulse circuit lead to a more efficient discharge in the load, ie to a greater energy input into this. With regard to the electromagnetic radiation as well as the contact safety, the somewhat closed construction of the system has decisive advantages. During the entire time of the HV pulse, the discharge current flows exclusively in the interior of the system. This is evident in any case for the outflow flowing to the bottom of the reaction vessel from the energy store, comprehensive pulse generator, via the high-voltage electrode and the load, reaction liquid with fractionating material, owing to the shielding function of the electrically conductive encapsulation.

The return flow from the bottom of the reaction vessel to the energy storage flows on the inner wall of the hollow cylindrical encapsulation, since the magnetic field built up by the discharge current flowing briefly in the system has the property of minimizing the area enclosed by the conductor loop. Due to the skin effect, this reverse current, which flows briefly on the inside of the plant wall, only penetrates into the wall material to a shallow depth, the frequency-dependent penetration depth. The penetration depth is known to be dependent on the electrical conductivity of the wall material and on the frequency spectrum occurring in the discharge current. With the usual rise times of the high-voltage pulses of about 500 ns, a characteristic natural oscillation period of the discharge circuit of about 0.5 μs and when using simple steels such as structural steel for the plant wall, the penetration depth into the inner wall is less than 1 mm. The wall thickness of the encapsulation on the one hand necessarily takes into account the lowest frequency of the Fourier spectrum from the electrical discharge because of the penetration depth (skin effect) and the necessary mechanical strength because of the shape retention of the system. The higher minimum requirement of wall thickness dominated for one of the two reasons. Thus, no electrical voltages can occur on the outer surface of the enclosure, thereby eliminating the protection against contact, or this can be limited in its construction to a minimum. An electromagnetic radiation to the outside can not occur either.

The coaxial system is compact, manageable and accessible in terms of measurement and control technology. The electric charger for the energy storage does not need to be specially screened. Its lead can be easily passed through bushings to the energy storage in the upper interior of the housing, possibly by a coaxial cable whose outer conductor contacts the housing.

• Figur 1 die koaxial aufgebaute FRANKA-Anlage,
• Figur 2 Skizze der FRANKA-Anlage mit Trennwand,
• Figur 3 Skizze der FRANKA-Anlage für kontinuierlichen Betrieb,
• Figur 4 Skizze der FRANKA-Anlage mit u-förmiger Kapselung,.
• Figur 5 Skizze der FRANKA-Anlage mit Reaktionsgefäß oben, Figur 6 die herkömmliche FRANKA-Anlage.

The complete, metallic encapsulated Fragmentieranlage will be explained in more detail below with reference to the drawing. Show it:

• FIG. 1 the coaxial FRANKA system,
• FIG. 2 Sketch of the FRANKA plant with partition,
• FIG. 3 Sketch of the FRANKA plant for continuous operation,
• FIG. 4 Sketch of the FRANKA plant with U-shaped encapsulation ,.
• FIG. 5 Sketch of the FRANKA plant with reaction vessel above, FIG. 6 the conventional FRANKA system.

In FIG. 1 the coaxial FRANKA system is shown schematically in axial section. The continuous or discontinuous operation is not respected here, here is the electrical structure in the foreground. Also, the electric charger for charging the electrical energy storage device 3 is not indicated. The coaxial structure is, electrically speaking, the most advantageous. A deviation from this would only be made of constructive constraints.

The high-voltage pulse generator consists of the electrical memory C, as a capacitor schematized, and the inductance L and the ohmic resistor R in series.
The high voltage electrode 5 connects. It is electrically insulated from its electrical connection at the resistor R forth to the end region by a dielectric jacket to the environment. It opens with its bare end region 4 in the direction indicated by a lightning symbol process / reaction volume and there has a predetermined, adjustable distance to the bottom of the process / reaction vessel 3, which forms the lower part of the coaxial, hollow cylindrical housing 6.

The current flow during the high voltage discharge takes place in the structural components along the axis of the hollow cylindrical housing 6, flows in at least one discharge channel in the process volume to the bottom of the reaction vessel 3 and then via the housing wall 6 back into the energy storage / capacitor 1. The housing 6 is connected to the reference potential "Earth" connected.

The inductance L and the resistance R are representative of the system inductance and the system resistance, C indicates the electrical capacity and thus the storage voltage available via the charging voltage,
1/2 C (nU) ² , which is to be converted to the largest possible extent in the process volume. In the case of a Marx generator as a HV pulse generator whose at least two-stage (n = 2), the individual capacity C and the step charge voltage U and the number of stages n for the storage energy is decisive.

FIG. 6 shows a FRANKA plant schematized in conventional construction, as it is simple for many laboratory work and is.

• Figur 2 zeigt, wie der Energiespeicher 1 durch eine Trennwand im Bereich der Hochspannungselektrode 5 vom Reaktorbereich 3 getrennt ist. Das ist insbesondere bei Auftreten von Spritzflüssigkeit durch den Entladungsvorgang einzubauen.
• Figur 3 zeigt zwei Öffnungen in der Kapselung 6, eine im Mantelbereich zum Einfüllen in das Reaktionsgefäß 3, die zweite aus dem Reaktionsgefäß 3 heraus beispielsweise durch den Boden. Durch diese bauliche Maßnahme kann ein kontinuierlicher Betrieb mit Beladung und Entnahme gefahren werden.
• Figur 4 zeigt die u-förmige Kapselung 3. Diese Bauform dürfte bei großen Anlage aufgrund der Gewichte und Handhabbarkeit Vorzug haben.
• Figur 5 skizziert eine auf den Kopf gestellte Bauform, das Reaktionsgefäß 3 sitzt über dem Energiespeicher 1. Bei gasförmigen oder sehr leichten, aufgewirbelten Prozesssubstanzen könnte sich eine solche Bauform anbieten.
• Figur 6 zeigt den Aufbau herkömmlicher FRANKA-Anlagen, die als voll funktionierende Anlage noch extra durch eine Wand zur Abschirmung und als Schutz gegen Berührung gekapselt ist. Die große elektrische Schleife ist nicht minimiert. Im Falle eines Pulses wirkt sie als starke Sendeantenne. Im industriellen Einsatz ist die Abschirmung aus diesem Grunde gesetzlich geregelt.

In the FIGS. 2 to 5 Coaxial variants of a FRANKA system are outlined:

• FIG. 2 shows how the energy storage device 1 is separated from the reactor region 3 by a partition wall in the region of the high-voltage electrode 5. This is especially to be installed when spraying liquid by the discharge process.
• FIG. 3 shows two openings in the enclosure 6, one in the shell region for insertion into the reaction vessel 3, the second out of the reaction vessel 3, for example through the bottom. By this structural measure a continuous operation with loading and unloading can be driven.
• FIG. 4 shows the U-shaped encapsulation 3. This design should be preferred for large plant due to the weights and handling.
• FIG. 5 sketched an upside down design, the reaction vessel 3 sits above the energy storage 1. With gaseous or very light, fluidized process substances could offer such a design.
• FIG. 6 shows the structure of conventional FRANKA systems, which is fully encapsulated as a fully functional system even by a wall for shielding and protection against contact. The big electrical loop is not minimized. In the case of a pulse, it acts as a strong transmitting antenna. In industrial use, the shield is therefore regulated by law.

LIST OF REFERENCE NUMBERS

1.

energy storage

Second

Output switch / -funkenstrecke

Third

reaction vessel

4th

Forehead of the high voltage electrode

5th

High voltage electrode with insulator

6th

encapsulation

7th

Connection process vessel - encapsulation

8th.

Connection charger - encapsulation

9th

filler pipe

10th

discharge pipe

Claims (9)

1. Assembly of an electrodynamic fractionating unit for the fragmenting , grinding or suspending of a brittle material to be processed, said unit comprising:

   a chargeable electrical energy store (1), two electrodes being connected to the output of said energy store, one of which being at reference potential and the other being impingable upon with high-voltage in a pulse-like manner via an output switch (2) at the energy store,

   a reaction vessel (3) which is filled with a process fluid, into which the material to be processed is immersed and in which the two exposed electrode ends are situated opposite each other at an adjustable distance,

   the reaction zone, wherein the electrode (4) that is impingable with high-voltage is surrounded by an insulating casing (5) as far as the free end region and said insulating casing in the end region is also immersed into the process fluid,

   the energy store together with its output switch, the electrodes together with supply line and the reaction vessel are situated totally in one volume, the enclosure (6),

   the electrode at reference potential (4) is connected to the earth side (8) of the energy store via the enclosure (6),

   the electrode impinged upon with high-voltage is connected over the shortest path to the output switch at the energy store,

   characterized in that:

   in operation the enclosure (6) is electrically conducting and the volume surrounded by the enclosure is minimal, in that consequently the inductance and the ohmic resistance of the unit is restricted to the unavoidable minimum,

   the wall thickness of the enclosure (6) is at least equal to the depth of penetration that corresponds to the lowest component of the Fourier spectrum of the pulsed electromagnetic field and has at least the thickness required for the mechanical strength.
2. Assembly according to Claim 1, characterized in that the enclosure wall is partially removable or there is at least one access in the enclosure wall for the batch-type processing of the fragmentation product.
3. Assembly according to 1, characterized in that at least one tubular connecting pipe (9) directed towards the outside and produced from conducting material for the charging process and at least one additional connecting pipe (10) for the removal process are attached to the enclosure wall for the continuous processing of fragmentation product, said connecting pipes being dimensioned in length and clear width in such a manner that at least the high-power, high-frequency proportions in the spectrum of the electromagnetic field generated by the high-voltage pulse do not escape through these connecting pipes or are weakened at least to the statutorily prescribed level in these connecting pipes before they reach the opening into the environment.
4. Assembly according to Claims 2 and 3, characterized in that the enclosure wall is a hollow body, the energy store being located in one inner end wall region of said hollow body and the reaction vessel being formed by the other end wall region of said hollow body.
5. Assembly according to 4, characterized in that the enclosure is polygonal or round in cross section and has an elongated form or a form that is angled at least once.
6. Assembly according to 5, characterized in that the electrode at reference potential sits in a centred manner in the end wall of the reaction vessel, the high-voltage electrode is situated opposite in a centred manner and said high-voltage electrode is connected to the output switch of the energy store on the path that is coaxial to the enclosure.
7. Assembly according to Claim 6, characterized in that the electric energy store together with output switch is situated in the enclosure spatially above or at the identical level or spatially below with reference to the reaction vessel.
8. Assembly according to Claim 7, characterized in that the electrode at reference potential is realized as a central part of the end face or as a sieve bottom or as an annular electrode or stick electrode.
9. Assembly according to one of Claims 1 to 8, characterized in that the energy store is separated from the reaction vessel by a protective wall.

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