EP1673172B1 - Processing reactor and operational method for electrodynamic fragmentation - Google Patents

Abstract

In a process reactor and a method for the electro-dynamic fragmentation of lumpy mineral materials by pulsed high voltage discharges, including a reaction chamber with a funnel-like bottom having a central outlet, an axially movable high-voltage electrode extending from the top into the reaction chamber and having a front end disposed opposite the central outlet where another electrode which is at an electric reference potential is disposed, the outlet converges into a tailback tube below which a transport unit for the controlled removal of the processed fragmented material sinking down through the tailback tube is disposed, a material supply arrangement extends to an opening in the wall of the reaction chamber and a material flow blocking structure is disposed in the reaction in front of the material inlet opening for controlling the material admission to, and the fill level in, the reaction chamber.

Description

The invention relates to a process reactor for the electrodynamic fragmentation of particulate mineral materials immersed in a process fluid by means of pulsed high-voltage discharges and a method for operating the process reactor.

• einem geschlossenen Reaktionsbehälter mit trichterförmigem Boden und zentralem Auslass darin. Eine mit Hochspannung beaufschlagbare Elektrode, die Hochspannungselektrode, ragt von oben in diesen hinein. Diese Elektrode ist bis auf ihren frei stehenden Endbereich mit einer elektrischen Isolation ummantelt. Die Hochspannungselektrode ist entlang ihrer Achse verschiebbar, so dass das Ende derselben dem Auslass, dessen metallische Umrandung die andere, auf elektrischem Bezugspotential befindliche Gegenelektrode repräsentiert, am trichterförmigen Boden des Reaktionsbehälters zentral gegenübersteht. Material wird über eine Öffnung in der Wand des Reaktionsbehälters zur Fraktionierung kontinuierlich oder schubweise zugeführt.

In its basic structure, such a process reactor consists of:

• a closed reaction vessel with funnel-shaped bottom and central outlet therein. An electrode which can be subjected to high voltage, the high-voltage electrode, projects from above into this. This electrode is sheathed with an electrical insulation except for its free end area. The high-voltage electrode is displaceable along its axis, so that the end of the same, the outlet whose metallic border represents the other, located on electrical reference potential counter electrode, centrally facing the funnel-shaped bottom of the reaction vessel. Material is supplied via an opening in the wall of the reaction vessel for fractionation continuously or batchwise.

The overwhelming majority of fragmentation plants which have become known hitherto operate in overrun mode, also called batch mode in technical usage, ie a small amount in the range of a few kilograms of the material to be treated is usually introduced by hand into the process space and above the ground electrode, usually a sieve bottom , deposited and fragmented by means of high voltage discharges. When the desired number of discharges has been reached, the sieve passage and, if present, the sieve support are discharged separately. Typical representative of this mode of operation is the Franka 0 system DE19534232 C2 (Figures 5, 6) or similar systems, which are described for example in the publication [1].

For industrially relevant mass flow rates, this batch mode is not particularly suitable. The device specified in [2] is for continuous filling, but is u.a. because of the sieve used not suitable for larger mass flow rates.

In the US Pat. No. 6,039,274 (Fig. 1) is also given a continuous flow of material in the context of a screen or vibrating screen, however, is unresolved: the throughput, the treatment time and Sieblebensdauer.

The in the DE 197 27 534 C2 and GB 1 284 426 Patented, continuously operating processes are based on the use of the electrohydraulic principle, ie only the action of the shock waves as a result of HV discharge under water. In general, it can be said that a major weakness of all screens with sieve tray in the process vessel is that apart from the relatively small possible mass flow rates, the largest aggregate component that allows escape from the process area is always smaller than the mesh size of the sieve. In practice, the conditions are even more unfavorable: if a surcharge component is dissolved out of the material and is not necessarily above a hole of the bottom sieve, but reaches there only in the course of some further discharges, it may experience one or more fragmentation / s. This effect is always undesirable if, in addition to the fundamental requirement for comminution of a material, the preservation of the size of certain components in a heterogeneous material also plays an important role. As an example, the treatment of concrete is mentioned, in which working on a sieve electrode inevitably leads to an undesirable shift of the grading curve of the original aggregate material to smaller fractions. Direct mixing of new concrete on the basis of this recycled material is therefore excluded. If this sliver shift or the unwanted grinding process to be avoided, so must a sieve with Larger number of holes and larger hole diameter can be used. However, this has the consequence that with a larger number of holes, the probability of breakage of the screen increases and that escape through the larger holes not only the aggregate components in the desired original size, but also smaller aggregate components with residual adhesions of the cement matrix and matrix conglomerates. This, in turn, contradicts the requirement for the most complete possible separation of the components.

Sieves also have the serious disadvantage of an inevitable tendency to clogging due to debris in the concrete debris, such as nails and Armierungsreste that affect the functioning of a technical system.

The object of the invention is to provide a process reactor for a preferably continuous and efficient electrodynamic fragmentation of brittle, particulate, mineral materials for industrially relevant mass flow rates.

The object is achieved by a process reactor according to the characterizing features of claim 1 and by a method according to the method steps of claim 11.

The outlet at the funnel-shaped bottom opens into a pitot tube, below which there is a transport unit for the removal of material, which removes the processed fragmented material that sank through the pitot tube. In the opening of the wall of the reaction vessel ends a material supply device, is introduced with the fraction to be fractionated material in the reaction vessel. In the reaction vessel in front of the material inlet sits a stowage device, which regulates the material flow and the level height in the reaction chamber or with which the material flow is regulated.

According to claim 11, the average residence time T _{M of} the material in the reaction zone by the speed of the material throughput determines the pitot tube below the reaction zone. This speed is determined by the outlet area A _u at the Staurohrausgang, the adjustable distance a between the lower opening of the pitot tube and the transport / material extraction unit and their speed v ₀ . The combination of these parameters results in the delivery rate dV / dt. The length 1 of the pitot tube is chosen so that when fragmenting a stable angle of repose of the struck on the transport unit, fragmented Guts formed. Finally, the degree of fragmentation of the processed material is set via the average number of high-voltage pulses n acting on the quantity m of the material in the reaction zone and the delivery rate dV / dt and the amount of energy introduced into the material per high-voltage pulse and the pulse repetition frequency f of the high-voltage pulses ,

In the dependent claims 2 to 9 features are described with which specific components of the device can be constructed.

According to claim 2 of the central outlet at the funnel-shaped bottom is a metallic Pitot tube with the upper clear entrance surface A _o, the outlet, the lower clearance exit area A _u and the area relationship A _o <A _u. This outlet has a conical edge and fits flush and smooth into the conical part of the funnel-shaped bottom. The metallic border of the outlet forms the counter electrode in the two-electrode system of the process reactor and is connected to a reference potential, usually ground potential.

In the case of the circular cross section and thus vertically seated pitot tube, the diameter and cross section are related by A = πd ^2/4 . In general, the pitot tube can have a round or polygonal cross-section and lead away from the reactor vertically or obliquely. On the funnel-shaped bottom sits the metallic wall of the reaction vessel, it is placed on the same reference potential as the pitot tube.

The pitot tube opens vertically or obliquely into a discharge channel, and is at an adjustable distance a above the transport unit for material removal.

In the opening of the wall of the reaction vessel opens a material supply device, is introduced with the fragment to be fragmented in the reaction vessel.

A stowage device is located in or protrudes into the reaction vessel, which regulates the level or the material flow.

The high-voltage electrode is, as described in claim 3, from electrically good conductive, low-burning metal. According to claim 4, it can therefore be solid cylindrical or tubular so hollow cylindrical with each round or polygonal cross-section.

The central diameter d _{e end of} the conical widening on the outlet tube faces parallel with the circumferentially constant width g to form a conically annular gap between the high voltage electrode and the reference potential electrode, thus forming the conically annular reaction zone for fragmentation.

The material supply device according to claim 5, for example, a known from the conveyor vibrator or a conveyor belt. The stowage device in the reaction vessel is according to claim 6, for example, a guided on the wall of the reaction vessel, height adjustable baffle, which touches in the closed position with its bottom edge of the reaction vessel or seated there. On the other hand, the stowage device according to claim 7 may be a horizontally or helically circulating group of at least one channel along the bottom line of which there are holes at each of which attaches a tube with at least the clear width of the hole diameter, thus not jamming by falling Good can. The tubes lead down near the reactor wall and open into the actual reaction volume.

As a transport unit is for example in question:

A baffle plate according to claim 8, on which the piled-up, fractionated material is turned away and, for example, deflected downwards via a separating board, or likewise a conveyor belt according to claim 9.

The beginning of the discharge channels at the two electrodes is crucial for the reliable long-term operation of the fragmentation system. At the exit surfaces they should begin in a designated area, so that the electrode erosion is not locally stuck, but occurs statistically evenly distributed with each discharge. Two surface states can contribute according to claim 10, namely the annular forehead of the high voltage electrode is smooth or rough designed in the intended start region of the discharge channels on their surface, that statistically uniform distribution local elevations of the electric field come about through the shaping.

In electrodynamic fragmentation, pulsed high-voltage discharges are used. The electrical discharge is in this regime, at least predominantly by the property to be fragmented and not around it only by the process liquid.

• kontinuierliche und kontrollierte Zu- und Abfuhr des zu fragmentierenden Materials zum und aus dem Reaktionsvolumen;
• Anordnung von Hochspannungs- und Masselektrode derart, dass große Materialdurchsätze erzielt werden.

The process reactor fulfills the following requirements:

• continuous and controlled supply and removal of the material to be fragmented to and from the reaction volume;
• Arrangement of high voltage and ground electrode such that large material throughputs are achieved.

• Die Füllhöhe des Materials im Prozessreaktor wird konstant gehalten. Dies ist ein wesentlicher Punkt, da beim Versagen der Staueinrichtung der Prozessreaktor in dem Fall, in dem die Anlieferung des Materials schneller erfolgt als die Bearbeitung und Abfuhr - ein Szenario, das bei Betriebsstörungen leicht eintreten kann - sukzessive mit zugeliefertem Material aufgefüllt werden würde. Dies hätte zwei nachteilige Auswirkungen:
  • Erstens, die Materialkinetik im Prozessraum wird durch die Überschichtung mit großen Materialmengen eingeengt. Das Material kann sich bei der Bearbeitung unter der Einwirkung der Schockwellen bei jedem Puls weniger frei umschichten und die Fraktionierung erfolgt weniger gleichmäßig.
  • Zweitens, die hohe Überschichtung des Reaktionsraumes mit nachfolgendem Material führt erfahrungsgemäß zu Kavernenbildung, als Silo-Effekt bezeichnet. Diese Kavernen sind teilweise durch Ausbildung einer Art Gewölbedecke von so großer Stabilität, dass die Materialnachförderung total zum Erliegen kommt.
• Die mittlere Verweildauer des zu fragmentierenden Gutes im Reaktionsvolumen kontrolliert, um den gewünschten Grad der Fragmentierung durch eine mittlere Zahl von Entladungen je Masseeinheit des durchgesetzten Materials zu erreichen.
• Das fragmentierte Material wird aus dem Reaktionsvolumen kontrolliert und kontinuierlich abgeführt.

These measures provide the following benefits:

• The filling level of the material in the process reactor is kept constant. This is an essential point, since in case of failure of the storage device, the process reactor in the case in which the delivery of the material faster than the processing and removal - a scenario that can easily occur in case of breakdown - gradually filled with supplied material would become. This would have two adverse effects:
  • First, the material kinetics in the process space is narrowed by overlaying with large amounts of material. The material is less free to redeploy on each pulse during processing under the action of shock waves and fractionation is less uniform.
  • Second, the high overlaying of the reaction space with the following material leads experience to cavitation formation, called silo effect. These caverns are partly by the formation of a kind of vaulted ceiling of such great stability that the Materialnachförderung totally comes to a halt.
• The average residence time of the material to be fragmented in the reaction volume is controlled in order to achieve the desired degree of fragmentation by an average number of discharges per unit mass of the material passed through.
• The fragmented material is controlled from the reaction volume and continuously removed.

• Die Hochspannungsentladungen gehen bevorzugt durch das zu fragmentierende Material, es wird elektrodynamisch fraktioniert, d.h. Entladungswege durch das Material explodieren dasselbe zunächst, darauf folgende Schockwelleneinwirkung mahlt das Material weiter durch äußere Einwirkung.
• Keine Entladungen treten an der Oberfläche der Isolation der Hochspannungselektrode auf.

The design of the electrode geometry brings the following advantages:

• The high-voltage discharges are preferably passed through the material to be fragmented, it is electrodynamically fractionated, ie discharge paths through the material explode the same first, then subsequent shock wave milling the material further by external action.
• No discharges occur on the surface of the insulation of the high voltage electrode.

Correspondingly constructive, field-relieving measures, as in the DE 101 26 646 A1 described are made in the region of the insulation end by the shaping of the high voltage electrode.

• der Reaktionsraum ist bei gleichem Elektrodenabstand auf Grund seiner konischen Ringform wesentlich größer, demnach kann mehr Material durchgesetzt und bearbeitet werden;
• der Abbrand beider Elektroden ist wegen derer größerer Oberflächen und der statistisch über deren Umfang verteilt auftretenden Funken geringer;
• die Masseelektrode, das Staurohr, weist nicht die üblichen siebähnlichen Strukturen mit den damit verbundenen Problemen der mechanischen Stabilität sowie der Verstopfung auf;
• eine Kompensation des Elektrodenabbrandes wird durch eine vertikale Verschiebung in z-Richtung der HV-Elektrode gemeinsam mit deren Isolator 2 durchgeführt und damit auch der Elektrodenabstand g an die optimalen Prozessparameter angepasst;
• wegen der stochastischen Natur der Verteilung der Materialbrocken in der Reaktionszone bzw. der Funkenbildung ist das Staurohr insgesamt die Masseelektrode und hat daher auch eine axiale Ausdehnung

Compared to the previously commonly used, cylindrical HV electrodes, which face a ground plate or a sieve bottom at intervals of about 20 to 40 mm (see, eg DE 195 34 232 C2 ), the electrode arrangement given here has the advantages:

• the reaction space is much larger at the same electrode spacing due to its conical ring shape, therefore, more material can be enforced and edited;
• the erosion of both electrodes is less because of their larger surfaces and the statistically distributed over the circumference occurring sparks;
• the ground electrode, the pitot tube, does not have the usual sieve-like structures with associated problems of mechanical stability and clogging;
• a compensation of the electrode erosion is carried out by a vertical displacement in the z-direction of the HV electrode together with its insulator 2 and thus also the electrode distance g adapted to the optimal process parameters;
• Because of the stochastic nature of the distribution of the chunks of material in the reaction zone or the sparking, the pitot tube is the total ground electrode and therefore also has an axial extent

In the following, the structure of the process reactor according to claims 2, 7 and 8 will be presented with reference to the drawing.

FIG. 1 shows the process reactor in axial section, FIG. 2 enlarges the reaction area with the near environment and the pitot tube.

The material to be fragmented is conveyed / vibrated via the oscillatingly mounted tube 5, the vibrator, from the material receiving funnel into the barrel-shaped reaction container 1 made of sheet metal. The amount of material supplied is adjustable by the intensity of the vibratory conveyor drive 6. In order to avoid overfilling of the reaction container 1 but also to protect the high voltage electrode 3 together with the insulator 2, the baffle plate 7 is installed height adjustable. With the adjustable passage width w between the baffle plate lower edge and the funnel-shaped wall of the reaction vessel 1, the height of the bed of the material to be processed in the reaction chamber above the reaction zone 8, regardless of the intensity of the vibratory conveyor 6 or Material transport limited to the top. This reduces the residence time of the material before it is processed. The restriction of the total amount of material in the reaction vessel 1 is also important in the case of repair work.

The plate-like shaped end 4 of the high voltage electrode 3 with the mean diameter d _{e of} the forehead forms the annular gap of width g with the opposite funnel-shaped ground electrode 9. The high voltage discharges occur preferably at the highest field strengths, ie between the end 4 of the high voltage electrode 3, a hereby in contact mineral material chunks with lower relative dielectric constant ε _r than the process liquid, here water, and the reaction vessel 1 here to ground / ground potential. In the spatially and temporally statistical contact of the Fragmentierguts with the electrodes 4 and 9, as well as the HV discharges occur statistically distributed over the circumference of the electrodes 4, 9.

The inflow and outflow of the process fluid required for the electrodynamic fragmentation-mostly water-take place via openings in the bottom of the reaction vessel 11, 12.

Above the reaction zone 8 sufficient material to be fragmented is heaped up and the material throughput through this zone is not geometrically limited, even if the pulse generator / electrical energy store is sufficiently powerful. Then, the average residence time T _{M of} the material in the reaction zone is determined by the speed of material withdrawal through the pitot tube 9. The pitot tube 9 is strongly conical with its high voltage electrode 3 opposite region, here has a circular cross-section and opens slightly conical downward. The entry of the reaction zone 8 into the pitot tube has the smaller inside diameter d _o and thus the circular entrance surface A _o and the exit the larger clear width d _u with the corresponding larger exit area A _u . The withdrawal speed v ₀ or delivery rate dV / dt from the Reaction zone 8, determined by the adjustable distance a between the output of the pitot tube 9 and the transport unit 10, which is here a conveyor belt, which moves at the adjustable speed v _o , determined by the backflowing surface of the discharge on the conveyor belt. The length 1 of the pitot tube 9 is chosen so that a stable angle of repose forms on the backstoping surface under water and despite the vibrations caused by the fragmentation process. Under these conditions, the mean number n of high-voltage pulses, which acts on the amount m of the material passed, determined by the stagnation parameters a, v ₀ and the pulse repetition frequency f of the high voltage pulses. These parameters control the degree of fragmentation of the material passed through. With constant stagnation parameters, the increase / reduction of the pulse repetition frequency f leads to a higher / lower fragmentation. If the limits of the performance of the pulse generator are reached or if the electrode gap g and / or the electrode-side diameter d _o of the pitot tube limit the perturbation parameters have to be adjusted, ie the distance a to the backflowing element and / or the speed v _{o of} the backflowing surface are reduced ,

List of reference numbers :

1.

reaction vessel

Second

High-voltage insulator

Third

High-voltage electrode

4th

End / end of the high voltage electrode

5th

Pipe / shaker

6th

Vibratory conveyor drive

7th

flapper

8th.

reaction zone

9th

Pitot tube, ground electrode

10th

transport unit

11th

jet

12th

strainer

References:

[1]

Hammon J. et al. "Electric pulse rock sample disintegrator", Proc. 28th IEEE Int. Conf on Plasma Science and 13th IEEE Int. Pulsed Power Conf. (PPPS-2001), Las Vegas, USA, June 17-22, 2001, pp 1142-1145

[2]

Andres, J. in: Int. Journal of Mineral Processing, 4 (1977) 33-38

Claims (11)

1. Process reactor for the fragmentation of lumpy mineral materials immersed in a process liquid in an electro-dynamic manner by means of pulsed high-voltage discharges, the said process reactor comprising:

   a reaction container with a funnel-shaped bottom,

   an electrode that extends from above into the said reaction container and can be impinged upon by high-voltage, the high-voltage electrode, being encased up to its end region by an electric insulating means, wherein the high-voltage electrode is displaceable along its axis such that, the end of the said high-voltage electrode is located on the funnel-shaped bottom of the reaction container, at a variable spacing, opposite the central outlet, where the other electrode, at electric reference potential, is situated, characterised in that:

   the outlet on the funnel-shaped bottom opens out into a Pitot tube, under which there is situated a transport unit (10) for removing the material, the said transport unit removing the processed fragmented product to be packed into sacks by the pressure tube,

   a material supplying device (5) opens out into the opening in the wall of the reaction vessel (1), the said material supplying device introducing material to be fractioned into the reaction vessel (1), and

   a dynamic pressure device (7) is situated upstream of the material inlet in the reaction vessel (1), the said dynamic pressure device controlling the material flow and the filling level in the reaction chamber or the material flow being controlled by means of the said dynamic pressure device.
2. Processing reactor according to claim 1, characterised in that the central outlet at the funnel-shaped bottom is a metallic Pitot tube (9) of the length I with the upper clearance do and the lower clearance du, where do < du, has a conical edge, is admitted into the conical part of the funnel-shaped bottom in a flush and smooth manner and forms the electrode at reference potential, the wall mounted on the funnel-shaped bottom of the reaction vessel (1) is also metallic and the said wall and the Pitot tube (9) are at a common electrical potential, the reference potential.
3. Processing reactor according to claim 2, characterised in that the high-voltage electrode (3) is made of low-combustion metal that is highly electrically conducting,
   an insulating hose to the cold water supply is connected to the said high-voltage electrode externally of the reaction chamber,
   the free end situated opposite the electrode at reference potential is widened in the shape of a funnel and,
   wherein the face with the diameter de, in an equidistant manner and at the extensively constant width g, is located opposite the conical widening at the outlet tube (9), thereby forming a conically ring-shaped gap between the high-voltage electrode (3) and the electrode (9) that is at reference potential, and consequently forms the conically ring-shaped reaction zone (8) for the fragmenting.
4. Processing reactor according to claim 3, characterised in that high-voltage electrode (3) is fully cylindrical or hollow cylindrical and has a round or polygonal cross-section.
5. Processing reactor according to claim 4, characterised in that the material supplying device (5) is a vibrator or a conveyor belt.
6. Processing reactor according to claim 5, characterised in that the dynamic pressure device (7) is a vertically adjustable baffle wall.
7. Processing reactor according to claim 5, characterised in that the dynamic pressure device (7) is a group made up by at least one channel circulating in a horizontal or helical manner on the inside wall of the reaction chamber, holes being located along the bottom line of the said channel, to each of which a tube with at least the clearance of the diameter of the hole is affixed, and the tubes lead downwards in the vicinity of the reactor wall and end shortly before the reaction bottom.
8. Processing reactor according to one of claims 5 to 7, characterised in that the transport unit (10) is a baffle plate for the removal of the material.
9. Processing reactor according to one of claims 5 to 7, characterised in that the transport unit (10) is a conveyor belt for the removal of the material.
10. Processing reactor according to one of claims 8 and 9, characterised in that the surface of the ring-shaped face of the high-voltage electrode (3) is developed smoothly or in such a manner that through the shaping local magnifications of the electric field come about.
11. Method for fragmenting lumpy mineral materials immersed in a process liquid in an electro-dynamic manner by means of pulsed high-voltage discharges including a processing reactor in accordance with one of claims 1 to 9, the said method comprising the steps:

    the material to be fragmented is introduced into the barrel-shaped reaction container (1) in a controllable manner by means of a material supplying device,

    the height of the loose material in the reaction container (1) is limited upwards by means of a dynamic pressure device,

    the mean dwell time TM of the material in the reaction zone (8) is determined by means of a Pitot tube (9) underneath the reaction zone (8) through the speed of the material removal, wherein the said speed is determined by the discharge rate dV/dt of the transport / material removal unit (10),

    the length I of the Pitot tube (9) is selected such that during the fragmenting process the fragmented product falls on the transport unit (10) at a stable angle of repose,

    the degree of fragmentation of the processed product is set by means of the average number of the high-voltage pulses n, which have an effect on the quantity m of the material situated in the reaction zone, and the discharge rate dV/dt as well as the amount of energy registered in the material per high-voltage pulse and the pulse repetition frequency f of the high-voltage pulse.

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