EP0850107A1

EP0850107A1 - Method of comminuting and crushing conglomerated solids into non-metallic or partially metallic components and for comminuting homogeneous non-metallic solids

Info

Publication number: EP0850107A1
Application number: EP96930040A
Authority: EP
Inventors: Christoph Schultheiss; Georg Müller; Volker Neubert; Valeri Isaakovich Kuretz; Eduard Tarakanovski
Original assignee: Forschungszentrum Karlsruhe GmbH
Current assignee: Forschungszentrum Karlsruhe GmbH
Priority date: 1995-09-15
Filing date: 1996-08-14
Publication date: 1998-07-01
Also published as: DE19534232A1; JPH0975769A; AU6924496A; WO1997010058A1; DE19534232C2

Abstract

The invention concerns a method of comminuting and crushing solids which may be partially metallic such as, for example, blocks of reinforced concrete. In contrast to the known electrohydraulic method, in which comminution is brought about by the effect of shock waves applied to the solids from the exterior, with the novel method the solid is exploded as a result of shock waves being produced therein. This occurs by observing various sets of parameters with respect to breakdown voltage amplitude, a minimum time for reaching this amplitude and the greatest possible input of energy into the solid. With minimum expenditure of energy, this method achieves the same result as the purely electrohydraulic method which consumes far greater amounts of energy.

Description

Process for comminuting and crushing solids conglomerated from non-metallic or partially metallic components and for comminuting homogeneous non-metallic solids

The invention relates to a method for comminuting and crushing solids conglomerated from nonmetallic or partially metallic constituents and for comminuting homogeneous nonmetallic solids by rapidly discharging an electrical energy store with a high voltage amplitude. In addition, the invention relates to uses of the method to break down different types of substances by type. For this purpose, the solid materials are immersed in a liquid which is held in a suitable vessel. The electrode system consisting of high-voltage electrodes and grounded electrodes of the electrical discharge circuit protrudes into the mixture of liquid and solid. The discharges take place individually or at periodic intervals, the latter being limited in their repetitive frequency by the dimensioning of the components of the system, essentially by the charging constant of the energy store and necessary relaxation processes such as the breakdown of bubbles in the process liquid.

The purpose of such processes is to disassemble the above-mentioned conglomerated solids such as concrete, reinforced concrete, metal ceramics or other composite, brittle material mixtures or brittle non-metallic bodies with a homogeneous composition such as graphite, glass and ores or simply up to to crush a grain size that is useful for a further use process.

Fragmentation of solid bodies by shock waves is known per se and is often mentioned under the term electrohydraulic comminution or crushing of solid or brittle bodies. Mostly these are pulse discharges from capacitor banks in water by means of an electrode system immersed in them. The shock wave generated during the discharge is directed either by a focussing element (parabolic mirror in a lithium transponder) or without such means onto the material to be broken up and crushed. The decrease in the intensity of the shock wave with distance and the reflection and transmission at interfaces are limiting physics.

A method for crushing ores with explosive energy which is released in a liquid and an apparatus for carrying out the method is specified in US Pat. No. 3,207,447. In the process, ore is mixed with the liquid to form a sludge and filled into the reaction vessel. Explosions are then periodically generated there, which smash the ore particles over the shock wave generated in this way, so that the usable components can be separated from the useless components. The explosions are achieved by discharging an electrical energy store. For this purpose, electrodes protrude into the sludge contained in the vessel.

Soviet development groups carried out essential work in this area of material destruction. In SU 1542619 AI, a system for controlling an electro-hydraulic mill is opened. Shock waves act on the material to be comminuted from the outside (electrohydrau¬ iisch). A control system guides the system optimally and maintains the good efficiency in the smashing device.

In SU 1719075 AI a vessel is presented in which materials can be smashed with a higher degree of efficiency by focusing the shock wave. For this purpose, the vessel is covered at its opening with a device which reflects the shock wave emanating from the electrical discharge between the anode and cathode and focuses on the pile of material lying on the bottom of the vessel. This lid is elastic connected to the vessel wall in order to cushion the mechanical load from the shock wave.

In the cited documents, the underlying principle of material destruction is the generation of a shock wave by electrical discharge in the liquid. The shock wave thus generated in the reaction vessel acts on the objects to be smashed from the outside (electrohydraulics). A high expenditure of energy is necessary for this, since the hard or brittle materials immersed in the liquid have to be broken up by the action of pressure from the outside, comparable to hammer blows. A balance of the energy input shows only from a physical point of view that no amount of energy can be introduced into the solid in the liquid through the shock wave effect, so that the destruction process can only be improved on this basis by means of higher discharge currents and thus larger energy stores.

As is known, the intensity of the shock wave decreases with 1 / r ² from the point of origin. At the liquid / solid interface, the incoming shock wave is split up, namely that about 2/3 is reflected in water as liquid and about 1/3 penetrates into the body to be destroyed. B., a. The energy input into the solid via electro-hydraulic action is therefore proportionately small.

The increase in the storage energy by means of an enlarged capacitor battery means higher discharge currents, which entails a greater load on the components via current load (on switching components) and shock wave (vibration on particularly exposed components in the reaction vessel).

The invention is based on the object of supplementing or replacing the electrohydraulic smashing method by means of shock waves in such a way that with a considerably higher energy entry into the body to be destroyed, smashing is achieved with less energy expenditure.

According to the invention, the object is achieved by the method steps of claim 1 while observing the specified parameter ranges. The apparatus structure can be suitable for the respective material, which, in addition to the usual material placement in the liquid, is also based on the easy material loading and rapid material removal.

The main idea that brought decisive progress arose from the findings of experiments and the measurements obtained in the process, which are to be explained using a model and the voltage-time profiles based on it. FIG. 1 a shows the electrical model on which the interpretation of the processes during the discharge in the reaction vessel is based.

If a voltage pulse with a very short (steep) rise time is applied to a liquid and a solid - the electrode spacing is the same - an electrical breakdown is observed after a delay T. The time delay τ is smaller, the higher the applied voltage. FIG. 2 shows such distortion curves for rock, water, transformer oil and air. All curves generally show a non-linear drop in the required breakdown voltage with increasing delay time T, but the drop is not the same in time and the voltage level is sometimes significantly different, that is to say material-specific. For example, air is characterized by a curve of the voltage-time curve that has very low voltage values throughout. In contrast, transformer oil has a very high voltage level throughout.

Two curves in FIG. 2 show that the breakdown voltage curve depends on a type of solid (stone) and flux. cut liquid (water). If the breakdown voltage is reached in this intersection time, 500 nsec for this example, the breakdown can take place both in stone and in the liquid. If the tension rises faster than this point of intersection, then the breakthrough in stone is more likely. If the voltage rises more slowly, the breakthrough in water is more likely. The tendency to break through is of course the more probable for one or the other medium, the more clearly the voltage rise on the side or beyond the delay time τ is for the intersection. The delay time specification τ or the time τ until the breakdown voltage amplitude is reached in claim 1 is therefore material-specific. It has only proven to be reliable for many rock-like materials and ores. In one or the other application, it could be modified in the case of intersecting characteristic curves of the material to be destroyed and reaction liquid, taking into account the delay time at the intersection of the two.

This is illustrated in FIG. 3, in which tolerance bands are placed around the associated breakdown voltage curve along both intersecting curves. The left corner point of the common overlap area indicates the delay time τ for which the electrical breakthrough in the solid (stone) takes place very reliably first. A discharge in the water does not take place because of this voltage breakdown in the rock (see figure la).

The right corner point of the common overlap area indicates the time of delay from which the breakthrough in the liquid occurs.

The situation takes an intermediate position when there is water and rock between the electrodes, that is, the solid body is immersed in the liquid (FIG. 1b). During the increase in voltage, charge carriers are generated in the rock, even at lower field strengths, along the electrical Field lines are shifted and due to this shortening of the path lead to increased field strength in the remaining waterway. According to FIG. 2, the field strength then locally reaches the breakthrough field strength in the liquid, so that the discharge through the rock and water runs simultaneously.

The vertical line through the intersection of the two curves (FIG. 4) at about 500 nsec separates the areas, destruction by externally acting shock waves (compression destruction) and destruction caused by the current flow through the solid (explosion destruction). In order to safely provoke the discharge in the rock, the voltage increase based on FIG. 3 (tolerance bands) should take place significantly below this time T = 500 nsec. For the example shown in FIG. 4, a voltage rise to the breakdown voltage below the delay time of 200 nsec was selected for the safe current flow regime. If air were used instead of water, there would definitely be a discharge in air. Would an electrically insulating liquid according to claim 3 be used instead of water, the z. B. transformer oil, an alcohol or any other liquid with a high electrical insulation, falling below this limiting delay time would not be so problematic, since then the discharge would go through the immersed solid.

Such a system can therefore be operated much more efficiently than in the pure electrohydraulic regime if: the field strength between the electrodes is in the range between 10 kV / mm and 30 kV / mm, the voltage rise to breakdown voltage takes place within 200 nsec, or more generally: the reliability is considerably shorter than the delay time at the point of intersection of the liquid and solid reaction medium in the reaction vessel, and the energy coupling along the discharge path in the solid, based on this path, is in the range between 12 J / mm and 40 J / mm holds. The energy input per discharge determines the action mechanism in the solid. The parameter range is selected so that in the solid body along the unloading path by energy coupling the body is torn by the shock wave generated inside, so to speak an explosion tearing. It comes about as follows:

The heat coupled in along the discharge path in a very short time is not and cannot be dissipated sufficiently quickly via heat conduction, but rather releases a shock wave in the solid body via velocity components of the atoms, directed away from the discharge channel. The effect of the shock wave is strengthened by the superposition of reflected portions of the shock wave at the interfaces of the solid body to the liquid medium, as a result of which the solid body is further broken down into fractions.

The advantage of a shock wave generated in the material itself compared to an external impact on the body is incomparably higher on the basis of the one explained above in the introduction. The shock wave generated in the solid body around the discharge channel loses only about 1/3 of the intensity to the liquid process medium due to transmission at the solid body interface, 2/3 are reflected there and continue to strain the body when it moves through it. It is understandable by this model that the shock wave generated in the body and the resulting explosion rupture place a much greater burden on the body than the shock wave action from outside in the form of compression on the body.

The impact on rock in water was checked in a small laboratory facility. For the discharge only in water, i.e. shock wave from the outside on the body, more than 10kJ / pulse was required for the compression destruction, for the discharge in the solid state, i.e. current flow through it and thus explosion rupture, it was with 0.6 to 1 kJ / pulse - enough. This is an energy order of magnitude lower.

The solid bodies immersed in the process liquid can be successively reduced to a predetermined grain size by repeated unloading processes. In the case of glass, the grain size of the destroyed goods down to 40 μm can be achieved without increasing the efforts for this. The minimum grain size that can be achieved with this method is material-specific and can be quickly determined by tests in a laboratory system.

Further process steps, which turn out to be advantageous in one or the other smashing project, relate to the selection of the process liquid as characterized in subclaims 2 and 3.

There are many reasons why the liquid used to crush and break up the material immersed in it. Primarily, it will be the high effectiveness of material destruction. It is important how the mixture of process liquid and the fractions present in it can be further treated, separated and processed or disposed of. Claim 2 therefore identifies tap water or demineralized water as the process liquid with which the minimum time in the voltage rise due to the intersection of the breakdown curve of water and that of the solid must be undershot. Claim 3, on the other hand, characterizes liquids with good electrical insulation, such as transformer oils, alcohols, paraffins in liquid, that is to say heated, or liquid substances, cooled or heated, with which a breakthrough in the solid is achieved in any case. However, precautionary measures to be taken with regard to environmental pollution cannot be overlooked and could therefore very well disqualify a very effective process fluid. On the other hand, if the solids to be processed are not hard or brittle enough, this can be achieved by a cold process liquid. Liquid nitrogen is known to be such a liquid with which embrittlement can be achieved.

Basically, it should not be chemically reactive. Liquid air or even liquid oxygen is therefore excluded as a process liquid without any special precautions.

The process liquid may well be a multi-component liquid with the above-mentioned properties.

Claim 5 characterizes the choice of polarity of the high voltage. Experience has shown that a positive polarity of the high voltage at the one electrode immersed in the liquid and the other electrode at ground potential in the form of a sieve, for example, through which the small fractions fall, work more efficiently than if it had high electrode negative polarity. This can be explained plausibly on the model of the gas breakthrough between the anode and the cathode.

The method can be used in a wide variety of ways, as is characterized in the claims 6 and 7. It can be used to process ore-containing rock, inclusions containing precious metals or to uncover minerals and crystalline inclusions (claim 6).

It can be used for the separation of metal-plastic-ceramic connections or combination connections therefrom (Claim 7), as they occur when recycling technically high-quality products at the end of their service life.

In summary, it is emphasized that only the setting of the parameter sets in compliance with the (possibly specific - Deletion) time for reaching the breakdown voltage amplitude, as listed in the form of the two inequalities in claim 1, crushing or shattering of the solid-like material via explosion destruction with minimal energy expenditure is possible. The compression destruction (electrohydraulics) requires an energy expenditure that is at least an order of magnitude higher for the same effect. The inventive method has already been explained and explained in detail above. For the sake of completeness, the structure and mode of operation of a system with which the method can be carried out are briefly described. In addition to the figures in the drawing which have already been described, two more are added via a basic system structure and an exemplary reaction vessel. The drawing therefore consists of:

Figure la model for viewing the unloading processes,

FIG. Lb model for viewing the unloading processes,

FIG. 2 curve of the breakdown voltage as a function of the delay time,

FIG. 3 curve of the breakdown voltage in the tolerance band,

FIG. 4 classification of FIG. 2 into the current flow and shock wave regime,

Figure 5 Structure of the smashing plant and

Figure 6 shows the reaction vessel in section.

First, Figure la is briefly explained again from the electrical structure. It shows the electrical scheme for the determination of the breakdown voltage curves. The source 13, which consists of a converter and transformer, feeds the capacitor 10, which then passes into the load via the spark gap 14 16 discharges. The load 16 consists of the electrically parallel arrangement of solid and liquid.

An exemplary smashing and crushing plant is shown in FIG. 5. The reaction vessel 1 is located on a frame 2. In the frame 2 is the collecting vessel 3 for the fractions 5 that have sunk through the sieve 4 and are deposited on the bottom. The sieve 4 is connected to earth potential. The reaction vessel 1 consists of an impact-resistant plastic which can absorb the impacts during the discharges. The indicated rings 6 are mechanical reinforcement rings which also extend the electrical creepage path, so that creep discharge along the reaction vessel is at least very difficult or even completely prevented. The positively polarized high-voltage electrode 7 projects into the reaction vessel. It is connected to the energy store 8. The energy store 8 consists of the capacitor bank 10 and the voltage multiplier circuit 9.

The entire energy store is also on a frame 11, under which the control cabinet 12, the converter transformer 13 and the switching path 14 to the energy store 8 are located.

Without going into technical details here, Figure 6 is briefly explained in the schematic structure. The section through the wall of the reaction vessel 1 shows the structural arrangement. The hemispherical sieve 4 has a mesh or hole size such that fractions with the desired grain size can fall through or sink through and settle on the bottom of the collecting vessel 3. From there they can be sucked off together with the liquid through the bottom opening. The sieve 4 forms the grounded electrode 4. The reaction vessel 1 is covered with a cover 20, through which the high-voltage electrode 7 projects into the interior of the vessel so that the electrode tip is at the predetermined distance from the sieve 4. The high-voltage electrode 7 is surrounded over a long way in the reaction vessel 1 by a cylindrical insulator 21, which prevents parasitic discharges into the filled process liquid. The bulges 6 are the rings mentioned above for mechanical support of the reaction vessel and for extending the electrical creepage distance.

Plants of this type and for such uses have a wide variety of structural designs, particularly when they are embedded in processing processes.

Reference list

1 reaction tube

2 frames

3 collecting vessel

4 sieve, grounded electrode

5 fraction

6 ring, bulge

7 high voltage electrode

8 energy storage

9 voltage multiplier circuit

10 capacitor bank, capacitor

11 frame

12 control cabinet

13 converter transformer, source

14 switching path, spark gap

15 switches

16 load

17 solids

18 liquid

19 bottom opening 20 lid

21 isolator

22 spark gap, switch

Claims

claims

1. Process for comminuting and crushing solid bodies conglomerated from non-metallic or partially metallic constituents and for comminuting homogeneous non-metallic solid bodies by rapid discharge of an electrical energy store, the solid bodies or solid body fragments for this purpose in the electrically non-conductive or only weakly conductive process fluid contained in a vessel are immersed, into which a system of high-voltage electrodes and grounded electrodes protrude at a predetermined distance from their ends to one another into the mixture of process liquid and solid,

consisting of the following steps per energy storage discharge,

the distance 1 of the ends of the high-voltage electrode and the grounded electrode to one another is set such that the field strength between the electrode ends during the pulse values between

10 kV / mm <U / 1 <30 kV / mm reached,

the dimensioning of the discharge circuit LC is kept such that the high voltage pulse rises up to the breakdown voltage amplitude in t <= 200 nsec,

The energy input of the discharge related to the discharge path 1, which is caused by the voltage and the capacitor capacity, is in the barrier

12 J / mm <1/2 Cu ^2/1 <40 kept * J / mm, the solid bodies or solid body fragments are exploded by shock waves triggered in them along the internal discharge paths,

the solid bodies or solid body fragments are additionally crushed (compressed) along the discharge paths in the process liquid that develop later in time by shock waves thereby triggered.

2. The method according to claim 1, characterized in that tap water and / or demineralized water is used as the liquid.

3. The method according to claim 1, characterized in that the liquid used is a high-voltage insulating liquid whose breakdown voltage curve is always higher than that of the solid body immersed in it to be processed.

4. The method according to claim 1, characterized in that the liquid is a water-glycol mixture or a water-Alko¬ hol mixture or a multicomponent mixture thereof.

5. The method according to claims 1 to 4, characterized in that the polarity of the high voltage material-specific and after effectiveness of the destruction is set positively or negatively.

6. Use of the method according to claims 2 to 5, characterized in that it is used to expose inclusions such as precious metals, precious stone or minerals in natural rock, or that it is used for the decomposition of crystalline heterogeneous bodies into its components, or that it is used for the separation of metal-ceramic composites.

7. Use of the method according to claims 2 to 5, characterized in that it is used for the separation of metal-plastic compounds or for the separation of plastic-ceramic compounds or for the separation of a composite of metal, ceramic and plastic.