Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C19/00—Other disintegrating devices or methods
  • B02C19/18—Use of auxiliary physical effects, e.g. ultrasonics, irradiation, for disintegrating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C19/00—Other disintegrating devices or methods
  • B02C19/18—Use of auxiliary physical effects, e.g. ultrasonics, irradiation, for disintegrating
  • B02C2019/183—Crushing by discharge of high electrical energy

Definitions

• 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.
• the invention relates to uses of the method to break down different types of substances by type.
• 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.
• 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. Usually 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.
• 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.
• electrodes protrude into the sludge contained in the vessel.
• a vessel in which materials can be smashed with a higher degree of efficiency by focusing the shock wave.
• 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.
• 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.
• the intensity of the shock wave decreases with 1 / r 2 from the point of origin.
• 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.
• 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.
• 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.
• FIG. 1 a shows the electrical model on which the interpretation of the processes during the discharge in the reaction vessel is based.
• 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.
• air is characterized by a curve of the voltage-time curve that has very low voltage values throughout.
• 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 ⁇ is for the intersection.
• the delay time specification ⁇ or the time ⁇ 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.
• the right corner point of the common overlap area indicates the time of delay from which the breakthrough in the liquid occurs.
• 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.
• 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 solid bodies immersed in the process liquid can be successively reduced to a predetermined grain size by repeated unloading processes.
• the grain size of the destroyed goods down to 40 ⁇ m 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.
• 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 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.
• 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.
• 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).
• 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 6 shows the reaction vessel in section.
• 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.
• the reaction vessel 1 is located on a frame 2.
• 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.
• FIG. 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.

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• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Disintegrating Or Milling (AREA)

Applications Claiming Priority (3)

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• 1995
  • 1995-09-15 DE DE1995134232 patent/DE19534232C2/de not_active Expired - Lifetime
  • 1995-12-07 JP JP31918795A patent/JPH0975769A/ja active Pending
• 1996
  • 1996-08-14 WO PCT/EP1996/003591 patent/WO1997010058A1/de not_active Application Discontinuation
  • 1996-08-14 AU AU69244/96A patent/AU6924496A/en not_active Abandoned
  • 1996-08-14 EP EP96930040A patent/EP0850107A1/de not_active Withdrawn

Non-Patent Citations (1)

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