EP0935513A2

EP0935513A2 - Method and device for recycling abrasive agents used in water jet cutting

Info

Publication number: EP0935513A2
Application number: EP97949858A
Authority: EP
Inventors: Hans-Günter Weide; Gerhard Hering; Jörn SCHATZ
Original assignee: Intrec Gesellschaft fur Innovative Technologien Mbh
Current assignee: Intrec Gesellschaft fur Innovative Technologien Mbh
Priority date: 1996-10-24
Filing date: 1997-10-23
Publication date: 1999-08-18
Also published as: DE19645142A1; WO1998017439A2; AU5306098A; WO1998017439A3

Abstract

The invention describes a process and a device for recycling sand and can, for instance, be used to recycle part of the reusable cutting agents that accumulate during sandblasting, especially abrasive high pressure water jet cutting, and to produce waste water which can be introduced into a circuit. The method is characterized in that fine grain particles are rinsed in an up-current, sedimented during calming phase of current, after which they are filtered and collected, and large grain particles are carried away, mechanically pre-desiccated, dried and despatched for reuse. The inventive device essentially contains at least one classifier operating according to the principle of up-current separation, connected on the overflow side to at least one fine particle path, comprising a baffle plate clarifier, a sedimentation basin, a take-out device and a final clarifying basin, and connected on the outflow side to at least one large grain particle path, comprising an intermediate container for large particles, a dryer, a tank for dry product and pumps that pump the solid-laden water out of the cutting basin and redirect the water arising from the fine grain particle path and large grain particle path to the cutting basin as industrial water.

Description

Method and device for recycling water jet cutting abrasives

Description

The invention relates to a method and a device for recycling the portion of cutting material which is produced and reusable in sandblasting, in particular in abrasive high-pressure waterjet cutting, and for producing a dischargeable wastewater.

By adding suitable cutting agents such as almandine garnet sand as an abrasive to a transport medium, for example water, a high separating effect can be achieved with water jet cutting, provided that a thin jet of this suspension is applied to the material to be cut at high speed and thus high kinetic energy is judged. The achievable cutting parameters for a given cutting substance are, apart from their chemical and physical properties (interaction with the material to be cut, hardness, etc.), very much dependent on the grain size and shape (spherical-round, angular-sharp-edged) of the corresponding particles. The grain parameters are changed already during the acceleration phase of the particles in the suspension, but also due to the mechanical interaction with the material to be cut.

According to the prior art, the cutting means changed after the cutting work has been carried out. together with the cutting material abrasion generated in a pool filled with water or solids, in which it is collected, suspended and discharged. It is customary to dispose of or process the used abrasive using a more or less complex administrative procedure. Most of the now contaminated water remains in the process as process water, a small proportion of which is often discharged into the sewer with a process-related suspended matter component.

Simple experiments showed that at least 50% of the amount of abrasive used could be used again as a cutting agent after the cutting process and that, accordingly, only half of the abrasive required would have to be disposed of in a costly manner.

The utility model G 93 08 809.4 describes, as a sub-step for sorting the waste sludge from abrasive jet cutting, a device known as a flow separator, consisting of a horizontally positioned pipe, through the inlet connection of which the resulting suspension is let in and whirled up by another medium. After flowing through the pipe equipped with eit- and guide devices, whereby the heavy, reusable particles should collect and move in a "flow layer" on or near the tube sheet, the finer and finest particles, however, above the layer containing the coarser particles through the Pipe flowing to the outlet, a separate recording and forwarding of the suspension fractions is made possible. The disadvantage of this solution, which takes up the elements of the classic horizontal and vertical upstream classifier, is that only a recyclate containing a relatively large amount of fine material is produced.

EP 0 502 461 AI discloses a method and a system for recovering abrasive abrasive material during water jet cutting, the abrasive material deposited on the tub bottom being transported horizontally to a lifting position and being lifted up from there out of the tub and out of the tub the abrasive material that has been removed is then subjected to drying by means of a UV lamp, after which the dried abrasive material is suspended in an air stream and finally collected in different size fractions. A disadvantage of this solution is that both the coarse grain and the fine constituents are dried, although only the coarse constituents can be reused. UV drying is also ineffective. In addition, a dry material made of coarse and fine components tends to cake.

Furthermore, DE 43 03 868 AI describes a method and a plant for the separation and recovery of abrasives in water abrasive jet applications, the separation being realized by hydrocyclones. The particular disadvantage here is that an additional centrifugal force has to be generated and discontinuous operation is problematic.

The invention is therefore based on the object of providing a method and a device which improve the prior art mentioned, with which an effective, reproducible separation of particles of different grain size and shape is possible and the process water entering the wastewater is largely cleaned.

In addition, the device should be inexpensive to manufacture and easy to operate and maintain, and should be flexibly adaptable to specific applications and have a long service life.

This object is achieved according to the invention by the features in the characterizing part of claims 1 and 9 in cooperation with the features in the preamble. Appropriate embodiments of the invention are contained in the subclaims.

A particular advantage of the invention is that an effective recovery of the abrasives is achieved by rinsing the fine-grained particles in an upflow, sedimenting them by calming the flow, then filtering and collecting a certain proportion and removing the coarse-grained particles, mechanically pre-dewatered, dried and be reused.

A system which is simple and inexpensive to produce and easy to maintain results from the fact that at least one classifier operating according to the current separation principle has at least one fine particle section on the overflow side, consisting of lamella clarifier, settling tank and removal device, and at least one coarse particle section on the outlet side, consisting of coarse material wiping container and conveying device with mechanical drainage, dryer and dry goods container, and the process water is returned to the cutting pool. A partial flow of the process water can be pumped through a filter unit, so that a conductive filtrate is obtained. _In addition to the classifying separation to be made on almandine garnet sand or olivine particles according to the particle size, sorting takes place at the same time according to the density-different cutting material particles involved in the sedimenting separation process, so that it was initially assumed that, if cutting material with a higher density than that of the cutting agent, for example Almandine is present, which can also get into the recycled portion in an undesirable manner.

Surveys, however, surprisingly showed only negligible proportions of such admixtures. With the frequently cut stones granite and marble, uniform separation in the garnet coarse fraction can only be determined for very large grains, such as broken pieces.

The invention is to be explained in more detail below on the basis of exemplary embodiments shown at least in the figure. Show it:

1 is a schematic diagram of the recycling plant,

Fig. 2 shows a schematic diagram of a bypass.

The mixture in the cutting basin, also called catcher, after the cutting process, consisting of coarse and fine abrasive and small amounts of material to be cut, predominantly of the finest grain size, is fed by means of a suspension pump Pl designed as a diaphragm pump, whose flow rate in the present exemplary embodiment is approximately 4 m ³ per hour after passing a sieve (not shown in FIG. 1) into an upstream classifier 1, in which the separation into the coarse-grained reusable abrasive fraction and into the fine fraction to be collected takes place. The sieve with a plastic bottom with a mesh size of 600 μm causes the separation of foreign components that are considerably larger in relation to the granular material to be cut, such as flaked stony cuttings or other foreign components that have entered the suspension, such as the smallest cutting material residues that have fallen through the sieve in the cutting basin. At the same time, it reduces the speed of the volume flow of 2.3 m / s entering classifier 1 by more than ten times. In classifier 1, the separation takes place according to the grain size, in that the coarse particles, the sinking speed of which is greater than or at least equal to that of the upward flowing water flow, sink downwards, but the finer grain reaches the overflow with the water flow. The classifier 1 is equipped with a tangential slurry inlet. To protect against shipping, it is automatically emptied before decommissioning. The classifier 1 in the present exemplary embodiment, with its dimensions, height 0.8 m, diameter 0.3 m, is designed for a clearing surface load of 1.6 cm / s at a suspension volume flow of 4 m ³ / h for a separation grain of 100 μm and specially configured for a cutting operation. The bottom of the classifier 1 is designed as a nozzle plate. Due to the process flow or a pure water flow flowing through it through the upflow water pump P3, a fluidized bed enriched with coarse material is formed above this perforated plate, in which it is subjected to an intensive rinsing / washing process, the fluidized bed essentially containing the hydrostatic pressure determined on the bottom of the container. It is also possible to design the nozzle plate as a perforated plate over which an elastic mat, made of silicone, for example, is attached. These slots are opened under inflowing water pressure and create like that Nozzle plate an ascending pure water flow in the classifier 1.

When the water pressure is switched off, the mat bulges back, the slits close and cannot become contaminated by falling abrasive particles.

A pressure transducer was installed to record a differential pressure that is related to an equally high water column, the signal of which controls a servomotor via a controller, which in turn actuates the floor outlet. If the bottom outlet opens, a steady or interrupted flow of recycled thick matter enters the intermediate bulk container 3, from which it is conveyed by means of a conveyor device 3a, e.g. a screw conveyor, into the dryer 4 and after passing through it into the dry goods container 5. The intermediate bulk goods container 3 is designed as a trough with an inclined wall on one side and an adjustable overflow. The level of the sand is sensed and is linked to the dryer 4 and the suspension pump P1 via an NC control.

The intermediate coarse material container 3 is equipped with a device which, in the event of an increased underflow quantity and / or a high sand level, minimizes the quantity of coarse material which undesirably enters the reserve pool 6. It can be adjusted in position, that is to say so that the water overflow edge forms a horizontal plane and the water flowing over it reaches the reserve basin 6 via a circumferential drainage channel. The sediment located in the intermediate bulk container 3 is conveyed by means of a mechanical conveyor 3a, preferably by a slow-moving screw conveyor, into the wet goods feed container of the dryer 4 in such a way that it is supported to a certain extent, for example by perforations in the Boundary wall surrounding the screw, is mechanically pre-dewatered. The inclination and length of the part of the conveying device 3a projecting above the water level are dimensioned in such a way that they enable mechanical pre-dewatering to 10-20% by mass of the moist material entering the dryer 4.

Transport through the dryer 4 is carried out by a revolving steel link belt, into the cavities of which the moist material is introduced. A special, self-adjusting applicator roller, in the present exemplary embodiment a rubber transverse roller 8, is arranged in between to evenly distribute the goods offered by the conveying device 3a over the intended mesh width. The steel mesh moves the moisture in it into the drying zone, where it is washed around on both sides, preferably with preheated (dry) air - recovered from the high-pressure pump cooling or from the cutting basin - with dehydration of the material and humidification of the desiccant in countercurrent. To intensify the drying, for example, heating elements are also arranged on one or both sides next to the braid near the air inlet at the lower part of the dryer 4. At the end of the vertical drying drying section, after passing through a screening device (not shown), the dried goods fall into the dry goods container 5. The dryer 4, which can be expanded, is designed for a moisture content from 12 kg / h. Because of the broader grain spectrum of the abrasive compared to the originally used cutting agent, the favorable cutting parameters achieved were similar to those achieved using high-quality commercial garnet sand.

The - coming out of the classifier 1 containing the fine material that can no longer be used as a cutting agent Overflow suspension arrives in a special device consisting of a combination of lamella clarifier 2a, sedimentation basin 2b and removal device 2c (e.g. filter bag), in which, for example, the lamella clarification part 2a stands detachably on a sealing layer directly on the sedimentation basin 2b and solely by its weight or guarantees the watertightness of the connection point in another suitable manner. The correct, immovable position of the attached lamella clarifying part 2a is ensured by the attached guide element. It has proven to be expedient that the upper basin, that is to say the lamella clarifier 2a, is arranged with all connections fixed to the frame and the other basin, that is to say the sales basin 2b, is lowered during emptying. When filling for the first time, the lower settling tank 2b fills first and then the upper lamella clarifying part 2a. In the filled state, the suspension initially flows horizontally / downwards into the lamella clarifier 2a from the side inlet of the suspension. After reaching the lower end of the plates arranged at a 60 degree inclination at a distance of 2 - 5 cm, the current reverses and flows upwards across the entire clarification cross-section between the plates. The sludge deposited on the plates slides downward against the flow and, after detaching from the lower end of the plate, falls directly into the removal device 2c designed as a fine material collection bag, in which it remains for a few days or weeks until the time of removal and can thus achieve a high degree of compression. The degree of filling or the time of removal is indicated by means of a sensor attached to the settling basin 2b, for example using the bottom plate deflection caused by the sludge weight or a stirring sensor or in another suitable manner. Before the fine material sack is removed, the water in the lamella clarifier 2a and settling basin 2b is first removed by means of an outlet Fes completely drained at the bottom The filter bag in this sedimentation tank retains the solids. After lifting off the clarifier container part which is not firmly connected to the remaining heel basin 2b, the fine material sack can be removed.

The filter bag in this sedimentation tank retains the solids.

Another lamella clarifier 2a can be operated in parallel to avoid downtimes when changing the fine material bag.

In a projected settling area 7-15 m ² and a flow rate of 4 m ³ / h results in the present embodiment, a surface loading of approximately 2 × 10 ^-2 cm / s at 7m. ² Therefore, the container overflow releases largely clarified process water (main stream) into a corresponding reserve pool 6, from which it is pumped back into the cutting pool 10 via the return pump P2. In particular through the entry of the process water further clarified in the lamella clarifier 2a into the reserve basin 6, the water therein is always moved. In order to achieve further clarification, a part of the reserve tank volume, at least the rear third, is almost separated from the remaining volume by at least one lower wall, depending on the flow rates of the upstream water and filter pumps P3 and P4. As a result of the water "calmed" in this container, further fine fraction can sediment. The filter pump P4 for feeding the filter unit 9 and the upstream water pump P3, which are most remote from the lower wall, are located, each taking clean water near the surface. Directly from the container overflow or another suitable location a process water bypass is branched off via a filter pump P4 and fed to a filter unit 9 leads, the effect of which is dimensioned such that - since decoupled from the process water circuit - only the amount of water entered into the cutting basin 10 with the abrasive water jet due to operation and settling and / or filtration, if necessary using flocculants, needs to be subsequently cleaned so that it can be discharged into the sewer according to water law requirements. The largely cleared process water - taken from the (internal) sedimentation chamber located within the reserve pool 6 - is only fed to the filter unit 9 (1 μm pore size) in a controlled amount for fine clarification, which is entered into the system via a cutting head . The water leaving the filter unit 9 is free of recognizable cloudiness for almost the entire filter service life. Its solids content is <5 mg / 1. As the service life of the filter elements, eg candle filters, progresses, the filter resistance increases, the final size or the time of change is indicated by a conventional differential pressure sensor. As a suspension or Return flow pumps use robust electric diaphragm pumps. Due to their arrangement in the upper part of the plant, the cutting basin 10 is reliably avoided when the pump is at a standstill.

In conjunction with the bypass 13 arranged between lamella clarifier 2a and classifier 1, a “shutdown regime” with low-solids process water and its high-level reflux in the event of a shutdown, line blockages are prevented.

In an advantageous modification of the device, a bypass 13 shown in FIG. 2 and provided with switching modules is arranged between the upflow classifier 1 and the lamella clarifier 2a. This bypass 13 causes or enables a low solids water circuit is realized during a limited "start-up" and "shutdown" operating regime, which practically prevents line blockages. Bypassing the upstream classifier 1, the suspension sucked out of the cutting pool 10 can, if necessary, be wholly or partially returned to the latter, for example to avoid overloading the upstream classifier 1, or the suspension can be fed directly to the lamella clarifier 2a. The bypass 13 has actuating elements 11 for opening / closing the flaps 12 and an entrance from the cutting basin 10 and exits to the upflow classifier 1, to the lamella clarifier 2a and back to the cutting basin 10.

The described recycling of an almandine garnet sand can also be applied to olivines and other minerals of suitable density.

The invention is not restricted to the exemplary embodiments shown here. Rather, it is possible to implement and implement further embodiment variants by combining and modifying the means and features mentioned, without leaving the scope of the invention.

Reference list

12 flap

1 On current classifier

13 bypass

2a lamella clarifier

Pl suspension pump

2b sedimentation tanks

P2 return pump

2c removal device

P3 upstream water pump

3 intermediate bulk container P4 filter pump

3a conveyor and drainage

4 vertical belt dryers

Dry goods container

Reserve pool

7. Heating elements

8 rubber cross roller

Filter unit

10 cutting basins

11 actuator

Claims

claims

1. A process for recycling sands from a solid-liquid suspension by separating the coarse-grained particles, wherein no centrifugal forces are generated and used, characterized in that the fine-grained particles are rinsed out in an upflow, sedimented by flow calming, subsequently filtered and collected and the coarse-grained particles are removed, mechanically pre-dewatered, dried and recycled.

2. The method according to claim 1, characterized in that a fluidized bed enriched with sedimented coarse particles is generated in the upflow, which is adjustable in height.

3. The method according to claim 1, characterized in that the drying of the coarse-grained particles is carried out electrically and / or by hot, dry air and / or microwave radiation.

4. The method according to claim 1, characterized in that the water is guided in a process water circuit and only the amount of water is introduced into the sewer, which is introduced by the abrasive water jet. A method according to claim 4, characterized in that the water to be introduced into the sewer through

Settling and / or filtration and / or using flocculants is cleaned to the extent that it is largely free of particles> 1 μm and

Is foreign components.

6. The method according to claim 1, characterized in that the suspension stream entering an upflow classifier is slowed down in its speed by a fine-mesh sieve and distributed over a large area, and coarser foreign components are retained.

7. The method according to at least one of the preceding claims, characterized in that the density of the suspension in the separating device provides a signal for controlling the removal of the coarse-grained particles.

8. The method according to claim 1, characterized in that the mechanical preliminary dewatering of the coarse-grained particles takes place to 10 to 20 Ma.% Of the damp material to be dried.

Device for recycling water jet cutting abrasives from a solid-liquid suspension Pension by separating the coarse-grained particles without the use of hydrocyclones, characterized in that at least one classifier (1) working according to the current separation principle has at least one fine particle section on the overflow side, consisting of lamella clarifier (2a), settling tank (2b) and removal device (2c) , and on the outlet side is connected to at least one coarse particle section, consisting of coarse material intermediate container (3), a conveyor device (3a) enabling drainage, dryer (4) and dry material container (5), and pumps P1, P2) are arranged which load the solids Pump water out of the cutting basin and return the water from the fine particle section and the coarse particle section back into the cutting basin as process water and, if necessary, pump a partial flow in this way with a pump (P4) via a filter unit (9) so that a filtrate that can be introduced is obtained.

10. The device according to claim 9, characterized in that the intermediate bulk container (3) and the dryer (4) via a screw conveyor (3a) and / or rubber cross rollers (8) are interconnected.

11. The device according to claim 9, characterized in that the dryer (4) has electric heating elements and / or hot air heating devices and / or microwave heating devices.

12. The apparatus according to claim 9, characterized in that the classifier (1) has a fine-meshed sieve at its input.

13. The apparatus according to claim 12, characterized in that the sieve has a bottom with a mesh width up to the maximum permissible grain diameter for the respective application.

14. The apparatus according to claim 9, characterized in that a pressure transmitter is arranged on the classifier (1), which is connected via a controller to a servomotor for controlling the floor outlet on the classifier (1).

15. The apparatus according to claim 9, characterized in that the intermediate bulk container (3) is designed as a tub with one-sided inclined wall and overflow.

16. The apparatus according to claim 9, characterized in that the transport through the dryer (4) is realized by means of a link belt.

17. The apparatus according to claim 9, characterized in that the lamella clarifier (2a) is removably arranged on a sealing layer directly on the sedimentation basin (2b) and realizes a watertight connection.

18. The apparatus according to claim 9 or 17, characterized in that the lamella clarifier (2a) has a plurality of plates which are arranged with an inclination of 60 degrees.

19. The apparatus according to claim 18, characterized in that the plates are arranged up to about 1 to 5 cm apart and have a high surface quality.

20. The apparatus according to claim 9, characterized in that the removal device (2c) has a sensor on the bottom of the container, which detects the bottom plate deflection as a measure of the filling weight or the filling of the filter bag is indicated by a stirring sensor.

21. The apparatus according to claim 9, characterized in that a reserve tank (6) is arranged below the fine particle section and / or coarse particle section.

22. The apparatus according to claim 21, characterized in that in addition to the reserve tank (6) an additional tank fed by overflow from the lamella clarifier (2a) and / or a filter unit (9) is arranged, which are connected to the sewer.

23. The device according to claim 9, characterized in that the pumps are arranged above the cutting pool water surface and / or the AufStrom Classified 1.

24. The device according to claim 9, characterized in that a bypass (13) is arranged between the up-current classifier (1) and the lamella clarifier (2a).

25. The apparatus according to claim 24, characterized in that the bypass (13) actuating elements (11) for opening / closing the flaps (12) and an input from the cutting pool (10) and outputs to the upflow classifier (1), to the lamella clarifier ( 2a) and back to the cutting basin (10).

26. The apparatus according to claim 9, characterized in that the lamella clarifier (2a) with all connections is fixed to the frame and the sedimentation basin (2b) is lowered for emptying.

27. The apparatus according to claim 9, characterized in that the bottom of the classifier (1) is designed as a nozzle plate or as a perforated plate over which an elastic mat having slits is arranged.

28. The apparatus according to claim 27, characterized in that the mat consists of silicone or rubber.