WO2008155047A1

WO2008155047A1 - Device and method for cleaning contaminated sands

Info

Publication number: WO2008155047A1
Application number: PCT/EP2008/004632
Authority: WO
Inventors: Jan Satek; Rüdiger KAULFERS
Original assignee: Hottinger Maschinenbau Gmbh
Priority date: 2007-06-18
Filing date: 2008-06-10
Publication date: 2008-12-24
Also published as: DE102007027928A1

Abstract

Contaminated sands are cleaned by means of a cleaning fluid in a resource-saving manner, if two cleaning steps based on different cleaning principles are used sequentially, the steps being able to remove different contaminants and using similar amounts of cleaning material per unit of time, such that cleaning fluid used for cleaning in the subsequent cleaning step can be used for the preceding cleaning step.

Description

Apparatus and method for cleaning contaminated sands

description

The present invention relates to an apparatus and a method by means of which contaminated sands can be cleaned using a cleaning liquid, and in particular by how the cleaning liquid can be used as efficiently as possible. An important field of application of the present invention is the purification of core sands, such as those used to produce sand cores for metal foundries. For environmental reasons, core sands, or sand cores made from them, which are bound with inorganic binders are already being used. In contrast, conventional methods use organic binders.

Regardless of the type of binder used, in core manufacture a molding material, called "core sand", is filled into a mold having a cavity having the shape of the sand core to be formed, to provide sufficient rapid and uniform filling of that cavity , the core sand is usually introduced via a plurality of distributed openings, so-called "shot openings" in the mold. When filling in each of the firing openings, a nozzle ("firing nozzle") is introduced, through which the core sand is introduced into the cavity, which is usually carried by compressed air or pressurized gas at high speed, so that the core sand is also injected.

The core sand itself is normally stored within a closed volume on the side of the shot nozzle facing away from the mold, the so-called "shot hood." The core sand is injected into the core sand. lumen abruptly and for a short time (within about 500 ms to 800 ms) applied to a pressurized gas, which in turn is stored in a compressed gas reservoir. Due to the overpressure, the core sand is introduced into the mold, the core sand being completely penetrated by the gas, so that the majority of the gas introduced also flows through the core sand and through the firing nozzles into the mold, from which the shot gas can escape through vents.

In processes with organic binding materials, dry air is usually used as a shot gas, since these binders are hardened after introduction of the core sand into the mold by adding an activating gas. However, the use of this activating gas as well as the use of organic binders results in a non-negligible burden on the workplace or the environment, so that the development of core sands with inorganic binders, such as water glass, has been promoted. Inorganic binders cure under the influence of supplied heat, so that can be dispensed with an activating, polluting the environment gas.

The bound with organic binders sands, for example, after the cold box process, usually cleaned by thermal treatment in which the sand must be heated to temperatures above 400 ⁰ C. This is energetically extremely unfavorable and thus leads to an increase in the total cost of the process. Since the process throughputs are usually relatively high, the thermally treated sand often even needs to be cooled before it can be reused. In addition to the thermal treatment other mechanical separation methods are common, such as the screening or air classification. In the now preferred inorganic binders, a thermal aftertreatment can in principle also lead to success, but then a chemical additive would be necessary to keep the sand processable. However, the chemical additives require an extremely high temperature of the thermal aftertreatment, which must be at least 900 ⁰ C. This would increase the cost of cleaning compared to the cost of organic binder to the inefficiency of the process, since organic binders can be removed even at temperatures around 400 ⁰ C.

Instead, alternative washing or cleaning methods are proposed which can clean contaminated sand using a cleaning fluid. In turn, aspects of cost-effectiveness and environmental compatibility must be taken into account. This means, in particular, that accumulating wastewater or accumulating cleaning liquid to be thrown out of the process must not have any environmental incompatibility. In addition, the amount of wastewater or the resulting cleaning liquid should be as low as possible in order to increase the efficiency of the process. In particular, processes that do not form a cycle in which so all cleaning liquid obtained after a single use as wastewater, are disadvantageous both in terms of cost and in terms of environmental impact.

In the case of sand washing with the aid of a liquid, a suspension is typically formed between the sand and the liquid, ie the macroscopic sand particles are in a liquid-saturated environment and can thus be conveyed or moved by a liquid flow or by mechanical drives. In this state of aggregation, they can also be used with fluidic methods clean, for example, when the suspension is diluted to supply a hydro-cyclone. A hydro-cyclone is functionally similar to a centrifuge, with the hydro-cyclone designed for continuous operation. The particles present in dilute suspensions are separated in the hydrocyclone in a kind of artificial vortex, the lighter particles in a liquid rotating about the center of the cyclone not being driven out as much as the heavier particles. In the case of the cyclone, the water is sucked off both at the edge of a cylinder or cone delimiting the cyclone and in the middle of the cyclone, so that a separation of the light and heavy particles in the suspension can be achieved. The system has high dynamics, ie, the liquid flows through the cyclone at high tangential velocities, which are achieved by tangentially entrapping the diluted suspension in the cyclone at high pressures. This inevitably requires that a large amount of liquid must be used per unit time. A Hydrozyk- lon consumes a large amount of liquid per unit of time.

It is also possible to use sieves through which the suspension flows, but these are only of limited suitability for core sand washing since the impurities which occur in the core sands, such as, for example, metallic abrasion or microscopic metal particles from the casting process, have approximately the dimension of the grains of sand reliable separation and spreading of the sand by sieves alone can not be achieved.

The same applies to filters, such as plan filters or ladle filters, if they are to be used as sole filter instruments. In principle, for example, several identi ^¬ cal cleaning devices can be mounted one behind the other, for example, several hydro-cyclones. This can increase the purity of the end product, ie the degree of soiling. However, this does not solve the problem of cleaning liquid consumption.

In general, to obtain a better cleaning effect, it is advantageous to carry out a plurality of cleaning steps, wherein each cleaning step is sensitive, for example, to specific physical differences of the particles to be separated.

It is the object of the present invention to provide a concept by cleaning of contaminated sands, by means of which sands can be cleaned with the aid of a cleaning liquid with low cleaning liquid consumption.

This object is achieved by a washing device according to claim 1 and by a method according to claim 14.

The present invention is based on the finding that contaminated sands can be cleaned in a resource-saving manner by means of a cleaning solution if two cleaning stages based on different cleaning principles are used sequentially, which can remove different impurities and whose cleaning agent requirement per unit time is similar, so that cleaning liquid used for cleaning the downstream cleaning stage can be used as a cleaning fluid for the upstream purification stage.

It has been recognized that, under the above condition, the cleaning liquid already used for cleaning in the downstream purification stage is in principle can be used completely for cleaning the sand in the upstream purification stage. In addition to the approximately identical consumption of detergent per unit time of the two sequentially operated purification stages is also advantageous if the cleaning fluid further used contains particles to be removed from the upstream purification stage in only low concentration.

The arrangement of the purification stages is therefore selected in the exemplary embodiments according to the invention such that an upstream classifier is used as the upstream purification stage, at the classifying inlet of which a suspension of the contaminated sand and the cleaning liquid is introduced. The upflow classifier separates ultrafine particles from the sand suspension whose rate of descent is less than the flow rate of the countercurrently flowing cleaning liquid. The classified sand suspension cleaned by the classifier of fines is fed to the second cleaning stage, a washing device for washing the suspension of the sand. For washing, this also uses cleaning liquid and a washing principle which does not lead to any accumulation of particles in the cleaning liquid. Since the sand suspension supplied to the washing device is already freed of very fine particles, in some embodiments of the invention a washing device is used whose washing principle prevents such finest particles from being additionally generated or accumulated in the cleaning liquid of the washing device.

In some embodiments of the invention, a paddle scrubber is used as the washing device, in which the sand suspension to be cleaned in countercurrent process counter to a cleaning liquid stream mechanically transported by paddles. In some embodiments of the invention, a multi-stage paddle scrubber is used, ie a paddle scrubber which has a plurality of serially arranged paddles. By the mechanical movement of the suspension with paddles an excellent mixing of the sand suspension or the sand to be cleaned with the cleaning agent is achieved, so that the cleaning can take place on a large effective area. This has the advantage that a comparatively small volume flow of cleaning liquid is required for cleaning. In addition, a paddle scrubber uses only slowly rotating mechanical components, so that there is hardly any mechanical abrasion in the paddle scrubber itself, as would be the case, for example, with a high-speed rotating centrifuge. An enrichment of the cleaning liquid with the finest particles of material as a result of abrasion is therefore excluded. In addition, the low speed of the paddles used prevents crushing or breaking up of the sand crystals due to mechanical effects, so that no fine particles are separated from the sand to be cleaned itself, which could prevent complete reuse of the cleaning fluid of the paddle scrubber.

In addition, a paddle scrubber can be operated with small but variable amounts of detergent, since a change in the amount of detergent per unit time can be compensated by the inclination of the paddle scrubber assembly, so that the cleaning properties do not change, even if the volume flow of the cleaning liquid is increased or decreased , In particular, in this way, the paddle scrubber can be operated with volume flows which are also favorable for the operation of the on-load classifier or enable the on-load classifier, to remove fine impurities from the sand suspension reliably.

In some embodiments of the present invention, the washing apparatus is used to clean core foundries bonded to inorganic binders of a foundry. The finest impurities resulting from the handling of the core sands consist of materials of low density, so that they can be removed from the sand suspension by the upstream classifier, even if this can be operated with a low volume flow because of a low flow rate in countercurrent. The sequential use of an upflow classifier and a paddle scrubber thus advantageously work together in terms of the parameters required for their operation for the washing of sands such that on the one hand a small amount of cleaning liquid per unit time can be used, and on the other hand the one used by the paddle scrubber Cleaning liquid can be used again to supply the upstream classifier, without it comes to the accumulation of impurities by the further use of the cleaning liquid.

In some embodiments of the present invention, water is used as the cleaning liquid, and the use of the inventive concept helps to provide an environmentally beneficial cleaning of sand since only a small amount of wastewater is produced per unit time because of the arrangement of the upstream classifier and the downstream washing device, the cleaning liquid can be used multiple times in the process.

Some other embodiments of the present invention include an attritor capable of generating the suspension of contaminated sand and cleaning slurry. liquid serves. For this purpose, cleaning fluid and contaminated sand are supplied in freely determinable volume ratios of a mechanical agitator, which may be one or more stages, and which generates the suspension. In this case, in addition to the generation of the suspension by the mechanical friction of the sand particles with each other already achieved a pre-cleaning by any impurities adhering to the sand grains are partially removed by mechanical means. In the case of core sand, this is, for example, the inorganic water glass used for bonding core sands, as some water-soluble alkali silicates are called. In some embodiments of the present invention, the cleaning agent used in the attritor to form the suspension is removed from the washing device elsewhere in the process, so no fresh cleaning agent is used, which can further reduce the consumption of cleaning agent in the overall system.

In another embodiment of the present invention, the cleaning agent of the washing apparatus may be used to dilute the suspension downstream of the attritor or before the upflow classifier in order to allow the reliable operation of the upstream classifier which requires a certain minimum dilution of the material to be classified. Here too, due to the further use of the cleaning fluid of the washing device, special attention is paid to the efficiency with regard to the consumption of cleaning fluid.

In another embodiment of the present invention, the sand suspension washed by the washing device is dried by means of a dehumidifier to result in a dry, cleaned sand. In some embodiments of the present invention, that of the Dehumidifying device obtained cleaning liquid supplied to the washing device, which uses these for washing the sand, so that attention is paid here to a consistent management of the cleaning liquid in countercurrent to the material to be cleaned.

In some embodiments of the present invention, a detergent feed, so the supply of fresh, not yet used detergent into the washing device, so that it can be used by the subsequent re-use in countercurrent multiple times.

In some embodiments of the present invention, the detergent supply takes place alternatively or additionally at the material inlet of a dehumidifier, so that within the dehumidifier (for example a pusher centrifuge) a trouble-free material transport is ensured. The cleaning liquid recovered from the dehumidification can then be used in countercurrent, for example to supply the washing device on.

In some embodiments of the present invention, newly added cleaning fluid is heated to temperatures above ambient temperature prior to introduction into the washer, which increases cleaning performance as water-soluble components or impurities dissolve more quickly. Thereby, although energy is to be used to heat the cleaning liquid, the total energy balance can still be positive if the flow rate of the cleaning liquid can be countercurrently reduced thereby resulting in a further reduction in the need for cleaning liquid. Further embodiments of the present invention will be explained below with reference to the accompanying drawings. Show it:

Fig. 1 shows an embodiment of a washing device;

Fig. 2 is a schematic representation of an embodiment of a washing device;

3 shows a schematic illustration of a further embodiment of a washing device for cleaning contaminated sand;

4 shows a further embodiment of a washing device for cleaning contaminated sand; and

Fig. 5 is a schematic representation of a method for cleaning contaminated sand.

FIG. 1 shows an exemplary embodiment of a cleaning device for cleaning contaminated sand 10, which comprises a flow classifier 12 and a paddle scrubber 14.

The upstream classifier 12 is formed by a container 16 filled with cleaning fluid, which has a classifier 18. The classifying installation is partially separated from the remaining volume of the container 16 by a partition wall 20 and consists essentially of an overflow 22 and an installation 24 which allows controlled introduction of the suspension of contaminated sand into the classifying installation 18. The upstream classifier 12 further has a detergent inlet 26 and a kierating outlet 28 through which the sand suspension can be removed after classification (floating particle liberation). The supply of cleaning liquid takes place on the side facing away from the classifying 18 side of the partition wall 20 so that set the required for classification flow conditions within the vessel. Depending on the added amount of cleaning liquid per unit time on the cleaning liquid inlet 26 is formed in the classifying 18 an upward flow, so that permanently drains through the drain 22 cleaning liquid. The flow rate is now adjusted so that it is higher than the rate of descent of the particles to be separated in the cleaning liquid. While the sand whose rate of descent is higher than the set flow rate, sinks to the bottom of the container 16 and can be removed there via the Klassierausgang 28, the particulate matter and other light impurities are discharged via the outlet 22 controlled. Are cleaned by the washing device 10 core sands, which are bound with inorganic binder, the effluent via the drain 22 cleaning liquid due to the ecological safety of the binder used (for example, water glass) in the public

The sand suspension taken from the classifier exit 28 is fed by a suitable conveyor to a material supply 30 of the paddle scrubber 14 so that in the paddle scrubber it passes to a first paddle 32a of a plurality of paddles 32a-32e sequentially arranged to receive the sand suspension to transport against gravity and against the flow direction of the cleaning liquid. The sand suspension is successively conveyed into different pans assigned to the respective paddles 32a-32e whose radius corresponds to the radius of the paddles. From the last delivery paddle 32e, the sand suspension enters the material exit 32 of the Paddle washer 14 transported. The cleaning liquid is added through a cleaning liquid inlet 34 of the paddle scrubber 14, so that the cleaning liquid, under the influence of gravity, flows against the flow of the sand suspension from the delivery paddle 32e to the delivery paddle 32a to leave the paddle scrubber 14 at a cleaning liquid outlet 36. The freely adjusting parameters of the paddle scrubber 14 include on the one hand the amount of material supplied per unit time, the amount of supplied cleaning liquid per unit time and the slope of the conveyor line, so that angle of a connecting line between the axes of the paddle 32a - 32e and an imaginary being trapped in the direction of the gravity line.

In order to carry out the cleaning of the sand as sparingly as possible, the cleaning liquid outlet 36 of the paddle scrubber 14 is connected to the cleaning agent inlet 26 of the flow classifier 12 such that the cleaning liquid of the paddle scrubber 14 used during washing can at least partially enter the flow classifier 12. In principle, the entire amount of cleaning fluid obtained at the cleaning fluid outlet 36 of the paddle scrubber 14 can be forwarded to the cleaning fluid inlet 26 of the supercharger classifier 12 since the detergent consumption of the supercharger classifier and the paddle scrubber can be adjusted to be approximately identical is. The use of the paddle scrubber as a washing device has the advantage that it can be operated with comparatively small amounts of cleaning liquid, which, in synergy with the use of the power classifier, results in only a very small amount of new cleaning fluid being added to each kilogram of sand to be cleaned must become. The amount of fresh cleaning fluid per kilogram Sand, for example, may be so low that it lies in an interval between 0.5 l / kg and 4 l / kg. This is only possible if the successive operated washing devices can be operated so that they can be operated with optimal cleaning effect with a similar amount of liquid.

For example, if a hydrocyclone were to be used instead of the paddle scrubber 14, the synergistic effect would not be achieved because the hydrocyclone has a high minimum cleaning fluid requirement due to the high flow rates required so that the cleaning fluid used for the hydrocyclone will not be fully utilized as the feed to the upstream classifier can not be used because of the high levels of cleaning liquid provided by the hydrocyclone for the separation of sand and fine dust or Feinstteilchen. A large part of the cleaning liquid would therefore have to be removed as wastewater, which would significantly worsen the overall eco-balance of the process. In principle, although a portion of the cleaning liquid used by the hydrocyclone could be returned to its own input, but then inevitably an accumulation of non-removable hydrocyclone impurities in the circulation or in the cleaning liquid, which would lead to a deterioration of the overall result or the purity of the device can carry washed sand.

Moreover, the combination of a top classifier 12 and a paddle scrubber 14 shown in Figure 1 has the advantage that the sand washing or the regeneration of the sand is achieved by methods which only cause extremely low mechanical stress on the sand to be cleaned. Therefore, only a little Sand produced as broke, for example, by mechanically crushing the sand grains below the minimum required grain boundary, so that with some embodiments of the invention, sand recycling rates of 90% or even 95% and above can be achieved.

2 is a block diagram schematically showing an embodiment of a scrubbing apparatus 10 for cleaning contaminated sand which is supplied to an upflow classifier 12 at a classifying inlet 25 in the form of a suspension of contaminated sand and a cleaning liquid. The upflow classifier further has a detergent inlet 26, at which the cleaning agent is introduced into the upflow classifier.

The pre-cleaned material obtained at a classifying outlet 28, the classified sand suspension, is fed to a washing device for washing the sand suspension 14 via a material feeder 30. The washing device 14 also has a cleaning liquid inlet 34, via which the washing device 14 is supplied with cleaning liquid. A cleaning liquid outlet 36 of the washing device is connected to the cleaning liquid inlet 26 of the upstream classifier 12 in such a way that the cleaning liquid of the washing device 14 used during the washing at least partially reaches the cleaning liquid inlet 26 of the flow classifier 12 in order to minimize the amount of cleaning liquid consumed to keep.

Fig. 3 shows a block diagram of a scrubber for cleaning contaminated sand 10 in the context of the entire process cycle as it is being run through a foundry for processing core sands. The core sand is initially stored in a sand bunker or held in stock, as can be seen from the process step 50. For the core sand mix 52, the already-reclaimed core sand is mixed with any required new sand, binders and any optional activators that may be required to obtain a core sand mix suitable for producing sand cores made by conventional processes in a production step 54. After a casting process 56, the sand cores located inside the castings are crushed and removed from the casting in a coring step 58. For this purpose, the casting can be vibrated, for example, so that the sand cores located in the interior part can break open and can be removed from the casting by shaking or by washing. In a comminution step 60, these sand core fragments are fed to a crusher, which reduces them to approximately identical size, whereupon the crushed sand core fragments are temporarily stored in a sand silo in a storage step 62, from where they are fed to the actual treatment or washing.

In this case, an attritor 64 can optionally be arranged in front of the washing device 10, which serves to produce a suspension of the contaminated core sand and a cleaning liquid, for example water. For this purpose, the core sand together with the cleaning liquid in an optional multi-stage, Rühereraufbau is given in which the cleaning liquid is mixed together with the contaminated core sand, so that the suspension of contaminated core sand and cleaning liquid forms. The core sand is almost crushed to particle size and there are already first impurities that adhere mechanically to the core sand, separated from this. The sand suspension is fed from the attritor 64 into a washing device 10, as described, for example, with reference to FIG. 2 was explained. To avoid redundancy, therefore, a detailed description of the upstream classifier 12 and the washing device 14 is omitted.

Incidentally, applies both here and in the entire context of the invention disclosure that functionally identical or functionally similar components are provided with the same reference numerals and that the description of the relevant components in the different embodiments should be mutually applicable.

It is also important here that the washing device 14 has a cleaning liquid outlet 36 which is connected to a detergent inlet 26 of the upflow classifier 12 in such a way that the cleaning liquid of the washing device 14 used during washing can at least partially enter the upstream classifier 12. Additionally, optional cleaning fluid may be added from a cleaning fluid exit 66 of the upstream classifier to the attritor 64 to form the sand suspension along with the sand. Furthermore, the attritor 64 may have a waste water outlet 68, via which, for example, sludge, which forms from fine particles in conjunction with the cleaning liquid in the attritor, may be discharged as waste water. This can, as shown in FIG. 3, be supplied together with the waste water from the overflow 22 of the upflow classifier 14 to a wastewater treatment 70, which can separate off parts of the cleaning liquid, for example by sedimentation or further classification, to obtain sludge and cleaning liquid to be dumped in the end result or to obtain wastewater. In the process shown schematically in FIG. 3, the sand suspension after the washing device 14 is fed before drying to a PAN filter 72 which, with the addition of fresh cleaning liquid, leaves a filtration of the sand suspension from the washing device 14 may make a cleaning liquid reservoir 72, to obtain in the final result as a filter cake a cleaned, pre-dried sand, which is a drying / cooling device 76 is supplied. The filtrate of the PAN filter, or the filtrate later filter stages of the PAN filter 72 can in turn be supplied to a cleaning liquid inlet 34 of the washing device 14 in countercurrent, since this is only slightly contaminated in the PAN filter 72. Here, too, the concept of taking consistent water flow countercurrently into account again takes into account the positive effect on the overall balance of cleaning fluid consumption.

The filter cake of the PAN filter, so the still moist cleaned sand is fed to a drying / cooling unit 76, which dries the wet sand for reuse. When the drying is carried out with heat input, the sand is then cooled, so as not to cause premature curing of the core sand mixture, when the inorganic, thermosetting, binder is supplied to it (for example, water glass). The cooled, cleaned sand may be subjected to optional fine dust screening through a sieve length 78 should this be required. The Siebanlange could for example be an air classifier, the dust removed by means of the screen 78 dust is disposed of as waste product. The re-sieved sand or the sand after processing by the cooling / drying unit 76 is the sand bunker 50 is supplied to be reused in the further course of the process for core production.

As can be seen in the concept shown in FIG. 3, care is also taken here to consistently guide the cleaning liquid countercurrently to the sand to be cleaned. That is, fresh cleaning fluid will added only in the last purification step. From there, contrary to the sand flow, that is to say in countercurrent, the cleaning liquid which was used for cleaning is for the most part transferred to the cleaning liquid inlet of the preceding cleaning device, so that no further fresh cleaning liquid is added until the first cleaning step of the sand (the attrition 64) must become. As a result, the cleaning liquid or the water used for cleaning is used as efficiently as possible, so that it is possible to bring the detergent consumption per kilogram of sand to be cleaned to below 4 liters.

4 shows a more detailed view of another embodiment of the present invention based on the attritor 64, power classifier 12, and paddle scrubber 14 components already described with reference to FIGS. As can be seen in FIG. 4, the attritor 64 has a two-stage design. The attritor holds at its Attritoreingang 80 both the sand to be cleaned and for cleaning (as a cleaning liquid) used water from a return container 82. At the Attritorausgang a suspension 84 of the sand and the cleaning liquid in the classifying input 25 of the power classifier 12 is given. In order optionally to improve the material flow of the sand suspension, water from the return container 82 can additionally be mixed with the sand suspension supplied by the two-stage agitator of the attritor 64 via a valve 86 to ensure a continuous supply to the upstream classifier 12 or to set a dilution for proper functioning of the upflow classifier 12 is required. The cleaning agent inlet 26 of the upstream classifier 12 is connected to the return container 82 via a valve HB, so that the cleaning agents required for operation of the upstream classifier 12 tion liquid or the required water can be completely removed from the return container 82.

The overflow 22 of the upstream classifier 12 is connected to a sump 90. The classifier exit 28 of the upstream classifier 12 is connected to a screw conveyor 92 to convey the sand suspension from the upstream classifier or classifier exit of the upstream classifier to the material supply 30 of the paddle scrubber 14. In this case, the conveying speed can be arbitrarily set by varying the rotational speed of the conveyor spindle and adapted to the conditions or the required throughput of the apparatus.

The purge fluid exit 36 of the paddle scrubber 14 is connected to the recycle bin 82 so that all of the water used by the paddle scrubber 14 for purification is collected in the recycle bin 82. Should the capacity of the return tank 82 be exceeded, water is transferred from the return tank 82 to the sump 90 via a line 94. The material outlet 32 is connected to a collection container 96, which serves to feed the washed sand suspension to a further conveyor screw 98. The sump 96 further includes an excess water overflow 100 which is connected by a conduit to the recycle tank 82 for countercurrently recycling the clean excess water to the washed suspension of sand; H. the attritor or upstream classifier.

By means of a further conveyor screw 98, the washed sand suspension is transferred to a pusher centrifuge 102, wherein here, too, the rotational speed of the further conveyor screw 98 is continuously adapted to the amount of sand to be cleaned per unit time can be. Fresh water from a fresh water reservoir 106 may also be added to an entrance 104 of the pusher centrifuge to prevent the pusher centrifuge 102 from being prevented from functioning properly by too thick a sand suspension. In this case, the amount of fresh water to be added can be regulated via a metering valve 107. Via a material outlet 108 of the pusher centrifuge 102, the cleaned and predried sand can be fed to a dryer.

The condensate of the pusher centrifuge 102, that is, the water obtained by the centrifuging is passed into a buffer 110. The buffer 110 thus contains hardly any contaminated fresh water. This is used to carry out the washing of the sand in the paddle scrubber 14. For this purpose, the cleaning fluid inlet 34 of the paddle scrubber 14 is connected to the intermediate reservoir 110 via a valve arrangement 112. If there is insufficient liquid in the intermediate reservoir 110 to operate the paddle scrubber 14, additional fresh water from the fresh water reservoir 106 can be admixed via the valve arrangement 112 in order to provide the liquid quantity required for operating the paddle scrubber. The introduction of fresh water into the process takes place in the example shown in Fig. 4 only at one position, namely at the beginning of the counterflow, so process flow at the end of the washing process of the sand in the fresh water reservoir 106. For safety reasons, the fresh water reservoir 106 is equipped with an overflow outlet 114 in that, when the maximum liquid level in the fresh water reservoir 106 is reached, the fresh water is transferred via the overflow into a waste water line 116 in order to prevent an uncontrolled overflow of the fresh water reservoir 106. Apart from the also provided for the intermediate reservoir 110 overflow mechanism is the Sewer 116 fed exclusively from the reservoir 90. That is, the waste water is removed during normal operation only at the end of the countercurrent, so that as little fresh water must be added, since the once added fresh water can be used in countercurrent successively for all cleaning stages used. This is possible in particular because the water-intensive cleaning steps, the laundry by means of the paddle scrubber 14 and the stream classification are coordinated with one another such that they require approximately the same amount of liquid per unit of time.

Fig. 5 shows schematically in block diagram form an example of a method for cleaning contaminated sands using a cleaning liquid. In a washing process 200, a classified sand suspension is washed with a cleaning liquid. In a classifying step, a sand suspension is classified using at least portions of the cleaning fluid used in the washing to produce the classified sand suspension.

Although in the preceding paragraphs and with reference to the figures, a washing apparatus has been described predominantly in which an on-current classifier is combined with a paddle scrubber, the use of a paddle scrubber in combination with an up-stream scrubber is not a prerequisite for a successful implementation of the inventive concept. Rather, any other washing device that achieves a washing effect using the cleaning liquid may be used, and the amount of cleaning liquid to be used to achieve the desired result may be adjusted to the consumption of the size classifier to achieve approximately complete reuse of the used for washing Cleaning fluid to operate the Aufstromklas- sierers to reach.

Likewise, in some embodiments optional attrition is not mandatory to enable resource efficient cleaning of sand. Instead of an attritor, it is possible, for example, to use any other suspension device which is suitable for producing a suspension or a dilution from the sand to be cleaned and a cleaning liquid which can be further treated by means of an upflow classifier. This may, for example, be a conventional mixer or obtained by mixing sand with a high pressure water jet to form a non-saturated suspension, which may become a saturated suspension by subsequent brief sedimentation should this be required be .

The further filtering or cleaning steps described after the application of the washing device or the cleaning device described in some embodiments are optional and can also be omitted without significantly degrading the result due to the high cleaning effect of the combination of upflow classifier and downstream washing device.

Claims

claims

A cleaning device (10) for cleaning contaminated sand using a cleaning fluid, comprising:

an upstream classifier (12) having a classifying inlet (25) for a suspension of the contaminated sand and the cleaning liquid, a cleaning agent inlet (26) and a classifying outlet (28) for a classified sand suspension; and

a washing device (14) for washing the classified sand suspension with a material feed (30) for the classified sand suspension, a cleaning liquid inlet (34) and a cleaning liquid outlet (36) connected to the detergent inlet (26) of the upstream classifier (12) It is associated with the fact that the cleaning fluid used during washing can at least partially reach the upstream classifier (12).

2. Cleaning device (10) according to claim 1, which uses water as a cleaning liquid.

3. cleaning device (10), wherein the cleaning liquid outlet (36) of the washing device (14) with the detergent inlet (26) of the upstream classifier (12) is connected such that at least 80% of the washing liquid used in the washing device in the detergent input (26) of the upstream classifier (12).

4. Cleaning device (10) according to one of the preceding claims, in which the cleaning agent inlet (26) of the flow classifier (12) is spatially adjacent to a classifying insert (18) of the Auflass- _S tromklassierers (12) is arranged, in which the cleaning agent flows with a required for classification flow.

5. Cleaning device (10) according to one of the preceding claims, wherein the washing device (14) is a paddle scrubber.

6. Cleaning device (10) according to claim 5, wherein the paddle scrubber serially arranged several

Paddle for promoting the classified sand suspension has.

7. Cleaning device (10) according to one of the preceding claims, further comprising a dehumidifying device (102) for dehumidifying a sand suspension washed by the washing device (14), the dehumidifying device having a cleaning liquid outlet which communicates with the cleaning liquid inlet (34). the washing device (14) is connected such that the cleaning liquid of the dehumidifying device (102) at least partially into the cleaning liquid inlet (34) of the washing device (14) can pass.

8. Cleaning device (10) according to claim 7, further comprising a Reinigungsmittelzuführeinrichtung to supply the cleaning device (10) new cleaning liquid, the Reinigungsmittelzuführeinrichtung is connected to a material inlet (114) of the dehumidifier (102) that the new cleaning liquid at least partially into the material inlet (114) of the dehumidifier (102) can pass.

9. cleaning device (10) according to any one of claims 1 to 7, further comprising a Reinigungsmittelzuführeinrichtung to the cleaning device (10) supply new cleaning liquid, the Reinigungsmittelzuführeinrichtung is so connected to the cleaning liquid inlet (34) of the washing device (14), the new cleaning liquid at least partially in the cleaning liquid inlet (34) of the washing device (14) can pass.

10. Cleaning device (10) according to one of the preceding claims, further comprising a suspension device (64) with a cleaning liquid inlet and a sand inlet to produce the suspension of the sand and the cleaning liquid.

11. Cleaning device (10) according to claim 10, wherein the suspension device is an attritor.

12. Cleaning device (10) according to claim 11, wherein the attritor has a plurality of stirrers.

13. Cleaning device (10) according to one of claims 10 to 12, in which the cleaning liquid inlet of the attritor (64) is connected to the cleaning liquid outlet (36) of the washing device (14), the cleaning liquid of the cleaning liquid outlet (36) of the washing device ( 14) can at least partially reach the cleaning liquid inlet of the attritor (64).

14. Cleaning device (10) according to one of claims 10 to 13, wherein the cleaning liquid outlet (36) of the washing device (14) connected to the classifying input (25) of the onstrus Classierers (12) or to an output of the suspension device (64) is that the suspension of the contaminated sand and the cleaning liquid with further cleaning liquid of the cleaning liquid keitsausgangs (36) of the washing device (14) can be diluted.

15. Cleaning device (10) according to one of the preceding claims, further comprising a heating device for heating the cleaning fluid to a temperature above the ambient temperature.

16. A cleaning device (10) according to claim 15, wherein the heating device is adapted to heat the cleaning liquid to a temperature of 50 ⁰ C or more.

17. A method of cleaning contaminated sand using a cleaning fluid, comprising the steps of:

Washing a classified suspension of the sand and the cleaning liquid using the cleaning liquid; and

Classifying a suspension of the contaminated sand and the cleaning liquid to obtain the classified suspension of the sand and the cleaning liquid, wherein at least parts of the cleaning liquid used in the washing are reused in classifying.