EP0917921B1 - Method and apparatus for reclaiming core sand or mould sand - Google Patents

Abstract

The installation for recovery of foundry sand from moulds or mould parts includes a recovery chamber (3) and a cooling chamber (4). A hot fluid bed (32) consisting essentially of heated foundry sand (16) suspended by gas flows is generated in the recovery chamber which is supplied with sand moulds and mould parts (37). The cooling chamber houses an analogous fluid bed (33) consisting of cooled foundry sand (16') transferred from the recovery chamber by a transfer device (34).

Description

The invention relates to a method and an apparatus for Recovering reusable core or molding sand Pieces of used cores or shapes as well as from contaminated Used sand from foundries. Such a system works for example from US-A 3 976 422 as known. The the prior art known therefrom is in the genus formation of independent claim 1 (procedure) or of the independent Claim 12 (device) used as a basis.

Sand molds are generally used in the production of castings and / or sand cores from bound quartz sand are used. After the castings have solidified, they are shaped and cored, leaving the sand in more or less large fragments bound sand and - as far as the grains of sand themselves detached individually from the fragments - in the form of individual, Grains of sand coated with binder are present. Besides, is the old sand in small quantities with others from the foundry Residues contaminated, e.g. with oxidized metal beads due to metal splashes, with metal chips and Burr remnants from cast iron cleaning. Also fall in the foundry water-wet sand sludge when quenching castings or Lumps of sand mixed with uncured synthetic resin binder on. The latter arise as a committee during core production and cleaning a core shooter. Furthermore, there is the danger it cannot be ruled out that other wastes that are everywhere, where people stay, occur, in individual cases in can get used sand, e.g. Beverage bottles or cans, paper, pieces of wood, plastic parts, textile residues, Pieces of wire, plant remains and the like.

Although new quartz sand is relatively inexpensive, so that replacement costs the relatively high cost of one Sand regeneration would not be economically justified. However, the Altand, which comes from foundries, must be disposed of as hazardous waste Expensive to dispose of, with landfill costs both replacement costs as well as regeneration costs exceed by a multiple. So sand regeneration is only because of the high and even increasing disposal costs in the future economically worthwhile. Added to that is that regenerated Sand at least in the usually downstream Size classification a narrower range of grits Has. In addition, the individual grains of sand are regenerated Used sand rounded due to repeated treatment, whereas the grains of new sand are broken and angular. These two Properties - about uniform grain size and rounded Grains of sand - together result in better air permeability the molds or cores made from it, what for the casting process is cheap. The sand regeneration offers next to one Cost advantage also a casting advantage.

To reuse the old sand accumulated in a foundry To date, one has had complex and multi-stage reprocessing plants used because of the high investment costs and the complicated procedure only for large foundries with high sand throughput and good trained operating personnel were economically justifiable. For smaller foundries with lower sand throughput these investments are not worthwhile; also stands this often not what is required for such complex process plants, qualified operating personnel available.

In the well-known large plants for the regeneration of old sand Incidentally, no coarse, alien particles such as pieces of metal or the like. contained in the old sand to be processed be because this leads to sensitive disruptions in the process flow leads. Likewise, no water-wet sand sludge and no lumps of binder wet get into the old sand regeneration; these also cause interference. It must accordingly the loose old sand and the core and form bridges carefully collected and in shielded conveyor systems to the regeneration system be brought, contamination with the above mentioned disruptive waste and wet sand mixtures conscientiously must be avoided. This sets one on in-house Organizational and logistical level to be solved Problem which large companies with a more in Streamlined and streamlined in the direction of series production Mastering manufacturing more easily than smaller ones and medium-sized companies, whereby here again the production volume oriented cost / benefit aspects come into play.

In the well-known large plants for the regeneration of old sand the separately collected form and core bridges are first mechanically to a particle size of about 3 to 5 mm crushed and this semolina together with the rest, free-flowing Used sand entered in the actual old sand regeneration. In its first stage, this consists of a flat, extensive fluidized bed of about 15 cm depth, which is operated at about 800 ° C. At these high Temperatures not only find an intense gasification of the organic Binder of the sand instead, it will also be cheap thermal requirements for a prescribed, at thermal afterburning taking place at even higher temperatures of the resulting gasification products. by virtue of the highly differentiated and extensive training Such large plants, it is not very easy, the process exhaust at all stages of the process to fully capture treat them properly and then into the atmosphere to be able to fire. Therefore the fluidized bed and also the subsequent cooling must be completed so that no exhaust gases out of the fluidized bed or the cooling section into the Environment can reach. This is the case with the well-known large-scale plants especially when loading the fluidized bed and when Removing the treated sand is problematic and only with one to solve complex and sensitive lock technology. The hot sand is only allowed during treatment and cooling are conveyed in closed lines or conveyor systems.

After the cleaned sand can only be reused when cold can be, the regenerated but still hot molding sand cooled to about room temperature before reuse become. For this are in the known large-scale plants voluminous and multi-stage heat exchanger systems provided, where the sand comes in through bundles of vertical pipes Gravity direction trickles through, the individual tubes in turn in the different cooling stages of different Coolant flows around. To in such heat exchanger systems the sand of initially 800 ° C in a reasonable Throughput time at least approximately down to room temperature to be able to cool, you need large heat exchanger surfaces in different cooling levels. This can only be done in extensive Realize systems that are correspondingly expensive and also cause high operating costs.

• Der Altsandanfall je Zeiteinheit liegt bei einer gewissen Mindestmenge, die nur bei Großgießereien, nicht jedoch bei kleineren und mittelständischen Betrieben erreicht wird.
• Der Altsand ist vorsortiert oder getrennt gesammelt, gegebenenfalls von etwaigen artfremden Stoffen und Partikeln befreit und enthält insbesondere keine wassernassen oder bindernassen Sandklumpen.
• Der Form- und Kernbruch wird vor der Sandregenerierung mechanisch auf eine rieselfähige Partikelgröße vorzerkleinert.

With the known large-scale plants for the regeneration of used sand, foundry used sand can be regenerated with economically justifiable effort, but only under the following conditions:

• The amount of waste sand per unit of time is a certain minimum amount, which is only achieved in large foundries, but not in small and medium-sized companies.
• The used sand is pre-sorted or collected separately, possibly freed of any foreign substances and particles and in particular contains no water-wet or binder-wet lumps of sand.
• The shape and core break is mechanically shredded to a free-flowing particle size before sand regeneration.

In addition to these, sometimes only with increased investment or The known requirements contain the requirements that can be met by personnel Due to their size, plants have certain approval requirements Problems that are small and medium-sized Companies shy away from the fact that the large plants would be oversized for them.

The above-mentioned US Pat. No. 3,976,422 shows a system for the regeneration of resin-containing core or molding sand of foundries compared to sand regeneration plants is small and compact for large foundries. In the out of this Font known compact system are in a common housing three chambers, namely a preheating chamber, a combustion chamber and a cooling chamber, through which the to be regenerated Sand is passed through one after the other and in which it is kept fluid using a fluidized bed. The combustion chamber and the cooling chamber are arranged next to one another at approximately the same height, whereas the preheating chamber is above these two Chambers extending across both. The fluidizing air the two lower chambers pass through the bottom of the preheating chamber as the fluidizing air there, the contained therein Heat is given off to the sand in the preheating chamber. The sand passes horizontally through the preheating chamber Direction corresponding to the direction of flow through the combustion chamber and directed in the opposite direction through the adjacent cooling chamber is. The cold sand in the area above the cooling chamber takes off So the waste heat from the cooling chamber, whereas the so moderate preheated sand now above the combustion chamber Waste heat from the fluidization air and the exhaust gases from the combustion chamber records and is strongly heated by these. On the of the cooling chamber facing away, approximately congruent outside from the preheating and combustion chamber the preheated trickles Sand through a bottom slot that can be controlled in cross section The preheating chamber descends vertically into the combustion chamber. The preheated fluidization air supplied from the bottom becomes a preheated fuel mixture for a support fire fed through which the binder resin is burned. The The combustion chamber and the cooling chamber are thermally insulated Partition wall separated from each other, which is the height of the fluidized bed exceeds. In the partition are near the floor and in Distance to the ground through openings arranged through the the cleaned but still hot sand from the combustion chamber into the Cooling chamber overflows. There are various heat exchangers in the cooling chamber arranged, over which heat is extracted from the hot sand can be. The fuel can flow through two of these heat exchangers or the fluidizing air of the combustion chamber are preheated. Another, near the bottom and the outlet The heat exchanger arranged in the cooling chamber can remove the sand further heat is removed and dissipated to the outside.

• separat von wassernassem und bindernassem Sand trocken gesammelt werden muß,
• von metallenen und organischen Fremdpartikel gereinigt werden muß und
• mechanisch auf rieselfähige Partikelgröße vorzerkleinert werden muß.

A disadvantage of the compact system for core sand regeneration known from US Pat. No. 3,976,422 is that, for trouble-free operation, the old sand and the core and mold fragments are complex, as is the case with large systems

• must be collected separately from water-wet and binder-wet sand,
• must be cleaned of metallic and organic foreign particles and
• must be mechanically pre-shredded to free-flowing particle size.

In the known compact system, the addition device is as Injector and the controllable transfer opening from the preheating chamber formed in the combustion chamber in the form of a narrow slot. Both on the addition device and on the The feed material must be cleaned of foreign particles and pre-shredded to flowable particle size the addition device or transfer opening also in continuous use can happen without interference. Everything about particles entered in the compact system at the entry point must pass through all openings and chambers and - apart from the exhaust gases from the burned binder resins - on exit the outlet opening. There is no removal option for removing foreign particles from the process. Therefore, the sand given in must not be coarser and gas or combustion-resistant particles such as metal Plaster residues, broken glass or the like. contain. such Foreign particles could and would accumulate in the system sooner or later disrupt the process. The one for regeneration Used sand that can be processed in the known compact system So - as I said - not only be pre-shredded, but also no larger organic particles such as paper, textiles, Pieces of wood or plastic parts as well as lumps of water-wet or binder-wet, uncured sand contain.

The object of the invention is a method and an apparatus for the regeneration of old foundry sand, with whichever of smaller quantities of used sand is economical can be regenerated and rewarded with the also rough shape and core breakage as well as heavily contaminated Used sand without any pretreatment or pre-selection can be treated.

This task is based on the generic method or the generic device according to the invention by the characterizing features of claim 1 (method) or by the characterizing features of claim 12 (device) solved.

• Zerlegen der Form- und Kernbruchstücke in einzelne Sandkörner,
• thermisches Dekontaminieren des Altsandes von Wasser, von ausgehärtetem sowie unausgehärtetem Binderharz und auch von artfremden Partikeln aus organischer Substanz,
• Selektieren und Zurückhalten resistenter Partikel, die sich im Bodenbereich des Heißwirbelbettes sammeln und von dort entnommen werden können.

The following processes are then carried out simultaneously in a single process step and locally combined in a deep hot fluidized bed:

• Breaking down the form and core fragments into individual grains of sand,
• thermal decontamination of the old sand from water, from hardened and uncured binder resin and also from foreign particles made of organic matter,
• Select and retain resistant particles that collect in the bottom of the hot fluidized bed and can be removed from there.

Through the targeted concentration of activities or processes in a procedurally unproblematic, deep hot work bed finds a complete cleaning of the untreated and unsorted old sand and core breakage in one Step instead. The concentration of features according to the invention on a hot fluid bed is the cause of the simplicity of the Regeneration plant. Thanks to the simplicity of the invention Process equipment requires it - based on the unit of time enforceable amount of sand - only relatively low investment costs and therefore also works at comparative low volume flows profitable. Because of the simplicity of the Plant and the integrated selection of resistant foreign particles the system is also contaminated with various types Used sand finished without problems. It does not make high demands to the operating personnel. The concentration of features according to the invention is used for sand regeneration Completely new for smaller flows and without any Role model in the state of the art.

Fig. 1

eine bevorzugte Bauform der erfindungsgemäßen Vorrichtung in schematischer Darstellung und größtenteils im Längsschnitt und

Fig. 2

in perspektivischer Einzeldarstellung einen Ausschnitt einer besonders effektiven Ausgestaltung von mit einer Beheizungseinrichtung kombinierten Ausströmermitteln.

Expedient embodiments of the invention can be found in the subclaims; otherwise, the invention is explained below with reference to an embodiment shown in the drawing; show:

Fig. 1

a preferred design of the device according to the invention in a schematic representation and largely in longitudinal section and

Fig. 2

a perspective individual representation of a section of a particularly effective embodiment of outflow means combined with a heating device.

The recovery device 1 shown in the drawing comprises a container 2 in which two lying side by side Chambers are formed, namely a recovery chamber 3rd and a cooling chamber 4.

In particular, the container 2 has a bottom 5 in the embodiment of rectangular plan, of which four Rise up sidewalls that delimit an interior space 7. By doing Interior 7 is located starting from the floor 5 upwards protruding partition 8, which are between two opposite Side walls extends so that the interior 7 in the two chambers 3, 4 is divided.

For the top of the container there is one on the side walls 6 overlying ceiling wall 12 provided, among other things by two lids 13, 14 is formed, each one of the chambers 3, 4 cover completely or partially removable. In the figure 1 shown closed position of the lid 13, 14 is the interior 7 completely closed to the environment. To one of the To make chambers 3, 4 accessible, the cover 13, 14 remove so that an upward opening is exposed becomes. The type of cover 13, 14 is arbitrary, with the embodiment Sliding covers are provided, which become the Move opening and closing horizontally according to double arrows 15 to let. The possibility of being largely complete Expose the top of at least the recovery chamber should be used to drain the below described Sieve basket 54 may be given. In addition, the top needs the Recovery chamber for ongoing refilling not to be fully exposed with material to be treated. To it suffices if the sliding lid 13 has a filling opening contains, which by an integrated, e.g. counterbalanced Filling flap is closable, which by hitting The filling material opens automatically.

The side walls 6, the bottom wall 5 and the partition 8 are as far as they enclose the recovery chamber 3, good heat insulation trained to heat loss of the heated To keep the hot fluidized bed as low as possible and to keep the Surface temperatures on the outer surfaces of the recovery chamber on easily tolerable and harmless Reduce values. The same applies analogously to the lid 13 of the recovery chamber with the exception of one if necessary integrated filler flap. heat loss in the area of the lid are harmless, because the ones there Exhaust gases already have their effect in the hot fluidized bed to have. In the area of the cooling chamber 4, the side walls, the bottom and the lid of simple, i.e. nichtwärmeisoliertem Steel sheet exist, because here in anyway Molding sand contained heat should be dissipated and because of the reduced temperature of the molding sand in the cooling chamber do not expect dangerous temperatures is.

First outflow means 17 are located in the recovery chamber 3 provided that dip into the associated molding sand filling 16 and are surrounded by it on all sides. Comparable Ways are in the cooling chamber 4 from the molding sand filling there 16 'enclosed second outflow means 18 are provided. Via the outflow means 17, 18 is in the associated molding sand fillings 16, 16 'compressed fluidization air can be introduced.

The outflow means 17, 18 are preferably in a suitable distribution laid pipe body 22, 22 ', the Interior according to arrows 23 from outside the container 2 compressed fluidization air is supplied, which then in the respective chambers 3, 4 through the outflow openings 24 according to arrows 25 and into the relevant sand fillings 16, 16 'occurs.

The two outflow means 17, 18 become independent of one another fed with compressed fluidization air. So they stand first outflow means 17 with an outside of the recovery chamber arranged compressor 26 in connection, wherein in the connection also outside the recovery chamber 3 arranged heater 27 is interposed. The aforementioned components together form a hot air generator 28, the hot air by means of the first air outlet means 17 feeds into the molding sand filling 16 of the recovery chamber 3. The air temperature can at least 550 ° C to 600 ° C amount on the immediate heating element. The actual temperature of the hot fluidized bed is due to certain heat losses somewhat lower and is e.g. 490 to 530 ° C. This Temperature is below the combustion temperature the pyrolysis of binders and accompanying organic substances Formsandes emerging gasification products, so that it is not too a spontaneous combustion of the exhaust gases, quite apart that the concentration of the combustible gas components in the exhaust air for permanent, self-sustaining combustion would be too small.

The second outflow means 18 are connected to an outside of the Cooling chamber located compressor 26 coupled. From him compressed fluidizing air is passed through the second without heating Air outlet means 18 into the molding sand filling 16 'of the cooling chamber 4 initiated and has the task that in the cooling chamber cool the fluidized molding sand to about room temperature. The temperature of the air introduced should be at least around ambient temperature or below. if necessary can easily add an additional cooling device in the form of a performance-based need Refrigeration unit are provided, which the cooling gas on a cools down lower temperature. It is also conceivable to be targeted and needs-based liquid air in a heat-insulated Storage container is provided in the pre-compressed Injecting fluidizing air so that it is low To cool down temperatures.

During operation of the recovery device 1 forms within of the two chambers 3, 4 by the infeed according to arrows 25 Fluidizing air from a fluidized bed, the individual Grains of sand from the molding sand 16, 16 'in a kind of suspended state are displaced and the molding sand has a fluid-like state having. The individual grains of sand are there in lively movement and experiencing an intensive mixing, without leaving the molding sand filling.

Through an overflow 34 between the chambers 3 and 4 can Refill the recovery chamber 3 with new items to be treated due to displacement of regenerated molding sand 16 from the hot fluid bed 32 pass into the cooling fluidized bed 33, where it cooled becomes. In the exemplary embodiment, the overflow 34 is so formed that the molding sand from the recovery chamber 3rd Depending on the level, passes into the cooling chamber 4. From reaching a certain level of the hot fluidized bed 32 occurs automatically molding sand from the recovery chamber 3 into the cooling chamber 4 over. The overflow 34 forms a permanent connection between the two chambers 3, 4, however, due to a level difference between the two whirling surfaces of the adjacent fluidized beds only in one direction of flow, namely from chamber 3 to chamber 4 is effective. It shouldn't recooled molding sand from the cooling chamber into the one to be heated Hot fluidized bed can get back.

The overflow 34 is in the illustrated embodiment in Area of the partition 8 is provided. He is one of the two Chambers 3, 4 connecting opening 35 formed, the lower Boundary wall from an upward-facing edge area 36 of the partition 8 is specified. The opening 35 can for example a window-like recess in the partition 8 be, as is the case with the exemplary embodiment. alternative it is also possible to define the opening by that the height of the partition 8 is less than the interior height chooses so that an opening 35 forms Free space between the upper edge of the partition 8 and the above opposite ceiling wall 12 results. It can also several transfer openings are provided at the same height become.

It is particularly useful to have the two chambers 3, 4 as in Combine embodiment into a structural unit and in a common, albeit heterogeneous, composition Train container 2. This container is convenient transportable and can be flexibly attached to different Set up locations.

The recovery device 1 enables the in foundries accruing, partly with foreign particles and substances contaminated old sand and bound molding sand Recycle core and mold fragments to make the molding sand practical to get back in output quality. When pouring for example, castings made of aluminum or gray cast iron are often molds made from bonded molding sand and casting cores used. The molding sand becomes a liquid, hardenable Binder added, the amorphous so produced Mix the sand in an openable and closable mold filled with bubbles, the binder and with it the sand mixture hardened in the mold and after opening it the now solidified and dimensionally stable casting mold or the casting core taken from bound molding sand. The cleaned Mold parts and mold cores become a complete mold composed of a certain shape during the casting process of the casting to be cast. After pouring, it has to Cast part can be taken out of the mold and cored. The the casting mold surrounding the outside can be made relatively simply by opening the divisible mold and by shaking Peel off the casting in chunks. Different types of cores can be used Processes are used, mostly the cores but mechanically shaken out of the castings, - knocked or - chiseled, with the seeds in more or less large fragments. Through the recovery device 1 is a very simple separation between the molding sand and the binder possible, so that ultimately more free and binder-free molding sand is present.

The two are in the initial state of a recovery process Chambers 3, 4 each with a molding sand filling 16, 16 ' pourable, granular molding sand filled, the filling height in the recovery chamber 3 is larger than in the cooling chamber 4. In any case, the fill level is at least twice the diameter of the largest shape or to be treated Core fragments 37. By appropriate container depth in the Recovery chamber 3 and due to a suitable choice in so far involved operating parameters such as air pressure and air volume the fluidizing air whirling up the molding sand must be ensured be that a corresponding fluidation depth in the Hot fluidized bed 32 can be maintained. Starting from the most common particle size of the shape or core break should have a free fluid bed depth of 80 to 120 cm can cover the largest part of the application spectrum.

To recycle used sand and core and shaped fragments 37 - after the hot fluidized bed reaches its operating temperature has - the relevant core and shape break in the hot fluidized bed 32 introduced. This can be done simply by the old sand and the core and shaped fragments 37 when open Cover 13 or by a flexible closure flap in the hot fluidized bed 32 thrown in or otherwise let in where the core and molding sand blocks are due to gravity into the fluidized molding sand filling 16 of the hot fluidized bed 32 sink down. By interaction of the increased temperature, the generated air swirl and strongly moving molding sand is broken down or separation of the core and molding sand blocks into the original Grains of sand instead. The decay proceeds - similarly like a melting process - from the outside to what used to be deeper Layers instead. The contained in the core and form fragments and also binders surrounding the individual grains gasified or pyrolyzed as well as other organic Foreign particles that can accompany the old sand. The one there resulting gases occur together with the fluidizing air Arrows 38 on the top of the hot fluidized bed 32. Apart from resistant particles, only the binder-free ones remain and scattered shaped sand grains back.

Because by filling new treatment goods into the Hot fluidized bed increases its filling mass, the level increases of the hot fluidized bed temporarily over that of the overflow 34 predetermined maximum level so that molding sand from the Recovery chamber 3 according to arrow 42 through opening 35 flows into the cooling chamber 4. Because of an offset the point of addition of old sand and shaped or core fragments 37 in the hot fluid bed on the one hand opposite the removal point or the overflow 34 of cleaned, hot molding sand on the other hand, the hot fluidized bed 32 becomes corresponding the sand throughput through the hot fluidized bed a drift movement the molding sand filling 16 located in the hot fluidized bed 32 of the addition point to the withdrawal point. About this to be discussed again below.

When the regenerated, initially still hot molding sand enters into the cooling chamber with the cool molding sand 16 'of the cooling fluidized bed 33 mixed and by this as well by maintaining fluidization of the cooling fluidized bed 33 Cooling air cooled quickly. The cooling goes above all because it is fluidized there Mold sand grains come into contact with cooling medium on all sides and so be forced convectively cooled. Here it is advantageous that no additional mechanical intervention from the outside are required.

It is not functionally necessary that even in the cooling fluidized bed 33 a certain minimum level is observed as long as it is ensured that there is a cooling effect is achieved at sufficiently low temperatures. Therefore can mold sand cooled from time to time from the cooling chamber be removed. However, a continuous one is more expedient Operation when removing molding sand from the cooling chamber 4. The removal means 43 provided in the exemplary embodiment the cooling chamber 4 contain at least one in a side wall 6 attached removal opening 44, which automatically a Level-dependent removal of molding sand enables. It lies the Transfer opening 35 from the hot fluidized bed opposite, so that the incoming hot molding sand is forced to a certain extent Minimum time to linger in the cooling fluidized bed before moving on The discharge opening can exit again. Otherwise located the removal opening 44 is at a certain height level, so that molding sand can only be removed from the cooling fluidized bed 33 is when the filling level of the cooling fluidized bed 33 reaches this level exceeds. The removal opening 44 forms - similar to the transfer opening 34 in the recovery chamber 3 - one Overflow, but with the removal opening 44 placed lower is than the transfer opening 34. That through the removal opening 44 predetermined maximum level of the cooling fluidized bed 33 is thus lower than that of the hot fluidized bed 32 µm thereby a return of already cooled molding sand exclude from the cooling fluidized bed 33 into the hot fluidized bed 32.

It may well be provided that molding sand from the cooling fluidized bed 33 automatically and continuously to the extent the removal opening 44 emerges from the cooling chamber 4, how there is an increase in volume through the expediently also automatic and continuous Transfer of molding sand from the recovery chamber 3 sets. The removed molding sand then only has to be collected and brought to a desired location. Would be conceivable it, the recovery device according to the invention directly set up in the molding shop or in the core shop of a foundry, so that the emerging molding sand without long transport routes must be used again immediately can be.

As a means of transport 45 different techniques for Use, in the simplest case, for example in the form a transport container, e.g. as a mobile wagon. This Means of transport at least when changing containers Interruption of the removal of molding sand in advance. Furthermore, the Pneumatic molding sand used in closed pipes an air pump 48 are promoted, as in Figure 1 is only indicated schematically. Further - open - Conveying techniques for molding sand are conveyor belts or rotating ones Bucket elevators.

In addition to a direct transfer of the regenerated and cooled Molding sand for molding or core making or an interim storage facility there may also be appropriate regenerated molding sand before it was reused classify, which presupposes that in addition to in the foundry the molding sand regeneration plant also a molding sand classification plant is provided. It can namely in enrich regenerated molding sand particles of unsuitable size, which the molding sand after frequent reuse in its reduce positive usage properties. And disintegrates a certain proportion when using the molding sand the grains of sand, so that a dust-like fine fraction is created, the air permeability of the molds made from it or cores impaired. In addition, the multiple Reuse of the molding sand even in the coarse particles Molding sand brought in, which is true to the figure of the molding sand to disturb. That is why a sieving of coarse particles and a selection of the fine fraction from the regenerated molding sand e.g. important in a screening plant.

In particular if 43 means of transport are assigned to the removal means which are an occasional interruption of removal make it necessary, it may prove appropriate to the Removal opening 44 a e.g. valve or slide type shut-off device 46 assign. This enables a controlled Removal of molding sand e.g. at intervals, which is an advantage is when the means of transport 45 individual transport containers include the one after the other outside of the container 2 the removal opening 44 are placed. The removal opening 44 is expediently designed in this case and merges into a molding sand outlet connection 47. At least partial closure of the removal opening is also essentially at continuous removal of molding sand makes sense, and an uncontrolled outlet of dust-laden exhaust air in the immediate vicinity of the recovery device or excessive intake of outside air through this opening to reduce through the suction device 62. It In such a case, the clear cross section can be useful the discharge opening automatically by a sand accumulation to avoid evasive swing flap at least partially.

If the removal means 43 with a forced shut-off device 46 are equipped, the removal opening 44 also below a minimum level to be observed the cooling fluidized bed are arranged. In this case when opening the shut-off device 46 make sure that the level in the cooling fluidized bed 33 does not fall below a certain level Minimum height that is required to always be sufficient Provide cooling fluidized bed volume. on the other hand In such a case, it must be ensured that the forcibly closable removal opening as it grows Level of the molding sand or fluidized bed in the cooling chamber is opened in time to overfill the Avoid cooling fluidized bed.

The recovery device 1 of the embodiment is further trained so that from the old sand and the core and Mold fragments resistant particles, e.g. Cast breakage, remains of burrs, broken feeders and similar fragments of metal Recycling material of a foundry, can be selected, regardless of how and where these parts in the old sand arrived or what type or how big they are. The recovery device 1 has in a natural way through the hot fluidized bed via a separating agent for selection such resistant particles 53. They sink due to gravity in the hot fluidized bed and collect in the floor area. Of there they can be taken out from time to time.

To completely empty the recovery chamber To avoid 3, a simple selection is more resistant Particles provided. Throughput was higher Drift movement of the mold sand filling 16 through the Hot fluidized bed moved from the addition point to the tapping point has been addressed. This drift movement is used according to the invention to fill the molding sand by a fixed, with regard to certain physical properties selectively effective release agent through or on to move past it, being crushing or gasification resistant Particles 53 on this release agent within the Hot fluidized bed 32 retained and from the further drifting Mold sand filling 16 can be selected and from time to time can be carried out.

In the illustrated embodiment, the separating means is 52 a strainer basket 54 which can be removed from the hot fluidized bed is provided, in which the resistant particles 53 collect. The The strainer basket can be opened from time to time with the lid 13 open the handling device 56 lifted out of the hot fluidized bed become. After emptying the strainer basket, it can again into the fluidizing hot fluid bed like a liquid be lowered. The rectangular screen basket 54 of the illustrated Embodiment has walls with grid-like Structure based on wall openings in the side walls and floor 55 has. By means of an only schematically indicated Handling device 56, for example a suitable lifting device, can the strainer basket 54, in which there are resistant particles 53 have accumulated, with the lid 13 open lift out of the hot fluidized bed 32 so that the resistant Particles no longer impair the action of the hot fluidized bed 32 can and the decomposition process of the introduced Core and form fragments can take place unhindered. The sieve basket 54 emptied of the resistant particles 53 is then lowered again into the hot fluidized bed 32. While the remaining of the screen basket in the hot fluidized bed 32 is the Handling device 56 uncoupled from the strainer and the Cover 13 closed. The grid in close succession on Sieve basket mounted wall openings 55 allow it Molding sand 16 of the hot fluidized bed 32, almost unhindered Inside of the strainer basket and the inserted core and Mold fragments 37 to act completely. In the the drawing exaggerated wall openings 55 can have a mesh size of 5 to 10 mm, so that resistant particles up to this size are retained in it become. Smaller resistant particles that are specifically heavier than the fluidized molding sand, e.g. Metal balls or Metal chips are not caught by the screen basket 54 or withheld, but they still don't get in the cooling fluidized bed because of their larger specific Weight can not pass the overflow 34. This thus acts as a gravity-selective release agent for the selected of small resistant particles that pass through the mesh of the sieve basket fall through and the specifically heavier than the fluidized molding sand. Specifically lighter Foreign particles are organic in nature and therefore can be gasified anyway, so not resistant.

It is easily conceivable that the hot fluidized bed is horizontal has a greater extension than the addition of the piece Treatments are required. Such an enlargement is primarily for increasing the volume of molding sand and thus to increase the time of the treatment item in the hot fluidized bed or to increase the throughput per unit of time sensible due to the hot fluidized bed. It can be in such a way If the strainer basket is limited to the size of the addition point his; he doesn't need the entire hot fluid bed fill. It only has to be ensured that the Really fill in all entered treatment items is caught within the strainer. In addition, must the sieve basket inserted into the hot fluidized bed with its upper one The edge protrudes from the fluidized hot fluidized bed, so that it also specifically lighter, larger foreign particles e.g. made of plastic, wood or textiles Float hot fluid bed, can hold back. such Coarse organic matter should be in the hot atmosphere Either gradually pyrolyze above the hot fluid bed or there until the next emptying process of the sieve basket be held. Are these parts through a disintegration process up to a particle size below the mesh size of the Sieve basket reduced, so they can in the cooling chamber transgressed. In a subsequent classification process however, these residual particles are sorted out.

As far as the resistant particles are made of iron, they can also by a permanent magnet inserted in the sieve basket are held, even if the iron particles are smaller than the mesh size of the screen basket. This can, if they are in a place other than where the permanent magnet is in the sieve basket, through the mesh of the strainer basket fall through and onto the bottom of the hot fluidized bed to lie down. However, you will be there due to the Fluidization movement of the surrounding sand constantly with in Movement kept and get into the Area of influence of the permanent magnet and are held by it. The permanent magnet must be heat resistant, i.e. its Curie point must be above the working temperature of the hot fluid bed lie. If necessary, he must from time to time be magnetized. With each emptying process of the Sieve basket can also with the permanent magnet lifted out from adhering iron parts, which is the hot magnet e.g. by blowing with compressed air outside the strainer can happen. Only small, resistant, non-magnetizable particles e.g. made of aluminum, copper, Brass or glass, which are relatively rare, must be made by Be taken out of the recovery chamber from time to time, which must be emptied completely beforehand. Small light metal parts otherwise oxidize at the operating temperature mentioned of the hot fluidized bed and disappear on oxidative Gradually by itself.

Those from the process of dismantling the core and form fragments the fluidized beds 32 and 33 escaping gases 38 - it is are mainly dust-laden fluidization air as well z.T. to gasification products from the hot fluidized bed not released directly to the environment, but by means of an exhaust gas discharge device 57 checked and cleaned dissipated. A separate exhaust gas discharge can be made from the two chambers respectively; takes place in the illustrated embodiment however, a common removal according to arrows 58. With the common Exhaust gas removal occurs due to a mixture of the hot and cold exhaust air to cool the exhaust air, thereby the suction device 62 is less thermally stressed becomes. The exhaust gas discharge device has a suction device 62 and is also with a filter device 63 equipped with a cleaning of the exhaust gases before delivery to the environment. To prevent the covers 23, 14 of the recovery chamber or the cooling chamber gases and dust-laden fluidization air must escape through a Sufficiently high suction capacity should be ensured that the top in the recovery chamber and in the cooling chamber, respectively an air pressure below the ambient air pressure prevails, so that outside air continuously in the leaks the chambers 3 and 4 are sucked in but no process gases can exit. If necessary, can also above an extractor hood is installed in both chambers 3 and 4, that ensures clean air at the workplace.

The process of dismantling the core and form fragments is proceeding within the hot fluidized bed only on the surface and therefore start slowly. This makes for a certain duration of treatment and Residence time of the old sand and the core and mold fragments in the Hot fluidized bed required, what for small and medium Flows of old sand as well as broken core and broken mold can be accepted. The hot molding sand must also be used are fluidized in the cooling fluidized bed for a relatively long time, until it finally cooled to approximately room temperature is. Taken together, there are large amounts of air through the to move regenerating molding sand through it until it finally cleaned and cooled again. This takes one Overall view of the process, however, in no way as to be viewed disadvantageously because of the per unit of measure Used sand as well as broken core and broken mold, relative large amount of air has a strong dilution effect the resulting gasification products. This strong dilution of the resulting pyrolysis gases may a costly thermal post-combustion of the exhaust air unnecessary. In such a case, the exhaust air only needs to be cleaned to become what by filtering and / or by wet washing the exhaust air can happen.

For an optimal distribution of fluidizing air in the fluidized beds To obtain 32, 33 are parts in the exemplary embodiment of the respective outflow means 17, 18 in a horizontal distribution arranged in the area of the respective chamber 3, 4 near the floor, in a first arrangement with outflow openings 24 provided tubular bodies 22. In addition, a further part of the outflow means 17, 18 in a vertical distribution in the area near the side wall within the respective Chamber 3, 4 arranged, namely with a second arrangement of tubular bodies 22 '. In these tubular bodies 22 'are the outflow openings aligned so that the registered there Fluidizing air flows horizontally into the fluidized bed, causing too a significant improvement in the effectiveness of the fluidized beds contributes. In the hot fluidized bed it is achieved that the Fluidized grains of sand are also a preferred horizontal component of motion get imposed on what the decomposition of the the hot fluidized bed inserted core and form fragments also possible from their side surfaces. The cooling fluidized bed allow the side inflow means an increased Air intake and thus an increased cooling capacity in comparison to a purely bottom entry of the fluidization air.

The fluidizing air whirling up the molding sand is said to have a such pressure in the hot fluidized bed 32 and / or in the cooling fluidized bed 33 are fed in, which is approximately proportional to Height of the fluidized fluidized bed above the respective one The fluidization air is fed into the fluidized bed. In terms of the depth of the fluidized Fluid bed approximated with a corresponding water depth be equated. The outflow openings arranged in the floor area are all at the same depth within of the fluidized bed and can accordingly with the same air pressure be supplied. With a fluidized bed depth The feed pressure of the bottom side is supplied by 80 cm Fluidization air amount to about 80 cm water column. The arranged in a distributive distribution, flowing out laterally Outflow openings, however, are at different depths in the fluidized bed, so that here measures for even distribution of the fluidizing air in the height direction have to. If - as shown in Figure 1 - the tubular body 22 'in Side area are arranged vertically, so must by installation suitable flow resistances for an even distribution the fluidizing air in the height direction. This can e.g. by suitable dimensioning of the outflow openings 24 done that as interchangeable nozzle inserts with different Flow resistance can be formed. resistance arms Nozzle inserts are used below, with increasing height, nozzle inserts with greater flow resistance weighed be used. Another way to Compensation for the different altitude of the outflow openings within the fluidized beds is the same level lying outflow openings - deviating from the Representation in Figure 1 - each on a horizontally laid Arrange the tubular body and several tubular bodies in the side wall area to be laid in rows like each other, each one Tubular body via an individually adjustable valve on the part of a uniform pressure source with the associated optimal fluid pressure can be supplied. Such pressure adjustment valves are also on the bottom tubular bodies expedient in order to achieve an optimal fluidization pressure even with them to be able to adjust.

Also in the longitudinal direction of the tubular body 22, 22 'takes place a change in a flow slowing backwards the flow resistance instead. Is due to the shorter flow paths the flow resistance to the front Outflow openings smaller than to only one longer flow paths or flow resistance can be achieved, rear outlets so that the front outlets preferably supplied with fluidizing air and the rear be ignored. Accordingly, the Tubular body for an equalization of the air outlet over be provided for the length. This can also be done by targeted different dimensioning of the outflow resistance the outflow openings and / or by decreasing cross-section of the tubular body can be reached towards the end.

The heating of the hot air fluidizing the hot fluidized bed 32 takes place in the case of the exemplary embodiment in FIG. 1 outside the recovery chamber 3 by the heater 27. To achieve an even better heating effect, everyone or at least some of those in the recovery chamber 3 first outflow means 17 within the recovery chamber 3 assigned a further heating device be shown in a possible embodiment in Figure 2 is. In any case, the fluidization air is heated only after compressing the air to the required Operating pressure and in any case also before inflow the fluidizing air into the hot fluidized bed. That in the inflow means 17, 22, 22 'integrated heating can be an additional heater his. If the effect is sufficient, the can Air outlet means integrated heating but also as sole Heater can be used so that the external heater 27 could be omitted. It may be not necessarily required, a heating device in all first outflow means 17 64 to integrate. Depending on the size of the fluidized bed and the amount of molding sand to be enforced per unit of time with less heat some of the tubular bodies without one such heating device 64 may be equipped. The corresponding Distribution - heated and unheated inflow means - done as needed. It can also be useful, everyone However, the tubular body of the hot fluidized bed is heatable only connect individual heating elements as required. For example you will be in the initial phase when heating the Fluid bed at operating temperature with higher heating energy drive than after reaching it. Likewise, one will feed a large amount of new - cold - items to be treated heating more than in phases with lower throughput. Through targeted Individual heating elements can be switched on or off control the operating temperature of the hot fluidized bed.

While in the embodiment of Figure 1, the tubular body 22, 22 'of the first outflow means 17 are generally cylindrical Have the outer contour, those with the heating device 64 cooperating tubular bodies 22 "according to FIG. 2 designed so that there is an arcuate cross-sectional shape. The tubular body 22 "has an overall groove-like shape and encloses an arcuate flow channel 65 Cross-section.

The heating device 64 has an outer cylindrical shaped heating element 66, which in the from the tubular body 22 " Defined concave longitudinal recess 67 with parallel alignment is attached heat transfer, so that a peripheral portion 68 of its outer surface enclosed by the tubular body 22 " is. In the embodiment shown in Figure 2 is a arranged in the interior of the heating element 66, preferably electrically heated heating element 72 shown. This gives, for example, an electrically heated heating element 66 Thermal energy on the tubular body in contact with it 22 "from, which is thus heated up and heating the air flowing in the flow channel 65 causes. simultaneously gives the heating element 66 over its not from the tubular body 22 " covered, exposed peripheral portion immediately heat by radiation and convection in the fluidizing molding sand from. The heat exchange with the tubular body 22 "can still be done be improved that the tubular body 22 "and that Executes heating element 66 as an integral unit that only a single wall in the area of the longitudinal recess 67 is present, which is also a wall section of the tubular body 22 "and the heating element 66 forms.

The outflow openings 24 are located in the channel-like designed tubular body 22 "on the radially outer, that is cylindrical convex wall section. Conveniently, is generally avoided in the case of the horizontal outflow means 17, 18, 22 upward outflow openings 24, so there is no molding sand inside during work breaks the tubular body can penetrate.

For the sake of completeness, there are a few alternatives below Design options for a regeneration device mentioned, which are not shown in the drawing:

For one, it is possible to have a single recovery chamber two or more cooling chambers, each with an associated one Assign cooling fluidized bed. These cooling chambers can be functional operated in parallel, especially if e.g. two Cooling chambers on opposite sides of the recovery chamber are arranged. Through a multiple arrangement of cooling chambers can a larger volume of the cooling fluidized beds, that is, a longer residence time of the molding sand in the cooling chambers and thus a lower final temperature of the molding sand despite using one only at ambient temperature or cooling air at a slightly lower temperature can be reached.

In addition, it is also conceivable for the multiple cooling chambers and to operate the associated cooling fluidised beds in series, the cooling fluidized beds, or at least the last one Cooling fluidized bed operated with separately tempered fluidizing air becomes.

Another alternative is a round one Training of the regeneration device with concentric Arrangement of the fluidized beds. The recovery chamber with a hot fluidized bed is arranged centrally, whereas one or more Cooling chambers concentrically around the recovery chamber arranged with an arcuate fluidization device is or are.

Claims (22)

1. Method for regeneration of old sand and recovering the sand from fragments of sand forms and sand cores of foundries, wherein the fragments of said sand forms and sand cores are crushed and the sand binder is gasified by heat supply and delivered from the sand and wherein the thermally cleaned sand is cooled down to room temperature, characterized by the community of the following features:

   uncrushed fragments of said sand forms and sand cores (37) as well as old sand, which may be accompanied by foreign particles (53), are braked down to the sand grains thermally as well as mechanically by influence of the fluidization movement in an unique step in a heated fluidized bed (32), whereby accompanying organic materials, especially binding means, are gasified thermally and carried off in this form from the heated fluidized bed (32) (flowing 38, 58),

   said cooling down of the cleaned sand is done in a cooling fluidized bed (33), which follows to the heated fluidized bed (32) with respect to fluctuation and which is fluidized with cold air, whereby the form sand is going over from the heated fluidized bed (32) to the cooling fluidized bed (33) over an overflow (34).
2. Method according to claim 1, characterized therein that by choice of suitable air pressure and air volume of the fluidization air fluidizing the form sand as well as suitable filling height in the heated fluidized bed (32) there is maintained a depth of fluidization of at least twice the diameter of the biggest fragments (37) of sand forms and sand cores.
3. Method according to claim 1 or 2, characterized therein that due to an offset of the location of supply of old sand and fragments (37) of sand forms and sand cores into the heated fluidized bed (32) on the one hand and the location of withdrawal (overflow 34) of cleaned hot form sand out of the heated fluidized bed (32) on the other hand and according to the throughput of sand through the heated fluidized bed (32) is created a drift motion of the form sand filling (16) in the heated fluidized bed (32) through or passing by a sedentary separating means, which is effective with respect to certain physical selection properties, whereby particles (53) which will resist to breaking down and to gasifying, are retained within the heated fluidized bed (32) at this separating means and are separated from the form sand filling (16) drifting further, from which they can be removed from time to time.
4. Method according to claim 1, 2 or 3, characterized therein that the fragments (37) of sand forms and sand cores are braked down from their underside as well as from lateral sides to sand grains by the fluidized motion of sand and hot air of the heated fluidized bed (32) by supplying the hot air into the heated fluidized bed (32) which creates the fluidizing sand motion not only from underneath but also from the lateral side and there with horizontal component of movement.
5. Method according to one of the claims 1 to 4, characterized therein that the fluidization air fluidizing the form sand (16, 16') is supplied into the heated fluidized bed (32) and/or into the cooling fluidized bed (33) respectively with a pressure, which is approximately proportional to the whirled up height of the heated fluidized bed (32) or of the cooling fluidized bed (33) measured above the supplying point of the fluidization air into the heated or the cooling fluidized bed (32, 33).
6. Method according to one of the claims 1 to 5, characterized therein that the heated fluidized bed (32) is operated at a temperature, which lies beneath the inflaming temperature of the developing gases, preferably at about 480 to 530 °C.
7. Method according to one of the claims 1 to 6, characterized therein that the fluidization air fluidizing the heated fluidized bed (32) is heated up to operation temperature only after compression up to the operation pressure immediately before supplying into the heated fluidized bed (32).
8. Method according to one of the claims 3 to 7, characterized therein that resisting particles (53) are selected from the form sand filling (16) of the heated fluidized bed (32) according to their size, whereby a sieve (54) is used as separating means.
9. Method according to claim 8, characterized therein that a basket (54) out of sieves is used as the sieve, the basket (54) being open at the top and surrounding the supply area of old sand and of fragments (37) of sand forms and sand cores at the underside and laterally and the basket (54) being able to get lift out of or merged into the heated fluidized bed (32).
10. Method according to one of the claims 3 to 9, characterized therein that resisting particles (53) are selected from the form sand filling (16) according to their specific weight, whereby a mechanically effective overflow (34) is used as the separating means.
11. Method according to one of the claims 3 to 10, characterized therein that resisting particles (53) are selected from the form sand filling (16) according to their magnetizability, whereby a permanent magnet is used as the separating means, the permanent magnet being stable against elevated temperatures and its curie-point lying above the operating temperature of the heated fluidized bed.
12. Apparatus for regeneration of old sand and recovering the sand from fragments of sand forms and sand cores of foundries, especially for working out the method according to one of the claims 1 to 11, characterized by

    a recovering chamber (3), being able that a heated fluidized bed (32) out of heated and gas flown form sand (16) can be created in it, to which the old sand and the fragments (37) of sand forms and sand cores can be supplied,

    a cooling chamber (4), being able that a cooling fluidized bed (33) essentially out of cooled and gas flown form sand (16') can be created in it, and

    an overflow (34) enabling a going over of heated form sand (16) from the heated fluidized bed (32) in the recovering chamber (3) into the cooling chamber (4).
13. Apparatus according to claim 12, characterized therein that the recovering chamber and the cooling chamber (3 and 4) are connected to a single mounting unit, especially are arranged in a common housing (2).
14. Apparatus according to claim 12 or 13, characterized therein that withdrawal means are arranged with respect to the cooling chamber (4) for withdrawing cooled form sand from the cooling fluidized bed (33), the withdrawal means being preferably in form of at least one opening (44) of overflow.
15. Apparatus according to claim 14, characterized therein that the opening (44) of overflow at the cooling chamber (4) for withdrawing cooled form sand from the cooling fluidized bed (33) is located geodetically lower than the overflow (34) at the recovering chamber (3) for going over of regenerated form sand (16) from the recovering chamber (3) to the cooling chamber (4).
16. Apparatus according to claim 14, characterized therein that a basket (54) out of sieves is arranged in the recovering chamber (3), the basket (54) being open at the top and surrounding at least the supply area of the heated fluidized bed (32) laterally and at the underside and the upper border of the basket protruding above the upper side of the whirled up heated fluidized bed (32), the basket (54) being able to get lift out or merged into the heated fluidized bed (32).
17. Apparatus according to one of the claims 12 to 16, characterized therein that at least the recovering chamber (3) but preferably the cooling chamber (4) too is equipped with a liftable lid (13 or 14 respectively).
18. Apparatus according to one of the claims 12 to 17, characterized by an exhaust gas device (56), which takes away gases escaping from the recovering chamber (3) and/or from the cooling chamber (4), which preferably is equipped with a filtering device (63).
19. Apparatus according to one of the claims 12 to 18, characterized therein that the recovering chamber (3) is equipped with first emitting means (17) for feeding heated fluidization air, which are integrated with a heating device (64).
20. Apparatus according to one of the claims 12 to 19, characterized therein that not only emitting means (17, 18; 22) near the bottom, spread out in a horizontal plane are arranged at least in the recovering chamber (3) and preferably in the cooling chamber (4) too, but that further emitting means (17, 18; 22') are arranged near the lateral area, spread out in a vertical plane, which cause an essentially horizontal emitting of gas.
21. Apparatus according to one of the claims 12 to 20, characterized therein that the emitting devices (17, 18) are formed by tubular bodies (22, 22', 22"), which are equipped with emitting openings (24).
22. Apparatus according to one of the claims 12 to 21, characterized therein that the heating means (64) is build up in that way, that heat is transferred both to the belonging emitting devices (17, 22") and to the heated fluidized bed (32) surrounding it.

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