EP3202927A1 - Method of and device for regeneration of foundry sand - Google Patents

Abstract

The invention relates to a method for regenerating foundry sand, in particular for the re-production of foundry molds and / or foundry mold cores from the regenerated foundry sand, by removing binder from a foundry sand binder mixture, using a, preferably absorbent, solid support means (6) Binder and carrier (6) are separated from the foundry sand. According to the invention, the carrier means (6) is brought into contact with the foundry sand binder mixture, preferably added thereto, and is separated from the foundry sand together with the binder adhering thereto and / or absorbed therein.

Description

The invention relates to a method for regenerating foundry sand according to the preamble of claim 1, in particular for the re-production of foundry molds and / or foundry mold cores from the regenerated foundry sand, by removing inorganic binder, such as waterglass or organic binder from a foundry sand-binder mixture, using a preferably absorbent, solid (ie not having a liquid state of matter, but formed by a solid) support means, wherein binder and carrier are separated from the foundry sand.

Furthermore, the invention relates to a (regenerating) device for foundry sand designed for carrying out the proposed regeneration method according to the preamble of claim 11, comprising means for contacting solid carriers and foundry sand.

For economic reasons, the foundry industry is anxious to reuse foundry sand, ie to feed the foundry sand already used at least once for cores or molds a sand cycle. It is known that the foundry sand no longer satisfies the sand quality requirements for a casting process with increasing proportions of binder (binding agent proportions), ie it is endeavored to largely separate the binder from the foundry sand as much as possible. In addition, the foundry sand must be free-flowing prior to its recycling, which in the case of cleaning with water, a drying of the sand requires.

Various foundry sand processing methods have become known, which are very energy-intensive, in particular in the event that they require the use of large amounts of water or the regeneration process requires high temperatures.

For example, on the DE-OS-18 06 842 directed. This describes a thermal process for the regeneration of foundry sand, wherein according to the teaching of the document the foundry sand is annealed at 1000 ° C and subsequently removed binder residues, by sudden cooling, rubbing or beating and air classification.

The DE 199 343 060 007 A1 describes a regeneration method for water-glass-bonded foundry sands, which requires a heating of the sand to over 200 ° C. A similar demand is made at the time of DE 20 2008 018 001 U1 collected known procedures. Here the foundry sand is treated in a rotary kiln or in a fluidized bed, whereby a screening and air classification can follow.

The WO 2013/026 579 A1 describes a mechanical-thermal regeneration process with which the treated foundry sand is to achieve new sand-like properties. The sand to be regenerated is first treated in a pneumatic treatment chamber and then fed to a thermal regeneration stage. However, prior to the thermal treatment, a hardening agent for water glass is added to the foundry sand.

The DE-OS-24 08 981 describes a mechanical regeneration process in which foundry sand is accelerated at high speed by means of a centrifugal disc and bounces against a sand pad. Due to the falling after the impact of the sand flow, an air flow is guided, which is to dissipate the fine particles resulting from the impact.

Another mechanical regeneration principle is in the DE 43 16 610 A1 described.

The purely mechanical and / or thermal regeneration methods hitherto do not provide satisfactory separation results based on the binder on an industrial scale.

The DE 100 38 419 A1 describes a wet regeneration process whereby the sand is regenerated by adding water until pulp forms and moving the pulp by external forces, flushing the sand with water, draining the water to neutralize it, and dewatering and drying the sand. Good separation results are suspected here, but the large amounts of water required in foundries are undesirable and dangerous. In addition, considerable energy inputs are needed to dry the sand and evaporate the large quantities of water. Also, the accumulating wash water must be regenerated.

From the DE 10 2005 029 742 B3 Also, a wet regeneration process has become known in which one of two sand streams is wet-regenerated, which means that the binder is washed out with large amounts of water and then the free liquid is separated. From the document, it is also known to reduce the energy input for the drying of the cleaned foundry sand the cleaned foundry sand after its washing with a substance to mix, which absorbs the moisture of the sand grain surface. This material is added in the form of granules larger than the foundry sand grains to screen the pulps from the cleaned foundry sand. Thus, according to the teaching of DE 10 2005 029 742 B3 drying the cleaned foundry sand without heating it.

The cleaned and dried foundry sand is mixed with untreated foundry sand, whereby the binder content increases again. The separated from the cleaned foundry sand cloth grains can then be dried. The known method is, as mentioned, the mixture of the purified and dried foundry sand flow ahead with an untreated foundry sand flow, whereby overall the energy input low, but the sand properties for foundry operation due to the still relatively high binder content in need of improvement. In addition, large amounts of water are needed for the drying process preceding the washing process, with the disadvantages already described above.

Based on the aforementioned prior art, the object of the invention is therefore to specify an alternative, improved regeneration method for foundry sand mixed with binder from a foundry process which has already taken place, which, in addition to low energy consumption, results in good foundry sand grades of the regenerated foundry sand, i. ensures a high separation rate with respect to the binder and beyond the foundry sand regenerate is free-flowing. Preferably, the regenerated material produced (cleaned and dry foundry sand) should at least largely have resurfacing properties and / or be reusable. More preferably, no environmentally and / or harmful substances should be used.

Furthermore, the object is to provide a regeneration device for carrying out the advantageous regeneration method.

This object is achieved in terms of the regeneration process with the features of claim 1, ie in a generic method characterized in that the carrier (not only with the already finished sand foundry sand, but) with the foundry sand binder mixture brought into contact, preferably added thereto, and is separated from the foundry sand together with the adhering to this and / or absorbed therein binder.

With regard to the device, the object is achieved with the features of claim 11, i. in a generic device characterized in that this release agent for the common separation of the carrier and adhering thereto and / or absorbed therein binder of the foundry sand.

Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

In order to avoid repetition, features disclosed according to the method are also to be regarded as disclosed in accordance with the device and to be able to be claimed. Likewise, devices disclosed according to the device should also be regarded as disclosed according to the method and be able to be claimed.

The invention is based on the idea that, preferably in an upstream mechanical treatment step of the foundry sand-binder mixture of the foundry sand grains detached binder and / or in a solid, ie no liquid state having state support carrier and then this solid carrier together or together with the at this adhering and / or absorbed in this binder including any binding properties of the binder influencing additives (additives) to separate from the foundry sand. At the same time, fumed silica is preferably separated from the foundry sand together with the carrier, whereby the fumed silica also adheres to and / or is absorbed in the carrier becomes. For the preferred case, to be explained later, that small amounts of an at least temporarily liquid adhesion promoter, in particular water, are added to the foundry sand binder mixture, the, preferably absorbent, carrier agent simultaneously performs a drying function in addition to its binder carrier function. However, this is not mandatory, especially if any existing moisture is removed in another way, for example by microwave treatment, or if drying due to a low moisture content is not necessary.

It is essential here, however, that the solid carrier, not or better not only takes over a drying function but primarily binds the binder, so that binder and carrier together, preferably with simultaneous drying of the foundry sand are separated from the foundry sand, for which it is necessary that the binder contrary to the doctrine of DE 10 2005 029 742 B3 is still at the time of contacting, in particular the addition of the carrier is located on the foundry sand, in particular not in a previous step by a wet treatment of the foundry sand binder mixture for the purpose of leaching the binder while simultaneously separating free liquid was separated from this.

Thus, for the first time, the invention makes use of the adhesion properties of the binder to form a solid support agent different from the foundry sand to be cleaned, by bringing the carrier, in particular by cohesion and / or by contacting, in particular adding the carrier with or to the foundry sand binder mixture Adhesion and / or Kapillarbindung and / or other adhesive or Saugaufnahmeeffekten the majority of located in the foundry sand grains binders and other fine-grained materials, such as Fumed silica and / or electrically charged particles binds, so that carrier with it and / or binder present in it separated from the foundry sand, in particular can be removed from a gas stream, can.

As a result, the invention overcomes a significant disadvantage of known methods, since with the technologies used there, binders, mechanically abraded Feinstteilchen and electrically charged particles could not be separated sufficiently from the foundry sand, which meant that they shortened in the reclaimed the period in which The Regenerat, which was usually mixed with new sand, new forms and cores could be produced. The interfering fines remained largely with the foundry sand, in particular they adhere to this, and acted through the enlarged surface active in the wet determination of electrical conductivity and acid consumption, which serve as indicators of foundry properties.

In principle, it is preferred if the binder present in the foundry sand binder mixture and to be separated from the foundry sand together with the carrier agent is an inorganic binder, in particular water glass. Additionally or alternatively, organic binders can be selected. In any case, the carrier agent and the binder are to be coordinated or selected such that a large part of the binder adheres to and / or is received in the carrier in order to be able to be separated from the foundry sand together with the carrier, ie in a common separation step. Belonging to the binder in the context of the present disclosure, the binding properties of the actual binder active substance, such as water glass influencing additives understood. Such, especially in inorganic binders or binder active substances used for use additives are also offered on the market under the name promoters. These additives preferably influence the network formation of the actual binding active substance and / or the hot strength of the forms and cores to be produced from the foundry sand binder mixture. Preferably, the aforementioned additives physically and / or chemically covalently interact with the binder active substance and / or serve as a catalyst. In principle, such additives may be added in powder form to the foundry sand and / or liquid, in particular together with a liquid binder active substance.

As already mentioned, it is essential that the carrier in order to be able to bind binders to any additives, other fines, in particular fumed silica and electrically charged particles, is added or brought into contact with the foundry sand binder mixture and not with the already cleaned foundry sand. To ensure this, it is advantageous if the contacting, in particular the addition of carrier to the foundry sand binder mixture without prior wet treatment, i. Wash out binder with liquid, such as water.

In general, it should be noted that - unless otherwise stated in an individual case - the weight percentages used in the text are based on the original foundry sand-binder mixture to be treated in the context of the invention, even before an optional mechanical-to-be-explained Treatment. This means that substances added in the context of the process, in particular the carrier and / or an adhesion promoter, are not considered.

It is particularly preferred if the carrier is reused after the separation of foundry sand, ie added to a (new) Altgießereisandcharge for performing the method according to the invention becomes. According to a first alternative, this reuse is essentially untreated, which is possible in particular when the absorption capacity for binders, any additives and fumed silica has not yet been exhausted. In an alternative variant, the carrier can be cleaned before re-use, for example, by mechanical treatment of adhering substances, so that the carrier has again an increased absorption capacity for the substances to be absorbed.

It is particularly expedient if the foundry sand-binder mixture at the time of bringing into contact with the carrier, especially before the addition, a binder weight fraction (weight fraction of binder active substance such as water glass including any previously explained additives) of at least 0.3 wt .-%, preferably at least 0.5 wt.%, More preferably at least 0.8 wt.%, Even more preferably at least 1.0 wt.%, Even more preferably at least 1.5 wt.%, Most preferably about 2 , 0 wt .-% or more.

As already mentioned, the electrical conductivity and the acid consumption are used as an indicator for the foundry sand quality. In principle, a high acid consumption and a high conductivity make it possible to deduce a high proportion of binder. The aim of the process according to the invention is therefore to reduce the conductivity and / or the acid consumption by the process according to the invention or the use of a device according to the invention.

Irrespective of the measuring method used in each case for determining the conductivity and the acid consumption, if the conductivity value and / or the acid consumption in the final process product, ie the regenerated foundry sand, is very particularly preferred at least 30% is reduced compared to a corresponding conductivity value or acid consumption value of the foundry sand-binder mixture before a start of the process. It is particularly preferred if the conductivity and / or the acid consumption by the process is reduced by at least 50%, more preferably by at least 60%, even more preferably by about one third or less of the corresponding original value before the beginning of the process. This reduction is based primarily on the contacting of the foundry sand binder mixture with the carrier and optionally an adhesion promoter and the removal of the binder or by the binder particles by means of the carrier.

The table below shows typical conductivity values and acid consumption values for three different foundry-sand binder mixtures (starting materials of the process) prior to the start of the process, i. in a typical state after a foundry process (left column) and after an optional mechanical processing in the context of the process, where as the mechanical processing here the later to be explained cluster RegVerfahren was applied (middle column), in connection with experiments on the sand 1 and 2 no mechanical processing took place and thus corresponding conductivity and acid consumption values are not indicated. In the right column are the values of the regenerated foundry sand after completion of the process, i. according to a still to be explained splits, i. the separation of the carrier with binder.

All foundry sand binder mixtures (Sand 1, Sand 2, Sand 3) contain a waterglass-based binder with additives. Table on conductivity and acid consumption (examples) 0-sample (used sand ie foundry sand binder mixture before regeneration) After optional mechanical processing, in particular Clusterreg method regenerated sand Conductivity in μS / cm (Sand 1) 1453 - (Sand 1) 461 (Sand 2) 1100 - (Sand 2) 344 (Sand 3) 1138 1109 (Sand 3) 450 Acid consumption in mg HCl / 100g sand (Sand 1) 153 - (Sand 1) 59 (Sand 2) 134 - (Sand 2) 61 (Sand 3) 130 126 (Sand 3) 80

As can be seen from the table and should be considered as a general teaching, it is preferred if the conductivity of a corresponding sand sample at the time of contacting with the carrier is greater than 800 μS / cm, more preferably greater than 900 μS / cm, even further preferably greater than 1000 μS / cm, even more preferably greater than 1100 μS / cm. Likewise, it is preferred that after completion of the process and the separation of the carrier from the then regenerated sand, the conductivity is less than 600 μS / cm, most preferably less than 500 μS / cm.

For the acid consumption is generally that this is preferably greater than 90 mg HCl / 100g sample, most preferably greater than 100 mg HCl / 100g sample, even more preferably greater than 110 mg HCl / 100g sample and before the execution of the method or the acid consumption of the regenerated sand is less than 90 mg HCl / 100g sample, most preferably less than 80 mg HCl / 100 g sample, even more preferably less than 70 mg HCl / 100 g sample.

The above-mentioned and other conductivity and acid consumption values given in the context of this disclosure are determined as follows:

Conductivity:

Add 50 g of sand to 100 ml of distilled or deionized water in a sealable container. Shaking the jar on the laboratory shaker (reciprocal, about 200 rpm) for 15 minutes. Then let the vessel rest for 15 minutes. Determination of the conductivity with the usual conductivity meter in μS / cm with indication of the temperature in ° C.

Acid consumption:

into a plastic bottle (250 ml) is added 100 ml of 0.05 N hydrochloric acid. Then 50g of sand sample are added to the bottle and sealed. This bottle is placed in an ultrasonic bath for 10 min. Following sonication, the sample is shaken for 15 minutes on a platform shaker (reciprocal, 200 rpm). Then it is filtered off via a filter (white tape). 50 ml of the filtrate are titrated with a 0.1 N sodium hydroxide solution in an automatic titrator to pH 3.8.

As already indicated, it is preferred that the foundry sand binder mixture, in particular - but not necessarily - liquid, adhesion promoter to improve the transport of the binder to the carrier and / or to improve the adhesion of binder and / or Feinstteilchen and electrically charged particles on and / or the inclusion of binder, fines and electrically charged particles in the carrier. It is particularly preferred if the adhesion promoter used is a liquid, in particular water, or the adhesion promoter comprises at least one such liquid. It is also conceivable in principle to add an adhesion promoter in the solid state of aggregation, it being expedient for this case if the adhesion promoter is fluid at least during a process step in which the adhesion promoter is in contact with the foundry sand / binder mixture together with the solid support. So reaches a liquid state of matter, which can be achieved, for example by addition of heat, depending on the choice of adhesion promoter, especially in the case of the addition of meltable adhesion promoter.

As a liquid adhesion promoter is particularly suitable water. Additionally or alternatively, for example, alcohols, polar solvents, electrically conductive liquids and / or binders, in particular water glass dissolving and / or dissolving liquids can be used. However, as will be explained later, it is essential that the foundry sand binder mixture does not become wet by the primer addition, i. does not exceed a certain, also to be explained later maximum moisture content and in particular no free liquid results, which would have to be separated. Regardless of the amount and choice of coupling agent, it is preferred to ensure a uniform distribution or mixing.

In principle, it is also conceivable not to use liquid adhesion promoters or to dispense with adhesion promoters which are separate from the support, in particular when the support itself assumes this function, in particular due to a corresponding interaction with the binder, for example because of a surface which is tacky or adhesively adhesive to the bonding agent or chemical or physical affinity for the binder.

The liquid, liquefiable (for example fusible) adhesion promoters resulting from the (small) adhesion promoter addition, only moist, non-wet treatment of the foundry sand binder mixture then also has the consequence considerable advantages in terms of a low energy input for drying.

In order to minimize the treatment energy, in particular the drying energy is, as already stated in development of the invention advantageously provided before and / or during the joint separation of binder and carrier of the foundry sand adhesion promoter, in particular a liquid, preferably water at most to a weight percentage based on the weight of the foundry sand binder mixture without consideration of the carrier weight of less than 4 wt .-%, preferably less than 3.5 wt .-%, more preferably less than 3 wt .-%. It is particularly preferred if this proportion by weight (moisture content) is less than 2.1% by weight, very particularly preferably between 0.1% by weight and 2.0% by weight, even more preferably between 0.3% by weight .-% and 2.0 wt .-%. Also, with 1.5% moisture content (wt.%), Reasonable separation results were observed with low use of dry energy.

Overall, it is advantageous if the moisture content is adjusted and / or selected throughout the process so that the foundry and binder mixture and the regenerative foundry sand (as well as all intermediates) is or remains free-flowing at each process time and not clumping.

It is altogether advantageous if a moisture content of the foundry sand binder mixture, which is always attributable to the addition of which liquid, does not take into account the carrier weight fraction, in particular during the entire regeneration process does not exceed a weight percentage specified in claim 5 or has weight percent ranges specified there and / or is set specifically to such a value.

It has proven particularly expedient if, preferably before the addition of adhesion promoter and / or carrier agent, the foundry sand binder mixture is mechanically processed in order to detach binder aggregated on the foundry sand and / or to comminute binder. Here are basically different mechanical treatments can be used, which ensure that the mixture is exposed to corresponding mechanical loads, in particular shear forces and / or impact forces. It is very particularly preferred when using the German patent DE 10 2013 001 801 B4 protected "clustreg" technology is used, wherein the foundry sand-binder mixture is treated in the void spaces of a heap of bluff bodies in a treatment vessel, wherein the debris is set in motion. It is particularly expedient if the bluff bodies are of spherical, or ball-like or irregular polyhedral shape, and preferably at least ten times larger than the maximum grain of the foundry sand-binder mixture to be treated. It has proved particularly expedient if at least the outer layer of the bluff body consists of quartz-containing material or at least the outer layer of the bluff body of polyurethane or the like. consists elastic material and / or the bluff bodies are hollow, so that the moving bluff body direct the flow of sand and stimulate the touching sand grains and these excited sand grains acting on other grains of sand cleaning.

If necessary, binder removed from foundry sand, particularly after mechanical processing as mentioned above, most preferably prior to addition of primer, i. be separated dry, for example by sieving and / or air classification.

In principle, it is possible for the carrier to be bound to a preferably moved carrier, for example one, in particular rotating, drum and / or a preferably moving, in particular circulating, belt and moving the foundry sand-binder mixture relative to the carrier-bound carrier becomes. Additionally or alternatively, it is possible and preferred to add the carrier in the form of a bulk material to the foundry sand binder mixture, wherein the carrier agent for this purpose is preferably granular and / or powdery and / or fibrous. In this preferred case, it is important to ensure thorough mixing of the vehicle and, preferably by addition of primer, moistened (not necessarily) foundry sand binder mixture.

In particular, substances with a large active surface area, ie with a large outer surface area and / or a large inner surface area, the latter should be accessible from the outside to interact with the binder. In principle, it is possible to use known drying agents, such as aluminum oxide, potassium carbonate, potassium hydroxide, silica gel, molecular sieve, celluloids, etc., the selection of which should be adapted to the particular binder in terms of material, grain and / or pore size.

Simple, cost-effective and environmentally friendly, it is natural substances, in particular renewable substances, preferably in the form of fibers, in particular cellulose and / or wood use.

Particularly good results were obtained with softwood wood fibers in a core spectrum of 0.05 mm to 0.2 mm. In principle, it is also possible to use coarser or finer wood fibers, which do not necessarily include or must consist of softwood. These were found in tests particularly absorbent and receptive to be removed from the grain mixture Feinstteilchen. In addition, such wood fibers with the adhering Feinstteilchen with a later to be explained gas flow well from the grains of sand split (separate). This is favored on it in relation to foundry sand of low weight and the comparison of the shape with the smooth, roundish grains of sand. It can be seen microscopically that binders and ultrafine particles generally and in particular the above-mentioned wood fibers are adhered and also stored with carriers, i. get inside the vehicle.

In the case of the addition of carriers, especially in the form of particles, such as fibers, more preferably wood fibers to foundry sand binder mixture, it has been found to be advantageous if the weight percentage of the carrier to the foundry sand binder mixture prior to the addition of a value range between 1 Wt .-% and 15 wt .-% is selected, even more preferably between 1 wt% and 10 wt .-%. Particularly good results were achieved with a weight proportion of carriers, such as wood flour of more than 2 wt .-%, most preferably more than 3 wt .-%.

It is particularly expedient if the carrier used is combustible, in particular in that it consists of or comprises organic material. This opens up a further development of the invention, according to which the carrier material separated from the foundry sand is burned and the heat energy and / or directly the combustion gases are used, in particular to dry the foundry sand and / or to heat and / or form a later to be explained gas stream, preferably with the separation of carrier and foundry sand takes place.

It has proven to be particularly advantageous if at least partial treatment, in particular drying, of the foundry sand and / or the carrier takes place when these are still mixed. This can be realized, for example, by subjecting the mixture to a heated gas jet, in particular an air jet, which will be explained later, which simultaneously takes place for the separation of carrier agent with binder and foundry sand arranged thereon.

In principle, it is possible to spatially and / or temporally separate the drying step of the foundry sand and the carrier agent from the separating step for the joint separation of the carrier and the binder from the foundry sand. However, a common implementation of drying and separation is particularly expedient, which is achieved in that the mixture of foundry sand and carrier with, in particular heated gas, in particular air are flowed through, in particular within a fluidized bed, in which the heated gas stream is introduced. This common drying and splitting (separation) has considerable advantages and can alternatively be carried out alternatively (batchwise) or continuously. The carrier is discharged by means of the gas stream and can be deposited again by means of at least one filter or cyclone or in other procedural manners (outside of a separating unit or container), in particular in order to be burnt, as already indicated. Preferably, the flow rate of the heated gas stream, in particular air flow during the chipping process is adjusted so that in the regrind no grains with a diameter of less than 0.2mm, preferably less than 0.1 mm are available.

Due to the low moisture content according to the invention or the low addition of moisture, in particular in the form of adhesion promoter, the use of air streams with a comparatively low temperature, in particular at a temperature of below 300 ° C., suffices for the desired drying and separating step. Particularly suitably, the temperature of the air flow is less than 250 ° C and is most preferably selected from a temperature range between 160 ° C and 240 ° C or is set to such a temperature. Additionally or alternatively, in the drying step, the foundry sand, in particular by gas flow, in particular Luftstrombeaufschlagung during the separation (splitting) of the carrier together with the binder at a maximum temperature below 220 ° C, especially below 200 ° C, even more preferably below 180 ° C heated. In principle, it has been recognized that the drying time to reach a desired final moisture content decreases with increasing temperature.

The drying step mentioned in the context of the disclosure comes into play, in particular, during wetting of the foundry sand-binder mixture with liquid and / or liquefiable adhesion promoter. If this is dispensed with, drying can be dispensed with if necessary.

As already explained, the drying by means of an air flow, in particular an air flow for simultaneous removal of the carrier (with binder) from the foundry sand is a possibility for setting a desired final moisture content. In addition or as an alternative to an air stream mentioned, other drying methods can in principle also be used, such as, for example, a treatment or drying with the aid of microwaves. On a drying can in particular be completely dispensed with, if the moisture content is kept low from the outset, in particular by no liquid coupling agent is added, but either no adhesion promoter or a residual adhesion promoter.

The device according to the invention is intended and configured for carrying out the method according to the invention and characterized by the provision of separating means (separating device) for jointly separating the carrier and the binder adhering thereto and / or absorbed therein from the foundry sand. The release agents are preferably simultaneously drying agents for the foundry sand and / or the carrier, which preferably binds a part, in particular the majority, of the moisture added, in particular in the form of adhesion promoter, and / or absorbs it. The release agents preferably comprise a fluidized bed in that the pourable sand / binder mixture can be flowed through by a gas stream, in particular an air stream, with the binder adhering to the carrier, wherein the gas stream, in particular air stream, as disclosed in the process, can preferably be heated.

It is particularly useful if, as already mentioned, the carrier is burned in the context of the method and / or the device, wherein the heat of combustion preferably for heating the gas stream, in particular the air stream for drying the foundry sand and / or separating the carrier with the binder adhering thereto and / or incorporated therein is used, for which purpose, for example, the combustion exhaust gases are conducted via a heat exchanger and / or or a heat exchanger is arranged in the combustion chamber and / or around the combustion chamber. Additionally or alternatively, it is conceivable, the gas volume flow for drying the foundry sand and / or the separation of the carrier with the binder of to form the foundry sand at least partially by means of the combustion gases themselves.

It is now particularly preferred if the device has a heat recovery device or thermal energy is recovered from the regenerated and preferably as described above in the gas flow stream heated foundry sand, further training this heat energy for preheating the gas flow to dry the foundry sand and / or for separating the carrier with the binder from the foundry sand is used. For this purpose, so-called Sandtemperiereinrichtungen can be used, for example, comprise a flowing in a pipe system heat transfer medium and the sand can give heat energy to this pipe system, such as falling or trickling through such a pipe system having falling or trickle space and / or by fluidization of the sand from below and thereby bringing into contact with such a pipe system. Alternative heat exchanger arrangements can also be used to utilize the heat energy of the regenerated foundry sand.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment with reference to the single Fig. 1 showing a preferred embodiment of a process design or apparatus according to the invention.

Fig. 1 shows a possible embodiment of a regeneration process according to the invention. At 1, an unwashed foundry sand binder mixture is supplied which is to be treated. In the present embodiment is inorganic binder in the form of water glass with promoters. The feed takes place in a mechanical treatment device 2 in order to detach and / or comminute binders from the foundry sand grains by the acting mechanical forces. The mechanical treatment is preferably dry, in the concrete embodiment by the in the DE 10 2013 001 801 B4 described "Clustreg" technology or - treatment in which the foundry sand-binder mixture mechanically processed by means of a heap and a relative movement, in particular sheared.

At 3, the result of the mechanical treatment, i. If necessary, the bed, in particular before the mixer 4, a sieving or air classification step for preferably dry cleaning the foundry sand-binder mixture of be subjected to a binder content and / or Feinstteilchen. In any case, in the concrete embodiment in the concrete embodiment, the addition of adhesion promoter 5, here for example in the form of water and carrier 6, here exemplified in the form of wood fibers. The amount of water is chosen in the specific embodiment so that the moisture content of the foundry sand binder mixture after thorough mixing here is for example 1.7 wt .-%, without consideration of the carrier weight fraction. Within the mixer, thorough mixing results in intensive contact of binder particles of the binder and carrier, whereby the binder particles adhere to and / or become lodged on the carrier.

At 7, the further transport of the mixture of foundry sand and carrier with binder particles of the binder thereon then takes place to a splitter 8 (common drying and separating device), by simultaneously drying the foundry sand and at least partially carried the carrier and the carrier together with the binder thereon binder of the binder discharged at 9, that is separated from the foundry sand, which is discharged at 10 dry from the splitter. The splitter 8 comprises a fluidized bed (fluidized bed), in which foundry sand and carrier agent with binder particles of the binder present thereon are flowed through by means of a gas stream 11 heated to 180 ° C. by way of example. It can be seen that the discharged carrier agent is supplied to a separator 12, by means of which carrier medium with binder adhering thereto is separated from the discharge gas stream and fed at 13 to a combustion device 14. The exhaust gas is passed through a heat exchanger 15, which heats a gas stream, here a fresh air stream 16, which then forms the gas stream 11 in the heated state. Preferably, additionally or alternatively, the preheated air stream 17, which has been freed from the carrier in the separator 12, is used to heat the fresh air stream 16. In addition or as an alternative to the aforementioned energy or heat sources, the external heating energy, for example electrically, gaseous, with liquid or solid energy carriers for heating the fresh air flow 16 can be used at 18.

In addition or as an alternative to heating the fresh air flow, thermal energy can be used (not shown) which is recovered from the regenerated sand, for example by a so-called sand tempering or cooling device.

LIST OF REFERENCE NUMBERS

1

Feed of foundry sand binder mixture

2

mechanical treatment device

3

Next transport

4

mixer

5

bonding agent

6

carrier

7

forwarding

8th

Sliver for drying and separation

9

Discharge (discharge gas stream comprising carrier with binder thereon)

10

Discharge of cleaned (and optionally dried) foundry sand

11

gas flow

12

separators

13

Supply of carrier to the incinerator

14

incinerator

15

heat exchangers

16

Fresh air flow

17

airstream

18

external heat energy

Claims (14)

A method for regenerating foundry sand, in particular for the re-production of foundry molds and / or foundry mold cores from the regenerated foundry sand, by removing binder from a foundry sand binder mixture using a preferably absorbent solid support (6), said binder and vehicle ( 6) are separated from the foundry sand,
characterized,
in that the carrier means (6) is brought into contact with, preferably added to, the foundry sand / binder mixture and is separated from the foundry sand (10) together with the binder which adheres to and / or is held therein. Method according to claim 1,
characterized,
that the contacting of support means (6) and foundry sand binder mixture without previous washing of binder is made from the foundry sand binder mixture with liquid. Method according to one of the preceding claims,
characterized,
that the foundry sand binder mixture coupling agent (5) to improve the transport of the binder is added to the carrier means (6) and / or for improving the adhesion of the binder on and / or recording of the binder in the carrier means (6). Method according to claim 3,
characterized,
that the adhesion promoter (5) comprises a liquid, in particular water, or, or at least temporarily in the simultaneous presence of the carrier means (6) in liquid form, particularly by melting, is present. Method according to one of claims 3 or 4,
characterized,
in that before and / or during the joint separation of binder and carrier (6) from the foundry sand, adhesion promoter (5) amounts to at most a weight percentage based on the weight of the foundry sand-binder mixture of less than 4 wt .-%, preferably less than 3.5 Wt .-%, even more preferably less than 3 wt .-%, even more preferably less than 2.1 wt%, most preferably between 0.1 wt .-% and 2.0 wt%, more preferably between 0 3% by weight and 2.0% by weight, even more preferably between 0.4% by weight and 1.7% by weight, and / or that a moisture content of the foundry sand-binder mixture, without taking into account the carrier weight fraction, especially during the entire regeneration process, a wt% of less than 4 wt%, preferably less than 3.5 wt%, even more preferably less than 3 wt%, even more preferably less than 2 , 1% by weight, very particularly preferably between 0.1% by weight and 2.0% by weight, especially b preferably between 0.3% by weight and 2.0% by weight, even more preferably between 0.4% by weight and 1.7% by weight and / or adjusted to such a weight% value becomes. Method according to one of the preceding claims,
characterized,
in that the foundry sand / binder mixture is mechanically processed for detaching binder from the foundry sand and / or for comminuting binder, preferably before the addition of adhesion promoter (5) and / or carrier, in particular by moving relative to a heap of bluff bodies. Method according to one of the preceding claims,
characterized,
in that the binder removed from the foundry sand, in particular after a mechanical treatment and / or prior to a coupling agent addition, in particular by screening and / or air classification, is separated off. Method according to one of the preceding claims,
characterized,
that the carrier (6) is brought into contact with the foundry sand binder mixture as, in particular granular and / or pulverulent and / or fibrous, bulk material and / or that the carrier (6) is attached to a carrier, in particular a drum and or is bound to a belt and the foundry sand-binder mixture is moved relative to the bonded carrier (6), in particular by moving the carrier. Method according to one of the preceding claims,
characterized,
in that the carrier (6), together with the binder, in particular binder particles, is heated by a preferably heated, Gas stream, in particular air stream, preferably in a fluidized bed, is separated from the foundry sand, continuously or batch wise, preferably with simultaneous at least partial drying of the still mixed with the foundry sand binder mixture carrier. Method according to claim 9,
characterized,
that the gas stream is heated to a temperature below 300 ° C, in particular below 250 ° C, particularly preferably to a temperature between 160 ° C and 240 ° C and / or the foundry sand during the separation of the carrier together with the binder to a maximum temperature from below 220 ° C, preferably below 200 ° C, even more preferably below 180 ° C is heated. Apparatus for regenerating foundry rice, in particular for the re-production of foundry molds and / or foundry mold cores, the apparatus being adapted for carrying out a method according to one of the preceding claims, comprising means for contacting solid support means (6) and a foundry sand,
in
by release means for joint separation of the carrier means (6) and of the adhesive thereon and / or incorporated therein binder part, in particular of binder ponds, of the foundry sand. Device according to claim 11,
characterized,
in that the, preferably a fluidized bed apparatus for producing a foundry sand-carrier-binder fluidized bed, comprising separating means, gas stream generating means for generating a, in particular heated, gas stream for the common separation of carrier means (6) and binder from the foundry sand. Device according to one of claims 11 or 12,
characterized,
in that the device has a combustion device (14) for burning the separated carrier means and means for heating the gas flow with heat energy resulting from the combustion and / or for forming the gas volume flow using combustion gases. Device according to one of claims 11 to 13,
characterized,
in that the device comprises a heat recovery device for recovering heat energy from the regenerated foundry sand, preferably for heating the gas stream for separating carrier and / or drying foundry sand.

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