MÉTODO E APARELHO PARA REGENERAR AREIA VERDE

Abstract

A method and an apparatus for regenerating green sand, wherein when regenerating green sand, focusing a first mechanical process to the green sand, focusing a thermo-me¬ chanical process to at least part of a green sand fraction that has undergone the first mechanical process, and focusing a second mechanical process to at least part of the green sand fraction that has undergone both the first mechanical process and the thermo-mechanical process.

Description

1 / 20 “METHOD AND APPARATUS FOR REGENERATING GREEN SAND” BACKGROUND OF THE INVENTION

[001] The invention relates to the regeneration of green sand, that is, sand comprising a clay-based binder.

[002] Green sand, that is, sand composed of a clay-based binder, is used in metal foundries for mold making, i.e., for the manufacture of molds and cores needed during metal casting. This foundry sand used in foundries is typically processed green sand, where a fraction suitable for its grain size for the intended use in question has been selected from green sand, to which is further added, for example, a clay-based binder. The clay-based binder comprises clay, usually bentonite, and one or more additives added to the clay, usually at least carbon. By means of this clay-based binder, the sand is moldable to form a desired mold or core.

[003] One of the biggest challenges and problems for foundries is the final disposal of used molding sand remaining from the molds. So much used foundry sand from the manufacture of castings is, on average, generated as finished castings. Previously, used foundry sand was typically transported to a landfill, but nowadays, as natural sand reserves are dwindling and environmental regulations are becoming more stringent, the recycling of used foundry sand for reuse as foundry sand or for some other use is increasing.

[004] However, recycling used foundry sand for reuse, either as foundry sand or for some other use, normally requires regenerating the used foundry sand so that the properties of the regenerated foundry sand are acceptable for reuse as foundry sand or for some other use.

[005] For example, mechanical or thermal processes have been used for the regeneration of used foundry sand, processes that aim to remove Petition 870250079879, dated 05 / 09 / 2025, pp. 64 / 94 2 / 20 Impurities in the sand used or in the binder containing clay and additives prevent the sand from functioning in its previous use. In order to use natural resources more effectively, there is an even greater need for more efficient regeneration of used foundry sand, in which a larger portion of the sand already used can be recycled and the use of natural sand reduced. BRIEF DESCRIPTION OF THE INVENTION

[006] The object of the invention is to provide a new type of method and apparatus for regenerating green sand.

[007] The arrangement according to the invention is characterized by what is disclosed in the independent claims.

[008] The invention is based on the regeneration of green sand by applying different processes in a specific order, where each process focuses on the sand at a stage where a previous process was applied to the sand, which assists in the regeneration of the sand during the next process. In the solution according to the invention, apply a first mechanical process to the green sand, apply a thermomechanical process to at least part of a fraction of green sand that has undergone the first mechanical process, and apply a second mechanical process to at least part of the fraction of green sand that has undergone both the first mechanical process and the thermomechanical process.

[009] The first mechanical process, the thermomechanical process, and the second mechanical process that follow each other efficiently regenerate the foundry sand comprising a clay-based binder. Furthermore, after the first mechanical process, the possible recovery of the used binder, i.e., used clay and an additive, particularly carbon, separated from it, increases the total amount of various recovered and reusable materials.

[010] Some embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[011] The invention will now be described in more detail in connection with Petition 870250079879, dated 05 / 09 / 2025, pages 65 / 94 3 / 20 some modalities and with reference to the attached drawings, in which: Figure 1 schematically shows a method for regenerating green sand, and Figure 2 shows schematically a device for regenerating green sand.

[012] For clarity, some embodiments of the invention are illustrated in the figures in a simplified manner. Similar parts are indicated in the figures by the same reference numbers. DETAILED DESCRIPTION OF THE INVENTION

[013] Figure 1 schematically shows a principal method according to the solution for regenerating green sand, i.e., sand composed of a clay-based binder, wherein the clay-based binder comprises clay, typically bentonite, and one or more additives, such as carbon, added to the clay. Thus, regenerable green sand consists of sand grains with a layer of clay-based binder on their surface. Regenerable green sand may include, for example, sand comprising a clay-based binder originating from a metal foundry, used for casting. Regenerable green sand may also include unused sand comprising a clay-based binder remaining from the manufacture of a foundry mold or core. Typically, the clay-based binder comprises bentonite, but the use of other clay-based binders is also possible in green sand.

[014] With reference to Figure 1, a method in accordance with the solution comprises at least the following steps: 1) Apply an initial mechanical process to the green sand, 2) apply a thermomechanical process to at least part of a green sand fraction that has been subjected to the first mechanical process, and 3) Apply a second mechanical process to at least part of the green sand fraction that has been subjected to both the first mechanical process and the thermomechanical process. Petition 870250079879, dated 05 / 09 / 2025, pages 66 / 94 4 / 20

[015] The objective of the first mechanical process applied to green sand is to mechanically release the clay-based binder and carbon that is normally included in the binder of regenerable green sand.

[016] The objective of the thermomechanical process applied to at least part of the green sand fraction that has undergone the first mechanical process is to direct to this green sand fraction both a mechanical process to separate the carbon from the remaining binder in this green sand fraction and a thermal process to burn said carbon and evaporate the crystalline water in the binder still remaining in said green sand fraction.

[017] The objective of the second mechanical process applied to at least part of the green sand fraction that has undergone both the first mechanical process and the thermomechanical process is to mechanically separate the binder that still remains in said green sand fraction, in order to provide regenerated sand.

[018] Figure 2 schematically shows an apparatus 10 for regenerating green sand. Apparatus 10 in Figure 2 comprises a green sand pre-processing step 100, in which the first mechanical process is also applied to the regenerable green sand, in addition to some other processes. Apparatus 10 in Figure 2 further comprises a thermomechanical green sand processing step 200, in which the thermomechanical process is additionally applied to at least part of the green sand fraction that has undergone the first mechanical process. In addition, apparatus 10 in Figure 2 comprises an additional green sand processing step 300, in which the second mechanical process is also applied to at least part of the green sand fraction that has undergone both the first mechanical process and the thermomechanical process, in addition to some other processes.Apparatus 10 in Figure 2 is intended only to schematically describe the construction and operation of apparatus 10 and, depending on various embodiments of apparatus 10, the configuration of apparatus 10 may differ from Figure 2.

[019] The green sand pre-processing stage 100 comprises at least one feeding device 110 that is configured to receive green sand. Petition 870250079879, dated 05 / 09 / 2025, pp. 67 / 94 5 / 20 regenerable and feed it into the regeneration process formed by the apparatus 10. The feeding device 110 may comprise, for example, a feeding container or silo and a conveyor arranged in connection with it, wherein the feeding container or silo in question is configured to receive regenerable green sand and feed it, by means of the conveyor in question, into the regeneration process.

[020] Green sand that feeds the green sand pre-processing stage 100, that is, the feeding device 110, is preferably mostly monogranular sand, i.e., sand with few lumps and various impurities, such as dust. Therefore, before the apparatus 10 for regenerating green sand there may be at least one crushing device 1 which is arranged to disintegrate, for example, molds and cores removed from foundry use, so that the sand feeding the feeding device 110 has the fewest possible number of lumps. Furthermore, after the crushing device 1, but before the actual apparatus 10 for regenerating green sand, there may be at least one separation device 2 which is arranged to separate dust or other impurities that are lighter than the sand grains from the green sand fed for regeneration, removing them from the green sand feeding the feeding device 110.The said separation can be implemented using, for example, air classification, where the said separation device 2 can be, for example, a cyclone. The green sand feed of the pre-processing stage 100 is shown schematically in Figure 2 by an arrow with the designation Fpt-in.

[021] The green sand pre-processing stage 100 comprises at least one first processing device 130 that is arranged to generate mechanical impacts applied to the green sand that feeds the regeneration process to focus a first mechanical process on the green sand. The first processing device 130 may be, for example, a grinder that is arranged to break or prepare the green sand to separate the clay-based binder and the carbon possibly contained therein from the mechanically regenerated green sand. The said Petition 870250079879, dated 05 / 09 / 2025, pp. 68 / 94 A 6 / 20 grinder could be, for example, a substantially vertical column grinder that could include, for example, a rotating screw-shaped blade or one or more vanes to create said mechanical impacts on the green sand being processed. The impacts then focused by the blade, vane or vanes directly on the green sand and the mutual friction of the sand grains that occurs within the green sand release the binder and any carbon contained therein from the surface of the sand grains. Alternatively, said grinder could be a substantially horizontal grinding mill that could comprise, for example, two drums inside one another rotating relative to each other.Next, these drums create mechanical impacts on the green sand supplied between the drums, so that both the impacts focused by the drums directly on the green sand and the mutual friction of the sand grains that occurs within the ground green sand release the clay-based binder and the carbon possibly contained within it from the surfaces of the sand grains.

[022] The first mechanical process produced by said at least one first processing device 130 is preferably focused on dry green sand, i.e., green sand that contains no moisture or has at least a very low moisture content, i.e., preferably below 1%. As the moisture content of the green sand supplied from the casting process to regeneration is normally greater than 1%, conventionally 1-2%, it is possible to remove the moisture from the green sand supplied to the first processing device 130 by at least one moisture removal device 120, so that the green sand supplied to the first processing device 130 contains no moisture or has very little moisture, i.e., its moisture content is preferably less than 1%.

[023] In the moisture removal device 120, moisture, that is, water or a water additive and some additive, is removed from the green sand. The moisture removal device 120 may comprise, for example, at least one liquid-solid separator for separating, from the green sand, liquid, that is, water or a water additive and some additive that has turned into water from the green sand. Petition 870250079879, dated 05 / 09 / 2025, pp. 69 / 94 7 / 20 The separated liquid is shown schematically in Figure 2 by an arrow designated SLQ. The separated liquid SLQ in the moisture removal device 120 can be provided for further processing, for example, to recover the chromite that has transformed in it. The moisture removal device 120 may also include, at least in addition to or instead of a liquid-solid separator, at least one heater to evaporate moisture from the green sand that feeds the first processing device 130. The heater may utilize, for example, heat recovered in the thermomechanical processing step 200, as shown schematically in Figure 2 by an arrow designated RHE.The moisture removal device 120 aims, therefore, to remove moisture from the green sand that feeds the first processing device 130, so that the moisture content of the green sand fraction that follows in the regeneration process from the moisture removal device 120, which feeds the first mechanical process, is preferably less than 1%. If the green sand feeding the regeneration process does not contain moisture, there is no need for the moisture removal device 120.

[024] According to one embodiment, the first processing device 130 can also be combined with the feeding device 110. Then, the moisture removal device 120, possibly included in the apparatus 10, is located before said combination of the feeding device 10 and the first processing device 130 in the direction of the flow of regenerable green sand.

[025] From the first processing device 130, the green sand fraction that has undergone the first mechanical process is conveyed to at least one separation device 140 which is arranged to separate the clay-based binder and the carbon released from the clay-based binder from the green sand fraction that has undergone the first mechanical process. The clay-based binder released from the green sand and the carbon released from the binder can be recovered for further processing and / or use, as shown schematically in Figure 2 by an arrow designated as FPU. Separation of the clay-based binder released from the green sand Petition 870250079879, dated 05 / 09 / 2025, pp. 70 / 94 8 / 20 and the carbon released from the binder of the green sand that has undergone the first mechanical process can be implemented, for example, by means of air classification, wherein said separation device 140 can be, for example, a cyclone.

[026] The green sand fraction from separation device 140, which has undergone the first mechanical process, and from which as much as possible of the clay-based binder released from the green sand and the carbon released from the binder is directed to at least one vibrator 150, where the sand is set in vibratory motion with the aim of breaking up the lumps still present in the sand at this stage, in order to reduce their number or size.

[027] From vibrator 150, the green sand that has undergone the first mechanical process is conveyed to at least one magnetic separator 160, which is arranged to separate ferromagnetic materials, such as, for example, chromite or steel, which may remain in the green sand collected from a foundry, from the fraction of green sand that has undergone the first mechanical process. Said magnetic separator 160 may include one or more permanent magnets or electromagnets, depending on the amount of material flow being processed or the separation capacity required. According to one embodiment, the magnetic separation implemented by the magnetic separator 160 may also be implemented in connection with the vibrator 150.

[028] From the magnetic separator 160, the green sand fraction that has undergone the first mechanical process is sent to at least one mixing device 170, where an additive is added and mixed with the green sand fraction that has undergone the first mechanical process, the purpose of which is to promote the removal of alkali metals or compounds remaining in the clay-based binder, such as potassium, from the green sand being regenerated. Said additive may be, for example, a substance containing aluminum silicate Al2SiO5 (Al2O3^SiO2) or aluminum hydroxysilicate (OH)4 (Al2O3^2SiO2^2H2O). The purpose of said additive is to increase the melting temperature of the oxides or compounds of alkali metals in the clay-based binder that remains in the green sand being regenerated and, Petition 870250079879, dated 05 / 09 / 2025, pp. 71 / 94 9 / 20 thus, to prevent said metals and alkaline compounds from reacting with silicon dioxide on the surface of a sand grain and adhering to the surface of the sand grain. The additive thus reacts with the metals or alkaline compounds in the clay-based binder that remain in the green sand being regenerated and forms alkaline salts that are at least partially melted at the temperature used in the thermomechanical process and, by means of said alkaline salts that are at least partially melted, promotes the removal of impurities comprising said metals or alkaline compounds from the green sand being regenerated during the thermomechanical processing step 200. Said mixing device 170 may be, for example, a screw feeder.The said additive can be added directly to the mixing device 170, as shown schematically in Figure 2, or to a fraction of green sand to be supplied by at least one dosing device 180, as shown schematically by an arrow designated BC in Figure 2. The content of said additive in the composition formed by the green sand being regenerated and the additive can be, for example, 0.5-3 percent by weight. The higher the content of the additive used in the composition of the green sand and the additive, the lower the pH and electrical conductivity of the regenerated sand. Since a significant amount of binders has already been removed from the green sand being regenerated during the first mechanical process focused on it, the amount of additive to be added to the green sand supplied for thermomechanical regeneration relative to the amount of said green sand can be kept very small.

[029] A composition of the green sand fraction that has undergone the first mechanical process and the additive mixed with it feeds the thermomechanical processing stage 200, in which the green sand fraction in question is further regenerated by simultaneously focusing a thermal and a mechanical process on it. In apparatus 10 of Figure 2, the thermomechanical processing stage 200 is carried out by a heated rotary kiln 210, which can be referred to hereafter as kiln 210. The heated rotary kiln 210 can be called a heated rotary kiln and rotary kiln. The heated rotary kiln 210 can be called a rotary kiln. Petition 870250079879, dated 05 / 09 / 2025, pp. 72 / 94 10 / 20 heated.

[030] The reheatable rotary kiln 210 of Figure 2 is substantially cylindrical and comprises a first end 210a and a second end 210b substantially opposite to the first end 210a in the longitudinal direction of the kiln 210. The green sand that feeds, from the pre-processing stage 100, the thermomechanical green sand processing stage 200 is supplied to the kiln 210 at its first end 210a, as shown schematically by an arrow designated Ftm-in in Figure 2, and the green sand that has passed through the kiln 210, i.e., has passed through the thermomechanical processing stage 200, is removed from the kiln 210 at its second end 210b, as shown schematically by an arrow designated Ftm-out in Figure 2.

[031] On the inner wall of the 210 oven, there is usually one or more elevators. 212, extending in the direction of the furnace diameter 210 from the inner wall of furnace 210 at least partially towards the center of the furnace and in the longitudinal direction of furnace 210 substantially from the direction of the first end 210a of furnace 210 towards the second end 210b of furnace 210. The lifters 212 are shown in Figure 2 very schematically by a dashed line. Each lifter 212 is arranged, when furnace 210 rotates about its geometric axis of rotation, to capture at least part of the green sand that feeds furnace 210 along with it, so that said part of green sand moves along furnace 210 in the inner circle of furnace 210 until the part in question of the sand falls back to the bottom of furnace 210.Oven 210 is rotated by a variable speed motor 214 so that the rotational speed of oven 210 is normally about 5 to 20 revolutions per minute, depending, for example, on the diameter and / or filling factor of oven 210.

[032] The elevators 212 can be arranged in an inclined position schematically shown in Figure 2 to guide and increase the passage of green sand from the direction of the first end 210a of the furnace 210 towards its second end 210b. A similar effect can be provided or can Petition 870250079879, dated 05 / 09 / 2025, pp. 73 / 94 11 / 20 can be intensified by arranging furnace 210 in an inclined position, so that the first end 210a of furnace 210 is in a higher position relative to the second end 210b of furnace 210, as shown schematically in the embodiment of Figure 2. The total degree of inclination provided by said position of the elevators 212 and / or furnace 210 from the first end 210a to the second end 210b of furnace 210 can be, for example, 0.5-5 degrees.

[033] The furnace 210 of Figure 2 further comprises at least one heating device 216 which is arranged to heat the internal volume of furnace 210 and the green sand fraction that feeds the furnace. In Figure 2, the heating device 216 is arranged at the first end 210a of furnace 210, but alternatively, it would be possible to arrange the heating device 216 in the internal volume of furnace 210, for example, in the vicinity of the first end 210a of furnace 210. The heating device 216 could be, for example, a gas burner, a plasma gas burner, a liquid gas burner or any other burner. Instead of or in addition to the burner, it is also possible to use some other device to heat the internal volume of furnace 210 and the green sand fraction that feeds the furnace 210. The first end 210a could be called the feed end.

[034] The furnace 210 of Figure 2 further comprises at least one air exhaust device 218, such as, for example, an air extractor or an exhaust fan, which is arranged to remove combustion gases and fine particles, such as combustion dust, generated during the processing of the green sand fraction from the internal volume of the furnace 210. In Figure 2, the air exhaust device 218 is arranged at the second end 210b of the furnace 210, but alternatively, it would be possible to arrange the air exhaust device 218 in the internal volume of the furnace 210, for example, in the vicinity of the second end 210b of the furnace 210. In connection with the air exhaust device 218 or its combustion gas channel, it is possible to arrange at least one heat recovery device 220 which is arranged to recover heat from the combustion gases extracted from the furnace. The Petition 870250079879, dated 05 / 09 / 2025, pp. 74 / 94 12 / 20 Recovered heat can be used, for example, in the manner described above in the green sand pre-processing stage 100 to remove moisture from the green sand being processed and / or to preheat the green sand fraction that feeds the thermomechanical processing stage 200. The power of the air exhaust device 218 is adjusted, for example, based on the filling factor of the furnace 210, so that the amount of air flowing through the furnace 210 is, for example, about 1,000 to 3,000 normal cubic meters per hour. Said air can flow inside the furnace 210, for example, through the same channel as the green sand fraction that feeds the thermomechanical process that feeds the furnace 210 or through one or more air supply channels 240 arranged separately in connection with the furnace 210.

[035] In apparatus 10 of Figure 2, a fraction of green sand, which has undergone the first mechanical process and to which the aforementioned additive is added, feeds furnace 210 at its first end 210b, where the green sand fraction in question preferentially passes to the bottom of furnace 210 through a flame from a burner used as a heating device 216, so that the heating of the green sand fraction in furnace 210 begins effectively. Simultaneously, furnace 210 is rotated by rotary motor 214, whereby each elevator 212 is arranged to capture at least part of the green sand fraction feeding the furnace, so that part of the green sand fraction in question moves along furnace 210 in the inner circle of furnace 210 until it falls back to the bottom of furnace 210, sand grains thus forming a kind of sand cloud inside furnace 210.This sand cloud formation allows for substantially uniform heating of the green sand fraction within the volume of furnace 210. The temperature of the green sand fraction processed in furnace 210 can be measured by a temperature sensor, and the measured temperature can be used to adjust, for example, the power of the heating device 216 and / or the rotation speed of furnace 210, so that the green sand fraction reaches a suitable temperature and delivery time in terms of regeneration in furnace 210. The temperature of the green sand fraction in furnace 210 during its thermomechanical process is preferably... Petition 870250079879, dated 05 / 09 / 2025, pp. 75 / 94 13 / 20 at approximately 500-850 °C and its delivery time is approximately 10-60 minutes.

[036] The rotation of the green sand being regenerated along the furnace 210 and its fall to the bottom of the furnace causes focused mechanical impacts on the green sand being regenerated, i.e., a mechanical process focused on the green sand fraction that is processed in the furnace, from the effect of which the clay-based binder detaches from the surface of the sand grains and carbon-containing dust is released from the clay-based binder. The carbon released from the clay-based binder burns in furnace 210, which reduces the amount of dust created in the process. Combustion gases created in the burning and unburned fine particles along with them are extracted from the furnace by the air exhaust device 218.

[037] Heating the green sand being regenerated in the furnace concentrates a thermal treatment on the green sand fraction processed in the furnace, from the effect of which the crystalline water in the clay-based binder remaining on the surface of a sand grain evaporated from the binder. When said crystalline water evaporates from the binder, it becomes easier to release the binder from the surface of the sand grain in the additional processing step 300, which occurs after the thermomechanical processing step, in which a second mechanical process is directed to at least part of the green sand fraction that has passed through the thermomechanical processing step 200.

[038] As mentioned above, an aluminum silicate-based additive is mixed into the green sand fraction that feeds the furnace, the purpose of which is to promote the removal of alkali metals or compounds, such as potassium, remaining in the clay-based binder of the green sand being regenerated, so that the additive reacts with oxides or compounds of alkali metals in the binder remaining in the green sand fraction that feeds furnace 210, thus forming, at the process temperature of the sand in furnace 210, such as, for example, at a temperature of 500-850 °C, at least partially melting the alkali salts. At least partially melted alkali salts are created in the green sand fraction processed in furnace 210, where the impurities originating from the binder in the green sand that is Petition 870250079879, dated 05 / 09 / 2025, pp. 76 / 94 14 / 20 being regenerated adhere to the partially or totally molten alkaline salts and form grains when adhered together. These grains also collect from the green sand fraction being regenerated both sand grains and particles of impurities still remaining in the green sand fraction, thus forming agglomerates that resemble grains with a diameter of, for example, about 5-10 millimeters, which can be separated from the green sand coming out of furnace 210 in known ways, such as, for example, by sieving.

[039] The addition of an additive containing aluminum silicate to a green sand fraction being regenerated in the thermomechanical process causes the impurities in the sand to agglomerate and form, depending on the apparatus used for the thermomechanical process and / or its method of application, grain-like agglomerates with a diameter of, for example, about 5 to 10 millimeters, which pass along the sand being regenerated and transport alkali metals or compounds adhered to them and other impurities along them until they are separated from the processed sand. The use of rotary kiln 210 for the thermomechanical process of the green sand fraction promotes contact between different particles and thus enables these particles to impact each other sufficiently to form said grains.

[040] The green sand exiting the second end 210b of furnace 210 and the agglomerates remaining therein feed at least one separation device 230, which is configured to separate the agglomerates created in said thermomechanical green sand process from the green sand fraction originating from furnace 210, before the second mechanical process is directed to the green sand fraction exiting furnace 210, i.e., the green sand fraction that has undergone both the first mechanical process and the thermomechanical process. Said separation device 230 may include, for example, one or more sieves whose meshes are sized so that said agglomerates do not pass through the sieve assembly. The green sand fraction that has passed through the separation device 230 forms the green sand fraction that has undergone both the first mechanical process and Petition 870250079879, dated 05 / 09 / 2025, pp. 77 / 94 15 / 20 by the thermomechanical process to feed the additional processing stage 300, which comprises the second mechanical process, the fraction of which is directed in the regeneration process to the additional processing stage 300, as shown schematically by an arrow designated Fat-in in Figure 2. The agglomerates separated by the separation device 230 are removed from the regeneration process as waste for further processing, as shown schematically by an arrow designated WT in Figure 2.

[041] The green sand fraction that has undergone both the first mechanical process and the thermomechanical process then feeds into the additional processing stage 300, where the green sand fraction in question is further regenerated by applying the second mechanical process to it. In apparatus 10 of Figure 2, the second mechanical process is carried out in a rotary kiln 310, which simultaneously constitutes a cooling device, i.e., a cooling furnace, to cool the sand fraction heated in the thermomechanical process. In other words, the second mechanical process is carried out in the cooling furnace 310 to cool the sand fraction heated in the thermomechanical process.

[042] The rotary kiln 310 of Figure 2 is substantially cylindrical and comprises a first end 310a and a second end 310b which is substantially opposite to the first end 310a in the longitudinal direction of the kiln 310. The green sand that feeds the thermomechanical green sand processing stage 200 to the further green sand processing stage 300 feeds the kiln 310 at its first end 310a, as shown schematically by an arrow designated Fat-in in Figure 2, and the regenerated and cleaned sand that has passed through the kiln 310, i.e., that has also passed through the second mechanical processing stage, is removed from the kiln 310 at its second end 310b, as shown schematically by an arrow designated Fat-out in Figure 2.Oven 310 is rotated by variable speed motor 314 so that the rotational speed of oven 310 is normally about 5 to 20 revolutions per minute and the residence time of the processed sand in oven 310 is through the oven. Petition 870250079879, dated 05 / 09 / 2025, pp. 78 / 94 16 / 20 310 oven cooking time can range from approximately 5 to 30 minutes, depending, for example, on the diameter and / or fill factor of the 310 oven.

[043] The furnace 310 of Figure 2 comprises at least one second processing device 320 in the first part of the furnace 310 in the vicinity of the first end 310a, which device is arranged to produce focused mechanical impacts on the green sand feeding the furnace 310 in order to focus the second mechanical process on said green sand. The second processing device 320 may be, for example, a grinder which is arranged to grind the green sand feeding the furnace 310 in order to mechanically release any clay-based binder that may still be present in it from the fraction of green sand being regenerated that feeds the furnace 310.The said grinder may be a ball mill, which is shown schematically and partially open in Figure 2, the ball mill comprising balls 322 placed inside furnace 310 which, when furnace 310 rotates, move within furnace 310 and, as they move, provide focused mechanical impacts on the green sand to focus the second mechanical process on the green sand. As the crystalline water has been removed from the clay-based binder, possibly still in the green sand fraction, to feed furnace 310 during the thermomechanical process, the binder is more easily released from the surface of the sand grains in this second sand-focused mechanical process due to the impacts directed at the sand and the mutual friction of the sand grains.

[044] In the apparatus of Figure 2, at least one second processing device 320 was therefore integrated into furnace 310 to focus the second mechanical process on at least part of the green sand fraction that has passed through both the first mechanical process and the thermomechanical process. However, it is said that at least one second processing device 320 may also be a device separate from furnace 310 located before furnace 310 in the direction of the flow of sand being regenerated.

[045] The inner wall of the 310 furnace usually includes one or more elevators. 312, which extend in the direction of the furnace diameter 310 from the inner wall. Petition 870250079879, dated 05 / 09 / 2025, pp. 79 / 94 17 / 20 of furnace 310 towards the center of the furnace and in the longitudinal direction of furnace 310 substantially from the direction of the first end 310a of furnace 310 towards the second end 310b of furnace 310. The lifters 312 are shown very schematically by a dashed line in Figure 2. Each lifter 312 is arranged, when furnace 310 rotates around its geometric axis of rotation, to capture at least part of the green sand feeding furnace 310 from the bottom of furnace 310 along with it, so that this part of green sand moves along furnace 310 in the inner circle of furnace 310 until the part in question of the green sand and, together with it, the binder released from the sand and other fine particles possibly present in the sand, fall back to the bottom of furnace 310.The said binder and other fine particles lighter than sand form a cloud of combustion dust inside furnace 310, which cloud is removed from furnace 310 in a manner described in more detail later.

[046] The elevators 312 can be arranged in an inclined position schematically shown in Figure 2 to guide and increase the passage of green sand from the direction of the first end 310a of the furnace 310 towards its second end 310b. A similar effect can be provided or intensified by arranging the furnace 310 in an inclined position, so that the first end 310a of the furnace 310 is in a higher position relative to the second end 310b of the furnace 310, as shown schematically in the embodiment of Figure 2. The total degree of inclination provided by said position of the elevators 312 and / or the furnace 310 from the first end 310a to the second end 310b of the furnace 310 can be, for example, 0.5-5 degrees. These degrees are compared to the horizontal level.

[047] The furnace 310 of Figure 2 further comprises at least one air exhaust device 330 which is disposed at the first end 310a of the furnace 310 outside the furnace 310. Alternatively, if possible, the air exhaust device 330 may be, at least to some extent, disposed in the internal volume of the furnace 310 at the first end 310a of the furnace 310. Said air exhaust device Petition 870250079879, dated 05 / 09 / 2025, pages 80 / 94 18 / 20 330 could be, for example, an air extractor or an exhaust blower. The air exhaust device 330 is arranged, together with an air supply channel 340 disposed at the second end of furnace 310 that goes from the outside of furnace 310 to the internal volume of furnace 310, to produce an airflow that runs from the direction of the second end 310b of furnace 310 towards the direction of the first end 310a of furnace 310 and through the air exhaust device 330 out of furnace 310. Said airflow, which comprises air drawn from the external environment of furnace 310, normally at the temperature of the furnace 310 environment, forms within furnace 310 a cooling airflow flowing from the direction of the second end 310b of furnace 310 towards the first end 310a of furnace and further through the air exhaust device 330 out of furnace 310 to cool the green sand fraction in furnace 310.Simultaneously, the aforementioned airflow removes the binder released from the sand and other fine particles lighter than sand, possibly still remaining in the sand of furnace 310.

[048] The power of the air exhaust device 17 is controlled so that only the binder released from the sand and other fine particles possibly still contained in the sand pass through the cooling airflow out of furnace 310 without carrying away sand clean of binder and other impurities. Said binder and fine particles can be separated in the airflow by means of a filter, or something similar, and guided for further processing. If air is available cooled to a temperature lower than the ambient temperature surrounding furnace 310, this cooled air can also be used to cool the green sand fraction processed in furnace 310. The power of the air exhaust device 330 is adjusted, for example, based on the filling factor of furnace 310, so that the amount of air flowing through furnace 310 is, for example, about 1,000 to 3,000 normal cubic meters per hour.

[049] The regenerated clean sand that has passed through furnace 310, that is, has passed through the first mechanical process, the thermomechanical process and the second mechanical process, is removed from furnace 310 at its second end 310b, as Petition 870250079879, dated 05 / 09 / 2025, pages 81 / 94 19 / 20 shown schematically by an arrow labeled Fat-out in Figure 2.

[050] Apparatus 10 of Figure 2 further comprises at least one classification device 350 which is arranged to receive the green sand fraction that has passed through the furnace 310 and to classify it into at least two different regenerated sand fractions in terms of grain size, which are shown schematically by arrows designated RS1 and RS2 in Figure 2. Said classification device may include, for example, one or more sieves. According to one embodiment, the sieve mesh may be, for example, 2 millimeters, so that a first fraction RS1 that has passed through the screen may be directed to be used for some specific use, such as, for example, to be reused as foundry sand, and a second fraction RS2 that has not passed through the screen, i.e., coarse fraction, may be directed to be used for some other use.

[051] The solution comprising the first mechanical process, the thermomechanical process and the second mechanical process in sequence to regenerate green sand effectively regenerates foundry sand, which comprises a clay-based binder. If an aluminum silicate-based additive is added to the sand fraction to feed the thermomechanical regeneration, it is also possible to effectively remove metals or alkaline compounds from the regenerating sand, which, by remaining on the surface of a sand grain, can impede the binder's function when using the regenerated sand and prevent or at least weaken the usefulness of the regenerated sand, for example, as foundry sand. In addition, the recovery of the binder and the carbon released from it in the pre-processing step of the sand being regenerated increases the total amount of various materials recovered and reused from the process.

[052] In apparatus 10 of Figure 2, at the end of the pre-processing stage 100, an additive is added and mixed with a fraction of green sand to feed the thermomechanical processing stage 200 to promote the removal of metals or alkaline compounds in the clay-based binder still remaining in the green sand being regenerated from the green sand being regenerated in Petition 870250079879, dated 05 / 09 / 2025, pages 82 / 94 20 / 20 thermomechanical processing stage. However, the solution presented can also be used in such a method and apparatus where none of the aforementioned additives are added to the green sand to feed the thermomechanical processing stage 200, but where the thermomechanical process is directed to green sand that has undergone the first mechanical process, from which, to the greatest extent possible, the clay-based binder and carbon released in the first mechanical process, and preferably also the ferromagnetic material, have been removed. When the aforementioned additive is not added to the green sand to feed the thermomechanical processing stage 200, the removal of metals or alkaline compounds in the sand cannot be done from the sand being regenerated with the same efficiency. This type of regenerated sand is still very applicable for reuse in many different applications, such as, for example, an aggregate in various products, such as concrete, in the construction industry.

[053] Those skilled in the art will find it obvious that, as technology advances, the basic idea of ​​the invention can be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above, but may vary within the scope of the claims. Petition 870250079879, dated 05 / 09 / 2025, pp. 83 / 94

Claims

1 / 4 CLAIMS 1. A method for regenerating green sand, wherein the method removes moisture from the green sand before applying a first mechanical process to the green sand, applies the first mechanical process to the green sand, in which the green sand is ground in at least one grinder to separate the clay-based binder and the carbon in the binder from the green sand, separates from the ground green sand, by at least one separation device, the binder and the carbon released from the green sand to form a fraction of green sand that has undergone the first mechanical process, applies a thermomechanical process to at least part of a fraction of green sand that has undergone the first mechanical process, and applies a second mechanical process to at least part of the fraction of green sand that has undergone both the first mechanical process and the thermomechanical process, characterized in that, in the second mechanical process,Grind at least part of the green sand fraction that has undergone the first mechanical process and the thermomechanical process to release the clay-based binder from said green sand fraction, in order to form regenerated green sand that has undergone the first mechanical process, the thermomechanical process, and the second mechanical process.

2. Method, according to claim 1, characterized by, in the thermomechanical process of green sand, feeding, with a fraction of green sand that has passed through the first mechanical process, a heated rotary kiln (210), whereby both a mechanical process to separate the carbon from the clay-based binder remaining in said green sand fraction and a thermal process to burn off that carbon and evaporate the crystalline water from the clay-based binder remaining in said green sand fraction are directed.

3. Method, according to claim 1 or 2, characterized by adding and mixing at least one additive to the green sand fraction to be processed thermomechanically to increase the melting temperature of metals or alkaline compounds in the green sand, whereby, in said thermomechanical process, said at least one additive and the metals or alkaline compounds react, thereby producing partially or totally molten alkaline salts that collect sand and impurity particles during the thermomechanical process, thus forming agglomerates that are separable from the green sand fraction that has undergone the thermomechanical process.

4. A method according to claim 3, characterized by separating, by at least one separation device, the agglomerates created in the thermomechanical process from the green sand fraction that underwent the thermomechanical process before directing the second mechanical process to the green sand fraction that underwent both the first mechanical process and the thermomechanical process.

5. Method according to claim 3 or 4, characterized in that the additive comprises at least aluminum silicate.

6. A method according to claim 1, characterized by feeding at least one crusher with a fraction of green sand that has been subjected to both the first mechanical process and the thermomechanical process, grinding said green sand fraction to release the clay-based binder from the green sand, and removing the binder released in the grinding process from the crusher to form regenerated green sand that has undergone the first mechanical process, the thermomechanical process, and the second mechanical process.

7. Method according to claim 1 or 6, characterized in that the second mechanical process is carried out in a cooling furnace (310) to cool the sand fraction heated in the thermomechanical process.

8. Apparatus (10) for regenerating green sand, wherein the apparatus comprises at least one moisture removal device (120) for removing moisture from the green sand to feed a first processing device Petition 870250079879, dated 05 / 09 / 2025, pp. 92 / 94 3 / 4 (130), at least one first processing device (130) disposed to provide mechanical impacts applied to the green sand to focus a first mechanical process on the green sand, the first processing device (130) being a crusher disposed to crush the green sand to release the clay-based binder from the green sand, at least one separation device (140) for separating from the ground green sand the binder and carbon released from it, in order to form a green sand fraction that has undergone the first mechanical process,at least one reheatable rotary kiln (210) for directing a thermomechanical process to at least part of the green sand fraction that has undergone the first mechanical process, and at least one second processing device (320) that is arranged to provide mechanical impacts applied to the green sand in order to focus a second mechanical process on at least part of the green sand fraction that has undergone both the first mechanical process and the thermomechanical process, characterized in that the second processing device (320) is a grinder that is arranged in the second mechanical process to grind at least part of the green sand fraction that has undergone the first mechanical process and the thermomechanical process to release the clay-based binder therein to form regenerated green sand that has undergone the first mechanical process, the thermomechanical process and the second mechanical process.

9. Apparatus, according to claim 8, characterized in that the rotating and heatable rotary kiln (210) is arranged to focus both a mechanical process for separating the carbon from the clay-based binder remaining in said green sand fraction and a thermal process for burning said carbon and for evaporating the crystalline water from the clay-based binder remaining in said green sand fraction to the green sand fraction that has undergone the first mechanical process.

10. Apparatus, according to claim 8 or 9, wherein the apparatus Petition 870250079879, dated 05 / 09 / 2025, pp. 93 / 94 4 / 4 is characterized by comprising at least one dosing device (180) for adding at least one additive to a green sand fraction to be processed in the thermomechanical process to increase the melting point temperature of metals or alkaline compounds in the green sand, and at least one mixing device (170) for forming a mixture of the green sand fraction processed in the thermomechanical process and an additive, whereby, in said thermomechanical process, at least one additive and metals or alkaline compounds react producing at least partially or totally molten alkaline salts which, during the thermomechanical process, collect sand particles and impurities, thus forming separable agglomerates of the green sand fraction that was subjected to the thermomechanical process.

11. Apparatus (10), according to claim 10, characterized in that the apparatus (10) comprises at least one separation device (230), which is arranged to separate the agglomerates created in the thermomechanical process from the green sand fraction that has undergone the thermomechanical process before directing the second mechanical process to the green sand fraction that has undergone the thermomechanical process.

12. Apparatus (10), according to claim 8, characterized in that the apparatus (10) further comprises a cooling furnace (310), and that said grinder is a ball mill comprising balls (322) placed within the cooling furnace (310) which, when the furnace (310) rotates, move within the furnace (310) and, by moving, provide focused mechanical impacts on the green sand to focus the second mechanical process on the green sand. Petition 870250079879, dated 05 / 09 / 2025, p. 94 / 94

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