Apparatus and method for recycling industrial sand using additives
The addition of aluminum silicate additives to industrial sand, forming molten alkali salts that adhere to impurities, addresses the issue of binders and impurities, improving sand quality for reuse by enhancing its properties and meeting industrial standards.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-19
- Publication Date
- 2026-03-13
AI Technical Summary
Used industrial sand often fails to meet requirements due to the presence of binders and impurities, particularly alkali metals, which hinder its reuse by adhering to the sand and interfering with the action of binders, leading to the need for additional binder usage.
A method involving the addition of aluminum silicate-based additives to industrial sand, followed by heating and causing relative motion to form molten alkali salts that adhere to impurities, forming granules, which are then separated from the sand.
Substantially removes binders and impurities, enhancing the sand's suitability for reuse by improving its properties such as hardness and reducing interference with binders, thus meeting industrial requirements.
Smart Images
Figure 2026508963000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the regeneration of industrial sand by using additives. In particular, the present invention relates to the thermomechanical regeneration of industrial sand by using additives.
Background Art
[0002] Generally, various requirements regarding strength, loss on ignition, acid demand value, pH value, and / or particle shape are set for industrial sand according to its use. These requirements are not always met by used industrial sand. This is because used industrial sand contains binders (adhesives) and impurities adhering to the sand, which hinders the realization of at least some of the above requirements.
[0003] According to one method, industrial sand can be regenerated thermally in a fluidized bed reactor, and according to another method, industrial sand can be regenerated thermomechanically in a rotary kiln, i.e., a combustion furnace. However, since the thermally or thermomechanically regenerated industrial sand still contains adhering binders and impurities, the regenerated industrial sand does not meet at least some of the requirements set for its use.
Summary of the Invention
[0004] An object of the present invention is to provide a new type of apparatus and method for regenerating industrial sand.
[0005] The method according to the present invention is characterized by adding an aluminum silicate-based additive to industrial sand. Furthermore, the method includes heating the industrial sand and the additive added to the industrial sand to react the additive with impurities in the industrial sand, including at least alkali metals, to form at least partially molten alkali salts. In addition, the method includes causing relative motion between the heated industrial sand and the alkali salt to cause at least some of the remaining impurities in the industrial sand to adhere to the alkali salt, thereby forming granular material. Furthermore, the method includes separating the industrial sand to remove the granular material from the industrial sand.
[0006] The apparatus according to the present invention is characterized by comprising a feeding device (feeder) for supplying industrial sand and additives to a processing device. Furthermore, the apparatus comprises a processing device for heating the industrial sand and the additives added to the industrial sand to cause relative motion between the industrial sand and the additives added to the industrial sand. The apparatus further comprises a separation device configured to separate the industrial sand in order to remove granular material from the industrial sand.
[0007] The advantage of the method and apparatus according to the present invention is that binders and impurities are substantially removed from industrial sand by the physicochemical treatment performed in the apparatus. Some embodiments of the present invention are shown in the dependent claims. [Brief explanation of the drawing]
[0008] The present invention will be described in more detail below in relation to preferred embodiments with reference to the accompanying drawings.
[0009] [Figure 1] This outlines methods for recycling industrial sand. [Figure 2] This outlines another method for recycling industrial sand. [Figure 3] The apparatus for carrying out the methods shown in Figures 1 and 2 is shown in a very schematic manner. [Figure 4] A very schematic diagram shows another apparatus for carrying out the method in Figure 1. [Modes for carrying out the invention]
[0010] Industrial sand refers to renewable sand used in industries such as foundry work. Industrial sand may be, for example, phenolic resin sand containing an organic resin (organic binder) as a binder and additives added to the binder. In this case, the additives added to the binder may be, for example, ester hardeners. Industrial sand may also be green sand containing at least bentonite as a binder and additives added to the binder. In this case, the additives added to the binder may be, for example, carbon. Industrial sand may also be furan resin sand. Industrial sand may contain impurities including alkali metals (e.g., potassium and / or sodium). Impurities in industrial sand may be present in the binder of the industrial sand and on the surface of the sand grains. Depending on the end use, industrial sand may be subject to requirements regarding sand hardness, loss on ignition (LOI), acid requirement (ADV), sand grain shape, and / or cracks that may occur in the sand grains. It should be noted that industrial sand may refer to renewable sand used, for example, in the power industry. As a binder, power plant sand may contain, for example, clay-based impurity films.
[0011] For example, when industrial sand is regenerated thermomechanically, it is heated and mechanically moved in a kiln. While the binders in the industrial sand are at least partially removed as a result of the heat and collision, impurities on the surface of the sand or sand grains are not completely removed. When thermally or thermomechanically regenerated industrial sand is reused, these impurities can hinder its use. For example, these impurities can interfere with the action of binders added to the sand, negatively impacting the requirements for industrial sand. For instance, thermally or thermomechanically regenerated green sand may contain impurities including alkali metal compounds such as potassium residue. Such impurities interfere with the action of binders such as bentonite in green sand used in the foundry industry. This prevents the achievement of the target hardness set for the industrial sand. When the action of the binder is hindered, it may lead to the use of more binder in the industrial sand to achieve the set requirements.
[0012] Figure 1 shows one method for recycling industrial sand. Figure 2 shows another method for recycling industrial sand. Figure 3 shows an apparatus equipped with a processing device 300 based on a thermomechanical operating principle. In this case, the processing device 300 is a rotary kiln 300A (i.e., a combustion kiln). Figure 4 shows an apparatus equipped with a processing device 300 based on a thermal operating principle. In this case, the processing device 300 is a fluidized bed reactor 300B.
[0013] The apparatus in Figures 3 and 4 comprises a feeder 220, a processing unit 300, and a separation unit 400. The feeder 220 is configured to supply industrial sand and additives to the processing unit 300. More specifically, the feeder 220 is configured to supply industrial sand and additives added thereto to the processing unit 300. The additives will be described in more detail later. The processing unit 300 is configured to heat (120) the industrial sand and additives added thereto. This causes the additives to react with impurities in the industrial sand, including at least alkali metals, to form at least partially molten alkali salts. In addition, the processing unit 300 is configured to perform a step (130) that causes the heated industrial sand and alkali salts to move relative to each other. This causes at least some of the remaining impurities in the industrial sand to adhere to the alkali salts, forming granules. More specifically, these alkali salts form granules or aggregates of granules. The separation device 400 is configured to separate industrial sand in order to remove granular material from industrial sand. The separation device 400 is configured to separate industrial sand in order to remove granular material and aggregates from industrial sand.
[0014] The removal of impurities occurs as a result of physicochemical events. Industrial sand is heated, and motion is introduced. This causes the binder in the industrial sand to burn and be removed (released). For example, carbon in industrial sand burns away due to the effect of heat. Industrial sand and additives added to it are heated to, for example, 500-850°C, 600-800°C, 650-750°C, or 700-750°C. The additives react with impurities in the industrial sand and impurities removed (released) from the industrial sand to form at least partially molten alkali salts. More specifically, the additives react with impurities in the binder of the heated industrial sand to form at least partially molten alkali salts. These impurities are in a molten state at this stage of reaction with the additives. For example, aluminum silicate-based additives, aluminum hydroxide silicate-based additives, or kaolin-containing additives react with impurities in heated industrial sand, thereby forming at least partially molten alkali salts. In addition, the heated industrial sand and the at least partially molten alkali salt are subjected to relative motion with respect to each other. This causes at least some of the impurities remaining in the industrial sand to adhere to the alkali salt, resulting in the formation of granules. More specifically, granules are formed when at least some of the impurities remaining on the surface of the sand grains of the industrial sand adhere to the alkali salt. Furthermore, the granules agglomerate with the industrial sand and any impurities or binders present in or removed from the industrial sand, thereby increasing in size. That is, the granules form larger granules, pellets, and aggregates. It should be noted that the alkali salt melts at least partially at a temperature lower than that of the industrial sand, thereby promoting the formation of granules. It should also be noted that the at least partially molten alkali salt may be a completely molten alkali salt. For clarification, it should be noted that the alkali salt forms granules by adhering to and binding with impurities on the surface of the industrial sand, and then at least some of the granules are separated from the industrial sand.
[0015] The additive may be aluminum silicate (Al2O3-SiO2) based. The additive may also be aluminum hydroxide silicate (Al2Si2O5(OH)4(Al2O3·2SiO2·2H2O)) based. The additive may also contain andalusite, kaolin (H2Al2Si2O8·H2O), kyanite, and / or sillimanite. The aluminum silicate mineral (aluminum silicate mineral) of the additive added to industrial sand is in a solid state. The additive may contain a liquid, such as water. Thus, the additive added to industrial sand is in a liquid state (in other words, a suspension). The composition of the additive is determined so that the additive melts at a temperature higher than the temperature of the heated industrial sand. The melting point of the additive may exceed, for example, 1000°C. The additive is added to the industrial sand in such an amount as, for example, 0.2 to 5.0 weight percent, for example, 0.3 to 4.0 weight percent, or for example, 0.5 to 3.0 weight percent of aluminum silicate mineral (aluminum silicate mineral) relative to the industrial sand. The alkali salt or granular material may be at least partially molten at, for example, 500 to 850°C, for example, 500 to 700°C, for example, at least 500 to 850°C, or for example, at least 500 to 700°C. The melting point of the alkali salt or granular material may be, for example, 700 to 1100°C, for example, 700 to 850°C, or for example, at least 700 to 1100°C.
[0016] The industrial sand to be recycled is pre-treated before being supplied to the processing unit 300. The apparatus in Figures 3 and 4 includes a pre-processing unit 200. The pre-processing unit 200 includes a crushing unit 201. The crushing unit 201 is configured to crush lumps (e.g., molds) formed from industrial sand into smaller sand lumps and industrial sand. The industrial sand is sent to a classifier 202. The sand lumps are removed (see arrows 201-R in Figures 3 and 4) and, if necessary, pre-treated again in the crushing unit 201. The crushing unit 201 may be, for example, a gyratory crusher, a roll crusher, an impact crusher, a jaw crusher, a hammer crusher, or a coil crusher.
[0017] Furthermore, the pretreatment device 200 includes a classifier 202. The classifier 202 separates the industrial sand processed in the crusher 201 into different quality classes, for example, by air classification. Such quality classification may be based on, for example, the particle size of the sand. Industrial sand of a specific quality class is sent to the industrial sand container 210. The remaining industrial sand and the particles contained therein are removed for other uses (see arrows 202-R in Figures 3 and 4) or reprocessed. The classifier 202 may be connected to, for example, the crusher 201, or it may receive the sand processed in the crusher 201 by, for example, a conveyor.
[0018] Furthermore, the pretreatment device 200 includes an industrial sand container 210 (in other words, an industrial sand hopper). Crushed industrial sand having a specific quality class is stored in the industrial sand container 210 for recycling. The industrial sand container 210 may be connected to a classifier 202. The industrial sand container 210 includes a feeder for supplying industrial sand forward.
[0019] In addition, the pretreatment device 200 includes a crusher 212 for crushing industrial sand. The crusher 212 applies vibration to the industrial sand. This mechanical crushing of the industrial sand promotes the dispersion (splitting) or removal (release) of binders in the industrial sand. The crusher 212 may be, for example, a substantially vertical column crusher. The column crusher may be equipped with rotatable blades or vanes (e.g., screw-shaped) for mechanically impacting the industrial sand to be processed. This removes (releases) binders and any carbon they may contain from the surface of the sand particles by both the impact directly applied to the industrial sand by the blades (vanes) and the mutual crushing of sand particles generated within the crushed industrial sand. Alternatively, the crusher 212 may be a substantially horizontal drum crusher. The drum crusher may be equipped with, for example, two drums that rotate relative to each other (i.e., one drum that rotates inside the other). This causes the drum to mechanically impact the industrial sand being fed between the kilns. This removes (releases) the binder and any carbon it may contain from the surface of the sand grains through both the direct impact applied to the industrial sand by the drum and the mutual crushing of the sand grains within the crushed industrial sand. The crusher 212 may be connected to the industrial sand container 210. The removed binder and carbon are then removed (see arrows 212-R in Figures 3 and 4) and sent for other uses (not further described herein). The pretreatment device 200 may include an attritor (a type of agitated ball mill) for crushing industrial sand instead of the crusher 212 for crushing industrial sand. Alternatively, the crusher 212 may be an attritor.
[0020] Furthermore, the pretreatment device 200 includes a metal separator 214 for removing metals from industrial sand. The metal separator 214 may include, for example, a conveyor and a magnet connected to the conveyor. The conveyor is configured to transport industrial sand to a supply device 220, and the magnet is configured to remove metals from the industrial sand (see arrow 214-R in Figures 3 and 4). The magnet of the metal separator 214 may also be referred to as a magnet device. According to one embodiment, the supply device 220, described later, is connected to the underside of the crusher 212. In this case, the metal separator 214 is a magnet positioned in the area between the crusher 212 and the supply device 220, and removes metals and other ferromagnetic materials from the industrial sand as the industrial sand falls from the crusher 212 to the supply device 220.
[0021] The apparatus in Figures 3 and 4 includes a feeder 220 for supplying industrial sand and additives to a processing device 300. The feeder 220 is configured to receive pre-treated industrial sand. More specifically, the feeder 220 is configured to receive industrial sand that has been pre-treated in a pre-processing device 200. The feeder 220 in Figures 3 and 4 includes a conveyor 222. The conveyor 222 may be, for example, a belt conveyor. Alternatively, the feeder 220 may be, for example, a screw conveyor 222. In addition, the feeder 220 may include an additive feeder (additive supply device) 224 for adding additives to the industrial sand on the conveyor 222. The additive feeder 224 is connected to the conveyor 222. The feeder 220 allows the additives to be uniformly added to the industrial sand. More specifically, the feeder 220 allows the additives to be uniformly mixed with the industrial sand. The supply rate of the additive feeder 224 can be adjusted to reach an appropriate additive ratio. The speed of the conveyor 222 can be adjusted so that the amount of industrial sand and additive supplied is appropriate for the line speed of the processing device 300. According to one embodiment, the supply device 220 may be a gravity-based supply device 220. In this case, the industrial sand falls into the processing device 300, and the supply device 220 supplies additives in a specific ratio to the industrial sand falling into the processing device 300.
[0022] Next, the processing apparatus 300 of the apparatuses in FIGS. 3 and 4 will be described in detail. The processing apparatus 300 includes at least an inlet 302 for receiving industrial sand and an additive. The processing apparatus 300 further includes a heating device 310. The heating device 310 is configured to heat the industrial sand and the additive added thereto (see arrow 300-H in FIGS. 3 and 4). Thereby, the additive reacts with impurities including at least alkali metals in the industrial sand to form at least partially molten alkali salts. In addition, the processing apparatus 300 includes means configured to cause relative movement with respect to each other (see arrow 300-M in FIGS. 3 and 4) between the industrial sand and the at least partially molten alkali salts. Thereby, at least a part of the impurities remaining in the industrial sand adheres to the alkali salts to form granular bodies. The processing apparatus 300 further includes an outlet 304 for supplying the industrial sand and the formed granular bodies (300-F) to the separation apparatus 400.
[0023] The processing apparatus 300 in FIG. 3 is a rotary kiln 300A (in other words, a combustion kiln, a rotary furnace, a rotary reactor). The rotary kiln 300A includes a container 303 in which industrial sand is processed. The rotary kiln 300A (more specifically, the container 303 of the rotary kiln 300A) includes a first end 301A and a second end 301B. The first end 301A and the second end 301B are located at opposite ends to each other. More specifically, the container 303 is a long hollow cylindrical or tubular structure.
[0024] Furthermore, the rotary kiln 300A includes an inlet 302 for receiving industrial sand and an additive. The inlet 302 is connected to the supply device 220. The inlet 302 is located near the first end 301A. In addition, the rotary kiln 300A includes an outlet 304 for discharging industrial sand and granular bodies from the rotary kiln 300A. The outlet 304 is connected to the separation apparatus 400. The outlet 304 is located near the second end 301B. In FIG. 3, the inlet 302 and the outlet 304 of the rotary kiln 300A are located at opposite ends to each other.
[0025] Furthermore, the rotary kiln 300A includes a plurality of lifters 306 (alternatively, shovels, vanes, blades). The lifters 306 facilitate the movement of the industrial sand and the above-mentioned alkali salts within the rotary kiln 300A. The lifters 306 are disposed within the rotary kiln 300A (more specifically, within the container 303). The lifters 306 are formed to carry the industrial sand and the alkali salts from the first end 301A of the rotary kiln 300A towards the second end 301B. When the rotary kiln 300A rotates, the lifters 306 lift the industrial sand upwards, and the industrial sand falls from the lifters 306 (vanes) to the bottom of the rotary kiln 300A at a specific height. Thereby, the particles of the industrial sand collide with each other, promoting the removal (release) of the binder in the industrial sand. In addition, when the industrial sand falls from the lifters 306 (vanes) to the bottom of the rotary kiln 300A, the reception of thermal energy by the industrial sand is promoted when thermal energy is applied to the falling industrial sand.
[0026] The rotary kiln 300A further includes a base 308 (foundation). The rotary kiln 300A is located above the base 308. In FIG. 3, the base 308 is shown very schematically. The base 308 sets the rotary kiln at an angular position (tilted position) inclined with respect to the horizontal plane. This angular position enables the influence (adjustment) of the traveling speed (moving speed) of the industrial sand within the rotary kiln 300A. The base 308 may be an adjustable base for changing the angular position of the rotary kiln. The angle between the rotary kiln 300A and the horizontal plane may be, for example, from 0.5 degrees to 5.0 degrees. The adjustable base 308 may operate, for example, hydraulically.
[0027] Furthermore, the rotary kiln 300A includes a heating device 310 for heating the industrial sand and additives. The heating device 310 is configured to heat the industrial sand and the additives added thereto by supplying thermal energy to the rotary kiln 300A (see arrow 300-H in Figures 3 and 4). The heating device 310 may include, for example, a burner, an electrical resistor, a plasma source, or an induction heating device for supplying thermal energy to the rotary kiln 300A. This thermal energy may be, for example, a combustion gas, heated air applied directly to the industrial sand, or heated air applied indirectly to the industrial sand through the structure of the processing apparatus 300. The heating device 310 is connected to the first end 301A.
[0028] The rotary kiln 300A further comprises an exhaust system 320. Through the exhaust system 320, any thermal energy, air masses, and exhaust gases, as well as soot and dust, that may be present in the air located within the rotary kiln 300A are removed (see arrow 300-R in Figures 3 and 4). An exhaust gas filter for filtering the exhaust gases, a heat recovery system for recovering heat, and / or a dust filter for filtering soot and dust may be connected to the exhaust system 320. More specifically, the exhaust filter of the exhaust system 320 is for removing solid matter from the exhaust gases. The exhaust system 320 is located at the end opposite the heating device 310. In other words, the exhaust system 320 is located at the second end 301B of the rotary kiln 300A. This arrangement facilitates the efficient application of thermal energy to industrial sand.
[0029] In addition, the rotary kiln 300A is equipped with a motor 330 for rotating the rotary kiln 300A. The motor 330 is configured to rotate the rotary kiln 300A and the lifter 306 included therein, thereby rotating the industrial sand. At this time, the rotational speed of the rotary kiln 300A and the lifter may be, for example, 5 to 20 revolutions per minute (rpm). The rotation of the industrial sand promotes the supply of thermal energy to the industrial sand. The rotary kiln 300A is equipped with, for example, bearings, toothed carriers, and / or gears connected to the motor 330, as necessary means to enable the rotation of the rotary kiln 300A. The rotational speed of the motor 330 (and thus the rotational speed of the rotary kiln 300A) is adjustable. The rotational speed of the rotary kiln 300A affects the velocity of the industrial sand and, consequently, the magnitude of the force applied to the industrial sand.
[0030] Furthermore, the rotary kiln 300A includes a control unit 340 for adjusting the parameters of the rotary kiln 300A to specify the size (particle size, particle size) of the granular material formed. The control unit 340 can influence the processing time of industrial sand within the rotary kiln 300A and the physicochemical reactions that occur in the industrial sand. The control unit 340 is connected to the rotary kiln 300A as shown very schematically and schematically in Figure 3. The control unit 340 is configured to control the amount of industrial sand received and the amount of additives added thereto. Furthermore, the control unit 340 is configured to adjust the amount of thermal energy supplied by the heating device 310. In addition, the control unit 340 is configured to control the amount of air parcels removed by the exhaust device 320. Furthermore, the control unit 340 is configured to adjust the angle of the rotary kiln 300A with respect to the horizontal plane by adjusting the position of the base 308. The control unit 340 is configured to manage the rotational speed of the motor 330 of the rotary kiln 300A. The parameters of the rotary kiln 300A are adjustable, which may affect the size of the granular material formed. The processing time during which the industrial sand to be processed passes through the rotary kiln 300A can be adjusted, for example, from 10 to 60 minutes. The size (particle size, particle size) of the formed granular material may be, for example, 3 to 10 mm, 4 to 8 mm, or 5 to 6 mm.
[0031] The apparatus in Figures 3 and 4 comprises a separator 400 configured to separate industrial sand in order to remove granular material from industrial sand. The separator 400 is connected to a processing unit 300. More specifically, the separator 400 is connected to the outlet 304 of the processing unit 300. Industrial sand is separated from granular material based on particle size. In this separation, the particle size of the industrial sand is smaller than that of the granular material. The separator 400 may be a sieve, in other words, a sieve mesh sized to a mesh size smaller than that of the formed granular material. In other words, the parameters used for the regeneration of industrial sand are adjusted so that the size (particle size, particle size) of the formed granular material is larger than the mesh size of the sized sieve. The separator 400 may be a vibrating table equipped with a sieve mesh of a specific size. Industrial sand having a particle size smaller than a specific size passes through the separator 400 (see arrow 400-S in Figures 3 and 4). As a result, industrial sand with particle sizes exceeding a certain size and the formed granules do not pass through the separation device 400. Industrial sand and the formed granules that do not pass through the sieve of the separation device 400 are removed (see arrow 400-R in Figures 3 and 4) and, if applicable, further processed. In this further processing, the formed granules can be refined into a secondary product, and the industrial sand in this further processing may be returned, for example, to the pretreatment device 200 or the feed device 220 of the device. The mesh size of the sieve may be, for example, 1 to 5 mm, for example, 2 to 4 mm, or for example, about 2 to 3 mm.
[0032] The apparatus in Figure 3 includes a cooling kiln 500 (cooling furnace). The cooling kiln 500 includes a container 503 into which industrial sand is cooled. The cooling kiln 500 (more specifically, its container 503) has a first end 501A and a second end 501B. The first end 501A and the second end 501B are located at opposite ends. More specifically, the container 503 is a long, hollow cylindrical or tubular structure.
[0033] Furthermore, the cooling kiln 500 is equipped with an inlet 502 for receiving the separated industrial sand. The inlet 502 is connected to the separator 400. More specifically, the inlet 502 is connected to the sieve of the separator 400. The inlet 502 is located near the first end 501A. In addition, the cooling kiln 500 is equipped with an outlet 504 for supplying the industrial sand from the cooling kiln 500 to the classifier 600. The outlet 504 is connected to the classifier 600. The classifier 600 will be described in more detail later. The outlet 504 is located near the second end 501B. In other words, the inlet 502 and the outlet 504 are located at opposite ends from each other.
[0034] In addition, the cooling kiln 500 is equipped with a base 508. The cooling kiln 500 is located above the base 508. In Figure 3, the base 508 is shown in a very schematic manner. The base 508 sets the cooling kiln 500 to an angled position (inclined position) with respect to the horizontal plane. This angled position can affect the speed at which the industrial sand moves within the cooling kiln 500. The base 508 may be an adjustable base for changing the angled position of the cooling kiln 500. The adjustable base 508 may be operated, for example, by hydraulics.
[0035] In addition, the cooling kiln 500 is equipped with an air supply device 520 for supplying cooling air to the cooling kiln 500 to remove (release) latent heat energy present in the industrial sand. The cooling kiln 500 is configured to cool the industrial sand by supplying cooling air to the cooling kiln 500 (see arrow 500-C in Figure 3). The cooling air may be air at the temperature present in the space outside the cooling kiln 500. The air supply device 520 is located at the second end 501B of the cooling kiln 500. The supply of cooling air to the cooling kiln 500 lowers the temperature of the industrial sand, promoting the removal (release) of any binder remaining in the industrial sand.
[0036] In addition, the cooling kiln 500 is equipped with an exhaust system 530 for receiving cooling air and thermal energy removed (released) from the industrial sand. Through this exhaust system 530, the cooling air flowing through the cooling kiln 500 and any dust it may contain are removed. The exhaust system 530 is configured to remove air masses and any dust they may contain from the cooling kiln 500 (see arrow 500-R in Figure 3). The exhaust system 530 is located at the end opposite to the air supply system 520. In other words, the exhaust system 530 is located at the first end 501A of the cooling kiln 500. A dust filter may be connected to the exhaust system 530 to filter out dust and various binder residues. A thermal energy recovery system may be connected to the exhaust system 530 to recover thermal energy.
[0037] The cooling kiln 500 further comprises a plurality of milling balls 540. The milling balls 540 are for pulverizing the cooled industrial sand, thereby removing (releasing) any remaining binder residue from the industrial sand. The milling balls 540 may, in other words, be grinding balls. Pulverization may, in other words, be grinding. The cooling kiln 500 comprises a milling chamber 505A in which the milling balls 540 are arranged. The milling chamber 505A begins at a first end 501A of the cooling kiln 500 and extends from this first end 501A to a predetermined distance. The milling chamber 505A may be separated (isolated) from the rest of the cooling kiln 500, for example, by a wall baffle having an opening located inside the cooling kiln 500. The industrial sand is pulverized by the milling balls 540 (see arrow 540-M in Figure 3). The crushing of industrial sand by the crushing balls 540, along with the simultaneous cooling of the industrial sand, facilitates the removal (release) of any binder remaining in the industrial sand. The industrial sand in the cooling kiln 500 has already been crushed once in the rotary kiln 300A, and furthermore, the temperature of the industrial sand in the cooling kiln 500 is lower than that of the industrial sand in the rotary kiln 300A. Therefore, the crushing applied to the industrial sand differs from the crushing that occurs in the rotary kiln 300A, and thus facilitates the removal (release) of any binder remaining in the industrial sand.
[0038] The cooling kiln 500 further comprises a number of lifters 550 (in other words, shovels). The lifters 550 facilitate the movement of industrial sand within the cooling kiln 500. The lifters 550 are configured to transport industrial sand from a first end 501A to a second end 501B of the cooling kiln 500. The lifters 550 are located in the vane chamber 505B. The vane chamber 505B is positioned at a predetermined distance from the grinding chamber 505A and extends to a predetermined distance from the second end 501B of the cooling kiln 500. As the cooling kiln 500 rotates, the lifters 550 lift the industrial sand upward, causing the industrial sand to fall from the lifters 550 (vanes) to the bottom of the cooling kiln 500 at a predetermined height. This facilitates the release of thermal energy in the industrial sand into the cooling air flowing through the cooling kiln 500. Furthermore, as the industrial sand falls to the bottom of the cooling kiln 500, the particles of the industrial sand collide with each other, facilitating the removal (release) of binders from the industrial sand.
[0039] In addition, the cooling kiln 500 is equipped with a motor 560 for rotating the cooling kiln 500. The cooling kiln 500 is equipped with, for example, bearings, toothed carrier rings, and / or gears connected to the motor 560, as necessary means for rotating the cooling kiln 500.
[0040] The apparatus in Figure 3 comprises a classifier 600 (sorting device) configured to classify industrial sand (see arrow 600-F in Figure 3). The industrial sand to be classified in the classifier 600 is thermomechanically treated in a rotary kiln 300A and further mechanically treated (by crushing) in a cooling kiln 500. The classifier 600 comprises at least one sieve for classifying industrial sand based on particle size. Thus, the classifier 600 comprises a first sieve having a specific mesh size. Industrial sand passing through the first sieve forms a first quality class of industrial sand. Furthermore, industrial sand that has passed through the first sieve may be sent to a second sieve having a specific mesh size smaller than that of the first sieve. Industrial sand that has passed through the second sieve forms a second quality class of industrial sand. The classifier 600 may be equipped with n sieves (n=1, 2, 3, 4, 5...). Industrial sand that does not pass through the first sieve is removed for other uses (see arrow 600-R in Figure 3) or, for example, sent to a reprocessing or feeding device 220. The mesh size of the sieves may be, for example, 0.1 mm, 0.2 mm, 0.5 mm, and / or 1.0 mm.
[0041] The apparatus shown in Figure 3 includes a post-treatment device 700. The post-treatment by the post-treatment device 700 may be, for example, a storage process, a transport process, or an industrial process for industrial sand.
[0042] The apparatus in Figure 4, apparatus 300, is a fluidized bed reactor 300B. The fluidized bed reactor 300B has an inlet 302 and an outlet 304. The fluidized bed reactor 300B is configured to receive industrial sand and additives from a supply device 220. The fluidized bed reactor 300B includes a heating device 310 for heating the industrial sand and the additives added thereto. The heating device 310 may be, for example, a gas combustion device. The heating device 310 causes the heated industrial sand and alkali salt to move relative to each other, thereby causing at least some of the remaining impurities to adhere to the alkali salt and form granules. The fluidized bed reactor 300B includes an apparatus 320B, such as a cyclone. Through this apparatus 320B, the combustion gas is sent for further gas processing, and the industrial sand and the formed granules are sent to a separation device 400. The apparatus in Figure 4 may be further connected to a cooling kiln 500, a classifier 600, and / or a post-processing device 700, but these are not shown in Figure 4 for clarity.
[0043] According to the first embodiment, the following configuration was implemented to regenerate industrial sand. The industrial sand is phenolic resin sand, i.e., sand bound with organic resin. The industrial sand was regenerated using the feeder 220, rotary kiln 300A, and separation device 400 shown in Figure 3. The phenolic resin sand contains carbon and alkali metal as binders, and the alkali metal contains potassium. Additives are added to the industrial sand so that, for example, about 1 weight percent of kaolin is present. The industrial sand and the added additives are heated to 500-850°C, by which the additives react with impurities in the industrial sand, including at least alkali metals, to form at least partially molten alkali salts. Within this temperature range, the carbon in the phenolic resin sand burns away. The industrial sand and alkali salts are moved relative to each other, by which at least some of the remaining impurities in the industrial sand adhere to the alkali salts, forming granular material. At this time, the size (particle size) of the formed granular material is about 5-10 mm. The rotation speed of the 300A rotary kiln is approximately 5-20 rpm. The angular position of the 300A rotary kiln relative to the horizontal plane is approximately 0.5-5.0 degrees. This allows the industrial sand to be thermomechanically treated for approximately 10-60 minutes. If the ignition loss of the industrial sand after thermomechanical treatment is approximately 1.5 percent, the pH value of the industrial sand is approximately 10-11, and its electrical conductivity is approximately 1000 EC.
[0044] According to the second embodiment, the configuration corresponding to the first embodiment was implemented, but the amount of kaolin in the additive was about 1.5 weight percent relative to the industrial sand. When the ignition loss of the industrial sand after thermomechanical treatment is about 1.5 percent, the pH value of the industrial sand is about 9.0 to 9.5, and its electrical conductivity is about 400 EC.
[0045] According to the third embodiment, the configuration corresponding to the first embodiment was implemented, but the amount of kaolin in the additive was about 2.0 weight percent of the industrial sand. When the ignition loss of the industrial sand after thermomechanical treatment is about 1.5 percent, the pH value of the industrial sand is about 7.5 to 8.2, and its electrical conductivity is about 200 EC.
[0046] According to the fourth embodiment, the configuration corresponding to the first embodiment was implemented, but the industrial sand was green sand, containing bentonite and alkali metal as binders, the alkali metal being potassium. For clarification, it should be noted that the additive is added to the industrial sand so that approximately 1 weight percent of kaolin is present relative to the industrial sand. When the ignition loss of the industrial sand is approximately 1.5 percent, the pH value of the industrial sand is approximately 8.4, and its electrical conductivity is approximately 150 EC.
[0047] According to the fifth embodiment, the configuration corresponding to the fourth embodiment was implemented, but the amount of kaolin in the additive was about 1.5 weight percent relative to the industrial sand. When the ignition loss of the industrial sand after thermomechanical treatment is about 1.5 percent, the pH value of the industrial sand is about 8.0, and its electrical conductivity is about 100 EC.
[0048] According to the sixth embodiment, the configuration corresponding to the fourth embodiment was implemented, but the amount of kaolin in the additive was 2.5 weight percent relative to the industrial sand. When the ignition loss of the industrial sand after thermomechanical treatment is about 1.5 percent, the pH value of the industrial sand is about 7.4, and its electrical conductivity is about 30 EC.
[0049] Those skilled in the art will see that, with advances in technology, the basic concept of the present invention can be implemented in various ways. Therefore, the present invention and its embodiments are not limited to the examples described above and may be modified as appropriate within the scope of the claims.
Claims
1. A method for recycling industrial sand, Step (110) of adding an aluminum silicate-based additive to industrial sand, The process involves heating the industrial sand and the additive added to the industrial sand to cause the additive to react with impurities in the industrial sand, including at least alkali metals, to form at least partially molten alkali salts (120), Step (130) involves heating the industrial sand and the alkali salt to induce relative motion between them, thereby causing at least some of the impurities remaining in the industrial sand to adhere to the alkali salt, thereby forming granular material. Step (140) of separating the industrial sand in order to remove the granular material from the industrial sand, A method for providing this.
2. The step (130) of generating relative motion between the heated industrial sand and the alkali salt is performed in a rotary kiln (300A) to promote the formation of the granular material. The method according to claim 1.
3. The industrial sand and the additive added to the industrial sand are heated until the temperature reaches between 500°C and 850°C. The method according to claim 1 or claim 2.
4. When the industrial sand and the additive added to the industrial sand are heated, the additive reacts with impurities containing at least alkali metals in the binder of the industrial sand, thereby forming the at least partially molten alkali salt. When the heated industrial sand and the alkali salt are subjected to relative motion toward each other, at least some of the impurities remaining on the surface of the sand grains of the industrial sand adhere to the alkali salt, thereby forming the granular body. The method according to any one of claims 1 to 3.
5. The aforementioned industrial sand is green sand. The method according to any one of claims 1 to 4.
6. The aforementioned industrial sand contains an organic resin as a binder. The method according to any one of claims 1 to 4.
7. The formed granular material is separated from the industrial sand based on its particle size. The method according to any one of claims 1 to 6.
8. The steps include: (150) cooling the industrial sand to make it easier to remove any binder remaining in the industrial sand; In order to remove the binder remaining in the industrial sand from the industrial sand, the cooled industrial sand is crushed by a crushing ball (540) (160), The method further comprises the step (170) of sieving the industrial sand in order to classify it based on particle size, The method according to any one of claims 1 to 7.
9. The aforementioned additive contains an aluminum silicate mineral, which is one of andalusite, kaolin, kyanite, or sillimanite. The method according to any one of claims 1 to 8.
10. An apparatus for recycling industrial sand according to the method described in any one of claims 1 to 9, A supply device (220) for supplying industrial sand and additives to a processing device (300), The apparatus (300) heats the industrial sand and the additive added to the industrial sand to cause relative motion between the industrial sand and the additive added to the industrial sand, A separation device (400) configured to separate industrial sand in order to remove granular material from the industrial sand, A device equipped with the following features.
11. The aforementioned supply device (220) In order to receive the industrial sand and guide it to the processing device (300), a conveyor (222) connected to the processing device (300) is provided. The conveyor (222) is further equipped with an additive feeder (224) for adding additives to the industrial sand on the conveyor (222). The apparatus according to claim 10.
12. The conveyor (222) is a screw conveyor. The apparatus according to claim 11.
13. The processing apparatus (300) is a rotary kiln (300A), The aforementioned rotary kiln (300A) is The inlet (302) connected to the supply device (220), A heating device (310) configured to heat the industrial sand and the additive within the rotary kiln (300A), A motor (330) configured to rotate the rotary kiln (300A) in order to generate relative motion between the industrial sand and the additive added to the industrial sand, A control unit (340) for adjusting the parameters of the rotary kiln (300A) to define the particle size of the formed granular material, The separation device (400) is equipped with an outlet (304) connected to it. The apparatus according to any one of claims 10 to 12.
14. The separation device (400) is a sieve that separates the granular material from the industrial sand based on particle size. The apparatus according to any one of claims 10 to 13.
15. It is further equipped with a cooling kiln (500), The cooling kiln (500) is An inlet (502) connected to the separation device (400) for receiving the separated industrial sand, An air supply device (520) for supplying cooling air to the cooling kiln (500) in order to release the thermal energy in the industrial sand from the industrial sand, An exhaust device (530) for receiving the cooling air and the thermal energy released from the industrial sand, A crushing ball (540) for crushing the cooled industrial sand to remove the binder remaining in the industrial sand, The cooling kiln (500), the crushing balls (540), and the motor (560) for rotating the industrial sand, The system includes an outlet (504) for supplying the aforementioned industrial sand forward. The apparatus according to any one of claims 10 to 14.
16. The system includes a classification device (600) connected to the outlet (504) of the cooling kiln (500), The classification device (600) comprises at least one sieve for classifying the industrial sand based on particle size. The apparatus according to claim 15.