JPWO2006019047A1 - Method and apparatus for producing recycled foundry sand - Google Patents

Abstract

A method of producing high quality recycled foundry sand. In the method of the present invention, the foundry sand is blown to the upper part of the roasting chamber by the air flow while being roasted in the roasting chamber. Grains of foundry sand float above the roasting chamber and collide with each other to be ground. When the wind velocity of the air flow is 0.8 m/s or more, unnecessary components are effectively removed from the foundry sand, and high quality reclaimed foundry sand is obtained. In one embodiment, most of the foundry sand is levitated by the air flow to the upper part of the roasting chamber and a part of the foundry sand is roasted from the upper part of the roasting chamber through a circulation path outside the roasting chamber. Returned to the bottom of the baking chamber.

Description

  The present invention relates to a method and apparatus for producing recycled foundry sand.

  Generally, iron or aluminum casting parts are manufactured by sand casting using a sand mold made of sand. The foundry sand used in the mold is reused in the sand mold by recovering and regenerating it.

  An organic binder such as a resin having a caking property may be added to the foundry sand. By adding the organic binder, the shape of the mold formed from the foundry sand is preferably maintained.

  When an organic binder is used for the molding sand used for the core and green sand is used for the outer mold, it is difficult to recover only the molding sand constituting the core. Therefore, raw sand containing an inorganic component such as bentonite is mixed in the recovered foundry sand.

  Conventional foundry sand is regenerated by a step of roasting the foundry sand in a roasting furnace and a step of polishing the roasted foundry sand. In the roasting process, the foundry sand is heated to 600°C or higher. By heating, organic components such as resin adhering to the surface of the grains of the foundry sand are removed. In the polishing step, the organic and inorganic components remaining on the surface of the molding sand particles not removed in the roasting step are peeled off, and the shape of the molding sand particles is adjusted.

As an example of a conventional method for reclaiming foundry sand, when roasting the foundry sand in a roasting furnace, it has been proposed to continuously heat the air flow in the roasting furnace with the roasting heat of the foundry sand. (See Patent Document 1). According to this regeneration method, it is possible to suppress the temperature decrease of the air flow and accelerate the combustion of the organic component in the foundry sand.
JP-A-63-180340

  However, in the above-described conventional method for reclaiming foundry sand, the inorganic component (bentonite) mixed in the foundry sand is not removed by roasting, and the reclaimed foundry sand in which the inorganic component remains is recovered. The inorganic component remaining in the reclaimed molding sand is one of the factors that reduce the strength of the sand mold made of the reclaimed molding sand. Therefore, it is indispensable to separately perform the step of polishing the grains of the foundry sand after the roasting of the foundry sand, and the regeneration efficiency was low.

  It is an object of the present invention to provide a method and apparatus for producing efficient and high quality reclaimed foundry sand.

  One aspect of the present invention provides a method for producing reclaimed molding sand, which includes a step of preparing the molding sand and a step of regenerating the molding sand. The step of regenerating is a step of loading the molding sand into a furnace, and a step of blowing the molding sand to an upper part of the furnace with an airflow of 0.8 m/s or more while roasting the molding sand. Including and

  In one embodiment, the furnace is a circulating fluidized furnace.

  Another aspect of the present invention provides a method for producing a reclaimed molding sand, which includes a step of preparing the molding sand and a step of regenerating the molding sand. In the step of regenerating, the step of carrying the foundry sand into a furnace having a roasting chamber, and the process of roasting the foundry sand at 600° C. or more while air having a wind speed of 0.8 m/s or more in the roasting chamber Supplying a flow to blow most of the foundry sand above the roasting chamber, and transferring the blown foundry sand from the roasting chamber to a separator along with the air flow.

  In one embodiment, the step of regenerating further comprises a step of separating the blown molding sand from combustion gas generated in the roasting chamber, and the separated molding sand from the separating device to the roasting chamber. And a step of repeating the step of transferring, the step of blowing, the step of transferring to the separation device, the step of separating, and the step of transferring to the roasting chamber.

  The wind velocity of the air flow is preferably 1.5 m/s or more.

  In one embodiment, the foundry sand is used foundry sand used for casting, foundry sand having substandard quality, unwanted foundry sand, or foundry sand used in a sand mold that has failed to be molded.

  A further aspect of the present invention is a roasting device having a roasting chamber for roasting the foundry sand, and a large amount of the foundry sand during the roasting of the foundry sand with an airflow of a wind speed of 0.8 m/s or more. It is an apparatus for producing reclaimed molding sand, which comprises a blower for blowing up a portion above the roasting chamber.

  The manufacturing apparatus of one embodiment further includes a circulation path for returning a part of the blown molding sand from the upper part of the roasting chamber to the outside of the roasting chamber to the lower part of the roasting chamber. The circulation path, a communication pipe connected to the upper portion of the roasting chamber, a separation device connected to the communication pipe, for separating the blown molding sand from the combustion gas generated in the roasting chamber, A delivery pipe is provided which connects the separating device to the lower portion of the roasting chamber and returns the foundry sand separated by the separating device to the roasting chamber.

  In one embodiment, the roasting chamber has a lower portion and an upper portion that is wider than the lower portion.

1 is a schematic diagram of an apparatus for manufacturing recycled foundry sand according to a first embodiment of the present invention. The schematic diagram of the manufacturing device of recycled casting sand according to a 2nd embodiment of the present invention. The graph which shows the relationship between the particle size index of the reclaimed molding sand manufactured using the manufacturing apparatus of the reclaimed molding sand of FIGS. 1 and 2, and the wind speed of the air flow during roasting. 3 is a graph showing the relationship between the ignition loss and bending strength of the reclaimed molding sand manufactured using the reclaimed molding sand manufacturing apparatus of FIGS. 1 and 2, and the wind speed of the air flow during roasting. The graph which shows the change of the particle size index-wind velocity curve of recycled casting sand with the amount of sand. The graph which shows the change in ignition loss-wind velocity curve of the reclaimed foundry sand according to the amount of sand. The graph which shows the change of the bending strength-wind velocity curve of recycled casting sand with the amount of sands.

(First embodiment)
Hereinafter, a method for manufacturing reclaimed molding sand according to the first embodiment of the present invention will be described.

  Foundry sand is sand used for casting molds (sand molds). The foundry sand (used foundry sand) that composes the sand mold used for casting is recovered and regenerated. The used foundry sand contains almost no water and contains 0.1 to 10 mass% of organic components. The binder contained in the foundry sand is a phenolic organic binder, an inorganic binder such as water glass or bentonite, and a common binder such as clay, and is not particularly limited. The method for producing reclaimed molding sand of the first embodiment is suitable for reclaiming molding sand containing an organic binder. The method for producing the reclaimed molding sand of the first embodiment is a sand mold formed by a thermosetting molding method such as a shell molding method or a self-hardening molding method such as a cold box method in which the molding sand is self-cured at room temperature. It is suitable for reclaiming foundry sand used in. The method for producing reclaimed molding sand of the first embodiment can be used for reclaiming molding sand used in a sand mold formed by a method other than the cold box method and the shell molding method.

  Hereinafter, the molding sand used in the sand mold formed by the shell molding method will be described.

  In the shell mold method, molding sand in which additive components are mixed, so-called resin coated sand, is used to form a sand mold. Examples of the additive component are a binder such as phenol resin, a hardening accelerator such as hexamethylenetetramine, and a lubricant such as calcium stearate. The resin coated sand contains almost no water and contains 0.1 to 10 mass% of organic components.

  The formation of the mold by the shell mold method will be described. A resin coated sand is filled in a mold of 200 to 300°C. A mold is formed by curing the resin coated sand in the mold. Resin coated sand is mainly used as a core material. As the material for the outer mold, green sand containing a binder such as bentonite is used.

  As used herein, reclaiming foundry sand not only means reactivating the foundry sand used for casting into a reusable state for formation of the sand mold, but also reusing unused foundry sand in the sand mold. It also means preparing into a molding sand that can be used to form Examples of virgin foundry sand are resin-coated sands with substandard qualities, unwanted resin-coated sands, and resin-coated sands used in sand molds that have failed to make. An example of a resin coated sand having a nonstandard quality is a resin coated sand having poor strength. According to the regenerating process of the present invention, the binder used for forming the sand mold and the regenerated foundry sand from which the inorganic components mixed during the recovery of the used mold sand are removed can be obtained. This recycled foundry sand can be suitably reused to form a new sand mold.

  Below, the manufacturing method of the recycled casting sand of 1st Embodiment is demonstrated.

  The method for producing reclaimed molding sand of the first embodiment includes a regenerating step of supplying an air flow (blowing air) into the furnace to blow the molding sand to the upper part of the furnace while roasting the molding sand. The amount of the foundry sand carried into the furnace is not particularly limited, but is adjusted to such an amount that most of the foundry sand is not blown up to the upper part of the roasting chamber and the foundry sand is not deposited on the bottom of the roasting chamber. Is preferred. The process of reclaiming foundry sand can be performed in a batch system or a continuous system. Generally, it is efficient to carry out the regeneration process continuously.

  Foundry sand is roasted at 600°C or higher. A preferable roasting temperature is 700°C or higher, and a more preferable roasting temperature is 800°C or higher. When the roasting temperature (the temperature of foundry sand) is less than 600° C., incomplete combustion of unnecessary components such as a binder adhering to the surface of the grains of the foundry sand occurs, and the unnecessary components are not sufficiently burned. In this case, low quality blackened recycled sand may be obtained. When the temperature of the foundry sand cannot be directly measured, the ambient temperature in the furnace may be regarded as the temperature of the foundry sand.

  The wind speed is determined so that most of the grains of the foundry sand float above the roasting chamber so that the foundry sand does not accumulate at the bottom of the roasting chamber. In the first embodiment, the foundry sand is blown up in the furnace by an air flow having a wind speed of 0.8 m/s or more. The particles of the foundry sand blown up are polished by violently colliding with each other. As a result, unnecessary components such as a binder adhering to the surface of the molding sand particles are peeled off, and the shape and size of the molding sand particles are adjusted. The wind velocity of the air flow is preferably 1 m/s or more, more preferably 1.5 m/s or more. When the wind velocity of the airflow is less than 0.8 m/s, the frequency of collision between the particles of the foundry sand is low, and the surface of the particles of the foundry sand may be insufficiently polished. The higher the wind speed of the air flow, the more effective the polishing effect of the foundry sand. Although there is no upper limit to the wind speed of the air flow, an air flow with a wind speed exceeding 15 m/s is not practical due to the structure of the foundry sand recycling apparatus.

  Hereinafter, with reference to FIG. 1, an apparatus for reclaiming foundry sand, that is, an apparatus for producing reclaimed molding sand according to the first embodiment of the present invention will be described.

  The regenerating apparatus includes a circulating fluidized furnace 11 that roasts foundry sand while circulating it.

  The circulating fluidized furnace 11 includes, for example, a roasting device 12 having a cylindrical roasting chamber, a separating device 13 (for example, a cyclone structure), a delivery pipe 14, and a blower pipe connected to the bottom of the roasting device 12. And a blower 16. The blower 16 supplies an air flow to the roasting chamber through a blower pipe. A side of the roasting device 12 is provided with a carry-in port 15 for carrying the foundry sand into the roasting chamber. The foundry sand is roasted in a roasting chamber by a burner (not shown). The communication pipe 17 connects the upper part of the roasting chamber and the separating device 13. The separation device 13 separates the combustion gas generated by roasting the foundry sand from the foundry sand. The delivery pipe 14 connects the lower part of the separation device 13 and the lower part of the roasting chamber. The grains of the foundry sand separated from the combustion gas by the separator 13 are returned to the roasting chamber through the delivery pipe 14. The communication pipe 17, the separation device 13, and the delivery pipe 14 function as a circulation path provided outside the roasting chamber.

  When the foundry sand is reclaimed using the circulating fluidized furnace 11, first, the foundry sand used for the mold is recovered. An organic binder is used as a binder for the foundry sand used for the core, and when the green sand is used as the outer mold, the foundry sand that constitutes the core even if only the core is to be recovered, Raw sand containing inorganic components (bentonite) that cannot be removed by roasting is mixed.

  After the foundry sand is collected, the foundry sand is pre-baked in a baking furnace (not shown) at 100° C. or higher. Next, a predetermined amount of foundry sand is carried into the roasting device 12 through the carry-in port 15. The foundry sand may be carried into the roasting device 12 continuously or intermittently. In one embodiment, the amount of foundry sand input is 10 tons per hour. The foundry sand carried into the roasting device 12 is blown up by the air flow supplied from the blower 16 while being roasted in the roasting device 12 by the heat of the burner.

  Unnecessary components such as a binder adhering to foundry sand are burned by roasting to generate combustion gas. A part of the organic components that cannot be removed among the unnecessary components such as the binder may remain on the surface of the grains of the foundry sand. When green sand is mixed in the recovered foundry sand, bentonite contained in the raw sand remains without being removed by roasting.

  In the first embodiment, the grains of the foundry sand float to the upper part of the roasting chamber by an air flow of a predetermined wind speed (0.8 m/s or more), collide violently with each other, or the wall surface of the roasting device 12. It collides with and is polished. Due to this collision, unnecessary components such as bentonite remaining in the foundry sand are peeled off from the surface of the grains of the foundry sand.

  The wind velocity of the air flow can be directly measured by installing a wind velocity sensor in the roasting chamber, but can also be calculated by the following formula.

Wind velocity of airflow = V1 x A1/B
V1 is the velocity of the air flow measured at the measurement position A of the blower tube of the blower 16. A1 is a cross-sectional area at the measurement position A of the blower pipe of the blower 16. B is the area of the bottom of the roasting chamber.

  When the molding sand is blown up as described above, the organic components that cannot be completely removed by roasting are also peeled off from the surface of the grains of the molding sand. As a result of the particles of the foundry sand rubbing against each other, the particles of the foundry sand are shaved and the particle size becomes smaller. In this way, a high quality reclaimed foundry sand with improved shape is obtained.

  A part of the air flow in which the molding sand is blown up by the roasting device 12 is supplied again from the roasting device 12 into the roasting device 12 via the separating device 13 and the delivery pipe 14.

  After a part of the foundry sand is blown up in the roasting device 12, it is sent to the separating device 13 through the communication pipe 17 together with the combustion gas. The separating device 13 separates the foundry sand and the combustion gas. The separated combustion gas is released to the atmosphere through a processing device (not shown), and the separated foundry sand is sent to the roasting device 12 through a delivery pipe 14.

  In the first embodiment, the grains of the foundry sand are not only polished in the roasting chamber, but are also polished by colliding with each other when moving the communication pipe 17, the separating device 13 and the delivery pipe 14. . Further, the grains of the foundry sand move while colliding with the inner surfaces of the communication pipe 17, the separating device 13 and the delivery pipe 14. Therefore, the circulating fluidized furnace 11 can efficiently produce the reclaimed molding sand by continuously polishing the molding sand.

  Grains of the foundry sand carried into the roasting device 12 flow into the roasting device 12 while continuously colliding with each other and being polished by the air flow circulating inside the circulating fluidized furnace 11. The foundry sand is regenerated by circulating it in the circulating fluidized furnace 11 at least once. According to the first embodiment, it is possible to obtain a high-quality regenerated foundry sand that is preferably subjected to a baking treatment along with roasting of unnecessary components such as a binder.

  According to the first embodiment, the following advantages can be obtained.

  The regenerating step of the first embodiment includes blowing the foundry sand by an air flow having a wind speed of 0.8 m/s or more while roasting the foundry sand carried into the toasting device 12. The grains of the foundry sand blown up by the air flow are sufficiently polished by the collision between the grains and the collision with the inner wall surface of the roasting device 12. As a result, unnecessary components such as a binder adhering to the surface of the molding sand particles can be removed, and the shape of the molding sand particles can be improved.

  According to the method for producing recycled foundry sand of the first embodiment, the surface of the grains of the foundry sand is polished while the foundry sand is roasted. It is not necessary to separately perform the step of polishing the foundry sand after roasting the foundry sand as in the conventional regenerating method. That is, in the first embodiment, the roasting step and the polishing step are performed at the same time. Therefore, the working process is simplified and the working time is shortened.

  The foundry sand is regenerated using the circulating fluidized furnace 11 in which the air flow circulates inside the roasting chamber. Due to the air flow, the grains of the foundry sand are circulated at least once in the circulating fluidized furnace 11 while being polished together. Therefore, the circulating fluidized furnace 11 can efficiently polish the foundry sand.

  Foundry sand is roasted at a high temperature of 600° C. or higher. Therefore, the organic components such as the binder adhering to the surface of the grains of the foundry sand are almost completely burned and removed from the foundry sand.

(Second embodiment)
Hereinafter, a method and an apparatus for manufacturing recycled foundry sand according to the second embodiment of the present invention will be described.

  First, with reference to FIG. 2, an apparatus for reclaiming foundry sand, that is, an apparatus for producing reclaimed foundry sand according to the second embodiment will be described. The regeneration device includes a roasting furnace 21. The roasting furnace 21 is connected to, for example, a roasting device 22 having a cylindrical roasting chamber and a lower part of the roasting device 22 that supplies an air flow of a wind speed of 0.8 m/s or more to the roasting chamber. And a blower 16 including a blower tube. The regenerator does not include the separator 13 (see FIG. 1). At a side portion of the roasting device 22, a carry-in port 15 for carrying the foundry sand into the roasting chamber is formed. A burner (not shown) for roasting the foundry sand is arranged on the side of the roasting device 22. In the roasting furnace 21 of the second embodiment, the grains of the foundry sand are blown up to the upper part of the roasting chamber and then fall to the bottom of the roasting chamber without being sent to the separating device 13 (see FIG. 1 ). The roasting chamber has a relatively wide top and a relatively narrow bottom. The roasting chamber having a relatively wide upper part has an effect of facilitating the floating and diffusion of the foundry sand and enhancing the collision efficiency of the particles of the foundry sand.

  An example of reclaiming foundry sand using the roasting furnace 21 will be described.

  The foundry sand is carried into the roasting chamber from the carry-in port 15 at a rate of 10 tons per hour. The casting sand is roasted by the heat of the burner while supplying an air flow having a wind speed of 0.8 m/s or more from the blower 16 to the roasting chamber. Most of the foundry sand grains are blown up by the air flow to the upper part of the roasting chamber. The wind velocity of the air flow is measured or calculated as described in the first embodiment.

  The grains of foundry sand violently collide with each other in the upper part of the roasting chamber and also with the inner surface of the roasting chamber. Unnecessary components such as a binder remaining in the foundry sand are peeled off and removed from the foundry sand. The mutual collision of the foundry sand particles results in a high quality reclaimed foundry sand with an improved shape, with the shape and size of the foundry sand particles being adjusted.

Example 1
(Production of recycled casting sand)
Foundry sand was recovered from the sand mold used for casting. 1 t of molding sand was carried into each of the circulating fluidized furnace 11 and the roasting furnace 21 having a processing capacity of 2 t/h. In each of the circulating fluidized furnace 11 and the roasting furnace 21, regenerated foundry sand was manufactured by roasting the foundry sand at 700° C. for 1 hour while floating the foundry sand.

(Physical properties of recycled casting sand)
The relationship between the wind velocity of the air flow during roasting and the physical properties of the recycled foundry sand was investigated. The results are shown in FIGS. 3 and 4.

(Particle size index)
The grain size index is an index of the grain size of the foundry sand. The particle size index was calculated according to the AFS system number standard defined in JACT test method S-1 (particle size test method for foundry sand). The higher the particle size index, the better the polishing and the higher the quality of the reclaimed foundry sand.

(Loss on ignition)
Ignition loss is an index showing the degree of mass change of foundry sand that occurs when pyrolysis and combustion occur. The smaller the loss on ignition, the less foreign matter adhered to the reclaimed molding sand. The ignition loss was measured according to JACT test method S-2 (Test method for ignition loss of foundry sand). Specifically, the free water of the foundry sand is removed according to JIS Z 2601. Place 10 g (W ₁ ) of accurately weighed foundry sand in a crucible. This crucible is left for 15 minutes in an electric furnace preheated to 1000°C. The crucible is subsequently ignited for 45 minutes. Let the crucible taken out of the electric furnace cool to room temperature in a desiccator. Then, the mass (W ₂ ) of the foundry sand is measured. Loss on ignition was calculated according to the following formula.

Loss on ignition (%)=(W ₁ -W ₂ )/W ₁ ×100
(Bending strength)
7 kg of reclaimed molding sand preheated to 150° C. and 175 g of novolac type phenol resin (manufactured by Asahi Organic Materials Co., Ltd., trade name SP610) were put into a whirl mixer (manufactured by Enshu Iron Works Co., Ltd.) and kneaded for 40 seconds. An aqueous solution containing 26.3 g of hexamethylenetetramine and 105 g of water was added to the kneaded product in the whirl mixer. Kneading was continued while blowing air with a blower until the mass of the kneaded material collapsed. 7 g of calcium stearate was added into the whirl mixer and kneaded for 5 seconds to obtain a resin coated sand. A test piece defined by JIS K 6910 was produced from this resin coated sand. The bending strength of the test piece was measured according to JACT test method SM-1 (bending strength test method). The higher the bending strength of the test piece, the higher the bending strength of the mold.

  As shown in FIG. 3, in the case of producing the reclaimed molding sand in the roasting furnace 21 of FIG. 2, when the wind velocity of the air flow was 0.8 m/s or more, the particle size index was sharply improved. That is, it was found that by roasting the foundry sand while levitating the foundry sand with an air flow of 0.8 m/s or more, the grains of the foundry sand were sufficiently polished to obtain a high quality reclaimed foundry sand. .. It has been found that when the wind speed is in the range of 1.5 to 3 m/s, the use of the circulating fluidized furnace 11 rather than the roasting furnace 21 makes it possible to obtain reclaimed molding sand having a preferred particle size index. It is presumed that this is because the collision force between the grains of the foundry sand in the circulating fluidized furnace 11 is higher than that in the roasting furnace 21, so that unnecessary components such as a binder are preferably removed. ..

  As is clear from FIG. 4, when the reclaimed molding sand was manufactured in the roasting furnace 21 of FIG. 2, the loss on ignition decreased sharply when the wind speed was 0.8 m/s or higher. That is, by roasting the foundry sand while floating it with an airflow of 0.8 m/s or more, a high quality reclaimed foundry sand with almost no unnecessary components such as a binder adhering to its surface is obtained. I found out that It was found that when the wind speed was within the range of 1.5 to 3 m/s, the use of the circulating fluidized furnace 11 rather than the roasting furnace 21 yielded regenerated foundry sand with a smaller ignition source. It is presumed that this is because the collision force between the grains of the foundry sand in the circulating fluidized furnace 11 is higher than that in the roasting furnace 21, so that unnecessary components such as a binder are preferably removed. ..

  The bending strength was drastically improved by roasting the foundry sand while floating the foundry sand with an airflow of 0.8 m/s or more. That is, the resin coated sand produced from the regenerated foundry sand roasted while floating the foundry sand with the air flow of 0.8 m/s or more is suitable for producing a mold having good strength. .. It was found that when the wind speed is in the range of 1.5 to 3 m/s, the use of the circulating fluidized furnace 11 rather than the roasting furnace 21 provides reclaimed molding sand capable of producing a mold having high bending strength. .. It is presumed that this is because the collision force between the grains of the foundry sand in the circulating fluidized furnace 11 is higher than that in the roasting furnace 21, so that reclaimed foundry sand having a small grain size can be obtained.

Example 2
A roasting furnace 21 having a roasting chamber with a volume of 40 m ³ was prepared. The amount of foundry sand carried into the roasting chamber was changed (0.5t, 1t, 1.5t) to regenerate the foundry sand. The physical properties of the reclaimed foundry sand were measured in the same manner as in Example 1.

  Regarding the physical properties of the reclaimed molding sand obtained when 1 t of the molding sand was carried in, the measurement values of Example 1 were cited. The results are shown in FIGS.

  As shown in FIG. 6, even when the amount of foundry sand carried into the roasting chamber was changed, the loss on ignition decreased sharply when an air flow of 0.8 m/s or higher was supplied. Reclaimed foundry sand was obtained.

  As shown in FIG. 5 and FIG. 7, even when the amount of foundry sand carried into the roasting chamber is changed, if the airflow with a wind speed of 0.8 m/s or more is supplied, the grain size index and the bending strength are increased. A reclaimed foundry sand having a sharply improved value was obtained.

Example 3
The casting sand was roasted at 900° C. using the circulating fluidized furnace 11 of FIG. 1 and the roasting furnace 21 of FIG. 2. The physical properties of the reclaimed foundry sand were measured. The effect of the roasting temperature of the foundry sand on the physical properties of the reclaimed foundry sand was evaluated. The results are shown in Table 1 below. The sand temperature in the furnace in Table 1 is the temperature of the foundry sand in the circulating fluidized furnace 11 and the roasting furnace 21. The amount of sand in the furnace is the mass of foundry sand carried into the circulating fluidized furnace 11 and the roasting furnace 21.

比較例１では、０．８ｍ／ｓ未満の風速の空気流を供給した。鋳物砂を９００℃で焙焼した場合、０．８ｍ／ｓを大幅に超える風速（６ｍ／ｓ）を使用した試験例１，２では、良好な物性を有する再生鋳物砂が得られた。

In Comparative Example 1, an air flow having a wind speed of less than 0.8 m/s was supplied. When the foundry sand was roasted at 900° C., in Test Examples 1 and 2 using a wind speed (6 m/s) significantly exceeding 0.8 m/s, regenerated foundry sand having good physical properties was obtained.

  In Test Example 1 in which the furnace sand temperature was higher than that in Test Example 3, a slight improvement in physical properties was observed. The reason for this is presumed to be that by roasting the foundry sand at 900° C., unnecessary components such as a binder, which could not be removed at 700° C., could be removed.

  Each embodiment may be modified as follows.

  The blower pipe of the blower 16 is not limited to the bottom of the roasting chamber, and may be connected to the upper part or the central part of the roasting devices 12 and 22. In this case, the grains of the foundry sand collide with each other in the roasting chamber more frequently and with a higher collision force by the air flows supplied from various directions. Therefore, the polishing effect is improved.

  The embodiments and examples detailed above are for explaining the gist of the present invention, and the gist of the present invention is defined in the claims and should be construed as limited to the description of the embodiments and examples. is not.

[0010]
And 175 g of trade name SP610) were placed in a whirl mixer (manufactured by Enshu Iron Works Co., Ltd.) and kneaded for 40 seconds. An aqueous solution containing 26.3 g of hexamethylenetetramine and 105 g of water was added to the kneaded product in the whirl mixer. Kneading was continued while blowing air with a blower until the mass of the kneaded material collapsed. 7 g of calcium stearate was added into the whirl mixer and kneaded for 5 seconds to obtain a resin coated sand. A test piece defined by JIS K 6910 was produced from this resin coated sand. The bending strength of the test piece was measured according to JACT test method SM-1 (bending strength test method). The higher the bending strength of the test piece, the higher the bending strength of the mold.
[0058] As shown in Fig. 3, in the case of producing the reclaimed molding sand in the roasting furnace 21 of Fig. 2, when the wind velocity of the air flow was 0.8 m/s or more, the particle size index was sharply improved. That is, it was found that by roasting the foundry sand while levitating the foundry sand with an air flow of 0.8 m/s or more, the grains of the foundry sand were sufficiently polished to obtain a high quality reclaimed foundry sand. .. It has been found that when the wind speed is in the range of 1.5 to 3 m/s, the use of the circulating fluidized furnace 11 rather than the roasting furnace 21 makes it possible to obtain reclaimed molding sand having a preferred particle size index. It is presumed that this is because the collision force between the grains of the foundry sand in the circulating fluidized furnace 11 is higher than that in the roasting furnace 21, so that unnecessary components such as a binder are preferably removed. ..
As is clear from FIG. 4, in the case of producing the reclaimed molding sand in the roasting furnace 21 of FIG. 2, the loss on ignition decreased sharply when the wind speed was 0.8 m/s or higher. That is, by roasting the foundry sand while floating it with an airflow of 0.8 m/s or more, a high quality reclaimed foundry sand with almost no unnecessary components such as a binder adhering to its surface is obtained. I found out that It was found that, when the wind speed is within the range of 1.5 to 3 m/s, the use of the circulating fluidized furnace 11 rather than the roasting furnace 21 yields a reclaimed molding sand with a smaller ignition loss. It is presumed that this is because the collision force between the grains of the foundry sand in the circulating fluidized furnace 11 is higher than that in the roasting furnace 21, so that unnecessary components such as a binder are preferably removed. ..
[0060] The bending strength was drastically improved by roasting the molding sand while levitating the molding sand with an air flow of 0.8 m/s or more. That is, the resin coated sand produced from the regenerated foundry sand roasted while floating the foundry sand with the airflow of 0.8 m/s or more is suitable for producing a mold having good strength. .. When the wind speed is within the range of 1.5 to 3 m/s,

比較例１では、０．８ｍ／ｓ未満の風速の空気流を供給した。鋳物砂を９００℃で焙焼した場合、０．８ｍ／ｓを大幅に超える風速（６ｍ／ｓ）を使用した試験例１，２では、良好な物性を有する再生鋳物砂が得られた。
［００６７］ 試験例３より高い炉内砂温の試験例１では、物性の僅かな向上がみられた。この理由は、鋳物砂を９００℃で焙焼することにより、７００℃では除去することができなかった粘結剤等の不要成分を除去することができたものと推測される。
［００６８］ 各実施形態は、次のように変更してもよい。
［００６９］ ブロア１６の送風管は、焙焼室の底に限らず、焙焼装置１２，２２の上部又は中央部に接続してもよい。この場合、鋳物砂の粒は、焙焼室内において、様々な方向から供給された空気流によって、より高頻度でより高い衝突力で互いに衝突する。よって、研磨効果が向上する。
［００７０］ 以上詳述した実施形態及び実施例は本発明の趣旨を説明するためのものであり、本発明の趣旨は請求の範囲に規定されており、実施形態及び実施例の記載に限定解釈されるべきではない。[0012]

In Comparative Example 1, an air flow having a wind speed of less than 0.8 m/s was supplied. When the foundry sand was roasted at 900° C., in Test Examples 1 and 2 using a wind speed (6 m/s) significantly exceeding 0.8 m/s, regenerated foundry sand having good physical properties was obtained.
[0067] In Test Example 1 in which the in-furnace sand temperature was higher than in Test Example 3, a slight improvement in physical properties was observed. The reason for this is presumed to be that by roasting the foundry sand at 900° C., unnecessary components such as a binder, which could not be removed at 700° C., could be removed.
[0068] Each embodiment may be modified as follows.
[0069] The blower pipe of the blower 16 is not limited to the bottom of the roasting chamber, and may be connected to the upper portion or the central portion of the roasting devices 12 and 22. In this case, the grains of the foundry sand collide with each other in the roasting chamber more frequently and with a higher collision force by the air flows supplied from various directions. Therefore, the polishing effect is improved.
[0070] The embodiments and examples described in detail above are for explaining the gist of the present invention, and the gist of the present invention is defined in the claims and limited interpretation to the description of the embodiments and examples. Should not be done.

Claims (9)

A method of manufacturing recycled foundry sand,
The process of preparing foundry sand,
And a step of regenerating the molding sand, the regenerating step,
Carrying the molding sand into the furnace,
A method for producing a reclaimed molding sand, which comprises a step of blowing the molding sand to an upper part of the furnace with an airflow of 0.8 m/s or more while roasting the molding sand. The method for producing reclaimed molding sand according to claim 1, wherein the furnace is a circulating fluidized furnace. A method of manufacturing recycled foundry sand,
The process of preparing foundry sand,
And a step of regenerating the molding sand, the regenerating step,
Carrying the casting sand into a furnace having a roasting chamber,
While roasting the foundry sand at 600° C. or higher, supplying an air flow of 0.8 m/s or more to the roasting chamber to blow up most of the foundry sand to the upper part of the roasting chamber. When,
And a step of transferring the blown foundry sand together with the airflow from the roasting chamber to a separator. The step of regenerating further includes
Separating the blown molding sand from the combustion gas generated in the roasting chamber,
Including a step of transferring the separated molding sand from the separation device to the roasting chamber,
The method for producing reclaimed molding sand according to claim 3, further comprising: a step of repeating the step of blowing up, a step of transferring to the separating device, a step of separating, and a step of transferring to the roasting chamber. .. The method for producing reclaimed molding sand according to claim 1 or 3, wherein the wind velocity of the air flow is 1.5 m/s or more. The casting sand is used casting sand used for casting, casting sand having a nonstandard quality, unnecessary casting sand, or casting sand used in a sand mold that has failed to be molded. A method for producing the reclaimed foundry sand described. A manufacturing device for recycled foundry sand,
A roasting device having a roasting chamber for roasting the foundry sand;
A blower for blowing up most of the molding sand to the upper part of the roasting chamber with an airflow of 0.8 m/s or more during roasting of the molding sand. apparatus. A part of the casting sand blown to the upper part of the roasting chamber is further provided with a circulation path for returning from the upper part of the roasting chamber to the lower part of the roasting chamber through the outside of the roasting chamber,
The circulation path, a communication pipe connected to the upper portion of the roasting chamber,
A separation device which is connected to the communication pipe and separates the blown up molding sand from the combustion gas generated in the roasting chamber,
8. The apparatus for producing reclaimed molding sand according to claim 7, further comprising a delivery pipe that connects the separating device to a lower portion of the roasting chamber and returns the molding sand separated by the separating device to the roasting chamber. 8. The apparatus for producing recycled foundry sand according to claim 7, wherein the roasting chamber has a lower portion and an upper portion wider than the lower portion.

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