Sand shape separation method, sand shape separation device, and reclaimed sand production method

Abstract

Properly separate the mixed sand. [Solution] A shape separator equipped with an inclined belt conveyor, a sand supply unit, a side recovery unit that recovers sand on the side of the belt, and a downstream recovery unit that recovers sand at the downstream end of the belt in the moving direction of the belt is used to separate spherical sand from irregularly shaped sand. The spherical sand and irregularly shaped sand are separated by the steps of: rotating the belt at a predetermined inclination angle and a predetermined moving speed, supplying sand from the sand supply unit, and obtaining the area of ​​the sand occupying an area on the belt when the area is viewed opposite each other as the sand area occupancy rate; changing the amount of sand supplied so that the sand area occupancy rate falls within a predetermined range; recovering sand at the side recovery unit and the downstream recovery unit, determining the average circularity and recovery rate of the sand recovered at the side recovery unit, and if the standard average circularity or the standard recovery rate is not satisfied, repeating the process with a different inclination angle and / or supply amount; and operating the shape separator under conditions where both are satisfied to perform shape separation.

Description

[Technical field]

[0001] The present invention relates to a sand shape separation method, a sand shape separation device, and a method for producing reclaimed sand, which are capable of obtaining sand containing spherical sand at a ratio equal to or greater than a standard from a sand mixture containing spherical sand and irregularly shaped sand other than spherical sand. [Background technology]

[0002] In the foundry industry, one of the molding methods for making casting molds is the shell molding method, which is a method in which resin-coated sand (also called Resin Coated Sand or RCS) is filled into a preheated metal mold and hardened to make a casting mold.

[0003] RCS contains sand as aggregate and a binder. The inventors have developed a spherical aggregate mainly made of synthetic mullite to achieve a quality that exceeds that of natural silica sand as an aggregate suitable for this RCS (see, for example, Patent Document 1). This aggregate is so-called artificial sand. The artificial sand described in Patent Document 1 is spherical and has a small surface area per unit volume, so it is less likely to break or crack due to contact between sand particles for casting, and can maintain its initial properties. Therefore, it has the property of being easy to regenerate. In addition, although not for foundry sand, a method for separating hydraulic composition particles such as cement or cement clinker and aggregate particles such as sand or gravel mixed therewith based on their shape is known, which uses an inclined belt conveyor to perform shape separation, i.e., a shape separation method using an inclined belt conveyor (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-251434 A [Patent Document 2] Japanese Patent Application Publication No. 07-000920 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, various types of artificial sand have been developed in the foundry industry other than the artificial sand described in Patent Document 1. Businesses that use casting molds mix various types of sand, including artificial sand, depending on the purpose. As a result, the waste casting sand after use contains multiple types of sand with different shapes. If a specific type of sand could be separated from this sand, it could be possible to reuse the artificial sand. One method of shape separation is known to use an inclined belt conveyor. However, as mentioned above, the types and ratios of sand contained in waste foundry sand vary, and it is difficult to predict their characteristics. On the other hand, shape separation devices using an inclined belt conveyor have many parameters related to separation performance, such as the inclination angle of the belt conveyor, the moving speed of the belt, and the supply amount of objects to be shape separated. It is not easy to set these parameters appropriately for objects whose characteristics cannot be predicted. The present invention has been made under such circumstances, and provides a method for determining operating parameters for an inclined belt conveyor type shape separation device so that mixed sand containing sand of various shapes, such as waste foundry sand, can be appropriately separated, thereby enabling shape separation to be performed. [Means for solving the problem]

[0006] The inventors analyzed the preferable behavior of sand on the belt when using an inclined belt conveyor type shape separator to separate sand having a standard average circularity or more, and found that the recovery rate of sand having a standard average circularity or more that falls to the side of the belt and the sand area occupancy rate on the belt are indices related to the realization of the preferable behavior. The inventors discovered that by obtaining the recovery rate and the sand area occupancy rate, it is possible to appropriately set the operating parameters of the shape separator, and arrived at the present invention. By determining the operating parameters using the recovery rate and the sand area occupancy rate of sand having a standard average circularity or more, it is possible to efficiently separate spherical sand having a standard average circularity or more from irregularly shaped sand other than spherical sand.

[0007] The present invention relates to A method for separating spherical sand and irregularly shaped sand using a shape separation device including an inclined belt conveyor section inclined in the width direction of a belt, a sand supply section which supplies sand to the inclined belt conveyor section, a side collection section which collects sand falling to the side in the width direction of the belt, and a downstream collection section which collects sand falling at the downstream end of the belt in the moving direction, the method comprising the steps of: rotating the belt at a predetermined inclination angle and a predetermined moving speed, supplying sand from the sand supply section, and obtaining the area of ​​sand occupying the area on the belt while viewing the areas opposite each other as a sand area occupancy rate; changing the amount of sand supplied per hour so that the sand area occupancy rate falls within a predetermined range; collecting sand at the side collection section and the downstream collection section while the sand area occupancy rate falls within the predetermined range, and determining the average circularity of the sand collected at the side collection section and the average circularity of the sand bags supplied from the sand supply section. and a recovery rate representing the proportion of sand recovered in the side recovery section, and a confirmation step of confirming whether or not a criterion that the average circularity is equal to or greater than a reference average circularity and the recovery rate is equal to or greater than a reference recovery rate is satisfied; a reacquisition step of, if the criterion is not satisfied, rotating the belt with a setting in which at least one of the inclination angle, the moving speed, and the supply amount is changed, reacquiring the sand area occupancy rate and confirming that it is within the predetermined range; if the sand area occupancy rate acquired in the reacquisition step is within the predetermined range, executing the confirmation step with the setting at the time when the reacquisition step was executed, and if the criterion is not satisfied, repeating the process from the reacquisition step; and a step of operating the shape separation device with the setting in which the criterion is satisfied to perform shape separation.

[0008] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: A method for producing recycled spherical sand and recycled irregularly shaped sand by separating spherical sand and irregularly shaped sand using a shape separation device including an inclined belt conveyor section inclined in the width direction of a belt, a sand supply section which supplies sand to the inclined belt conveyor section, a side collection section which collects sand falling to the side in the width direction of the belt, and a downstream collection section which collects sand falling at the downstream end of the belt in the moving direction, the method comprising the steps of: rotating the belt at a predetermined inclination angle and a predetermined moving speed, supplying sand from the sand supply section, and obtaining the area of ​​sand occupying the area on the belt in a state in which the areas are viewed opposite each other as a sand area occupancy rate; changing the amount of sand supplied per hour so that the sand area occupancy rate falls within a predetermined range; collecting sand at the side collection section and the downstream collection section in a state in which the sand area occupancy rate falls within the predetermined range, and obtaining the average circularity of the sand collected at the side collection section and the average circularity of the sand supplied from the sand supply section. and determining a recovery rate representing the proportion of sand recovered in the side recovery section out of the total circularity, and verifying whether or not a criterion is met that the average circularity is equal to or greater than a reference average circularity and the recovery rate is equal to or greater than a reference recovery rate; if the criterion is not met, rotating the belt with a setting that changes at least one of the inclination angle, the moving speed, and the supply amount, and reacquiring the sand area occupancy rate to verify that it is within the predetermined range; if the sand area occupancy rate acquired in the reacquisition step is within the predetermined range, executing the confirmation step with the setting at the time when the reacquisition step was executed, and if the criterion is not met, repeating the process from the reacquisition step; and operating the shape separation device with the setting that satisfies the criterion to perform shape separation.

[0009] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: The present invention provides a sand shape separation device comprising an inclined belt conveyor section inclined in the width direction of the belt, an inclination angle adjustment mechanism for adjusting the angle of the inclination, a belt drive section for moving the belt, a speed adjustment section for adjusting the moving speed of the belt, a sand supply section for supplying sand containing a mixture of spherical sand and irregularly shaped sand to the inclined belt conveyor section, a supply amount adjustment section for adjusting the amount of sand supplied per hour by the sand supply section, a side recovery section for recovering sand that falls to the side in the width direction of the belt, a downstream recovery section for recovering sand that falls at the downstream end in the moving direction of the belt, and a device for calculating the area occupied by sand in a region on the belt based on an image captured by a device that faces the region and images the sand in the region. Effect of the Invention

[0010] According to the present invention, the operating parameters of the inclined belt conveyor type shape separator can be determined, and mixed sand containing sand of various shapes can be appropriately separated by shape. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an example of the configuration of a shape separation device used in a shape separation method according to the present invention. [Diagram 2] FIG. 2 is a perspective view showing the behavior of sand when shape separation of mixed sand is performed using the shape separation device shown in FIG. [Diagram 3] FIG. 3 is a perspective view showing a shape separation device having the same configuration as in FIGS. 1 and 2 except that the number of sections of the spherical sand recovery tank is one. [Figure 4] 11 is a graph showing the relationship between the sand area occupancy rate and the spherical sand recovery rate in Example 2. [Diagram 5] 1 is a graph showing the fraction recovery rate for each fraction in Examples 3 to 3-2. [Figure 6] 1 is a graph showing the average particle size for each section of Examples 3 to 3-2. [Figure 7] 1 is a graph showing the average circularity for each section of Examples 3 to 3-2. [Figure 8] 1 is a graph showing the fraction recovery rate for each fraction in Examples 4 to 4-5. [Figure 9] 1 is a graph showing the fraction recovery rates for each fraction in Examples 4-2, 4-4, and 4-5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. (shape separation device) An example of a shape separator used in the shape separation method of sand according to the present invention will be described. Fig. 1 is a perspective view showing an example of the configuration of a shape separator used in the shape separation method of the present invention. As shown in Fig. 1, the shape separator 10 includes an inclined belt conveyor unit 11, an inclination angle adjustment mechanism 12, a belt drive unit 13, a speed adjustment unit 14, a sand supply unit 15, a supply amount adjustment unit 16, a recovery unit 17, and an imaging device 18.

[0013] The inclined belt conveyor section 11 includes an upstream roller 11U, a downstream roller 11L, and a belt 11B that is stretched between the upstream roller 11U and the downstream roller 11L and is movable in a moving direction M indicated by a one-way arrow in FIG. 1. In the embodiment of the present application described later, the belt conveyor uses an Escon Mini SZV30 manufactured by Sanki Engineering Co., Ltd. The belt 11B is an endless belt, and is inclined in the width direction W of the belt 11B with respect to the horizontal plane by an inclination angle adjustment mechanism 12. The mixed sand is dropped onto the surface of the belt 11B from the sand supply section 15, and the mixed sand is made to roll on the surface of the belt 11B, so that the mixed sand can be separated by shape. Here, the mixed sand is sand in which spherical sand and irregularly shaped sand other than spherical sand are mixed. In this specification, the spherical sand refers to sand with an average circularity of 0.9 to 1.0, and the irregularly shaped sand refers to sand with an average circularity of less than 0.9. The average circularity is a value obtained by averaging the circularities of the sand, which will be described later in detail. The types of spherical sand include, for example, spherical artificial sand, irregularly shaped sand whose corners have been rounded off by a mechanical reclaimer such as a reclaimer, and original irregularly shaped sand whose corners have been rounded off by repeated use. In this specification, the sand supplied to the belt 11B by the sand supply unit 15 is also called original sand. The material of the belt 11B is not particularly limited, but may be, for example, rubber, plastic, cloth, metal, alloy, etc., and in this embodiment, it is polyurethane. The material of the surface of the belt 11B may be the same as that of the belt 11B or may be different. The material of the surface of the belt 11B may be, for example, rubber, plastic, cloth, metal, alloy, etc., and in this embodiment, it is polyurethane, the same as the belt. If the material of the surface of the belt 11B has a low friction coefficient, the sand will easily roll on the surface of the belt 11B. If the friction coefficient of the surface of the belt 11B is high, the sand will not easily roll on the surface of the belt 11B. For this reason, it is necessary to determine the moving speed, inclination angle, and supply amount of sand, which will be described later, taking into consideration the material of the belt surface. The belt 11B is driven by a belt driving section 13 which will be described later.

[0014] The inclination angle adjustment mechanism 12 lifts one side of the belt 11B in the direction indicated by the double-headed arrow in FIG. 1 perpendicular to the substantially horizontal moving direction M of the belt 11B (hereinafter, also referred to as the width direction W of the belt 11B) to incline the belt 11B in the width direction W. The inclination angle adjustment mechanism 12 includes a support part that can be extended and retracted vertically and fixed at any position, and is installed so that the belt 11B can be inclined without interfering with the movement in the moving direction M. Here, the angle of inclination (hereinafter, also referred to as the inclination angle) is represented by the inclination (°) of the width direction W of the belt 11B of the upper surface of the belt 11B of the inclined belt conveyor unit 11 relative to the horizontal plane. The angle of inclination can be appropriately selected so that the average circularity of the sand collected in the spherical sand collection tank is 0.9 or more. For example, the angle of inclination is 1° or more and less than 20°, preferably 1 to 18°, more preferably 1 to 16°, and particularly preferably 10 to 16°. If the inclination angle is less than 1°, the spherical sand will roll slowly on the belt surface, and may not fall from the lower side of the belt 11B inclined in the width direction W (hereinafter, simply referred to as the side of the belt 11B or the belt side) before reaching the downstream end in the moving direction. On the other hand, if the inclination angle is 20° or more, in addition to the spherical sand, much of the irregularly shaped sand may roll on the belt surface and fall from the belt side. In either case, the spherical sand and the irregularly shaped sand may not be properly separated.

[0015] The belt drive unit 13 includes a motor as a drive source and a mechanism for transmitting the driving force of the motor to the downstream roller 11L. In the example shown in FIG. 1, the belt drive unit 13 transmits the driving force of the motor to the downstream roller 11L via a belt, but the driving force may be transmitted to the upstream roller 11U. Alternatively, the belt drive unit 13 may drive a drive pulley provided separately from the downstream roller 11L and the upstream roller 11U. The belt drive unit 13 supplies a driving force to the roller or the drive pulley, thereby moving the circumferential surface of the belt 11B stretched between the rollers in the moving direction M. The belt drive unit 13 may be disposed anywhere as long as it can supply a driving force to the roller or the drive pulley. In one example, the belt drive unit 13 is disposed adjacent to the downstream roller 11L as shown in FIG. 1.

[0016] The speed adjustment unit 14 is a circuit that adjusts the rotation speed of the motor of the belt drive unit 13. In the example shown in FIG. 1, the speed adjustment unit 14 is a control circuit that controls the motor of the belt drive unit 13, and can set and adjust the moving speed of the belt 11B by controlling the rotation speed of the motor. The moving speed of the belt 11B can be appropriately selected as long as it is within a range in which the irregularly shaped sand contained in the sand supplied to the inclined belt conveyor does not fall to the side of the belt. In this case, by applying a moving speed within a range in which the irregularly shaped sand contained in the sand supplied to the inclined belt conveyor does not fall to the side of the belt, it is possible to realize a suitable behavior of the sand on the belt in which the spherical sand is collected in the side collection section and the irregularly shaped sand is collected in the downstream collection section. Here, the irregularly shaped sand does not fall to the side of the belt means that the irregularly shaped sand does not fall in an amount such that the average circularity of the mixed sand collected in the side collection section is less than 0.9. The specific moving speed of the belt 11B is, for example, 50 m / min or less, preferably 10 to 50 m / min, more preferably 15 to 40 m / min, even more preferably 20 to 40 m / min, and particularly preferably 25 to 40 m / min. By applying a moving speed of 50 m / min or less at which the irregular sand contained in the sand supplied to the inclined belt conveyor does not fall to the side of the belt, the spherical sand is collected in the side collection section and the irregular sand is collected in the downstream collection section, and the sand behaves in a suitable manner on the belt. Furthermore, when the moving speed exceeds 50 m / min, depending on the inclination angle and the supply amount, much of the irregular sand in addition to the spherical sand rolls and falls to the side of the belt, and the average circularity of the sand in the side collection section may fall below 0.9. On the other hand, when the moving speed is less than 10 m / min, depending on the inclination angle and the supply amount, sand may accumulate on the surface of the belt, and the spherical sand may not roll to the side of the belt, resulting in a low recovery rate of the spherical sand.

[0017] The sand supplying section 15 is provided above the belt 11B near the upstream roller 11U in the moving direction M. The sand supplying section 15 shown in FIG. 1 is a vibrating feeder equipped with a trough 15T. The trough 15T is composed of a base end member 15B and a terminal end member 15S. The base end member 15B has a rectangular bottom surface (base end bottom surface) and side walls surrounding the three sides of the base end bottom surface, and the long sides of the base end bottom surface are along the width direction of the belt 11B. The side walls of the base end member 15B rise from the two long sides of the base end bottom surface and the short side of the high side (opposite the belt side) of the belt 11B inclined in the width direction W. The terminal end member 15S has a right-angled triangular bottom surface (terminal end bottom surface) having a side wall on one side on the upstream end side of the belt 11B. One of the two sides of the bottom surface of the terminal end portion is connected to the short side of the bottom surface of the base end portion that has no side wall, so that the bottom surface of the base end portion and the bottom surface of the terminal end portion are connected. The other side of the bottom surface of the terminal end portion is along the width direction of the belt 11B and is connected to the long side of the upstream end of the bottom surface of the base end portion, and the side wall of the terminal member 15S is connected to the upstream end side of the side wall of the side wall of the base end member 15B. The remaining side of the bottom surface of the terminal end portion is located above the belt 11B and constitutes the tip portion 11F of the trough 15T. The tip portion 11F corresponds to a portion without a side wall that extends from the vicinity of the high end of the belt 11B inclined in the width direction W to the vicinity of the low end (belt side). A supply port not shown in FIG. 1 is provided above the base end member 15B, and mixed sand is supplied to the base end member 15B of the trough 15T by dropping the mixed sand from the supply port to the base end 15B.

[0018] The mixed sand supplied to the base end member 15B of the trough 15T is transported from the base end member 15B to the terminal member 15S by the vibration given to the trough 15T from the supply amount adjustment unit 16, and falls from the tip end 15F onto the belt 11B. The sand supply unit 15 can supply a predetermined amount of mixed sand per unit time to the surface of the belt 11B. In FIG. 1, the sand supply unit 15 is a vibration feeder, but it is not limited to a vibration feeder as long as it is a device that can supply a constant amount of sand to the surface of the belt 11B. For example, a slide gate and a screw feeder may be used. When the sand supply unit 15 is a vibration feeder as shown in FIG. 1, the mixed sand can be dispersed over a wide range from the tip end 11F having a predetermined length in the width direction of the belt 11B and dropped onto the belt 11B. By dispersing and dropping the mixed sand, the spherical sand and the irregularly shaped sand that have fallen onto the belt 11B tend to behave according to their respective shapes.

[0019] The supply amount adjustment unit 16 applies vibration to the trough 15T. By changing the frequency of the vibration applied with a constant amplitude, it is possible to adjust the amount of mixed sand that falls per unit time (supply amount) that is transported from the base end member 15B to the tip end 15F and falls onto the belt 11B. The most upstream position of the tip end 15F in the moving direction M corresponds approximately to the position (upstream end) where the upstream roller 11U of the inclined belt conveyor unit 11 is disposed.

[0020] The collection section 17 includes a spherical sand collection tank 17R provided on the side of the belt 11B along the moving direction M of the belt 11B, and an irregular-shaped sand collection tank 17V provided at the downstream end of the moving direction M. The spherical sand collection tank 17R corresponds to the side collection section, and the irregular-shaped sand collection tank 17V corresponds to the downstream collection section.

[0021] The spherical sand collection tank 17R may be a collection tank that is not divided as shown in FIG. 3, or may be a collection tank that is divided into two or more sections along the moving direction M of the belt 11B as shown in FIG. 1 and FIG. 2. FIG. 3 shows a shape separation device 10 having the same configuration as FIG. 1 and FIG. 2, except that the number of sections of the spherical sand collection tank 17R is one. The spherical sand collection tank 17R is a collection tank that collects the spherical sand that is easy to roll among the mixed sand that falls from the tip end 15F of the sand supply unit 15 onto the belt 11B and rolls due to the inclination of the belt 11B and falls from the side of the belt, that is, a collection tank that collects sand with a high degree of circularity. When the spherical sand collection tank 17R has multiple sections, the number may be set appropriately from the viewpoint of accuracy and efficiency according to the size of the inclined belt conveyor unit 11. The number of sections is, for example, 2 or more, 4 or more, 6 or more, 8 or more, 10 or more, or 15 or more. In addition, the area of ​​belt 11B corresponding to one section (hereinafter also referred to as the belt portion area) is, for example, 50% or less, 25% or less, 20% or less, 15% or less, or 10% or less of the outer circumferential area of ​​belt 11B.

[0022] The irregular sand collection tank 17V has one collection tank. This irregular sand collection tank 17V is a collection tank for sand that does not roll to the side of the belt on the surface of the belt 11B inclined in the width direction, but remains on the surface of the belt 11B and is transported to the downstream end of the belt 11B in the moving direction M, that is, a collection tank for sand with low circularity. The spherical sand collection tank 17R of the shape separation device 10 is provided to collect spherical sand, and the irregular sand collection tank 17V is provided to collect irregular sand. The shape of the irregular sand collection tank 17V is not limited as long as it can collect sand that has fallen from the downstream end of the moving direction of the belt 11B.

[0023] The imaging device fixing part 18F provides a means for fixing the imaging device 18 at a position facing the belt 11B, so that the imaging device 18 can image the imaging area 18A on the belt 11B. The imaging device fixing part 18F may be movable so that the imaging position of the imaging device 18 can be changed, or may be fixed. The imaging device 18 may be any device capable of imaging, and in this embodiment, is a camera. The imaging area 18A is an area in which the imaging device 18 images the belt 11B facing it. The imaging area 18A may be an area including at least one of the locus LU and the locus LL shown in FIG. 2 in the width direction W of the belt 11B, or may be an area closer to the center in the width direction than the locus LU and the locus LL. The imaging area 18A may be an area of ​​any size with the midpoint between the upstream and downstream ends of the belt 11B in the moving direction M as the center of the imaging area, or may be a series of areas including the area of ​​the belt 11B corresponding to the section where the maximum recovery rate was obtained, with the area being at the upstream end (starting end) of the imaging area 18A in the moving direction M, or including that section and one or more sections on the downstream end side of the moving direction M. In a still image obtained by imaging the imaging area 18A with the imaging device 18, the ratio (occupancy rate) of the area of ​​the mixed sand to the area of ​​the imaging area 18A is called the sand area occupancy rate.

[0024] The method for measuring the sand area occupancy is not limited as long as it is possible to calculate the area occupied by the mixed sand relative to the area of ​​the imaging region 18A for which the sand area occupancy is to be calculated. For example, the sand area occupancy may be calculated using a still image captured by a camera, or the sand area occupancy may be calculated by applying Lidar (Light Detection and Ranging) technology. The area occupied by the mixed sand may also be calculated automatically by applying image processing to the still image captured by imaging. The imaging device for measuring the sand area occupancy rate may be any device having a resolution sufficient to recognize the outlines of individual mixed sand particles in the imaging area 18A. In the examples described below, the method used to obtain the sand area occupancy is as follows: A camera is used to capture an image of a certain area on the belt. The captured image is then binarized using software attached to a digital microscope (digital microscope, VHX-600, Keyence Corporation), and the area of ​​the particles in the binarized image is calculated, and the ratio of this area to the area of ​​the entire image is calculated to obtain the sand area occupancy.

[0025] The behavior of the mixed sand dropped onto the belt 11B will be described with reference to FIG. 2. FIG. 2 is a perspective view showing the behavior of the sand when the mixed sand is subjected to shape separation using the shape separator 10 shown in FIG. 1. First, the belt 11B is made to travel in one direction at a moving speed within the above-mentioned range, and the mixed sand containing a mixture of spherical sand and irregularly shaped sand is fed into the sand supplying section 15. The sand supplying section 15 drops a substantially constant amount of the mixed sand onto the belt 11B per unit time. The drop position is near the upstream end of the inclined belt conveyor section 11 in the moving direction M, and the mixed sand is dispersed and dropped in a range from the high side of the width direction W of the inclined belt 11B to the belt side vicinity.

[0026] In this way, the spherical sand that falls on the surface of the belt 11B, which is easy to roll, rolls and falls to the side of the belt due to the inclination of the belt 11B, and is collected in the spherical sand collection tank 17R. The spherical sand that falls near the side of the belt from the tip 15F of the trough 15T follows the trajectory T1 shown in Figure 2 and is collected in the spherical sand collection tank 17R near the upstream end. The spherical sand that falls near the high side of the width direction W follows the trajectory T2 shown in Figure 2 and is collected in the spherical sand collection tank 17R near the downstream end. The spherical sand that falls between the high side of the width direction W and the side of the belt, that is, near the center, follows the trajectory T3 and is collected in the spherical sand collection tank 17R between the upstream end and the downstream end.

[0027] With reference to Examples 3 to 3-2 described later, since small-sized spherical sand is difficult to roll compared to large-sized spherical sand, it tends to be blocked by irregularly shaped sand on the belt 11B and to be collected in the spherical sand collection tank 17R over a longer period of time. This is because large-sized spherical sand has a larger mass than small-sized spherical sand, so it has a larger force to roll to the side of the belt, and even if there is irregularly shaped sand on the belt 11B that does not try to roll to the side of the belt, it is easy to avoid or pass it. Therefore, large-sized spherical sand moves to the side of the belt more quickly than small-sized spherical sand, and as a result, it tends to be collected in the spherical sand collection tank 17R at the more upstream end. Conversely, small-sized spherical sand has a smaller mass than large-sized spherical sand, so it is difficult to avoid or pass the irregularly shaped sand on the belt 11B, so it moves to the side of the belt over a longer period of time, and as a result, it tends to be collected in the spherical sand collection tank 17R at the more downstream end.

[0028] On the other hand, of the mixed sand that falls on the surface of belt 11B, irregularly shaped sand that is difficult to roll remains and is transported in the moving direction M, even if belt 11B is inclined. The irregularly shaped sand that falls near the higher side of belt 11B, which is inclined in the width direction W, follows the trajectory LU shown in Figure 2, falls from the downstream end in the moving direction M, and is collected in irregularly shaped sand recovery tank 17V. The irregularly shaped sand that falls near the side of the belt follows the trajectory LL and is collected in irregularly shaped sand recovery tank 17V. The irregularly shaped sand that falls near the center in the width direction W follows the trajectory LC and is collected in irregularly shaped sand recovery tank 17V.

[0029] When the spherical sand collection tank 17R is composed of one section, the range of a certain image capture area 18A may be determined, imaged, and the sand area occupancy rate may be calculated. Here, the certain image capture area 18A is, for example, an area in the width direction W that includes at least one of the trajectories LU and LL shown in FIG. 2, and is an area between 30% and 60% from the upstream end side when the total length from the upstream end to the downstream end of the belt 11B in the moving direction M is 100%. If it is desired to calculate the sand area occupancy rate more accurately, the spherical sand collection tank 17R may be divided into multiple sections to determine the range of the image capture area 18A.

[0030] When the spherical sand recovery tank 17R is composed of multiple sections, the recovery rate (section recovery rate) of each section recovered based on the total recovery amount (mass of recovered sand) of each section can be calculated, and the section with the highest recovery rate can be determined. The recovery rate of each section can be calculated from the recovery amount of each section based on the mass of sand supplied to the sand supply section. In this case, if a weight sensor is attached to each spherical sand recovery tank 17R, the recovery rate of each section can be automatically calculated. The area of ​​the belt 11B corresponding to the section with the highest recovery rate in the moving direction M is set to the upstream end (starting end) of the imaging area 18A, and the image of the section or a series of areas including the section and one or more sections downstream of the section in the moving direction M can be taken, and the sand area occupancy rate can be calculated. By taking an image of the section with the highest recovery rate or a series of target areas including the section and one or more sections downstream of the section in the moving direction M, it is possible to appropriately capture and judge the behavior of the mixed sand on the belt. The recovery amount rather than the recovery rate may be used to determine the suitable imaging area 18A.

[0031] The sand area occupancy is a parameter indicating the degree of dispersion of the mixed sand on the belt 11B, excluding the spherical sand of large particle size among the mixed sand that has fallen onto the belt 11B. This is because the spherical sand of large particle size is collected in the spherical sand collection tank 17R on the upstream end side of the maximum collection rate section without being affected much by the irregularly shaped sand. Then, the sand area occupancy after the spherical sand of large particle size is small to medium particle size spherical sand and irregularly shaped sand remaining on the belt surface. Since the spherical sand of small to medium particle size is easily affected by the irregularly shaped sand, it takes time to move to the side of the belt. Therefore, the sand area occupancy is related to the behavior of the spherical sand on the belt 11B at the downstream end side of the imaging area 18A. The suitable sand area occupancy is, for example, 0.9 to 30%, preferably 0.9 to 21%, and more preferably 0.9 to 12%. If the sand area occupancy rate is between 0.9% and 30%, the mixed sand can be properly separated into spherical sand and irregularly shaped sand. If the sand area occupancy rate is less than 0.9%, the amount of sand that can be collected per hour is small, and efficient shape separation may not be possible. On the other hand, if the sand area occupancy rate is more than 30%, the spherical sand will not roll on the belt surface due to the irregularly shaped sand blocking it, and most of the spherical sand will be collected in the irregularly shaped sand collection tank 17V, making it impossible to separate the spherical sand from the irregularly shaped sand.

[0032] A specific example of the mixed sand to be subjected to shape separation by the shape separation device 10 is recycled mixed sand. The recycled mixed sand is sand that is processed by roasting waste foundry sand and going through a reclaimer process. To make a casting, a mold is made using sand, molten cast iron is poured into the mold, and after cooling, the mold is broken to remove the casting. The waste foundry sand is the sand in the broken mold. The waste foundry sand includes natural silica sand and artificial sand, and these sands are recycled as sand for molds or for other uses. For example, by separating the recycled mixed sand obtained by processing waste foundry sand into shapes, recycled spherical sand and recycled irregular sand can be recovered as recycled foundry sand. Then, by using the recovered recycled foundry sand, the amount of new foundry sand to be collected can be reduced, and thus the environmental load can be reduced. Therefore, it is meaningful to produce recycled spherical sand and recycled irregular sand from the recycled mixed sand obtained by processing waste foundry sand. Spherical artificial sand is often used in applications requiring particularly high quality foundry sand. If the artificial sand is magnetic, i.e., if it has the property of being attracted to a magnet, it may be subjected to magnetic separation as a pretreatment to separate it from non-magnetic natural silica sand and the like. In this case, the recycled mixed sand to be subjected to shape separation is the recycled mixed sand after magnetic separation. However, the mixed sand to which the sand separation method of this invention is applied is not limited to recycled mixed sand. This sand shape separation method can also be applied to applications in which new foundry sand, whether artificial or natural, is separated into spherical sand and irregularly shaped sand.

[0033] The method for measuring circularity will be described. The method for measuring circularity in the examples is as follows. Sand collected in a spherical sand collection tank or an irregularly shaped sand collection tank is imaged using a digital microscope (digital microscope, VHX-600, Keyence Corporation), and the image is processed (binarized) using software attached to the digital microscope. The area and perimeter of the particles in the image after binarization are measured to calculate circularity, and the circularity of each sand is averaged. The average circularity is calculated through these steps. The series of processes may be automated to calculate the average circularity. The circularity is expressed by the following formula, and the closer the circularity is to 1, the closer it is to a perfect circle. Circularity = 4π × area of ​​sand in binarized image / (perimeter of sand in binarized image) 2 If multiple particles overlap, they must be excluded from the binarization. Since the shaded areas of particles cannot be recognized, only particles with clear outlines are measured as representative particles.

[0034] The supply rate of the sand supply unit 15 is, for example, 0.83 to 8.58 g / s, preferably 1.27 to 5.58 g / s, and more preferably 2.83 to 5.58 g / s. However, this value is a reference value for the device used in the embodiment in which the length of the belt surface in the moving direction is 1.5 m and the length in the width direction is 0.3 m, and the present invention is not limited thereto. As long as a certain mass of mixed sand can be supplied per unit time, there is no limit to the supply rate. In addition, the supply rate may be measured by a sensor, may be calculated by conversion from the vibration frequency, or may be automatically determined based on the measured sand area occupancy rate by measuring the sand area occupancy rate. In addition, in this embodiment, the vibration frequency in the above supply rate is 10 to 27 Hz, preferably 15 to 25 Hz, and more preferably 20 to 25 Hz.

[0035] The average circularity of the raw sand supplied by the sand supply unit 15 is, for example, 0.60 to 0.89, preferably 0.70 to 0.89, more preferably 0.75 to 0.89, and particularly preferably 0.80 to 0.89. If the average circularity of the raw sand is less than 0.60, the proportion of irregularly shaped sand is too high and separation may not proceed smoothly. In this specification, spherical sand is sand with an average circularity of 0.9 to 1.0, so that if the average circularity of the raw sand is 0.9 or more, the object of the present invention has already been achieved. The ratio of spherical sand in the sand supplied by the sand supply unit 15 is, for example, 5 to 94%. Here, the reference recovery rate can be determined from the ratio of spherical sand contained in the sand supplied by the sand supply unit. For example, when a recovery rate of 80% or more is targeted, the reference recovery rate when the ratio of spherical sand in the sand supplied by the sand supply unit 15 is 5% is 4%, which is the ratio of spherical sand (5%) multiplied by the target lower limit value of 80%, and the reference recovery rate when the ratio of spherical sand is 94% is about 75%, which is the ratio of spherical sand (94%) multiplied by the target lower limit value of 80%.

[0036] The mixed sand collected in the spherical sand collection tank 17R rolls on the surface of the belt 11B inclined in the width direction W and falls from the side of the belt, and has a relatively high circularity. The average circularity of the sand collected in the spherical sand collection tank 17R is, for example, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, or 0.95 or more. Here, the reference average circularity is determined according to the purpose of shape separation. That is, it is determined based on the degree of average circularity of the spherical sand to be obtained, and in this embodiment, it is 0.9 or more. Depending on the required average circularity, it may be another value, such as 0.85. The average particle size of the mixed sand collected in the spherical sand collection tank 17R is, for example, 0.1 to 0.5 mm, preferably 0.15 to 0.45 mm, and more preferably 0.18 to 0.40 mm. The calculation method of the average particle size in this embodiment is as follows. A digital microscope (digital microscope, VHX-600, Keyence Corporation) is used to obtain images of the mixed sand particles, and the software attached to the digital microscope is used to calculate the average particle size. Specifically, the particle size of each sand particle obtained after excluding particle groups in which multiple sand particles overlap and performing binarization processing is averaged. Here, if the sand collected in the spherical sand collection tank 17R is sand that has been shape-separated from recycled mixed sand that has been processed from waste casting sand, sand containing a large amount of artificial sand with a high degree of circularity is collected from the spherical sand collection tank 17R. Such sand is also called recycled spherical sand. This allows the waste casting sand to be reused. By recycling, the amount of new sand to be collected is reduced, and thus the burden on the environment can be reduced. If the original sand supplied contains a large amount of sand with a high degree of circularity, the amount of mixed sand collected in the spherical sand collection tank 17R also increases.

[0037] A method for separating spherical sand and irregularly shaped sand using the shape separator 10 will be described. The inclination angle adjustment mechanism 12 is adjusted to a preferred inclination angle, for example, 16°, and the belt 11B is rotated at a preferred moving speed, for example, 38 m / min, to supply sand from the sand supply unit 15. The initial supply amount of sand is, for example, 5.0 g / s. Here, when there is one spherical sand recovery tank 17R, for example, an area of ​​any size with the midpoint between the upstream end and the downstream end of the belt 11B in the moving direction M as the center of the imaging area may be determined as the imaging area 18A. When there are multiple spherical sand recovery tanks 17R, for example, the area of ​​the belt 11B corresponding to the section where the maximum recovery rate was obtained may be set to the upstream end (starting end) of the imaging area 18A, and the imaging area may be determined as a series of areas including that section or one or more sections located on the downstream end side of that section in the moving direction M. The imaging area 18A is imaged while facing the belt 11B, and the area of ​​sand occupying the imaging area 18A is obtained as the sand area occupancy rate.

[0038] If the acquired sand area occupancy rate is not within a preferred range, for example, 0.9 to 21.0%, the amount of sand supplied per hour is changed so that it falls within that range. If the acquired sand area occupancy rate is within the range, for example, 0.9 to 21.0%, but is not within a more preferred range, for example, 0.9 to 12%, the amount of sand supplied may be changed to bring it within the more preferred range.

[0039] The belt 11B is rotated with the inclination angle, moving speed, and supply amount set so that the sand area occupancy rate falls within a preferred range, and sand is supplied from the sand supply unit 15, and the sand is collected in the spherical sand collection tank 17R and the irregular sand collection tank 17V. Then, for example, an image of the sand collected in the spherical sand collection tank 17R is obtained using a digital microscope, and the image is processed (binarized) using software attached to the digital microscope. The area and perimeter of the particles in the image after the binarization process are measured to calculate the circularity of the sand, and the average circularity of each sand is calculated to calculate the average circularity of the collected sand. In addition, the proportion of the sand collected in the spherical sand collection tank 17R is calculated as the collection rate from the amount of sand supplied from the sand supply unit 15. It is confirmed whether the calculated average circularity is equal to or greater than the standard average circularity (for example, a value of 0.9) and the calculated collection rate is equal to or greater than the standard collection rate (for example, a value of 80%), and whether these standards are met. The process of calculating the average circularity from the collected sand and checking whether it satisfies the standard for the average circularity, and calculating the recovery rate from the collected sand and checking whether it satisfies the standard for the recovery rate corresponds to a confirmation step. If the calculated average circularity satisfies the standard and the calculated recovery rate satisfies the standard, the shape separator 10 may be operated with the inclination angle, moving speed and supply amount settings that satisfy the standard to perform shape separation.

[0040] On the other hand, if the calculated average circularity is less than the reference average circularity or the calculated recovery rate is less than the reference recovery rate, in other words, if the calculated average circularity or the calculated recovery rate does not meet the standard, at least one of the inclination angle or the supply amount is changed, and the belt 11B is rotated at the same moving speed as when the sand area occupancy rate was previously obtained to supply sand from the sand supply unit 15, and the sand area occupancy rate is reacquired and it is confirmed that the reacquired sand area occupancy rate is within the specified range. The process of changing at least one of the inclination angle or the supply amount to reacquire the sand area occupancy rate and confirming that the reacquired sand area occupancy rate is within the specified range when at least one of the average circularity or the recovery rate does not meet the standard corresponds to the reacquisition step.

[0041] If the reacquired sand area occupancy is within a preferred range, for example, 0.9 to 21.0%, the belt 11B is rotated with the inclination angle, movement speed, and supply amount set when the sand area occupancy is reacquired, sand is supplied from the sand supply unit 15, and the average circularity and recovery rate of the recovered sand are calculated. It is confirmed whether the calculated average circularity is equal to or greater than the reference average circularity, and the calculated recovery rate is equal to or greater than the reference recovery rate, so that both standards are satisfied. In other words, a confirmation step is performed with the inclination angle, movement speed, and supply amount set when the sand area occupancy is reacquired. If at least one of the calculated average circularity or recovery rate does not satisfy the standard, at least one of the inclination angle or the supply amount is changed, and the belt 11B is rotated with the same movement speed as when the sand area occupancy was previously acquired, sand is supplied from the sand supply unit 15, the sand area occupancy is further reacquired, and it is confirmed that the reacquired sand area occupancy is within the predetermined range. In other words, the above-mentioned reacquisition step is repeated. If both criteria are met, the shape separator 10 may be operated with the inclination angle, moving speed and supply amount set to satisfy the criteria, to perform shape separation.

[0042] On the other hand, if the reacquired sand area occupancy ratio is not within a desired range, for example, 0.9 to 21.0%, the setting is changed to at least a different supply amount, belt 11B is rotated, sand is supplied from sand supply unit 15, and the sand area occupancy ratio is reacquired. The acquisition of the sand area occupancy ratio can be repeated with at least a different supply amount setting until the sand area occupancy ratio falls within the desired range.

[0043] When the reacquired sand area occupancy is not within the desired range, and the reacquired sand area occupancy falls within the desired range by changing the setting to at least a different supply amount, the belt 11B is rotated with the inclination angle, moving speed, and supply amount set at that time to supply sand from the sand supply unit 15, and the average circularity and recovery rate of the recovered sand are calculated, and at least one of the calculated average circularity or recovery rate may not meet the criteria. In that case, after changing at least one of the inclination angle or the supply amount, the belt 11B is rotated at the same moving speed as when the sand area occupancy was previously obtained, sand is supplied from the sand supply unit 15, and the sand area occupancy is further reacquired, and it is confirmed that the reacquired sand area occupancy is within the predetermined range. In other words, the above-mentioned reacquisition step is repeated. Then, depending on the reacquired sand area occupancy ratio, either a process is performed in the case where the reacquired sand area occupancy ratio described above is within a preferable range, or a process is performed in the case where the sand area occupancy ratio is not within a preferable range.

[0044] In the case where at least one of the average circularity and the recovery rate does not meet the standard, after changing the setting of only one of the inclination angle or the supply amount, it may be confirmed again whether the standard of the average circularity and the recovery rate is met without re-acquiring the sand area occupancy rate. In other words, if at least one of the average circularity and the recovery rate does not meet the standard, the belt 11B is rotated with the setting of only the inclination angle or the supply amount changed, sand is supplied from the sand supply unit 15, the sand is recovered, and the average circularity and the recovery rate of the recovered sand are calculated without re-acquiring the sand area occupancy rate, and it is confirmed whether the standard is met. If the standard is met, the shape separator 10 may be operated with the setting of the inclination angle, the moving speed, and the supply amount that meet the standard to perform shape separation. If at least one of the average circularity and the recovery rate does not meet the standard even if only one of the inclination angle or the supply amount is changed, the setting of only one of the inclination angle or the supply amount is further changed. Then, the belt 11B is rotated to supply sand from the sand supply unit 15, and the sand is recovered. Then, without re-obtaining the sand area occupancy ratio, the average circularity and recovery rate of the recovered sand are calculated to confirm whether they satisfy the criteria. In this way, when at least either the average circularity or the recovery rate does not satisfy the criteria, the shape separator 10 may be operated with a setting in which only one of the inclination angle or the supply amount is changed, and the average circularity and recovery rate of the recovered sand are calculated without re-obtaining the sand area occupancy ratio to confirm whether they satisfy the criteria, and these processes may be repeated until the criteria are satisfied.

[0045] In addition, the process of not reacquiring the sand area occupancy rate even if only one of the inclination angle or the supply amount is changed is preferably applied when the difference from the standard is small and it is expected that the average circularity and recovery rate of the sand to be recovered will meet the standard by changing at least one of the inclination angle or the supply amount. The case where it is expected to meet the standard is when it is possible to predict to some extent, for example, from past data or experience, how the average circularity and recovery rate of the sand to be recovered will change when at least one of the inclination angle or the supply amount is changed. For example, if you want to increase the circularity to the standard circularity, it is possible to predict how much the inclination angle should be reduced. Or, for example, if you want to increase the recovery rate to the standard recovery rate, it is possible to predict how much the inclination angle should be increased. Also, if you want to increase the recovery rate to the standard recovery rate, it is possible to predict how much the supply amount should be increased. However, for example, if the supply amount is increased, depending on the belt speed, the sand may not be dispersed well on the belt surface, and the recovery rate may decrease contrary to prediction.

[0046] The mixed sand collected in the irregular sand collection tank 17V is sand with a relatively low circularity that does not roll on the surface of the inclined belt 11B and falls from the downstream end of the belt 11B in the moving direction M. The average circularity of the mixed sand collected in the irregular sand collection tank 17V is, for example, 0.80 to 0.85, although there is no particular standard that must be met. If the mixed sand collected in the irregular sand collection tank 17V is regenerated irregular sand that has been shape-separated from regenerated mixed sand obtained by treating waste casting sand, specific sand with a low circularity is collected. If the raw sand supplied contains a large amount of sand with a low circularity, the amount of mixed sand collected in the irregular sand collection tank 17V also increases. EXAMPLES

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0048] <Magnetic separation process> In this embodiment, the spherical artificial sand contained in the waste foundry sand is magnetic. Therefore, as a pretreatment, the waste foundry sand was roasted and reclaimed to obtain 1000 kg of regenerated mixed sand, which was then subjected to magnetic separation treatment using a magnetic separation treatment device (counter-pole magnetic separator, model G-30+30, Japan Magnetic Separation Co., Ltd.) to remove non-magnetic sand. Then, 150 kg of magnetic sand was obtained as the original sand.

[0049] <Circularity Analysis> The circularity of the obtained original sand was measured by taking images using a digital microscope (digital microscope, VHX-600, Keyence Corporation) and calculating the circularity using the software attached to the digital microscope. As a result, the average circularity of the original sand was 0.85. The maximum circularity of the original sand was 0.96, and the minimum was 0.44.

[0050] <Elemental analysis> The obtained raw sand was subjected to elemental analysis using an analytical device (X-ray fluorescence analyzer, ZSX PRIMUS II, Rigaku Corporation), and the results are summarized in Table 1. [Table 1]

[0051] Example 1 Belt inclination angle and sand behavior Using the shape separator 10 equipped with the spherical sand recovery tank 17R with one division as shown in FIG. 3, the inclination angle of the belt 11B in the width direction W with respect to the horizontal plane was changed to five different angles of 16°, 10°, 9°, 5°, and 1°. In each case, the belt 11B was run in the moving direction M shown in FIG. 1 at a moving speed of 38.3 m / min, 200 g of original sand was fed into a vibration feeder (small electromagnetic feeder, CF-1, Sinfonia Technology Co., Ltd.) installed in the sand supply section 15, and the original sand was dropped onto the surface of the belt 11B at a supply rate of 2.83 g / s from the drop port of the vibration feeder. The sand that had fallen from the side of the belt was then collected in the spherical sand recovery tank 17R, and the recovery rate and average circularity of the obtained sand were calculated. The results of Example 1 are summarized in Table 2. [Table 2]

[0052] From the results in Table 2, it was found that the larger the inclination angle, the higher the recovery rate of the spherical sand. The recovery rate shown in Table 2 is the ratio of sand recovered in the spherical sand recovery tank 17R to the original sand. The original sand in Example 1 contains about 30% spherical artificial sand. The recovery rate exceeds 30% because the original sand contains rounded artificial sand that cannot be detected by the analytical equipment in addition to the 30% artificial sand that can be detected by the analytical equipment. On the other hand, it was found that the smaller the inclination angle, the higher the average circularity tends to be. This is thought to be because sand with a higher circularity rolls on the belt surface even if the inclination angle is small. It was also found that spherical sand with an average circularity of 0.9 or more can be obtained if the inclination angle is between 1 and 16 degrees. However, when the inclination angle is in the range of 1 to 10 degrees, the spherical sand does not move much on the belt 11B, so the recovery rate of the spherical sand is a small value of less than 10%, and the productivity of the spherical sand recovery is not high. However, the average circularity of the sand recovered in the spherical sand recovery tank 17R is high. On the other hand, although not shown in Example 1, when the inclination angle is set to 20°, almost all the sand falls from the side of the belt and into the spherical sand recovery tank 17R. A practical inclination angle is in the range of 1 to 16°, and when a higher recovery rate is aimed for, it is 10 to 16°. Based on the relationship between the spherical sand recovery rate and the average circularity in Table 2, it was decided to carry out the experiment of the next Example 2 at an inclination angle of 16°, where the spherical sand recovery rate is high and the average circularity is greater than the boundary of 0.9.

[0053] Example 2 Relationship between sand area occupancy rate and recovery rate Using the shape separator 10 shown in FIG. 3, the inclination angle of the belt 11B in the width direction W to the horizontal plane was set to 16°, and the moving speed of the belt 11B in the moving direction M was set to 27.0, 38.3, and 54.0 m / min. The supply amount of the sand supplying section 15 was set to 0.83, 0.86, 1.27, 2.83, 5.59, 8.58, 9.46, and 14.46 g / s, and shape separation was performed. The position 30 cm from the upstream end of the belt 11B was set as the starting point, and the position 70 cm was set as the end point, and the sand area occupancy rate in the region excluding the upper and lower 10% in the width direction W of the belt, and the recovery rate and average circularity of the sand recovered in the spherical sand recovery tank 17R were obtained. The results are shown in Table 3, and a graph plotted from them is shown in FIG. 4. The X-axis of FIG. 4 is the sand area occupancy rate, and the Y-axis is the recovery rate.

[0054] [Table 3]

[0055] The recovery rate shown in Table 3 is the ratio of sand recovered in the spherical sand recovery tank 17R to the original sand. As shown in Figure 4, when the inclination angle is set to a constant value (16°) and the moving speed of the belt 11B and the amount of sand supplied are changed, the sand area occupancy rate and the recovery rate of the sand recovered in the spherical sand recovery tank 17R show a high correlation. And, if the sand area occupancy rate is low and the mixed sand on the belt 11B is somewhat sparse, a high recovery rate can be obtained. When the average circularity was calculated, it was confirmed that almost all of the spherical sand obtained was 0.9 or more. The only time the average circularity was less than 0.89 was when the moving speed of the belt 11B was the fastest, 54.0 m / min. In that case, it is considered that the irregularly shaped sand that fell onto the belt was pushed by the moving belt and tended to roll and fall to the side of the belt. Therefore, the upper limit of the moving speed of belt 11B for obtaining spherical sand with an average circularity of 0.9 or more is 50 m / min, and the moving speed of belt 11B for obtaining spherical sand stably with a high recovery rate should be a little slower; in the examples of Table 3, 38.3 m / min or 27.0 m / min are preferable values. From Table 3, under the condition that the moving speed of the belt 11B is 27.0 to 38.3 m / min, the sand area occupancy rate at which spherical sand having an average circularity of 0.9 or more can be obtained is 0.9 to 31.2%, of which the sand area occupancy rate at which a recovery rate of 5% or more can be obtained is 0.9 to 21.0%, and the sand area occupancy rate at which a recovery rate of 25% or more can be obtained is 0.9 to 11.6%. Also, in Table 3, the results of carrying out the operation with the belt moving speed of 27.0 m / min and the sand supply amount of 14.46 g / s showed that the sand area occupancy rate was 31.2%, and the recovery rate of the spherical sand was 0.91%. It can be seen that when the sand area occupancy rate exceeds 30%, the recovery rate of the spherical sand becomes a low value of 0.91%, so it is considered that most of the spherical sand was recovered in the irregular sand recovery tank 17V. For this reason, it is considered that the sand area occupancy rate is the upper limit of 30%.

[0056] Example 3: Sand behavior as shown by experiments using a compartmented spherical sand collection tank Using a shape separator 10 having a divided spherical sand recovery tank 17R as shown in FIG. 2, the inclination angle of the belt 11B and its horizontal surface was set to 16°, and the belt 11B was run at 27 m / min in the moving direction M. 200 g of new original sand was fed into a vibration feeder (small electromagnetic feeder, CF-1, Sinfonia Technology Co., Ltd.) installed in the sand supply section 15, and the original sand was dropped onto the surface of the belt 11B at a supply rate of 2.83 g / s from the tip 15F of the vibration feeder. The sand that fell from the side of the belt was collected in a spherical sand recovery tank 17R that was evenly divided into 15 sections, and the recovery rate (section recovery rate) of each section of the obtained sand was calculated. In this example, the section recovery rate is the ratio of the yield of each section to the total amount of sections 1 to 15. In addition, the average circularity of each section of the obtained sand was calculated. Furthermore, the average particle size of each of the obtained sand sections was calculated using software attached to the digital microscope, which captured images of the sand particles. In addition, for the above 15 sections, the spherical sand collection tank 17R close to the upstream roller was numbered consecutively in the belt movement direction M, with the tank being numbered as 1 (hereinafter, the same applies when the spherical sand collection tank 17R is divided into 15 sections).

[0057] Example 3-1 The same procedure as in Example 3 was carried out except that the belt 11B was moved in the moving direction M at 38.3 m / min and the base sand was dropped onto the surface of the belt 11B at a supply rate of 5.59 g / s.

[0058] Example 3-2 The same procedure as in Example 3 was carried out except that the inclination angle between belt 11B and its horizontal plane was set to 10°, belt 11B was run at 38.3 m / min in the moving direction M, and the source sand was dropped onto the surface of belt 11B at a supply rate of 5.59 g / s. The only difference from Example 3-1 was the inclination angle.

[0059] The results of the division recovery rate, average circularity and average particle size of Examples 3 to 3-2 are summarized in Tables 3-1 to 3-6 (the numbers in parentheses in the Examples represent (inclination angle (°)-belt speed (m / min)-sand supply amount (g / s). The same applies below). In addition, a graph of each division and division recovery rate in Examples 3 to 3-2 is shown in FIG. 5, a graph of the division and average particle size is shown in FIG. 6, and a graph of the division and average circularity is shown in FIG. 7.

[0060] [Table 3-1]

[0061] [Table 3-2]

[0062] [Table 3-3]

[0063] [Table 3-4]

[0064] [Table 3-5]

[0065] [Table 3-6]

[0066] With reference to Table 3-1, Table 3-2 and FIG. 5, it was found that the position of the maximum division recovery rate of the spherical sand recovery tank 17R divided into 15 changes depending on the sand supply amount, the belt speed and the inclination angle. The specific positions of the maximum division recovery rate are the third division in Example 3, the fourth division in Example 3-1 and the seventh and eighth divisions in Example 3-2. When the inclination angle is small (10°), there is a tendency for the division to move from the upstream end to the side of the belt over time. Looking at the overall tendency from the upstream end to the downstream end, it was found that the division recovery rate of the division on the downstream end side of the belt 11B tends to decrease as the division approaches the downstream end side from the division with the maximum division recovery rate. This is considered to be because the amount of sand that can roll to the side of the belt is less on the downstream end side of the belt 11B. Note that, when implementing with multiple divisions, the number of divisions is not limited to 15, but if the number of divisions is too small, the positioning of the imaging area 18A becomes rough, so for example, 10 or more divisions are preferable.

[0067] Next, referring to Table 3-3, Table 3-4 and FIG. 6, it was found that the sand collected in the downstream end section of the belt 11B tends to have a smaller average particle size than the sand collected in the upstream end section in the moving direction. From this result, it can be said that the heavy sand, which falls onto the belt 11B and tends to finish rolling to the side of the belt before moving to the downstream end, tends to finish rolling to the side of the belt, as described above, since the spherical sand with a large average particle size, i.e., the sand with a large mass and weight, is collected in the spherical sand collection tank 17R in the upstream end section. In other words, it is considered that the heavy sand can roll to the side of the belt without taking a long time. On the other hand, the spherical sand with a small average particle size, i.e., the sand with a small mass and weight, is collected in the spherical sand collection tank 17R on the downstream end side, tends to finish rolling to the side of the belt. In this way, by measuring the average particle size of the section where the spherical sand is collected, it can be seen that the trajectory of the sand on the belt surface differs depending on the average particle size.

[0068] Furthermore, referring to Tables 3-5, 3-6 and Figure 7, it can be seen that the average circularity is almost constant regardless of the position of the sections in the spherical sand recovery tank. This is believed to indicate that as long as the inclination angle, belt speed and sand supply amount are within certain ranges, the mixed sand can be separated into spherical sand and irregularly shaped sand regardless of the position of the sections. Next, the inclination angle and moving speed of the belt 11B and the supply amount of the sand supply section 15 were changed to investigate the effects of these conditions on the sand area occupancy, recovery rate and section recovery rate.

[0069] Example 4: Effects of inclination angle, moving speed and supply amount on sand area occupancy rate, recovery rate and section recovery rate As in Example 3, using a shape separation device 10 having a divided spherical sand recovery tank 17R as shown in Figure 2, 200 g of new original sand was added to a vibrating feeder (small electromagnetic feeder, CF-1, Symphonia Technology Co., Ltd.) installed in the sand supply section 15, and the original sand was dropped onto the surface of the belt 11B from the drop outlet of the vibrating feeder. The inclination angle of the belt 11B was set to 16°, the moving speed to 27 m / min, and the supply amount to 2.83 g / s. The sand that fell from the side of the belt was collected in the spherical sand collection tank 17R, which was divided into 15 equal sections. The yield of all sections of the spherical sand collection tank 17R was calculated as the spherical sand recovery rate based on the recovery rate (section recovery rate) of each section of the obtained sand and the supply amount of the original sand. In addition, the average circularity of all sections of the spherical sand collection tank 17R was calculated. Furthermore, the imaging area 18A listed in Table 4 below was captured using a camera (digital camera, EOS KISS X7, Canon Inc.), and the sand area occupancy rate of the captured image was calculated using image processing software attached to the digital microscope VHX-600 manufactured by Keyence Corporation.

[0070] Example 4-1 The inclination angle was set to 16°, the travel speed to 38.3 m / min, and the feed rate to 2.83 g / s.

[0071] Example 4-2 The inclination angle was set to 16°, the travel speed to 38.3 m / min, and the feed rate to 5.59 g / s.

[0072] Example 4-3 The inclination angle was set to 10°, the moving speed was set to 38.3 m / min, and the feed rate was set to 2.83 g / s.

[0073] Example 4-4 The inclination angle was set to 10°, the travel speed was set to 27 m / min, and the feed rate was set to 5.59 g / s.

[0074] Examples 4-5 The inclination angle was set to 10°, the travel speed was set to 38.3 m / min, and the feed rate was set to 5.59 g / s.

[0075] The results of the imaging area 18A, inclination angle, moving speed, supply amount, recovery rate, sand area occupancy rate and average circularity for Examples 4 to 4-5 are summarized in Table 4, and the results of the classification recovery rates for Examples 4 to 4-5 are summarized in Table 5-1, Table 5-2, Figures 8 and 9.

[0076] [Table 4]

[0077] [Table 5-1]

[0078] [Table 5-2]

[0079] With reference to Table 4, the average circularity did not change even when the conditions of sand supply amount, belt speed, and inclination angle were changed. This is thought to be because, if the inclination angle is within a certain range, spherical sand rolls on the belt surface, while irregularly shaped sand has difficulty rolling on the belt surface. The recovery rate of spherical sand was higher at an inclination angle of 16° than at an inclination angle of 10°. This is thought to be because, at an inclination angle of 10°, the smaller spherical sand is blocked by the irregularly shaped sand and does not roll all the way to the side of the belt before reaching the downstream end. Also, with reference to Tables 4, 5-1, 5-2, and FIG. 8, it can be seen that, for Examples 4 to 4-2 with an inclination angle of 16°, the maximum sectional recovery rate is near section 3, whereas, for Examples 4-3 to 4-5 with an inclination angle of 10°, the maximum sectional recovery rate is section 6. It is thought that when the recovery rate is high, the section where the maximum sectional recovery rate is obtained tends to be the upstream end side of the belt 11B. When the amount of sand supplied from the original sand is large as in Examples 4-2, 4-4, and 4-5, the sand area occupancy rate is 4.00%, 6.01%, and 4.06%, respectively, which is higher than that of Examples 4, 4-1, and 4-3. This is thought to be because when the amount of sand supplied is large, a lot of sand is scattered on the belt surface, so that a lot of mixed sand remains on the belt surface. It can be seen from Tables 4, 5-1, 5-2, and FIG. 9 that the sand area occupancy rate increases regardless of the inclination angle at 10 to 16 degrees, that is, regardless of the maximum recovery position of spherical sand. Comparing Examples 4, 4-1, 4-4, and 4-5, the recovery rate of spherical sand does not change significantly in the range of moving speeds of 27 to 38.3 m / min even when the belt speed is changed. Also, comparing Examples 4-1 and 4-2, the amount of sand supplied in Example 4-2 is about twice that of Example 4-1, and the recovery rate of spherical sand is about 1.4 times higher in Example 4-2 than in Example 4-1. However, when Examples 4-1 and 4-3 were compared, it was found that the recovery rate in Example 4-1 was more than twice as high as that in Example 4-3, merely because the angle was different.

[0080] From the above examples, the following can be said. In order to perform appropriate shape separation using the inclined belt conveyor type shape separator shown in Figs. 1 to 3, the spherical sand should be collected in the spherical sand collection tank 17R, and the irregular sand other than the spherical sand should be collected in the irregular sand collection tank 17V. To achieve this, the moving speed of the belt 11B should be set so that the irregular sand of the mixed sand that has fallen onto the belt 11B can move to the downstream end along the moving direction M as shown by the trajectories LU, LC, and LL in Fig. 2 without rolling and falling to the side of the belt. According to the second embodiment, it is 50 m / min or less. However, if the moving speed of the belt is slow, the amount of sand that can be collected per hour is small, so a suitable moving speed is determined by balancing the two. One example of a preferred range of the moving speed is 25 to 40 m / min.

[0081] The preferred range of the supply amount varies depending on the size of the equipment (shape separator 10). The sand area occupancy rate can be used as an index for determining the supply amount. The preferred supply amount can be determined by setting the sand area occupancy rate to 0.9% or more and 30% or less.

[0082] In addition, from the results of Example 1, the larger the inclination angle of the belt 11B, the higher the recovery rate of the spherical sand. On the other hand, the smaller the inclination angle of the belt 11B, the higher the average circularity of the sand, that is, the sand with a shape closer to a perfect sphere, tends to be recovered in the spherical sand recovery tank 17R. However, if the inclination angle of the belt is small, the amount of spherical sand that can be recovered per hour is small, that is, the productivity of the spherical sand is not high, so a suitable inclination angle should be determined based on the balance between the average circularity of the recovered sand and the amount of recovery per hour. However, if the inclination angle is set to 20°, in addition to the spherical sand, the irregularly shaped sand also falls to the side of the belt, so the inclination angle should be set to less than 20°. The suitable inclination angle is an angle at which sand with an average circularity of 0.9 or more is obtained in the spherical sand recovery tank. In that case, from the results of Example 1, the practical inclination angle when separating the spherical sand and the irregularly shaped sand is in the range of 1 to 16°. One example of a preferred range considering the balance with the amount of recovery per hour is 10 to 16°.

[0083] (1) When sand is subjected to shape separation using a shape separator in which the circumferential length and width of the belt 11B are fixed and the inclination angle is variable as shown in Figs. 1 to 3, the inclination angle should be set to the upper limit of the preferred conditions (for example, 16° based on Example 1) or less. The moving speed should be set to the upper limit of the preferred conditions (for example, 50 m / min based on Example 2) or less under which irregularly shaped sand is difficult to roll. The supply amount of the sand supply unit 15 should be set so that the average circularity of the spherical sand recovered in the spherical sand recovery tank 17R is equal to or greater than the reference average circularity and the recovery rate is equal to or greater than the reference recovery rate at an inclination angle of 16° or less and a moving speed of 50 m / min or less.

[0084] (2) When the original sand is subjected to shape separation at a preferred range of inclination angle and moving speed, the amount of sand supplied by the sand supplying unit 15 is set so that a predetermined range of sand area occupancy rate (for example, 0.9 to 11.6% based on Example 2) is obtained. It is preferable that the imaging area 18A for obtaining the sand area occupancy rate is an area including the section where the maximum recovery amount was obtained as the start end on the upstream end side, or that section and one or more series of sections located downstream of that section in the movement direction. It is confirmed that shape separation that satisfies the standard average circularity and standard recovery rate is achieved at that inclination angle, moving speed and supply amount.

[0085] (3) When shape separation that satisfies the standard average circularity and the standard recovery rate is not achieved, the parameters to be corrected can be determined from the knowledge based on the embodiment. For example, when the sand recovered in the spherical sand recovery tank 17R satisfies the standard recovery rate but does not satisfy the standard average circularity, the inclination angle can be set smaller. On the other hand, when the sand satisfies the standard average circularity but does not satisfy the standard recovery rate, the inclination angle can be set larger. To increase the accuracy of parameter determination, a curve showing the recovery rate for each section as shown in the graph of FIG. 5 under that condition is plotted, and the main difference from the ideal curve when the standard average circularity and the standard recovery rate are satisfied is determined to determine the parameters to be adjusted. For example, when it is determined that the section where the recovery rate reaches its peak is too close to the downstream end of the belt 11B, the inclination angle can be set larger. This is because when the inclination angle is small, the position of the section where the recovery rate reaches its peak tends to be closer to the downstream end.

[0086] (4) When the amount of sand collected in one section near the downstream end is small, the ratio (recovery rate) of the sand collected in the spherical sand collection tank 17R to the sand supplied from the sand supply unit 15 may also be low. This is considered as follows. When the sand area occupancy rate is low, the spherical sand that rolls easily on the belt 11B falls almost to the side of the belt in the upstream. Near the downstream end, there is less sand that rolls to the side of the belt, and the spherical sand that is difficult to roll moves directly to the downstream end. Therefore, the recovery rate is low. There is a method of increasing the inclination angle to increase the recovery rate, but fine adjustment is difficult. It is considered that the number of rolling sands increases and the recovery rate is increased by increasing the amount of sand supplied within a preferable range. This is because when the amount of supply is large, the peak becomes gentle and the base on the downstream end also tends to become gentle. In this way, fine adjustment of the conditions can be made to satisfy the standard average circularity and the standard recovery rate. [Explanation of symbols]

[0087] 10: Shape separation device, 11: Inclined belt conveyor section, 11B: Belt, 11L: Downstream roller, 11U: Upstream roller, 12: Incline angle adjustment mechanism, 13: Belt drive section, 14: Speed ​​adjustment section, 15: Sand supply section, 15B: Base end member, 15F: Tip section, 15S: End member 15T: Trough, 16: Supply amount adjustment section, 17: Recovery section, 17R: Spherical sand recovery tank, 17V: Deformed sand recovery tank, 18: Imaging device, 18A: Imaging area, 18F: Imaging device fixing section

Claims

1. A method for separating spherical sand and irregularly shaped sand using a shape separator including an inclined belt conveyor section inclined in the width direction of a belt, a sand supply section for supplying sand to the inclined belt conveyor section, a side recovery section for recovering sand that falls to the side in the width direction of the belt, and a downstream recovery section for recovering sand that falls at the downstream end of the belt in the moving direction, comprising: A step of rotating the belt at a predetermined inclination angle and a predetermined moving speed, supplying sand from the sand supply unit, and obtaining the area of ​​sand occupying the area on the belt as a sand area occupancy rate while viewing the area on the belt from the opposite direction; A step of changing the amount of sand supplied per hour so that the sand area occupancy rate falls within a predetermined range; a confirmation step of recovering sand in the side recovery section and the downstream recovery section while the sand area occupancy rate is within a predetermined range, determining an average circularity of the sand recovered in the side recovery section and a recovery rate representing the proportion of the sand recovered in the side recovery section out of the sand supplied from the sand supply section, and confirming whether or not the criteria that the average circularity is equal to or greater than a standard average circularity and the recovery rate is equal to or greater than a standard recovery rate are satisfied; If the criteria are not satisfied, the belt is rotated with at least one of the settings relating to the inclination angle, the moving speed, and the supply amount changed, and the sand area occupancy is reacquired to confirm that it is within the predetermined range. If the sand area occupancy rate acquired in the reacquisition step is within a predetermined range, the confirmation step is executed with the settings when the reacquisition step was executed, and if the criteria are not satisfied, the process is repeated from the reacquisition step; and operating the shape separator at a setting where the criteria are satisfied to perform shape separation.

2. 2. The shape separation method according to claim 1, wherein, if the criterion is not satisfied in the confirmation step, the confirmation step is executed with a different setting for only one of the inclination angle or the supply amount among the settings relating to the inclination angle, the moving speed, and the supply amount, without executing the re-acquisition step and the repeating step, and if the criterion is not satisfied, this step is repeated so that the criterion is satisfied without re-acquiring the sand area occupancy rate.

3. 2. The shape separation method according to claim 1, further comprising the steps of: if the sand area occupancy ratio acquired in the re-acquisition step is not within a predetermined range, changing at least the supply amount setting to bring the sand area occupancy ratio into the predetermined range; executing the confirmation step with the setting when the sand area occupancy ratio is within the predetermined range; and repeating the process from the re-acquisition step if the criterion is not satisfied.

4. 2. The shape separation method according to claim 1, wherein the predetermined moving speed is a moving speed within a range in which irregularly shaped sand contained in the sand supplied to the inclined belt conveyor section does not fall to the side of the belt.

5. 2. The shape separation method according to claim 1, wherein the reference average circularity is determined according to a purpose of the shape separation, and the reference recovery rate is determined according to a proportion of spherical sand contained in the sand.

6. 2. The shape separation method according to claim 1, wherein the step of acquiring the sand area occupancy rate is a step of determining a section in which the maximum recovery rate is obtained in a side recovery section divided in the moving direction of the belt, determining a target area as the section in which the maximum recovery rate is obtained or a series of areas including that section and one or more sections downstream of that section in the moving direction, and acquiring the sand area occupancy rate using an image obtained by photographing the target area.

7. The shape separation method according to claim 1 , wherein the sand supplied from the sand supply unit is recycled mixed sand in which the spherical sand and the irregularly shaped sand are mixed.

8. 5. The shape separation method according to claim 4, wherein the moving speed within a range in which irregularly shaped sand contained in the sand supplied to the inclined belt conveyor does not fall to the side of the belt is 50 m / min or less.

9. The shape separation method according to claim 1 , wherein the predetermined range of the sand area occupancy is 0.9% or more and 30% or less.

10. 2. The shape separation method according to claim 1, wherein the inclination angle is from 1 to 16 degrees with respect to the horizontal.

11. 2. The shape separation method according to claim 1, wherein the sand supply unit is a vibrating feeder equipped with a trough, the trough having a base end where sand is replenished and a tip end that supplies the replenished sand to the belt, and the tip end drops sand onto the belt from an end having a predetermined length in the width direction of the belt.

12. A method for producing recycled spherical sand and recycled irregularly shaped sand by separating spherical sand and irregularly shaped sand using a shape separation device including an inclined belt conveyor section inclined in the width direction of a belt, a sand supply section for supplying sand to the inclined belt conveyor section, a side recovery section for recovering sand that falls to the side in the width direction of the belt, and a downstream recovery section for recovering sand that falls at the downstream end of the belt in the moving direction, comprising: A step of rotating the belt at a predetermined inclination angle and a predetermined moving speed, supplying sand from the sand supply unit, and obtaining the area of ​​sand occupying the area on the belt as a sand area occupancy rate while viewing the area on the belt from the opposite direction; A step of changing the amount of sand supplied per hour so that the sand area occupancy rate falls within a predetermined range; a confirmation step of recovering sand in the side recovery section and the downstream recovery section while the sand area occupancy rate is within a predetermined range, determining an average circularity of the sand recovered in the side recovery section and a recovery rate representing the proportion of the sand recovered in the side recovery section out of the sand supplied from the sand supply section, and confirming whether or not the criteria that the average circularity is equal to or greater than a standard average circularity and the recovery rate is equal to or greater than a standard recovery rate are satisfied; If the criteria are not satisfied, the belt is rotated with at least one of the settings relating to the inclination angle, the moving speed, and the supply amount changed, and the sand area occupancy is reacquired to confirm that it is within the predetermined range. If the sand area occupancy rate acquired in the reacquisition step is within a predetermined range, the confirmation step is executed with the settings when the reacquisition step was executed, and if the criteria are not satisfied, the process is repeated from the reacquisition step; and operating said shape separator at a setting where said criteria are satisfied to effect shape separation.

13. A method for producing recycled spherical sand and recycled irregularly shaped sand as described in claim 12, wherein, if the criterion is not satisfied in the confirmation step, the confirmation step is executed without executing the re-acquisition step and the repeating step, and with only one of the settings relating to the inclination angle, the moving speed, and the supply amount being changed, and if the criterion is not satisfied, this step is repeated so that the criterion is satisfied without re-acquiring the sand area occupancy ratio.

14. A method for producing recycled spherical sand and recycled irregularly shaped sand as described in claim 12, further comprising the steps of: if the sand area occupancy ratio acquired in the re-acquisition step is not within a predetermined range, setting at least the supply amount differently to bring the sand area occupancy ratio into the predetermined range, executing the confirmation step with the setting when the sand area occupancy ratio is within the predetermined range, and repeating the process from the re-acquisition step if the criterion is not satisfied.

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