JPS60244445A - Separating and recovering method of used molding sand - Google Patents

Abstract

PURPOSE:To recover efficiently and inexpensively used molding sand at high purity by separating said sand to magnetically stuck sand and non-magnetically stuck sand by magnetic separation and recovering the magnetically stuck sand to a system for recovering the metallic mold sand and a system for recovering the shell sand. CONSTITUTION:The sand mixture 2 recovered from used casting molds is conducted via a hopper 6 to the inside of a crusher 1. The crushed sand mixture 7 is conducted via a belt conveyor 8 and a hopper 9 to a screening device 10. The lumped sand mixture 15 is removed by the device 10 and the sand mixture 18 having the size smaller than a prescribed size is conducted to the down stream by conveyor 17. The ferromagnetic material 24 contained in the sand mixture 18 is removed by an auxiliary magnetic separator 19. The sand mixture 28 from which the ferromagnetic material is removed is conducted to a magnetic separator 27, by which the sand is separated to the magnetically stuck sand 29 and the non-magnetically stuck sand 30. The sands are conducted respectively to tanks 33, 34 where the sands are recovered as base sand for green sand and base sand for shell sand.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to casting, and more particularly to a method for separating and recovering used foundry sand. BACKGROUND OF THE INVENTION Molding sand used to form molds has conventionally been recycled and recycled repeatedly as recycled foundry sand from the viewpoint of economy and resource conservation. Generally, molds used to manufacture castings with hollow parts, such as cylinder blocks for internal combustion engines, consist of a main mold (green mold) that forms the main part of the casting, and a core (green mold) that forms the hollow part. −
The green mold is made of silica sand with the addition of an inorganic binder such as clay or bentonite, raw nail water, coal powder, etc., and the shell mold is made of silica sand. )
It is formed from shell sand to which an organic binder such as J-Nor resin is added. When recovering foundry sand from used molds made of such green molds and shell molds, the types of green mold sand and shell sand, as well as the type and suspension of binders added to them, differ from each other. Therefore, if green mold sand or shell sand contains iI9 of the other sand, problems such as an increase in the amount of binder added and an increase in the number of strokes required for recycling will occur, so green mold sand and shell sand should not be mixed with each other. It is desirable to separate them from each other and recover them as much as possible. However, some of the molds after spinner V1 lost their bonding strength and collapsed due to the thermal effect of melt-lifting, and also collapsed due to mechanical force during the transportation process (dismantling), resulting in Mold sand and shell sand come in various forms, from single grains to lumps, and are easy to mix with each other!: It is very difficult to reliably separate them from each other and collect them, and in that case, there is no possibility of mixing. Ratio t) Iti
The formation f[, varies greatly depending on the casting equipment, etc. As one way to deal with this problem, when a mixture of lumpy green sand and shell sand is sieved, the green mold sand to which an inorganic binder has been added as a binder tends to crumble; A method is known in which a mixed sand of green mold sand and shell sand is separated into green mold sand and shell sand by utilizing the property that shell sand to which an organic binder has been added is less susceptible to l'Ji1. However, depending on such a method, it is not possible to separate the mixed sand collected as a single grain or in a state close to it into green mold sand and shell sand at a height of l4ii. In addition, as other methods for dealing with the above-mentioned problems, methods disclosed in Japanese Patent Publication No. 55-4510, Japanese Patent Application Laid-open No. 58-128246, and No. 58-1282/18 Mei III are known. In each of these methods, used foundry sand is subjected to magnetic separation to remove magnetic particles as impurities, and non-magnetic particles are recycled. The aim is to reuse this as sill sand. However, in these methods, there is a problem that if the quality of the recovered sand is improved, the recovery rate of the recovered sand decreases due to breakage, and depending on these methods, used foundry sand Both the green mold sand and shell sand are tl, respectively.
There is a problem in that it cannot be separated and recovered using IA N11. In view of the above-mentioned problems in the conventional method of recovering foundry sand, the inventors of the present application have decided to collect used foundry sand by magnetic separation! As a result of conducting an experimental study to separate H1M sand and non-magnetic sand, and to examine in detail the components and properties of H1M sand and non-magnetic sand, it was found that H1M sand and non-magnetic sand were not found. It has components and properties suitable for use as green mold sand and shell sand,
It has also been found that, prior to magnetic separation, it is preferable to process used foundry sand into single grains of a predetermined size or less, or into a state close to it. Purpose of the Invention The present invention is based on the knowledge obtained as a result of experimental research carried out by the inventors of the present invention, and is based on the knowledge obtained as a result of experimental research carried out by the inventors of the present invention. The purpose is to provide a method that can be used to collect waste. According to the invention, the above-mentioned object is to collect molding sand of a predetermined size or less from a used mold consisting of a green mold and a shell mold, and separate it into magnetic sand and non-fi1 by magnetic separation. Sand arrival P1
11. This is achieved by a method for separating and recovering used foundry sand, in which the magnetic sand is recovered into a green mold sand recovery system, and the non-magnetic sand is recovered into a shell sand recovery system. Functions and Effects of the Invention According to the present invention, used foundry sand containing green sand and shell sand is separated into magnetic sand and non-magnetic sand by magnetic separation, and the magnetic sand and non-magnetic sand are separated from each other by magnetic separation. Focusing on the fact that it has components and properties suitable for use as green molding sand and shell sand, instead of discarding the magnetically attached material as impurities! i Magnetized sand and non-magnetic sand are recovered as green mold sand recovery system and shell Sunagawa source sand, respectively, so both green mold sand and shell sand have higher purity and higher recovery rate than used foundry sand. can be recovered. According to the present invention, as in the method disclosed in Japanese Patent Publication No. 54510 and Japanese Unexamined Patent Publication No. 58-128246, C.
It is not necessary to remove impurities such as binders contained in Si1. Since it is not necessary to pay close attention to prevent mold sand from getting mixed with mold sand, molding sand can be recovered efficiently and in a small number of times. Inorganic binders such as Nai 1~ can also be effectively reused, and since the amount of inorganic binders contained in shell sand is greatly reduced, they can be recovered: mold sand and The light added to each shell sand when reusing it! l
The amount of binder and organic binder added can be reduced,
In addition, the energy consumed in the process of roasting and regenerating shell sand can be reduced, and as a result, the regeneration costs of green mold sand and shell sand can be significantly reduced. One detailed feature of the method of the present invention is that in the process of recovering foundry sand of a size smaller than a predetermined size from a used mold, the mold is collapsed using a cracking frame or the like, and then crushed. , sieving

[By doing this, the molding sand is under the specified method 1,
In other words, the sieved lumpy foundry sand is made into a single grain or a nearly solid state, and the sieved lumpy foundry sand is further crushed to become a single grain or a state close to this. This process aims to increase the recovery rate of the foundry sand, and also separates it into magnetic sand and non-magnetic sand by magnetic separation, that is, green Sunagawa base sand and base sand for SIJ and RU sand. separation efficiency is improved. In this case, the predetermined dimensions are lQmn+,
In particular, 5w1Ill is preferable. According to another detailed feature of the method of the present invention, the recovered foundry sand is separated into magnetized sand and non-magnetized sand by magnetic separation prior to or after this step. Ferromagnetic substances such as iron pieces and molten metal in the recycled foundry sand or recovered green molding sand are removed by auxiliary magnetic separation, resulting in a relatively large amount of ferromagnetic substances mixed into the raw sand for green molding sand. Due to the reader,
Problems such as poor casting surface, insertion, and deterioration of mold disintegration are avoided. In this case, '#i auxiliary, F41
In order to improve the efficiency of the V41 selection (main magnetic selection), which is carried out to separate foundry sand into VII-attached sand and non-magnetic sand, the above-mentioned auxiliary selection is carried out. It is preferable that the i selection is preceded by the main selection by 4 x't lines. In addition, in order to prevent magnetic sand from being removed as ferromagnetic impurities in the auxiliary magnetic separation, the strength of the magnetic field for the auxiliary magnetic separation is set to be weaker than that of the main magnetic separation. For example, the strength of the magnetic field for auxiliary magnetic separation is preferably 1000 to 4000 Gauss, particularly 1500 to 4000 Gauss.
It is set at 3000 Gauss, and the strength of the magnetic field for this magnetic selection is 16
000-=27000 Gauss, especially 18000-230
Preferably, it is set to 0.00 Gauss. EXAMPLES The present invention will now be described in detail with reference to examples with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a foundry sand separation and recovery system suitable for use in carrying out the method according to the present invention. In the figure, 1 indicates a green mold, a shell mold, and J: a crusher for crushing a lumpy mixed sand 2 containing green mold sand and shell sand collected from different used molds. The crusher 1 is a rotary crusher screen in the illustrated embodiment, and has a cylindrical screen 4 of a predetermined mesh l and a cylindrical body 5, which are arranged concentrically with respect to the axis 3, and which are not shown in the figures. It is designed to be rotated around axis 3 by the actuator. The mixed sand 2 is introduced from one end into the screen 4 through the hopper 6, and by colliding with each other in the screen, relatively large aggregates are crushed into single grains or relatively small aggregates, and are crushed to a predetermined size. The pulverized mixed sand 7 passes through the screen and moves into the cylindrical body 5, and falls onto the belt conveyor 8 from one end of the cylindrical body. Relatively large lumps remaining in the screen 4 are recycled to the hopper 6 or roasted (
39). Fall onto the belt conveyor 8 and 1. : The mixed sand 7 is conveyed to the right in the figure by the belt conveyor, and guided through the hopper 9 to the sieving device 10. The sieving device 10 is a vibrating screen in the illustrated embodiment, and is supported by a frame 12 via a spring 11 and has a substantially coat-shaped body 13 stretched over the upper end of the body. Predetermined mesh screen 14
Although it is not shown in the figure, the main body and screen are
It has an actuator that vibrates in the L-FZj direction and in the left and right directions in the figure. The lumpy mixed sand 15 contained in the mixed sand 7 and sieved by the sieving device 10 falls onto the belt conveyor 16 from the right end of the screen 14 in the figure.
The foundry sand is discharged from the separation and recovery system by the belt conveyor or recycled to the hopper 6. A belt conveyor 17 is provided below the sieving device 10, and the mixed sand 18 of a predetermined method or less that has passed through the screen 14 moves downward within the main body 13 and is transferred to the belt conveyor 17.
It falls upward and is conveyed to the right in the figure by the belt conveyor. An auxiliary magnetic separator 19 is arranged above the downstream end of the belt conveyor 17. In the illustrated embodiment, the auxiliary magnetic separator 19 is an overband magnet, and includes four pulleys 20 provided at the four vertices of an isosceles trapezoid, a belt 21 wound around these pulleys, and a belt 21 wound around the pulleys. The belt 21 is driven in the direction of the arrow by an actuator not shown in the figure. It has become. Ferromagnetic substances such as iron pieces contained in the mixed sand 18 conveyed to the downstream end of the belt conveyor 17 and discharged into the chute 23 are attracted by the attractive force of the magnet 22 and adhere to the surface of the belt 21. The ferromagnetic material is conveyed to the right side in the figure by the belt T-21, and at the right end of the auxiliary magnetic separator 19 in the figure, the gravitational force acting on the ferromagnetic material exceeds the attraction force by the magnet 22. passes through shoe I.25 and reaches belt conveyor 2.
6. Fall upwards. The ferromagnetic material 24 that has fallen onto the belt conveyor 26 is discharged from the foundry sand separation and recovery system by the belt. A magnetic separator 27 is installed on the T side of the downstream end of the belt conveyor 18.
is located. Mixed sand 28 discharged from the belt conveyor 18 and from which ferromagnetic substances have been removed by the auxiliary magnetic separator 19
is introduced into the magnetic separator 27 via the chute 23. Does the magnetic separator 27 create an internal magnetic field stronger than the magnetic field created near the downstream end of the belt conveyor 18 by the magnets 22? 6, so that the mixed sand 28 introduced therein is continuously separated into ff1n sand 29 and non-magnetic sand 30. The magnetic sand 29 and non-magnetic sand 30 separated by the magnetic separation 127 fall onto the belt conveyors 31 and 32, respectively, and are transported into the I1 sand storage tank 33 and the non-magnetic sand storage tank 34 by the respective bell conveyors. and recovered as raw Sunagawa sand and shell Sunagawa sand, respectively. The LC magnetic sand 29 collected in the tank 33 is taken out from the tank 33 as needed by a screen feeder 36 which is rotationally driven by a motor 35, and is used for green mold formation. In addition, non-IT! was recovered in the tank 34! The screw feeder 3 is rotated by a mortar 37.
8, the chute 39a is roasted in the roasting furnace 39 as necessary.
The denatured organic caking material adhering to the surface of the sand grains is removed by being roasted in the roasting furnace.
The non-1i1 sand 40 treated in this way is guided into a non-magnetic sand storage tank 41, and is further taken out from the tank 41 as necessary by a screw feeder 43 which is rotationally driven by a motor 42, and is used as base sand for shell sand. ) The molding sand is coated with I-Nol resin and used to form a mold. The method of the present invention, which is carried out using the molding sand separation and recovery system thus constructed, is carried out as follows. First, mixed sand 2 recovered from a used mold consisting of a green mold and a shell mold is guided through a hopper 6 into a crusher 1, and the mixed sand 7 crushed by the crusher is passed through a belt conveyor 8 and a hopper 9. The sieving device removes the lumpy mixed sand 15, and the mixed sand 18 of a predetermined 51 method or less is led to the downstream end by the belt conveyor 17, and the mixed sand 18 is removed by the auxiliary magnetic separator Ia 19. An auxiliary i-selection is performed to remove ferromagnetic materials 24 such as iron pieces contained in the sand, and the mixed sand 28 from which the ferromagnetic materials have been removed is led to a magnetic separator 27, where the magnetic sand 29 is removed. The sand 30 is separated from the non-la deposited sand 30, and is transferred to tanks 33 and 34 by belt conveyors 31 and 32, respectively, where it is recovered as green Sunagawa original sand and raw sand for sanding sand. The magnetic sand 30 is transferred from a tank 34 to a roasting furnace 39, where it undergoes a regeneration process to remove the organic binder. In the method of the present invention, the auxiliary magnetic separator 19 performs the auxiliary magnetic separation as shown by the phantom line in FIG.
Auxiliary magnetic separator 19, sea L-1 to 25, belt conveyor 2
6 is placed on the downstream end side of the belt conveyor 31, auxiliary magnetic separation is performed on the magnetic sand 29 (or the auxiliary magnetic separation may be omitted). Next, a concrete example of the separation and recovery method of the present invention carried out using the system shown in Fig. 1 will be explained. The mixed sand 2 recovered from the mold consisting of a shell mold is guided into the crusher t-1 and pulverized, and the thus pulverized mixed sand 7 is passed through the belt conveyor 8 and the chute 9 through the openings of the sieving device 10. Diameter set to 5IllllIl 1
= Guided onto the screen 14 and passed through the sieving device 10 to a diameter of 51
! The mixed sand 18, which has been sieved into single grains of 1 m or less or close to grain size, is subjected to auxiliary magnetic separation 1j by a belt conveyor 17!
t19, and the ferromagnetic material 24 such as a piece of iron is guided downward by the auxiliary magnetic separator 19 in which the strength of the It field near the downstream end of the belt conveyor 17 is set to 1500 to 3000 Gauss.
The mixed sand (first selection sand) 28 from which ferromagnetic substances were removed was subjected to a rotating matrix type dry high gradient magnetic separation process with an internal magnetic field strength set to 20,000 gauss [27 for 1!1 selection sand]. The sand was separated into sand 29 and non-magnetic sand 30, and each sand was collected into tanks 33 and 34. Grain anti-index, active clay content, egross, fixed carbon content, and volatile content were measured for the thus recovered magnetic sand, non-magnetic sand, and magnetic separation source sand. The results are shown in Table 1. In Table 1, Igros refers to magnetic reduction sand, etc., heated to 1000℃ for 1 hour.
The amount of volatile matter is the amount of carbon lost when magnetic reduction sand is heated to 950℃ for 2 minutes, and the amount of fixed carbon is the amount of carbon remaining after the above treatment. means. In addition, for the three types of sand mentioned above, add 2 parts of water to 100 parts by weight of sand so that the compactability value becomes 40 to 55%.
．． 5 to 3.03 tfi parts were added and kneaded for 5 minutes using a Simpson type kneader 1 (manufactured by George Futushito Ichirei), and the wet compressive strength of the green sand was measured. The results are shown in Table 2 and Figure 2 below.
17 2.8 43 Magnetic sand 1.37 2.7 40 Non-magnetic sand 0,72 2,4 50 In addition, in order to confirm the suitability of the three types of sand mentioned above when reusing them as shell sand, Three types of sand were placed in a fluidized bed IJ.
! After roasting at 800° C. for 30 minutes in a roasting furnace, a roasting regeneration process was performed to remove fine powder using a fluidized bed type fine powder removal device (yield: 96%). 3 where such roasting and regeneration treatment was performed
Regarding the types, 2.5 parts of phenol resin and 0.375 parts of power law methylenetetramine per 100 parts by weight of sand.
ff1MtW. 0.1 part by weight of calcium stearate was added, shell sand was formed using a Speed Muller mixer, and the shell sand was used to measure bending strength based on JISM rating 6910. The results are shown in Table 3 and FIG. 2 below. Table 3 1L” transverse bending 1ffl (k (110?) magnetic separation source sand 21
．． 1 Magnetized sand 17.7 Non-magnetic sand 38.9 From Tables 1 to 3 and Figure 2 listed in 1, it can be seen that the Ii type sand has a large proportion of green sand, and the non-magnetic sand has a large proportion of shell sand, respectively. It is found that it is suitable for reuse as green mold sand and shell sand. Therefore, by using the Wik8 sand separated by magnetic separation as the base sand for green molding sand and the non-magnetic sand as the shell Sunagawa base sand, the used foundry sand that is not separated and recovered by magnetic separation can be used as it is for green molding. Compared to supplying Sunagawa base sand or Shell Sunagawa base sand to the regeneration/mixing system, the amount of additives such as inorganic binders can be reduced for green mold sand, and Shell Sunagawa base sand It can be seen that for sand, the energy required for torrefaction can be reduced, and the amount of additives such as organic binders can be reduced. Figure 3 shows the three types of sands mentioned above, namely, magnetically separable sand, magnetic sand, and non-magnetic sand, which are required to be roasted and recycled to a state suitable for reuse as recycled shell sand. It is a graph showing the torrefaction energy consumption required for torrefaction of the magnetic separation source sand with the energy consumption ratio being 100%. From this Figure 3, it can be seen that the energy consumption of magnetic and coated sand is higher than that of magnetically selected sand, and the energy consumption of non-magnetized sand is less than that of magnetically selected sand. It can be seen that the sand is suitable for reuse as base sand for sealing sand. It is presumed that the above results were obtained because the magnetic sand contained relatively large amounts of water and bentonite. Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and it is understood that various embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a foundry sand separation and recovery system suitable for use in carrying out the method according to the present invention, and Fig. 2 shows green sand for magnetic reduction sand, magnetic sand, and non-Ii sand. A tag graph showing the wet compressive strength and shell sand resistance strength. Figure 3 shows the roasting of magnetically selected original sand, magnetic sand, and non-magnetic sand to a state suitable for reuse as shell Sunagawa original sand. It is an illustrative graph showing the energy consumption rate of 1 energy required to carry out the regeneration treatment, assuming that the energy consumption of the magnetic separation source sand is 100%. 1... Kurare v-, 2... Mixed sand, 3... Axis, 4... Screen, 5... Cylindrical body, 6... Hopper, 7... Mixed sand, 8...・Belt conveyor, 9...
・Hopper, 10... Decoration, 11... Spring, 12.
...Frame, 13...Main body, 14...Screen, 15...Lumpy mixed sand, 16.17...Belt conveyor, 18...Mixed sand, 19...Auxiliary magnetic separator, 2
0...Pulley, 21...Belt, 22...Magnet,
23...Hopper, 24...Ferromagnetic material, 25...Hopper, 26...Bell 1~: Conveyor, 27...Magnetic sorting machine. 28...li'l sand, 29...magnetic sand,;30...
・Non-I! Wakasuna. 31.32...Belt:]Nbare, C33...Ni
l Sand storage tank, 34...Non-magnetic sand storage tank, 35
...Tanabata,, :'<a...Screw feeder,
37...Motor. 38...Screw feeder, 39...Roasting path, 3
9a... Sheet 1-sheet, 7IO... Non-magnetic sand after roasting, 41... Non! 11 Sand storage tank, 42...L-
TA, 43...Slurry 1 - Fieg Patent Applicant: Toyota Automobile Co., Ltd., 1st Representative, Patent Attorney: Masatake Akashi (Method) Procedural Amendment September 27, 1980 Commissioner of the Patent Office Manabu Shiga 1 , Incident Display 1982 Patent Application No. 099561 2
, Name of the invention Method for separation and recovery of used foundry sand 3 Relationship with the case of the person making the amendment Patent applicant address 1 Toyota-cho, Toyota City, Aichi Prefecture Name (320) Toyota Motor Corporation 4 Address of agent @104 1-5-19 Shinkawa, Chuo-ku, Tokyo August 8, 1982 (Shipped on August 28, 1980) 6. Subject of amendment Drawings

Claims (1)

[Claims] Foundry sand of a specified size or less is recovered from a used mold consisting of a green mold and a shell mold, and then it is processed by magnetic separation.
A method for recovering used foundry sand by separating it into sand and sand, recovering the magnetic sand to a green mold sand recovery system, and recovering the non-liiIM sand to a shell sand recovery system.