JPS61273238A - Method for separating and recovering - Google Patents

Abstract

PURPOSE:To recover and reuse nonmagnetic shell sand and to reduce the cost of the sand by subjecting the used molding sand in which green sand and shell sand are mixed to a magnetic sepn. treatment, heating and roasting the nonmagnetic sand in a specific temp. range and magnetizing the residual green sand then separating again the sand by the magnetic sepn. treatment. CONSTITUTION:The used molding sand 2 in which the green sand and the shell sand are mixed is passed through a screening device 9 by which large-sized solid matter is removed. The minus sieve 2 thereof is fed to an auxiliary magnetic separator 16 by which cast iron is removed from the sand. The sand is then separated to the magnetized sand 25 and the non-magnetized sand 26 by the 1st magnetic separator 24. The sand 26 is put into a roasting furnace and is heated to 500-1,000 deg.C to intensify the magnetism of the bentonite, coal powder, etc. contained in the residual green sand. The sand is separated again by the 2nd magnetic separator 36 of about 18,000-23,000 gauss. The reseparated nonmagnetic sand 39 is mostly the shell sand and is reused. The separated magnetic sands 25, 38 are mixed with the green sand after the sepn. of the pulverous powder and are reused.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for separating and recovering used foundry sand, and more specifically, from a used mold having green sand and shell sand, foundry sand suitable for green sand is collected. The present invention relates to a method for separating and recovering used foundry sand into molding sand suitable for shell sand and shell sand.

[Conventional technology]

The foundry sand that forms the mold has conventionally been repeatedly recycled and used in consideration of economical efficiency and resource conservation.

By the way, a mold used to manufacture a casting having a cavity, such as a cylinder block for an internal combustion engine, consists of a main mold (green mold) that forms the main part of the casting, and a core (shell core) that forms the cavity. ).

In general, the green mold is made of silica sand (SiLJ2) with added viscosity, an inorganic binder such as bentonite, a small amount of water, coal powder, etc., and the shell core is made of silica sand with an organic binder such as phenolic resin added. Formed of shell sand with added binder. When recovering foundry sand from used molds made of green sand and shell sand, the types of green sand and shell sand, the type of binder added to them, and the appearance etc. are different. If shell sand mixes with the other sand, problems such as an increase in the amount of binder added, removal of excess components, recycling processing cost, and increase in costs will occur, so green sand and shell sand should be kept as much as possible to prevent them from mixing with each other. It is desirable to separate and collect.

However, after casting, the mold collapses due to the binding agent losing its binding strength due to the thermal influence of the molten metal, and also due to the mechanical force applied to the mold from which the casting is taken out, and even during transportation to the next process. , green sand and shell sand mix with each other. For this reason, it is extremely difficult to reliably separate and recover green sand and shell sand, and the mixing ratio of green sand and shell sand varies greatly depending on casting conditions, casting equipment, etc.

One method for dealing with this problem is to use sieving. This is applied to mixed sand of lumpy green sand and shell sand. Green sand with inorganic binder added as a binder tends to crumble easily, and organic binder added as binder with green sand tends to crumble. This method takes advantage of the property of shell sand that it does not easily crumble, and uses a sieve to separate mixed sand of green sand and shell sand into green sand and shell sand. However, with this method, it is not possible to separate the mixed sand, which is recovered in the form of single grains or nearly so after the mold collapses, into green sand and shell sand with high purity.

In addition, as another method to deal with such problems,
The methods described in Japanese Patent Application Laid-open No. 5-4510, Japanese Patent Application Laid-Open No. 58-128246, and Japanese Patent Application Laid-Open No. 58-128248 are known. In either of these methods, used foundry sand is subjected to magnetic separation to remove magnetic bones as impurities, and the non-magnetic portion is recycled and reused as shell sand, or recycled After this, magnetic separation is performed to remove the magnetized bone as impurities, and the non-magnetized portion is reused.

[Problem that the invention seeks to solve]

However, according to the above method, there is a problem in that if an attempt is made to improve the quality of recycled sand, the recovery rate of recycled sand, that is, the yield rate, decreases accordingly.

Furthermore, although these methods yield relatively pure silica sand that can be reused as aggregate for foundry sand, it is difficult to separate and recover green sand and shell sand from used molds made of green sand and shell sand. The problem is that it is not possible.

Therefore, in order to solve this problem, the applicant has previously conducted various experiments and research, and has developed compositions and materials suitable for magnetic sand and non-magnetic sand to be used as green sand and shell sand, respectively. As a result, we separated foundry sand of a specified size or less into magnetic sand and non-magnetic sand by magnetic separation, and divided these into a green sand recovery system and a shell sand recovery system. An application has been filed for a method for separating and recovering used foundry sand.

Although this application made it possible to separate and recover green sand and shell sand with considerable precision, it was unavoidable that about 10 to 20 percent of the green sand would be mixed into the non-magnetic sand.

For this reason, it has been desired to develop a method for separating and recovering green sand and shell sand with even greater precision.

[Means for solving problems]

According to the present invention, the above problem is solved by the method for separating and recovering used foundry sand described below.

That is, the present invention recovers molding sand of a predetermined size or less from a used mold containing green sand and shell sand, and performs a first magnetic separation process to collect the molding sand into first magnetic sand and first magnetic sand. The first magnetic sand obtained is collected into a green sand recovery system, and the first non-magnetic sand is heated at 500°C to 1000°C.
By roasting at a temperature of The method is characterized in that the proportion of green sand mixed in the first non-magnetic sand is reduced by separating it into non-magnetic sand, and this second non-magnetic sand is collected into a shell sand recovery system. There is.

In the present invention, in order to recover molding sand of a predetermined size or less from a used mold, the mold is collapsed using a conventional barrack or the like, and then the sand is crushed and sieved. Thereby, the foundry sand is brought into a state of a predetermined size or less, that is, into a single grain state or a state close to it.

In the present invention, both the first magnetic separation process and the second magnetic separation process can be performed using a dry high gradient magnetic separator or the like, and the strength of the magnetic field is 16,000 to 27,000 Gauss.
Preferably, it is set at 18,000 to 23,000 Gauss.

Furthermore, it is desirable to supplementally remove castings, iron powder, etc. from the treated sand prior to or after the first and second magnetic separation treatments. This auxiliary magnetic selection includes
A conventional magnetic separator can be used. At this time, in order to prevent the magnetic sand from being removed as ferromagnetic impurities by the auxiliary magnetic separation, the strength of the magnetic field for the auxiliary magnetic separation is equal to the magnetic field of the first and second magnetic separation processes described above. It is preferable to set it weaker than strong. For example, the strength of the auxiliary magnetic field is 1000-4000 Gauss, preferably 1500 Gauss.
It is desirable to set it to ~3000 Gauss.

In the present invention, the temperature at which the non-magnetic sand is roasted is 500°C.
-1000 degreeC is desirable, and 800 degreeC - 1000 degreeC is more desirable. At this time, the roasting time is preferably 0.5 to 2 hours, more preferably about 1 hour. At this time, as the roasting device, for example, a "foundry sand regeneration device" (Utility Model Publication No. 58-23467) proposed by the applicant of the present invention can be used.

[Effect]

According to the method for separating and recovering used foundry sand of the present invention, the first magnetic separation treatment separates the sand into first magnetic sand and first non-magnetic sand. This first magnetic sand contains an inorganic binder such as bentonite, and is recovered by a green sand recovery system and reused as green sand by supplementing the missing bentonite and the like. Depending on the strength of the magnetic field in the first magnetic separation process and the ratio of green sand to shell sand in the original mold, the first non-magnetic sand separated by the first magnetic separation process may be mixed with shell sand. Approximately 10 to 20% of raw sand is mixed in. In order to further separate this green sand and shell sand, the first non-magnetic sand separated by the first magnetic separation process is roasted at 500°C to 1000°C. As a result, green sand becomes more magnetic due to its added components such as bentonite and coal powder, and the second magnetic separation process can capture what was not captured in the first magnetic separation process. become. Therefore, by performing the second magnetic separation process after roasting, the first non-magnetic sand obtained in the first magnetic separation process is again divided into the second magnetic sand and the second non-magnetic sand. can be separated into The second non-magnetic sand obtained as a result is collected in the shell sand collection system, and the second
The magnetic sand can be appropriately treated as silica sand enriched with green sand constituents.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Here, FIG. 1 is a schematic configuration diagram showing a foundry sand separation and recovery system used for carrying out the present invention.

In the figure, 1 is a crusher that crushes mixed sand 2 in the form of lumps recovered from a used mold made of green sand and shell sand. This crusher 1 is a rotary crusher screen in the figure, and has a cylindrical screen 4 of a predetermined mesh and a cylindrical body 5 arranged concentrically with respect to an axis 3, and is rotationally driven around the axis 3 by an actuator (not shown). Ru.

The mixed sand 2 is introduced from one end into a screen 4 through a hopper 6, and collides with each other within this screen 4, thereby crushing relatively large aggregates into single grains or relatively small aggregates. The mixed sand 2 pulverized to a predetermined size or less passes through the screen 4 and moves into the cylindrical body 5, and falls onto the belt conveyor 7 from one end of the cylindrical body 5.

The relatively large lumps remaining on the screen 4 are recycled to the hopper 6 or sent to the roasting furnace 31 (described later).
directly injected into The mixed sand that has fallen onto the belt conveyor 7 is conveyed to the left in the figure by the belt conveyor 7, and guided to the sieving device 9 via the hopper 8.

This sieving device 9 is a vibrating screen in the figure, is supported by a frame 1 via a spring 10, and has a main body 12 that is substantially funnel-shaped, and a predetermined screen stretched over the upper end of the main body 12. Metush screen 1
3, and an actuator (not shown) that vibrates the main body 12 and the screen 13 in the vertical and horizontal directions. The lumpy mixed sand 2 contained in the mixed sand 2 and sieved by the sieving device 9 falls onto the belt conveyor 14 from the right end of the screen 13 in the figure. The fallen lumpy mixed sand 2 is discharged from the molding sand separation and recovery system or recycled to the hopper 6. A belt conveyor 15 is provided below the sieve device 9, and a screen 13
The mixed sand 2 of a predetermined size or less that has passed through moves downward within the main body 12 and falls onto a belt conveyor 15, and is conveyed by this belt conveyor 15 to the right in the figure.

An auxiliary magnetic separator 16 is disposed above the downstream end of the belt conveyor 15. The auxiliary magnetic separator 16 is an overband magnet in the figure. The auxiliary magnetic separator 16 consists of four pulleys 17 provided at the four vertices of the isosceles trapezoid, a belt 18 wound around these pulleys 17, and a portion of the belt 18 forming the base of the isosceles trapezoid. The belt 18 has a magnet 19 provided inside, and the belt 18 is driven in the direction of the arrow by an actuator (not shown).

By this auxiliary magnetic separator 16, the mixed sand 2 conveyed to the downstream end by the belt conveyor 15 and guided to the chute 20 has ferromagnetic materials such as iron pieces contained therein removed. That is, the ferromagnetic material is attracted by the attractive force of the magnet 19 and adheres to the surface of the belt 18, is transported by the belt 18 to the right in the figure, and is moved by the magnet 19 at the right end of the auxiliary magnetic separator 16 in the figure. As the gravity acting on the ferromagnetic material exceeds the attraction force, the material falls through the chute 21 onto the belt conveyor 22. Belt conveyor 2
The ferromagnetic material 23 that fell onto the belt conveyor 2
2, the foundry sand is discharged out of the separation and recovery system.

A first magnetic separator 24 is arranged below the downstream end of the belt conveyor 15. The mixed sand 2 conveyed by the belt conveyor 15 and from which the ferromagnetic substances have been removed by the auxiliary magnetic separator 16 is introduced into the first magnetic separator 24 via the chute 20 . The first magnetic separator 24 is configured to be able to generate a magnetic field inside thereof that is stronger than the magnetic field generated near the downstream end of the belt conveyor 15 by the magnets 19 of the auxiliary magnetic separator 16 . With this first magnetic separator 24,
The mixed sand 2 is continuously separated into first magnetic sand 25 and first non-magnetic sand 26 . The first magnetic sand 25 and the first non-magnetic sand 26 separated by the first magnetic separator 24 fall onto a belt conveyor 27 and a belt conveyor 28, respectively. Then, the first magnetic sand 25 is transferred to the belt conveyor 2.
7 into the magnetic sand storage tank 29 and recovered as raw sand for green sand. On the other hand, the first non-magnetic sand 26 is carried into the roasting furnace 31 via the belt conveyor 28 and the packet elevator 30.

The magnetic sand 25 collected in the tank 29 is taken out from the tank 29 as needed by a screw feeder 33 that is rotationally driven by a motor 32, and is used for forming a green mold. Further, the first non-magnetic sand 26 guided to the roasting furnace 31 via the packet elevator 30 is
By roasting at ℃~1000℃ for 0.5~2 hours, the altered organic binder adhering to the surface of the sand grains is removed and mixed into the first non-magnetic sand 26. The magnetization of green sand components is promoted.

The roasted first non-magnetic sand 26 is transferred to the belt conveyor 3 through a chute 34 attached to the lower part of the roasting furnace 31.
5 falls on top. This first non-magnetic sand 26 is conveyed on the belt conveyor 35 to the left in the figure.

A second magnetic separator 36 is arranged below the downstream end of the belt conveyor 35. The first non-magnetic sand 26 conveyed by the belt conveyor 35 is introduced into the second magnetic separator 36 via a chute 37. The second magnetic separator 36 is
Similar to the first magnetic separator 24, the magnet 19 of the auxiliary magnetic separator 16
It is constructed so that it can create a stronger magnetic field inside than the strength of the magnetic field created by. This second magnetic separator 36
Accordingly, the first non-magnetic sand 26 is connected to the second magnetic sand 38 and the second
is continuously separated into non-magnetic sand 39. Second magnetic separator 3
The second magnetic sand 38 and the second non-magnetic sand 39 separated by 6 fall onto the belt conveyor 40 and the belt conveyor 41, respectively. Then, the second magnetic sand 38
is guided into a magnetic sand storage tank (not shown) by a belt conveyor 40 and recovered as raw sand for green sand. on the other hand,
The second non-magnetic sand 39 is guided by a belt conveyor 41 to a non-magnetic sand storage tank (not shown), and is recovered as source sand for shell sand.

Next, a specific operation using the above separation and recovery system will be explained.

First, mixed sand 2 was recovered from a mold made of raw sand and shell sand used for casting cylinder blocks for internal combustion engines.
is put into the hopper 6. The mixed sand 2 is then introduced into the crusher 1 and crushed there. The mixed sand 2 pulverized to a predetermined size falls onto the belt conveyor 7,
It is conveyed to the left in the figure, thrown into the hopper 8, and sieved by the sieving device 9.
Guided within. By this sieving device 9, the mixed sand 2 is pulverized by a screen 13 into a size smaller than a predetermined size, for example, the size of a single grain, and falls onto a belt conveyor 15. In addition,
The lump-like mixed sand 2 that has not been crushed is guided from the sieving device 9 onto the belt conveyor 14, and then thrown into the hopper 6 again.

The mixed sand 2 that has fallen onto the belt conveyor 15 is conveyed to the right in the figure and is thrown into the hopper 20 from the right end. At this time, the ferromagnetic material 23 such as a piece of iron is removed by the auxiliary magnetic separator 16 whose magnetic field strength is set to 1500 to 3000 Gauss.

The mixed sand 2 put into the hopper 20 is guided through a rotating machine (IJ x type dry type high gradient magnetic separator), which is a first magnetic separator 24 whose internal magnetic field strength is set to 20,000 Gauss.
Here, it is separated into first magnetic sand 25 and first non-magnetic sand 26. Then, the first magnetic sand 25 is transferred to a belt conveyor 27.
The sand is guided into the magnetic sand storage tank 29 and used as source sand for green sand as needed.

On the other hand, the first non-magnetic sand 26 is charged into a roasting furnace 31 via a belt conveyor 28 and a packet elevator 30, where it is roasted at 800±10° C. for one hour. The roasted first non-magnetic sand 26 is guided by a belt conveyor 35 into a second magnetic separator 36 set to the same magnetic field strength of 20,000 gauss as the first magnetic separator [24], and is again passed through the second magnetic separator 36. 2
The magnetic sand 38 and the second non-magnetic sand 39 are separated by a belt conveyor 40.41, and the second magnetic sand 36 is used as raw sand for green sand, and the second non-magnetic sand 39 is used as a shell sand river. It is collected separately as raw sand.

According to this embodiment, the green sand component that was included in the first non-magnetic sand 26 by 10% to 20% becomes more magnetic during the roasting process, so that it can be separated again by the magnetic separation process. , green sand and shell sand can be separated with much higher precision than conventional methods.

The following experiment was conducted to confirm that the magnetism of the green sand component increases due to roasting, making it easier to be captured and separated from the shell sand component by magnetic separation processing.

(Experiment example) Gunma bentonite 9 added to 100 parts by weight of Australian natural silica sand
Parts by weight, 4 parts by weight of coal powder (high-grade coal powder manufactured by Mikawa Mining Co., Ltd.) and 4 parts by weight of water were added, and the mixture was kneaded in a Simpson mix muller to obtain green sand for testing.

This test green sand was divided into two equal parts, and the half was dried for 2 hours in a drying oven set at 1) 0±2°C, and then cooled to room temperature in a desiccator to obtain Sample No. 1. The other half is 800±10
After performing roasting treatment for 1 hour in a furnace set at ℃, it was cooled to room temperature in a desiccator, and this was designated as sample 1) h2.

Magnetic measurements were carried out for the above two types of sand using a vibrating sample magnetometer (VSM-33-15 manufactured by Toei Kogyo), and a high magnetic force magnetic separator (62A RMEO7・SA manufactured by Mitsubishi Steel Corporation) was used.
) was used to perform magnetic separation treatment at a magnetic field strength equivalent to about 20,000 Gauss, and the percentage of magnetized bone was examined. The results are shown in Table 1.

Table 1: However, the unit of magnetic properties is p mu / g, and the unit of magnetic bone is %.

From Table 1, by applying roasting treatment to green sand, the magnetic properties are approximately 7.
It can be seen that the magnetic properties are significantly improved by about 9 times in terms of magnetic adhesion. As a result, by roasting the raw sand,
It can be seen that green sand components can be efficiently separated and recovered using a magnetic separator.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes various embodiments within the scope of the claims.

For example, in the example, auxiliary magnetic selection was performed on the sieved mixed sand, but this auxiliary magnetic selection may be performed only on the first magnetic sand after the first magnetic selection. .

〔Effect of the invention〕

As described above, the method for separating and recovering used foundry sand of the present invention provides the following effects.

(b) By using magnetic separation treatment and roasting process, green sand and shell sand can be separated and recovered with high accuracy. In particular, since the roasting process can impart magnetism to the raw sand components mixed in the first non-magnetic sand, the separation and recovery efficiency of the non-magnetic sand can be greatly improved by performing magnetic separation again. can.

(b) It is not necessary to remove impurities such as binders adhering to the surface of sand grains prior to magnetic separation, or to pay close attention to prevent green sand from getting mixed into shell sand, making the recovery of molding sand more efficient. It can be implemented easily and inexpensively.

(c) Since the inorganic binder attached to the surface of green sand can be effectively used, the amount of inorganic binder added for reuse can be reduced, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a foundry sand separation and recovery system used in the implementation of the present invention. 2.-Co.Mixed sand 9--Sieving device 16--Auxiliary magnetic separator 24--First magnetic separator 25--First Magnetic sand 26 - - - - - First non-magnetic sand 31 - - Roasting furnace 36 - - Second magnetic separator

Claims (1)

[Claims] (1) Collect molding sand of a predetermined size or less from a used mold containing green sand and shell sand, and process this molding sand into first magnetic sand and first non-magnetic sand through a first magnetic separation process. The first non-magnetic sand is collected into a green sand recovery system, and the first non-magnetic sand is roasted at 500°C to 1000°C. Magnetism is imparted to the raw sand mixed in the magnetic sand, and after roasting, it is separated into the second magnetic sand and the second non-magnetic sand through a second magnetic separation process. A method for separating and recovering used foundry sand, which comprises reducing the proportion of green sand mixed in non-magnetic sand and collecting the second non-magnetic sand into a shell sand recovery system.