JP2017148725A - Reutilization method for cast waste and manufacturing method for back-filling hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a high-performance back-filling material by utilizing cast wastes.SOLUTION: A reutilization method for cast wastes comprises a dust collection process 17 of collecting dust floated when sand serving as a cast raw material is mixed with bentonite, a classification process 18 of classifying the dust collected in the dust collection process 17 into a plurality of stages of grain-size divisions, and a reutilization process of reutilizing powder as a back-filling material component, the powder contained in a smallest one of grain-size divisions classified in the classification process 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for reusing waste generated in a casting process and to a method for producing a hydraulic composition using the waste.

  Bentonite is widely used for tunnel backfill materials, void fillers, void fillers, fluidized soil, molds and the like.

  On the other hand, the mold is created by solidifying the mold sand. Molten iron (molten metal) is poured into the mold, the mold is released from the mold, and the casting is taken out, thereby producing the casting. In addition, the separated mold is regenerated and reused as mold sand.

  Patent Literature 1 classifies dust generated during reprocessing of a mold (waste sand) separated into two stages of particle size classification, and uses powder contained in a large particle size classification as an admixture for blended cement mortar. It is disclosed that a powder contained in a small particle size category is used as mud clay.

  Patent Document 2 discloses a method in which casting dust, cement, water, and water glass are mixed and these mixtures are produced as gap fillers.

JP-A-8-206776 Japanese Patent No. 4955938

  However, in the technique described in Patent Document 1, since the bentonite contained in the mold is denatured by heating the mold in the pouring step, the admixture for blended cement mortar produced from the mold (waste sand) and The performance of mud clay is low. Similarly, the gap filler described in Patent Document 2 has low performance due to the influence of heat.

  Therefore, the present invention has been made in view of the above circumstances. The problem to be solved by the present invention is to recycle casting waste to produce a high performance backfill material.

  The main invention for solving the above problems is a dust collection process for collecting dust that floats when mixing sand and bentonite as a raw material of a mold, and a plurality of stages of the dust collected in the dust collection process. A classification step of classifying the particles into a particle size classification, and a reuse step of reusing the powder contained in the smallest particle size classification among the particle size classifications classified by the classification step as a component of the backfilling material. This is a method for reusing casting waste.

  In addition, the main invention for solving the above problems is a dust collection step for collecting dust floating when mixing sand and bentonite as a raw material of the mold, and the dust collected in the dust collection step. A classification step of classifying into a plurality of particle size categories, and a compounding step of blending the powder contained in the smallest particle size category among the particle size categories classified by the classification step with cement. It is a manufacturing method of the hydraulic composition for backfilling materials.

According to the above invention, dust that floats when sand and bentonite as a raw material for the mold are mixed is collected, so that the bentonite contained in the dust is not modified or transformed by heat. Moreover, when the dust is classified, the bentonite content of the powder included in the minimum particle size classification increases.
Therefore, when the powder having the minimum particle size obtained by classification of unheated dust is reused as a component of the back-filling material, a high-performance back-filling material can be provided. For example, even if the blending ratio of cement used for the backfilling material is lower than usual, the backfilling material can be made high in strength.

Preferably, the minimum particle size category is less than 75 μm.
Therefore, since the bentonite content rate of the powder contained in the minimum particle size classification becomes high, a high-performance backfilling material can be provided.

Preferably, the reuse method adheres to the surface of the casting by injecting a blast material into the casting removed from the mold and removing the casting created by casting from the mold. A separation step of separating the residue of the mold, a separation step of separating the blast material from dust settled in the separation step, a recovery step of collecting the powder from which the blast material has been separated in the separation step, A second reuse step of reusing the powder collected in the collection step as a component of a filler used in construction work or civil engineering work, and in the classification step, classification into three stages of particle size classification In the second recycling step, the powder contained in the medium particle size segment among the three particle size categories is also reused as a component of the filler.
The performance of the filler containing the powder included in the medium particle size classification and the powder recovered in the recovery process is high. For example, even if the blending ratio of cement used for the filler is lower than usual, the filler can be made high in strength.

Preferably, the reuse method adheres to the surface of the casting by injecting a blast material into the casting removed from the mold and removing the casting created by casting from the mold. A separation step of separating the residue of the mold, a separation step of separating the blast material from dust settled in the separation step, a recovery step of collecting the powder from which the blast material has been separated in the separation step, A second reuse step of reusing the powder recovered in the recovery step as a component of a filler used for construction work or civil engineering work, and the powder included in the minimum particle size category is also the above In the second reuse step, it is reused as a component of the filler.
The performance of the filler containing the powder included in the smallest particle size classification and the powder recovered in the recovery process is high. For example, even if the blending ratio of cement used for the filler is lower than usual, the filler can be made high in strength.

Preferably, in the classification step, the powder is classified into three stages of particle size categories, and the powder contained in the medium particle size category of the three stages of particle size categories and the powder contained in the largest particle size category. Reuse as a filler component for construction work or civil engineering work.
Therefore, the performance of the filler containing the powder included in the medium particle size category and the powder included in the maximum particle size category is high. For example, even if the blending ratio of cement used for the filler is lower than usual, the filler can be made high in strength.

  According to the present invention, a high-performance backfilling material can be provided.

FIG. 1 is a casting process diagram in a foundry.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are given various technically preferable limitations for carrying out the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples.

1. Collection of Backfill and Filler Components FIG. 1 is a casting process diagram in a foundry. Casting is manufactured at a foundry, and waste (casting waste) generated in the casting process is collected and reused as a component of the backfill material and filler. Therefore, the casting process in the foundry will be described in detail below.

  In the sand treatment process 1, sand (for example, silica sand), a binder (specifically, bentonite), an additive (for example, coal powder, etc.) and water are supplied to the sand treatment machine, and further after the sand recovery process 10 described later. Sand is also supplied to the sand processor, and these are kneaded by the sand processor. Then, the molding sand prepared and kneaded by the sand processing machine is conveyed to the molding machine. Further, surplus mold sand prepared by the sand processor is transported to a sand regenerator and regenerated into sand by the sand regenerator (see sand regeneration step 5).

  In the core sand generation step 2, the binder (resin) and sand are supplied to the core sand generator, and the sand regenerated in the sand regeneration step 5 is also supplied to the core sand generator, and the binder and sand are supplied to the core sand generator. Core sand (resin coated sand) is generated by kneading and heating with a sand generator. And the produced | generated core sand is conveyed to a core molding machine.

In the main mold making process 3, the mold sand kneaded in the sand treatment process 1 is filled into a casting frame by a molding machine and pressed to form a main mold.
In the core molding step 4, the core is molded by pressing the core sand generated in the core sand generating step 2 with a core molding machine. The core glass generated at that time is transported to a sand regenerator and regenerated into sand by the sand regenerator (see sand regeneration step 5).

In the mold matching process (core fitting process) 6, the core is combined in the molded main mold.
In the melting step 7, iron scrap is melted by a melting furnace to produce molten iron.
In the pouring process 8, molten iron is injected into the cavity of the matched main mold. Then, the molten iron is filled in the cavity of the main mold, and the molten iron is cooled, thereby producing a casting.
In the mold releasing process 9, the main mold and the core are crushed by a mold releasing machine, and the casting is taken out. The main mold and core crushed pieces (return sand) are collected (see sand collecting step 10), and the crushed pieces are returned to the sand treatment. The dust floating in the mold separation process 9 is collected by a dust collector and collected (see the dust collection / collection process 15).

  The casting taken out in the mold breaking process 9 is conveyed to a shot blasting machine. Since the residue of the mold adheres to the surface of the casting, the residue is peeled from the casting by spraying the blasting material (iron powder) onto the casting with a shot blasting machine (see the residue peeling step 12). Ships after processing and painting the casting from which the residue has been peeled off. The dust floating in the residue peeling process 12 is collected by a dust collector and collected (see the dust collection / collection process 16). Since the sprayed blast material and the separated residue (powder) settle inside the shot blasting machine, they are conveyed to a magnetic separation separator.

  In the separation step 13, the blast material is separated from the residue sent to the magnetic separation separator by the magnetic force of the magnetic separation separator. The sorted blast material is conveyed to a shot blasting machine and reused in the residue peeling process 12. On the other hand, the separated residue is recovered (see the recovery step 14), and the recovered residue (hereinafter referred to as powder d) is reused as a component of the filler. The filler will be described in detail later.

  When sand and binder (bentonite) etc. are supplied to the sand processing machine used in the sand treatment step 1, sand and binder etc. float as dust. The suspended dust (sand, bentonite, etc.) is collected by a dust collector (see dust collection step 17). Then, the collected dust is conveyed to a classifier.

  In the classification step 18, the collected dust is classified into a plurality of particle size categories according to the particle size using a classifier, and the classified dust is recovered for each particle size category. Specifically, it is classified into three stages of a large particle size category, a medium particle size category, and a small particle size category. The small particle size category includes powder a having a particle size of less than 75 μm, the medium particle size category includes powder b having a particle size of 75 μm or more and less than 200 μm, and the large particle size category includes powder having a particle size of 200 μm or more. c is included. The threshold value for dividing the small particle size category and the medium particle size category and the threshold value for dividing the medium particle size category and the large particle size category are set by designing, adjusting, and controlling the classifier. Note that the threshold value for dividing the small particle size segment and the medium particle size segment may be set to a value other than 75 μm (for example, 45 μm, 65 μm, 80 μm).

  The classifier used in the classification process 18 is an ultrasonic vibration fluid type screen classifier. It should be noted that other classifiers, for example, vibration screen system, vibration screen system, rotary shifter system, cylindrical stirring screen system or blower shift system screen classifier, forced centrifugal separation system, specific gravity sorting system or gravity inertia separation system wind power A classifier may be used.

  By classifying the dust generated by the sand processor, powders a to c having different bentonite contents can be collected. Specifically, powder a having the highest bentonite content, powder c having the lowest bentonite content, and powder b having a lower bentonite content than powder a and higher than powder c can be collected. . In particular, the powder a of the small particle size group has a higher bentonite content than the dust before classification. The fact that the bentonite contents of the powders a to c are different as described above will be clarified by Example 1 described later.

  Since the powder a in the small particle size group obtained by classification has a high bentonite content, the powder a is used as a component of the shielding back-filling material. The powder a is also used as a component of the filler. Moreover, the powders b and c of the medium particle size group and the large particle size group obtained by classification are also used as components of the filler. Since the powders a to d are obtained from the waste generated in the foundry, the waste can be effectively used.

  The powders a to c are mainly generated from the dust generated in the sand treatment step 1 before the pouring step 8, and contain a lot of unheated bentonite components. Therefore, many bentonites contained in the powders a to c are not thermally denatured or thermally transformed and are good as a coagulant. Therefore, the backfilling material and filler described later using the powders a to c have high performance and high quality. In addition, the sand is separated into heated sand (not affected by heat) and unheated (not affected by heat) in the sand recovery process 10, and is not heated (not affected by heat). No) Only sand may be returned to the sand treatment step 1 as recycled sand. Further, since the reclaimed sand includes heated sand (which is affected by heat), the reclaimed sand may not be returned to the sand treatment fixing 1.

2. Reuse as a component of backfill material Backfill material for shield is used for shield method. In the shield construction method, a shield tunnel is constructed by excavating a face with a shield machine, advancing the shield machine sequentially, and assembling segments at the rear of the shield machine. When the shield machine advances, tail voids (air gaps) are formed outside the segment behind the shield machine, and the tail voids are filled with backfill material. Here, the backfilling material is a mixture of A liquid (main material) and B liquid (coagulant), and A liquid and B liquid are separately passed through the piping etc. to the back of the shield machine and backfilled. Immediately before, liquid A and liquid B are mixed, and the mixture (backfill material) is injected into the tail void.

  In general, the liquid A contains bentonite, but in the present embodiment, the powder a is used as a component of the liquid A, focusing on the fact that the powder a contains a large amount of bentonite. Specifically, liquid A is prepared by blending powder a, cement, stabilizer and water, and further, liquid B and liquid A made of water glass (sodium silicate aqueous solution) are mixed to provide a back-filling material. Mix.

  The backfilling material containing the powder a has a lower cement content than a normal backfilling material (mixed liquid A containing cement, bentonite, stabilizer and water, and further mixed with water glass). Regardless, it has the same uniaxial compressive strength as a normal backfill material. This will be clarified by Example 2 described later.

  When powder a is used as a component of the backfill material, cement and powder a are blended in a factory or a local plant to obtain a hydraulic composition (powder), and the hydraulic composition is stabilized with the stabilizer. And A liquid is mix | blended with water. And as above-mentioned, the A liquid and B liquid are mixed just before backfilling, and it inject | pours into a tail void.

3. Reuse as a component of filler Filler is used to fill cavities, voids, gaps, joints, cracks, etc. in construction work or civil engineering work. For example, in a cavity generated in the ground during construction work or civil engineering work, a filler material is backfilled instead of fluidized treated soil (soil mortar in which cement and water are added to the construction generated soil to improve fluidity). Fill the cavity with filler. In this embodiment, a filler is prepared as in the following (1) to (3).

(1) A hydraulic composition (powder) is prepared by blending cement (for example, blast furnace cement type B), powder b, and powder d. Among cement, powder b, and powder d, the mass ratio of powder d is the highest, and the mass ratio of cement is the lowest. And a filler is prepared by adding water to the hydraulic composition.

(2) A hydraulic composition (powder) is prepared by blending cement (for example, blast furnace cement type B), powder a and powder d. Among the cement, the powder a, and the powder d, the mass ratio of the powder d is the highest, and the mass ratio of the cement is the lowest. And a filler is prepared by adding water to the hydraulic composition.

(3) A hydraulic composition (powder) is prepared by blending cement (for example, blast furnace cement type B), powder b, and powder c. Among the cement, the powder b, and the powder c, the mass ratio of the powder c is the highest, and the mass ratio of the cement is the lowest. Then, the filler is prepared by adding water to the hydraulic powder.

The filler prepared as in the above (1) to (3), although the cement content is lower than normal fluidized soil (constructed soil containing cement and water), Uniaxial compressive strength is higher than normal fluidized soil. This is demonstrated by Example 3.
Since the filler was prepared by using the waste generated in the foundry, it is possible to generate a substitute material such as fluidized soil without using soil.

  A dust collector was connected to a sand treatment machine (used in the above-mentioned sand treatment process 1) installed at a casting factory of Aisin Takaoka Co., Ltd., and dust generated by the sand treatment machine was collected by the dust collector. The collected dust is separated by an ultrasonic vibration sieve screen classifier, powder a of small particle size (particle size less than 75 μm), powder b of medium particle size (particle size of 75 μm or more and less than 200 μm) and large particle size. When classified into powder c having a particle size of 200 μm or more, the mass ratio was 33% for powder a, 40% for powder b, and 27% for powder c. And the bentonite content rate (mass%), the average particle diameter, the density, and the specific surface area of the dust before classification and the powders a to c after classification were measured. The measurement results are shown in Table 1.

As described above, it is understood that powders a to c having different bentonite contents can be generated by classifying the dust generated by the sand processing machine. Therefore, the filler for the purpose can be prepared by adjusting the blending ratio of the powders a to c.
Moreover, it turns out that the bentonite content rate of the powder a after classification is higher than the bentonite content rate of the dust before classification. Therefore, bentonite contained in a normal backfill material can be substituted for the powder a.

  As in the case of Example 1 above, powder a having a small particle size classification (particle size less than 75 μm or particle size less than 45 μm) is collected by classification, and A liquid and backfill material containing powder a as components are prepared. did. Table 2 shows the volume, specific gravity, and blending amount of each component of the liquid A and the backfilling materials (Examples A to D). And while measuring the time for A liquid to pass a P funnel, the breathing rate of A liquid was measured. In addition, the gelation time of the backfill material was measured, and the uniaxial compressive strength of the cured backfill material was measured. The measurement results are shown in Table 3.

  As a comparative example, a normal A liquid and a backfill material containing bentonite as components were prepared, and similarly, the P funnel passage time, the breathing rate, the gelation time, and the uniaxial compressive strength were measured. Table 2 shows the volume, specific gravity, and blending amount of each component of normal A liquid and backfill material containing bentonite as components, and Table 3 shows the measurement results.

  As is apparent from Table 3, the P funnel passage time, breathing rate, and gelation time of Examples A to D satisfy the performance required as a shielding backfill material. The uniaxial compressive strength of the materials of Examples A to D satisfying the necessary performance as a shielding back-filling material. In Examples A, B, and D, the uniaxial compressive strength at the age of 28 days satisfies the performance required as a shielding back-filling material. Although the uniaxial compressive strength (average value) of Example C at the age of 28 days does not satisfy the performance required as a shielding back-filling material, the difference between them is slight.

In addition, Examples B, C, and D have a higher uniaxial compressive strength than the comparative example, although the amount of cement is less than that of the comparative example. Examples A, B, and D are more cemented than the comparative example. Although the blending amount is small, the uniaxial compressive strength at the age of 28 days is equal to or higher than that, so that it can be seen that a high strength backfilling material can be produced.
Moreover, since Example AD has a breathing rate lower than a comparative example, it turns out that A liquid and backfilling material with high water retention performance can be created.
In particular, Example B showed favorable results as a shielding backfill.

  As in the case of Example 1 above, by classification, the powder a having a small particle size (particle size less than 75 μm), the powder b having a medium particle size (particle size of 75 μm or more and less than 200 μm), and a large particle size (particle) Powder c having a diameter of 200 μm or more was collected. In addition, the residue generated in the shot blasting machine (used in the above-described residue peeling process 12) installed in a casting factory of Aisin Takaoka Co., Ltd. is subjected to a separation process by a magnetic separation type separator, Powder d from which the blast material was removed was collected.

  And the filler was prepared by mix | blending blast furnace cement B type | mold, powder b, powder d, and water with the compounding quantity shown in Table 4 (Example E). Moreover, the filler was prepared by mix | blending blast furnace cement B type | mold, powder a, powder d, and water with the compounding quantity shown in Table 4 (Example F). Moreover, the filler was prepared by mix | blending blast furnace cement B type | mold, powder b, powder c, and water with the compounding quantity shown in Table 4 (Example G). Note that the powder d and the powder c also serve as substitutes for fluidization treatment as in the comparative example.

  The specific gravity, flow value, breathing rate and uniaxial compressive strength of the prepared filler were measured. The results are shown in Table 5. Moreover, as a comparative example, Table 5 shows the specific gravity, flow value, breathing rate, and catalog value of uniaxial compressive strength of the fluidized soil prepared as shown in Table 4.

In Examples E and G, the specific gravity, flow value, breathing rate, and uniaxial compressive strength satisfy the performance required as a filler. In Example F, although the breathing rate does not satisfy the performance required as the filler, the specific gravity, the flow value, and the uniaxial compressive strength satisfy the performance required as the filler.
Moreover, although Example EG has a uniaxial compressive strength higher than a comparative example, although a compounding quantity of cement is smaller than a comparative example, it turns out that a filler with high intensity | strength can be created.

  DESCRIPTION OF SYMBOLS 1 ... Sand processing process, 9 ... Mold release process, 12 ... Residue peeling process, 13 ... Separation process. 14 ... Recovery process, 17 ... Dust collection process, 18 ... Classification process, ad ... Powder

Claims (6)

A dust collection process for collecting dust that floats when mixing sand and bentonite as raw materials for the mold;
A classification step of classifying the dust collected in the dust collection step into a plurality of particle size categories;
A recycling step of reusing the powder contained in the smallest particle size classification among the particle size classification classified by the classification step as a component of the backfilling material, Method.   2. The method for reusing casting waste according to claim 1, wherein the minimum particle size classification is less than 75 [mu] m. A mold releasing step of taking out a casting produced by casting from the mold;
A peeling step of peeling the residue of the mold attached to the surface of the casting by spraying a blast material onto the casting taken out in the mold releasing step;
A separation step of separating the blast material from the dust settled in the peeling step;
A recovery step of recovering the powder from which the blast material has been separated in the separation step;
A second reuse step of reusing the powder recovered in the recovery step as a component of a filler used for construction work or civil engineering work,
In the classification process, classification into three stages of particle size classification,
The method for reusing casting waste according to claim 1 or 2, wherein the powder contained in the medium particle size among the three particle size categories is also reused as a component of the filler in the second reuse step. . A mold releasing step of taking out a casting produced by casting from the mold;
A peeling step of peeling the residue of the mold attached to the surface of the casting by spraying a blast material onto the casting taken out in the mold releasing step;
A separation step of separating the blast material from the dust settled in the peeling step;
A recovery step of recovering the powder from which the blast material has been separated in the separation step;
A second reuse step of reusing the powder recovered in the recovery step as a component of a filler used for construction work or civil engineering work,
The method for reusing casting waste according to claim 1 or 2, wherein the powder contained in the minimum particle size category is also reused as a component of the filler in the second reuse step. In the classification process, classification into three stages of particle size classification,
Reusing the powder contained in the medium particle size category and the powder contained in the largest particle size category among the three-stage particle size categories as the components of the filler used for construction work or civil engineering work. The method for reusing casting waste according to any one of claims 1 to 4, wherein: A dust collection process for collecting dust that floats when mixing sand and bentonite as raw materials for the mold;
A classification step of classifying the dust collected in the dust collection step into a plurality of particle size categories;
And a blending step of blending the powder contained in the smallest particle size category among the particle size categories classified by the classification step with cement. A method for producing a hydraulic composition for a backfill material, comprising:

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