JP5316888B2 - Method and system for treating harmful substances in mold sand - Google Patents

Description

The present invention relates to a treatment method and a treatment system for insolubilizing harmful substances such as heavy metals and halogen contained in mold sand.

Conventionally, mold sand used in foundries has been reused as a mold raw material through a predetermined treatment process, and waste sand containing spilled sand and dust collection dust has been reused as a cement raw material and a roadbed material raw material. However, due to the recent tightening of environmental cleanup regulations including soil, it is necessary to implement insolubilization treatment to prevent hazardous substances such as heavy metals and halogens from the Ministry of the Environment Notification No. 46 from exceeding the elution standard value of the soil environment standard. Has arisen.

As such a toxic substance insolubilization process, for example, Patent Document 1 discloses a technique for performing an insolubilization process by adding an additive containing magnesium oxide or the like as a main component to fluorine-contaminated soil and performing a mixing process. Yes.

JP 2005-324083 A

However, in the above-described processing method, in order to perform the insolubilization process, it is necessary to provide a separate processing facility, which increases the cost of the facility and requires a new installation location of the processing facility.

Therefore, the present invention realizes a processing method and a processing system that can reduce the processing cost for insolubilizing harmful substances such as heavy metals and halogens contained in the molding sand without greatly changing the existing casting equipment. The purpose is to do.

In order to achieve the above object, according to the present invention, in the invention described in claim 1, treatment of harmful substances in mold sand for insolubilizing harmful substances in mold sand used in a casting line for producing castings. In the method, the casting line is regenerated in a mold separation process for performing mold dispersion after pouring into the mold, a sand regeneration process for regenerating the mold sand discharged from the mold dispersion process, and a sand regeneration process. A recycle process for reusing the mold sand, which includes kneading the mold sand with unused foundry sand, additives, etc., and supplying the mold sand to a molding machine as a kneaded product used for mold molding. The technical means of adding an insolubilizing agent for insolubilization treatment to the mold sand in at least one of the transporting process between facilities for performing each process of the utilization process, the sand regeneration process and the kneading process is used.

According to invention of Claim 1, the insolubilization agent for performing an insolubilization process is used for casting sand in at least 1 process among the conveyance process between the facilities which perform each process of a reuse process, a sand reproduction | regeneration process, and a kneading | mixing process. It can be added to treat harmful substances in the mold sand.
This eliminates the need for special equipment for insolubilizing mold sand, without making major changes to the existing casting equipment, and simply providing equipment for adding insolubilizing agent to the mold sand. Hazardous substances such as heavy metals and halogens contained in the mold sand can be insolubilized.
Also, because hazardous substances are insolubilized in the casting line, hazardous substances in waste such as mold sand (waste sand) that has become unusable and spilled sand accumulated outside the conveyor of the casting line are below the standard value. Therefore, a new insolubilization process is not required after discharge, and the processing cost can be reduced.
Here, the insolubilization process is a process that insolubilizes to prevent the elution of harmful substances by chemical reaction, adsorption, etc., and stabilizes by collecting mainly heavy metal ions with a chelating agent, etc. Includes processing.

In the invention according to claim 2, in the method for treating harmful substances in the molding sand according to claim 1, the harmful substances include cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, fluorine, boron, etc. A technical means is used in which at least one of the second type specified harmful substances whose soil environmental standards are defined in the Soil Contamination Countermeasures Law is selected.

As in the invention described in claim 2, among cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, fluorine, boron, etc. The insolubilization treatment can be performed on at least one selected from the above.

According to a third aspect of the present invention, in the method for treating harmful substances in the molding sand according to the first or second aspect, the insolubilizing agent is used in a dust collection step of conveying dust generated in the reuse step to a dust collector. The technical means of further comprising the step of adding is used.

According to the invention described in claim 3, since it further includes a step of adding an insolubilizing agent in the dust collection step of conveying dust generated in the reuse step to the dust collector, the surface area per weight is small because the particle size is small and fine. Can be treated together with dust that is classified as a high-concentration contaminant to retain more chemicals and heavy metals.

The invention according to claim 4 is a system for treating harmful substances in mold sand for insolubilizing harmful substances in mold sand used in a casting line for producing a casting, wherein the casting line is applied to a mold. Mold removal equipment that performs mold separation after pouring of sand, sand regeneration equipment that regenerates the sand that has been generated in the mold dispersion equipment, casting sand that has been regenerated by the sand regeneration equipment, unused casting sand, additives, etc. Kneading equipment, and a kneading equipment for supplying to the molding machine as a kneaded product used for mold making, the mold separating equipment, the sand recycling equipment, the transport equipment between the equipment of the kneading equipment, the sand recycling equipment, At least one of the kneading facilities is provided with an insolubilizing agent addition facility for adding an insolubilizing agent for performing insolubilization treatment to the mold sand, and the insolubilizing agent addition facility is used to add any one of claims 1 to 3. Or one performs processing method of harmful substances in a template sand described, using the technical means of.

According to invention of Claim 4, insolubilization for performing insolubilization processing in at least one equipment among conveyance equipment between each equipment of mold separation equipment, sand regeneration equipment, and kneading equipment, sand regeneration equipment, and kneading equipment An insolubilizing agent addition facility for adding an agent to the mold sand is provided, and an insolubilizing agent for performing the insolubilization treatment can be added to the mold sand to treat harmful substances in the mold sand. The effect similar to invention of any one of claim | item 3 can be show | played.

It is explanatory drawing which shows a casting process and the reuse process of mold sand. It is explanatory drawing which shows the processing system of the harmful | toxic substance in casting sand. It is explanatory drawing which shows the example of a change of the processing system of the harmful substance in casting sand. It is explanatory drawing which shows the example of a change of the processing system of the harmful substance in casting sand. It is explanatory drawing which shows the example of a change of the processing system of the harmful substance in casting sand.

Hereinafter, the processing method and processing system of the hazardous | toxic substance in the mold sand of this invention are demonstrated with reference to figures. In addition, this invention is not limited to the following embodiment.

Here, the hazardous substances are the second class specified hazardous substances (cadmium or its compounds, hexavalent chromium compounds, cyanide compounds) listed in the Environmental Agency Notification No. 46 “Environmental Standards Concerning Soil Contamination” as soil environmental standards. , Alkyl mercury compounds, mercury or compounds thereof, selenium or compounds thereof, arsenic or compounds thereof, fluorine and compounds thereof, boron and compounds thereof).
In particular, fluorine and its compounds and boron and their compounds are easy to be mixed in the mold sand and have strict environmental standard values. Therefore, in this embodiment, these insolubilization treatments are taken as an example.

In the casting line shown in FIG. 1, a reuse process 1 for reusing used mold sand includes a mold spreading process 11, a sand recycling process 12, and a kneading process 13 surrounded by a dotted line portion in the figure.

In the mold releasing step 11, the mold that has been cooled after the pouring step is released to separate the cast product from the mold sand.

In the sand reclamation process 12, the mold sand collected in the mold separation process 11 is subjected to separation of iron pieces, etc. by magnetic separation, separation of binder (clay and resin) on the sand surface, sieving of fine powder, cooling with a sand cooler, etc. Play sand.

Here, in the sand regeneration step 12, the mold sand removed by blasting from the surface of the cast product taken out in the mold spreading step 11 is also sent.

In the kneading step 13, a predetermined amount of a binder such as clay and resin, water and the like is added to the molding sand transported from the sand regeneration step 12 and unused casting sand, and kneading is adjusted. After aeration and the like, it is supplied to the mold making process.

FIG. 2 shows a schematic diagram of a processing system for harmful substances in the molding sand of the present invention. The mold sand recovered by the mold separation facility 21 that performs the mold separation step 11 is conveyed by the belt conveyor 31 to the sand regeneration facility 22 that performs the sand regeneration step 12. The mold sand regenerated by the sand regeneration facility 22 is conveyed by the belt conveyor 32 to the kneading facility 23 that performs the kneading step 13.
A dust collector 42 is connected to the sand regeneration facility 22 via a duct 35, and dust generated in the sand regeneration facility 22 is collected.

The kneading equipment 23 stores mold sand and supplies it in a fixed amount, a mold sand supply device 23a, a binder such as clay and resin, and a material supply device 23b that supplies a material mixed with the mold sand such as water, and kneads these. And a kneading device 23c.
A dust collector 43 is connected to the kneading device 23c through a duct 36, and dust generated in the kneading equipment 23 is collected.

In the present embodiment, an insolubilizing agent adding device 23d for adding an insolubilizing agent is added to the material supply device 23b, and a predetermined amount of the insolubilizing agent is supplied to the kneading device 23c in a fixed amount with respect to the mold sand.

Here, the insolubilizing agent in the present invention is magnesium oxide, or a magnesium oxide-containing agent and ferric chloride, a magnesium chloride solution, an alkali metal silicate, or a PH regulator, calcium oxide and calcium aluminum. Examples thereof include those composed of nates, and those composed of calcium aluminate and calcium silicate.

In particular, a magnesium oxide-based insolubilizing agent can be suitably used for the insolubilization treatment of fluorine and its compound and boron and its compound having strict environmental standard values. In the present embodiment, the magnesium oxide-based insolubilizing agent is supplied in a powder state to the kneading device 23c by the insolubilizing agent adding device 23d.

Here, the insolubilizing agent includes those having hygroscopicity, and the insolubilizing agent adding device 23d equipped with a vibrator or the like is preferably used because it is liable to cause sticking in the hopper storing the insolubilizing agent and to suspend the shelf.

In the kneading device 23c, insolubilization treatment can be performed by supplying a kneading agent in addition to a binder such as mold sand, clay, resin, or water, and kneading. After the kneaded and adjusted mold sand is conveyed to the aerator 23e by the belt conveyor 33 and aerated, it is supplied by the belt conveyor 34 to a mold making facility (not shown) for performing the subsequent mold making process.

As described above, the hazardous substance processing system in the molding sand according to the present invention does not require a dedicated facility for insolubilizing the molding sand, and does not significantly change the existing casting facility, so that the insolubilizing agent adding device 23d is used. It is possible to insolubilize toxic substances such as heavy metals and halogens contained in the molding sand simply by providing them in the casting equipment.
In addition, because toxic substances are insolubilized in the casting line (kneading step 13 in the reuse step 1), mold sand that has become unusable (waste sand), spilled sand accumulated outside the casting line transport device, etc. Since noxious substances in the waste are treated below the standard value, a new insolubilization treatment is not required after the discharge, and the treatment cost can be reduced.
In particular, spilled sand has conventionally been collected by installing a chute etc. under a conveyor means such as a belt conveyor or collected manually, and it has been separately insolubilized, resulting in high processing costs. The effect of reducing the processing cost according to the present invention is great.

(Modification 1)
As shown in FIG. 3, it is also possible to employ a configuration in which an insolubilizing agent adding device 23d is provided above at least one of the conveyors 31, 32, 33, 34, and the insolubilizing agent is added to the transported mold sand. This eliminates the need for dedicated equipment for insolubilizing the mold sand, and makes it possible to insolubilize harmful substances such as heavy metals and halogens contained in the mold sand without making major changes to the existing casting equipment. In this configuration, since it is easy to install the insolubilizing agent adding apparatus 23d, the insolubilizing agent adding apparatus 23d is not installed in the kneading equipment 23.
In the above-described embodiment, the belt conveyor is exemplified as the transport facility between the facilities, but other transport means such as pneumatic transport and kneader can also be adopted.

(Modification 2)
As shown in FIG. 4, the insolubilizing agent adding device 23 d can be provided connected to the sand recycling facility 22. This makes it possible to add the insolubilizer to the foundry sand in which the foreign matters such as metal are removed and the properties such as the particle diameter and temperature are stable, so that the amount of the insolubilizer added can be appropriately maintained and managed. Moreover, in order to take sufficient reaction time for what needs time for insolubilization or stabilization, it can also store.

(Modification 3)
As shown in FIG. 5, an insolubilizing agent adding device 23d may be further provided in the dust collecting process of conveying the dust generated in the reuse process 1 to the dust collectors 42 and 43 that collect the dust. Thereby, since the particle size is small and fine, the surface area per weight is increased, and dust classified as high-concentration contaminants can be treated together to retain more chemical substances and heavy metals.

[Effect of the embodiment]
According to the processing method and processing system for harmful substances in the mold sand of the present invention, insolubilization is performed in at least one of the transporting process between facilities for performing each process of the reuse process 1, the sand recycling process 12 and the kneading process 13. An insolubilizing agent for performing the treatment can be added to the mold sand to treat harmful substances in the mold sand.
This eliminates the need for a dedicated facility for insolubilizing the molding sand, and does not significantly change the existing casting equipment, and the insolubilizing agent adding device 23d is included in the existing casting equipment, and is included in the molding sand. Hazardous substances such as heavy metals and halogens can be insolubilized.
In addition, because hazardous substances are insolubilized in the casting line, hazardous substances in waste such as mold sand that has become unusable and spilled sand that has accumulated outside the conveyor of the casting line are processed to below the standard value. Therefore, a new insolubilization process is not required after discharge, and the processing cost can be reduced.

[Other Embodiments]
In each of the above-described embodiments, the insolubilizing agent adding device 23d employs a configuration in which the insolubilizing agent is added to the mold sand in a powder state, but the present invention is not limited to this and can be added in various forms. . For example, in the case of a liquid insolubilizer, the solution of the insolubilizer can be added by a method such as dropping or spraying.

DESCRIPTION OF SYMBOLS 1 Reuse process 11 Mold separation process 12 Sand regeneration process 13 Kneading process 21 Mold separation equipment 22 Sand regeneration equipment 23 Kneading equipment 23a Mold sand supply apparatus 23b Material supply apparatus 23c Kneading apparatus 23d Insolubilizer addition apparatuses 31, 32, 33, 34 Belt conveyor 42, 43 Dust collector

Claims (4)

A method for treating harmful substances in molding sand for insolubilizing harmful substances in molding sand used in a casting line for producing castings,
The casting line is
A mold spreading process for casting mold after pouring into mold,
A sand regeneration process for regenerating the mold sand discharged from the mold separation process;
Reusing mold sand, including kneading the mold sand regenerated in the sand reclamation process with unused foundry sand, additives, etc., and supplying it to the molding machine as a kneaded product used for mold molding With a process,
A mold characterized in that an insolubilizing agent for performing insolubilization treatment is added to the mold sand in at least one of the transport process between facilities for performing each process of the reuse process, the sand regeneration process and the kneading process. How to treat harmful substances in sand. The hazardous substance is selected from at least one of the second type specified hazardous substances stipulated by the soil pollution control law, such as cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, fluorine and boron. The method for treating harmful substances in mold sand according to claim 1, wherein: The toxic substance in the mold sand according to claim 1 or 2, further comprising a step of adding the insolubilizing agent in a dust collection step of conveying dust generated in the reuse step to a dust collector. Processing method. A system for treating harmful substances in molding sand for insolubilizing harmful substances in molding sand used in a casting line for producing castings,
The casting line is
A mold disassembly facility that performs mold disassembly after pouring into the mold,
Sand reclamation equipment for reclaiming waste sand generated in the mold separation equipment;
Kneading mold sand regenerated with sand reclamation equipment with unused foundry sand, additives, etc., and kneading equipment for supplying to a molding machine as a kneaded product used for mold molding,
An insolubilizing agent for insolubilization treatment is added to the mold sand in at least one of the mold separation equipment, the sand reclamation equipment, the transport equipment between the equipment of the kneading equipment, the sand reclamation equipment, and the kneading equipment. Equipped with an insolubilizing agent addition facility
A processing system for hazardous substances in molding sand, wherein the method for treating hazardous substances in molding sand according to any one of claims 1 to 3 is performed by the insolubilizing agent addition facility.

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