WO2012014383A1

WO2012014383A1 - A method and a system for treating hazardous materials that have been generated in a foundry line

Info

Publication number: WO2012014383A1
Application number: PCT/JP2011/003836
Authority: WO
Inventors: Masaki Suzuki; Hiroyuki Amano
Original assignee: Sintokogio Ltd
Current assignee: Sintokogio Ltd
Priority date: 2010-07-27
Filing date: 2011-07-05
Publication date: 2012-02-02
Anticipated expiration: 2013-01-27
Also published as: JP5435364B2; CN102958627A; JP2012024826A; BR112012033401A2

Abstract

A method and a system for treating hazardous materials by insolubilizing the hazardous materials, such as heavy metals and halogen, that are contained in collected dust are provided. Only a small facility must be added to a foundry line. The foundry line reuses molding sand by performing the steps of shaking out a casting (14), reclaiming the molding sand (11), and mulling the sand (10). The collected dust that has been generated in the foundry line is transported to the step of mulling the sand to mull the molding sand with the dust and an insolubilizing agent. Thus the hazardous materials are insolubilized. Since no facility for insolubilizing the hazardous materials is required, the cost for facilities can be reduced. Further, if the treated sand is reused for a raw material for cement or a roadbed, no hazardous materials elute.

Description

A METHOD AND A SYSTEM FOR TREATING HAZARDOUS MATERIALS THAT HAVE BEEN GENERATED IN A FOUNDRY LINE

The present invention relates to a method and a system for treating hazardous materials. Specifically, it relates to a method and a system for insolubilizing hazardous materials, such as heavy metals and halogens, that are contained in dust collected from a foundry line.

Conventionally, sand that has been used in a foundry has been reused as a material for molds after predetermined treatments. Sand that includes collected dust and that is to be disposed of has been reused as a material for cement or a roadbed. However, since the requirements for a clean environment such as for soil have recently increased, a need for an insolubilization treatment has arisen to prevent heavy metals such as cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, and boron and halogens such as fluorine from eluting into soil.

As an example of insolubilization treatments for these hazardous materials, Japanese Patent Laid-open Publication No. 2005-324083 discloses an insolubilization treatment in which additives having magnesium oxide as the major component are added to fluorine-contaminated soil, and mixed.

To insolubilize the hazardous materials by applying that treatment to a foundry line, a facility 1 for an insolubilization treatment must be installed as shown in Fig. 2., The hazardous materials include heavy metals and halogens and are contained in collected dust. Thus the cost for facilities increases and a space for the facility for insolubilizing by that treatment is additionally required. These have been problems.

The object of the present invention is to provide a method and a system for treating hazardous materials that have been generated in a foundry line. The method and system do not require any additional facility other than the foundry line. Only a small facility must be added to the foundry line. By the method and system hazardous materials, such as heavy metals and halogens, that are contained in collected dust can be insolubilized. Thus the cost for the facilities can be reduced and no large space for facilities is required.

To achieve that object, the method of the present invention for treating hazardous materials that have been generated in a foundry line is a method for insolubilizing the hazardous materials that are contained in collected dust generated in the foundry line. The foundry line performs the steps of shaking out a casting after molten metal is poured into molds, reclaiming the molding sand that is discharged by shaking out a casting, and mulling the reclaimed molding sand with at least green sand and an insolubilizing agent to feed the mulled sand to a molding machine for forming molds. The molding sand is reused. The collected dust generated in at least one of those steps and the step for transportation between those steps is transported to the step of mulling the sand. There the molding sand is mulled with the dust and an insolubilizing agent. Thus the hazardous materials are insolubilized.

In the step of mulling the sand, the molding sand can be prepared. The hazardous materials contain at least one of cadmium and its compounds, hexavalent-chromium compounds, cyanogen compounds, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds. These materials contain cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, fluorine, or boron. They must be removed from soil, to prevent it from being polluted.

To achieve that object, the system of the present invention for treating hazardous materials that have been generated in a foundry line is a system for insolubilizing the hazardous materials that are contained in collected dust generated in the foundry line for manufacturing castings. The foundry line comprises a facility for shaking out a casting after pouring molten metal into molds, a facility for reclaiming the molding sand that is discharged from the facility for shaking out a casting, and a facility for mulling the reclaimed molding sand with at least green sand and an insolubilizing agent to feed mulled sand to a molding machine for molding. The system comprises a foundry line and a facility for transporting collected dust to the facility for mulling the sand. The facility for mulling the sand comprises a facility for adding an insolubilizing agent and collected dust to molding sand.

By the present invention, collected dust that has been generated in a foundry line is transported to the facility for mulling molding sand. The dust is insolubilized by mulling the molding sand with the dust and an insolubilizing agent. Thus no dedicated facility for insolubilizing hazardous materials, such as heavy metals and halogen, that are contained in the collected dust, is required. Thus the cost for the facilities can be reduced, and no large space for facilities is required. If the molding sand treated by the method or system of the present invention is to be reused as a raw material for cement or a roadbed, no hazardous materials are eluted, and any infection to soil is prevented.

The basic Japanese patent application, No. 2010-167793, filed July 27, 2010, is hereby incorporated in its entirety by reference into the present application.
The present invention will become more fully understood from the detailed description given below. However, the detailed description and the specific embodiment are illustrations of desired embodiments of the present invention, and are described only for an explanation. Various possible changes and modifications will be apparent to those of ordinary skill in the art on the basis of the detailed description.
The applicant has no intention to dedicate to the public any disclosed embodiment. Among the disclosed changes and modifications, those which may not literally fall within the scope of the present claims constitute, therefore, a part of the present invention in the sense of the doctrine of equivalents.
The use of the articles "a," "an," and "the" and similar referents in the specification and claims are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention, and so does not limit the scope of the invention, unless otherwise claimed.

Fig. 1 is a flowchart illustrating the steps of the embodiment of the present invention. Fig. 2 is a flowchart illustrating the steps of the conventional example.

Below, referring to Fig. 1, an embodiment of the present invention is described. In the flowchart of the foundry line in Fig. 1, the number 10 denotes the step of mulling molding sand that utilizes a facility for mulling the sand. In the step of mulling the sand, the molding sand that is transported from the step 11 of reclaiming the molding sand is mulled with green sand and additional materials to obtain mulled sand that is to be used for forming molds. The additional materials are binders such as clay and resin. The molding sand that has been mulled with a predetermined amount of water is transported to the step 12 of molding. In the step 12 of molding, molds are formed by using the molding sand. In the following step 13 of pouring, molten metal is poured into the molds. Thus a casting is manufactured.

The molds are cooled after the step 13 of pouring and are transported to the step 14 of shaking out a casting. In the facility for shaking out the casting, the casting and molding sand are separated. The separated sand is transported to the step 11 of reclaiming the molding sand. In the facility for reclaiming the sand, the molding sand is reclaimed, i.e., pieces of iron are removed by a magnetic separator, the binders are removed from the surfaces of the sand particles, fine particles are filtered, and the sand is cooled by a sand cooler. By the step 14 of shaking out the casting, the step 11 of reclaiming the sand, and the step 10 of mulling the sand, the step of reusing the molding sand is constituted.

The sand that adhered to the surface of the casting that is taken out in the step 14 of shaking out the casting is removed by the step 15 of cleaning the casting. The removed sand is transported to the step 11 of reclaiming the sand. The casting from which the sand is removed by the step 15 of cleaning the casting is shipped out after the step 16 of finishing the casting and the step 17 of inspecting the casting are completed.

In the foundry line, dust that contains hazardous materials such as heavy metals and halogens is generated. Thus it is collected by a dust collector 20. It is generated in each of those steps as described above and the step of transportation between the steps. Among them much dust is generated in the step 14 of shaking out the casting and the step 11 of reclaiming the sand. Thus the dust is collected in at least one of these two steps.

Normally the dust collected by the dust collector 20 contains at least one of hazardous materials such as cadmium, hexavalent chromium, mercury, selenium, lead, arsenic, fluorine, boron, and a compound containing one of these substances. These hazardous materials must be removed so as to prevent soil from being polluted. By the present invention, the collected dust containing these hazardous materials is transported to the step 10 of mulling the sand by a means 21 for transporting the dust, such as conveyor-belt machinery and a tube. The means 21 for transporting the dust is preferably hermetically sealed so as to prevent the dust from scattering during transportation.

In the step 10 of mulling the sand, the insolubilizing agent and the collected dust are added to the molding sand by a facility for adding the insolubilizing agent. The insolubilizing agent may include magnesium oxide, an agent containing magnesium oxide and ferric chloride, calcium chloride, alkali-metal silicates, calcium oxide and calcium aluminate, or calcium aluminate and calcium silicate.

About the treatment for insolubilizing fluorine and its compounds and boron and its compounds, the allowable amount for eluting these substances to soil is strictly limited, as one of the countermeasures against environmental pollution. Magnesium oxides are appropriate for an insolubilizing agent to insolubilize these substances. In this embodiment, a powdery insolubilizing agent of magnesium oxides are used. The facility for adding the insolubilizing agent is preferably designed to supply a constant amount of an insolubilizing agent from a reservoir.

In this way the collected dust that contains the hazardous materials is transported to the step 10 of mulling the sand. There the molding sand is mulled with the collected dust and the insolubilizing agent. Thus the hazardous materials react with the insolubilizing agent to be fixed in an insoluble state. They do not elute in molding sand. The molding sand that has been treated by the abovementioned treatment can be used for forming molds without any further treatment. Further, if the sand is reused as waste sand that is used for a raw material for cement or for a roadbed, it does not cause pollution in an environment of soil.

By the present invention, only the means 21 for transporting the collected dust to the step 10 of mulling the sand and the facility for adding an insolubilizing agent must be added to an existing foundry line, which is equipped with a dust collector. No facility for insolubilizing the sand is required. Thus the cost for facilities can be low. Further, no space for a facility for insolubilizing the sand is required.

Claims

A method for treating hazardous materials by insolubilizing the hazardous materials in collected dust that has been generated in a foundry line, wherein the foundry line reuses molding sand by performing the steps of:
shaking out a casting after molten metal is poured into molds;
reclaiming the molding sand that is discharged after the step of shaking out the casting; and
mulling the molding sand that has been reclaimed by the step of mulling the sand with at least green sand and an insolubilizing agent to feed mulled sand to a molding machine, the mulled sand being used for forming molds;
characterized in that the collected dust generated in each of the steps or the step of transporting the sand between the steps is transported to the step of mulling the sand where the molding sand is mulled with the transported dust and the insolubilizing agent.
The method of claim 1, wherein the molding sand is prepared in the step of mulling the sand.
The method of claim 1, wherein the hazardous materials contain at least one of cadmium and its compounds, hexavalent-chromium compounds, cyanogen compounds, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds.
A system for treating hazardous materials by insolubilizing the hazardous materials in collected dust that has been generated in a foundry line that manufactures a casting, wherein the foundry line comprises:
a facility for shaking out a casting after molten metal is poured into molds;
a facility for reclaiming molding sand that is discharged from the facility for shaking out the casting; and
a facility for mulling the molding sand reclaimed by the facility for mulling the sand with at least green sand and an insolubilizing agent to feed mulled sand to a molding machine, the mulled sand being used for forming molds;
characterized in that the system comprises the foundry line and a facility for transporting the collected dust to the facility for mulling the sand, and
in that the facility for mulling the sand comprises a facility for adding the insolubilizing agent and the collected gas to the molding sand.