JP2001149909A - Producing method of reclaimed sand using waste incineration residue as raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce reclaimed sand having the useful usage by using a waste incineration residue as the raw material and to surely allow the use of the reclaimed sand. SOLUTION: This producing method of reclaimed sand comprises a grain size controlling process in which the granular waste incineration residue which is discharged from below the furnace of a waste incinerator is crushed and sieved so as to be smaller than the prescribed grain size, a dioxins decomposing process in which dioxins are decomposed after the grain size controlling process and a cleaning and classifying process in which the waste incineration residue is cleaned with cleaning water so as to remove fine particles and the reclaimed sand is obtained after the dioxins decomposing process. In addition, this producing method of the reclaimed sand is provided with a process for inspecting the reclaimed sand, a process for verifying the quality of the reclaimed sand and the process for water examination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to produce recycled sand which can be used as concrete aggregate, cement raw material, roadbed material, etc., using waste incineration residues discharged from below the waste incinerator as raw materials. About the method.

[0002]

2. Description of the Related Art Waste treatment in Japan has been developed mainly by incineration. However, there is a shortage of managed landfills for landfilling waste incineration residues, which has become a serious problem.

[0003] Therefore, it is an urgent task to extend the life of a managed final disposal site. To extend the life of a managed landfill, there is a method that does not produce incineration residues, or a method that recycles incineration residues.

[0004] As a method of not producing incineration residues, at present,
Gasification and melting furnaces have been developed and are expected as furnaces in the 21st century.

[0005] As a recycling method, there is a melting and solidifying method in which incinerated ash and dust are melted at a high temperature and used as a roadbed material. There is also a concrete solidification method in which the incineration residue is solidified with concrete and used as recycled crushed stone.

[0006]

However, the gasification and melting furnace requires funds of several billions to several tens of billions of yen in construction cost, and it is financially necessary to adopt it at the time of rebuilding the current incinerator. Impossible.

In addition, the melt-solidification method requires a large amount of billions of yen, and it is difficult to make a capital investment under the current situation where it is expected that the furnace will become a gasification-melting furnace in the future.

The concrete solidification method does not require much capital investment, and is a practical method when the melt solidification method cannot be used. However, cement and gravel are mixed with the waste incineration residue and solidified. Therefore, there is a problem that the volume of the processed waste residue is doubled. Moreover, the work of solidifying the concrete requires the work of using a mold, pouring the concrete into the mold and curing it, and then crushing the hardened concrete. Therefore, there is a problem that not only a considerable area of the site is required, but also the work is complicated and costly.

[0009] From this problem, if added value is added to the granular waste incineration residue itself and the waste can be recycled, the volume of the waste landfilled at the final disposal site can be reduced, and the life of the final disposal site can be extended. In addition, the cost of solidifying concrete can be significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method for producing recycled sand from waste incineration residue, which is capable of producing recycled sand having a useful use from waste incineration residue as a raw material. The purpose is to provide.

In the case of using the obtained reclaimed sand, it is impossible to recycle the reclaimed sand unless it is legally proved that the reclaimed sand is harmless.

In view of such circumstances, an object of the present invention is to provide a method for producing recycled sand from a waste incineration residue as a raw material, which makes it possible to reliably use recycled sand.

[0013]

Means for Solving the Problems As a result of diligent studies to solve the above problems, the present inventor has found that granular waste incineration residue is first crushed and sieved to adjust the particle size to a certain particle size or less. By treating waste incineration residues in the dioxin decomposition process, dioxins can be removed at a high decomposition rate.After that, the waste incineration residues are washed with washing water and classified to adhere to the waste incineration residues. Can remove fine powder that had been mixed or mixed, as well as remove salt and harmful substances contained in the waste incineration residue, and as a result, the resulting reclaimed sand was harmless, free of fine powder, and used for concrete. Has a usefulness as an aggregate, a raw material for cement, a roadbed material, etc., and it can obtain recycled sand from waste incineration residue of raw material at a high yield of 60 to 80%, and is a waste to be buried in the final disposal site The amount of 却残 residue was found to be able to greatly volume reduction.

Therefore, the invention according to claim 1 comprises a particle size adjusting step of crushing and sieving a granular waste incineration residue discharged from under a waste incinerator to reduce the particle size to a certain particle size or less, After the process, a dioxin decomposing step of decomposing dioxins in the waste incineration residue, and after the dioxin decomposition step, washing and classification of the waste incineration residue with washing water to remove fine powder and obtain recycled sand And a method for producing recycled sand from waste incineration residues as a raw material.

In this case, it has been found that in the washing and classifying step, the waste incineration residue can be efficiently washed by using a spiral classifier.

Therefore, the invention according to claim 2 is based on claim 1
The method for producing recycled sand from waste incineration residues as described above, wherein the washing / classifying step uses a spiral classifier to provide a method for producing recycled sand from waste incineration residues. .

Furthermore, it has been found that by blending a heavy metal fixing agent into the washing water, heavy metals can be easily and reliably removed from the waste incineration residue, and the recycled sand can be more reliably rendered harmless.

Therefore, the invention described in claim 3 is based on claim 1.
Or a method for producing recycled sand from waste incineration residue as a raw material, wherein the washing water contains a heavy metal fixing agent. I do.

In the case where recycled sand is produced from waste incineration residues as raw materials, the quality of the obtained recycled sand is inspected by a predetermined inspection organization, and the inspection organization checks that the quality of the recycled sand meets environmental standards. By proving that the recycled sand is harmless, it becomes possible to legally prove that the recycled sand is harmless and to ship the recycled sand, thereby ensuring the use of the recycled sand.

Therefore, the invention described in claim 4 is based on claim 1.
3. A method for producing recycled sand from waste incineration residues as described in any one of the above-mentioned items, wherein a predetermined inspection organization inspects the quality of the obtained recycled sand, and a predetermined inspection organization performs the inspection. A method for producing recycled sand from waste incineration residues as a raw material, comprising a recycled sand quality certification step of legally proving the quality of the recycled sand after the process.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for producing recycled sand from waste incineration residues according to the present invention will be described below.

FIG. 1 shows an overall flowchart of a method for producing recycled sand from waste incineration residues as a raw material according to the present invention.
FIG. 2 is a flowchart showing an example of a production apparatus for producing recycled sand from waste incineration residues as a raw material according to the present invention. Hereinafter, description will be made with reference to FIGS.

Waste incineration residue as raw material is generated by general incinerators such as household waste, or incinerators that incinerate industrial waste generated by business activities such as paper waste, wood waste, rubber waste, and fiber waste. It is a residue (bottom ash) discharged from the bottom of the furnace, and although it varies depending on the type of waste, it is generally a gray round granule and contains fine powder. Heavy metals are hardly contained in bottom ash because most of them have been treated at high temperature in an incinerator and have been transferred to fly ash. As an acceptance inspection, heavy metals in waste incineration residues may be analyzed to confirm that they are harmless. The raw material waste incineration residue A is supplied to the input hopper 1
Stored in 1.

In the present invention, first, a particle size adjusting step for crushing and sieving the raw material waste incineration residue to make the particle size smaller than a certain particle size is performed. If waste incineration residue having a large particle size is present, the decomposition rate of dioxin in the subsequent step of decomposing dioxins is reduced, so that the particle size is made uniform to ensure the decomposition of dioxins.

In the particle size adjusting step, the waste incineration residue A is conveyed from the charging hopper 11 to the crushing / sieving device 13 by the belt conveyor 12. In the crushing / sieving process 13,
Metals are separated from the waste incineration residue A by the magnetic separator 14 and stored in the stocker 15 as useful scrap B. Thereafter, the waste incineration residue A is sieved into fine particles of 5 mm or less and coarse particles of 5 mm / m or more using a vibrating sieve or the like with a certain particle size, for example, 5 m / m sieve. The coarse particles that do not pass through the sieve are passed through a crusher or crusher such as a hammer mill, a rod mill, or a jaw crusher to crush large particles such as a clinker and then sieved again. In this way, the particle size of the waste incineration residue is adjusted to a certain particle size or less. Scrap B is recycled.

The particle size is adjusted, for example, to 5 mm or less. This is in order to meet the conditions required as fine aggregate for concrete, that is, the conditions that the particle size is 5 mm or less and does not contain fine powder. Therefore, the size of the screen can be changed as needed. The waste incineration residue C adjusted to a certain size or less is supplied to the hopper 16
Is stored in

Next, the waste incineration residue C whose particle size has been adjusted is conveyed from the hopper 16 to the dioxin decomposition step by the conveyor 21. In the dioxin decomposition step, any dioxin decomposition method can be adopted. As a method for decomposing dioxins, for example, a method of decomposing dioxins by heat dechlorination treatment in a heat treatment step can be adopted. This heat dechlorination treatment uses, for example, a heat treatment unit 22 of an external heating type rotary kiln system comprising a heating unit accommodating a heater and a plurality of rotating retorts (inner cylinders) and a cooler 23. The waste incineration residue is passed through the rotary kiln 22 for 300 to 5
By heating to about 00 ° C., preferably about 450 ° C., the catalytic action of the metals in the waste incineration residue causes a reaction to remove chlorine from the dioxins or to cut off oxygen bridges, thereby producing dioxins. Decompose. The waste incineration residue subjected to the heat dechlorination treatment is quenched through a cooler 23 to prevent re-synthesis of dioxin. The removal rate of dioxins is 95% or more. The exhaust gas discharged from the rotary kiln 22 is guided to an incinerator via a dust collector, and is completely pyrolyzed. Waste incineration residue D from decomposition of dioxins in heat treatment process D
Are stored in the hopper 24.

Next, the waste incineration residue D is transferred to the hopper 24
From the conveyor 25 to the washing / classifying step. The purpose of this washing / classifying step is to wash the waste incineration residue D with washing water, and mainly to remove fine powder (referred to as “Noro”) and salt. By removing the noro, it is possible to obtain reclaimed sand that can meet, for example, environmental standards related to soil contamination. Further, it is preferable to remove heavy metals in the washing / classifying step by using washing water to which a heavy metal fixing agent is added, just in case. With the addition of the heavy metal fixing agent, heavy metals in the waste incineration residue form flocs,
Removed from waste incineration residue with fine powder.

Any washing and classifying apparatus that can achieve the above object can be used. In the present embodiment, a spiral classifier 30 is used. The spiral classifier 30 puts the waste incineration residue into the spiral tank 310, injects washing water from the tip side of the spiral tank 310, and removes the waste incineration residue by the spiral 322 rotating in the water tank 311 of the spiral tank. Washing and classification are performed by stirring and washing, and waste incineration residues having a large particle size are sorted out. Only the selected waste incineration residue having a certain particle size or more is carried out by the spiral 322 to obtain reclaimed sand, while the fine powder in the waste incineration residue overflows from the water storage tank 311 together with the washing water. . The spiral classifier will be described later.

The waste incineration residue is washed by the spiral classifier 30 and, for example, fine powder having a particle size of 0.15 mm or less is removed, and the necessary conditions for fine aggregate having a particle size of 0.15 to 5 mm are cleared. Recycled sand E can be obtained. The recycled sand E that has passed through the washing / classifying process is stored in the stockyard 40.

As the heavy metal fixing agent to be added as necessary to the washing water, those which are generally commercially available as chelating agents can be used. The components of waste incineration residues vary depending on the region and incinerator. For this reason, heavy metal fixing agents must be properly selected in accordance with waste incineration residues.
In some cases, it is difficult for the obtained reclaimed sand to meet the environmental standards for soil. There are more than 20 types of heavy metal fixing agents, and it is preferable to test waste incineration residues with these heavy metal fixing agents and to screen an appropriate heavy metal fixing agent. At the time of schooling, the waste incineration residue was treated experimentally by changing the type and amount of heavy metal fixing agent, and the obtained recycled sand was analyzed. Since it is necessary to carry out the inspection with certain inspection items as shown in the above, it is preferable to request an inspection institution, such as a measurement certification office, which is equipped with an inspection system.

Examples of the heavy metal fixing agent include a polymer heavy metal scavenger having a water-soluble polymer having a dithiocarbamic acid group (—NH—CS ₂ Na) and a thiol group (—SNa) as chelating groups. Can be. This polymer heavy metal scavenger is used for various heavy metal ions such as mercury, cadmium, lead, copper, trivalent and hexavalent chromium, and EDT.
It is effective for metal complexes such as A-Cu, and forms an insoluble salt in these metals and water, generates flocs and removes heavy metals. The amount of heavy metal fixing agent added to washing water is 1
It is about 0 to 45 ppm.

Although it is possible to wash with a chemical such as an acid or an alkali, it is necessary to separately perform a step of treating heavy metals extracted from the cleaning solution after the treatment. A heavy metal fixing agent is preferable because it may corrode a washing / classifying device such as a spiral classifier.

The obtained reclaimed sand E is subjected to the inspection of the inspection items indicated in the environmental standards for soil contamination as of July 1999 shown in Table 1 by the measurement certification office in the reclaimed sand inspection process. If this standard is not met, recycled sand cannot be recycled.

Further, even if the obtained reclaimed sand satisfies the environmental standards related to soil pollution, if it is not proved to be harmless by a measurement certification office, the reclaimed sand is legally recycled. It is not possible. Therefore, after obtaining the legal certification that the recycled sand obtained from the measurement certification facility in the next recycled sand quality certification process meets the environmental standards related to soil contamination, for example, fine bone for roadbed material and concrete It can be recycled as an extender for materials or as a raw material for cement.

On the other hand, the fine powder having a size of, for example, less than 0.15 mm separated from the regenerated sand together with the washing water is supplied to the sludge tank 5.
1 and sent to a solid-liquid separation step. As a solid-liquid separation device, for example, after being dehydrated to a water content of about 85% using a filter press 52, the tank 5
It is stored in 3. When a heavy metal fixing agent is added to the washing water, flocs are mixed in the washing water and are separated from the washing water as mud with the fine powder. The mud G is used, for example, as a bulking material for backfilling residual soil, or transported to a final disposal site.

The washing water separated from the mud by the solid-liquid separation device 52 is subjected to a water quality test in a water quality test step to determine whether or not the wastewater standards for heavy metals and the like are satisfied. If the water quality is not always inspected and managed so that the wastewater satisfies the water quality standard, the above-mentioned device cannot be operated. After it is confirmed that the water quality standard is satisfied, the pH is adjusted in the pH adjusting tank 54 and incinerated or discharged.

In the above-mentioned process, the process of decomposing dioxins is carried out by heat treatment. However, the method of decomposing dioxins is not limited to this, and any of existing methods or methods to be developed in the future may be used. Including both.
For example, a method of decomposing dioxins at normal temperature and pressure using a catalyst in a dioxin decomposition tank can be adopted.

FIG. 3 shows a schematic structure of a spiral classifier used in the present invention. In the spiral classifier 30, a spiral 322 rotatably supported by a rotating shaft 321 is disposed along the bottom surface of a spiral tank 310 having an inclined semicircular shape. This spiral 322 has 2
This is a three-stage type in which the diameter of the spiral increases in stages. The rotational speed of the spiral 322 is variable. The bottom of the spiral tank 310 is a water storage tank 311 for storing water, and the lower part of the spiral 322 is immersed in the water W stored in the water storage tank 311. In this spiral classifier, the washing water is supplied to the spiral tank 31
Injection is possible from a plurality of zero positions. In the spiral classifier 30 shown in FIG.
The washing water can be injected into the spiral tank 310 from a position near the center of the spiral tank 310, a position near the rear end of the spiral tank 310 from the front end, and a position near the rear end of the spiral tank 310. It has become. The injected washing water flows down in the spiral 322 and can wash waste incineration residues conveyed in the spiral 322 toward the distal end. It is desirable that a heavy metal fixing agent be added to the washing water. The cleaning water injected into the spiral tank 310 stays in the water storage tank 311 as the water storage W, and is then discharged from the overflow port 313 partitioned by the partition plate 312. An outlet 314 is opened at the bottom of the uppermost end of the spiral tank 310. An intermediate outlet is also provided at the bottom of the second-stage spiral tank 310, which is normally closed by a lid 315.
Regenerated sand passing through the second spiral can be discharged from the intermediate discharge port.

The waste incineration residue is poured into the washing water W stored in the water tank 311 from above the water tank 311. The input waste incineration residue sinks to the bottom of the water storage tank 311, is stirred in the cleaning water W with the rotation of the spiral 322 in the water storage tank 311, and is washed to remove fine powder, salt, and heavy metal. When a fixing agent is added, heavy metals are removed. The fine powder in the waste incineration residue is suspended in the washing water W,
Overflow port 3 with washing water containing salt and floc
13 to be discharged. On the other hand, the waste incineration residue having a large particle diameter is conveyed from the bottom of the water storage tank 311 through the spiral 322 toward the front end, and is stirred and washed in the water W while being conveyed. After coming out of the water storage W, it is washed or dehydrated with the injected washing water, and is discharged as recycled sand from a discharge port 314 at the upper end of the spiral tank 310.

In this spiral classifier, since the contact time between the waste incineration residue and the washing water is long and the waste incineration residue is stirred, sufficient washing can be performed. In addition, since it is a multi-stage type, cleaning and classification efficiency is good. Furthermore,
Wash water is stored in a step portion at the bottom of the spiral tank of each stage, and washing can be performed in this portion as well.

When the washing water is injected from or at the position of the tip of the spiral, the washing water flows down and the recycled sand is conveyed in a counter-current manner, so that the washing efficiency is good and the washing sand is good. Good quality recycled sand that has been washed can be obtained. When washing water is injected in the middle or from the middle, dehydration can be efficiently performed at the upper end of the spiral. Further, for example, a method of injecting cleaning water to which a heavy metal fixing agent is added from a position or injecting cleaning water without adding a heavy metal fixing agent from a position can be adopted. As a result, the heavy metal fixing agent is washed away from the regenerated sand, and sufficient washing can be performed. As described above, the spiral classifier 30 shown in FIG.
Various cleaning and classification conditions can be changed.

The particle size of the fine powder removed by the spiral classifier 30 can be adjusted by the amount of washing water injected, the amount of waste incineration residue charged, the number of revolutions of the spiral, and the like.
Particle size smaller than 05mm-0.3mm, usually 0.15
It is possible to remove fine powders of less than mm.

The yield of recycled sand obtained by the method for producing recycled sand from the waste incineration residue of the present invention as a raw material varies depending on the type of the waste incineration residue of the raw material and the particle size of the recycled sand. If the particle size is 0.15 mm or less as fine powder,
About 70-80%, fine powder (mud) is 30-20
%.

It has been confirmed that the obtained reclaimed sand satisfies the environmental standards for soil contamination shown in Table 1. In addition, since the salt was washed with water and the fine powder (mud) containing a large amount of salt was removed, chlorine ions were reduced to 9%.
0% or more is removed. As a concrete aggregate, the chloride needs to be less than 0.1% in terms of NaCl, but it has been confirmed that it is satisfied without any problem. The criteria for accepting recycled products as a raw material for cement differ somewhat depending on the cement manufacturer and factory. Generally, if the chlorine content is 500 mg / l or less, it can be reused as a raw material for cement. Has been confirmed.

Therefore, the recycled sand obtained by the method of the present invention is
It is a useful product that can be effectively used as a filler for concrete fine aggregate, as a cement raw material, and as a roadbed material, backfill material and the like.

FIG. 4 shows the results of a strength test in the case where recycled sand was used as an extender for fine concrete aggregate. According to this, it is recognized that mixing up to 50% is possible.

[0048]

[Table 1]

In the method for producing recycled sand from waste incineration residue according to the present embodiment, the particle size of the waste incineration residue is adjusted to a certain particle size or less in the particle size adjustment step, and then the dioxin is decomposed in the dioxin decomposition step. Can be removed with a high decomposition rate. Further, fine powder, salt, and heavy metals can be efficiently removed in the subsequent washing / classifying step, and harmless and recyclable recycled sand can be obtained in high yield.

The recycled sand inspection step, the recycled sand quality certification step, and the water quality inspection step are equivalent to software if the above-mentioned apparatus for producing recycled sand is hardware, and the recycled sand can be reliably recycled. In addition, the operation of the device can be ensured.

[0051]

According to the method of the present invention for producing recycled sand from waste incineration residue as a raw material, recycled sand having harmless and useful use from waste incineration residue conventionally discarded in a controlled final disposal site. Can be produced in good yield.

Further, by providing the recycled sand inspection step and the recycled sand quality certification step, it is possible to reliably use the recycled sand.

[0053]

[Brief description of the drawings]

FIG. 1 is a flowchart showing the steps of a method for producing recycled sand from waste incineration residues as a raw material according to the present invention.

FIG. 2 is a flowchart illustrating an example of an apparatus used in a process of a method for producing recycled sand from waste incineration residues as a raw material according to the present invention.

FIG. 3 is a structural diagram showing a schematic structure of a spiral classifier used in the present invention.

FIG. 4 is a graph showing the results of a concrete strength test when recycled sand obtained by the method of the present invention is used as fine aggregate of concrete.

[Explanation of symbols]

 Reference Signs List 13 particle size adjusting device 22 dioxin decomposing device (heat treatment device) 30 washing / classifying device 310 spiral tank 311 water tank 322 spiral

Claims (4)

[Claims] 1. A particle size adjusting step of crushing and sieving granular waste incineration residues discharged from the bottom of a waste incinerator to reduce the particle size to a certain particle size or less. A dioxin decomposing step of decomposing dioxins, and after the dioxin decomposing step, washing and classifying a waste incineration residue with washing water to remove fine powder and obtain reclaimed sand, Of recycled sand from waste incineration residues. 2. The method for producing recycled sand from waste incineration residues as a raw material according to claim 1, wherein said washing and classification step uses a spiral classifier as a raw material. Method for producing recycled sand. 3. The method for producing recycled sand from a waste incineration residue according to claim 1 or 2, wherein the washing water contains a heavy metal fixing agent, and the waste incineration residue as a raw material. Method for producing recycled sand. 4. A method for producing recycled sand from waste incineration residues as claimed in claim 1, wherein a predetermined inspection organization inspects the quality of the obtained recycled sand. A method for producing a recycled sand from waste incineration residues, wherein a predetermined inspection organization legally certifies the quality of the recycled sand after the inspection step.