JPH11300331A - Production of sand vsing waste incineration residue as raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reuse a waste incineration residue by washing a granular waste incineration residue discharged from a bottom of a waste incineration furnace, with water to remove a fine-powdery material from the incineration residue and to produce sand. SOLUTION: In this production, gravel washed with water contg. a heavy metal fixing agent is sieved with a sieve 21 having 5 mm mesh size and a remaining gravel fraction on the sieve 21 is rinsed with fresh water supplied to the gravel fraction at a point inside the sieve 21, in the immediate vicinity of a point at which the gravel fraction falls from the sieve 21, to wash off flocs from the gravel fraction. Further, fresh water for washing is supplied to a screw conveyer 3 in the vicinity of its outlet to wash a waste incineration residue conveyed from a receiving vessel 4, with the fresh water while allowing the fresh water to flow down through the inside of the screw conveyor 3, to produce sand from the waste incineration residue. The sand thus produced is allowed to fall from the outlet of the screw conveyor 3 into a product storage vessel 6 placed below the outlet of the screw conveyor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing sand that can be reused as concrete aggregate or cement raw material using waste incineration residues discharged from the bottom of a waste incinerator or the like as a raw material. .

[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.

The present invention has been made in view of the above circumstances, and provides a method for producing sand using waste incineration residues as a raw material capable of producing sand having a useful use by reusing the waste incineration residues. The purpose is to provide.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor found that granular waste incineration residues were attached to waste incineration residues by washing with water. Or, it can remove fine powder mixed with it and remove harmful substances such as chlorine contained in waste incineration residue, resulting in harmless and fine powder-free porous sand. I found what I could do. This sand is useful as an aggregate for concrete, and has an excellent component as a raw material for cement. It is obtained from a waste incineration residue in a yield of 60 to 70%, and has been conventionally discarded. The present inventors have found that 60 to 70% of the waste incineration residue can be reused and that the amount of the waste incineration residue to be buried in the final disposal site can be significantly reduced, thereby achieving the present invention.

Therefore, the invention according to claim 1 is to remove fine powder from the waste incineration residue by washing the granular waste incineration residue discharged from the bottom of the waste incinerator with water to remove sand. The present invention provides a method for producing sand using waste incineration residues as a raw material.

In the present specification, the term "sand" means not only sand having a particle size of less than 5 mm for concrete but also a particle having a particle size of 5 mm.
It is a concept including gravel of mm or more.

[0014] In the case where the granular waste incineration residue is used as fine aggregate for concrete, sieving is required. In that case, a wet sieving method is employed to reduce the sieving process. It has been found that it is possible to use the washing step with water, and it is efficient.

Therefore, the invention described in claim 2 is based on claim 1.
The method for producing sand from a waste incineration residue as described above, comprising a sieving step of wet-sieving the granular waste incineration residue, wherein the sieving step is to wash the waste incineration residue with water. The present invention also provides a method for producing sand using waste incineration residues as a raw material.

Further, by using a screw conveyor, for example, water is allowed to flow down in a countercurrent manner while the waste incineration residue is being conveyed through the screw conveyor, and washing is performed.
It has been found that washing can be efficiently performed and the incineration residue of the washed waste can be efficiently separated from water.

Therefore, the invention described in claim 3 is based on claim 1.
Or a method for producing sand from waste incineration residue as a raw material, wherein the waste incineration residue is washed with water while being conveyed using a screw conveyor. And a method for producing the same.

It has also been found that by continuously performing the above-mentioned wet sieving step and washing using a screw conveyor, the steps of sieving, washing and separation from water can be efficiently performed.

Therefore, the invention described in claim 4 is based on claim 1.
In the method for producing sand from the waste incineration residue as described above, the waste incineration residue is sieved by a wet method, and then the waste incineration residue having passed through the sieve is washed with water while being conveyed using a screw conveyor. The present invention provides a method for producing sand using waste incineration residues as a raw material.

Further, the waste incineration residue washed with water includes:
Although harmful heavy metals are hardly contained, it has been found that by adding a heavy metal fixing agent to water used for washing, heavy metals can be removed to ensure harmless sand.

Therefore, the invention described in claim 5 is based on claim 1.
5. The method for producing sand from waste incineration residue as described in any one of the above-described items, wherein the water used for washing contains a heavy metal fixing agent. A manufacturing method is provided.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a method for producing sand from waste incineration residue of the present invention will be described, but the present invention is not limited to the following embodiment.

FIG. 1 is a flow chart showing the steps of one embodiment of the method for producing sand from waste incineration residues of the present invention. Hereinafter, the steps will be described with reference to the flowchart of FIG.

First, when accepting the waste incineration residue as a raw material, the waste incineration residue is analyzed for heavy metals and the like. This waste incineration residue is discharged from the bottom of an incinerator that incinerates general waste such as household waste or industrial waste generated from business activities such as paper waste, wood waste, rubber waste, and fiber waste. Residue (bottom ash)
Depending on the type of waste, it is generally gray, round, granular and contains fine powder. Most of the heavy metals are treated at high temperature in the incinerator, and most of them have been converted to fly ash.Therefore, they are hardly contained in the bottom ash. I have confirmed.

Next, the received waste incineration residue is heated and dechlorinated to decompose dioxins. This heat dechlorination treatment uses, for example, a treatment device composed of a heat treatment device of an external heating type rotary kiln system and a cooler, and passes through a waste incineration residue through a rotary kiln at about 450 ° C.
By heating the dioxin, a reaction of removing chlorine from the dioxins or cutting off oxygen bridges is caused to decompose the dioxins. The incineration residue that has been thermally decomposed is rapidly cooled by passing it through a cooler to prevent re-synthesis of dioxin. Dioxin removal rate is 95%
That is all.

Next, prior to the next sieving process, the magnetic material is conveyed on a conveyor belt using a magnetic separator installed on a belt conveyor for conveying the waste incineration residue to a sieving device. Remove metals such as iron from waste incineration residue. Then, in order to remove coarse particles such as metal scraps and unburned matters, waste incineration residues are sieved and sorted by a sieving device using, for example, a 20 m / m sieve. The coarse particles of 20 m / m or more selected by the sieve are crushed by a crusher such as a hammer mill and sent to the next 5 m / m sieving step. Waste incineration residues that cannot be crushed by the crusher are solidified as usual. Also, a magnetic separator is arranged on a belt conveyor that conveys the waste incineration residue crushed by the crusher, and metals such as iron are removed from the waste incineration residue crushed by the crusher.

The waste incineration residue that has passed through the 20 m / m sieve is sieved with a 5 m / m sieve, for example, using a vibrating sieve. At this time, water mixed with a heavy metal fixing agent such as a chelating agent is injected, and wet sieving is performed by a water washing method, sieving is performed, and waste incineration residues are washed. The reason for using the 5 m / m sieve is to meet the conditions necessary for fine aggregate for concrete, that is, the condition that the particle size is 5 mm or less and that no fine powder is contained. Therefore, the size of the screen can be changed as needed.

As the heavy metal fixing agent to be added to water used for washing, for example, a polymer heavy metal having a dithiocarbamic acid group (—NH—CS ₂ Na) and a thiol group (—SNa) as chelating groups in a water-soluble polymer A trapping agent can be exemplified. This polymer heavy metal collector is effective for various heavy metal ions such as mercury, cadmium, lead, copper, trivalent and hexavalent chromium, and metal complexes such as EDTA-Cu. It can form insoluble salts and form flocs to remove heavy metals. The amount of the heavy metal fixing agent added to water is about 10 to 45 ppm.

The excess which has not passed through the 5 m / m sieve is crushed with a crusher such as a hammer mill to reduce the particle size, and then re-filtered with a 5 m / m sieve and reused as much as possible. The excess of 5 m / m sieve itself has a particle size of 20 mm or less and 5 mm or more, and can be reused as coarse aggregate for concrete or the like. for that reason,
The 5 m / m excess can be commercialized as gravel (included in the concept of sand as defined herein) without crushing.

After wet sieving using water containing a heavy metal fixing agent, the waste incineration residue that has passed through the 5 m / m sieve is washed again with water while classifying using a classifier, and is mainly slurried (fine powder). And remove chlorine and floc. Then, the waste incineration residue can be separated from water to obtain harmless sand that is purified and does not contain fine powder. This sand, after drying,
Can be shipped as a product.

On the other hand, the water used for the second washing is combined with the wet sieving, and the water is separated by precipitating the slag.
It can be recycled and used again for wet sieving or for the second water washing. A part of the water used for washing can be discharged after solid-liquid separation and water treatment, or can be incinerated after solid-liquid separation.

The separated noro contains relatively heavy metals,
Because of the high chlorine content, a water content of 85
After dewatering to about%, the concrete is solidified to make recycled crushed stone.

FIG. 2 shows the above-mentioned 5 m / m wet sieving process,
1 shows a schematic configuration of an embodiment of a sieving / washing / separating apparatus that continuously performs a washing step and a separation step from water. This sieve
The washing / separating apparatus 1 is provided with, for example, a vibratory wet sieving apparatus 2 called a vibrose sieve, and a transfer washing apparatus 5 composed of a screw conveyor 3 called a spiral classifier and a receiving tank 4 below the vibrating wet sieving apparatus. The wet sieving device 2 and the transport cleaning device 5 are integrated devices.
A receiving tank 4 is arranged below the outlet of the sieving device 2, a rear part of the screw conveyor 3, which is arranged obliquely in the receiving tank 4, is disposed, and a part in front of the screw conveyor 3 is separated from the receiving tank 4. It has a protruding structure. The screw conveyor 3 is driven and rotated by a motor (not shown), and carries out the waste incineration residue sinking at the bottom of the receiving tank 4 from the receiving tank 4.

Further, below the sieving / washing / separating apparatus 1, a product storage tank 6 for storing washed sand of less than 5 m / m, a slurry for storing washing water containing noro and a slurry for precipitating noro. A tank 7 and a gravel storage tank 8 for storing 5 mm to 20 mm of gravel, which is an excess of 5 m / m sieve, are provided. A screw feeder (not shown) is provided on the wet sieving device 2 to supply waste incineration residue to the wet sieving device 2, and water in the slurry tank 7 is supplied to the wet sieving device 2 via a pipe. It can be circulated. Further, 5 m from above the screen 21 of the wet sieving apparatus 2
The excess portion that has not passed through the / m screen 21 falls into the gravel storage tank 8.

Further, fresh water is supplied just before the excess of 5 m / m of the sieve 21 falls from the sieve 21, and the gravel washed with the water containing the heavy metal fixing agent is rinsed with fresh water to flush the flocs. ing. Further, fresh water for washing is supplied to the vicinity of the outlet of the screw conveyor 3, and the waste incineration residue transferred from the receiving tank 4 is washed by the screw conveyor 3 while flowing down the inside of the screw conveyor 3. ing. The water for cleaning may be the heavy metal fixing agent-containing water in the slurry tank 7 from which the noro has been separated. However, by washing with fresh water, flocs formed with more salt and the heavy metal fixing agent may be used. Since it can be washed away, the quality of the obtained sand can be improved.

A screw feeder (not shown) and a screw conveyor 3 (not shown) for supplying the waste incineration residue to the above-mentioned sieving apparatus 2 are variable in the amount of rotation by an inverter, respectively, depending on the nature of the waste incineration residue. Thus, the supply amount and the transport amount of the waste incineration residue can be arbitrarily changed.

The waste incineration residue that has passed through the 20 m / m sieve is supplied to the wet sieving apparatus 2 by a screw feeder (not shown), and mixed with water containing a heavy metal fixing agent circulated from the slurry tank 7. Sieved with sieve 21. The waste incineration residue is washed with water while being sieved, and the heavy metal is collected by the heavy metal fixing agent with the heavy metal fixing agent. In this case, the mixing ratio between the waste incineration residue and water can be, for example, a ratio of waste incineration residue: water = 1: 1 to 2 by weight. The contact time (residence time) of the waste incineration residue with water is, for example, about 10 to 20 seconds.

The excess waste incineration residue that has not passed through the 5 m / m sieve 21 is rinsed with fresh water, washed and dropped into the gravel storage tank 8. This gravel is crushed by a crusher and supplied to a 5 m / m sieve again. on the other hand,
The waste incineration residue that has passed through the 5 m / m sieve 21 falls together with the washing water into the receiving tank 4 in which water is stored, and precipitates at the bottom of the receiving tank 4. And it is conveyed by the screw conveyor 3 from the bottom part of the receiving tank 4, and is spirally conveyed in the screw conveyor 3 diagonally upward. At the time of this conveyance, the water is washed in a countercurrent manner by water supplied from above the screw conveyor 3. The washed waste incineration residue (sand) falls from the outlet of the screw conveyor 3 to the product storage tank 6 below. In this case, the ratio of the amount of waste incineration residue transported per unit time and the amount of water supplied per unit time is, for example, waste incineration residue: water = 1: 1.5 in volume ratio.
The ratio can be about 3 to 3. The contact time (residence time) of the waste incineration residue with water on the screw conveyor 3 is, for example, about 3 to 20 minutes.

On the other hand, the waste incineration residue is washed, and the washing water containing slag falls from the upper part of the receiving tank 4 into the slurry tank 7 by overflow. In the slurry tank 7, slag naturally precipitates and can be separated. The supernatant containing the heavy metal fixing agent from which the slag is separated is circulated and supplied to the wet sieving apparatus 2. Although not shown, the water overflowing from the slurry tank 7 is subjected to solid-liquid separation by a filter press, and after pH adjustment, management analysis is performed, and after confirming that it is harmless, the water is discharged. Alternatively, after solid-liquid separation, the filtrate can be incinerated by spraying it as it is into a furnace.

The wet sieving apparatus 2 is extremely efficient because the sieving can be performed and the waste incineration residue can be washed at the same time. In addition, by mixing a heavy metal fixing agent in the water to be washed, it is possible to remove heavy metals with this wet sieving apparatus.

In the transfer and cleaning apparatus 5 using the screw conveyor 3, the waste incineration residue is spirally transferred from bottom to top while being stirred by the screw conveyor 3, while water is transferred from top to bottom. Flows down spirally in contact with the waste incineration residue. Therefore,
The contact time between the waste incineration residue and water is long, and the waste incineration residue is agitated. As well as good washed and good quality sand can be obtained. At the same time, it can be separated from water, which is extremely efficient.

The present apparatus 1, which continuously performs the above-mentioned wet sieving, washing and separation steps, can wash waste incineration residues very efficiently and obtain high-purity sand. In addition, since it is performed in a wet manner, dust is not generated, and the working environment is good.

The thus obtained fine powder not containing 5
The yield of sand less than m / m is generally 60 to 70% of the entire waste incineration residue. Table 1 shows the analysis values of heavy metals and harmful organic compounds in the obtained sand.

[0044]

[Table 1] From the results in Table 1, mercury, cadmium, lead, hexavalent chromium,
Heavy metals such as arsenic are below the detection limit, and organic chlorine compounds such as carbon tetrachloride are also below the detection limit.It is recognized that all harmful items meet the environmental standards for recycling. . Table 2 shows the results of the chloride ion extraction test.

[0045]

[Table 2] It can be recognized that 90% or more of chloride ions were removed by washing with water and removing noro containing a lot of salt. As a concrete aggregate, chloride needs to be less than 0.1% in terms of NaCl.
Meet without problems. The criteria for accepting recycled products as cement raw materials differ somewhat depending on the cement manufacturer and factory, but generally 500 mg / l or less can be reused as cement raw materials, and satisfies this standard.

From these analysis results, the sand obtained by the method of the present invention is a harmless and high quality sand in which no heavy metals are detected and the chlorine content is small. Therefore, for example, the sand obtained by the method of the present invention can be used at a rate of several tens of percent of the total aggregate for concrete and used as an extender for fine aggregate for concrete. In addition, since it meets the criteria for accepting recycled products as a raw material for cement, it can be used as a raw material for cement. Gravel-like waste incineration residues of less than 20 mm and 5 mm or more also have uses as raw materials for cement.

According to the method for producing sand from the waste incineration residue of the present embodiment, the waste incineration residue is efficiently washed with water, and in particular, chlorine and fine powder are efficiently removed from the waste incineration residue. Harmless concrete aggregate,
Sand that can be used as a cement raw material or the like can be obtained from waste incineration residues at a yield of 60 to 70%. As a result, the volume of waste incineration residues conventionally disposed of in a managed final disposal site can be reduced by 60 to 70% compared to the conventional type, and the life of the final disposal site can be extended, which is extremely useful for society. is there.
Moreover, since the amount of concrete solidification work can be reduced, the cost of concrete solidification can be reduced.

In the above embodiment, the waste incineration residue was washed with water in the wet sieving step and the transport and washing step using a screw conveyor. However, the washing method is not particularly limited. For example, an ordinary stirring type washing tank is used. Alternatively, a washing method using a fluidized bed type column or the like can be adopted.

In the above embodiment, the water used for cleaning contains a heavy metal fixing agent. However, since this heavy metal fixing agent is mixed just in case, it may not be necessary to mix it. Further, it is a matter of course that the water used for cleaning may be mixed with a cleaning aid such as a surfactant and a pH adjuster.

[0050]

According to the method for producing sand from waste incineration residue of the present invention, the waste incineration residue conventionally buried in the final disposal site is reused to produce useful sand. It can be manufactured and can meet the social demands of extending the life of final disposal sites.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing an outline of an apparatus for continuously performing wet sieving, washing, and separation from waste water of a waste incineration residue according to the present invention.

[Explanation of symbols]

1 .... wet sieving / washing / separation device 2 .... wet sieving device, 3.
... Screw conveyor, 4 ... Receiving tank, 5 ... Conveying and washing equipment, 6 ... Product storage tank, 7 ... Slurry tank, 8 ... Gravel storage tank

Claims (5)

[Claims] Claims: 1. Disposal, characterized in that granular incineration residues discharged from the bottom of a waste incinerator are washed with water to remove fine powder from the waste incineration residue to obtain sand. A method for producing sand from incineration residues. 2. The method for producing sand from waste incineration residues as a raw material according to claim 1, further comprising a sieving step of sieving the granular waste incineration residues by a wet method, wherein the sieving step is A method for producing sand from waste incineration residues as a raw material, wherein the waste incineration residues are also washed with water. 3. The method for producing sand from waste incineration residues according to claim 1 or 2, wherein the waste incineration residues are washed with water while being conveyed using a screw conveyor. A method for producing sand from incineration residues. 4. The method for producing sand from waste incineration residue as a raw material according to claim 1, wherein said waste incineration residue is sieved in a wet manner, and then the waste incineration residue passed through a sieve is passed through a screw conveyor. A method for producing sand from waste incineration residues, wherein the sand is washed with water while being transported. 5. The method for producing sand from waste incineration residues according to claim 1, wherein the water used for washing contains a heavy metal fixing agent. A method for producing sand from incineration residues.