JP2706634B2 - Recycling method of main ash of stalker type incinerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention processes incineration ash discharged from under a stoker type incinerator for general waste,
The present invention relates to a processing method for utilizing iron scrap, non-ferrous metal scrap, and earth and sand for civil engineering.

[0002]

BACKGROUND OF THE INVENTION According to the Ministry of Health and Welfare's "Japanese Waste 1991", 73% of municipal solid waste is incinerated, and the total weight of this incinerated waste is 100%.
%, The weight of incineration residue after incineration is 16.2%. In addition, the amount of incinerated waste generated in Japan is about 94,000 tons per day, and even if it is incinerated, 15,000 tons of incineration residues remain per day and are transported to the final disposal site for landfill. I have. However, the place where the above-mentioned landfill waste is landfilled, that is, the space of the final landfill disposal site is naturally limited, so that some municipalities will not be able to secure landfill space in the very near future if the current pace is maintained. In the treatment of incineration ash (not fly ash) discharged from the bottom of a stalker type incinerator, currently only iron is separated and recovered by a magnetic separator in some incineration plants, but the remaining non-ferrous metals and Non-metallic substances containing iron that passed through the magnetic separator have been disposed of in landfills. If there is some way to recover and use these iron, non-ferrous metals and non-metallic substances, the life of final landfills scattered throughout the country can be extended. Therefore, the present inventors have focused on recovering and utilizing useful materials from incinerated ash that has been conventionally disposed of in landfills, and as a result, the incinerated ash from which metals have been removed has a large amount of its components and its enormous amount. Considering that the use as civil engineering materials is the most suitable in view of the amount, and further researched and found that if the following conditions were satisfied, the nonmetallic substance could be sufficiently used as civil engineering soil. Unburned organic substances have been removed Chloride content has been reduced Being harmless by the alkali silica reaction Iron has been sufficiently removed Non-ferrous metals have been removed Particle shape It must be homogenized.Eluted amount of heavy metals should be less than specified value.Dioxin should be sufficiently decomposed.

[0003]

Means for Solving the Problems The present inventors have described the above-mentioned.
As a result of intensive studies on a method for improving and stabilizing the quality of non-metals from incinerated ash so as to satisfy the above conditions, the specific process of the present invention has been completed. That is, the present invention relates to a method for recycling metals and reusing nonmetallic substances from incinerated ash discharged from the bottom of a stoker type incinerator for waste, and (1) a clinker-like process from the incinerated ash. After removing coarse pieces such as ingots, (2) a roasting step of roasting the incinerated ash at 300 to 500 ° C., and (3) sorting to remove fine powder, irons, and non-ferrous metals from the incinerated ash. And (4) a pulverizing / polishing step of dividing the remaining non-metallic substance into two according to particle size, pulverizing / polishing and processing into particles, and (5) chemically refining the granulated residual with dilute sulfuric acid or the like. And a chemical treatment step of washing with water after the treatment.

[0004] Hereinafter, the method for reusing waste incineration ash of the present invention will be specifically described. In the treatment method of the present invention, first, as a first step, in order to protect equipment in a subsequent step from incineration ash discharged from a water tank provided under the stoker type incinerator for waste. In addition, kitchen utensil pieces such as frying pans and kettles, metal pieces such as tire wheels and pearls, clinker-like ingots and the like are removed by a mechanical method such as a screen.

[0005] Next, the incinerated ash is heated and roasted in a roasting furnace. This roasting process roughly performs the following three functions. (1) Thermal decomposition of unburned organic substances contained in incinerated ash,
By converting it to inorganic material, the incinerated ash becomes a base that can be used as civil engineering materials. (2) Eliminate odor sources peculiar to incineration ash, and destroy bacterial growth factors. (3) Thermal decomposition of dioxin. As a result of treating the incineration ash discharged from the incinerator in the incinerator, the inventors have confirmed that the ignition loss was significantly reduced and most of the thermally decomposable substances were decomposed. Table 1 is an example, and it can be determined that the incinerated ash after the actual treatment was converted to an odorless inorganic substance having no odor.

[0006]

[Table 1]

Next, regarding dioxin, dioxin is polychlorinated dibenzoparadioxin (PCD).
DS) and polychlorinated dibenzofuran (PCDFS). PCDDS has 75 isomers, and PCDDS has 135 isomers, and their biological effects (toxicity) are diverse. Generally, each type of toxicity of PCDDS and PCDFS is assumed, and the toxicity of a substance containing dioxin is evaluated as a toxicity equivalent concentration (TEQ). Table 2
Are some examples of the amount of dioxin in the incineration ash discharged from the incinerator and its toxic equivalent concentration.

[0008]

[Table 2]

[0009] Although there is no official indication of how much dioxin in incinerated ash can be said to be biologically acceptable, there are some indications for measuring the use of incinerated ash. Even so, dioxins must be significantly reduced. It has been reported in academic journals that dioxin can be completely decomposed by heating at 300 ° C or more for several tens of minutes, and it is currently recognized as such. The inventors selected a kiln type heating furnace as a practical method of roasting incinerated ash, and heated the outer periphery of the rotary kiln body instead of blowing high-temperature combustion gas into the kiln body. Suppress the incineration ash, which is a roasting substance,
A method was devised to control the roasting residence time of the material to be roasted by adjusting the inclination angle of the kiln body. In addition, the incineration ash was fed into the rotary kiln body by a screw conveyor type and the discharge port was made by a damper type, thereby minimizing the leakage of gas inside. By this method, a technology for continuously roasting a large amount of incinerated ash was established. Table 3 shows an example of the dioxin concentration of the incinerated ash after the treatment in the roasting step and the chemical liquid treatment step and the water after the washing by the treatment method of the present invention.

[0010]

[Table 3]

[0011] The TEQ values shown above are the permissible daily intake (ADI values) for the general population according to the "Dioxin Experts' Meeting on Waste Management" in the Federal Republic of Germany and in Japan.
Even lower than 0.1 ng / kg-day (kg is human weight). This ADI value is for dioxin released into the atmosphere. If this calculation is applied to a human body weighing 60 kg, the permissible intake is 6 ng / day.
Compared to 0.009ng / g, this is equivalent to 666g of this product entering the human body as it is. Although this is not possible, 0.009 ng / g is a sufficiently small and safe numerical value.

Next, an alkali silica reaction (hereinafter referred to as ASR)
ASR means that the product produced by the reaction of the silica contained in the aggregate with the reactive silica in the aggregate absorbs water and expands, causing cracks and the like in the concrete. Phenomenon
Judgment of the reactivity by the reaction test method (chemical method) of JIS A 5308 is as follows: "When the amount of fused silica (Sc) is 10 mmol / L or more and the amount of reduced alkali concentration (Rc) is less than 700 mmol / L, the amount of dissolved silica (Sc) is the decrease in alkali concentration (R
c) In the case of the above, the aggregate is determined to be harmless, and the others are determined to be harmless. ". Then, the present inventors repeated ASR for incineration ash of many stalker incinerators, and it was determined that all of them were harmless. Table 4 shows examples of the analysis values.

[0013]

[Table 4]

Regarding the fact that iron has been sufficiently removed, a stalker type incinerator installed around the city is provided with a device (magnetic separator) for recovering iron from incinerated ash. There are places. The purpose of this is to separate iron and recycle it as a raw material for iron making. However, this separation rate is low, and in many cases, existing equipment does not reach 50%. In local municipalities, iron is hardly separated. However, when incinerated ash is used as earth and sand for civil engineering, the iron removal rate must be further increased in order to avoid coloring due to iron oxidation and to remove coarse iron pieces. Therefore, in the present invention, the conventional magnetic force 10
Use a magnetic separator of 3000 gauss or more instead of a general magnetic separator of a suspended type of about 00 gauss or incorporated in a chute. By arranging the portions, the distance between the magnetic force portion and the non-sorted object is made the shortest distance, and a device is devised so that a sufficient approach time can be maintained, thereby completely removing iron.

Next, in the present invention, non-ferrous metal is removed.
This is a step of removing non-ferrous metals from the incinerated ash after the above iron removal step using a high voltage electric field or a strong induced current generated by rotating a strong magnet at high speed. As described above, this step is a step performed in order to achieve "removal of non-ferrous metals" required as a condition when the non-metallic substance is used as earth and sand for civil engineering. The reason is that the mixing of irregular metal pieces is not desirable for earth and sand for civil engineering, and many of these nonferrous metals are relatively expensive and highly valuable, such as copper and brass. It is for planning. In general, non-ferrous metals in incineration residues are often miscellaneous small metal pieces.For example, relatively large pieces such as kettles and pipes can be easily removed by sieving, etc. Have difficulty.
Actually, there is no example of carrying out an operation of separating nonmetals and nonferrous metals from incineration ash. As one method of separating non-ferrous metals from non-metals, attempts have been made to add metal particles to heavy oil and separate them with a specific gravity difference.However, as a method of treating incinerated ash, an operation of washing and removing oil is indispensable, which is complicated and economical. Not a target.

Therefore, in the incineration ash treatment of the present invention,
Non-ferrous metal separation and recovery using induced current is adopted. This is a method that has been used for sorting aluminum cans. However, since the magnetic force is insufficient (about 1000 gauss) if it is diverted as it is, the magnetic force used to fill the drum must be 2,000 to 3,000.
This is a method in which the number of poles is increased to twice or more from 16 poles in general and the number of poles is increased to about 3000 rpm instead of the one usually used at 1500 to 1800 rpm. The present inventors have made various improvements and repeatedly conducted experiments on the removal of non-ferrous metals. As a result, in the separation test of the incineration residue from which iron was completely removed, when the weight ratio of non-ferrous metals in the sample was 50%, the separation rate was 75-85%, also the non-ferrous metal weight ratio in the sample is 100%
In the case of, a separation rate of 83 to 87% was obtained. Here, non-ferrous metals that cannot be separated are mainly bolts and nuts made of stainless steel, thick castings, and tangled copper wires, which have a relatively large shape, and are separated by a particle size after a pulverization step described later. It was confirmed that it could be removed with.

Next, regarding the uniform particle shape, the particle size of the non-metallic material obtained from the incinerated ash after removing the fine powder, irons and non-ferrous metals was compared with the standard particle size of JIS sand. An example is shown in Table 5 below.

[0018]

[Table 5]

Although ash is generally considered to be a fine powder, it has been found that the ash does not greatly deviate from the particle size analysis of the aggregate sand as shown in Table 5 above. That is, most of the incinerated ash has a required particle size as sand.

However, the shape of the particles other than the particle size is a problem. For example, small pieces of glass or porcelain may have sharp ridges and may be directly touched by workers as earth and sand for civil engineering. It must be machined into a round shape without danger. Therefore, the inventors divided the obtained non-metallic substance into two by particle size, crushed the coarser one with a crusher, and crushed the finer one and the one that passed through the crusher together. The crusher and polisher are not instantaneous crushers, but rod mill types that can adjust the processing time.
Further, in consideration of the interchangeability of parts, the crusher and the polisher were of the same size and the same type. Finally, regarding the fact that the chloride content has been reduced and the amount of heavy metal eluted below the specified value, the inventors have determined that chloride and elution with acids such as sulfuric acid and water. A method was selected in which the soluble heavy metals were dissolved as much as possible or converted into a compound having extremely low water solubility by reaction with an acid. Initially, chloride was predicted to be sufficiently removed by washing with a large amount of water.However, the amount of Cl did not fall below 0.4%. This is because chlorine is a compound other than highly water-soluble salts such as NaCl and KCl. Inferred. This is the reason why I came to think of decomposing hardly soluble chlorides with some chemicals. FIG. 1 shows the residual Cl amount when the incinerated ash was washed with water and dilute sulfuric acid. It was revealed that the treatment with the acid was effective in reducing the elution of heavy metals as the experimental analysis was repeated. Here, the following table shows the allowable elution amount of heavy metals.

[0021]

[Table 6]

The above values are reference values in the spring of 1995, and the PB has been revised to a very severe value from 1994. The goal of the inventors to reduce the elution of incinerated ash is:
The value was set to be equal to or less than the environmental standard value related to the most severe soil pollution in Table 6 above. Recently, in the collection of municipal solid waste, the separation and cooperation of the residents has progressed, and the contamination of Hg, Cd, and Cr has been extremely low, and the amount of the incinerated ash eluted has become sufficiently low. The problem is Pb. The inventors continued various experimental researches and analyzes on this Pb countermeasure. As a result, it was confirmed that the target could be achieved. FIG. 2 shows the experimental results for lead. In order to reduce the amount of washing water and acid as much as possible and economically treat it, it is necessary to soak the incinerated ash in chemicals for several hours, but if it is soaked for 10 to 24 hours, it may fall below the strict standard value. confirmed. The dissolution test results of each heavy metal in the final product are shown in Table 7 below.

[0023]

[Table 7]

As the acid, hydrochloric acid besides sulfuric acid can be used in this treatment method, and sodium hydrogen sulfide is effective in a small amount and can be used in this treatment method.

[0025]

The present invention will be described in more detail with reference to the following examples. FIG. 3 is a schematic diagram showing an example of a facility for treating incineration ash discharged from the stalker incinerator of the present invention. The coarse piece removing device 1 removes large metal pieces contained in the incinerated ash, for example, kettles, pots, tire wheels, pearls, and the like, as well as metal clumps that are melted and solidified in a clinker shape due to high temperature. This is for protecting the equipment.

The incinerated ash that has passed through the coarse piece removing device 1 then enters the roasting device 2. In the case of wet ash, the incinerated ash contains 15 to 30% of moisture, and the roasting device 2 has the following purpose in addition to drying the incinerated ash.

[0027] The unburned organic matter is carbonized, and the malodor source substance is decomposed. Increase separation efficiency in subsequent processing steps. Decomposes dioxin. In order to achieve the purpose of ~, incineration ash should be 300 ~ 500 ℃
It must be heated and roasted, but the incinerated ash contains a lot of fine particles and is blown away when exposed directly to hot air. Therefore, the inventors devised and put into practical use a device for indirectly heating incineration ash from outside the kiln in a closed kiln. In addition, the kiln is inclined so that the roasting time can be adjusted, and the incineration ash is lifted up by the fins provided on the inner periphery of the kiln so that it can be sent out at the same time. Controllable. The heat source of the roasting device is combustion of gas or fuel oil, but the amount of combustion can control the internal temperature of the kiln. Next, the incinerated ash that has exited the roasting device is cooled by cold air, and then fine particles are removed by the fine particle removing device 3, irons are removed by the irons separator 4, and metals other than iron are removed by the non-ferrous metal separator 5. Separate and remove. The fine particle removing device 3 blows off fine powder by wind power. The iron separator 4 allows any iron to be adsorbed and separated by magnetic force by the rotating magnetic force charged to the pulley of the conveyor belt. The non-ferrous metal separator is based on the principle of releasing non-separated materials by induced current.However, in order to reliably release non-ferrous metal pieces having various shapes, the magnetic force of the magnet is increased and the rotation speed is increased. increase of,
Modified the belt conveyor belt thickness and speed, etc.
The separation efficiency was dramatically improved. The incinerated ash from which fine particles, irons and non-ferrous metals have been removed as described above is used as a raw material for reclaimed sand. However, it is difficult to handle because the particles having a too large particle diameter and sharp fragments of glass and ceramics are mixed. Therefore, after the raw material is sieved 11 and divided into coarse and fine, the coarse is finely crushed by a crusher 12 It has become. Granulated incineration ash, however, still contains water-soluble salts and very small amounts of heavy metals,
Cannot be used as general material. Therefore, the incineration ash treated by the polishing machine 14 is sufficiently dissolved and eluted by the acid solution such as dilute sulfuric acid in the chemical solution treatment device 16 with the heavy metal dissolved by the acid.
Alternatively, the solubility of heavy metals in the final product was reduced by using a sulfate having extremely low water solubility. The target value is below the strictest allowable standard value of the Environment Agency, and the type of acid and its concentration,
An adapted value for the elution time was obtained. The incinerated ash that has been treated with the chemical is finally washed with neutral water in a washing device 17 and stored in a product hopper 18 as a product. As a result of the treatment by the above treatment equipment, the dioxin content and the dissolution rate of the dissolvable heavy metals, which are the drawbacks that incinerated ash could not be used as general civil engineering materials, were extremely large as shown in Tables 3 and 7. We succeeded in reducing it. Although the waste liquid finally discharged from the torrefaction device 2 and chemical treatment apparatus 16, the waste is mainly salt (NaCl, KCl, CaCl _2, etc.) heavy metals eluted in addition are included many include. In this waste liquid treatment method, it is general that the solid phase body and dissolved heavy metals are reacted with an additive to precipitate and remove them, and the remaining salt water is discharged. After filtering the whole amount and removing only the solid phase, a method was employed in which the entire amount of the waste liquid was evaporated to recover salts and heavy metal compounds as powder. That is, the waste liquid discharged from the chemical liquid treatment device 16 and the exhaust gas cleaning device 22 is separated into solid and liquid by the water treatment device 19, the solid phase is dehydrated by the cake dehydrator 19, and the liquid phase is treated water evaporator.
At 21 all was evaporated. This method of evaporating the entire amount of waste liquid eliminates the need for expensive additives conventionally used for the precipitation treatment of dissolved metals, and eliminates the troublesome operation and maintenance of the waste liquid circulation system because all waste liquid is evaporated. The main functions and objects of the present invention have been described above. According to the present invention, the ratio of products obtained from incinerated ash is as follows. Incinerated ash 100% Iron about 10% Non-ferrous metals about 5 to 10% Washing and elution and burning unburned matter about 10% Defective fine particles during drying and grinding about 10 to 20% Reclaimed sand 50 to 60% Iron among the above , Non-ferrous metals and reclaimed sand are useful,
Therefore, 10 to 20% of the waste is disposed at the final disposal site as before.
This can greatly extend the life of the final disposal site.

[0028]

As described above, according to the method for reusing incineration ash from the stalker-type waste incinerator of the present invention having the above-described configuration, the incineration ash currently disposed of at the final disposal site Of non-ferrous metals that can be used as recycled sand for civil engineering in addition to the recycling of ferrous and non-ferrous metals, and as a result, incineration ash disposal transported to final disposal sites The volume can be reduced to 10 to 20% of the conventional amount, and the waste disposal cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a washing time and a residual salt content when incinerated ash is washed with water and dilute sulfuric acid.

FIG. 2 is a graph showing the relationship between shaking time and lead elution amount of incinerated ash after treatment with water and dilute sulfuric acid.

FIG. 3 is a schematic view showing an example of an incineration ash treatment device used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coarse-piece removal apparatus 2 ... Roasting apparatus 3 ... Particle removal apparatus 4 ... Irons separator 5 ... Non-ferrous metal separator 6 ... Raw material hopper 7 ... Coarse piece hopper 8 ... Particle hopper 9 ... Iron scrap hopper 10 ... Non-ferrous metal Waste hopper 11… Sieve 12… Pulverizer 13… Sieve 14… Polisher 15… Sieve 16… Chemical solution treatment device 17… Cleaning device 18… Product hopper 19… Water treatment device 20… Cake dewatering device 21… Treatment water evaporator 22… Exhaust gas cleaning equipment

Claims (1)

(57) [Claims] The present invention relates to a method for recycling metals from incinerated ash discharged from the bottom of a stoker-type incinerator for waste and for recycling nonmetallic substances. After removing coarse pieces such as ingots, (2) the incinerated ash placed in the rotary kiln is
A roasting step of roasting at 300 to 500 ° C. by heating from the outer periphery of the sorting step of removing fine powder, ferrous metals, non-ferrous metals (3) the ash, (4) said residue Ride Certain non-metallic substances are divided into two by particle size,
A stalking type incinerator characterized by performing a pulverizing / polishing step of polishing and processing into particles, and (5) a chemical liquid treatment step of subjecting the granulated residue to chemical treatment with diluted sulfuric acid or the like and then washing with water. Ash recycling method.