JPH0824831A - Metal recovery method from fly ash - Google Patents

Abstract

(57) [Summary] [Purpose] Metals contained in fly ash generated when shredder dust from abandoned automobiles, home electric appliances, etc. is incinerated and reduced in volume are efficiently separated and collected. [Structure] After washing fly ash with water to elute and remove chlorine ions, and then attributing the separated dechlorinated fly ash slime,
Metals are separated and collected by flotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering metals from incinerated fly ash as a technique for recycling waste. More specifically, it relates to a method for recovering metal from fly ash generated when incinerating and reducing the volume of shredder dust after crushing scrapped automobiles, waste home electric appliances, etc. with a shredder to recover metal, and effective use of fly ash. Is.

[0002]

2. Description of the Related Art Increasing amounts of various kinds of waste and this disposal method have become a social problem as an adverse effect on the development of the consumption economy in recent years. At present, large shells such as body shells, electric washing machines, electric refrigerators, etc. after scrapping and collecting valuable parts from scrapped automobiles are crushed by shredders, and iron and non-ferrous metals are collected, but these are collected. The shredder dust, which is mainly made of plastics, is disposed of by landfill.

However, the amount of industrial waste and household waste is increasing, and it is becoming more and more difficult to secure the landfill site due to the problems of saturation of existing landfill sites and environmental pollution. Therefore, recycling of waste and reduction of volume are required. Incineration power generation is being studied as a method for recycling and reducing the volume of the shredder dust. That is, it aims to recover and utilize the thermal energy generated by the combustion of plastics, which occupy the main part of shredder dust, by heat exchange in a power generation boiler or the like, and also to reduce the volume as incinerated ash.
The incineration ash generated when this shredder dust is incinerated includes bottom ash (bottom ash) and fly ash (fly ash) that is contained in the combustion waste gas and is collected by a capturing means such as a filter. is there.

Common fly ash, such as coal ash, is reused and disposed of by aggregates, cement raw materials, landfill disposal, stabilization treatment (pelletization) and the like. Fly ash obtained by incinerating shredder dust, etc. contains many chlorine compounds and metals derived from plastic such as polyvinyl chloride. It cannot be used due to problems such as corrosion and environmental friendliness, and even if it is landfilled, there is a risk of salt damage due to elution of chlorine from the landfill site due to acid rain, etc. There is fear. Furthermore, from the viewpoint of resource reuse, it is desired to recover metal components from fly ash.

In Japanese Patent Laid-Open No. 49-113703, while maintaining the diluted sulfuric acid eluate of incinerated ash at pH 2.0 to 3.0, sodium sulfide in an amount equal to or higher than the concentration of metal ions contained is added to make it other than iron. Metal is coagulated as sulfide, then polymer flocculant is added to form metal sulfide floc, and amine collector and polypropylene glycol ether foaming agent are added for air supply. It has been proposed that the metal sulfide flocs are levitated as scum and collected. However, the surface of the metal particles present in the incineration ash is oxidized, and since many chlorine compounds are present in the incineration ash, it is not possible to capture a sufficient amount of metal in the form of sulfide, and , It was difficult to collect sulfide efficiently by flotation.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for removing fly ash generated when incinerating waste such as shredder dust.
It is an object of the present invention to provide a method for efficiently and easily separating and recovering various metals.

[0007]

SUMMARY OF THE INVENTION The present inventors have
The surface of the metal particles present in the incinerated ash is oxidized,
Focusing on the fact that the presence of such metal oxides on the surface of particles reduces the efficiency of iron recovery by magnetic separation or the recovery of other heavy metals by flotation, as a result of intensive research, the results showed that fly ash By subjecting the dechlorinated fly ash slime, which has been separated after washing to remove chlorine ions with water, to attrition, the oxides on the surface of the metal particles are scraped off by collision and friction between particles at this time, and the unoxidized metal is removed. We obtained new knowledge that it can be exposed and that the subsequent flotation or magnetic separation can be efficiently performed.

That is, the first invention is a method for recovering metal from fly ash generated when waste is incinerated, and the fly ash is washed with water to elute and remove chlorine ions. It is a method for recovering metals from incinerated fly ash, which comprises separating and recovering metals by flotation after attrition of slime.

A second invention is a method for recovering metal from fly ash generated when waste is incinerated, wherein the fly ash is washed with water to elute and remove chlorine ions, and the dechlorinated fly ash is separated. Metals from incinerated fly ash characterized by separating and recovering magnetic metals by magnetic separation after attributing slime, then further non-magnetic residual components are separated, and then separating and collecting nonmagnetic metals by flotation. It is a collection method.

[0010]

The present invention will be described in detail below by taking as an example a series of treatment processes of shredder dust from abandoned automobiles and abandoned home electric appliances which incorporate the method for recovering metals from incinerated fly ash according to the present invention.

First, after disposing of reusable parts of scrapped automobiles and scraps of household electric appliances, they are crushed by a shredder according to a conventional method to collect ferrous and non-ferrous metals. The shredder dust, which is mainly made of plastic after recovery, is burned to reduce the volume, but 1000 ° C or lower in order to prevent generation of harmful components such as dioxins due to burning.
More preferably, for example, a fluidized roasting furnace or a grate furnace is used so that it can be incinerated at a temperature of 700 to 900 ° C. The heat energy generated at this time is heat-exchanged and recovered in the power generation boiler. In addition, during this combustion, a large amount of chlorine is generated due to plastic such as polyvinyl chloride, but shredder dust 100 is generated during incineration.
By adding about 5 to 30 parts by weight of slaked lime or limestone to parts by weight and fixing chlorine as calcium chloride (CaCl2), the release of harmful chlorine gas is prevented. Then, the bottom ash, which has been reduced in volume after incineration and remains in the furnace, is subjected to a recovery process of contained metal.

On the other hand, the fly ash contained in the combustion flue gas is captured and collected by a dust collector, which is provided in the middle of the flue and is composed of a filter or the like. The average particle size of this fly ash is about 0.1 to 10 μm, and particles of 1 to 8 μm account for 30 to 70% of the whole. And, as described above, a large amount of chlorine component (CaCl ₂ ) and metals are present in this fly ash.

In the present invention, the fly ash is first washed with water in order to remove chlorine components from the fly ash. Washing with water is usually performed using 1 to 10 times the volume of fly ash and leaching time of about 0.1 to 2 hours. CaCl ₂ can be easily dissolved and removed by such a treatment, but in order to shorten the leaching time, carbon dioxide gas is dissolvedly added to the wash water, for example, the pH is maintained at 6-9. It may be carried out under the condition of being added to the extent that it is added, or may be stirred.

Then, for example, after a predetermined leaching time in a sedimentation tank or the like, an overflow fraction and a sedimentation fraction of the fly ash slurry are separated to obtain dechlorinated fly ash slime having a water content of about 10 to 40% by weight. The overflow fraction containing a large amount of dissolved calcium chloride is carried to the step for recovering calcium chloride.

The dechlorinated fly ash slime that has been separated and agglomerated is then subjected to attrition. Attrition is performed by using a pulverizer such as a ball mill, a tower mill, and an attrition machine, and lumps are crushed to have an average particle size of 0.1 to 8 μm and 1 to 6
The water content is 30-
It is made into a powdery material of about 50% by weight.

The condition of the attrition is not particularly limited, and depends on the type of the crusher used and the like, but it is preferably about 1 to 24 hours. The metal particles contained in the fly ash slime are in a state where the nuclei of the metal particles remain metal, but the surface of the metal particles is oxidized to be a metal oxide. Such metal particles having a metal oxide layer on the surface are scraped away from the oxide layer on the surface by repeating collision and friction with other particles in the above-mentioned attrition to remove the unoxidized metal portion. Expose.

After performing the attrition in this manner, the dechlorinated fly ash is subjected to magnetic separation to separate magnetic metals such as iron. For the magnetic separation, a wet magnetic separation machine such as a commonly used high magnetic force separation can be used. As described above, since the surface oxide layer of the metal particles is removed by the attrition and the agglomeration of the particles is dissociated, the magnetic metal is recovered at a high yield, specifically about 50 to 90%. be able to.

Subsequently, the nonmagnetic residual component separated from the magnetic metal by such magnetic separation is further subjected to attrition. This attrition is also carried out using the same apparatus as described above, and the non-magnetic metal particles in the non-magnetic residual component are repeatedly scraped and rubbed against other particles to scrape off the surface oxide layer again. Expose the oxidized metal.

The condition of the attrition is not particularly limited, and it depends on the kind of the crusher used and the like, but it is preferably carried out for about 1 to 24 hours. Note that the magnetic metal recovery process by magnetic separation described above can be omitted if the content of magnetic metal in fly ash is predicted to be low due to sources such as incinerated shredder dust. In this case, the conditions suitable for the flotation as described above are directly adjusted by the attrition after removing the chlorine component by washing with water.

The nonmagnetic residual component thus attrited is subjected to flotation according to a conventional method to obtain copper,
Recover non-magnetic metals such as zinc. That is, the non-magnetic residual component is suspended in water in an amount of 3 to 6 times the volume of the non-magnetic residual component, a predetermined foaming agent and a scavenger are added, and air is blown to make the target non-magnetic metal. Only particles are floated together with bubbles and beneficiated. Pine oil, MIBC, polyglycol, etc. may be used as a foaming agent for obtaining the copper concentrate. Further, as the scavenger, xanthates, yellow floats and the like can be used. To obtain zinc concentrate,
In addition to these foaming agents and collectors, copper sulfate is required as an activator. Further, the amount of the foaming agent and the scavenger used depends on the types of the foaming agent and the scavenger used,
5-100 mg / kg of non-magnetic residual components
And about 10 to 1000 mg. As described above, since the surface oxide layer of the metal particles is removed by the attrition, it is possible to recover the non-magnetic metal in a high yield by the flotation, specifically, a yield of about 40 to 90%. it can.

The tailings after the non-magnetic metals are recovered by flotation are stable because chlorine ions and metals are removed. Therefore, it is of course not a problem to dispose of them, but silicic acids are not a problem. Since it contains a large amount, it can be reused as a raw material for cement, a processing raw material for heat insulating materials, and the like.

The method of the present invention has been described above by taking as an example the case of fly ash produced by incineration of shredder dust from abandoned automobiles and household electric appliances. The method for recovering metal from fly ash according to the present invention is as follows. The same applies to the treatment of fly ash generated when other wastes are incinerated.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples. Approximately 2 kg of fly ash generated when fluidized and roasted shredder dust from an abandoned car at about 850 ° C
A chlorine slime was dissolved and removed by washing and leaching with 0 volume of water for 0.5 hours to obtain a washed slime. The contents (grade%) of Fe, Cu, Zn and silicate insolubles contained in this washed slime were analyzed by chemical analysis, and the results are shown in Table 1.

Next, the wash slime was made into a homemade attrition machine (4 blades, 2 stage impeller, peripheral speed 300 m).
/ Min) and the attrition was performed for about 5 hours. The temperature during attrition starts from room temperature, but rises with the attrition time. Next, the crushed dechlorinated fly ash particles were subjected to magnetic beneficiation by a wet magnetic beneficiation machine (manufactured by Japan Elise Co., Ltd., model name HIW) to remove the iron components present in the washing slime as shown in Table 2. About 72% by weight could be separated and recovered as iron scrap.

Subsequently, the non-magnetic residual component separated from the iron scrap by magnetic separation is further treated by the same device as described above.
The mixture is again subjected to attrition for about 5 hours, and the nonmagnetic residue after the attrition is suspended in 4 volumes of water, and MIBC as a foaming agent and potassium butyl xanthate as a scavenger are added per 1 kg of the nonmagnetic residual components. 20m
g and 300 mg, and further add copper sulfate to 50
After the addition of 0 mg, a copper concentrate was obtained by air flotation. The Cu grade in this copper concentrate is 25% by weight,
The recovery rate for the copper component existing in the washed slime was as high as about 70%. The zinc grade in this sample was low (about 0.8% by weight in the wash slime).
Therefore, the zinc concentrate was not separated.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

As described above, according to the present invention, the fly ash is washed with water to remove chlorine, and then the metals in the fly ash are recovered by magnetic separation and flotation after attrition. Therefore, each metal in the fly ash can be easily separated and recovered in high yield, which enables a high degree of resource reuse in waste, and is expected to make significant progress in terms of environmental conservation. It is something.

Claims (2)

[Claims] 1. A method for recovering metals from fly ash generated when waste is incinerated, wherein the fly ash is washed with water to remove chlorine ions and the separated dechlorinated fly ash slime is attrited. A method for recovering metals from incinerated fly ash, characterized in that metals are separated and recovered by flotation. 2. A method for recovering metal from fly ash generated when waste is incinerated, wherein the fly ash is washed with water to elute and remove chlorine ions, and the separated dechlorinated fly ash slime is attrited. A method for recovering metals from incinerated fly ash, characterized in that magnetic metals are separated and recovered by magnetic separation, after which nonmagnetic residual components are attrited, and then nonmagnetic metals are separated and recovered by flotation.