JP3440246B2 - Waste residue treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for safely disposing of a metal halide-containing waste residue in a reusable state.

[0002]

2. Description of the Related Art Incinerated ash, which is a residue generated when combustible waste is incinerated, and sludge, which is a residue generated when processing various industrial wastes, contain harmful heavy metal oxides and chlorides. Often included.

For example, paper, textiles,
When combustible wastes such as plastics, garbage and various synthetic chemical substances are incinerated in a cleaning plant incinerator, calcium oxide etc. are used to capture harmful hydrochloric acid gas generated from vinyl chloride plastics etc. Although added, this calcium oxide becomes calcium chloride and remains in the incineration ash.

However, although there are differences in the incineration ash depending on the composition of the waste, the incineration temperature, etc., harmful heavy metals such as mercury, lead, cadmium and zinc, which are originally contained in a considerably high concentration, are oxidized. It exists as compounds such as compounds and chlorides. If the content of such heavy metals is below the standard value, it can be dumped as it is to landfills, etc., but even if the content of residue per unit weight is very small, the total amount due to mass dumping will be a certain large amount. It is clear that it has reached and is not desirable. In particular, the fly ash separated and collected from the exhaust gas of the incinerator contains a high concentration of harmful heavy metals as chlorides that are easily dissolved in water, and cannot be discarded as it is or reused.

On the other hand, cement mortar is used as a method for treating incineration ash and sludge containing a metal halide such as the above-mentioned heavy metal chloride which is easily dissolved in water, particularly as a method capable of treating it in a reusable state. It is recognized that it is made into concrete, solidified with an admixture such as a polymer substance, vitrified or sintered by applying high heat.

However, when building and building materials such as blocks and panels are produced by these methods and provided as so-called recycled products, the heavy metal compounds contained therein are those produced by the first and second methods. However, there is a problem that it is likely to be easily eluted by rainwater and pollute the environment. Further, the third method has a problem that harmful hydrochloric acid gas is generated by thermal decomposition to corrode equipment or pollute the atmosphere.

[0007]

The problem to be solved by the present invention is that the conventional method, which is accepted as a method for treating waste residues so as not to elute harmful heavy metals, completely elutes even when solidified. However, there is a problem of environmental pollution that cannot be prevented, and if vitrification or sintering is measured, not only is it economically disadvantageous to the facility, but it also causes the problem of generating harmful gas and polluting the atmosphere. Alternatively, there was no reliable and pollution-free means of processing into a reusable state.

[0008]

The present invention solves the above problems and ensures that waste residues containing water-soluble metal halides, especially metal chlorides, can be safely dumped or treated in a reusable state. The purpose of the present invention is to provide a non-polluting means, in which the waste residue is made into a dry powder form and mixed with a powder of a metal oxide, and the mixture is heated while aerating steam to heat the metal. It was decided to decompose the halide.

The metal halide is decomposed by heat to generate halogen hydrogen gas, which is trapped by water vapor and therefore can be safely recovered as halogen hydrogen water by cooling and condensing the water vapor that has passed through the mixture. Become.
In addition, most of the metal produced by decomposition becomes an insoluble oxide in water, and even if it remains in the treated product as it is, it will not elute due to rainwater, etc., so it is safe to dispose of in landfills. is there. Furthermore, even if the treated product is solidified with cement mortar, polymer substance or the like and recycled as a building or building material, it can be used outdoors without fear of environmental pollution for the same reason. Furthermore, since no harmful gas is generated during the high heat treatment to a reusable state by vitrification or sintering, the treatment can be performed without causing equipment corrosion or air pollution.

When the waste residue is incinerated ash, it can be treated as it is because it is already in the form of dry powder. However, if the waste residue is a sludge containing water such as a sediment produced at the final sewer treatment plant, it is dried by sun or by low-temperature heating to evaporate the water and crush it into powder. , Pretreatment is required.
The pretreatment is carried out at a temperature low enough to evaporate water, so that the metal halide remains without being decomposed.

By thus forming a dry powder,
The powder of the metal oxide that acts as a catalyst for promoting the decomposition can be uniformly mixed, and the steam can be evenly contacted and passed. As the metal oxide, aluminum oxide, ferric oxide, and tungsten oxide are exemplified as preferable substances, and one or more of these are added and used.

The waste residue and the metal oxide are mixed in a ratio (weight ratio) of the former to the latter in the range of 9: 1 to 2: 8, preferably 9: 1 to 5: 5. Good. That is, if the metal oxide content is less than 10% by weight, the absolute amount with respect to the waste residue is insufficient and a sufficient effect cannot be obtained. Also,
It is effective to increase the ratio of metal oxides, but if the ratio is more than a certain level, the effect is not proportional and it is useless.
It is economically preferable to set it to 0% or less.

Further, the steam to be aerated in the mixture is equivalent to 1 to 10 L in terms of condensate with respect to 1 kg of waste residue, and the heating temperature is 600 ° C. or higher, which is capable of actively decomposing metal halides in the presence of a catalyst, preferably Is 600 to 1100
It shall be in the range of ° C. By maintaining this heating temperature range for 0.5 to 6 hours, preferably 1 to 3 hours while aerating water vapor, the metal halide is completely decomposed even if it is contained at a high concentration and The generated halogen hydrogen gas can be almost completely captured and recovered. During this time, the mixture may be allowed to stand, but by appropriately stirring it, the contact with the steam can be equalized and the efficiency can be improved. That is, the higher the heating temperature is, the more effective the heating temperature is.
The temperature is preferably 100 ° C or lower. Further, it seems that a longer heating time is effective, but it is preferable to keep the heating time within 3 hours because even if the heating time is long, the one whose decomposition is almost completed is continued to be heated.

The condensate of water vapor in which halogen hydrogen gas is captured is mainly an aqueous solution of hydrochloric acid, and harmful gas such as hydrogen chloride gas is recovered without being diffused into the atmosphere and volatilized.
Emitted mercury and the like are also recovered in this aqueous solution, and cadmium, lead, zinc and the like can be recovered as harmless oxides.

The treated waste residue contains metal oxides produced by decomposition of metal halides and metal oxides added as catalysts, but most of these are insoluble in water. If the harmful heavy metal content is below the standard value, it can be discarded as it is. In addition, solidification, vitrification,
It is extremely safe because it does not release or elute harmful substances during use and processing when it is reused after sintering .

FIG. 1 schematically shows an example of equipment for carrying out the treatment according to the present invention, in which a treatment chamber 2 is provided inside a heating furnace 1 such as an electric furnace to dispose of waste residues and metal oxides. One or two or more dish-shaped containers 4 in which the mixture 3 of and is placed thinly are placed, and a steam introduction pipe 6 and a condenser 7 extending from a steam generator 5 are provided at both ends of the processing chamber 2. This is a configuration in which all the collecting tubes 8 are connected.

The mixture 3 is treated with the amount of steam permeation, the heating temperature and the heating time described above, and the aqueous solution of halogen hydrogen condensed in the condenser 7 is stored in the recovery container 9 for further use or disposal.

[0018]

[Examples] A predetermined amount of incineration ash generated in an incinerator of an urban cleaning plant and sludge that is a sediment generated in a sewer final treatment plant are dried in the sun and aluminum oxide that is a decomposition accelerator is sufficiently added. Samples were prepared by crushing and mixing, and compared with samples consisting only of incinerated ash and sludge. The blending ratio (weight ratio) of each sample is as shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

5 g of the sample was placed in a magnetic dish, and 1000
It was placed in an electric furnace that had been heated to 0 ° C., and kept at 1000 ° C. for 6 hours while ventilating steam. The total flow rate of water vapor is 1500 cc in terms of condensate. For the filtrate obtained by adding dilute nitric acid to the treated sample and heating it to dissolve the chloride and filtering it, measure the residual chloride ion amount using the chloride ion electrode method and an automatic titrator using a silver nitrate solution as the titrant. The results shown in Tables 3 and 4 were obtained.

[0022]

[Table 3]

[0023]

[Table 4]

From these, the catalyst metal oxide 10
It was found that halogen, particularly chlorine, which is a harmful gas, can be separated and removed almost completely by adding more than the weight ratio. If the amount exceeds 50% by weight, the effect is almost leveled off. Therefore, considering the economical efficiency, the addition range of the metal oxide is 10-5.
It has also been found that a 0 weight ratio is preferred.

Next, Table 5 shows the measurement results of the amount of residual chlorine ions when the heating temperature was changed using a sample in which the weight ratio of aluminum oxide was 20. However, the heating time is 6
It's time. From this, it was found that the higher heating temperature is more effective.

[0026]

[Table 5]

Table 6 shows the measurement results of the residual chlorine ion amount when the heating time was changed using a sample in which the weight ratio of aluminum oxide was 20. However, the heating temperature is 1
It is 000 ° C. Therefore, in order to almost completely separate and remove chlorine, heating for 1 hour or more is required, but even if it is heated for a long time, the effect is hardly improved. It turned out to be good time.

[0028]

[Table 6]

Further, Table 7 shows the measurement results of the amount of residual chlorine ions when the amount of aeration of water vapor was changed using a sample in which the weight ratio of aluminum oxide was 20. However, the heating temperature is 10
The heating time is 00 ° C. and the heating time is 6 hours. From this, it was found that the larger the amount of vapor permeation, the more effective.

[0030]

[Table 7]

[0031]

As is apparent from the above description, a metal halide which is dissolved in water or thermally decomposes to cause environmental pollution is thermally decomposed using a metal oxide as a catalyst which does not cause environmental pollution. According to the present invention in which halogen hydrogen gas is captured by water vapor, it is possible to separate metal halide into metal oxide and halogen hydrogen gas with extremely high efficiency, and to safely recover the gas without releasing it into the atmosphere. It can be processed into. And
The waste residue treated according to the present invention is safe to discard as it is because the water-soluble and heat-decomposable metal halides are decomposed and removed, and is also processed and used for reuse. It's safe.

[Brief description of drawings]

FIG. 1 is a layout diagram of an example of equipment for implementing the present invention.

[Explanation of symbols]

1 heating furnace, 5 steam generator, 7 condenser,

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B09B 3/00-5/00 C02F 11/00-11/20

Claims (3)

(57) [Claims] 1. A waste residue, characterized in that the waste residue is made into a dry powder form, and a powder of a metal oxide is added to and mixed with the waste residue, and the mixture is heated while aerating steam to decompose the metal halide. Processing method. 2. A dry powdery waste residue and a powdered metal oxide are mixed in a weight ratio of 9: 1 to 5: 5, and 60
The processing method according to claim 1, wherein the heating temperature is maintained at 0 to 1100 ° C for 1 to 3 hours. 3. The processing method according to claim 1, wherein the metal oxide is one kind or two or more kinds of aluminum oxide, ferric oxide, and tungsten oxide.