JPS5821551B2 - Method for solidifying dry waste containing hazardous pollutants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for solidifying dry waste containing hazardous pollutants, and in particular to a method for solidifying municipal waste incineration ash, electrostatic precipitated dust, etc. with increased water resistance. It is.

Cd and Pb are found in municipal waste incineration ash, electrolytic dust, etc.
They often contain harmful heavy metals such as

However, these dry-processed wastes contain components that react with water, and if they come into contact with rainwater or groundwater after being landfilled, or with seawater during ocean dumping, these components may react with water. This causes a reaction with the solidified molded product, causing a decrease in the strength of the solidified molded product, and causing harmful contaminants to be leached from cracks and damaged areas.

For example, Na2 is contained in electrostatically collected dust from municipal waste incinerators.
It contains oxides such as O and CaO, and metals such as AI, and these substances cause the following reaction with water.

In the case of the above formula (1), a mechanically extremely fragile substance called Ca(OH)2 and heat are generated, and in the case of the formula (2), H2 gas and heat are generated.

These substances, gas, heat, etc. have a synergistic effect, lowering the mechanical strength of the solidified molded product, and causing cracks and
This results in damage and the elution of harmful contaminants such as Cd and Pb.

An object of the present invention is to provide a method for solidifying dry waste as described above, which does not cause a significant decrease in water resistance and prevents the elution of harmful pollutants.

According to the present invention, the above purpose is to react the waste containing hazardous pollutants with water before solidification, and to complete the reaction that produces substances, gases, heat, etc. that reduce mechanical strength. This is achieved by adding a processing step.

The present invention will be explained in detail below.

The present inventor discovered the fact that, after solidification, when the solidified molded products are buried, dumped in the ocean, etc., components that react with water that are contained in these solidified molded products cause a special reaction with water. After discovering that this is the cause of lowering the mechanical strength of solidified molded products, we considered pretreatment as one method to eliminate this cause.

That is, better results will be obtained if the reaction of the component that reacts with water is completed in advance and then solidified.

Therefore, we mixed water and waste while changing the mixing ratio (weight ratio) of dry waste and water, solidified this, and investigated the crushing strength of the solidified molded product after immersing it in water. I saw it.

As a result, the results shown in FIG. 1 were obtained.

The product shown in Figure 1 is pre-treated while changing the mixing ratio with water, and after the reaction with water is complete, this is dried, then kneaded with asphalt, and this is formed into a cylindrical shape. This shows the case where a crush test was conducted after immersing the sample in water for 7 days.

As is clear from the diagram in Figure 1, when the mixing ratio of water (mixed amount of water to 100 parts of waste...%) is increased (as shown by curve A), the crushing strength is increased. was significantly increased, and when the mixing ratio was 50%, a large strength of 200 kg/crA was obtained.

In comparison, it was found that the solidified molded product obtained by the conventional method in which no pretreatment reaction was performed with water had a significantly lower crushing strength as shown at point B.

On the other hand, as a result of conducting a Cd and PB elution test in parallel with the crushing strength test, the results shown in FIG. 2 were obtained.

As is clear from the diagram in Figure 2, as the mixing ratio of water increases, the amount of elution decreases, and it becomes clear that there is a large correlation between this and mechanical strength, which is a satisfactory result. Obtained.

By the way, from the above results, it is clear that the more water is mixed, the better the results are produced, but the problem lies in the drying process after the reaction with water, and the drainage equipment, drying equipment, and usage. The optimum water mixing ratio should be selected in consideration of the energy used and in relation to economic evaluation and purpose.

As is clear from the above explanation, according to the present invention, before solidifying dry waste containing hazardous pollutants with asphalt, a reaction between a reactant with water in the waste and water is performed as a pretreatment step. Because we add a processing step to complete the process, there is no reaction with water after solidification and dumping (no brittle substances, no gas, no heat, etc. are generated, and the mechanical strength is improved and no harmful It has excellent effects because it can dramatically reduce the amount of pollutants eluted and significantly improve water resistance.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the relationship between the water mixing ratio in the pretreatment process of the solidified molded product obtained by the method of the present invention and the crushing strength after molding, and Figure 2 is the same (water mixing ratio and elution strength). It is a diagram explaining the relationship with quantity.

Claims (1)

[Claims] 1 In a method of kneading dry waste containing hazardous pollutants with asphalt and solidifying it into a predetermined shape, the waste and water are mixed and reacted with water before the dry waste is kneaded with asphalt. A method for solidifying dry waste containing hazardous pollutants, which comprises drying and kneading with asphalt after completing the reaction of the components.