JPS5850784B2 - Methods for treating industrial waste containing hazardous pollutants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating industrial waste containing harmful pollutants. The present invention relates to a method of solidifying industrial waste such as dust ash containing harmful pollutants using asphalt.

When industrial waste containing hazardous pollutants such as cadmium, lead, and hexavalent chromium is to be landfilled or dumped into the ocean, it is necessary to dispose of it in a way that prevents the hazardous pollutants from leaching out.

A solidification treatment method is one of the treatments for preventing the elution of harmful pollutants.

The solidification treatment method is a method in which industrial waste is coated with an inert medium and solidified.

Typical solidification methods include the cement solidification method, which uses cement as an inert medium, and the asphalt solidification method.

The asphalt solidification method involves mixing industrial waste with asphalt, covering the surface of the industrial waste with asphalt, and solidifying it.

To carry out the asphalt solidification method, conventionally, waste is generally fed into a kneading machine equipped with a heating device, heated to around 100°C, and then asphalt molten at 150 to 200°C is added separately and thoroughly kneaded. After that, the kneaded material was solidified using a compression molding machine.

In the asphalt solidification method, it is necessary to knead waste and asphalt so that the surfaces of waste particles are completely covered with molten asphalt.

For this purpose, use a suitable mixer, allow sufficient mixing time, and increase the mixing ratio of asphalt to transfer the solid-liquid system consisting of waste particles and asphalt from the capillary region to the sticky or slurry region. It needs to be mushy.

However, it is impossible to compression mold a kneaded material in the state of such a capillary region or slurry region.

Further, if the kneaded product is not compressed and then landfilled or dumped as a final treatment, many difficult problems arise in terms of handling.

Funicular region, capillary region, slurry (5lurry)
) area is a technical term indicating the filling state of a powder-liquid (-air) system (there is also a pendula area), and corresponds to expressions such as ``bushy'', ``sticky'', and ``mushy''.

On the other hand, when making mixed materials into a state where they can be solidified by a compression molding machine, that is, into a funicular state, the industrial waste is not completely covered with asphalt, and harmful pollutants often elute when it is buried or dumped. Solidified asphalt cannot be dumped into the ocean or landfilled.

The purpose of the present invention is to completely cover the surface of industrial waste particles containing harmful pollutants with asphalt, to suppress the elution of harmful pollutants to an extremely low value, and to provide a mixture of industrial waste and asphalt. An object of the present invention is to provide a method for treating industrial waste containing harmful pollutants, which can be solidified using a compression molding machine.

The method for treating industrial waste containing harmful pollutants according to the present invention involves kneading the industrial waste containing harmful pollutants with molten asphalt in excess of the amount suitable for solidification to form a capillary or slurry state. It is characterized by adding powder or granules that do not contain harmful contaminants and continuing kneading to create a funicular state necessary for solidification, and then solidifying.

The method of the present invention will be explained in detail below.

As mentioned above, in order to completely cover the surface of waste particles with molten asphalt, use an appropriate mixer, allow sufficient time for mixing, and increase the mixing ratio of asphalt. It is necessary to bring the solid-liquid system made of asphalt into a capillary state or a slurry state.

The state of the solid-liquid system consisting of waste particles and asphalt varies depending on the mixing ratio of asphalt, crosstalk time, particle size distribution of waste particles, viscosity of asphalt, surface tension, etc.

The state of this solid-liquid system changes from fluffy to sticky to mushy depending on the crosstalk time, and eventually reaches a constant state, but the greater the amount of asphalt added, the shorter the time it takes to reach a constant state.

FIG. 1 shows an example of the results of measuring the change in state of the mixed material depending on the kneading time when asphalt was added to the collected dust ash at various mixing ratios.

Table 1 shows the physical properties of the collected dust ash and asphalt used in this measurement.

In this test, the collected ash from the electric furnace shown in Table 1 was supplied to the crosstalk machine.
After heating to around 100'C, the modified asphalt shown in Table 1 melted at 150-200C was added.

As is clear from FIG. 1, the mixture containing 20% asphalt reaches a constant state after about 30 minutes of kneading, but the amount of asphalt added is reduced.

Therefore, it takes a long time for kneading to reach a certain state, and the one with 13% asphalt added takes about 120 minutes to reach a certain state.

Asphalt at a constant level of 13-15%
The added material is in a funicular state and has a content of 17-18%.
Those added are in a capillary state, and those added at 19 to 20% are in a slurry state.

FIG. 1 shows the results of measuring the elution concentration of harmful substances (hexavalent chromium) in the kneaded mixture of collected dust ash and asphalt that reached a certain state.

As is clear from FIG. 1, the concentration of hexavalent chromium eluted from the mixed substance in the funicular state is 1.0 ppm or more in dogs.

It can be proven from Figure 1 that a large amount of harmful substances are leached from the solid material by the conventional asphalt solidification method.

The elution concentration of hexavalent chromium from the kneaded product in capillary state is as low as 0.3 ppm or less.

However, as mentioned above, it is difficult to compression mold a mixed wire in such a state.

Therefore, in the method of the present invention, harmful pollutants are added to the mixture of waste and asphalt, in which the surface of the waste particles is completely covered with asphalt, and the waste particles are in a capillary or slurry state, and the elution concentration of harmful substances is extremely low. Add the powder or granules that do not contain the powder and continue kneading to obtain a funicular state suitable for solidification.

It is desirable that the added powder or granules do not contain harmful contaminants, do not dissolve in water, and are dry.

Examples include stone powder, calcium carbonate powder, foundry sand, etc.

As an example, 18% asphalt was added to the collected dust ash in Figure 1.
When 30% by weight of stone powder was added to the mixed wire in the capillary state and mixing was continued, compression molding became possible in the funicular state.

The eluted concentration of hexavalent chromium in the compression-molded solidified product was measured to be 0.2 ppm, which was almost the same as the eluted concentration of hexavalent chromium in the kneaded product before the addition of stone powder.

In addition, when 18 parts by weight of asphalt was added to a mixture of 100 parts by weight of collected dust ash and 30 parts by weight of stone powder and kneaded, it became a constant funicular state in about 1 hour.
Compression molding is now possible.

The elution concentration of hexavalent ROM in the compression-molded solidified product is approximately 1
It was ppm.

As is clear from the above explanation, in the method of the present invention, industrial waste containing harmful pollutants is first kneaded with excess asphalt to form a capillary or slurry state, so that the waste particles are completely covered with asphalt. This suppresses the elution of harmful pollutants.

Next, powder and granules that do not contain harmful pollutants are added to the mixture of waste and asphalt, and kneading is continued to create a funicular state, which can be solidified using a compression molding machine.
The amount of harmful pollutants eluted from the solidified material is extremely small.

Therefore, the method of the present invention is industrially useful.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the change in state of a mixture of industrial waste and asphalt at various mixing ratios depending on the kneading time and the elution concentration of hexavalent chromium.

Claims (1)

[Claims] 1 Industrial waste containing harmful pollutants is kneaded with molten asphalt in excess of the amount suitable for solidification to form a capillary or slurry state, and then powder and granules that do not contain harmful pollutants are added and kneaded. Next, there is a method for treating industrial waste containing harmful pollutants, which comprises solidifying after forming a funicular state suitable for solidification.