JPS595322B2 - Melting treatment method for electrostatically collected ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for melting and treating electrostatically collected ash discharged from a garbage incinerator or the like.

Electrostatic precipitated ash discharged from a garbage incinerator differs slightly depending on the type of garbage, but generally, as shown in Table 1, it contains slag components of 50 to 70%, chlorides and sulfates of 25 to 45%.
%, and the low toxic heavy metals and general heavy metals are 3-5%.
Contains chi.

Among these, some of the harmful heavy metals and general heavy metals exist in the form of chlorides that are soluble in water, and the hazardous heavy metals that are dumped as they are exceed the emission regulation value as shown in the elution test results shown in Table 2. There is a risk of elution.

Furthermore, the particles of electrostatic precipitated ash are fine and have a bulk density of 0.2.
It is as small as ~0.3, and there are problems such as scattering during dumping and ground subsidence after dumping.

Cement solidification methods, asphalt solidification methods, sinter solidification methods, etc. have been proposed to solve these problems, but cement solidification methods and asphalt solidification methods have problems with the strength of the solidified product and are Because it is extremely soluble in water, there is a problem with the long-term stability of toxic heavy metals, and because it is bulky, there are problems in discarding it.

In addition, the sintering solidification method is a complex process, and because it is heated to high temperatures in the heat treatment process, harmful heavy metals (CdO, P,
There are problems such as volatilization of bO, etc.).

The present invention has been made in view of the above circumstances, and its purpose is to solidify slag components and metal oxide components, and recover volatilized harmful heavy metal chlorides by fractional distillation to make them non-polluting and reduce their volume. The purpose of the present invention is to obtain a method for melting and processing electrostatically precipitated ash.

That is, in the present invention, a fractionating tower provided at the upper part of the melting furnace is filled with alkaline or neutral granular refractories to form a plurality of packed beds, and the temperature of each packed bed becomes lower from the lower layer to the upper layer. An electric appliance characterized by heating and maintaining it within a predetermined temperature range, melting the electrostatically precipitated ash in a melting furnace to volatilize salts, and condensing and adhering the salts to each packed bed for fractional distillation according to type. This is a method for melting and processing collected dust ash.

Further, in the present invention, three filled layers are formed, and the lower layer has a density of 960 to 12
00℃, middle layer 420~960℃, upper layer 150~42℃
This method involves heating and maintaining the temperature at 0°C.

Further, in the present invention, electrostatically collected ash is melted in a melting furnace to a temperature of 1300 to 155
This method involves heating to 0°C.

The present invention will be explained below.

FIG. 1 shows an example of a fractionating apparatus used in the method of the present invention. This apparatus is equipped with a fractionating column 2 made of alkaline or neutral refractory material above a melting furnace 1, and inside this fractionating column 2. is filled with alkaline or neutral granular refractories to form three filled layers 31 to 33.

The melting furnace 1 is provided with an electrostatic precipitator ash inlet 4 and a molten slag outlet 5, and a high frequency heating coil 6 is installed around the melting furnace 1.

Further, a filling material charging lower and an extraction port 81 to 83 are formed in the lower part of each of the filling layers 3□ to 33, respectively.

Note that the alkaline or neutral refractory is a material such as magnesia or alumina.

Furthermore, acidic refractories are unsuitable because they react with alkali salts at high temperatures.

In the present invention, each of the filled layers 31 to 33 is heated in advance to a predetermined temperature range by the heating element 9.

This temperature range corresponds to the volatilized alkali salt (NaC4KCL
etc.) and harmful metal chlorides (CaC12, PbC12), the lower packed layer 31 is
It is preferable to heat and maintain the middle filled layer 32 at 420-960°C and the upper filled layer 33 at 150-420°C at 1200°C.

The reason for this is that 960°C is the temperature at which alkali salts and harmful metal chlorides can be separated, and 420°C is the temperature at which ZnC4
This is because 150° C. is the temperature at which water can be separated, and 150° C. is the temperature at which water can be released while remaining evaporated.

Next, electrostatically collected ash 10 is placed in the melting furnace 1 and melted.

This melting temperature is preferably 1300 to 1550°C.

The reason for this is that the temperature at which the slag component melts is 1250° C. or higher, and the temperature at which metallic iron melts is 1540° C., which is suitable for separating metallic iron from slag and recovering it.

Salts are volatilized by melting the electrostatically precipitated ash 10.

Among these, chlorides and sulfates with high melting points and boiling points are in the lower layer 3. It condenses and adheres to the person-proof filling material, and is periodically flushed out from the extraction port 81 or taken out together with the filling material.

Chlorides and sulfates collected in the lower packed bed 31 include those shown in Table 3.

Among the chlorides that are not collected in the lower packed bed 31, those within a predetermined temperature range are condensed and adhered to the filling in the middle packed bed 32, and are periodically flushed out from the extraction port, or are extracted together with the filling. It will be done.

Chlorides collected in the middle packed bed 32 include those shown in Table 3.

Chlorides that are not collected in the middle packed bed 32 condense and adhere to the filling in the upper packed bed 33 and are periodically flushed out from the outlet or extracted together with the filling.

Note that the salt-adhered fillers in the lower, middle, and upper packed layers 3□ to 33 are returned to the charging port again after being mechanically peeled off or separated by water washing.

Note that 11 in the figure is a temperature measuring device.

This method not only melts the electrostatically precipitated ash and volatilizes harmful heavy metals to reduce their content, but also dissolves them into the glassy or crystalline structure of the solidified molten slag. can be prevented.

Moreover, the obtained solidified product has a high volume reduction rate and can solve the problem of dumping.

Furthermore, this solidified product has high strength and can be effectively used as roadbed material, aggregate, etc.

In addition, since the volatilized salts such as heavy metals are recovered by fractional distillation according to their respective compositions, their treatment is easy and they can be used effectively.

Further, heating to 1300 to 1550°C allows separation of the slag and iron components, so the iron components can be used effectively.

Next, an experimental example of the present invention will be explained.

EXPERIMENTAL EXAMPLE Figure 2 shows the configuration of the experimental apparatus, and Table 1 shows the composition of electrostatically collected ash to be melted.

In this experimental device, the heating element is divided into three parts, each of which has an outer diameter of 60 rM inside an annular electric furnace 21 whose temperature can be controlled arbitrarily.
An alumina tube 22 with a length of 1,000 mm was inserted, and the lower part of the alumina tube 22 was filled with alumina powder 23 to support an alumina crucible 25 (melting furnace) containing electrostatically precipitated ash 24.

A thermocouple 26 was inserted directly below the alumina crucible 25, a filler support 27 was placed directly above it, and several magnetic chips 28 were filled thereon as granular refractories to a height of 100 m.

Furthermore, the same amount of glass beads 29 and magnetic chips 30 were sequentially filled in the same manner.

In addition, a magnetic protection tube 31 with an outer diameter of 10 mm was inserted into the center, and four thermocouples 32 were installed inside to measure the boundary temperature of each filling.

This electrostatically collected ash was melted and held at 1400° C. for 2 hours.

The lower layer of the filling layer (where the magnetic chip 28 is provided) is 960
~1200℃ middle layer (place where glass beads 29 are installed) 42
The upper layer (where the magnetic chip 30 was provided) was heated and maintained at 0 to 960°C and 150 to 420°C.

Table 4 shows the proportions of heavy metals distributed in each layer and in the molten slag.

From Table 4, 90% or more of heavy metal salts (including harmful heavy metals) are collected in the middle layer, and 90% or more of other salts are collected in the lower layer.

It is thought that the heavy metals (including harmful heavy metals) and alkalis that were not volatilized were fixed as slag'lIc oxides.

We also conducted elution tests on solidified molten slag.
In addition, hardness, bulk density, and volume reduction rate were measured.

The respective 11ffl results are shown in Table 5.

According to the above table, the elution of heavy metals is sufficiently lower than that in Table 2, and the emission regulation value is fully satisfied.

It was also observed that the hardness was high and the volume reduction rate was large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the present invention, and FIG. 2 is an explanatory diagram showing an experimental apparatus of the present invention. 1... Melting furnace (graphite), 2... Fractionating column, 31-33... Packed bed, 6... High frequency heating coil, 4... ...Electrostatic precipitator ash inlet, 5.
...Melted slag extraction port, 7...Filling material charging port, 8□~83...Extraction port, 9...
heating body.

Claims (1)

[Claims] 1. A fractionating tower provided at the top of the melting furnace is filled with alkaline or neutral granular refractories to form a plurality of packed beds, and the temperature of each packed bed decreases from the bottom to the top. The method is characterized by heating and maintaining it within a predetermined temperature range, melting the electrostatically precipitated ash in a melting furnace to volatilize the salts, and condensing and adhering the salts to each packed bed according to their type for fractional distillation. A method for melting and processing electrostatically precipitated ash. 2 Form three filled layers, lower layer at 960-1200°C,
2. The method for melting electrostatically precipitated ash according to claim 1, wherein the middle layer is heated and maintained at 420 to 960°C and the upper layer is heated to 150 to 420°C. 3. The method for melting electrostatically collected ash according to claim 1, which comprises heating the electrolysed ash to 1,300 to 1,550°C in a melting furnace.