JP2000274646A - Melting method for coal ash and fly ash of refuse incineration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To melt coal ash at low cost and to supply slag useful in building or civil work at low price by adding refuse incineration fly ash, as CaO source for lowering the melting point, to coal ash and melting the mixture in a melting furnace. SOLUTION: In order to utilize coal ash being produced when coal is combusted, the coal ash is admixed with refuse incineration fly ash as CaO source for lowering the melting point or a mixture thereof with refuse incineration ash and melted in a melting furnace. The refuse incineration fly ash or a mixture thereof with refuse incineration ash is added to the coal ash such that the basicity of molten slag CaO/SiO2 will be preferably in the range of 0.4-1.5. According to the method, coal ash is slagged at low cost and utilized in building or civil work. Since refuse incineration fly ash is diluted with coal ash and melted, generation of salts, e.g. NaCl or KCl, or Pb, Zn, and the like, can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for effectively melting coal ash and refuse incineration fly ash.

[0002]

2. Description of the Related Art In thermal power generation and the like, in recent years, conversion from oil or gas fuel to coal fuel has been actively promoted from the viewpoint of reducing fuel cost. Therefore, the emission of coal ash remaining after burning the coal also increases with the consumption of this coal.

Conventionally, this coal ash has been treated by landfilling, but it has become difficult to secure a landfill site, and various methods have been developed for effectively utilizing this coal ash instead of landfill. For this reason, at present, nearly 60% of the coal ash generated by the electric power business of about 5 million tons (FY 1994) is effectively treated.
However, since most of the effective treatment methods are for the cement field, there is a problem that the effective use in the cement field will be saturated in the future.

As a method of effectively using coal ash other than for the cement field, there is a method in which slag is obtained by melting and then cooling and solidifying coal ash, and the slag is used for civil engineering and construction. However, when coal ash is melted alone, the coal ash has a high content of SiO ₂ .Al ₂ O ₃ and Ca
Since the O content is low, the melting point is high, and such a high melting point requires a high temperature for melting. In addition, since the fluidity of the molten slag deteriorates, there is a problem that it is difficult to accumulate the slag or discharge it from the melting furnace. To solve these problems, Ca
Although it is necessary to lower the melting point by adding an O source, the CaO source currently used is a powder such as quicklime or limestone, and has a problem that the cost is high.

On the other hand, in Japan, municipal solid waste is
100,000 tons are generated, 75% of which is incinerated by an incinerator, and about 6 million tons of incinerated ash are generated annually. The incineration ash generated includes incineration ash discharged from the incinerator (hereinafter referred to as garbage incineration ash) and incineration fly ash collected by the exhaust gas treatment device of the incinerator (hereinafter, garbage incineration fly ash). The incineration fly ash has a fine particle size and contains a large amount of salts such as NaCl and KCl and heavy metals such as Pb and Zn.

[0006] In order to treat such refuse incineration ash and refuse incineration fly ash, a number of refuse incineration ash melting plants for melting them with electric power, coke, heavy oil and the like have been developed and put into practical use. However, in these melting plants, it is relatively easy to melt the refuse incineration ash alone and turn it into slag.However, a mixture of the refuse incineration ash and the refuse incineration fly ash or the refuse incineration fly ash alone is melted. There are various problems when processing. That is, NaC is contained in the molten fly ash generated when melting such garbage incinerated fly ash.
1, salts such as KCl, and heavy metals such as Pb and Zn. Among them, salts such as NaCl and KCl adhere to the duct and solidify, so that a problem such as clogging of the duct occurs, and furthermore, there is a problem that a great effort is required to remove the same. In addition, Pb and Zn are contained in the molten fly ash.
Since the molten fly ash is specified as a specially managed municipal waste because it contains harmful heavy metals such as harmful heavy metals, it cannot be disposed of unless these heavy metals are detoxified. Therefore, there arises a problem that processing of the collected molten fly ash is costly.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a low-cost slag that can be used for construction and civil engineering by melting coal ash at low cost. It is an object of the present invention to provide a method for melting coal ash and refuse incineration fly ash, which can simultaneously perform refuse incineration fly ash that has various problems during the melting treatment.

[0008]

According to the present invention, in order to achieve the above object, according to the first aspect of the present invention, coal incineration fly ash or trash incineration ash is used as a CaO source for lowering the melting point. And a method for melting coal ash and refuse incineration fly ash, characterized by adding a mixture of the above and melting in a melting furnace.

As described above, by adding refuse incineration fly ash or a mixture of this and refuse incineration ash to coal ash, CaO for lowering the melting temperature can be added to coal ash at low cost. Coal ash can be turned into slag at a cost. In addition, since refuse incineration fly ash is diluted with coal ash and melted, salts and Pb, such as NaCl and KCl, which are problematic in melting refuse incineration fly ash.
The amount of dust containing harmful heavy metals such as Zn can be relatively reduced. Therefore, it is possible to reduce the amount of fusion material from the melting furnace to the exhaust gas duct,
Further, the molten fly ash which needs to be detoxified because of containing harmful heavy metals can be relatively reduced.

[0010] In the present invention, as described in claim 2, ash incineration fly ash or a mixture thereof with ash incineration is added to coal ash by the basicity CaO / Si of molten slag.
It is preferred that O ₂ is added to a range of 0.4 to 1.5. Thus, the basicity of molten slag CaO /
By making SiO ₂ in the range of 0.4 to 1.5,
Because the melting temperature of slag can be kept low,
Melting and discharging of the slag becomes easy, and a stable melting process can be secured.

Further, in the present invention, it is preferable that the melting furnace for melting the coal ash and the refuse incineration fly ash or a mixture thereof and the refuse incineration ash is a swirling flow type melting furnace. Coal ash and refuse incineration fly ash are both powders, and it is therefore preferable to use a swirling flow type melting furnace that makes use of the characteristics of the powders.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for melting coal ash and incineration fly ash of the present invention will be described in detail. The present invention is characterized in that refuse incineration fly ash is used as a CaO source necessary for lowering the melting point when melting coal ash.

That is, in melting coal ash normally, since the melting point of coal ash alone is too high, the melting point has been lowered by adding a CaO source to coal ash.
At this time, powder such as quicklime or limestone is usually used as a CaO source to be added. However, these CaO sources cost about 2,000 yen to 8,000 yen per ton, which causes an increase in the cost of treating coal ash.

On the other hand, in the refuse incineration equipment, since the exhaust gas generated from the incinerator contains hydrogen chloride, a treatment for removing the hydrogen chloride is performed. As one of the methods for removing hydrogen chloride from the exhaust gas, powder of a calcium-containing substance such as CaO or Ca (OH) ₂ is blown into an exhaust gas path upstream of the dry dust collector, so that the calcium compound reacts with hydrogen chloride. There is a method of trapping hydrogen chloride by this chemical reaction. Therefore, a large amount of calcium is contained in the incineration fly ash subjected to such a dechlorination treatment, and the basicity CaO / SiO ₂ is high.

[0015] Further, the dust from the incineration fly ash has a problem that salts such as NaCl and KCl are contained in the melt fly ash when the fly ash is melted, so that it adheres to a duct or the like. Since the collected molten fly ash needs to be subjected to a detoxification treatment because of the inclusion of the like, the treatment is difficult.

Therefore, in the melting treatment of coal ash, by using refuse incineration fly ash as a CaO source for lowering the melting point, coal ash can be converted without using powders such as quicklime and limestone which cause a cost increase. Since it can be processed, the cost of the melting process of coal ash can be reduced. Further, as described above, since the refuse incineration fly ash having various problems during the melting treatment can be diluted with coal ash and treated, the various problems that occur when the above-mentioned refuse incineration fly ash are melted are solved. It can be reduced.

The coal ash to be melt-processed in the present invention is not particularly limited as long as it is coal ash, and various coal ash such as coal ash generated by thermal power generation can be used.

In the present invention, the incineration fly ash added to the coal ash or a mixture of the ash and the refuse incineration ash is added to the coal ash to add the basicity CaO / Si of the molten slag.
Any material can be used as long as it can raise O _2, and there is no particular limitation. Table 1 shows a specific example of the composition of such refuse incineration fly ash.

[0019]

[Table 1] As shown in the above example, the basicity CaO / S
It can be seen that iO ₂ is as high as 1.00 to 5.17, and can be sufficiently used as a CaO source in the treatment of coal ash.

In the present invention, such refuse incineration fly ash may be added to coal ash alone, or a mixture of refuse incineration fly ash and refuse incineration ash may be added to coal ash for use. Good. In any case, any material can be used as long as it can increase the basicity CaO / SiO ₂ of the molten slag and lower the melting point thereof. Specifically, the basicity Ca of the incineration fly ash or a mixture thereof and the incineration ash
It is preferable to use one having O / SiO ₂ of 0.8 or more, and it is particularly preferable to use one having O / SiO ₂ of 1.5 or more.

In the present invention, the ratio of addition of the above-mentioned refuse incineration fly ash or a mixture of this and the refuse incineration ash to the coal ash is such that the basicity CaO / SiO ₂ after addition is 0.4 to 1.5.
Is preferably added so as to fall within the range, particularly preferably within the range of 0.4 to 1.0. The reason for this range is that the melting temperature of the coal ash after the addition can be particularly lowered. In the present invention, since the incineration fly ash can be further processed in a larger amount and the melting temperature can be further lowered, the basicity CaO / SiO ₂ after the addition is 0.8 to 1. 0
It is particularly preferable that the compound is added so as to fall within the range of

The specific addition amount of this refuse incineration fly ash or a mixture of the refuse incineration ash to coal ash is based on the basicity CaO / of the refuse incineration fly ash or the mixture of the refuse incineration ash.
It changes greatly depending on SiO ₂ . Therefore, it is difficult to limit the range of the amount of addition, but for example, the incineration fly ash or the mixture of the incineration fly ash and the incineration ash is in the range of 0.15 to 1.0 with respect to the coal ash 1 by weight ratio. Can be added.

As the melting furnace used in the present invention, any melting furnace can be used, for example, an electric melting furnace such as an AC arc melting furnace, an electric resistance melting furnace, a plasma melting furnace or an induction melting furnace. Melting furnace, rotating surface melting furnace, reflection type surface melting furnace, self-combustion type melting furnace, radiation type surface melting furnace,
Examples include a swirling flow type melting furnace, a rotary kiln type melting furnace, a coke bed type melting furnace, and a fuel combustion type melting furnace such as an oxygen burner flame type melting furnace. In the present invention, since coal ash and refuse incineration fly ash are powders, it is preferable to use a swirling flow type melting furnace to which such powders can be directly charged. In other systems, coal ash must be briquetted or granulated and charged, which is disadvantageous in terms of costs such as binder costs and granulation costs.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, in the above embodiment, there is no example in which refuse incineration ash is used alone as a CaO source. This is because the basicity CaO / SiO ₂ of normal garbage incineration ash is
This is because such incineration ash having a low basicity CaO / SiO ₂ is not used alone because it is not so high as 0.4 to 0.6. However, if the situation changes due to a change in the method of the desalination treatment, and the incineration ash having a high basicity of CaO / SiO ₂ becomes available, such incineration ash is mixed with the incineration fly ash. It is also possible to use without doing.

[0026]

EXAMPLES (Example) 343 kg of high-alkaline refuse incineration fly ash was added to 1000 kg of coal ash, and charged into a swirling flow type melting furnace to perform melting treatment to obtain 1124 kg of slag. At this time, the basicity CaO / SiO ₂ of the molten slag was 0.4. The consumed heavy oil was 150 L (224 kg of alternative coal powder). The melting process was very smooth and the slag could be discharged stably. By cooling the obtained slag by air, a slag having high strength and suitable as a roadbed material could be obtained.

Comparative Example 283 kg of limestone powder was added to 1000 kg of coal ash and charged into a swirling flow type melting furnace.
Melting was performed to obtain 1085 kg of slag. At this time, the basicity CaO / SiO ₂ of the molten slag was 0.4. The consumed heavy oil is 145L (alternative coal powder 216kg)
Met. The melting process was very smooth and the slag could be discharged stably. By cooling the obtained slag by air, a slag having high strength and suitable as a roadbed material could be obtained.

As is clear from the above Examples and Comparative Examples, even when high alkali dust incineration fly ash was used in place of limestone powder, dust was slightly increased in the exhaust gas, but the melting process and the resulting slag were not used. There was no problem at all, and it became clear that refuse incineration fly ash could be used as a CaO source. Table 2 summarizes the compositions of the used coal ash, limestone powder and fly ash from incineration of high alkali garbage. In addition, the unit of the numerical value in a table | surface is all weight%.

[0029]

[Table 2]

[0030]

As described above, the method for melting coal ash and refuse incineration fly ash according to the present invention provides a method for melting coal ash and refuse incineration fly ash as a CaO source for lowering the melting point. It is characterized in that a mixture with ash is added and melted in a melting furnace. As described above, by adding garbage incineration fly ash containing a CaO source to coal ash or a mixture of this and garbage incineration ash, a CaO source for lowering the melting temperature can be added to coal ash at low cost. And slag can be obtained at low cost. Also,
Since waste incineration fly ash is diluted with coal ash and melted, generation of dust containing salts such as NaCl and KCl and toxic heavy metals such as Pb and Zn which are problematic in the melting treatment of the waste incineration fly ash. The amount can be relatively reduced. Therefore, it is possible to reduce the amount of the fused material from the melting furnace to the exhaust gas duct, and it is possible to relatively reduce the molten fly ash that must be subjected to the detoxification treatment.

Claims (3)

[Claims] 1. A method for reducing the melting point of coal ash.
A method for melting coal ash and refuse incineration fly ash, comprising adding refuse incineration fly ash or a mixture of this and refuse incineration ash as an O source and melting in a melting furnace. 2. A method according to claim 1, wherein said fly ash or a mixture of said fly ash and said waste ash is mixed with said coal ash to a basicity C of molten slag.
melt processing method for coal ash and refuse incineration fly ash according to claim 1, wherein the aO-/ SiO ₂ is added to a range of 0.4 to 1.5. 3. The method according to claim 1, wherein the melting furnace is a swirling flow type melting furnace.