JP2000237712A - Treatment of coal ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly divert coal ash generated in a large quantity from a thermal electric power plant or the like by adding and mixing an alkali neutralizing agent to the coat ash to manufacture a civil engineering and construction material such as a land-filling material a roadbed material, a banking material, a back filling material, a vegetation base material. SOLUTION: In the case of treating a large quantity of the coal ash 2 generated from the thermal electric power plant, the coal ash 2 is transported by a belt conveyer 1 and charged into a line mixer 3 and at the same time, gaseous carbon dioxide supplied from a neutralizing agent tank 4 as the alkali neutralizing agent is charged into the line mixer 3. Alkali earth metals or alkali components eluted from the coal ash 2 are neutralized by the gaseous carbon dioxide. If the neutralization reaction is insufficient with only stirring and mixing, the coal ash 2 is once taken out and charged into an aging vessel 6 to perform the neutralization reaction. The coal ash 2 after taken out from the line mixer 3 or the aging vessel 6 is used as the civil engineering and construction material 7 mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a large amount of coal ash generated from a thermal power plant or the like.

[0002]

2. Description of the Related Art Coal ash generated in large quantities from thermal power plants is used not only as landfill material, but also as a possibility of being diverted to roadbed material, embankment material, backfill material, backfill material, etc. However, when such coal ash is used, for example, as a landfill material, highly alkaline seepage water is generated with the infiltration of rainwater,
If left as it is, the alkaline component may flow into the groundwater system together with rainwater.

[0003] Therefore, if the landfill site is, for example, an industrial waste disposal site, even after the landfill disposal is completed, the leachate from the coal ash is collected in the collection and drainage structure laid on the bottom of the disposal site, and the leachate is collected. The exuded water is pumped up and neutralized until the pH of the water clears a predetermined drainage standard, for example, 5.8 to 8.6, and the exuded component from the landfill material diffuses into the environment by being discharged after that. Care has been taken to ensure that they do not.

[0004]

However, such work is often performed over a long period of time, which delays the use of the landfill, which is a valuable land resource, or makes it substantially difficult to use the landfill. The problem had arisen.

[0005] In addition, the alkali component leaching from coal ash inhibits plant growth and is difficult to use as a greening base material or embankment material. Was. In addition, such a problem,
Although it can be solved by isolating coal ash in the impermeable structure, construction of the impermeable structure requires extra costs.
The economy is inevitable.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a method for treating coal ash which can be promptly diverted to landfill materials, embankment materials, and the like.

[0007]

In order to achieve the above object, a method for treating coal ash according to the present invention comprises adding an alkali neutralizing agent to coal ash, mixing the coal ash with a landfill material, It is used to produce civil engineering and building materials such as roadbed materials, embankment materials, backfill materials, backfill materials, and greening base materials.

[0008] The method for treating coal ash according to the present invention comprises:
The alkali neutralizer is carbon dioxide.

According to a third aspect of the present invention, there is provided a method for treating coal ash, wherein a neutralizing agent insertion hole is formed in a landfill board using coal ash as a landfill material, and the neutralizing agent insertion hole is formed in the neutralizing agent insertion hole. A solid alkali neutralizer is charged.

In the method for treating coal ash according to the present invention, an alkali neutralizing agent is added to and mixed with coal ash to bury landfill, roadbed material, embankment material, backfill material, backfill material, greening base material and the like. Produce civil construction materials.

[0011] In this case, the added alkali-neutralizing agent neutralizes the coal ash, so that it can be quickly diverted as a civil engineering building material.

The alkali neutralizing agent may be any as long as it can neutralize the alkali component of coal ash, and includes low-concentration hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, organic acids, and sodium bicarbonate. Although it can be used, if the alkali neutralizing agent is carbon dioxide, even if it is supplied in large quantities to coal ash, the pH of the coal ash does not significantly shift to the acidic side, so soil acidification As a result, there is no concern about conversion to greening base materials and the like, and there is almost no environmental concern even if surplus carbon dioxide is released into the atmosphere. In addition, since the acidity of carbon dioxide is relatively weak, the state in which iron, aluminum, or heavy metals are eluted from coal ash is also prevented.

The form of addition of the alkali neutralizing agent may be gas (for example, carbon dioxide), liquid (for example, a solution of carbon dioxide), or solid (for example, dry ice). In addition, as an addition method, a gas or a liquid is fed into coal ash via an air supply pipe or a water supply pipe, and these are stirred and mixed, or a liquid or solid, particularly, finely pulverized one is added to the coal ash and stirred and mixed. There is a method such as doing.

Here, when the coal ash has already constituted a landfill board as a landfill material, a neutralizer insertion hole is formed in the landfill board, and a solid alkali neutralizer is formed in the neutralizer insertion hole. Agent,
For example, dry ice can be introduced. In such a case, the same operation and effect as described above can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating coal ash according to the present invention will be described below with reference to the accompanying drawings. It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof is omitted.

FIG. 1 shows how coal ash is treated according to the method for treating coal ash according to the present embodiment. As can be seen from the figure, in the method for treating coal ash according to the present embodiment, coal ash 2 generated in a thermal power plant or the like is conveyed by a belt conveyor 1, charged into a line mixer 3, and neutralized. Gaseous carbon dioxide (carbon dioxide) as an alkali neutralizer supplied from the agent tank 4 is fed into the line mixer.

In this manner, the supplied carbon dioxide gas neutralizes alkaline components such as alkaline earth metals and alkali metal ions such as calcium ions, sodium ions and potassium ions eluted from the coal ash 2.
The calcium ions contained in the coal ash 2 are converted into calcium carbonate by the reaction with carbon dioxide and remain in the coal ash 2. However, since the calcium carbonate is hardly soluble, it is diverted to civil engineering building materials described later. No problem arises when trying to do so. Rather, by being formed in the gap in the coal ash 2, it becomes possible to reduce the permeability coefficient and increase the strength of the civil engineering building material.

Since the neutralization by carbon dioxide naturally requires moisture, if the water content of the coal ash 2 is small, steam may be added to the carbon dioxide gas if necessary.
Processing such as increasing the water content of the coal ash 2 is appropriately performed.

Here, if the neutralization reaction is insufficient only by stirring and mixing in the line mixer 3, the coal ash 2 is once taken out from the line mixer 3 as shown by the process along the broken line in FIG. This may be put in the curing tank 6 to perform a neutralization reaction.

The feed speed of the line mixer 3 and the standing time in the curing tank 6 may be adjusted as needed while monitoring the pH change of the coal ash 2 and the like.

Next, the coal ash 2 directly taken out of the line mixer 3 or taken out of the curing tank 6 is used as landfill material, roadbed material, embankment material, backfill material, backfill material, greening base material, etc. Used as civil engineering and building materials 7.

Next, the effects of the method for treating coal ash according to the present embodiment have been confirmed by experiments, and the outline thereof will be described below.

First, 2.5 liters of water and 30 liters of carbon dioxide gas (about 6% by mass) were added to 1 kg of coal ash, and the pH changed as shown in Table 1. The pH when no carbon dioxide was added was 12.6.

[0024]

[Table 1]

As can be seen from the table, the pH significantly decreased, and a clear neutralizing effect was observed. Further, pH 5.8 to 8.6, which is a drainage standard, was satisfied.

When 1 liter of water and 10 liters of carbon dioxide (about 2% by mass) were added to 1 kg of coal ash, the pH dropped to 7.5 after one day.

As described above, according to the method for treating coal ash according to the present embodiment, the carbon dioxide gas fed into coal ash 2 reacts with calcium ions and the like in the coal ash to convert coal ash 2. Since the coal ash is neutralized, there is no danger of the alkaline component seeping out of the coal ash 2. Therefore, coal ash 2
Can be quickly diverted as civil engineering building material 7.

Further, according to the method for treating coal ash according to the present embodiment, carbon dioxide is used as the alkali neutralizing agent, so that not only the chemical cost required for neutralization can be reduced, but also the cost can be reduced. Even if a large amount is supplied to the coal ash 2, the pH of the coal ash does not significantly shift to the acidic side. Specifically, since the pH does not fall to about 5.5 or less, the adverse effect due to the acidification Is prevented beforehand, and there is no concern about conversion to a greening base material or the like.

Further, even if surplus carbon dioxide is released into the atmosphere, there is almost no environmental concern, so there is no need to provide a collecting and exhausting means. Further, since the acidity of carbon dioxide is relatively weak, it is possible to prevent iron, aluminum or heavy metals from being eluted from the coal ash 2 beforehand.

Further, according to the method for treating coal ash according to the present embodiment, since carbon dioxide is used in a gaseous state, that is, as carbon dioxide, it is possible to suppress an increase in the water content of coal ash 2. Post-treatment such as dehydration, vaporization, and drying becomes unnecessary, and as a result, it is diverted to civil engineering and building materials 7 such as landfill materials, roadbed materials, embankment materials, backfill materials, backfill materials, and greening base materials. Can be performed more quickly.

In the present embodiment, gaseous carbon dioxide (carbon dioxide) was used as the alkali neutralizer, but the form is not limited to such a gas, and a carbon dioxide solution prepared by blowing carbon dioxide may be used. Alternatively, solid ice, that is, dry ice, particularly finely ground one, may be used.

In the present embodiment, carbon dioxide is used as an alkali neutralizer, but the present invention is not limited to such a substance as an alkali neutralizer, but can neutralize an alkali component of coal ash. Anything is fine.

Further, in the present embodiment, the coal ash 2 generated in the thermal power plant or the like is neutralized and then diverted to various civil engineering and building materials 7, but as shown in FIG. When the ash 2 has already constituted the landfill board 11 as a landfill material, a neutralizing agent insertion hole 12 is formed in the landfill board, and a dry alkali neutralizer, which is a solid alkali neutralizing agent, is formed in the neutralizing agent insertion hole. Inject ice 13 and insert neutralizer insertion hole 1 as needed.
The cover 14 may be attached to the cover 2.

In such a configuration, the dry ice 13
While the carbon dioxide gas sublimated from the above neutralizes the alkali component of the coal ash while passing through the coal ash 2 as a landfill material, the landfill ground 11 made of the coal ash 2 is quickly changed from a highly alkaline ground to a neutral ground. Changes to

Therefore, compared to the conventional method in which the neutralization in the landfill board 11 is left to rainwater infiltration, it is possible to start using the former site after the completion of the landfill work, and to generate a large amount of heat from the thermal power plant. It becomes possible to actively and effectively use the coal ash 2 to be used as a landfill material for a landfill. Also,
By using solid dry ice 13, it is possible to prevent an increase in the water content in the landfill board 11, and post-treatment such as drainage is not required. Note that the operation and effect relating to the use of carbon dioxide are the same as those in the above-described embodiment, and thus a detailed description thereof will be omitted.

[0036]

As described above, according to the method for treating coal ash according to the first aspect of the present invention, the alkali neutralizer sent into the coal ash reacts with calcium ions and the like in the coal ash. In this way, the coal ash is neutralized, so that there is no possibility that the alkaline component is leached out of the coal ash. As a result, the coal ash can be quickly diverted as a civil engineering building material.

According to the method for treating coal ash according to the second aspect of the present invention, not only can the chemical cost required for neutralization be reduced, but even if a large amount of coal ash is supplied, The pH of coal ash does not significantly shift to the acidic side. Therefore, the adverse effects of acidification are prevented beforehand,
There is no concern about conversion to greening base materials. Also,
There is almost no environmental concern even if surplus carbon dioxide is released into the atmosphere, so there is no need to provide collection and exhaust means.Also, since the acidity of carbon dioxide is relatively weak, iron, aluminum or heavy metals are eluted from coal ash. This also has the effect of preventing the situation from occurring.

According to the method for treating coal ash according to the third aspect of the present invention, it is possible to quickly change a landfill made of coal ash from a highly alkaline ground to a neutral ground. Compared to the conventional method that entrusts the neutralization to rainwater infiltration, the use of the former site after the completion of landfill work can be started earlier, and a large amount of coal ash generated from thermal power plants is actively used as landfill material for landfill sites. It can be used effectively effectively.

[0039]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which coal ash is treated according to a method for treating coal ash according to the present embodiment.

FIG. 2 is a cross-sectional view illustrating a method of treating coal ash according to a modification.

[Explanation of symbols]

2 Coal ash 4 Neutralizer tank containing alkali neutralizer 7 Civil engineering building materials 11 Landfill 13 Dry ice (alkali neutralizer)

Claims (3)

[Claims] 1. An earth-building material such as a landfill material, a roadbed material, an embankment material, a backfill material, a backfill material, a greening base material, etc., is produced by adding and mixing an alkali neutralizing agent to coal ash. Coal ash treatment method. 2. The method for treating coal ash according to claim 1, wherein the alkali neutralizer is carbon dioxide. 3. A method for treating coal ash, comprising forming a neutralizing agent insertion hole in a landfill using coal ash as a landfill material, and introducing a solid alkaline neutralizing agent into the neutralizing agent insertion hole. Method.