JP2734633B2 - Solidification method of incineration ash - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for solidifying incinerated ash, and in particular, obtains a solidified body having high crushing strength by subjecting incinerated ash to a hydrothermal reaction and solidifying it under heat and pressure. And a method for solidifying incinerated ash.

[Prior Art] Various metals are contained in incineration ash, and when landfill disposal or ocean dumping is performed as it is, elution of metals from the incineration ash becomes a problem. In particular, regarding the incineration ash of radioactive waste, a solidification process of the incineration ash is necessary from the viewpoint of elution of radioactivity and safety during storage.

Conventional methods for solidifying incinerated ash include cement solidification,
Although there is an asphalt solidification method, the content of incinerated ash with respect to the solidifying agent is small, so that the amount of waste increases.
Asphalt is flammable,
Fire prevention measures for the solidified material are required, and the strength of the solidified material itself is small.

As a method for solidifying radioactive waste, there are a plastic method and a melt solidification method. However, a solidifying agent or a solidifying container is expensive, running costs are high, and equipment is large.

As mentioned above, cement solidification method, asphalt solidification method,
Conventional solidification methods such as the plastic solidification method and the melt solidification method have the problems that the volume of the solidified material is significantly increased, the solidified material is flammable and has low strength, is expensive, and requires large-scale equipment. there were.

In order to solve this problem, the present applicant, a method of using the SiO ₂ contained in the incineration ash, which was added to NaOH was hydrothermal reaction solidifying the incineration ash, ie, SiO ₂ and Al ₂ O ₃ incinerated ash, NaOH, or NaOH and SiO
₂ containing material content in the mixture after the addition, SiO ₂ 25 to 90 wt%, Na ₂ O 2 to 10 wt%, with and mol% in Al ₂ O ₃ 5 wt% or more, SiO ₂ content , And water is added in an amount of 5 parts by weight or more based on 100 parts by weight of the mixture and kneaded.
A solidification method of incinerated ash characterized by solidifying while maintaining a heating and pressurizing state of 70 kg / cm ² or more and a temperature of 150 ° C. or more was found, and a patent application was previously filed (Japanese Patent Application Laid-Open No. 61-78483).

According to the method of the above-mentioned JP-A-61-78483, incineration ash
After adding NaOH and optionally SiO ₂ , adding water and kneading, the mixture is hydrothermally reacted to obtain a solid having a three-dimensional network of at least partially hydrated alkali-containing aluminosilicate. The metal is retained in the solidified body, the strength of the solidified body is high, and the elution of metal ions is extremely small. Also, an excellent effect that the volume of the incinerated ash is significantly reduced is achieved.

[Problems to be Solved by the Invention] However, depending on the composition and type of incinerated ash, the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-78483 requires the addition of more additives than necessary, which increases the processing cost and is economical. May be disadvantageous.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for solidifying incinerated ash that can obtain a solidified body having high crushing strength at low cost.

[Means for Solving the Problems] The method for solidifying incinerated ash according to the present invention comprises the following steps: 100 parts by weight of dry incinerated ash containing SiO ₂ and Al ₂ O ₃ ; 5 to 15 parts by weight of water;
That is, 3 to 15 parts by weight of Ca (OH) ₂ powder 3 to 15 parts by weight of CaCl ₂ powder is added and mixed with one or two kinds of substances, and the obtained mixture is subjected to a pressure of 100 kg / cm. ² or more, temperature 100 ~
It is characterized in that it is kept at a heating and pressurized state of 400 ° C. and solidified.

 Hereinafter, the present invention will be described in detail.

Dry incineration ash to be solidified in the present invention is Si
Includes O ₂ and Al ₂ O ₃ and includes municipal solid waste incineration ash, sewage sludge incineration ash, industrial waste incineration ash, coal incineration ash, etc. Fly ash (powder) collected by a collecting means such as a cyclone, a bag filter, and an electric dust collector is preferably used.

When a wet exhaust gas treatment device is employed, wastewater containing fly ash is generated. When the sludge generated in the process of treating the wastewater is treated according to the method of the present invention, it is preferable that the sludge be dehydrated and dried to a water content of 30% by weight or less before being applied.

Further, it is preferable that the bottom ash discharged from the bottom of the furnace is mixed with fly ash having the same weight or more and applied to the present invention.

In the present invention, 5 to 15 parts by weight of water and the following and / or are added and mixed with 100 parts by weight of such dry incineration ash.

3 to 15 parts by weight of Ca (OH) ₂ powder 3 to 15 parts by weight of CaCl ₂ powder In addition, water is mixed with Ca (OH) ₂ powder and / or CaCl ₂ powder and added and mixed in the form of an aqueous solution or a water slurry. May be. Water is advantageously added in the form of an aqueous solution or a water slurry of the powder from the viewpoints of the operability of the addition and mixing treatment, the uniformity of mixing and the reactivity.

Of the above additives, water is 5 parts per 100 parts by weight of incinerated ash.
If the amount is less than 15 parts by weight, the compression strength of the obtained solid is low, and if it exceeds 15 parts by weight, it is uneconomical.

If the Ca (OH) ₂ powder is less than 3 parts by weight with respect to 100 parts by weight of the incinerated ash, the obtained solid has a low compressive strength, and if it exceeds 15 parts by weight, it is uneconomical.

If the CaCl ₂ powder is less than 3 parts by weight with respect to 100 parts by weight of the incinerated ash, the obtained solid has a low compressive strength, and if it exceeds 15 parts by weight, it is uneconomical.

In the present invention, the incineration ash to be treated contains SiO ₂
Is preferably present in an amount of 25% by weight or more and Al ₂ O _{3 in an amount} of 3% by weight or more. Therefore, for example, when SiO ₂ is insufficient,
If necessary, a substance containing SiO ₂ is added. As the SiO ₂ -containing substance, silica stone powder or terra alba powder is suitable, but incinerated ash containing a large amount of SiO ₂ may be used.

The mixture obtained by adding and mixing a predetermined amount of additives is then subjected to a hydrothermal reaction while maintaining a pressure of at least 100 kg / cm ² and a temperature of 100 to 400 ° C. to solidify the mixture. Let That is, the present invention forms a three-dimensional skeleton structure (network) of an alkali-containing aluminosilicate which is at least partially hydrated by the hydrothermal synthesis reaction, thereby solidifying the incinerated ash and including it in the incinerated ash. Various metals (especially heavy metals) are contained in this network.

Next, the range of the content of SiO ₂ and Al ₂ O ₃ will be described.

SiO ₂ is an oxide that forms the above-mentioned alkali-containing aluminosilicate network. If its content is less than 25% by weight, the network is not sufficiently formed, and the strength of the solidified body is insufficient and brittle. Become. The upper limit of SiO ₂ is not particularly defined, Na ₂ O, the lower limit of Al ₂ O ₃ is 0.4 wt%, since it is 3 wt%, in the present invention, the SiO ₂ content 95 % By weight or less. Incidentally, a particularly preferred range is 30 to 60% by weight.

Al ₂ O ₃ cannot form a network by itself, but forms a network by replacing a part of SiO _{2 in} the network. Then, Al replaced with Si in the network has a negative charge and holds a metal ion having a positive charge. If the content of Al ₂ O ₃ is less than 3% by weight, the sequestering (containment) function of the network is reduced. If the Al ₂ O ₃ content is higher than SiO ₂ by mol%, the network will not grow sufficiently.

In the present invention, the pressure of the hydrothermal reaction is 100 kg / cm ² or more. The upper limit of the pressure is practically about 500 kg / cm ² . The pressure is naturally higher than the vapor pressure of water at the reaction temperature so as to be in a hydrothermal state.

If the temperature of the hydrothermal reaction is lower than 100 ° C., the solidification reaction does not proceed, and only a solid with extremely low strength is obtained,
If the temperature exceeds 400 ° C., there is a problem in the material of the apparatus. A particularly preferred temperature is 200 to 350 ° C or higher.

A hydrothermal reaction time of about 5 minutes to 1 hour is sufficient.
When the pressure and temperature of the hydrothermal reaction are low, the reaction time becomes longer. Conversely, when the pressure and temperature are increased, the reaction time becomes shorter.

In the method of the present invention, in order to cause a hydrothermal reaction,
It is convenient to use a device in which a compression piston is fitted to one or both ends of the cylindrical body and a reaction filling chamber is formed in the center of the cylindrical body. That is, a mixture obtained by adding water and kneading is filled into the reaction filling chamber, and the mixture is heated while compressing the filling with a compression piston to cause a hydrothermal reaction.

That is, first, the incinerated ash is weighed, and / or an additive, and if necessary, an SiO ₂ -containing substance is added and mixed.
The reactor is filled and heated under pressure to cause a hydrothermal reaction.

Prior to the weighing, if a pretreatment such as removing coarse particles of bolts, wires or sintered incineration ash contained in the incineration ash is performed, the post-process is facilitated.

After a lapse of a predetermined time, the temperature of the reactor is lowered and the solidified body is taken out.

In the method of the present invention, when the mixture is charged into the reactor, the kneaded material is divided into two or more parts, and a press (hereinafter, sometimes referred to as a temporary press) is performed each time one kneaded material is charged into the reactor. It is preferable to do so. By temporarily pressing in this way, the filling of incineration ash becomes uniform,
A good solid can be obtained. In addition, since the kneaded material of one section filled in the reactor is immediately compressed and its volume is reduced, it becomes possible to fill a large amount of kneaded material in the reactor, and in the fixed reactor, A large solid can be obtained efficiently. This temporary press pressure may be smaller than the pressure during the solidification reaction, for example, about 1/10 of the pressure during the solidification reaction. It should be noted that the press after filling all of the sorted mixture into the reactor is sufficient if the reaction is started by pressing at the pressure during the solidification reaction without performing such a light temporary press.

Thus, in the method of the present invention, the incineration ash to be treated only needs to be in a heated and pressurized state during the solidification reaction, and the pressure increases to a predetermined reaction pressure and to a predetermined reaction temperature. The temperature may be preceded by any of these, or may be performed simultaneously.

By the way, at the time of such heating and pressurizing, conventionally, the cylinder is filled with ash, the filling in the cylinder is compressed by a piston, and the cylinder is heated with an electric heater, a high-temperature gas, a high-temperature liquid, a high frequency, or the like. Heating by heat conduction from the heated cylinder,
Heating is performed by a so-called external heating method (for example, JP-A-59-116100).

However, the external heating method has poor heating efficiency,
There is a drawback that heating requires a long time and mass processing is difficult. For example, when a large solidified body having a diameter of 20 to 30 cm is formed by an external heating method, the solidification by heating and pressurizing is 2
A long time of up to 6 hours is required, and the processing efficiency is extremely poor.

Therefore, in the present invention, the cylindrical body is constituted by an electric insulator such as fine ceramics, the compression piston is made of a conductive material, and this is used as an electrode. A high frequency voltage is applied to this electrode to mix the incinerated ash in the cylindrical body. It is preferable to perform heating and pressurization by a so-called internal heating method in which high-frequency induction heating is performed while compressing. According to the internal heating method, it is possible to perform processing with extremely high heating efficiency, and the heating and pressurizing time is reduced to an extremely short time of 10 to 30 minutes, so that a large amount of processing can be achieved.

[Action] After adding and mixing water and one or two of the above-mentioned additives to the incinerated ash, the mixture is subjected to a hydrothermal reaction, so that at least a part of the incineration ash can be at least partially produced at a low cost with a minimum necessary amount of additives. A solid having a three-dimensional network of hydrated alkali-containing aluminosilicate is obtained. The metal is retained in the solidified body, the strength of the solidified body is high, and the elution of metal ions is extremely small. Also, the volume of the incinerated ash is significantly reduced.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Example 1 17 to 20 g of incineration ashes A and B having the composition shown in Table 1 were weighed, and the incineration ash was mixed with the additives shown in Table 2 and charged into a reaction tube having an inner diameter of 20 mmφ. The mixture was held at the pressure and temperature shown in Table 2 for 20 minutes to cause a hydrothermal reaction, thereby obtaining a solid.

The crushing strength of the obtained solid was measured, and the results are shown in Table 2.

As is apparent from Table 2, according to the method of the present invention,
A solid having a high pressure crush strength of approximately 110 kg / cm ² or more can be obtained at low cost and under appropriate heating and pressing conditions without using a large amount of additives.

[Effects of the Invention] As described in detail above, according to the method for solidifying incinerated ash of the present invention, a solidified product having high strength can be obtained at low cost, and its industrial utility is extremely high.

Claims (1)

(57) [Claims] 1. To 100 parts by weight of dry incineration ash containing SiO ₂ and Al ₂ O ₃ , 5 to 15 parts by weight of water and one or two substances selected from the group consisting of A method for solidifying incinerated ash, wherein the obtained mixture is solidified while keeping the mixture under pressure of 100 kg / cm ² or more at a temperature of 100 to 400 ° C. under heat and pressure. Ca (OH) ₂ powder 3 to 15 parts by weight CaCl ₂ powder 3 to 15 parts by weight