JPH10310464A - Compacting of fly ash which is industrial waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable solidification at a low temperature and pressure, to remarkably lower cost of the material added to fly ash, and to attain the effective utilizing of fly ash which is industrial waste generated in large quantities by mixing blast furnace slag with fly ash containing alkali by the specified quantity, adding water to the mixture to knead it, and compacting the kneaded material to solidify it. SOLUTION: Water is added to fly ash which is industrial waste in the presence of alkali, and the mixture is kneaded to form material. When the material is compacted to solidify it, 5-80 wt.% of blast furnace slag is added to the material to compact the mixture and solidify it. As the alkali, metal hydroxide or carbonate such as sodium hydroxide and calcium hydroxide is used. The added quantity of alkali is >=0.5 g equivalent to total weight of 1,000 g of the fly ash and the blast furnace slag. The fly ash to which the blast furnace slag is added realizes excellent strength equivalent to that of fly ash to which Portland cement is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming and solidifying fly ash, which is industrial waste generated in large quantities in power plants and the like that use coal as fuel.

[0002]

2. Description of the Related Art A thermal power plant using coal as fuel generates an enormous amount of coal ash, that is, fly ash.
Fly ash is an inorganic powder with very fine particles.
The main component is silica and alumina. Fly ash
Currently, most are disposed of by landfill or other means. However, fly ash is not a desirable physical property as a landfill material. For it does not set like the earth. Fly ash can be effectively used for various applications by solidifying it. In order to solidify the fly ash, there are a method using cement, and a method in which water is kneaded and molded in the presence of an alkali, and the mixture is heated and pressed to be solidified. A method of forming, heating and pressurizing by adding an alkali is described in JP-A-63-35469. Further, JP-A-4-237745 discloses that
Add slaked lime as an alkaline component to fly ash,
It is described that this is solidified and used as a humidity control material for construction.

[0003]

The fly ash molded by kneading in the presence of an alkali or by kneading cement can be solidified in a short time by heating and pressing. For example, fly ash can be solidified and formed as follows. 20 mol% of a 6 mol / l sodium hydroxide aqueous solution is added to the fly ash and kneaded. The kneading material is filled in a pressure vessel and molded. Thereafter, the filler is kept in a pressure vessel at a pressure of 20 MPa, and is heated to about 300 ° C. for 10 minutes to be solidified.

When the pressure at which the fly ash compact is broken is measured by pressing the fly ash compact, the compressive strength is about 22 MPa.

[0005] Furthermore, the method of adding cement to fly ash and solidifying it can produce a tougher fly ash formed body. For example, for fly ash, 10
A fly ash compact solidified in the same manner as described above, except that 10% by weight or 20% by weight of Portland cement is added, the compressive strength is 55 MPa and the Portland cement is 10% by weight of Portland cement. Compressive strength is 8 with the addition amount of
It becomes 0 MPa and becomes considerably tough.

[0006] As described above, fly ash is solidified in a short time by adding Portland cement or alkali.
Although it has preferable physical properties that can be molded, this method has a disadvantage that the molded material must be solidified under severe conditions of high temperature and high pressure, and equipment cost and running cost are increased. In order to effectively use a huge amount of industrial waste such as fly ash, it is very important to solidify and mold the waste easily and inexpensively and efficiently. This is because the processing of industrial waste is almost completely unprofitable and is therefore extremely economically burdensome, which is the biggest obstacle to its practical application.

[0007] Further, a molded product obtained by adding Portland cement to fly ash and solidifying it has excellent strength, but has a disadvantage that it has a large specific gravity and is heavy.

[0008] The present inventor reduced the weight of the molded article,
In order to lower the solidification temperature, we have developed a technology to add silica fume to fly ash, press and heat mold it, and solidify it. By this molding method, the solidification temperature was considerably reduced, and the molded body was successfully lightened. In the silica fume added to the fly ash, the amorphous silica contained therein is easily dissolved in an alkali, and is dissolved at a low temperature to solidify the fly ash.
Further, fly ash to which silica fume is added realizes excellent strength not inferior to the addition of Portland cement, and has a small specific gravity and can be reduced in weight.

Therefore, the method of adding silica fume to fly ash and solidifying it has excellent characteristics as compared with the conventional method, but has the disadvantage that the raw material cost is high because silica fume is considerably expensive. Further, fly ash to which silica fume is added can be solidified by pressurizing at a considerably low temperature of, for example, 100 ° C.
There is a disadvantage that it cannot be solidified without heating.

The present invention has been further developed to solve this drawback. It is an important object of the present invention that it can be solidified at a low temperature and a low pressure and significantly reduces the cost of raw materials added to fly ash. An object of the present invention is to provide a fly ash forming method capable of effectively reusing fly ash, which is a huge amount of industrial waste generated by reducing the amount of fly ash.

[0011]

According to the method of forming fly ash, which is industrial waste, of the present invention, fly ash is solidified and formed as described below to achieve the above-mentioned object. The fly ash is kneaded by adding water in the presence of an alkali, and the kneaded raw material is subjected to pressure molding and solidified. Further, in the method for forming fly ash of the present invention, instead of silica fume, blast furnace slag is added to fly ash and solidified by pressure molding. Blast furnace slag, like fly ash, is an industrial waste.
The amount of blast furnace slag added is in the range of 5 to 80% by weight.
When the addition amount of the blast furnace slag is 3% by weight or less, the effect of adding the blast furnace slag is reduced, and the strength is reduced. Conversely, when the amount of blast furnace slag added increases, the production cost increases. For this reason, the addition amount of the blast furnace slag is set in the above range in consideration of the heating temperature and the raw material cost.

The blast furnace slag added to the fly ash is easily dissolved in alkali like silica fume, and melts at a low temperature to solidify the fly ash.
Furthermore, fly ash with added blast furnace slag achieves excellent strength that is no less than that of adding Portland cement.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples are intended to exemplify a method for forming fly ash, which is industrial waste, for embodying the technical idea of the present invention. Not specific to

The fly ash is formed by solidifying and molding fly ash as follows. The forming method of the present invention is characterized by adding blast furnace slag to fly ash. The addition amount of the blast furnace slag is adjusted in the range of 5 to 80% by weight. In this specification, the addition amount of blast furnace slag is a weight ratio with the total weight of fly ash and blast furnace slag being 100. Therefore, the addition of 3 parts by weight of blast furnace slag to 97 parts by weight of fly ash is the minimum value, and the addition of 80 parts by weight of blast furnace slag to 20 parts by weight of fly ash is the maximum value.

An alkali is added to fly ash in addition to blast furnace slag. As the alkali, hydroxides and carbonates of metals such as sodium hydroxide and calcium hydroxide can be used. The amount of alkali added is 0.5 g equivalent or more based on the total weight of fly ash and blast furnace slag of 1000 g. If the amount of alkali added is less than this, sufficient strength cannot be obtained in a solidified state. When the addition amount of the alkali is increased, the strength of the solidified molded body increases. The addition amount of the alkali to 1 to 1.5 gram equivalent,
The strength of the molded body can be considerably improved. When the addition amount of alkali is further increased, the strength is increased, but the raw material cost is increased by adding a large amount of alkali. If the raw material cost is neglected, the amount of alkali added can be as high as 50 gram equivalent to the total amount of fly ash and blast furnace slag of 1000 g to obtain a molded article having sufficient strength. When a large amount of alkali is added, inexpensive slaked lime or the like is used for the alkali. Since a large amount of alkali cannot be added by dissolving in water, it is mixed with fly ash and blast furnace slag in the form of powder and added. In order to effectively utilize fly ash, which is industrial waste, it is extremely important to reduce the cost of the raw materials to be added. For this reason, the addition amount of the alkali is adjusted to an optimum value in consideration of both the strength required for the application and the raw material cost.

The alkali is added to fly ash and blast furnace slag in a state of being dissolved in water, or fly ash, blast furnace slag and alkali are dry-mixed, and then water is added and kneaded. The method of dissolving in water and adding an alkali has a feature that the alkali can be uniformly dispersed.

FIG. 1 shows a molding container for press-molding a molding material obtained by kneading fly ash, blast furnace slag, alkali and water. The molding container shown in this figure has a main body 1 which is cylindrical and has a molding chamber 7 at the center, a molding rod 10 which slides in close contact with the inner surface of the molding chamber 7 of the main body 1, and this molding rod 10 is connected to the tip. A pressing rod 2, a cylinder 3 for pressing the pressing rod 2, an arm 4 for connecting the cylinder 3 to the main body 1 so as to be detachable, a heater 5 for heating the main body 1 to a set temperature, and a heater 5. A temperature sensor 6 for controlling the main body 1 to a set temperature.

In the molding container shown in this figure, a gland packing 8 is provided at the boundary between the tip of the pressing rod 2 and the molding rod 10 so that gas does not leak in a heated and pressurized state. The gland packing 8 prevents gas from leaking from a gap between the pressing rod 2 and the inner surface of the molding chamber 7, and keeps the heated molding chamber 7 hermetically sealed and pressurized. Gland packing 8
The gap 9 is provided in the shape of a ring in the molded rod 10 further at the tip portion. The gap 9 is a gap for absorbing gas expansion.

The molded container shown in FIG.
The molding material is pressed. The cylinder 3 is removed from the arm 4 and the pressing rod 2 is pulled out to open the molding chamber 7. The molding chamber 7 is filled with a molding material. The pressing rod 2 is inserted into the molding chamber 7 of the main body 1. The cylinder 3 is mounted in a detachable cylinder 4A provided on the arm 4. The rod 11 of the cylinder 3 is pushed out, the pressing rod 2 is pressed by the cylinder 3, and the pressing chamber 2 is pressed by the pressing rod 2.
Fill. The cylinder 3 is held in a state where the pressing rod 2 is pressed, and the heater 5 is energized to heat the main body 1 to a set temperature. The heating temperature is, for example, 140 to 260 ° C.
The temperature gradient at which the heater 5 heats the main body 1 is, for example, 1
The temperature is set at 5 to 30C / min, preferably 20C / min. In this state, the molding material in the molding chamber 7 is heated and solidified in a pressurized state. When the molding material solidifies, the main body 1 is gradually cooled. After cooling the main body 1 to room temperature, the rod 11 of the cylinder 3
And remove the cylinder 3 from the arm 4. Thereafter, the pressing rod 2 is pulled out of the main body 1 and the solidified molded body is taken out of the molding chamber 7.

[0020]

EXAMPLE The fly ash is solidified by the above method as follows. Example 1 Fly ash is formed as follows. To 900 parts by weight of fly ash, 100 parts by weight of blast furnace slag are added and mixed. A blast furnace slag having a specific surface area of 8000 cm ² / g was used. In this step, 10% by weight of blast furnace slag is added to fly ash. To 10 g of the mixture of fly ash and blast furnace slag obtained in the above step, 1.5 cc of an aqueous solution in which 4 mol / l of sodium hydroxide is dissolved in water is added. The molding material is charged into the molding chamber 7 of the molding container shown in FIG. Holding the pressing rod 2 in a pressing state of 10 MPa,
The main body 1 of the molding container is heated to 150 ° C. by the heater 5 at a temperature gradient of 22 ° C./min, and the main body temperature is maintained at 150 ° C. for 10 minutes, and the energization of the heater 5 is stopped. After the main body 1 is cooled to 50 ° C., the pressing state of the pressing rod 2 is released, and the molded body is taken out of the molding chamber 7.

The compression strength of the obtained molded product is about 20MP.
a, The apparent specific gravity was 1.59, which was light and tough.

Example 2 A fly ash compact was manufactured in the same manner as in Example 1 except that the temperature for heating the main body 1 of the molded container was 175 ° C. The compression strength of the obtained molded body is about 40 MPa, and the apparent specific gravity is 1.64.
Met.

Example 3 A fly ash molded body was manufactured in the same manner as in Example 1 except that the temperature of heating the main body 1 of the molded container was set to 200 ° C. The compression strength of the obtained molded body was about 60 MPa, and the apparent specific gravity was 1.57.

Example 4 A fly ash molded body was manufactured in the same manner as in Example 1 except that the temperature for heating the main body 1 of the molded container was 225 ° C. The obtained molded article has a compressive strength of 64.3 MPa and an apparent specific gravity of 1.65.
Met. This strength is about twice that of ordinary concrete. Further, the specific gravity of the concrete is 2.1 to 2.2.
Therefore, the molded article of this example exhibits excellent characteristics of being lightweight and tough as compared with concrete.

Example 5 A fly ash molded body was manufactured in the same manner as in Example 1 except that the temperature of heating the main body 1 of the molded container was set to 250 ° C. The compression strength of the obtained molded body was 62 MPa, and the apparent specific gravity was 1.64.

FIG. 2 is a graph showing the compressive strength of the fly ash compacts experimentally produced in Examples 1 to 5. As shown in this graph, the compressive strength of the fly ash compact increases as the heating temperature increases. However, when the heating temperature is 230 ° C., the compressive strength is maximized,
C lowers somewhat at ° C. Further, FIG. 3 shows the tensile strength of the fly ash molded products prototyped in Examples 1 to 5. As shown in this graph, the tensile strength of the fly ash molded body also increases as the heating temperature increases. However,
It reaches its maximum when the heating temperature is about 200 ° C.
C lowers somewhat at ° C. For this reason, the heating temperature is set to about 200 ° C. in order to maximize the compressive strength and the tensile strength.

Example 6 The temperature for heating the main body 1 of the molding container was set to 200 ° C., and the pressure of the pressing rod 2 was set to 7.5 MPa.
A molded body of fly ash was produced in the same manner as in Example 1 except that a was used. The obtained molded article had a compressive strength of about 42 MPa and an apparent specific gravity of 1.53.

Examples 7 to 11 Example 6 except that the mixing ratio of the blast furnace slag was 20 to 80% by weight as described below.
A fly ash compact was produced in the same manner as described above. The compressive strength of the obtained molded body was about 40 to 60 MPa as shown in FIG. The apparent specific gravity is 1.53 ~
It was in the range of 1.67. Example 7 ... 20% by weight Example 8 ... 40% by weight Example 9 ... 50% by weight Example 10 ... 60% by weight Example 11 ... 80% by weight FIG. As shown, it can be seen that there is a sufficient solidification effect even when the mixing ratio of the blast furnace slag is 10% by weight. For this reason,
Fly ash can be effectively reused by reducing the amount of blast furnace slag added.

[Examples 12 to 17] In the same manner as in Example 1 except that the temperature for heating the main body 1 of the molding container was set to 200 ° C and the pressure of the pressing rod 2 was changed to 0.75 to 5.0 MPa. , And a fly ash compact was manufactured.
As shown in FIG. 5, the compressive strength of the obtained molded body was about 20%.
４０40 MPa. The apparent specific gravity is 1.48 to 1.
It was in the range of 54. Pressing pressure of pressing rod Example 12 ... 0.75 MPa Example 13 ... 1.25 MPa Example 14 ... 1.75 MPa Example 15 ... 2.5 MPa Example 16 ... 3.75 MPa Example 17 ... 5.0MPa

FIG. 5 shows that the compressive strength tends to increase as the pressure of the pressing rod is increased. However, even if the pressure is 0.75 MPa, it has sufficient strength. To make fly ash solidified practically, it is desirable to reduce the pressure as much as possible. For this reason, the pressure is set to 0.75 to 1.
It is economical to solidify the fly ash in the range of 5 MPa.

Further, a molded body of fly ash was produced by using the molded container shown in FIG. 6 instead of the molded container shown in FIG. 1 without heating the main body of the molded container. The molding container shown in FIG. 1 includes a main body 1 having a molding chamber 7 at the center, a pressing rod 2 which slides in close contact with the inner surface of the molding chamber 7 of the main body 1, and a cylinder 3 which presses the pressing rod 2. And an arm 4 connected to the main body 1 so that the cylinder 3 can be attached and detached. The molded container shown in this figure can have a simple structure by simplifying the tip of the pressing rod 2. However, as shown in the figure, this molded container is provided with a heater 5 for heating the main body 1 and a temperature sensor 6 for controlling the heater 5 to control the main body 1 to a set temperature, and heat the pressurized state. Thus, the fly ash molded body can be solidified.

Embodiments 18 to 21 The structure of the molding container is changed from the structure shown in FIG. 1 to that of FIG. 6, and the molding container main body 1 is kept in a pressurized state for about 10 hours without heating, and is solidified.
Except that the pressure of the pressing rod 2 is 7.5 MPa and the mixing ratio of the blast furnace slag is 20 to 60% by weight as described below.
In the same manner as in Example 1, a fly ash compact was manufactured. The compression strength of the obtained molded body was about 40 to 65 MPa as shown in FIG. The apparent specific gravity is 1.
It was in the range of 61 to 1.80. Mixing amount of blast furnace slag (% by weight) Example 18 ... 20% by weight Example 19 ... 30% by weight Example 20 ... 50% by weight Example 21 ... 60% by weight

As shown in FIG. 7, it can be seen that the fly ash compact can be solidified to a sufficient strength by press-forming without heating at a mixing ratio of blast furnace slag of 20% by weight. For this reason, it is possible to obtain a fly ash molded body without heating by adding the blast furnace slag to an amount of 20% by weight.

In the above embodiment, sodium hydroxide is used as the alkali. However, slaked lime or the like can be used instead of sodium hydroxide as the alkali. Furthermore, the strength of the fly ash molded article can be further improved by increasing the amount of alkali added.

Further, in the method for forming fly ash of the present invention, when the formed fly ash is heated and solidified, it is ideal that the fly ash is heated while being pressed by a pressing rod and solidified. It is not always necessary to keep the pressing state with a pressing rod or the like. For example, a molding material formed by kneading fly ash, blast furnace slag, alkali and water is put into an airtightly sealed autoclave chamber, heated steam is blown into the autoclave chamber, and the autoclave is heated and pressurized to solidify. You can also. The method of solidifying in an autoclave chamber has the feature that a large amount of molding material can be solidified at one time.

Further, for comparison, FIG. 8 shows the strength of the fly ash compact without the addition of blast furnace slag. The fly ash compact of this figure was manufactured in the same manner as in Example 1 except for the following conditions. (1) No blast furnace slag is added in the process of Example 1. (2) In the process of Example 1, fly ash 10
2 g of an aqueous solution obtained by dissolving 6 mol / l sodium hydroxide in water is added to g. (3) The heating temperature of the molding container is increased from 150 ° C. to 300 ° C., and is increased by 150 ° C., and the heating time is 10 minutes to 30 minutes. (4) In the process of the first embodiment, the pressing force of the pressing rod 2 is doubled from 10 MPa to 20 MPa.

As is apparent from FIG. 8, the fly ash to which no blast furnace slag is added has a high compressive strength despite a high alkali concentration, a high pressing force of the pressing rod, and a remarkably high heating temperature. It is about 20 MPa, which cannot be increased beyond this value.

[0038]

According to the method for forming fly ash, which is industrial waste, of the present invention, by adding blast furnace slag,
There is a feature that a tough molded body can be mass-produced at low temperature and low pressure at low cost. The solidification temperature can be lowered by adding blast furnace slag to fly ash, because blast furnace slag contains amorphous silica and is more easily dissolved in alkali than fly ash. Further, the method of the present invention can also solidify the mixture of fly ash and blast furnace slag without heating. It is also possible to add a blast furnace slag and heat it to 100 ° C. to solidify it in a short time for a molded body that does not require strength. Furthermore, the molding material is heated to a lower heating temperature compared to only fly ash, for example, heated to 200 ° C., and cannot be realized at all by only fly ash.
There is a feature that the compression strength can be increased to 60 MPa or more.

Furthermore, the fly ash forming method of the present invention can be performed without using expensive silica fume or the like.
Fly ash can be solidified by effectively utilizing blast furnace slag, which is industrial waste. Therefore, there is a feature that the raw material cost can be significantly reduced and the fly ash can be solidified.

Furthermore, the fly ash compact produced by the method of the present invention is significantly lighter in weight than the compact compacted with Portland cement, and has a strength comparable to the compact compacted with Portland cement. Features that can be realized can also be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a molding container used in a method for molding fly ash of the present invention.

FIG. 2 is a graph showing the relationship between the heating temperature of a fly ash compact and the compressive strength.

FIG. 3 is a graph showing the relationship between the heating temperature and the tensile strength of a fly ash compact.

FIG. 4 is a graph showing the relationship between the blast furnace slag mixing ratio and the compressive strength of the fly ash compact.

FIG. 5 is a graph showing the relationship between the pressure of a pressing rod and the compressive strength of a fly ash molded product.

FIG. 6 is a sectional view showing another example of a molding container used in the method for molding fly ash of the present invention.

FIG. 7 is a graph showing the relationship between the blast furnace slag mixing ratio and the compressive strength of a fly ash compact formed without heating;

FIG. 8 is a graph showing the compressive strength of a fly ash compact without the addition of blast furnace slag.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main body 2 ... Pressing rod 3 ... Cylinder 4 ... Arm 4A ... Detachable cylinder 5 ... Heater 6 ... Temperature sensor 7 ... Molding chamber 8 ... Gland packing 9 ... Air gap 10 ... Molding rod 11 ... Rod

Continuing from the front page (71) Applicant 595170339 Kentaro Nishino 397-8 Muronouchi, Ryoke-cho, Anan-shi, Tokushima Prefecture (72) Inventor Mamoru Nishioka 43, Kami-Fukui-Jido, Daifuku, Nakagawa-cho, Naga-gun, Tokushima Prefecture (72) Inventor Awa Kazuo 11-1 Yanaginohana, Yanagijima-cho, Anan-shi, Tokushima Prefecture (72) Inventor Kentaro Nishino 397-8, Muranouchi, Ryoke-cho, Anan-shi, Tokushima

Claims (1)

[Claims] 1. A method for forming fly ash, which is industrial waste, by adding water in the presence of alkali and kneading the raw material under pressure to solidify the fly ash. A method for forming fly ash, which is industrial waste, characterized in that blast furnace slag is added by weight and solidified by pressure molding.