JP2898238B2 - Method of forming fly ash as industrial waste - Google Patents

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 cured in a short time by heating and pressurizing. For example, fly ash can be solidified and formed as follows. 20% by weight of a 6 M aqueous sodium hydroxide solution is added to the fly ash and kneaded. The kneading material is filled in a pressure vessel and molded. Thereafter, the filler is held in a pressure vessel at a pressure of 20 MPa, and is cured by heating to about 300 ° C. for 10 minutes.

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.

Further, a method of adding cement to fly ash and curing the fly ash can produce a tougher fly ash molded body. For example, for fly ash, 10
The fly ash molded body solidified in the same manner as the above method except that wt% or 20 wt% of Portland cement is added, the compressive strength is 55 MPa, and the addition of Portland cement is 10 wt% of Portland cement. Compressive strength of 8 with the amount of 20 wt%
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.

The present invention has been developed for the purpose of effectively utilizing a huge amount of fly ash generated. An important object of the present invention is to enable solidification at a low temperature and a low pressure and to obtain a molded article. An object of the present invention is to provide a method for forming fly ash, which is industrial waste that can be mass-produced.

[0008]

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 molded, heated, and cured. Further, the molding method of the fly ash of the present invention, the fly ash, with the addition of silica fume 3～50Wt%, was added silica fume original
The material is cured by heating under pressure . When the addition amount of silica fume is 3 wt% or less,
The effect of adding silica fume is reduced, and the heating temperature for curing is increased. Conversely, when the amount of added silica fume increases, the production cost increases. For this reason, the addition amount of silica fume is set in the above range in consideration of the heating temperature and the raw material cost.

In the silica fume added to 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 with added silica fume achieves excellent strength no less than the addition of Portland cement.

[0010]

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 molding method of the present invention is characterized by adding silica fume to fly ash. The amount of silica fume added is 3 to 50.
It is adjusted to the range of wt%. In this specification, the amount of silica fume added is a weight ratio where the total weight of fly ash and silica fume is 100. Therefore, the addition of 3 parts by weight of silica fume to 97 parts by weight of fly ash is the minimum value, and the addition of 50 parts by weight of silica fume to 50 parts by weight of fly ash is the maximum value.

An alkali is added to fly ash in addition to silica fume. 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 silica fume of 1000 g. If the amount of alkali added is less than this, sufficient strength cannot be obtained in a cured state. When the addition amount of the alkali is increased, the strength of the cured molded body increases. When the amount of the alkali added is 1 to 1.5 gram equivalent, the strength of the molded article can be considerably improved. Further increasing the amount of alkali added, the strength increases, but the material cost increases become the Turkey to add a large amount of alkali.
Neglecting the raw material cost, the amount of alkali added to the total amount of fly ash and silica fume 1000g,
By adding 50 gram equivalents, a molded article having sufficient strength can be obtained. 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 silica fume 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 amount of alkali added depends on the strength required for the application,
Adjust to the optimum value taking into account both raw material costs.

The alkali is added to fly ash and silica fume in a state of being dissolved in water, or fly ash, silica fume and alkali are dry-mixed,
Thereafter, 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, silica fume, alkali and water. The molding container shown in this figure is a cylinder-shaped main body 1 having a molding chamber 7 at the center, a molding rod 2 that slides in close contact with the inner surface of the molding chamber 7 of the main body 1, and a cylinder that presses the molding rod 2. 3 and cylinder 3
An arm 4 is connected to the main body 1 so that the main body 1 can be detached, a heater 5 for heating the main body 1 to a set temperature, and a temperature sensor 6 for controlling the heater 5 to control the main body 1 to the set temperature.

The molded container shown in FIG.
The molding material is pressed. The cylinder 3 is removed from the arm and the molding rod 2 is pulled out to open the molding chamber 7.
The molding chamber 7 is filled with a molding material. The forming rod 2 is inserted into the forming chamber 7 of the main body 1. The cylinder 3 is mounted in a detachable cylinder 4A provided on the arm. The rod of the cylinder 3 is extruded, the molding rod 2 is pressed by the cylinder 3, and the molding chamber 7 is filled with the molding rod 2.
The cylinder 3 is held in a state of pressing the forming rod 2, and the heater 5 is energized to heat the main body 1 to a set temperature.
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 the main body 1 is cooled to room temperature, the rod of the cylinder 3 is pulled in and the cylinder 3 is removed from the arm. Thereafter, the molding rod 2 is pulled out of the main body 1 and the solidified molded body is taken out of the molding chamber 7.

[0016]

EXAMPLE The fly ash is solidified by the above method as follows. [Example 1] Fly ash is formed as follows. 90
100 parts by weight of silica fume is added to 0 parts by weight of fly ash and mixed. In this step, 10 wt% of silica fume is added to fly ash. 150 cc of an aqueous alkali solution is added to 850 g of the mixture of fly ash and silica fume obtained in the above steps, and the mixture is kneaded to obtain a molded material. The aqueous alkali solution is 4
Gram equivalents (160 g) of sodium hydroxide were added to 100
It is made by dissolving in 0cc of water. This alkaline aqueous solution contains 0.6 gram equivalent of sodium hydroxide in 150 cc. Therefore, this molding material is 1000 g
Contains 0.6 gram equivalent of alkali. The molding material is charged into the molding chamber 7 of the molding container shown in FIG.
While the forming rod 2 is kept in a pressed state of 5 MPa, the main body 1 of the forming container is heated by the heater 5 at a temperature gradient of 22 ° C./min.
The heater 1 is heated to 20 ° C., the temperature of the main body 1 is kept at 120 ° C. for 10 minutes, and the energization of the heater 5 is stopped. After the main body 1 is cooled to 50 ° C., the pressed state of the forming rod 2 is released, and the formed body is taken out of the forming chamber 7.

The obtained molded product has a compressive strength of 22.2M.
Pa and the apparent specific gravity was 1.79.

Example 2 A molded body was manufactured in the same manner as in Example 1 except that the temperature at which the main body 1 of the molded container 1 was heated was 140 ° C. The obtained molded article had a compressive strength of 25.9 MPa and an apparent specific gravity of 1.80.

Example 3 A molded article was manufactured in the same manner as in Example 1 except that the temperature at which the main body 1 of the molded container 1 was heated was 110 ° C. The obtained molded article had a compressive strength of 4.5 MPa and an apparent specific gravity of 1.70.

Example 4 Example 1 was repeated except that the temperature for heating the main body 1 of the molding container was set at 200 ° C. and the pressing pressure of the molding rod 2 was set at 2 MPa.
A fly ash compact was produced in the same manner as in Example 1.
The obtained molded article had a compressive strength of 35.8 MPa and an apparent specific gravity of 1.69.

Example 5 The procedure of Example 1 was repeated, except that the amount of sodium hydroxide dissolved in 1000 cc of water was changed from 4 gram equivalents of Example 1 to 2 gram equivalents. Thus, a molded body of fly ash was manufactured. The obtained molded body had a compressive strength of 6.0 MPa and an apparent specific gravity of 1.
66.

Further, a molded product of fly ash was produced using the molded container shown in FIG. 2 instead of the molded container shown in FIG. The molding container shown in FIG. 2 is provided with a gland packing 8 at the distal end of the molding rod 2 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 forming rod 2 and the inner surface of the forming chamber 7, and keeps the heated forming chamber 7 airtight and pressurized. A ring-shaped gap 9 is provided at the tip of the gland packing 8. The gap 9 is a gap for absorbing gas expansion.

Example 6 A molded article was produced in the same manner as in Example 1 except that the structure of the molded container was changed from the structure shown in FIG. 1 to FIG. 2, and the temperature for heating the main body 1 was set to 200 ° C. The obtained molded product had a compressive strength of 42.8 MPa and an apparent specific gravity of 1.80.

Example 7 A molded article was produced in the same manner as in Example 1 except that the structure of the molded container was changed from the structure shown in FIG. 1 to FIG. 2, and the temperature for heating the main body 1 was 140 ° C. The obtained molded body had a compressive strength of 29.4 MPa and an apparent specific gravity of 1.80.

Example 8 A molded article was produced in the same manner as in Example 1 except that the structure of the molded container was changed from the structure shown in FIG. 1 to FIG. The obtained molded body had a compressive strength of 24.2 MPa and an apparent specific gravity of 1.79.

Example 9 A molded article was manufactured in the same manner as in Example 1 except that the molding container was changed from the structure shown in FIG. 1 to FIG. 2, and the temperature for heating the main body 1 was 110 ° C. The obtained molded article had a compressive strength of 14.3 MPa and an apparent specific gravity of 1.79.

Example 10 A molded article was manufactured in the same manner as in Example 1 except that the structure of the molded container was changed from the structure shown in FIG. 1 to FIG. The obtained molded article had a compressive strength of 9.5 MPa and an apparent specific gravity of 1.76.

FIG. 3 is a graph showing the compressive strength of the fly ash compacts experimentally produced in Examples 1 to 10. As shown in this graph, the compressive strength of the fly ash compact increases as the heating temperature increases. However, in this graph, in Example 4 and Example 5, the pressing force of the forming rod 2 in the heated state is 2 MPa.

Further, the amount of silica fume added to fly ash was changed, and how the compressive strength of the fly ash formed changed was measured. FIG. 4 shows the results. However, in this figure, a fly ash molded body was manufactured in the same manner as in Example 1 except for the following conditions. (1) In the process of the first embodiment, the amount of the alkaline aqueous solution is changed from 150 cc to 130 cc. (2) The heating temperature of the molding container is from 120 ° C. to 200 ° C., and the heating time is from 10 minutes to 30 minutes. The curve A in this figure indicates that the pressing force of the forming rod 2 is 16 MPa.
Shows the compressive strength was, curve B that shows the compressive strength was 11MPa pressing force of the forming rod 2.

As is clear from FIG. 4, the strength of the silica fume forming method of the present invention in which silica fume is added is remarkably increased by increasing the amount of silica fume added. The compact to which 20% by weight of silica fume was added had a remarkably increased compressive strength of about 140 MPa.

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, according to the method for forming fly ash of the present invention, the formed fly ash can be heated and cured while being pressed by the forming rod 2 to form a tough formed body. It is not necessary to keep the pressed state by 2 or the like. For example, a molding material formed by kneading fly ash, silica fume, alkali and water is put into an airtightly sealed autoclave chamber,
Heating steam is blown into the autoclave chamber and heated with steam.
It can be cured by applying pressure. The method of curing in an autoclave chamber has the feature that a large amount of molding material can be cured at a time.

In order to clarify how excellent the fly ash molded article of the present invention is, a fly ash molded article is produced by trial using Portland cement instead of silica fume, and the strength is measured as shown in FIG. Became. In this figure, a fly ash molded body was manufactured in the same manner as in Example 1 except for the following conditions. (1) The heating temperature of the molding container is from 120 ° C. to 300 ° C. in Example 1, and the heating time is from 10 minutes to 20 minutes. (2) The pressing force of the forming rod 2 is changed from 5 MPa of Example 1 to 20 MPa.

As is apparent from FIG. 5, the addition of Portland cement to fly ash is effective in increasing the strength of the compact. However, the compressive strength can be remarkably improved to 140 MPa by adding 20 wt% of silica fume, while Portland cement is 20 to
By adding 30 wt%, the compressive strength can be increased only up to 80 MPa.

Further, in the fly ash molded body to which silica fume is not added, the pressing force of the molding rod 2 is increased,
Even if the amount of alkali added is increased and the heating temperature is further increased to increase the heating time, the compressive strength does not increase,
It is clear from FIG. In this figure, a fly ash molded body was manufactured in the same manner as in Example 1 except for the following conditions. (1) In the step of Example 1, no silica fume is added. (2) In the process of Example 1, the amount of sodium hydroxide added to 1000 cc of water is 6 gram equivalent. (3) Add 150 cc to 200 cc of the aqueous alkali solution
increase to cc. (4) The heating temperature of the molding container is increased from 120 ° C. to 300 ° C., and is increased by 180 ° C., and the heating time is set to 10 minutes to 30 minutes. (5) In the process of Example 1, the pressing force of the forming rod 2 is quadrupled from 5 MPa to 20 MPa.

As is apparent from FIG. 6, the fly ash to which no silica fume is added has a high compressive strength despite the high alkali concentration, the high pressing force of the forming rod 2 and the remarkably high heating temperature. About 20MP
a, which cannot be increased beyond this value.

[0037]

The method for forming fly ash, which is industrial waste, according to the present invention has the feature that by adding silica fume, a tough molded body can be mass-produced at low temperature and low pressure at low cost. The reason why the curing temperature can be lowered by adding silica fume to fly ash is that silica fume contains amorphous silica and thus is more easily dissolved in alkali than fly ash. The method of the present invention comprises:
It is also possible to add a silica fume to a molded body that does not require strength and to cure it by heating to 100 ° C. Furthermore, when the molding material is heated to a lower heating temperature, for example, 200 ° C. as compared with only fly ash, the compression strength is 100 M, which cannot be realized by fly ash alone.
There is a feature that can be increased to Pa or more.

[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 cross-sectional view showing a molded container having another structure used in the method for molding fly ash of the present invention.

FIG. 3 is a graph showing the compressive strength of a molded article produced by the molding method of the present invention.

FIG. 4 is a graph showing the compressive strength of a molded product obtained by adding silica fume to fly ash.

FIG. 5 is a graph showing the compressive strength of a molded product obtained by adding Portland cement to fly ash.

FIG. 6 is a graph showing the compressive strength of a fly ash compact without addition of silica fume and Portland cement.

[Explanation of symbols]

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

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mamoru Nishioka 43, Kamifukui-jidou, Ogawa, Nakagawa-cho, Naga-gun, Tokushima Prefecture Inventor Kentaro Nishino 397-8 Muronouchi, Ryoke-cho, Anan-shi, Tokushima (56) Reference JP-A-6-239655 (JP, A) JP-A-64-90079 (JP, A) JP-A-63-35469 JP, A) JP-A-61-78483 (JP, A) JP-A-9-108649 (JP, A) JP-A-8-119693 (JP, A) JP-A-7-232973 (JP, A) JP-A-2-66256 (JP, A) JP-A-55-73383 (JP, A) JP-A-57-204276 (JP, A) JP-A-7-165455 (JP, A) JP-A-50-119000 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B09B 3/00 C04B 7/26

Claims (1)

(57) [Claims] 1. A raw material in which fly ash, which is industrial waste, is kneaded by adding water in the presence of an alkali to form a raw material,
In a method for forming a fly ash in which a molding material is heated and hardened, 3 to 50% by weight of silica fume is added to the fly ash, and a raw material to which the silica fume is added is added.
A method of forming fly ash, which is industrial waste, characterized in that the material is cured by heating under pressure .