JP2909662B2 - Manufacturing method of heat storage - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat storage body by effectively utilizing coal ash discharged by coal combustion in a coal-fired power plant or the like.

2. Description of the Related Art In recent years, coal as an energy source has been reviewed. Coal is used in large quantities and intensively in coal-fired power plants and the like. However, a large amount of ash is contained in coal, and a large amount of the ash is discharged as coal ash (fly ash) by burning the coal. At present, how to effectively use this large amount of coal ash is a major issue. As one of the methods of using coal ash, for example, the document "On the development and practical application of coal ash hardening technology" (Yasuo Tanaka)
There is [Fuel and Combustion Vol. 52, No. 10], which makes a roadbed body using coal ash. The purpose is different from that of the present invention, and the manufacturing method is completely different.

SUMMARY OF THE INVENTION An object of the present invention is to effectively utilize coal ash discharged after coal combustion and to burn the coal ash to produce a heat storage body having a high heat storage density.

Constitution of the invention
5% by weight of binder agent and 1 to 20 for coal ash
It is characterized by adding water by weight of water, kneading, press-molding under a pressure of 100 to 2000 kg / cm ² , and heating and firing in a temperature range of 1125 to 1225 ° C.

 Hereinafter, the present invention will be described in more detail.

FIG. 1 is a process chart showing an example of the manufacturing method (manufacturing method 1) of the present invention.

Since raw coal ash itself has a low bulk density, it cannot be used as it is as a heat storage body having a high heat storage density.

Therefore, in the present invention, press molding is performed in a mold in order to improve the heat storage density, that is, to increase the bulk density. Coal ash itself has poor cohesion and is difficult to handle as a compact.
Therefore, it is necessary to mold using a binder agent in order to impart caking properties and not to lose the shape after pressing. Preferred binder agents compatible with coal ash include polyvinyl alcohol and acryl. Examples include a system binder, carboxymethylcellulose, pregelatinized starch, lignin, and bentonite. By using these binders, the molded body is hardened and easy to handle.

The binder agent is added in an amount of 0.1 to 15% by weight based on coal ash (0.1 to 15 parts by weight based on 100 parts by weight of coal ash), preferably 0.3 to 10% by weight, more preferably 1 to 5% by weight.
It is.

If the amount is less than 0.1% by weight, the effect of adding the binder is not sufficiently exhibited. On the other hand, if the content of the binder agent exceeds 15% by weight, the effect is already saturated and is meaningless.

Note that coal ash has poor cohesion and does not solidify even when pressure-formed in a dry state. Also, if the coal ash is moistened with water and then pressure molded, it hardens for the time being, but is very brittle and difficult to handle.

Water is added to kneaded coal ash in which the binder agent is mixed in order to develop the binding property of the binder agent. The optimum amount of water to be kneaded varies depending on the type of the binder agent used, but is 1 to 20% by weight, preferably 3% by weight, based on the coal ash.
-15% by weight, more preferably 2-10% by weight. If the amount is less than 1% by weight, the binder agent hardly exhibits the caking property. On the other hand, if it is more than 20% by weight, it is difficult to perform pressure forming in a subsequent step.

The kneaded coal ash is put into a mold frame to obtain a desired shape, and is subjected to pressure molding to obtain a green compact. The pressure was maintained the shape of the molded body, and a range that is possible increase the bulk density, specifically, a 100 to 2,000 kg / cm ^2, preferably 300~1200kg / cm ^2. If it is less than 100 kg / cm ² , the bulk density does not increase, and even if it is 2000 kg / cm ² or more,
There is no remarkable effect on improving the bulk density.

The obtained pressed body is then fired at a temperature of 1125 to 1225 ° C, preferably 1150 to 1200 ° C. By firing in this temperature range, a fired body having a large bulk density and a high heat storage density can be obtained.

The preferred firing temperature range is also affected by the particle size of the coal ash and the like, and shifts to a higher temperature as coarse particles are included, and shifts to a lower temperature as the particle size is smaller.

As shown in the curve of coal ash in Fig. 4,
By heating and firing at a temperature of 60 ° C. or higher, the bulk density of the fired product is significantly increased. On the other hand, when the temperature exceeds 1200 ° C., voids are formed in the molded body, and the bulk density is conversely reduced.

The heating rate in the heating and firing is from 10 ° C / hour to 200 ° C /
The time range is good, and the temperature holding time is preferably in the range of 30 minutes to 5 hours. When the treatment is performed in this range, the bulk density is significantly increased. This is an experimental value, and the internal function and reason for increasing the bulk density are not fully understood.

The obtained coal ash sintered body has a large bulk density and a high heat storage density, and can be used as a heat storage body.

FIG. 2 is a process chart showing another embodiment (manufacturing method 2) of the present invention, in which ferric oxide powder is added to and mixed with raw coal powder.

Ferric oxide is added as an additive for adjusting bulk density and thermophysical properties, and the higher the ratio, the better. However, in order to suppress the effective use of coal ash and reduce production costs, 50% by weight or less is practical. And preferably not more than 40% by weight.

When ferric oxide is added to coal ash, the binder is added in an amount of 0.3 to 10% by weight (preferably 1 to 5% by weight) based on the total amount of coal ash and ferric oxide, and water is added to the coal. 3 to 15% by weight (preferably 5 to 10% by weight) is added to the total amount of ash and ferric oxide.

After the addition and kneading, pressure molding and baking are performed in accordance with Production Method 1.

As shown in FIG. 4, according to the production method 1 (see FIG. 1), when the coal ash is fired at 1200 ° C., the bulk density is 2.13 g / cm ³ , whereas under the same firing conditions, ferric oxide is used. 17% by weight
2.32g / cm ³ when added, and 2.5% when added by 33% by weight
It is significantly increased to 0 g / cm ³ .

FIG. 3 shows a process chart of another embodiment (manufacturing method 3) of the present invention.

The raw coal powder is pulverized to a particle size of 20 μm or less to form finely pulverized coal ash, and the finely pulverized coal ash, a binder agent, and water are kneaded. The following are heat-formed in the same manner as in production method 1,
It is fired to obtain a heat storage body. Further, as in the production method 2, 50% by weight or less of ferric oxide powder may be added to the finely ground coal ash.

Generally, coal ash used as a raw material contains coarse particles exceeding 100 μm in particle diameter. When the coarse particles are mixed, the particle gap tends to increase, and the bulk density of the heat storage body after firing decreases. In order to avoid this, the coal ash may be finely reduced to about 20 μm or less. When the particle size is larger than 20 μm, the effect of increasing the bulk density is reduced. In order to perform the pulverization, the coal ash itself is pulverized using a pulverizer such as a ball mill, a roller mill, and a vibration mill, or coarse particles are removed using an air classifier or the like.

Raw coal ash supplied from a coal-fired power plant was pulverized for 30 minutes with a vibration mill and compared with uncrushed coal ash. Hereinafter, the pulverized material is referred to as “crushed coal ash” or the original coal ash is referred to as “raw coal ash”. For comparison before and after the pulverization of the coal ash, the results of the particle size distribution measurement are shown in FIGS. 6A and 6B, and the electron micrographs thereof are shown in FIGS. 7A and 7B.

 In addition, properties such as the particle size of coal ash are shown in Table 1 below.

According to the production method 1, therefore, when the bulk density of the green compact obtained by kneading and pressure molding was compared, the raw coal ash was 1.59 g / cm ³ , while the pulverized coal ash was 1.74 / cm ³ .

When baked by heating according to the production method 1, as shown in FIG. 5, in the case of pulverized coal ash, the bulk density of the fired body is significantly increased in a temperature range of 1125 ° C. or more and 1175 ° C. or less.

By making the coal ash finer, the particles are more closely adhered and heat transfer is improved. For this reason, the firing temperature is lower by 20 to 40 ° C. than in the case of raw coal ash.

FIGS. 8A and 8B show electron microscopic observation photographs of the fired body obtained by firing the ground coal ash at 1175 ° C. and the fired body obtained by firing the raw powdered coal ash at 1200 ° C. in Production Method 1.

According to the present invention, a binder agent and water are added to coal ash, kneaded, and heated and fired after press molding,
As the fired body, a heat storage body having a large bulk density and excellent heat storage properties can be obtained.

Example 1 100 parts by weight of coal ash was mixed with 2 parts by weight of polyvinyl alcohol (hereinafter referred to as PVA) and kneaded with 7 parts by weight of water.
This was put into a molding frame and subjected to pressure molding at 1000 kg / cm ² to obtain a green compact. Next, the green compact was fired at 1200 ° C. to obtain a fired body.

 The following properties were obtained by measuring the thermophysical properties of the fired body.

At a measurement temperature of 20 ° C: bulk density 2.18 kg / m ³ , non-heat 0.74 kJ /
kgK, heat capacity 1602kJ / m ³ K.

At a measurement temperature of 800 ° C: high density 2.14kg / m ³ , specific heat 1.15kJ
/ kgK, heat capacity 2461kJ / m ³ K.

When the heat cycle test at 20 to 800 ° C. was repeated 100 times, it was confirmed that cracks did not occur, and it was found that the heat storage body could be used sufficiently.

Table 2 shows the details of the thermophysical properties of the obtained heat storage body and the following description together with the following Example 2 and below.

Example 2 33 parts by weight of ferric oxide were mixed with 67 parts by weight of coal ash. Further, 2 parts by weight of PVA was mixed and kneaded with 7 parts by weight of water. This was treated in the same manner as in Example 1 to obtain a fired body.

 The following properties were obtained by measuring the thermophysical properties of the fired body.

At a measurement temperature of 20 ° C: bulk density 2.72kg / m ³ , specific heat 0.68kJ /
kgK, heat capacity 1853kJ / m ³ K.

At a measurement temperature of 800 ° C: bulk density 2.66 kg / m ³ , specific heat 1.05 kJ
/ kgK, heat capacity 2797kJ / m ³ K.

When the heat cycle test at 20 to 800 ° C. was repeated 100 times, it was confirmed that cracks did not occur, and it was found that it could be sufficiently used as a heat storage body.

 Table 2 shows details of the thermophysical properties of the obtained heat storage material.

Example 3 Coal ash was pulverized with a vibration mill for 30 minutes to obtain pulverized coal ash. After kneading and molding this ground coal ash according to Example 1,
The green compact was fired at 1175 ° C. to obtain a fired body.

 The following properties were obtained by measuring the thermophysical properties of the fired body.

At a measurement temperature of 20 ° C: bulk density 2.54kg / m ³ , specific heat 0.76kJ /
kgK, heat capacity 1929kJ / m ³ K.

At a measurement temperature of 800 ° C: bulk density 2.49kg / m ³ , specific heat 1.23kJ
/ kgK, heat capacity 3066kJ / m ³ K.

When the heat cycle test at 20 to 800 ° C. was repeated 100 times, it was confirmed that cracks did not occur, and it was found that it could be sufficiently used as a heat storage body.

 Table 2 shows details of the thermophysical properties of the obtained heat storage material.

Comparative Example 1 A green compact was prepared according to the procedure of Example 1,
Was fired. Table 2 shows the thermophysical properties of the fired body.

Examples 4 to 8 Each binder shown in Table 2 below was mixed with 100 parts by weight of coal ash and kneaded with water. Put this in the molding frame 10
Press molding at 00 kg / cm ² gave a green compact. Then
The green compact was fired to obtain a heat storage body.

The bulk density of this heat storage body was measured, and the results are shown in Table 3.

[Brief description of the drawings]

FIG. 1, FIG. 2, and FIG. 3 are process diagrams showing the manufacturing method of the present invention. FIG. 4 is a graph showing the relationship between the firing temperature of the raw coal ash, the addition of ferric oxide, and the bulk density. FIG. 5 is a graph showing the relationship between the firing temperature and the bulk density of the pulverized coal ash. FIG. 6A is a graph showing a particle size distribution curve of the raw coal ash. FIG. 6B is a graph showing a particle size distribution curve of the pulverized coal ash. FIG. 7A is an electron micrograph showing the particle structure of the raw coal ash. FIG. 7B is an electron micrograph showing the particle structure of the pulverized coal ash. FIG. 8A is an electron micrograph showing a fracture surface (structure) of a fired body of raw coal ash. FIG. 8B is an electron micrograph showing a fracture surface (structure) of a fired body of pulverized coal ash.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Michio Yantori 502 Kandachi-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (56) References JP-A-60-41589 (JP, A) JP-A-62- 212260 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 5/00 F28D 20/00 B09B 3/00 WPI / L (QUESTEL)

Claims (3)

(57) [Claims] 1. A binder agent in an amount of 0.1 to 15% by weight based on coal ash and water in an amount of 1 to 20% by weight based on coal ash are added and kneaded, followed by press molding at a pressure of 100 to 2000 kg / cm ² . Later, 1
A method for producing a heat storage element, comprising heating and firing in a temperature range of 125 to 1225 ° C. 2. Ferrite oxide is added in an amount of 50% by weight or less based on coal ash to obtain a raw material powder.
After adding 3 to 10% by weight of a binder agent and 3 to 15% by weight of water to the raw material powder, kneading and press-molding at a pressure of 100 to 2000 kg / cm ² , a temperature range of 1125 to 1225 ° C. A method for producing a heat storage element, wherein the heat storage element is fired and heated. 3. The method for producing a heat storage body according to claim 1, wherein the coal ash is pulverized and refined to 20 μm or less, kneaded, and calcined by heating in a temperature range of 1125 to 1175 ° C.