JPS5953230B2 - Method for producing hardened material using coal ash as main raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a hardened material using coal ash as a main raw material discharged during coal combustion, specifically, a method for producing a hardened material using coal ash as a main raw material, and more specifically, coal ash, quicklime and/or slaked lime, dihydrate gypsum, hemihydrate gypsum,
or/and relates to a method for producing a hydrated hardened product with high mechanical strength by kneading a mixed powder containing type II anhydride with a small amount of phosphoric acid and moisture at room temperature and curing at room temperature. be.

In recent years, the development of alternative energy to oil has become a national issue in our country in order to reduce our dependence on oil.
Coal energy is being actively promoted as one of the pillars of energy.

As one of the challenges in the practical application of coal utilization technology necessary for mass consumption of coal, the treatment of large amounts of coal ash generated during coal combustion has been highlighted as an important issue. During coal combustion, coal ash is usually generated which is approximately 10-20% by weight of the amount of coal used.

Conventionally, in Japan, a part of fly ash is reused as cement admixture, cement raw material, etc., and the rest is disposed of in landfills. However, it cannot be expected that the demand for coal ash will be sufficient to meet the huge amount of coal ash that will be produced in the future through reuse using only the current method. With the tightening of environmental regulations, it is becoming difficult to secure ash disposal sites, and when full-scale coal-fired power generation begins operation, all coal ash must be disposed of using the current methods of disposal and effective utilization. It is expected that it will be difficult to do so. In addition, in order to establish a mass processing method for coal ash, it is essential to avoid environmental pollution and aim for reuse as much as possible. This is because, in a country with limited domestic resources and limited land, reuse, rather than simply dumping, contributes to the effective use of resources and land. In view of the above-mentioned points, the present invention has been developed using coal ash as a raw material with a high compressive strength, in order to enable early formation of soil when disposing of coal ash for sea level leveling or land reclamation, and to utilize it in large quantities as a resource. This product was created for the purpose of producing hardened soil, and is made from coal ash6, which is emitted during coal combustion.
0-90% by weight, quicklime or/and slaked lime 10-2
5% by weight, dihydrate gypsum, hemihydrate gypsum or/and 11
When producing a cured body using a mixed powder consisting of 5 to 25% by weight of type anhydrous gypsum as a raw material, 0.1 to 2.0 parts by weight of phosphoric acid and 10 to 60 parts by weight per 100 parts by weight of the mixed powder. After kneading the coal ash at room temperature with the addition of fresh water, quicklime or/and slaked lime (hereinafter referred to as quicklime etc.),
Then, dihydrate gypsum, hemihydrate gypsum or/and type 11 anhydrite gypsum (hereinafter referred to as dihydrate gypsum, etc.) are added and kneaded again at room temperature, and then this kneaded product is shaped into a predetermined shape using a mold or a molding container. A method of producing a hardened soil material with high compressive strength by curing at room temperature under a It provides:

Hereinafter, the configuration of the present invention will be explained in detail. In general, the typical properties of coal ash, such as components, composition, and particle size distribution, greatly depend on the coal's production area and combustion history. First of all, depending on the place of coal production, SlO2, Al2O3, CaO
．． Fe2O3, Na2O. ．． The blending ratio of components such as K2O is different. Secondly, the coal ash currently generated in Japan is mainly pulverized coal combustion ash, and depending on the generation site and collection method, it can be used for electrostatic precipitator (EP) attachment or clinker attachment. They are distinguished from yew and cinder ash, each having a different particle size distribution. Therefore, when producing a hydrated hardened material with high compressive strength using coal ash as the main raw material by curing at room temperature, the appropriate manufacturing conditions for the hydrated hardened material may vary depending on the composition and particle size distribution of the coal ash. different. Factors that have a large contribution rate as manufacturing conditions are the mixing ratio of raw material powder, kneading time and kneading temperature, and room temperature curing time. The main component of the hydrated hardened product produced by curing at room temperature is ettringite (3Ca0-Al2O3・3C
aS04.32H20) and various forms of calcium silicate hydrate (XCaO-YSiO2.ZH2O), but the one that contributes most as an early strength member is ettringite.

For this reason, the appropriate blending ratio of raw material powder is the one most favorable for the production of ettringite, with the amount of quicklime added being 10 to 25% by weight, and the amount of dihydrate gypsum being added being 5 to 5% by weight.
Limited to 25% by weight. Furthermore, the room temperature curing conditions are mainly due to the processing time. Since the treatment temperature is low in normal temperature curing, it usually takes a few days to a week for ettringite to form and exhibit a compressive strength of several kg/cm2 or more, which is sufficient to withstand normal civil engineering work. The particle size distribution of coal ash also has a large effect on the properties of the hydrated hardened material.

Generally, as the particle size of coal ash becomes smaller, that is, as the specific surface area becomes larger, the hydrated hardened material tends to exhibit a predetermined strength in a short curing period. This means that the ettringite production reaction is a through solution reaction.
n), the dissolution rate of Al2O3 is significantly lower than that of slaked lime and dihydrate gypsum, and the rate of formation of ettringite is Al. It can be estimated that it depends on the dissolution rate of O3. In this way, the properties of the hydrated hardened material are determined by the components and composition of the coal ash,
It is greatly influenced by manufacturing conditions such as the amount of other raw material powders added, amount of water mixed, kneading method, kneading time, and room temperature curing period, and each manufacturing condition must be appropriately selected according to the required characteristics of the hydrated material. It is necessary. Furthermore, a small amount of additives is effective in improving the performance of the hydrated and cured product and shortening the room temperature curing period. The object of the present invention is to increase the initial strength of a hydrated product and shorten the curing period at room temperature by adding a small amount of phosphoric acid.

The strength development of this hydrated hardened product is due to the production of ettringite, but the production rate of ettringite is
It depends on the dissolution rate of 3. This dissolution rate of Al2O3 is the same as that of Na2O3 in coal ash. It is significantly suppressed by the presence of K2O. Therefore, by kneading coal ash in advance with an aqueous solution containing a small amount of phosphoric acid, or by adding a small amount of phosphoric acid to coal ash in advance and adding water to this and kneading, Coal ash is washed with phosphoric acid to produce Na2O and K2O
As a result, the dissolution rate of Al2O3 is increased, the formation rate of ettringite is increased, and the strength is increased. In the present invention, there are various combinations of addition, mixing order, and kneading order of the raw material powder such as coal ash, quicklime, dihydrate gypsum, etc. and the additive phosphoric acid. However, as stated in the claims, the best method is to first knead coal ash and then add quicklime and dihydrate gypsum, focusing on the strength characteristics of the hardened product. ing.

Next, Examples and Comparative Examples will be explained.

The raw material coal ash in Examples and Comparative Examples was commercially available fly ash, and its properties are shown in Table 1. The test method for lime ash and hydrated hardened material is shown below.

The Blaine specific surface area was measured using a powder specific surface area measuring instrument SS-100 manufactured by Shimadzu Corporation, and by an air permeation method.
The compressive strength test uses 20 x 20 x 20 (Mm) as a test piece.
A universal testing machine manufactured by Instron was used as the testing device. The test method was based on the constant deflection method.
In Examples and Comparative Examples, room temperature curing was carried out indoors without direct sunlight. Example 1 1.0 parts by weight of phosphoric acid was dissolved in 45 parts by weight of water and 85 parts by weight of coal ash was dissolved.
After kneading parts by weight at room temperature, 10 parts by weight of quicklime, 2 parts by weight
5 parts by weight of water gypsum was added and kneaded again at room temperature to form a slurry, and this slurry was poured into a mold to obtain a molded body.

This molded product was cured at room temperature for 3 days to obtain a hydrated and cured product.
The properties of the hydrated and cured product were as shown in Table 2. Example
2 Dissolve 0.5 parts by weight of phosphoric acid in 45 parts by weight of water and make 85 parts by weight of coal ash.
After kneading parts by weight at room temperature, 10 parts by weight of quicklime, 2 parts by weight
5 parts by weight of water gypsum was added and kneaded again at room temperature to form a slurry, and this slurry was treated in the same manner as in Example 1 to obtain a hydrated hardened product.

The properties of the hydrated and cured product were as shown in Table 2. Comparative example
1. After kneading 45 parts by weight of water and 85 parts by weight of coal ash at room temperature, 10 parts by weight of quicklime and 5 parts by weight of dihydrate gypsum were added and kneaded again at room temperature to form a slurry. A similar treatment was performed to obtain a hydrated cured product.

The properties of the hydrated and cured product were as shown in Table 2. Comparative example
2 Dissolve 2.5 parts by weight of phosphoric acid in 45 parts by weight of water and prepare 85 parts by weight of coal ash.
After kneading parts by weight at room temperature, 10 parts by weight of quicklime, 2 parts by weight
5 parts by weight of water gypsum was added and kneaded again at room temperature to form a slurry, and this slurry was treated in the same manner as in Example 1 to obtain a hydrated hardened product.

The properties of the hydrated and cured product were as shown in Table 2. Comparative example
3 Dissolve 1.0 part by weight of NaOH in 45 parts by weight of water and add 8 parts by weight of coal ash.
After kneading 5 parts by weight at room temperature, 10 parts by weight of quicklime, 2
5 parts by weight of water gypsum was added and kneaded again at room temperature to form a slurry. This slurry was treated in the same manner as in Example 1, but as shown in Table 2, no hardened product was obtained.

Table 2 shows that the addition of 0.1 to 2.0 parts of phosphoric acid can improve the initial strength of the hydrated and cured product after curing at room temperature.

As explained above, according to the present invention, coal ash which is an exhaust product during coal combustion, quicklime and/or slaked lime which is an inexpensive raw material, dihydrate gypsum, hemihydrate gypsum or/and 11
By using molded anhydrous gypsum, adding a small amount of phosphoric acid, kneading it with fresh water, and then curing at room temperature, it is possible to easily and inexpensively produce a hydrated hardened product with high compressive strength. The present invention is extremely useful as a technology that effectively utilizes coal ash and contributes to the production of soil materials for leveling and land preparation in the fields of civil engineering and architecture.

Claims (1)

[Claims] 1. 60 to 90% by weight of coal ash discharged during coal combustion,
Quicklime or/and slaked lime 10-25% by weight, dihydrate gypsum, hemihydrate gypsum or/and type II anhydrous gypsum 5-2
When producing a cured body using a mixed powder containing 5% by weight as a raw material, 0.1 to 2.0 parts by weight per 100 parts by weight of the mixed powder.
After adding parts by weight of phosphoric acid and 10 to 60 parts by weight of fresh water and kneading coal ash at room temperature, quicklime or/and slaked lime, dihydrate gypsum, hemihydrate gypsum or/and
Curing using coal ash as the main raw material, which is characterized by adding type II anhydride gypsum and kneading it again at room temperature, then molding this kneaded product using a mold or a molding container, and then curing it at room temperature. How the body is manufactured. 2 60-90% by weight of coal ash emitted during coal combustion,
Quicklime or/and slaked lime 10-25% by weight, dihydrate gypsum, hemihydrate gypsum or/and type II anhydrous gypsum 5-2
When producing a cured body using a mixed powder containing 5% by weight as a raw material, 0.1 to 2.0 parts by weight per 100 parts by weight of the mixed powder.
After adding parts by weight of phosphoric acid and 10 to 60 parts by weight of fresh water and kneading coal ash at room temperature, quicklime or/and slaked lime, dihydrate gypsum, hemihydrate gypsum or/and
A hardened material made from coal ash as the main raw material, which is characterized by adding Type II anhydrite, kneading it again at room temperature, solidifying the kneaded material without molding it into a specific shape, and then curing it at room temperature. Production method.