JPS6324941B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a hardened body using coal ash discharged during coal combustion as a main raw material, specifically, to coal ash, slaked lime or/and quicklime, and dihydrate gypsum, hemihydrate gypsum or/and type anhydrous gypsum are added. Knead the mixed powder with water,
The present invention relates to a method for producing a hydrated material with high mechanical strength by curing at room temperature. In recent years, the development of alternative energy sources for oil in order to reduce our dependence on oil has become a national issue in our country, and coal energy is attracting attention as one of the pillars of energy. One of the challenges in the practical application of coal utilization technology to cope with the large consumption of coal as a primary energy source is the disposal of large amounts of coal ash generated during coal combustion. When burning coal, usually almost 10 to 20 of the coal usage
% coal ash is generated. The so-called pulverized coal combustion ash generated from a typical pulverized coal combustion boiler is classified into bottom ash, cinder ash, and fly ash, depending on where it is generated, and of these, fly ash accounts for the majority of the amount generated. Traditionally in Japan, a portion of fly ash has been reused as cement admixtures, cement raw materials, etc.
The rest is disposed of in landfills. However, it is not possible to expect enough demand to meet the huge amount of coal ash that will be generated in the future through current recycling methods alone. With the tightening of environmental regulations, it is becoming increasingly difficult to secure land for coal ash disposal. It is expected that it will be difficult to dispose of this amount of coal ash. Furthermore, when considering mass processing technology for coal ash, it is necessary to aim for reuse as much as possible without causing environmental pollution. This is because in a country with limited domestic resources and limited land, it is important to reuse coal ash as a resource rather than simply dumping it. In view of the above points, the present invention utilizes coal ash in large quantities in the civil engineering sector, such as as a soil material for sea surface reclamation and land reclamation, as a soil improvement material for soft ground, and as a roadbed material for conduit construction. This was made with the aim of producing a hardened soil with high bending strength using coal ash as a raw material.
Weight%, preferably 60 to 80% by weight, slaked lime or/and quicklime (hereinafter abbreviated as slaked lime etc.) 5
~40% by weight, preferably 15-30% by weight, 4-40% by weight of dihydrate gypsum, hemihydrate gypsum or/and type anhydrous gypsum (hereinafter abbreviated as dihydrate gypsum etc.),
Preferably, 10 to 20% by weight of mixed powder is added.
When producing a cured body by adding 60% by weight of water (weight% of water added to 100% by weight of powder), 0.1 to 2 parts by weight per 100 parts by weight of mixed powder. of sulfuric acid is added to water in advance and kneaded with the mixed powder, or added and kneaded when water is added to the mixed powder, then the kneaded product is shaped using a form frame or a molding container, and then this The present invention provides a method for producing a hardened body using coal ash as a main raw material, characterized in that the formed body is treated with steam at 80 to 100°C. 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, it depends on where the coal comes from.
The proportions of ingredients such as SiO ₂ , Al ₂ O ₃ , CaO, Fe ₂ O ₃ , Na ₂ O, K ₂ O are different, and secondly, the coal ash currently generated in Japan is mainly pulverized coal combustion ash. Yes, the particle size distribution varies depending on the location and collection method. Therefore, when producing a hydrated hardened material with high mechanical strength using steam treatment using coal ash as the main raw material, 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 blending ratio of raw material powder, kneading time, steam treatment temperature, and steam treatment time. Note that it is desirable to use normal pressure steam as the steam. The main component of the hydrated hardened product produced by steam treatment is ettringite (3CaO・Al ₂ O ₃・
3CaSO ₄ 32H ₂ O), various forms of calcium silicate hydrate (xCaO ySiO ₂ zH ₂ O),
Etrin guides contribute most to early strength development. For this reason, the appropriate mixing ratio of the raw material powder is the one most favorable for the production of ettringite, and the amount of slaked lime added is 5 to 40% by weight, preferably 15 to 30% by weight, and the addition of dihydrate gypsum, etc. The amount is limited to 4-40% by weight, preferably 5-20% by weight. Furthermore, the steam treatment conditions are mainly determined by treatment temperature and treatment time. Generally, when the steam treatment temperature is low and the steam treatment time is short, the reaction progresses slowly, and the hydrated hardened product becomes calcium monosulfo aluminate hydrate (3CaO・Al ₂ O ₃・CaSO ₄・
12H ₂ O), dihydrate gypsum, and ettringite, and has low strength. As the reaction progresses, the amount of ettringite produced increases and its strength also increases. 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 with a shorter curing time. This is because the formation reaction of ettringite is a through solution reaction, and the dissolution rate of alumina (Al ₂ O ₃ ) contained in coal ash is significantly lower than that of slaked lime and dihydrate gypsum. This is because it can be estimated that the production rate of ettringite depends on the dissolution rate of alumina. in this way,
The properties of the hydrated hardened product are determined by the components and composition of the coal ash,
It is greatly affected by manufacturing conditions such as the amount of other raw material powders added, the amount of water mixed, the kneading method and kneading time, and the steam treatment temperature and treatment time, and each manufacturing condition should be adjusted appropriately according to the required characteristics of the hydrated hardened product. It is necessary to select the The purpose of the present invention is to improve the bending strength of the hydrated product after steam treatment by adding a small amount of sulfuric acid during kneading of mixed powder and water, and the amount of sulfuric acid added is The amount is preferably 0.1 to 2 parts by weight per 100 parts by weight of the raw material mixed powder. Note that sulfuric acid may be dissolved in water in advance or may be added when kneading the mixed powder and water, but it is preferable to carry out the kneading at the same time.In the present invention, the amount of water mixed is ~60% by weight, but if the amount of mixed water is reduced, the strength will increase, but the moldability will deteriorate, and if the amount of mixed water is less than about 10% by weight, molding will not be possible. In addition, when the amount of mixed water is increased, the fluidity increases and it becomes difficult to solidify, and the amount of mixed water is about 60% by weight as the limit. Therefore, in the present invention, the desirable amount of water to be mixed is 30 to 50% by weight. Next, Examples and Comparative Examples will be described.
The raw material coal ash in the examples and comparative examples is commercially available fly ash, and its composition and properties were
Shown in the table.

[Table] The test methods for coal ash and hydrated hardened bodies are shown below. The Blaine specific surface area was measured using a powder specific surface area measuring instrument SS-100 manufactured by Shimadzu Corporation, using the air permeation method. The bending strength test uses 20×20× as a test piece.
80 (mm) was used, and for the compressive strength test, a 20 x 20 x 20 (mm) test piece was used as the test piece, and 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. Details of Examples and Comparative Examples are shown in Table 2. Example 1 81.5 parts of coal ash, 12.5 parts of slaked lime, 6 parts of dihydrate gypsum
1 part, 0.5 parts of sulfuric acid, and 35 parts of water to make a slurry.
This slurry was injected into a mold to obtain a molded body.
This molded body was treated with steam at 95° C. for 15 hours to obtain a hydrated and cured body. The properties of the hydrated and cured product were as shown in Table 2. Example 2 81.5 parts of coal ash, 12.5 parts of slaked lime, 6 parts of dihydrate gypsum
1 part, 1.0 part of sulfuric acid, and 35 parts of water to make a slurry.
This slurry was injected into a mold to obtain a molded body.
This molded body was treated with steam at 95° C. for 15 hours to obtain a hydrated and cured body. The properties of the hydrated and cured product were as shown in Table 2. Comparative example 1 82.5 parts of coal ash, 12.5 parts of slaked lime, 6 parts of dihydrate gypsum
1 part and 35 parts of water were kneaded to form a slurry, and this slurry was poured into a mold to obtain a molded body. This molded body was treated with steam at 95° C. for 15 hours to obtain a hydrated and cured body. The properties of the hydrated and cured product were as shown in Table 2. Comparative example 2 77.5 parts of coal ash, 12.5 parts of slaked lime, 10 parts of dihydrate gypsum
1 part and 35 parts of water were kneaded to form a slurry, and this slurry was poured into a mold to obtain a molded body. This molded body was treated with steam at 95° C. for 15 hours to obtain a hydrated and cured body. The properties of the hydrated and cured product were as shown in Table 2. Comparative example 3 81.5 parts of coal ash, 12.5 parts of slaked lime, 6 parts of dihydrate gypsum
1 part, 2.5 parts of sulfuric acid, and 35 parts of water to make a slurry.
This slurry was injected into a mold to obtain a molded body.
This molded body was treated with steam at 95° C. for 15 hours to obtain a hydrated and cured body. The properties of the hydrated and cured product were as shown in Table 2.

Table 2 shows that by adding sulfuric acid during kneading of the raw material powder and water and then subjecting it to steam treatment, a hydrated hardened product with high bending strength can be produced. As explained above, according to the present invention, coal ash, which is an exhaust product during coal combustion, slaked lime and/or quicklime, which is an inexpensive raw material, dihydrate gypsum, hemihydrate gypsum, and/or type anhydrous gypsum are used, By kneading with water and then steaming, it is possible to easily and inexpensively produce a hydrated material with high bending strength. It is useful as a technology that contributes to the production of soil materials for land reclamation, land reclamation, road construction, etc. in the field.

Claims (1)

[Claims] 1 50-90% by weight of coal ash discharged during coal combustion, 5-40% by weight of slaked lime or/and quicklime,
When manufacturing a hardened body by adding water in an amount of 10 to 60% by weight to a mixed powder consisting of 4 to 40% by weight of dihydrate gypsum, hemihydrate gypsum or/and type anhydrous gypsum, 100% of the mixed powder Either 0.1 to 2 parts by weight of sulfuric acid is added to water in advance and kneaded with the mixed powder, or it is added when water is added to the mixed powder and kneaded, and then the kneaded product is molded into a mold or molded. A method for producing a hardened body using coal ash as a main raw material, which comprises forming the body using a container or the like, and then treating the formed body with steam at 80 to 100°C.