JPS5969465A - Manufacture of hardened body from coal ash - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses coal ash discharged during coal combustion as a main raw material.
A method of producing a hardened material by ~, specifically, kneading a mixed powder obtained by adding slaked lime and/or quicklime to coal ash, and dihydrate gypsum, hemihydrate gypsum or/and type water gypsum with water. The present invention also 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 mass consumption of coal as a secondary energy source is the treatment of the large amount of coal ash generated during coal combustion.

During coal combustion, coal ash is usually generated which is approximately 10-20% by weight of the amount of coal used. The so-called pulverized coal combustion ash generated from a normal pulverized coal combustion/combustion boiler is classified into bottom ash, shishida ash, and 7 ash, depending on the molten ash produced, of which fly ash accounts for the majority of the generated amount. Conventionally, in Japan, a part of the 7 lion sieves has been reused as cement mixed phase ('), cement raw material, etc., and the rest has been disposed of in landfills, etc. However, if only the current method of reuse is used, the future Demand for coal ash cannot be expected to be sufficient to cope with the enormous amount of coal ash that will be generated, and on the other hand, the current disposal of coal ash in landfills, etc. is becoming increasingly difficult due to stricter environmental regulations. Difficulty in securing land 1. It is becoming more and more difficult to process all the coal ash generated by the current coal ash disposal and effective utilization methods when a full-scale coal-fired power plant goes into operation. -1) When evaluating mass processing technology for coal ash, it is necessary to aim for environmental pollution and reuse as much as possible. In our country, it is important to reuse coal ash as a resource rather than simply dumping it.

In view of the points listed in "L," the present invention is suitable for use in the civil engineering sector, such as using coal ash as soil improvement material for soft ground, soil reclamation material for sea surface reclamation and land reclamation, and road base material for road construction.
In order to utilize coal ash as a raw material, it was proposed to produce a hardened clay body with high compressive strength. or/and quicklime (hereinafter abbreviated as slaked lime) 5 to 40% by weight, preferably 15 to 30% by weight
, dihydrate gypsum, hemihydrate gypsum, or/and ■ type hydrogypsum (hereinafter abbreviated as dihydrate gypsum, etc.) to a mixed powder of 4 to 40% by weight, preferably 5 to 20% by weight, and 10 to 60% by weight.
When producing a cured product by adding water in an amount of water of 100% by weight (weight% of water added to 100% by weight of powder), after adding water to the mixed powder and kneading, this kneading The product is molded using a mold or a molding container, and then the voids of the molded product are filled with water, and then the mechanical strength is increased to 80-1 (by treating with steam at 10°C). The present invention provides a method for producing a large cured body.

Hereinafter, the structure 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, 5iOz, Al2O3, Ca
The blending ratio of ingredients such as O1Na20 and K2O is different,
Second, the coal ash currently generated in Japan is mainly pulverized coal combustion ash, and the particle size distribution differs depending on the location and collection method. For this reason, when producing a water-phase hardened body with high mechanical strength using coal ash as the main raw material by steam treatment, the appropriate manufacturing conditions for the hydrated hardened body differ slightly depending on the composition and particle size distribution of the coal ash. 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 components of the hydrated hardened product produced by steam treatment are Ettringai 1~(3CaO・Al2O3・3CaSO
4.32HzO), and ettringite, which is a silicate hydrate of various forms (XCaO=ySi02.zH20), contributes most to the early strength development of gar.

For this reason, the mixing ratio of the raw material powder should be the most convenient for the production of ettringite, and the addition of slaked lime @ 5 to 40% by weight, preferably 15 to 30% by weight, dihydrate gypsum, etc. The amount added is limited to 4 to 40% by weight, preferably 5 to 20% by weight.

Furthermore, the steam treatment conditions are mainly determined by treatment temperature and treatment time.

In general, when the steam treatment temperature is low and the steam treatment time is short, the reaction progresses slowly and the hydrated hardened product becomes a calcium monodulfate aqueous phase product (3C).
It is made of a mixture of aO・Al2O3・CaSO4・12H20), dihydrate gypsum, and ettringite, and has low strength. As the reaction progresses, the amount of ringite 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 means that the production reaction of ettringite is a through solution reaction.
Furthermore, the dissolution rate of alumina (Al2O,1) contained in coal ash is smaller than that of slaked lime and dihydrate gypsum, and it is estimated that the rate of ettringite formation depends on the dissolution rate of alumina. Because you can. Like this.

The properties of hydrated hardened products are greatly influenced by manufacturing conditions such as the components and composition of coal ash, the amount of other raw material powders added, the amount of water mixed, the cross-mixing method and kneading time, and the steam treatment temperature and treatment time. Direct running means appropriately selecting each manufacturing condition according to the required characteristics of the Japanese hardened product.

In the wood invention, raw mixed powder and water are kneaded and molded using a formwork or a molding container, and then the voids of this molded body are filled with water.
The objective is to improve the strength of the aqueous phase cured product by subjecting it to steam treatment after 1 hour of cooling.

In the wood invention, the amount of mixed water @ fl O ~ 60% by weight is set, 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, if the amount of water mixed is increased, the fluidity increases and it becomes difficult to solidify, but the maximum amount of water mixed is about 60% by weight. Therefore, in end 1, the amount of mixed water in Bokke 1~I is 3
It is 0 to 50% by weight.

Examples and comparative examples will be explained below.

The raw material coal ash in Examples and Comparative Examples is commercially available fly ash, and its composition and properties are shown in Table 1.

The plain specific surface area measurement was carried out using a powder specific surface area measuring instrument 5S-100 manufactured by Koguruma Manufacturing Co., Ltd. by an air permeation method.

For the bending strength test, a 20 x 20 x 80 (tomo) test piece was used, and for the compressive strength test, a 20 x 20 test piece was used.
X2.0 (fighting) was used, and a universal testing machine manufactured by Instron was used as the testing device. The test method was 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 1 805 parts of coal ash, 12.5 parts of slaked lime, 7 parts of dihydrate gypsum,
After kneading 35 parts of water, the kneaded product was poured into a mold and molded, and the voids of this molded product were filled with water, and then treated with steam at 95°C for 15 hours to hydrate. A cured product was obtained. Note that the amount of free water in the molded article before steam treatment was 25%. The properties of the obtained hydrated and cured product were as shown in Table 2.

Example 2 805 parts of coal ash, 12.5 parts of slaked lime, 7 parts of dihydrate gypsum,
After kneading 35 parts of water, pour this kneaded material into the mold 1-
Then, the voids of this molded body were filled with water, and then treated with steam at 95° C. for 15 hours to obtain a water phase cured body. The amount of free water in one compact before steam treatment is 2
It was 0%. The properties of the obtained aqueous phase cured product were as shown in Table 2.

Ratio 1 bite example 1 Coal ash 80.5 + < (S, slaked lime 125 parts, dihydrate gypsum 7) η After kneading 35 parts of water, this kneaded material was poured into a mold and molded, and then After filling the voids of this molded body with water, it is treated with steam at 95°C for 15 hours]7
A water phase cured product was obtained. The amount of free water in the molded product before steam treatment was 2%. The properties of the obtained aqueous phase cured product were as shown in Table 2.

(Leaving space below) From Table 2, a strong water-phase cured product can be produced by thoroughly filling a molded product made by mixing the raw material powder with water, soaking it, and then subjecting it to steam treatment. I know it's a city.

As explained above], according to the great invention, coal ash, which is an exhaust product during coal combustion, slaked lime, which is an inexpensive abrasion, and/or quicklime, dihydrate gypsum, hemihydrate gypsum, and/or and UII type 911 (1) It is possible to easily and inexpensively produce a water-phase hardened body with high compressive strength by using hydrogypsum and kneading it with water and then steaming it. The uninvented method is to utilize coal ash effectively.1111-1-1 Benefits as a technology that contributes to the production of paulownia wood for land reclamation, land development, road construction, etc. in the field of wood and construction. It is.

Claims (1)

[Claims] 1 50-90% by weight of coal ash emitted during coal combustion,
Slaked lime - 1'ta/fi/ and quicklime 5-40% by weight,
When producing a hardened body by adding water in an amount of 10 to 60% by weight to dihydric gypsum, hemihydrate gypsum or/and l%p anhydrous gypsum 4 to 40% by weight or ranal mixed powder, After adding water to the mixed powder and kneading it, the kneaded product is molded using a mold cutter or a molding container, and then the voids of this molded product are filled with water, and then 80 to 10 A method for producing a hardened product using coal ash as a main raw material, characterized by treating with steam at 0°C.