JPS60191046A - Manufacture of cured body comprising coal ash as main raw material - 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 relates to a method for producing a hardened material using coal ash as a main raw material discharged during coal combustion. A mixed powder obtained by adding / and ■ type water gypsum is kneaded with water, and then this kneaded material is cured in a humid atmosphere, and then the mechanical strength is improved by normal pressure steam treatment at 80 to 100°C. The present invention relates to a method for producing large hydrated and cured bodies.

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 problem of processing and disposing of the multi-wire coal ash generated during coal combustion.

When burning coal, the amount of coal used is usually approximately 10 to 20 W.
t% of coal ash is generated. The so-called pulverized coal combustion ash generated from a normal coal-fired boiler is classified into bottom ash, cinder ash, and fly ash, depending on where it is generated, with fly ash accounting for the majority of the amount generated. Conventionally, in Japan, a portion of fly ash has been reused as cement admixture, cement raw material, etc., and the rest has been disposed of in landfills, etc. However, it is not possible to expect demand to increase enough to cope with the huge amount of coal ash that will be generated in the future by reusing conventional methods alone. With the tightening of regulations related to environmental conservation, it is becoming difficult to secure land for coal ash disposal. It is expected that it will be difficult to dispose of all the coal ash that is generated. In addition, when considering methods for mass disposal of 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 was made for the purpose of producing a hardened body with high compressive strength using coal ash as a raw material in order to utilize coal ash in large quantities in the water supply and construction fields. 60 to 35 wt%, slaked lime or/and quicklime (hereinafter abbreviated as slaked lime, etc.) 10 to 25 wt%, 2
Water gypsum, hemihydrate gypsum or/and type water gypsum (
A mixed powder consisting of 5 to 25 wt% (hereinafter abbreviated as dihydrate gypsum, etc.) is mixed with an amount of water of 20 to B□wt% (powder 100w
After adding and kneading water in an amount (Wj, %) of water to be added to t%, the kneaded product is molded using a mold or a molding container, and then the molded body is heated at 35 to 75°C1 relative humidity. After curing for 5 to 25 hours in a humid atmosphere of 80% or more,
The present invention provides a method for producing a cured product with high mechanical strength by treating with normal pressure steam at 80 to 100°C.

The present invention also provides a method for producing a granular hardened body with high mechanical strength by crushing the hardened body, that is, 60 to 85 wt% of coal ash discharged during coal combustion, 10 to 25 wt% of slaked lime and/or quicklime, A mixed powder of 5-25 wt % of dihydric gypsum, hemi-hydrate gypsum and/or type water gypsum is mixed with 20-80W 7% of water and then kneaded. After curing for 5 to 25 hours in a humid air atmosphere with a relative humidity of 80% or more at °C1,
The present invention provides a method for producing a hardened granular material having high mechanical strength by treating the hardened material with normal pressure steam at 80 to 100°C and then pulverizing the hardened material into a hardened granular material having a particle size of 4 Q +, qm or less. be.

Hereinafter, the configuration of the present invention will be explained in detail. In general, the typical properties of coal ash, such as its components, composition, particle size, and fabric? L+
Ota (exist) is included in the records of the people working in the open coal fields at the time of the destruction.

First of all, depending on the place of coal production, 5i02, Al2O
3.Cab, Na20SK20, etc.) The blending ratio of the constituent components is different. Secondly, the coal ash currently generated in our country is mainly pulverized coal combustion ash, and the particle size distribution differs depending on the hot spring where it is generated and the method of collection.

For this reason, when producing a hardened product with high mechanical strength using coal ash as a main raw material by atmospheric pressure steam treatment, the appropriate manufacturing conditions for the hardened product differ slightly depending on the component composition and particle size distribution of the coal ash. Factors that have a large contribution rate as manufacturing conditions are the mixing ratio of raw material powder, amount of water mixed, kneading method, humid air curing conditions, and steam treatment conditions. Note that normal pressure steam is used during the steam treatment.

The main component of the hydraulic hardening material produced by steam treatment is
4.32H2o) and various forms of calcium silicate hydrate (xcaO-yS:LO2.zH20), but the one that contributes most to early strength development is ettringite.

Therefore, the mixing ratio of the raw material powder should be the most favorable for the production of ettringite, and the amount of slaked lime added should be 10 to 25 wt%, and the amount of dihydrate gypsum added should be 5 to 5 wt%.
Limited to 25wt%.

The particle size distribution of coal ash also has a great influence on the properties of the water-cured 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 shorter time. This is the ettringite production reaction through solution reaction.
aclon) F reeds, and the rate at which alumina (A, 1□03) contained in stone and ash is leached into water is higher than that of other raw materials, such as slaked lime, dihydrate gypsum, etc. This is because it is estimated that the production rate of ettringite is extremely small and depends on the dissolution rate of alumina. In this way, when producing hydraulic hardened bodies using coal ash as the main raw material,
In order to satisfy the required performance for the hydrated hardened material, the amount of other raw material powders added, the amount of water per shot, the kneading method, the moist air curing conditions, and the steam treatment conditions are appropriately adjusted according to the component composition and particle size distribution of the coal ash. It is necessary to make a selection.

In the present invention, a raw material mixed powder and water are kneaded, molded in a mold or a molding container, and then this molded product is
The objective is to significantly shorten the humid air curing time by performing humid air curing at °CSA/inspection humidity of 80% or more.

(Left below) In the production of cured products, relatively low temperatures (e.g. room temperature to 7.5
The mechanical strength of the cured product is only 1.
It's not too big. To achieve compressive strength almost equivalent to concrete (for example, 800 kg/crj or more),
A humid air curing process at a low temperature and a normal pressure steam treatment process at 80 to 100°C are essential. In this moist air curing process,
At a humid air curing temperature of 20 to 30°C, near room temperature, it takes 3 to 7 days to achieve a compressive strength of approximately 300 kg/cl1 or more after normal pressure steam treatment, and a long period of time is required to produce the cured product. shall be. However, the present inventors have found through repeated experiments that the humid air curing period can be significantly shortened by setting the humid air curing temperature to 35 to 75°C. The present invention has been made based on this knowledge, and thereby significantly simplifies the process for industrial large-scale production of the cured product.

The present invention also provides a method for producing not only a cured product having a predetermined shape by cast molding or pressure molding, but also a granular cured product obtained by pulverization. That is, when producing a granular hardened body by pulverization, it is not necessary to mold it into a specific shape in advance, making it suitable for large-scale production. For crushing after steam treatment, a conventional powder 1j4''4 such as an impact crusher or a show crusher can be used.

Regarding the pulverization method, it is desirable to select a pulverizer and operating conditions so as to obtain a particle size distribution and particle shape suitable for the intended use of the granular hardened product.

Next, an example and a ratio 1 bite case will be described.

The raw material coal ash in the examples is commercially available fly ash, and the composition and properties are shown in Table 1. Blaine specific surface area measurement is performed using powder specific surface measurement device 5S-10 manufactured by Shimabara Seisakusho.
The air permeation method was used using type 0.

(The following is a blank space) Table 2 shows examples and comparative examples of the first invention. In Table 2, the compressive strength test uses 4 as a test piece.
For the bending strength test, a 40 x 40 x 160 (ux) test piece was used as the test piece, and an Instron universal testing machine was used as the testing device. The test method was the constant deflection method. Further, Tables 3 and 4 show examples of the second invention.

Example 1 Coal ash 8QVi7t, % with the composition and properties shown in Table 1
After adding and kneading 34 wt% of water to a mixed powder consisting of 12 wt% of slaked lime and 3 wt% of dihydrate gypsum, the kneaded product was heated at 40°C in a humid atmosphere of 95 to 100% relative humidity for 24 hours. After curing for 1 hour, it was treated with normal pressure steam at 92°C for 10 hours. The properties of the obtained cured product were as shown in Table 2.

Example 2 A mixed powder of sowt% coal ash, 12wt% slaked lime, and 8wt% dihydrate lime having the composition and properties shown in Table 1 was mixed with water in an amount of 34wt%. After curing for 15 hours at 50°C in a humid air atmosphere with a relative humidity of 95-100%, it was cured for 10 hours in normal pressure steam at 92°C.
Time processed. The properties of the obtained cured product were as shown in Table 2.

Example 3 After adding and kneading 34 wt% of water to a mixed powder consisting of 8 Qwt% of coal ash, 12 wt% of slaked lime, and 3 wt% of dihydrate gypsum with the composition and properties shown in Table 1, this kneaded product was After curing for 10 hours in a humid air atmosphere at 70°C and relative humidity of 95-100%, it was treated with normal pressure steam at 92°C for 10 hours. The properties of the obtained hard body were as shown in Table 2.

Comparative Example 1 After adding and kneading 34 wt% of water to a mixed powder consisting of 3 Qwt% of coal ash, 12 wt% of slaked lime, and 8 wt% of dihydrate gypsum with the composition and properties shown in Table 1, this kneaded product was After curing for 10 hours in a humid air atmosphere at 80°C and relative humidity of 95-100%, it was treated with normal pressure steam at 92°C for 10 hours. The properties of the obtained cured product were as shown in Table 2.

Comparative Example 2 After adding and kneading 34 wt% of water to a mixed powder consisting of 8 Qwt% of coal ash, 12 wt% of slaked lime, and 8 wt% of dihydrate gypsum with the composition and properties shown in Table 1, this kneaded product was After curing for 70 hours in a humid air atmosphere at 20° C. and relative humidity of 95 to 100%, it was treated with normal pressure steam at 92° C. for 10 hours. The properties of the obtained cured product were as shown in Table 2.

Comparative Example 3 After adding and kneading 84 wt% of water to a mixed powder consisting of 8 Qwt% of coal ash, 12 wt% of slaked lime, and 8 wt% of dihydrate gypsum with the composition and properties shown in Table 1, this kneaded product was After curing for 120 hours in a humid air atmosphere with a relative humidity of 95 to 100% at 20°C, the
Time processed. The properties of the obtained cured product were as shown in Table 2.

(Left below) Also, 79 parts by weight of coal ash having the composition and properties shown in Table 1,
18 parts by weight of slaked lime, 8 parts by weight of dihydrate gypsum, and 30 parts by weight of water were mixed, and then this kneaded product was heated to 45°C, relative humidity 95%.
After curing for 20 hours in ~100% humid air atmosphere, 92
A cured product before pulverization was obtained by treating with normal pressure steam at °C for 15 hours. The compressive strength and bending strength of this cured product were 4 as shown in Table 3.

(The following is a blank space) Example 4 The cured product shown in Table 3 before crushing was crushed in a show crusher to give 40 to 20 fl 16.4% and 20 to 10 fl.
19.4%, 10-5 pm 23.2%, 5-1.7 pm
15.8%, 1.7-0.074 23.0%, 0.
A granular cured product having a particle size distribution of 0.074 or less and 2.2% was obtained. The properties of this granular cured product were as shown in Table 4.

Example 5 The cured product before crushing shown in Table 8 was crushed in a show crusher, and the results were 5-1.7H47.0%, 1.7-0.074
A granular hardened product with a particle size distribution of 50.6% and 0.074 or less and 2.4% was obtained. The properties of this granular cured product were as shown in Table 4.

(Margin below) The unconfined compressive strength in Table 4 was measured after adding 10% cement and curing in water for 7 days (at the time of tamping corresponding to modified CBH). Ushita CB
R is given by the following formula from the penetration resistance of a penetration rod with a diameter of 5α according to J Engineering 5A1211 (subgrade soil bearing capacity ratio test method).

The modified CBR is divided into three layers in the vertical direction and compacted to a degree of compaction of 95% of the maximum dry density when each layer is tamped 92 times in accordance with J.S.A. 1210 (Test method for soil compaction by compaction). This refers to the CBR after corresponding 4 days of water immersion.

From Tables 2 to 4, the raw material powder and water are kneaded and 35 to
After curing in humid air at 75°C1 relative humidity 80% or more, 8
It can be seen that by performing steam treatment with normal pressure steam at 0 to 100°C, a hardened hardened body and a granular hardened body with high strength can be produced in a very short period of time.

As explained above, according to the present invention, slaked lime and/or quicklime, which are inexpensive raw materials, dihydrate gypsum, hemihydrate gypsum, and/or type water gypsum are added to coal ash, which is an exhaust product during coal combustion. By adding it and subjecting it to atmospheric pressure steam treatment after curing in a humid air at 35 to 75°C, it is possible to easily produce a hardened product with high strength and a granular hardened product obtained by pulverization in a short time. The present invention is extremely useful as a technology that contributes to the production of various building materials and structural materials in the field of construction using coal ash.

Claims (1)

[Claims] 1. 60 to 85 wt% of coal ash discharged during coal combustion,
Slaked lime or/and quicklime 1O~25wt%, dihydrate gypsum, hemihydrate gypsum or/and type water gypsum 5~2
After adding and kneading water in an amount of 20 to 8 Q wt% to the mixed powder consisting of 5 wt%, the kneaded product is molded using a mold or a molding container, and then this molded body is heated to 35 wt%.
~75°C1 5~ in a humid atmosphere with a relative humidity of 80% or more
A method for producing a hardened material using coal ash as a main raw material, which comprises curing for 25 hours and then treating with atmospheric pressure steam at 80 to 100"C. 2. 60 to 85 wt% of coal ash discharged during coal combustion. ,
Slaked lime or/and quicklime 10-25 wt%, dihydrate gypsum, hemihydrate gypsum or/and type water gypsum 5-2
20~R (1 wt% flood 7
To the amount of 7'6L-Minato 1. Encouragement 1. After curing the kneaded product for 5 to 25 hours in a humid air atmosphere at 35 to 75°C and a relative humidity of 80% or more, it is treated with normal pressure steam at 80 to 100'C, and then the particle size is 4QMM or less. A method for producing a hardened product using coal ash as a main raw material, the method comprising pulverizing coal ash into a granular hardened product.