JPH07108827B2 - Method for producing a porous fired and hardened body using coal ash as a main raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses coal ash as a main raw material, which can be used as a material for blocks for civil engineering and landscaping, boards for construction, etc. The present invention relates to a method for producing a porous calcination cured product.

(Prior art) At present, coal-fired power plants are equipped with 11.47 million KW and 49 facilities, but since there are 17.1 million KW and 22 facilities under planning and construction, around 2000, there will be 28.57 million KW. It is estimated that the number will increase dramatically to 71 units. As a result, the amount of coal ash generated is expected to increase significantly from the present annual amount of 3.9 million tons.

At present, of the coal ash generated, only a small amount is effectively used, and most of it is dumped at landfills or ash dumps. However, there are many problems associated with the waste treatment method, and technical development for effective utilization is desired.

The fields of effective utilization of coal ash are for cement, roads, concrete admixtures, building materials, etc., and can be roughly classified into either powder as a raw material or solidified.

As is well known, coal ash does not solidify as it is,
Many solidification methods have been proposed so far.

For example:

(A) In Japanese Examined Patent Publication No. 63-17791, after coal or ash is mixed with water or a caustic soda or sodium silicate aqueous solution, pressure molding is performed,
Method of drying and sintering.

(B) In Japanese Patent Laid-Open No. 57-145064, a method of adding cement to coal ash, kneading the mixture with water or seawater, and performing pressure molding and steam curing.

(C) In Japanese Patent Laid-Open No. 62-21775, a method of adding water and a foaming agent to a mixture of coal ash and cement, kneading and foaming the mixture into a predetermined molded body, and curing in a room temperature and humid air.

(D) In JP-A-56-69262, a method of adding a binder to a mixture of coal ash having a specific composition and a degassable granular material, molding the mixture under a specific pressure, and sintering at a specific temperature.

(E) In JP-A-61-127679, a method of molding and curing a gelled product of an aqueous slurry containing coal ash / lime and gypsum.

(F) In JP-A-62-256747, a method in which limestone, Portland cement, and slaked lime are added in a specific amount to coal ash and fired.

Each of these conventional techniques is a method in which coal ash is added with an inorganic chemical such as coal, cement, gypsum, slaked lime, caustic soda, sodium silicate or the like, and the mixture is cured or fired.

(Problems to be Solved by the Invention) In the above-mentioned conventional proposals, the amount of the additive to the coal ash is relatively large, and no one using 90% or more of the coal ash is found,
There is a problem that the effective utilization rate of coal ash is low, and the additive is lime, cement, gypsum, etc., and if a large amount of these is used, the cost will increase, and the binding agent is limited. There is a problem that inconvenience may occur to human hands, and in the curing means, there is a problem that the curing method takes too much time until commercialization and a wide space for curing is required. Because of the high temperature of 1200 to 1300 ℃, there are many problems such as bulky fuel cost and cost increase, and these problems have been desired to be solved.

The present invention solves the above-mentioned conventional problems, most of the material is coal ash, the range of selection of the binder is wide, the firing temperature can be commercialized at a relatively low temperature, the product has a bulk specific gravity. It is an object of the present invention to provide a method for producing a porous fired and hardened body containing coal ash as a main raw material, which has a small size, and has water absorption and water permeability.

(Means for Solving the Problems) The present invention for achieving the above object is a mixture 10 of coal ash and sand or clay in an amount of 10% or less by weight of the coal ash.
0 parts by weight to 1 to 5 parts by weight of a natural or artificial binder,
After adding 15 to 30 parts by weight of water and kneading at room temperature and normal pressure, it is filled into a mold or molded into a predetermined shape by press molding, and then the molded product is placed in a firing furnace and allowed to reach a maximum of 8 to 24 hours. A method for producing a porous fired and hardened body containing coal ash as a main raw material, which is fired under firing conditions that reach a firing temperature of 1050 to 1150 ° C.

The above-mentioned natural binders are strong wheat flour, potato starch, soluble starch, tragacanth gum, arabic gum and the like, and artificial binders are trade names Pozzolis No70 and Sunex P, which are mainly composed of polyvinyl alcohol and sodium ligninsulfonate.
-200, sun extract P-201, sun extract P-252, sun extract SCP and the like.

(Function) By adding a small amount of sand or clay to the coal ash (weight ratio of 10% or less), the sand or clay functions as an aggregate, and a mixture of a binder and water is kneaded. It is possible to increase the strength of the fired product as well as the shape of the molded product that is put into the mold or pressed to be molded.

In addition, when the molded product is placed in a firing furnace and fired in advance according to a temperature rising program planned according to the characteristics of the coal ash and the added sand or soil, the unburned carbon and caking contained in the molded product When the agent is completely burned, the coal ash is aggregated to change the particle size composition, and due to this combustion and the particle size composition change, a large number of pores are created inside the molded product, making it a lightweight, water-absorbing and water-permeable porous material. A quality calcined product is obtained.

(Examples) Examples of the present invention will be described below.

Fig. 1 is a block diagram showing the steps of the present invention. 90% of coal ash
It is shown that a binder and water are added to a mixture of the above and sand or 10% or less of clay to obtain a porous fired cured body through the steps of kneading, molding and firing. For example:

Example 1 100 parts by weight of a mixture of 95 parts by weight of coal ash and 5 parts by weight of soil for roof tile material, and 2 parts by weight of a binder (commercial name Pozzolith No70) containing sodium ligninsulfonate as a main component. ,water
Add 20 parts by weight and knead to obtain the clay.
1W × 61H × 212Lmm) (filling amount about 2.44kg), press molding (about 100kg / cm ² ) with a hydraulic press, take it out from the mold, and air dry at 100 ° C and air dry. Thus, a molded product having a predetermined shape and a strength capable of being transferred to the firing step was obtained.

Then, this molded product is propane gas kiln (internal volume 0.25 m ³ )
Then, according to a preset temperature rising program shown in FIG. 2, firing was performed under the firing conditions that the maximum temperature reached 1100 ° C. for 14 hours to obtain a porous fired cured body. As a result of measuring the physical properties of the six porous calcinated cured products, the results are shown in Appendix 1. Judging from this physical property value,
It was recognized as having sufficient practicality.

Example 2 This Example 2 was carried out to find out whether or not commercialization was possible by using 11 kinds of natural and artificial binders, and 97 parts by weight of coal ash and 3 parts by weight of soil for roof tile raw material. To 100 parts by weight of the mixture consisting of 10 parts by weight, a binder of the type and amount shown in Appendix 2 and water to the extent that a clay having an appropriate viscosity is obtained are added, and each is mixed with a mortar mixer (volume 5 l). Each binder is kneaded for 1 hour to obtain 11 kinds of clay, which are filled into a wooden form (4W x 4H x 16Lcm) by the manual packing method (filling amount about 500g). In this state, the mixture was left overnight to reduce the water content naturally, and then the mold was removed and the molded product was taken out.
This molded product is naturally dried and air-dried by heating at around 100 ° C, and has the required shape and strength to move to the firing process.
Molded articles with 11 different binders were obtained.

Next, this molded product was placed in an electric furnace (internal volume: 30W x 30H x 60Lc
m) The maximum temperature was set in advance for a total of 16 hours divided into 2 days in accordance with the preset heating program shown in Fig. 3.
By firing under the firing conditions reaching 1130 ° C, 11 kinds of porous fired cured bodies were obtained. The results of measuring the physical properties of each of the 11 types of porous calcination cured products are shown in Appendix Table 2.

It was recognized that these physical properties have practicality because they have a large difference in mechanical strength depending on the kind of the binder, but they are suitable for applications where each property can be utilized.

(Effect of the invention) According to the method for producing a porous calcination effect body using coal ash as a main raw material according to the present invention described above, the amount of the additive is small, and the coal ash occupies 90% or more of the raw material. Therefore, the effective utilization rate of coal ash is high, and since the additive is sand or clay, it is cheaper than conventional cement or gypsum,
Moreover, by adding a small amount of this sand or clay, it can function as an aggregate and prevent the deformation of the mold during molding and the occurrence of cracks during drying, and it is possible to reduce the strain due to firing, and the binder is There are advantages that both natural and artificial can be used, and that the firing temperature is lower than that of the conventional method, so that the firing cost such as fuel cost can be reduced.

In addition, since the product is porous and lightweight, and has water absorbency and water permeability, it is possible to obtain a porous calcination cured product which can be widely used for civil engineering, blocks for landscaping, construction boards and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a process of the present invention, and FIGS. 2 and 3 are diagrams showing a temperature rising program in firing in a line graph.

Claims (1)

[Claims] 1. A binder 1 to 5 is added to 100 parts by weight of a mixture of coal ash and sand or clay in an amount of not more than 10% by weight of the coal ash.
After adding 15 parts by weight of water and 15 to 30 parts by weight of water and kneading the mixture at room temperature and normal pressure, it is filled into a mold or molded into a predetermined shape by press molding, and the molded product is put into a firing furnace for 8 to 24 hours. A method for producing a porous calcination cured body containing coal ash as a main raw material, characterized in that calcination is performed under calcination conditions such that the maximum calcination temperature reaches 1050 to 1150 ° C.