JPH07112174A - Production of artificial sand - Google Patents

Abstract

PURPOSE:To provide a technique for forming resources at a low cost to stably utilize a large amt. of sewer sludge incineration ashes by adding water to the sewer sludge incineration ashes, mixing and kneading these ashes to form a mixture, pelletizing this mixture, calcining the pellets after drying and crushing the calcined pellets after cooling, thereby producing artificial sand. CONSTITUTION:Only water is added at a prescribed mixing ratio to the sewer sludge incineration ashes and after the ashes are sufficiently kneaded by a kneading machine 1, the mixture is pelletized or molded to a plate form of prescribed sizes by a molding machine 2. The moldings are dried by a dry calcination furnace 3 and are then calcined at a prescribed temp. (m. p. or below). The calcined pellets are allowed to stand for natural cooling or allowed to cool down to the prescribed temp., and thereafter, the pellets are cooled with water and are crushed by a crushing machine 4. The crushed ashes are classified by a classifying machine 5 and are subjected to grain size adjustment according to applications thereof by which the artificial sand is produced. Consequently, the technique for using resources at the low cost to stably utilize a large amt. of the sewer sludge incineration ashes is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing artificial sand from sewage sludge incineration ash generated in sewage sludge treatment equipment.

[0002]

2. Description of the Related Art Conventionally, sewage sludge incineration ash has been humidified and then landfilled, or it has been mixed with cement, lime or the like, granulated and solidified, and then landfilled. In addition, recently, molten slabs have been used for landfill disposal, or pressure-molded to make fired bricks.

[0003]

The above-mentioned prior art has the following problems. When landfilling, it is difficult to secure landfill sites, and there are problems such as protection of the natural environment and soaring sludge disposal costs. In addition, when manufacturing fired bricks and the like, measures such as treatment cost, quality and sales channels are insufficient.

It is an object of the present invention to provide a resource-saving technique for stably utilizing a large amount of sewage sludge incineration ash at a low cost.

[0005]

[Means for Solving the Problems] To a sewage sludge incineration ash, only water is added at a predetermined mixing ratio, and after sufficiently kneading, granulated or plate-shaped to a predetermined size and dried, and then a predetermined temperature (below the melting point) )
Bake at. Next, the calcined product is naturally cooled or naturally cooled to a predetermined temperature, and then water cooled, and crushed and classified to adjust the particle size according to the purpose of use to produce artificial sand. In addition, the fine material is returned to the incineration ash side and used again as a raw material.

[0006]

The sewage sludge incineration ash incinerated in the fluidized bed furnace has a very fine particle size of several tens of microns or less, regardless of the type of dehydrated cake (polymer type or lime type). And
By adding an appropriate amount of water to this ash and sufficiently kneading, it becomes possible to perform molding such as granulation. Therefore, it is formed into a granular or plate-like material of a predetermined size, pre-dried, and then 100
Baking is carried out for 10 to 30 minutes at a baking temperature of 0 to 1200 ° C. Then, it is naturally cooled or water-cooled at 500 ° C or lower.
And by crushing and classifying this and adjusting the particle size,
It is possible to manufacture artificial sand having physical properties comparable to natural sand. This is due to the fact that the material was uniformly heated during firing to achieve uniform firing inside the material. This is a pretreatment of the material molding conditions (shape, dimensions, water content, etc.).
Is heavily involved.

That is, if the size, shape, water content and heating conditions before firing are not appropriate, cracks may occur in the firing process or uniform firing may not be possible, resulting in different firing degrees inside and outside the fired product. Becomes

[0008]

EXAMPLE A block flow diagram of the method for producing artificial sand from sewage sludge incineration ash according to the present invention is shown in FIG. As shown in the figure, the incinerated ash is quantitatively supplied from a hopper or the like to the kneading machine 1, where it is mixed and kneaded with a predetermined amount (15 to 30% by weight) of water, and the molding machine of the next step. Sent to 2. The amount of water added for granulation is closely related to the particle size of incinerated ash, and the finer the particles, the smaller the amount of water added to the shape-retaining power,
For fluidized bed incineration ash of sewage sludge, the appropriate amount of water added is 15
Was 30%.

Next, in the molding machine 2, it is formed into a granular shape having a maximum diameter of 10 mmφ or a plate shape having a thickness of 10 mm or less, and the plate-like material is crushed to a size of about several tens of mm and introduced into the drying and firing furnace 3. Here, the sintering reaction proceeds after the drying of the added water, and the firing is completed at a predetermined temperature for 10 to 30 minutes.
This predetermined temperature varies depending on the component composition of the object and is in the range of 1000 to 1200 ° C., which is slightly lower than the melting point.

Further, the shrinkage rate of the baked product, that is, the porosity is large or small.
Influences the heating rate, residual water content during firing, and firing temperature.
On the other hand, the product strength is large at the processing temperature as shown in Fig.2.
To be affected. In the figure, region A is in the state of sintering at the stage of solid phase sintering.
Is still insufficient, and a slight liquid phase is generated inside the particles in the B region.
Then, sintering proceeds a little, and in the C region, a liquid phase is generated.
More, complete liquid phase sintering, particles are firmly fixed to each other, D
In the region, the liquid phase further increases, particles begin to coalesce, and
In the area, degassing from inside (for example, CO₂, SO ₂other)
Bubbling and foaming due to product strength here
The degree will be extremely low. Moreover, the temperature is further raised.
And the whole becomes molten slag, and by gradually cooling and crystallization
Strength is improved. And as the optimum sintering temperature in the figure,
Area C is selected. However, this C region also depends on the material composition.
However, in the case of sewage sludge incineration ash, it is generally very narrow at several tens of degrees Celsius.
It is within the range. Therefore, both inside and outside of the material are uniform
In order to achieve a sintered state, in addition to controlling the firing furnace temperature,
Keep the temperature distribution in the object to be processed within the temperature range of the above C range.
Is important.

Therefore, the inventors conducted various basic tests, heat transfer analysis, etc., and set the maximum thickness or diameter of the pre-firing target material (water-added granulated material) to 10 mmφ or less, thereby It was possible to obtain a uniform calcined product by controlling the temperature distribution in the article to be treated within the temperature range of the C range. Next, the calcined solidified product is allowed to cool naturally (air cooling) or 5
After being naturally cooled to 00 ° C., it is cooled with water, conveyed to a crusher 4, where it is crushed to a particle size required as a product and classified by a classifier 5. In addition, in this classification operation, the large-sized product is crushed again, and the fine product is returned to the process inlet side and is again fired together with the incinerated ash.

The physical properties of the artificial sand produced by this system are shown in Table 1, and the applicability evaluation results of this artificial sand as fluidized sand for a fluidized bed incinerator are shown in Table 2. From these, it was found that the artificial sand produced by adding water to sewage sludge incineration ash, granulating and firing it can be sufficiently used as a substitute for natural sand that has been conventionally used as fluidized sand.

The following Table 1 shows the physical properties of the artificial sand thus obtained, and Table 2 shows an example of the results of the applicability evaluation test as a fluid material for an incinerator.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

Industrial Applicability The method for producing artificial sand according to the present invention comprises adding water to sewage sludge incineration ash, mixing and kneading to make a mixture, granulating the mixture, drying and firing the mixture. The following effects can be obtained by producing a product, cooling the fired product, and then crushing the product to produce artificial sand.

Conventionally, artificial fluidized sand as a substitute for natural fluidized sand can be produced from sewage sludge incineration ash, which has hitherto been mainly used for landfill disposal. In addition, it can be reused in the sewage treatment plant, which is the source of incineration ash, and can contribute to reduction of the amount of landfill incineration ash (prolonging the life of the landfill) and resource saving. Furthermore, by using this artificial sand as an aggregate for fired bricks, etc., a fired brick manufacturing system with high dimensional accuracy can be provided, and it can be used as a construction material for wide-area utilization.

As described above, it is possible to provide a resource recycling type processing method from the conventional transient type processing method.

[Brief description of drawings]

FIG. 1 is a block flow diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between processing temperature and product strength in an example of the present invention.

[Explanation of symbols]

 1 Kneader 2 Molding machine 3 Drying firing furnace 4 Crusher 5 Classifier

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 18/10 Z (72) Inventor Satoshi Okuno 12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries Shares Company Yokohama Works (72) Inventor Shuichi Jida 12-71 Goryocho, Higashimatsuyama City, Saitama Prefecture (72) Inventor Toshio Tsuru 5-14-46, Oshidate Town, Fuchu City, Tokyo

Claims (1)

[Claims] 1. Water is added to sewage sludge incineration ash, mixed and kneaded to form a mixture, and the mixture is granulated, dried, and fired to produce a fired product, which is then cooled. A method for producing artificial sand, which comprises crushing to produce artificial sand.