JPH02169082A - Method for calcining molded body of ash obtained by incinerating sludge - Google Patents

Abstract

PURPOSE:To enhance the compressive strength and bending strength of a molded body of ash obtd. by incinerating sludge and to reduce the rate of water absorption by rapidly raising the temp. of a furnace until the surface temp. of the molded body reaches a prescribed temp. below the softening point of the ash and by slowly raising the temp. of the furnace to the softening point of the ash. CONSTITUTION:The temp. of a furnace is rapidly raised until the surface temp. of a molded body of ash obtd. by incinerating sludge reaches a prescribed temp. below about 1,000 deg.C as the softening point of the ash, e.g. about 900 deg.C. The temp. of the furnace is then slowly raised, e.g. at about <=200 deg.C/hr rate until the surface temp. of the molded body exceeds about 1,000 deg.C as the softening point of the ash. Since oxygen is fed even to the inside of the molded body during calcining, the compressive strength and bending strength of the molded body are enhanced and the rate of water absorption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for firing a sludge incineration ash compact.

(Prior Art) There are various methods for treating sewage sludge, etc.
Lime-based or polymer-based sewage sludge incineration ash under surface pressure of 0.3
~2. Pressure molded with OL/c♂, then 950~12
By firing at a temperature of 00'c, the volume of incinerated ash per medium weight ffi is reduced to 1/4 to 1/6,
We proposed a treatment method that is easy to handle and has excellent disposal properties.

Furthermore, since this fired product complies with standards for construction materials, it can be effectively used as construction materials such as tiles and bricks.

By the way, conventionally, as shown in FIG. 3, the molded body of incinerated ash has been prepared by controlling the furnace temperature to 950 to 950, which is the firing temperature.
The temperature is rapidly increased linearly to 1200° C., and then the firing temperature is maintained at the above firing temperature.

However, the surface of the obtained fired body is brick-colored and densely fired, but the interior is white and porous, and the compressive strength, bending strength, water absorption rate, and The results of the freeze-thaw test showed the following values,
In particular, it was not sufficient as a construction material in cold regions.

As a result of various studies on the above points, the present inventors found that in the conventional firing method, the surface of the molded body rises almost in line with the temperature rise curve of the furnace temperature, but the internal temperature of the molded body increases as shown in Figure 4. As shown by the broken line, the temperature rises much later than the surface temperature. In other words, it has been found that only the surface portion of the molded body becomes softened (molten state) first, and as a result, sufficient oxygen is not supplied to the inside of the molded body, creating an oxygen-free firing region.

The present invention has been made based on this knowledge.

(Means for Solving the Problems) In the present invention, when firing a molded body of sludge calcined ash, the surface temperature of the molded body is rapidly raised to a predetermined temperature below the softening point of the calcined ash, and then the This is a method for firing a sludge incineration ash molded body, which is characterized by slowly increasing the temperature until it passes a softening point.

(Example) Next, an example of the present invention will be described with reference to the drawings.

Sewage sludge incineration ash generally has two types: lime-based and polymer-based. The former contains 20 to 50% CaO, 10 to 30% Si,
It consists of Al1O35~15% pond, the latter is CaO3~1
O%, Siot 20-45%, AItos lo
~20% consists of others.

Then, in the burning process, 1) the ash is pressure-molded into a predetermined shape using a powder-forming press to obtain a compact.

This molded body is fired by setting the internal temperature curve of the firing furnace as shown in FIG.

That is, the figure shows the case where a molded body made of polymer-based incinerated ash is fired, and the temperature is about 1000°C, which is the softening point of the incinerated ash.
Furnace up to a predetermined temperature, e.g., about 900°C; 1.
Rapidly raise the temperature of A. After that, the softening point is about +000
℃ (preferably 200° C./h or less), and then the temperature is raised to the calcination temperature at the same temperature increase rate for firing. In addition, as shown in FIG. 1(b), after passing the softening point, the temperature may be rapidly raised by 1q degrees to the firing temperature, and then held and fired.

When the temperature is raised in this way, the temperature reaches 900° as shown in Figure 2.
Since the temperature rise rate is relatively slow from C to 1000°C, the internal hot water temperature of the molded body becomes the same as the surface l temperature while the temperature of the molded body surface reaches the softening point.

Therefore, the entire molded body, both the surface and the inside, passes through the softening point and reaches 1100° C. at approximately the same temperature, during which time it is fired.

In other words, in this example, the softening point of the incinerated ash is about 100
Oxygen is sufficiently supplied to the inside of the molded body through the gaps between the powders until the temperature reaches 0°C (in Figure 4, the supply of oxygen stops when the temperature inside the molded body reaches about 800°C), and an anoxic sintering zone is formed. Therefore, the molded body is completely fired to the inside.

A molded article of polymeric incineration ash (a cylindrical block with a diameter of 70 x 60 i) was fired using the method of the present invention and the conventional method, and the following results were obtained.

(Left below) In the above example, a high-density j'-based incineration ash was used, but almost the same results were obtained with a lime-based incineration ash.
'It's J.

However, in the case of lime-based, the firing temperature is approximately 1300℃,
The softening point is about 1100°C.

(Effects of the Invention) As is clear from the above explanation, the present invention rapidly raises the surface temperature of the compact until it reaches a predetermined temperature below the softening point of the fired ash, and then Since the temperature is raised slowly, oxygen is supplied to the inside of the molded body during firing, thereby improving compressive strength and bending strength, and reducing water absorption.

[Brief explanation of the drawing]

Figure 1 is the furnace temperature curve of the method of the present invention, Figure 2 is a partially enlarged curve of Figure 1, Figure 3 is the furnace temperature curve of the conventional method, and Figure 4 is the furnace temperature curve of the method of the present invention.
The figure is a partially enlarged curve of FIG. Patent applicant Chugai Roko Kogyo Co., Ltd. Agent
Patent attorney Aohaku Haka1 figure Hr figure 3 Hr 21m

Claims (1)

[Claims] (1) When firing a molded body of sludge and calcined ash, the surface temperature of the molded body is rapidly raised to a predetermined temperature below the softening point of the calcined ash, and then gradually raised until it passes the softening point. A method for firing a sludge incineration ash compact characterized by heating it.