JP2620742B2 - Method for producing sintered soil from dewatered sludge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for reusing sludge generated from a water purification plant, sludge deposited in rivers, lakes and marshes, etc. More specifically, the present invention relates to dewatered sludge obtained by dewatering the above sludge. The present invention relates to a method for producing a sintered soil as a raw material.

[0002]

2. Description of the Related Art Sludge settled in a sedimentation basin at a water purification plant has been subjected to a dehydration treatment and most of the sludge has been landfilled. In addition, sludge (sludge) accumulated in rivers and lakes is collected by mechanical means such as suction by a pump or excavation by a shovel, and is mixed with cement or a coagulant to be solidified and then landfilled. It had been.
As another disposal method of sludge, there is a method of mixing fertilizer into dewatered sludge and using it as field soil.

[0003]

However, the amount of sludge generated from the water treatment plant tends to increase, and it is becoming difficult to secure landfill sites every year. Can not expect. Also, when fertilizer is mixed with dewatered sludge and used as field soil, if harmful substances such as soluble aluminum and arsenic are contained in the sludge, it may become a source of pollution. There were limitations and only very small amounts were used in practice.

The present invention has been made in view of the above-mentioned circumstances, and has been devised in consideration of the above-mentioned circumstances, and has a product value of dewatered sludge obtained by dewatering sludge generated from a water purification plant and sludge deposited in rivers, lakes and marshes. It is an object of the present invention to provide a method for producing sintered soil used for high horticultural soil and the like, and to effectively reuse sludge.

[0005]

In order to achieve the above object, the method for producing a sintered soil using dewatered sludge as a raw material according to the present invention deposits sludge generated from a water purification plant, rivers, lakes and marshes. A method for producing a sintered soil used for horticultural soil, etc., using dewatered sludge obtained by dewatering dewatered sludge as a raw material, wherein a crushing step of crushing the dewatered sludge to a particle size of about 5 mm or less and stirring A granulating step of granulating into pellets by a granulator, a drying step of drying the pellets to a water content of about 10% or less, and a firing step of firing the dried pellets at a firing temperature of about 800 ° C. to 1100 ° C. It consists of

In the above-mentioned crushing step, the degree of crushing of the dewatered sludge is about 5 mm or less, more preferably about 4 mm or less. Granulation cannot be performed efficiently.

[0007] In the granulation step, a stirring granulator is used, which promotes the agglomeration of the pellets.

In the drying step, the pellets are preferably dried for a relatively long time by a hot-air dryer using a low-temperature (for example, 150 ° C. to 200 ° C.) hot gas as a heat source. An intermolecular force or the like acts on the pellet to form an aggregated structure having an excellent bonding force, and can prevent explosion or cracking of the pellet in the next firing step. If the degree of drying of the pellets exceeds 10%, the hardness of the product obtained by sintering is not sufficient, and the pellets are likely to lose their shape. % Is preferred.

The dried pellets are fired at a required firing temperature in a firing step, whereby the amount of soluble aluminum and the like contained in the raw material is reduced to a target value or less required for a product, and A product excellent in water absorption and hardness can be obtained. Preferred firing temperature is 8
00 ° C to 1100 ° C, more preferably 900 ° C to 950
If the sintering temperature is within the range of ° C. and the sintering temperature is out of this range, the amount of soluble aluminum and the like required for the product cannot be sufficiently reduced.

In this way, a pollution-free product excellent in water absorption, water permeability and hardness, and in which the leaching amount of harmful substances such as soluble aluminum is reduced to a target value or less can be obtained.

[0011]

An embodiment of the present invention will be described below.

In this embodiment, a palm-sized filter cake (dewatered sludge) obtained by dewatering sludge settled in a sedimentation basin to a water content of about 65% by a dewatering machine installed in a water purification plant was used as a raw material. . The filter cake does not contain any additives such as a binder. Each step until a product is obtained is as shown in FIG. 1 and includes a crushing step, a granulating step, a drying step, a firing step, and a sieving step.

(A) Crushing Step In this step, the palm-sized filter cake was crushed using a crusher to a particle size of 4 mm to 5 mm or less.

(B) Granulation Step In the granulation step, the crushed filter cake is crushed using an agitation granulator to form the aggregate structure required for the plant soil, and the average particle size is 8 mm. Granulated into pellets of about 15 mm.

(C) Drying Step In the drying step, a hot gas of 150 ° C. to 200 ° C. is used as a heat source in order to dry the pellets at a low temperature for a relatively long time so as to have a aggregated structure having an excellent bonding force. The pellets are charged into a packed bed dryer using
%.

(D) Firing Step In the firing step, the dried pellets were fired at a firing temperature of 900 ° C. to 1000 ° C. using a rotary kiln.

Here, FIGS. 2 to 4 show experimental data obtained by examining the relationship between the temperature in the kiln (firing temperature) and the water absorption, hardness, and the amount of soluble aluminum eluted from the fired pellets. 2 and 3 also show experimental data obtained by performing the preceding drying step in the same rotary kiln as in the present step, and conducting the other conditions under the same conditions.

FIG. 2 shows the relationship between the water absorption of the fired pellets and the temperature inside the kiln. As is clear from FIG. 2, the higher the temperature inside the kiln, the lower the water absorption of the fired pellets. I have.

FIG. 3 shows the relationship between the hardness of the fired pellets and the temperature in the kiln. As is apparent from FIG. 3, the higher the temperature in the kiln, the harder the fired pellets.

FIG. 4 shows the relationship between the amount of soluble aluminum eluted from the fired pellets and the temperature in the kiln.
(Note that, as a sample for the elution analysis, a fired pellet finely pulverized to a particle size of 0.5 mm or less was used as a sample, and pH 4, N sodium acetate was used as a solvent.) As is clear from FIG. The elution amount of soluble aluminum tends to decrease as the internal temperature increases.

As is clear from FIGS. 2 to 4, if the firing temperature is maintained at about 950 ° C., it is possible to obtain a product having a low soluble aluminum elution amount and excellent in water absorption and hardness.

The exhaust gas used in the drying step and the baking step is discharged out of the system through a large-scale high-performance dust collector, thereby making the plant pollution-free.

(E) Sieving Step The pellets fired in the firing step are cooled, then screened, and those having an appropriate particle size are selected as products. On the other hand, the oversized and undersized ones are pulverized to an appropriate particle size and then returned to the crushing step. Thereby, the product yield can be improved.

[0024]

The method for producing sintered soil used for horticultural soil and the like using the dewatered sludge as a raw material according to the present invention comprises the steps of:
mm, a granulating step of granulating the crushed material into aggregated pellets by a stirring granulator, a drying step of drying the pellets to a moisture content of about 10% or less, and a drying step. Since the sintering step comprises sintering the pellets at a sintering temperature of about 800 ° C. to 1100 ° C., the water absorption and the water permeability are excellent, the surface hardness is high, and the elution amount of harmful substances such as soluble aluminum is reduced to a target value or less. , High quality products with no pollution. Therefore, according to the present invention,
Effective reuse of the sludge generated at the water purification plant can be achieved, which can contribute to a reduction in the amount of sludge disposal.

Of course, the sintered soil produced by the present invention may be used for applications other than horticultural soil, for example, construction materials such as aggregates, soil improvement materials, and the like.

[Brief description of the drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

FIG. 2 is a view showing a relationship between a water absorption rate of a fired pellet and a firing temperature.

FIG. 3 is a diagram showing a relationship between hardness of a fired pellet and a firing temperature.

FIG. 4 is a graph showing the relationship between the amount of soluble aluminum eluted from a fired pellet and the firing temperature.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jinshiro Fujita 5-3-28 Nishikujo, Konohana-ku, Osaka-shi Inside Tachibana Shipbuilding Co., Ltd. (72) Osamu Izuno 5-3-1 Nishikujo, Konohana-ku, Osaka-shi No. 28 Nippon Shipbuilding Co., Ltd. (72) Inventor Hiroyoshi Yamazaki 5-28 Nishikujo, Konohana-ku, Osaka-shi Nippon Shipbuilding Co., Ltd. (72) Inventor Hiroshi Okada 5-6-Kitaurawa, Urawa-shi, Saitama No. 5 Saitama Prefecture Environmental Conservation Public Corporation (56) References JP-A-1-199524 (JP, A) JP-A-62-275618 (JP, A) JP-A-61-74694 (JP, A) Kaikai 53-38527 (JP, A)

Claims (1)

(57) [Claims] 1. A method for producing a sintered soil which is used as a horticultural soil, using dewatered sludge obtained by dewatering sludge generated from a water purification plant or sludge deposited in rivers, lakes and marshes as a raw material,
A crushing step of crushing the dehydrated sludge to a particle size of about 5 mm or less, a granulating step of granulating the crushed material into aggregated pellets by a stirring granulator, and a drying step of drying the pellets to a water content of about 10% or less. And the dried pellets are fired at a firing temperature of about 800.
A method for producing a sintered soil using dehydrated sludge as a raw material, comprising a firing step of firing at a temperature of from 1 ° C to 1100 ° C.