JPH05294692A - Production of artificial lightweight aggregate from construction sludge - Google Patents

Abstract

PURPOSE:To produce the artificial aggregate by utilizing construction sludge which treatment becomes difficult. CONSTITUTION:The production of an artificial aggregate comprising coating the surfaces of granule nuclei produced from ground paper or its mixture with construction sludge with the construction sludge or its mixture with the ground paper and subsequently firing the produced two layer granules in a firing oven separated from the atmosphere, while controlling the concentration of oxygen in response to the amount of a self-burning material contained in the granules. The granule nuclei may be mixed with coke powder or fine coal to improve their self-burning property, and further the surfaces of the two layer granules may be coated with alumina powder or silica powder for preventing their fusing.

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 an artificial lightweight aggregate applied to an aggregate of lightweight concrete from a construction sludge as a raw material in order to reuse the construction sludge discharged from a construction site.

[0002]

2. Description of the Related Art (1) Waste bentonite mud, (2) waste mud associated with the reverse construction method, and (3) mud excavated soil with high water content and fine particles are the main sludge discharged from construction sites. , (4) Settled sludge generated by sedimentation and separation of spring water discharged during construction, (5) Groundwater, earth and sand and cement that overflow from the top of the auger when a highly water-blocking wall is constructed by the soil cement method. Examples include mixed sludge of milk.

There are a sun drying method and a mechanical dehydration method as a method for treating muddy water. In the sun drying method, waste muddy water is transported from the site to an area that combines vacuum dehydration and closed dump trucks for both dehydration and drying and final disposal. As the opposition from the residents has become stronger, this sun drying method has almost never been implemented.

A vacuum filter, a pressure filter, a gravity filter and the like are used for dehydration and concentration of sludge in the mechanical dehydration method. The dehydrated cake, which is the residue after dehydration, is carried out to the landfill site as it is, or is mixed with cement, quick lime, water-absorbent resin, etc., and is carried out to the landfill site after solidification treatment.

[0005]

When the amount of muddy water discharged at the construction site is small, the muddy water is transported to a centralized treatment facility by a vacuum truck or a closed dump truck for dehydration drying / solidification treatment. When a large amount of muddy water is discharged, a muddy water treatment facility is installed at the site base to perform mechanical dewatering or stop the trailer equipped with a dewatering machine for processing. Most of the dehydrated cakes whose moisture content has been reduced in this way are discarded at landfill sites.

However, in a metropolitan area where a large amount of muddy water is discharged,
The cost of landfill disposal is becoming difficult, and the transportation distance from the discharge site to the centralized treatment facility or the final landfill is becoming longer. Furthermore, some of the sludge that has become landfillable is used as landfill material, embankment material, etc. for land preparation, but its economic value is similar to that of natural earth and sand, so it cannot always be said that it is actively utilized. ..

In view of such a situation, the present invention has been made by paying attention to the positive regeneration of construction sludge as a resource. The construction sludge solid matter after dehydration and drying is granulated and sintered. By doing so, it is intended to provide a method for producing an artificial lightweight aggregate from construction sludge that can be recycled as an artificial lightweight aggregate.

[0008]

The method for producing an artificial lightweight aggregate from construction sludge of the present invention takes the following means. (1) Pulverized paper or pulverized paper and construction sludge This mixture is used as a granulation nucleus, and the surface of the granulation nucleus is coated with construction sludge or a mixture of construction sludge and pulverized paper to form a two-layer granulation product. It is characterized in that the product is fired. (2) The invention of (1) above is characterized in that coke powder or pulverized coal is added to the granulation nucleus. (3) In the invention of (1) or (2), the surface of the two-layer granulated product is coated with alumina powder or silica powder. (4) In the invention of any one of (1), (2), and (3) above, a two-layer granulated product is laminated on a grate of a firing furnace isolated from the atmosphere, and self-combustion contained in the granulated product. It is characterized in that the sintering is performed while controlling the oxygen concentration according to the amount of the material.

[0009]

[Operation] Since solid matter of construction sludge usually does not contain combustibles, when granulating and sintering with only solid matter, external heat supply is required to reach the sintering temperature. However, it is not practical because the specific gravity of the sinter is only comparable to that of natural aggregate.

Therefore, in the present invention (1), in order to reduce the specific gravity of the sintered product and minimize the amount of heat supplied from the outside, crushed paper which is a self-burning material is used. A method was adopted in which a mixture of construction sludge was used as a granulation nucleus, and the surface layer of the granulation nucleus was coated with a construction sludge or a mixture of construction sludge and crushed paper as a pellet layer to form a two-layer granulation product, which was then sintered. ..

Further, in the present invention (2), the above-mentioned present invention (1)
In the above, coke powder or pulverized coal was further added to the granulation core.

The crushed paper, which is a self-burning substance, is crushed into smaller pieces (usually 5 mm or less) than the granulation core by a crusher or the like, and can be obtained at a low cost such as cardboard, newspaper, magazines, other used paper or recycled pulp. Any kind of paper can be used. On the other hand, coke dust or pulverized coal is crushed by a crusher or the like (usually 100
μm or less).

In this way, the self-burning substance is burned by firing the granulated substance which is composed of the construction sludge and the crushed paper, and further contains the self-burning substance to which coke powder or pulverized coal is added if necessary. Then, self-combustion is performed to obtain a granular sintered product.

The sintering temperature is the temperature at which the maximum expansion rate is judged from the high temperature characteristic curve of the construction sludge shown in FIG. 2 (in this case,
A temperature in the range of 1150 to 1200 ° C near 1200 ° C) is appropriate. The structure of the sintered product sintered at this temperature is
The self-burning substance in the granulation nucleus has a large cavity due to the disappearance of firing,
In addition, innumerable minute cavities are formed in the pellet layer around the cavities due to the foaming phenomenon, and the surface layer thereof vitrifies. When the sintering temperature exceeds 1170 ° C., the sinters are fused to each other. Therefore, as in the present invention (3), as a fusion preventing material for the surface layer of the granules, the alumina powder is formed on the surface of the two-layer granules. Alternatively, by coating with silica powder, fusion of the sintered products can be prevented. However, when the sintering temperature is 1250 ° C. or higher, the sintered product melts and loses its shape. Therefore, in the present invention, it is preferable to perform the sintering at 1250 ° C. or lower.

In granulating the two-layer granulated product as raw pellets in the present invention, the particle size ratio of granulated nucleus / granulated product The self-combustible material that constitutes the granulation nucleus may be pulverized paper alone or a mixture of pulverized paper and coke powder or pulverized coal. That is, when the particle size ratio of the granulated core / granulated product is large (when the particle size of the granulated product is small), the granulated core has a small calorific value, and when it is small (the particle size of the granulated product When the value is large), the crushed paper contains a mixture of coke powder or pulverized coal, which has a large calorific value, as a granulation nucleus.

On the other hand, in the case of a two-layer granulated product in which the granulation nucleus surface layer is coated with construction sludge containing pulverized paper as a pellet layer, about 5% by weight of pulverized paper is added to the pellet layer on a dry basis for self-combustion binding. Need to let.

In the sintered products of the present invention (1) and (2), the absolute dry specific gravity can be adjusted by changing the particle size ratio of the granulation nucleus / granulated product. Further, since the surface layer of the sintered product is vitrified by high temperature sintering, it is possible to manufacture a product having a remarkably small water absorption rate. As a result, this sintered product can sufficiently satisfy the physical property values as an artificial lightweight aggregate. Further, in the present invention (3), the surface of the two-layer granulated product is further coated with the alumina powder or the silica powder, so that the sintering temperature range is widened and the product yield can be improved.

Further, in the present invention (4), the two-layer granulated product is laminated on the grate of the firing furnace which is isolated from the atmosphere, and the oxygen concentration is adjusted according to the amount of the self-combustion product contained in the granulated product. By controlling, the combustion is controlled according to the amount of self-burning substances, and it is possible to obtain an artificial lightweight aggregate having excellent physical properties.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Reference numerals 1, 2 and 17 are hoppers for accommodating finely pulverized paper, construction sludge (dehydrated and dried product), and coke powder, respectively, from the hoppers 1 and 2 to finely pulverized paper, construction sludge, and if necessary, hopper 1
Coke powder is supplied from 7 to the kneading machine 3. Same kneader 3
Then, water 3'is sprinkled to knead finely pulverized paper, construction sludge and the like, and the granulation nuclei obtained by granulating this with a pan-type granulator 4 are transported by a belt conveyor 5 and pelletized. It is put into a pan-type granulator 6 for coating the layers.

On the other hand, construction sludge is supplied from the hopper 2 ', and finely pulverized paper is supplied from the hopper 1'to the kneading machine 16, if necessary.
The kneaded material which is kneaded by sprinkling water 16 ′ in the same kneading machine 16 is coated on the surface of the granulation nucleus which is put into the pan type granulator 6 and transported by the belt conveyor 5. Thus, a two-layer granulated product obtained by two-stage granulation is obtained.

Further, if necessary, the two-layer granulated product is
It is put into a bun-type granulator (not shown), the surface layer of the same two-layer granulated product is coated with alumina powder or silica powder, and it is stored in the hopper 8 for charging raw pellets.

Reference numeral 8'denotes a hopper for placing bedding on the floor which contains the baked products (baked pellets). The hopper 8'and the hopper 8 for charging the raw pellets are used to load the pellets into a baking furnace 9 isolated from the atmosphere. .. 9'is a moving grate of the firing furnace 9, 11 is a blower for sucking from a suction box 10 provided below the grate 9 ', and 17 is air for adjusting the O ₂ concentration in the firing atmosphere. It is a blower to introduce. Reference numeral 14 is a bucket conveyor that sends the pellets fired in the firing furnace 9 to the product recovery hopper 15.

The atmosphere of the firing furnace 9 sucked by the blower 11 is circulated into the firing furnace 9. Further, 12 is an ignition device for the firing furnace 9 such as an LPG burner, and 13 is a partition plate of the firing furnace 9.

In the present embodiment, the construction sludge is used by dehydrating the underground excavation work discharged by the reverse method with a filter press and further drying. Properties of construction sludge and coke powder are shown in Tables 1 and 2. The finely crushed paper is used by crushing newspaper with a crusher and passing a screen of 2 mmφ.

[0025]

[Table 1]

[0026]

[Table 2]

Alumina powder (melting point: 2
050 ° C, specific gravity: 3.97) and silica powder (melting point: 17
Dry powder is used for each of 02 ° C. and specific gravity: 2.32).

The finely pulverized paper is put into the hopper 1, the construction sludge into the hopper 2, and the coke powder into the hopper 17, and these are weighed so as to be a target granulation nucleus raw material, supplied to the kneading machine 3, and water 3 40% to 50% by weight of ′ ′ and kneaded and then granulated by the pan-type granulator 4 through the belt conveyor 5 to coat the pellet layer on the granulation nucleus surface layer with the pan-type granulator. It is thrown into the machine 6. The construction sludge from the hopper 2'and the finely pulverized paper from the hopper 1'are weighed and supplied to the kneading machine 16 so as to become the target pellet layer raw material, and the water 16 'is supplied to 20
The kneaded product added by up to 25% by weight is sent to the pan-type granulator 6, where the granulation nucleus is coated with the kneaded product in a two-step granulation process to form a two-layer granulated product. Is obtained.

Further, the above two-layer granulated product is put into a pan type granulator (not shown), and the surface layer of the granulated product is coated with alumina powder or silica powder to complete the granulation work.

The obtained two-layer granulated product is fed from the raw pellet feeding hopper 8 to the fired pellets simultaneously from the bedding floor pellet hopper 8'into a firing furnace 9 which is isolated from the atmosphere, and dried in the firing furnace 9. The two-layer granulated product is sintered through ignition, sintering and cooling steps. Great 9'for this sintering
Sintered pellets are put on the top and spread over to a thickness of 30 mm to make a bedding, and the above granulated material is loaded on it and stacked to a thickness of 200 mm.

While suctioning at a pressure of 30 mm H ₂ O from the suction box 10 below the grate 9 ', 300 ~
After drying with hot air of 500 ° C. for about 10 minutes, the surface of the granulated product is ignited by the igniter 12 (ignition temperature 800 to 1300 ° C.). The firing area of the firing furnace 9 is set to a firing inlet gas amount of 500 to 800.
Sintering is performed for about 40 minutes while controlling the Nm ³ / h and the O ₂ concentration at the firing inlet to be 10 to 21% to obtain an artificial lightweight aggregate. The O ₂ concentration is controlled according to the amount of self-burning substances (finely pulverized paper and coke powder) contained in the granulated product.

The firing test results using the apparatus shown in FIG. 1 are as follows. The aggregate physical properties of Ig.Loss, absolute dry specific gravity, water absorption, and crushing strength were evaluated according to JIS standards.

Table 3 shows the effect of self-burning substances (crushed paper, coke) on the granulation nuclei.

[0034]

[Table 3]

The result of the main calcination is the result of calcination with air (O ₂ : 21%). If the particle size ratio of granulation core / granulation product is 0.7, finely pulverized paper (coke) in the granulation core is obtained. (Including 3% by weight)
It was found that the firing temperature rises with the increase of, and self-combustion can occur. Further, it was found that even if only 50% by weight or more of crushed paper was contained, it would self-combust.

As for the physical properties of the aggregate, the firing temperature is 1030 to 1200.
Those with a temperature of ℃ have an absolute dry specific gravity of 1.09 to 1.25, a water absorption rate of 3.5 to 4.3%, and a crushing strength of 60 to 80 kg / piece, which are low enough to satisfy the physical properties of the artificial lightweight aggregate. We have confirmed that it is possible to manufacture aggregates with low specific gravity and low water absorption.

Table 4 shows the influence of the particle size ratio of the granulation nucleus / granulated product.

[0038]

[Table 4]

When the particle size ratio of granulated core / granulated product is 0.3, even if air-baked, the self-combustible function of the granulated product is completely lost due to lack of self-combustible product (heat generation amount) of the granulated core. Does not happen. When the particle diameter ratio was 0.5, the granulated nuclei granulated with 100% by weight of pulverized paper did not self-combust even due to insufficient calorific value even when air-baked. However, what added 3 to 5 weight% of coke in order to increase the calorific value of a granulation nucleus has a self-combustion effect, and a calcination temperature rises to about 1150 degreeC. However, when the amount of coke is less than 3% by weight, it does not burn by itself, and when it exceeds 5% by weight, the cost increases. When the particle size ratio is 0.8, self-combustion can occur, but the crush strength is lower than the physical properties. On the other hand, when the O ₂ concentration of the firing inlet is 15% or more, there is no problem with the physical properties of the aggregate, but with 10%, the absolute dry specific gravity and the crush strength do not satisfy the standard values.

The effects of the amount of gas at the firing inlet and the alumina powder in the surface layer of the granulated product are as follows. That is, if the firing speed of the granulated product is too fast, the Ig.Loss of the sintered product will exceed the standard value. Therefore, the firing inlet gas amount is optimally 800 to 500 Nm ³ / h. The coating amount of the alumina powder is preferably 3% by weight. If it is less than 3% by weight, the sintered products will be fused to each other and 3% by weight
If it exceeds, the cost will increase. This phenomenon also applies to silica powder. From the above firing results, the firing conditions for the two-layer granulated product in which the pellet layer is coated on the granulation nuclei in this example are as follows. (1) Mixing ratio of self-burning material to granulation core is 30 to 100% by weight of finely pulverized paper and 3 to 5% by weight of coke powder with respect to construction sludge.
Is. (2) The particle size ratio of the granulated nucleus / granulated product is 0.5 to 0.7. (3) The firing temperature is 1000 to 1200 ° C. by controlling the firing inlet O ₂ concentration to 15 to 21%.

Table 5 shows the results of investigating the influence of the amount of crushed paper, using a two-layer granulated product in which the surface layer of the granulated nucleus was coated with construction sludge containing crushed paper as a pellet layer.

[0042]

[Table 5]

As a result, when the amount of pulverized paper in the pellet layer was 3% by weight, the firing temperature was as low as 950 ° C. and the self-combustion was insufficient. When the content is 5 to 10% by weight, self-combustion occurs, the firing temperature also becomes 1100 to 1180 ° C, and the physical properties of the aggregate also satisfy the physical properties. In the case of 15% by weight, the sintered product is fused and the shape is deformed under the main firing conditions, and it is necessary to control the O ₂ concentration to be less than 15% for firing.

[0044]

According to the present invention, as described above,
An artificial lightweight aggregate having excellent physical properties can be manufactured from construction sludge.

That is, a sintered product obtained by firing a two-layer granulated product in which the surface layer of the granulation core of the construction sludge containing crushed paper as a self-burning substance is coated with the construction sludge is completely dried as an artificial lightweight aggregate. Specific gravity 1.09 to 1.45, water absorption rate 3.6 to 6.5%
It has the following physical properties.

Furthermore, the sintered product obtained by firing a two-layer granulated product in which the surface layer of the granulated nucleus is coated with construction sludge and crushed paper is an absolute dry specific gravity of 1.16 to 1.20 which is sufficiently satisfactory as an artificial lightweight aggregate. ,
It has a physical property of water absorption of 8 to 10.0%.

The above-mentioned physical property values can be set to desired values by changing the particle size ratio of the granulation nucleus / two-layer granulated product.

Further, by coating the surface layer of the two-layer granulated product with alumina powder or silica powder as a fusion preventing material,
The sintering temperature range is widened and the product yield is improved.
A layered granulated product is laminated on a grate in a firing furnace that is isolated from the atmosphere, and the oxygen concentration is controlled according to the amount of self-combustible substances contained in the granulated product to perform firing. Aggregate can be manufactured.

[Brief description of drawings]

FIG. 1 is a system diagram of an apparatus used in an embodiment of the present invention.

FIG. 2 is a graph showing high temperature characteristics of construction sludge.

[Explanation of symbols]

1,2,1 ', 2', 17 Hopper 3 Kneader 3'Water 4 Bread type granulator 5 Belt conveyor 6 Bread type granulator 8 Raw pellet feeding hopper 8'Bedding pellet feeding hopper 9 Baking furnace 9'Great 10 Suction Box 11 Blower 12 Ignition Device 13 Partition Plate 14 Bucket Conveyor 15 Product Recovery Hopper 16 Kneader 16 'Water 17 Blower

Claims (4)

[Claims] 1. A pulverized paper or a mixture of pulverized paper and construction sludge is used as a granulation nucleus, and the surface of the granulation nucleus is coated with a construction sludge or a mixture of construction sludge and pulverized paper to form a two-layer granulated product. A method for producing an artificial lightweight aggregate from construction sludge, which comprises firing granules. 2. The method for producing an artificial lightweight aggregate from construction sludge according to claim 1, wherein coke powder or pulverized coal is added to the granulation nucleus. 3. The surface of the two-layer granulated product is coated with alumina powder or silica powder.
A method for producing an artificial lightweight aggregate from the construction sludge described in. 4. A method of laminating a two-layer granulated product on a grate of a firing furnace which is isolated from the atmosphere, and firing while controlling the oxygen concentration according to the amount of self-combustion substance contained in the granulated product. The method for producing an artificial lightweight aggregate from the construction sludge according to any one of claims 1 to 3.