JPH1112568A - Artificial sand useful for dehydration method of construction for soft soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain artificial sand useful for dehydration method of construction for soft soil, formed from a solid material prepared by melting and solidifying an incombustible material contained in nonindustrial waste, industrial waste and excreta disposal treatment residue. SOLUTION: Nonindustrial waste and industrial waste thrown into a direct melting furnace 1 are firstly dried at the upper part of the melting furnace 1, thermally decomposed at the middle part of the melting furnace 1, burned and melted at the lower part of the melting furnace 1 and discharged as slag from a slag outlet 1d. The slag is dropped in a water cooling tank 4 below the direct melting furnace 1, quenched by water as a cooling medium for the water cooling tank 4 and the slag is granulated by water in the cooling into a solid material having about 100 μm to 5 mm particle diameter. The solid material is transported by a belt conveyor 5 of the water cooling tank 4 to an artificial sand pit 6 and used as artificial sand for dehydration method of construction for soft soil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial sand used for a method of dewatering soft soil for improving the ground of soft ground, and a method for producing the artificial sand.

[0002]

2. Description of the Related Art A method using sand called a packed drain method, a sand drain method, or the like is widely practiced as a method for improving soft ground in a landfill. For example, this sand drain method is a method in which a large number of sand pile drains are installed in the ground, and pore water in the soft ground is drained to the ground through this drain to harden the soft ground. A water-permeable bag is suspended in a casing pipe having a lid that can be opened and closed at the lower end, and after filling the bag with sand, the casing pipe is pulled out and a sand pile drain is installed in the ground. It is a method of hardening soft ground in a short period of time by draining pore water in the ground to the ground through drains. In these construction methods, it is indispensable to install a drain of sand pile in the ground, and sand is an important factor.

[0003]

As described above, sand is indispensable in the dewatering method for soft soil, and so-called river sand collected from rivers was generally used before. However, river sand has been depleted in recent years, and its collection has become difficult. Therefore, there was a technical problem that sand became expensive and construction cost increased. On the other hand, so-called sea sand may be used as an alternative to river sand.However, sea shells are mixed in sea sand, so bags may be cut off in the packed drain method, which is not very preferable. Was. Therefore, at present, so-called mountain sand is generally used, but mountain sand contains a large amount of silt component, and sand containing a large amount of this silt component is used in each method when it contains a lot of moisture. It has adhered to the inner wall of the sand supply device and the vicinity of the sand supply port, causing a new technical problem that the supply of sand is hindered.

To solve these problems, Japanese Patent Laid-Open No.
In the method for dehydrating a hydrated soft soil described in -147033, it has been proposed to use granulated blast furnace slag. However, when granulated blast furnace slag is used, it contains a large amount of calcium, and when dewatering is performed, alkaline drainage is generated and a neutralization treatment is required, which is not preferable. Further, in a vertical drain construction method for accelerating the compaction of soft clay ground described in JP-A-4-185810, it has been proposed to use a crushed concrete material. However, not only is a step for crushing the concrete necessary, but also because the particle size of the crushed concrete is not constant, it has not been a very preferable alternative to the conventional sand.

[0005] The inventors of the present invention have conducted intensive studies in search of a substitute for sand used in a dewatering method for soft soil, and have conducted non-combustible substances contained in general waste, industrial waste, human waste treated sludge, and sewage treated sludge. Has been found to be suitable as a substitute for sand used in the dewatering method for soft soils. Moreover, in general, incineration residues such as general waste, industrial waste, human waste treated sludge, sewage treated sludge, and the like are generally landfilled. These wastes may contain heavy metals such as lead, chromium, cadmium, and mercury, and pollution in the landfill treatment due to elution of these heavy metals has become a problem. By melting and solidifying incombustible substances contained in general waste, industrial waste, human waste treatment sludge, and sewage treatment sludge, the present inventors have developed lead, chromium, cadmium, mercury and other heavy metals contained in waste. In addition to preventing dissolution and using the solidified product as a substitute for sand used in the dewatering method for soft soil as described above, it is possible to solve the problem of space for landfill and the problem of pollution in landfill Was found.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional technical problems as described above,
The purpose of the present invention is to provide artificial sand used for the dewatering method of soft soil formed by solidification obtained by melting and solidifying incombustible substances contained in industrial waste, human waste treatment sludge, sewage treatment sludge. is there.

[0007]

The artificial sand used in the soft soil dewatering method according to the present invention for solving the above-mentioned technical problem is to cool and solidify slag obtained by melting incombustible substances contained in waste. It is characterized by being formed by doing. The artificial sand used in the soft soil dewatering method according to the present invention that solves the above-mentioned technical problems is obtained by melting ash from incineration ash obtained by incinerating waste with a pyrolysis gasification melting furnace or waste with an incinerator. It is characterized by being formed by cooling and solidifying slag obtained by melting in a furnace.

Here, it is preferable that the waste is general waste, industrial waste, human waste treatment sludge, or sewage treatment sludge. Preferably, the slag is formed by rapid cooling by water cooling. Further, the particle diameter of the solidified product obtained by cooling and solidifying the slag obtained by melting is 100 μm or more and 5 μm or more.
mm or less, and the particle size of the solidified material obtained by cooling and solidifying the slag obtained by melting is 250 μm or more
mm or less, and the solidified body has a cumulative weight percentage of 90%.
% Or more, and preferably has a 50% weight average diameter of 0.5 mm or more, particularly 1 mm to 3 mm. Further, it is preferable that corners of the outer shape of the solidified body obtained by cooling and solidifying the slag obtained by melting are removed.

The artificial sand used for the dewatering method of the soft soil thus constituted is composed of SiO ₂ and Al contained in the slag.
_{Since 2} O ₃ forms a glass skeleton and takes in heavy metals, the heavy metals do not elute. Especially,
When the slag is quenched by water cooling to form a solidified body, the solidified body is further vitrified and crushed by quenching, so that the particle diameter is 100 μm or more.
mm or less can be obtained. In particular, since the solidified material having a particle diameter of 100 μm or more and 5 mm or less is the same as the particle diameter of conventional river sand or the like used in the dewatering method of soft soil, as a substitute for sand used in the dewatering method of soft soil, It can be used as it is.

[0010] The particle size of the solidified product is 250 μm or more and 4 m or more.
m and not less than 90% by weight of the solidified body in terms of the cumulative weight percentage, and the 50% weight average diameter is 0.1%.
Since artificial sand having a diameter of 5 mm or more has good water permeability, dehydration of soft soil can be easily performed. Furthermore, since the outer shape of the artificial sand from which the corners of the solidified body obtained by cooling and solidifying the slag obtained by melting are removed is rounded,
For example, even if a water-permeable bag is used as in the packed drain method, the bag is not cut. Further, since the external shape of the artificial sand is rounded, the operator is not hurt when supplying sand to the sand supply device used in each method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing artificial sand used in a method for dewatering soft soil according to the present invention will be described in detail with reference to FIG. Reference numeral 1 in FIG. 1 denotes a direct melting furnace for burning and melting waste such as general waste, industrial waste, human waste treatment sludge, sewage treatment sludge, and the like. Oxygen for combustion is supplied from the apparatus 2 to the melting furnace 1
An oxygen supply port 1a is formed so as to be supplied inside. In the upper part of the melting furnace 1, waste is supplied to the melting furnace 1 directly from a waste pit 3 in which general waste, industrial waste, and the like are stored by means of a feeding machine (not shown). Thus, the waste inlet 1b is formed. Further, a gas outlet 1c is formed at the upper end of the direct melting furnace 1 to guide the pyrolysis gas generated from the waste to a secondary combustion chamber (not shown). In the secondary combustion chamber, the combustion of the gas is performed, and the heat is recovered and used effectively. The waste gas from the secondary combustion chamber is H
After the fly ash is removed by the removal of the acidic gas such as cl and SO _X and the dust collector, it is released to the outside. Some or all of the fly ash collected by this dust collector is again
Is supplied together with the waste and can be used as a raw material.

Although not shown, a burner for auxiliary combustion is provided at the bottom of the direct melting furnace 1, and a slag discharge port 1d for discharging slag melted by the direct melting furnace 1 is provided. ing. A water cooling tank 4 for cooling the slag discharged from the slag discharge port is provided below the slag discharge port 1d, and the slag falls directly into a water cooling tank 4 provided below the melting furnace 1. Then, it is configured to be quenched there. The water-cooling tank 4 is provided with a conveying means 5 such as a belt conveyor, and the solidified material cooled and solidified by the water-cooling tank 4, that is, the artificial sand
It is configured to be conveyed to. In addition, artificial sand pit 6
Is used to store artificial sand. The artificial sand is removed from the artificial sand pit as needed, and used for the dewatering method of soft soil.

The general waste and industrial waste put into the direct melting furnace 1 having the above-mentioned structure are first dried in the upper part of the melting furnace 1, pyrolyzed in the middle part of the melting furnace 1, and decomposed in the middle part of the melting furnace 1. It is burned and melted in the lower part. High-concentration oxygen is supplied to the combustion and melting zone of the direct melting furnace 1 from the oxygen production apparatus 2 described above, and reacts with the char (mainly carbon) generated by the thermal decomposition of the waste. The temperature in the lower part is kept between 1350C and 1650C. Due to this high temperature, the incombustible waste is melted and discharged from the slag discharge port 1d. The slag discharged from the slag discharge port 1d is at 1350 ° C. to 1650 ° C., falls directly into a water cooling tank 4 provided below the melting furnace 1, and is rapidly cooled by water as a cooling medium of the water cooling tank 4. You. At this time, the slag is granulated into a solid having a particle size of about 100 μm to 5 mm. The solidified body is conveyed to an artificial sand pit 6 by a belt conveyor 5 of a water cooling tank 4.

In the above embodiment, the case where the solidified material (artificial sand) is formed using a direct melting furnace has been described, but the type of the furnace is not particularly limited, and the incombustible material in the waste is not limited. Any material can be used as long as it can be melted. Therefore,
It may be a fluidized bed type, a rotary kiln type, a shaft type, a retort type, or the like.

In the above embodiment, the case where the incombustible waste is directly melted using a direct melting furnace has been described. First, the waste is incinerated in an incinerator, and the ash is melted in an ash melting furnace. Even when solidified, a similar solidified body (artificial sand) can be obtained. The incinerated ash includes not only incinerated ash discharged from the incinerator but also fly ash. This fly ash can be captured by a bag filter, an electric dust collector, or the like, which is an auxiliary equipment of the incinerator. The type of ash melting furnace is not particularly limited as long as the ash can be melted. For example, a ash melting furnace such as a combustion type, an arc type, a plasma type, a resistance type, and a low frequency induction type ash melting furnace can be used.

Further, in the above embodiment, the solidified material cooled or solidified by the water cooling tank 4, ie, the artificial sand, is transported to the artificial sand pit 6, and the artificial sand is carried out from the artificial sand pit as necessary, and It is configured to be used for the dewatering method. However, since the solidified body is rapidly cooled by water and crushed, a sharp corner may be formed in the crushed portion (vitrified portion), and there is a possibility that an operator may be injured by the corner. Therefore, before or after being conveyed to the artificial sand pit 6, it is preferable to load the solidified body into a rotating drum and remove the corners.

[0017]

Next, an embodiment of the artificial sand used in the method for dewatering soft soil according to the present invention will be described. First, when analyzing the general waste, for example, the municipal garbage, which is the raw material of the artificial sand according to the present invention, it is constituted by the composition shown in Table 1,
The water, ash, and combustibles of the municipal waste are contained as shown in Table 2.

[0018]

[Table 1]

[0019]

[Table 2]

The above-mentioned municipal waste was put into the above-mentioned direct melting furnace, and the composition of the molten and solidified slag was analyzed. The results shown in Table 3 were obtained. The results shown in Table 3 are shown in terms of% by weight in terms of oxide. The numerical value indicated by <in the table indicates that the item is below the lower detection limit.

[0021]

[Table 3]

As is clear from the above analysis results, it is understood that silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) which form the skeleton of glass are contained in large amounts.

Then, the slag discharged from the slag discharge port of the direct melting furnace is dropped into a water-cooled tank, quenched by water (water temperature 90 ° C.) in the water-cooled tank, and the particle size of the solidified material (artificial sand) at this time is reduced. Was measured. The result is shown in FIG. This figure shows the particle distribution in terms of cumulative weight%. In FIG. 2, for example, 1000 μm is shown to be 20%, which means that the solidified material (artificial sand) is sieved with a sieve having an opening of 1000 μm. Indicates that the weight of the particles passing through the sieve is 20% of the whole. That is, FIG. 2 shows the weight% under the sieve corresponding to each particle size.
As apparent from FIG. 2, it was found that the minimum diameter of the solidified particles was about 100 μm, and the maximum diameter of the particles was about 5 mm. Moreover, 250 mm or more and 4 mm
The particles having the following particle diameters were contained in an amount of 95% by weight or more, and it was confirmed that they had almost the same particle diameter as sand used in the dewatering method for soft soil. In addition, as shown in FIG. 2, the solidified body (artificial sand) has a 50% weight average diameter (when the solidified body (artificial sand) is sieved with a sieve, the weight of particles passing through the sieve is 50% of the whole). (The opening of the sieve at that time) was found to be about 2 mm.

As a result of measuring the water permeability of the solidified material (artificial sand), the water permeability of the sand was 10 ^-1 mm / sec to 10 ^-3.
mm / sec, 1 to 10 mm / sec. The specific gravity of the solidified material (artificial sand) was measured, and as a result, the bulk specific gravity was 1.5 to 1.7 (g / cm ³ ), and the true specific gravity was 2 to ⁴ g.
/ Cm ³ . From this, the solidified body (artificial sand) is excellent in water permeability, and can obtain good dehydration in the dewatering method for soft soil. In addition, it was recognized that the solidified material (artificial sand) can be handled in the same manner as conventional sand because the specific gravity is substantially the same as river sand or the like used in the dewatering method of soft soil.

Next, the solidified product (artificial sand) was subjected to a dissolution test, and as a result, it was proved that the product was suitable for the Notification Nos. 13 and 46 of the Environment Agency. This Environment Agency Notification No. 46 is a soil standard for fields and is stricter than the Environment Agency Notification No. 13 which is a standard for landfill. Table 4 below
The reference values, analysis methods, and analysis values of Environment Agency Notification No. 46 are shown below. As can be seen from these results, no elution of harmful heavy metals such as Pb and Cd was observed, and it was found that the artificial sand was sufficiently usable for the dewatering method of soft soil. In the table,
In the analysis value column, the numerical value indicated by the symbol <indicates that the item is below the lower detection limit. In the column of analysis method, for example, JIS K 0102-54 indicates that the analysis was performed by the method specified in JIS K 0102-54, and Annexes 59 and 3 of the Announcement No. 59 of the Environment Agency Notification No. 59 are specified. This indicates that the analysis was performed by the method described above. In the judgment, the symbol “判定” indicates that the reference value has been cleared.

[0026]

[Table 4]

The artificial sand used in the method for dewatering soft soil according to the present invention can be applied to any method other than the packed drain method as long as it is a method for dewatering soft soil using sand. Things. The artificial sand used in the method for dewatering soft soil according to the present invention may be used alone or in combination with natural sand such as river sand. Further, artificial sand used in the dewatering method for soft soil according to the present invention,
The solidified material outside the range of 100 μm to 5 mm may be selected by using a screening means such as a sieve. Similarly, sorting is performed so that the particle size of the solidified body is 250 μm or more and 4 mm or less, the solidified body is 90% by weight or more in terms of cumulative weight percentage, and the 50% weight average diameter is 0.5 mm or more. Adjusted artificial sand may be used.

[0028]

As described above, the artificial sand used in the method for dewatering soft soil according to the present invention is composed of Si contained in slag.
Since O ₂ and Al ₂ O ₃ form a glass skeleton to take in heavy metals, the heavy metals do not elute. Therefore, even when this artificial sand is used in the dewatering method for soft soil, no pollution such as elution of heavy metals is caused. Moreover, the artificial sand used in the soft soil dewatering method according to the present invention is formed by melting and solidifying general waste, industrial waste, human waste treatment sludge, incombustible substances contained in sewage treatment sludge, and the like, This has the effect of solving the problem of space for landfilling waste.

In particular, since the artificial sand used in the dewatering method for soft soil described in Item 4 is formed by rapidly cooling the slag by water cooling, the slag is gradually cooled by air cooling. Compared with vitrification, the vitrification is further promoted and the particles are crushed by rapid cooling, so that the particle diameter of the artificial sand can be reduced.

The artificial sand used in the soft soil dewatering method described in claim 5 has a particle diameter of 100 μm or more.
mm or less, because it is the same as the particle size of river sand,
This has the effect that it can be used as it is as a substitute for sand used in the dewatering method for soft soil.

In the artificial sand used in the soft soil dewatering method according to claim 6, the solidified material obtained by cooling and solidifying the slag has a particle size of 250 μm or more and 4 mm or less, and the solidified material has a cumulative weight percentage of 90%. % By weight and a 50% weight average diameter of 0.5 mm or more, so that it has good water permeability. As a result, good dewatering properties can be obtained in the dewatering method for soft soil.

Further, the artificial sand used in the dewatering method for soft soil described in claim 6 has a rounded outer shape, and thus uses a water-permeable bag as in the packed drain method, for example. Also, without cutting the bag,
When the sand is supplied to the sand supply device used in each method, the effect is obtained that the worker is not hurt.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a production apparatus for producing artificial sand according to the present invention.

FIG. 2 is a diagram showing the relationship between the particle size of artificial sand and the cumulative weight percentage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Direct melting furnace 2 Oxygen production apparatus 3 Waste pit 4 Water cooling tank 5 Conveyor 6 Artificial sand pit

Claims (7)

[Claims] An artificial sand for use in a dewatering method for soft soil, wherein the artificial sand is formed by cooling and solidifying slag obtained by melting incombustibles contained in waste. 2. An incineration ash obtained by incinerating waste in a pyrolysis gasification melting furnace or an incinerator of waste in an incinerator, using an ash melting furnace.
An artificial sand used in a dewatering method for soft soil, which is formed by cooling and solidifying a slag obtained by melting. 3. The method for dewatering soft soil according to claim 1, wherein the waste is general waste, industrial waste, human waste treatment sludge, or sewage treatment sludge. Artificial sand. 4. The slag is formed by rapid cooling by cooling the slag with water.
Artificial sand used in the soft soil dewatering method described in any one of the above. 5. The method for dewatering soft soil according to claim 1, wherein a particle size of a solidified material obtained by cooling and solidifying the slag obtained by melting is 100 μm or more and 5 mm or less. Artificial sand used for. 6. A solidified product obtained by cooling and solidifying a slag obtained by melting has a particle size of 250 μm or more and 4 mm or less,
The softness according to any one of claims 1 to 5, wherein the solidified body contains 90% by weight or more in terms of a cumulative weight percentage and a 50% weight average diameter is 0.5 mm or more. Artificial sand used for soil dewatering. 7. The method for dewatering soft soil according to claim 1, wherein corners of an outer shape of a solidified body obtained by cooling and solidifying the slag obtained by melting are removed. Artificial sand used for.