JP2000130942A - Production of soil based powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a soil based powder for city engineering building material or planting by conditioning the moisture content of mud correctly depending on the mean grain size of soil particles or shape variation, evaporating moisture by blowing hot air accompanying a shock wave to mud flow and producing powder directly from mud thereby promoting regeneration of mud. SOLUTION: Rough particles 13 are removed from a material mud 12 by means of a sieve 11 and moisture content of the mud 12 is conditioned in a moisture content conditioning tank 10 based on the mean grain size of soil particles or the content of organic components. Subsequently, the mud 12 is fed through a control valve 8 and a material supply pipe 4 to a powder drying chamber 5. Since exhaust gas from a pulse jet engine 1 located with the forward end of the material supply pipe 4 produces hot air through combustion of fuel being supplied from a fuel supply pipe 2, the material mud 12 is dispersed by a shock wave and heated while being blown by the hot air thus bringing about a dry state. Large particles in the dried mud are collected into a collection tank 14a and small particles are separated through a cyclone 7 and collected into another collection tank 14b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to mud such as construction sludge and dredged mud (including muddy and muddy mud depending on the water content). ) To produce a soil-based powder that can be used for civil engineering building materials, vegetation greening, and the like.

[0002]

2. Description of the Related Art A large amount of construction sludge is generated due to a tunnel excavation work, a building construction, and the like, and a large amount of dredged mud is discharged in a harbor work or a dredging of a bottom soil of a lake or marsh. These muds cannot be reused as they are, and most of them have been landfilled as industrial waste sludge.
However, recycling is being performed, albeit slightly, and in particular, in recent years, development of technologies for recycling such mud has been actively pursued in various fields.

For example, regarding construction sludge, technical guidelines for recycling are compiled by the Ministry of Construction, and technical standards for sediment separation, dehydration treatment, stabilization treatment and the like are set forth. As the dehydration method, various techniques such as centrifugal filtration (screw decanter), pressure filtration (filter press), pressure squeezing filtration (roll press), and high-pressure thin layer dehydration can be applied. I have.

[0004] The stabilizing treatment is a treatment for chemically improving the properties of construction sludge by mixing an improving material. Examples of the improving material include cement and cement-based improving materials, lime (quick lime, slaked lime), and lime-based improving materials. Have been applied.

[0005] In addition, the solid content of the dredged soil is settled and separated in an original mud tank, and the settled mud is extracted by a pump, added with a dehydration aid, concentrated, dewatered, and used as residual soil. Or landfilled. In some cases, a solidifying agent is added to the dewatered cake and used as cover soil. The treated water discharged in the above-mentioned steps of concentration and dehydration is discharged after being subjected to treatments such as coagulation sedimentation and neutralization.

[0006] On the other hand, a water-containing raw material converter (drying device) using a pulse jet engine, which is not intended to treat mud, is known (Japanese Patent Publication No. 6-33).
939). This device generates a wide range of sonic energy by burning the fuel of the pulse jet engine,
The impact on the air layer surrounding the material to be dried allows moisture to be quickly removed from the raw material to be treated. Therefore, raw materials having a high water content can be dried in a short time without going through a dehydration step, and even when treating organic matter, for example, waste fish, scorching or incineration does not occur and nutritional value is not impaired, It is said that the dried product can be easily used as a soil additive or feed.

As an apparatus for directly obtaining a powder product from a slurry-like raw material without going through a dehydration step, a dehydration technique using a spray dryer is known ("Powder and Industry" Vol. 2).
7, NO. 9 (1995) 27-48). This technology employs a method in which the raw material is turned into a slurry, atomized by spraying, and dried by contact with hot air, and is used for the production of powdered synthetic detergents and the drying of powders such as ceramics, ferrite, and oxides. I have.

[0008]

In the prior art described above, dewatering by a screw decanter or filter press used in dewatering mud, roll dewatering,
In high-pressure thin-layer dehydration or the like, mud solidifies during dehydration and does not turn into a powdery state, so that it is difficult to uniformly mix with an improving agent when performing a stabilization treatment. Therefore, the performance (strength) of the recycled material obtained by the above-mentioned mixing treatment is low, and in order to enhance the performance, a large amount of an improver must be added, resulting in a problem such as an increase in cost.

On the other hand, it is conceivable to apply a spray dryer type drier which has an advantage that a raw material in a slurry state can be made into a powder without going through a dehydration step, for drying mud. However, a powdery material cannot be obtained, and the cost must be increased.

[0010] The pulse jet engine drying technique is also a technique for directly drying a raw material having a high water content without performing a dehydration treatment. However, what is specifically indicated as an application field of this technology in the above-mentioned patent gazette is the removal of water contained in a large amount in organic matter, particularly, the treatment of waste fish with high nutritional value. Feed. Mud such as construction sludge and dredging mud has completely different properties from such organic matter.
In addition, since the amount of generation is extremely large and its physical properties are significantly different depending on where it is generated, there is no established drying technology that can efficiently dry these enormous amounts of mud and effectively utilize the obtained powder. is there.

[0011] The present invention, as a part of the technology for actively promoting the recycling of mud such as construction sludge and dredging mud, treats the mud to obtain a soil-based powder that can be used for civil engineering building materials, vegetation greening, and the like. It is an object to provide a method for producing a.

[0012]

Means for Solving the Problems In treating mud such as construction sludge and dredging mud, the present inventors have reduced the cost required for transporting the mud and improved the solidifying agent,
Alternatively, in order to facilitate uniform mixing with an additive or the like for imparting a function such as adjustment of water permeability or pH, studies were repeated on the premise that mud is made into a powder (soil-based powder).
As a result, the present inventors have newly found that by applying appropriate pretreatment to mud, it is possible to apply the technology utilizing the impact of sound waves employed in the above-described pulse jet engine drying technology. Reached.

The gist of the present invention resides in the following method for producing a soil-based powder.

[0014] A method for producing a soil-based powder, which is obtained by drying mud and making it into a powder, wherein the water content of the mud is determined at least according to a change in the average particle size and shape of the soil particles contained in the mud. A method for producing a soil-based powder, characterized in that hot water with a shock wave is blown onto the mud flow after adjusting the water content ratio to evaporate the water, thereby obtaining the powder directly from the mud.

Here, "mud" is, as described above,
This refers to construction sludge with a lot of moisture generated by construction work (excluding dredging) such as tunnel excavation work and building work, and dredging mud generated by harbor work and dredging of the bottom soil of lakes and marshes.

The "water content ratio of mud" is the weight ratio of water to solid content (ie, soil contained in mud) (moisture / solid content). The weight ratio (moisture / solid content) or the weight percentage is indicated.

"Hot air accompanied by a shock wave" is a flow of a high-temperature gas, and means a gas flow through which a shock wave propagates using this gas as a medium. The shock wave is, for example, a wave having a kind of discontinuous surface in which the pressure, density, and the like of a fluid (gas) generated during combustion rapidly increase.

The method of the present invention can be easily carried out by using the pulse jet engine as a device for generating hot air accompanied by a shock wave and supplying the mud after adjusting the water content into the exhaust gas of the pulse jet engine. .

Further, when an oxidizing agent is added to the hot air blown to the flow of the mud after adjusting the water content ratio, it is possible to oxidize and remove organic substances in the mud.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a soil-based powder of the present invention (hereinafter, also referred to as “method of the present invention”) will be specifically described.

It is extremely difficult to dry mud such as construction sludge and dredged mud by using hot air accompanied by a shock wave, for example, high-temperature gas obtained by operation of a pulse jet engine, to dry it. Can not get. This is because the properties of the mud to be treated vary widely, and it is necessary to improve the dispersion state of the soil particles in the mud before blowing hot air accompanied by a shock wave.

Therefore, in the method of the present invention, prior to the treatment, the mud is subjected to a pretreatment for adjusting the water content to a predetermined range in accordance with the properties thereof. The reason for “according to the properties” is that the range of the appropriate water content of the mud varies depending on the properties of the mud.

The properties of the mud are determined by considering at least (a) the average particle size of the soil particles contained in the mud and (b) the shape of the soil particles contained in the mud. The average particle size of the soil particles may be used by indexing the particle size distribution of the soil particles.
In the case where solids having a large particle size are mixed, it is preferable to remove particles having a particle size of 3 mm or more in advance. In addition, it is preferable that the surface shape of the grains is indexed and used together with the shape of the soil particles. In addition, if factors that have a large effect on the properties of the mud are recognized depending on the type of mud, those factors should also be considered. For example, an organic component corresponds to this. This is because organic components may be contained in the mud.

That is, in the method of the present invention, the water content of the mud is determined in accordance with at least the average particle size and shape of the soil particles contained in the mud, and the change in the average particle size and shape of the soil particles. Pretreatment is performed to adjust the water content within the range. In addition, the above-mentioned "proper water content of the mud" means that the dispersed state of the soil particles in the mud is good, and the mud flow can be smoothly and smoothly subjected to the drying treatment, and the flow of the mud is blown with hot air accompanied by a shock wave. This is the water content ratio at which the soil-type powder is obtained when water is easily evaporated and removed.

The appropriate moisture content range of the mud is determined by using the mud to be treated, changing the conditions, and actually performing the drying process.
It is better to ask in advance. In addition, by collecting the data obtained in this way and graphing the relationship between the average particle size and shape of the soil particles contained in the mud and the range of the appropriate water content ratio of the mud, it is easy to use and effective. is there.

Next, the thus obtained mud having a controlled water content (since this mud is a raw material for the soil-based powder produced by the method of the present invention, it is also referred to as a "raw material" or a "raw material slurry" hereinafter). Hot water with a shock wave is blown onto the stream to evaporate the water, and the mud is directly powdered without going through a dewatering step.

The hot air (hereinafter, “hot air” means a hot air accompanied by a shock wave) is blown onto the “flow of mud” in order to effectively evaporate water from the raw material slurry. It is. To create a mud flow,
For example, the raw slurry may be continuously flowed from a nozzle having a circular or elliptical cross section. A plurality of nozzles may be used, or a thin strip-shaped flow may be formed using a slit-shaped nozzle.

The raw slurry is blown off by blowing hot air accompanied by a shock wave on the flow of the mud, and at the same time, the water and the soil particles in the raw slurry are finely dispersed by the action of the shock wave, and the water (liquid) inside the soil particles is removed. The particles ooze on the surface of the particles and are blown off by a shock wave, and evaporate quickly because they are in a high-temperature airflow. That is, the evaporation of water is remarkably promoted, and the powder can be directly made into a powder without a dehydration step.

The method of the present invention can be easily and effectively carried out by using a pulse jet engine as a device for generating hot air accompanied by a shock wave and supplying the raw material slurry into the exhaust of the pulse jet engine.

When an organic component is contained in the mud, adding an oxidizing agent to the hot air blown to the raw slurry is effective in burning and oxidizing organic substances in the slurry. Note that air, oxygen gas, or the like can be used as the oxidizing agent.

The adjustment of the water content of the raw slurry may be performed as described above so that the water content falls within the range of the appropriate water content determined in advance. If the range of the appropriate water content can be determined from the measured values of the properties of the mud, various cases can be dealt with, which is simple and effective.

In the following formula (1), when the average particle size of the soil particles is small, it is necessary to increase the water content in order to improve the dispersion state of the soil particles in the slurry, and conversely, the average particle size is large. Based on the fact that the amount of moisture may be small in this case, the equation is obtained as a result of conducting experiments on various cases and investigating the dispersion and drying state of the soil particles. By using this equation (1), it is not necessary to determine the relationship between the average particle size and shape of the soil particles contained in the mud and the range of the appropriate water content ratio of the mud each time the treatment is performed, or it is not necessary to determine the relationship in advance. Thus, the dispersion state of the soil particles can be made good, and the range of the appropriate water content ratio at which the powder can be produced can be easily obtained.

−0.015 (logd _p ) ³ +0.160 (logd _p ) ² −0.467 logd _p + 3.81 ≧ log W ₁ ≧ 0.103 (logd _p ) ³ −0.210 (logd _p ) ² −0.573 logd _p +2.46 (1) where φ = 0.6 to 1.0 where, W ₁ : water content (%) d _p : average particle size (μm) φ: shape factor (here, sphericity is adopted. That is,
(The ratio between the surface area of a sphere having the same volume as the soil particles and the surface area of the soil particles is 1 for a complete sphere.) An example of an apparatus for carrying out the method of the present invention is shown below. All of them are devices using a pulse jet engine, and these devices were used in Examples described later.

FIG. 1 is a diagram showing an example of the configuration of a drying apparatus having a powder drying chamber in which exhaust gas from a pulse jet engine is directed downward.

As shown in the figure, the drying apparatus includes a sieve 11 for removing dust and coarse particles 13 from raw mud (as-generated mud) 12 and a water content adjusting tank provided immediately below the sieve 11. 10, a raw mud supply tank 9 for supplying raw mud 12 after adjusting the water content to a powder drying chamber 5, and a powder drying chamber in which a pulse jet engine 1 for supplying hot air with a shock wave is mounted on an upper portion thereof. 5, a cyclone 7 provided adjacent thereto, and a powder drying chamber 5 and dry powder recovery tanks 14a and 14b attached immediately below the cyclone 7, respectively. The pulse jet engine 1 includes a fuel supply pipe 2 and a combustion air supply pipe 3.

After the dirt and coarse particles 13 are removed from the raw mud 12 by the sieve 11, the average particle diameter of the soil particles, the shape of the soil particles, Adjustment of the water content is performed based on the relationship between at least one of the content of the organic component and the appropriate water content of the mud,
The powder is supplied to the powder drying chamber 5 through the control valve 8 and the raw material supply pipe 4. The tip of the raw material supply pipe 4 is located in the exhaust of the pulse jet engine 1, and the exhaust of the pulse jet engine 1 becomes hot air due to the combustion of the fuel supplied to the engine 1 via the fuel supply pipe 2. Therefore, the supplied raw mud 12 is dispersed by the shock wave and heated while being blown off by the hot air, and the water is evaporated to be in a dry state. In order to completely burn the fuel, the secondary air for combustion is supplied from the secondary air supply pipe 6 attached near the position (height) of the tip of the raw material supply pipe 4 on the side wall of the powder drying chamber 5. Supplied.

The mud having a relatively large particle diameter in the mud dried in the powder drying chamber 5 is collected in a dry powder collecting tank 14a attached immediately below the powder drying chamber 5, and the small particle diameter is exhausted. Enters the cyclone 7 where it is separated from the exhaust gas and collected in the dry powder recovery tank 14b.

The powder recovered in the dry powder recovery tanks 14a and 14b is easily transported, has good mixing with an improving agent, a solidifying agent, and the like, and can be effectively recycled as a soil-based powder.

FIG. 2 is a diagram showing an example of a configuration of a drying apparatus having a powder drying chamber in which exhaust gas from a pulse jet engine is directed in a horizontal direction. As the exhaust of the engine is directed in the horizontal direction, the mounting positions of the pulse jet engine 1, the secondary air supply pipe 6, and the raw material supply pipe 4 are different from those of the apparatus shown in FIG. There is no difference in composition.

The raw mud 12 is supplied into the exhaust of the pulse jet engine 1 through the raw material supply pipe 4, is dispersed by a shock wave, is heated while being blown off by hot air, and is evaporated to a dry state by evaporating moisture. Those having a relatively large particle size are collected in a dry powder recovery tank 14a attached to the lower portion on the exhaust side of the powder drying chamber 5, and those having a small particle size are collected in a dry powder recovery tank 14b attached to the lower portion of the cyclone 7. Collected.

According to the method of the present invention described above, construction sludge,
Dry mud such as dredging mud, dam sediment (inflow sediment, sediment mud), and other mud-like inorganic powders generated during harbor construction and the dredging of the bottom soil of lakes, etc. Soil powder that can be used for planting, vegetation greening and the like. Since the process can be simplified, equipment costs can be reduced. In addition, the obtained soil-based powder removes a large amount of water contained in the mud, so that the transportation cost can be significantly reduced, and the mixture with an improving agent or a solidifying agent upon reuse is improved. Is good.

[0042]

(Example 1) Using an apparatus having the structure shown in Fig. 1, the method of the present invention is applied to mud generated at the time of dredging of lakes and marshes, and dried powder (soil-based powder) ) Manufactured. The drying capacity of the apparatus was 20 kg / h, and kerosene was used as fuel for the pulse jet engine. For comparison, a dehydration treatment was performed using a filter press to obtain a dewatered cake.

Next, a solidifying agent (cement-based solidifying agent) was mixed with these powders or dewatered cakes, and the mixing properties at that time were compared.

Table 1 shows the characteristics of the mud (raw mud) used.
In the treatment, the properties of the raw slurry obtained by adjusting the water content of the raw mud are shown in Table 2, and the drying conditions of the raw slurry are shown in Table 3. In addition, adjustment of the water content of the raw mud, the range of the appropriate water content of mud generated during dredging of lakes and marshes,
I went so that it was within that range.

Table 4 shows the properties (moisture content) of the obtained dry powder.
Was as shown in FIG.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

On the other hand, the water content of the dehydrated cake obtained in the comparative example was 300%.

A cement solidifying agent was mixed with each of the powder and the dewatered cake so as to be 16% by weight based on the weight of the solid content, and the mixing properties were compared. Table 5 shows the results. In Table 5, the degree of mixing M is an index defined by the following equation (2). M = 0 when completely mixed, and M = 1 when not mixed.

[0052]

(Equation 1)

As is evident from the results, the powder obtained by applying the method of the present invention was clearly better in mixing with the solidifying agent than the comparative example.

[0054]

[Table 5]

(Example 2) Using the apparatus having the configuration shown in FIG. 2, the method of the present invention is applied to the mud generated during the tunnel shield method, and the dry powder (soil-based powder) is processed. Manufactured. The drying capacity of the device is 20kg
/ H, kerosene was used as fuel for the pulse jet engine. For comparison, a dehydration treatment was performed using a filter press to obtain a dewatered cake.

Next, as in the case of Example 1, a solidifying agent (cement-based solidifying agent) was mixed with these powders or dehydrated cakes, and the mixing properties at that time were compared.

Table 6 shows the characteristics of the mud (raw mud) used.
In the treatment, the properties of the raw slurry obtained by adjusting the water content of the raw mud are shown in Table 7, and the drying conditions of the raw slurry are shown in Table 8. In addition, the adjustment of the water content of the raw mud was performed so that the range of the appropriate water content of the mud generated at the time of the tunnel shield construction method was obtained and was within the range.

Table 9 shows the properties (moisture content) of the obtained dry powder.
Was as shown in FIG.

[0059]

[Table 6]

[0060]

[Table 7]

[0061]

[Table 8]

[0062]

[Table 9]

On the other hand, the water content of the dehydrated cake obtained in the comparative example was 250%.

A cement solidifying agent was mixed with each of the powder and the dewatered cake so as to be 16% by weight based on the weight of the solid content, and the mixing properties were compared as in Example 1. Table 10 shows the results.

As is evident from the results, the mixability of the powder obtained by applying the method of the present invention with the solidifying agent was clearly better than that of the comparative example.

[0066]

[Table 10]

[0067]

According to the method of the present invention, mud such as construction sludge and dredging mud is directly dried without going through a dewatering step to produce an earth-based powder that can be used for civil engineering building materials, vegetation revegetation, etc. Can be. The process can be simplified, and the transportation cost can be significantly reduced. Since it is a powder, there is also an advantage that the mixing property with an improving agent, a solidifying agent, and the like is extremely good.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of an apparatus for performing a method of the present invention.

FIG. 2 is a diagram showing the configuration of another example of an apparatus for performing the method of the present invention.

[Explanation of symbols]

 1: Pulse jet engine 2: Fuel supply pipe 3: Combustion air supply pipe 4: Raw material supply pipe 5: Powder drying chamber 6: Secondary air supply pipe 7: Cyclone 8: Control valve 9: Raw mud supply tank 10: Water containing Ratio adjustment tank 11: sieve 12: raw mud 13: dust, coarse particles 14a, 14b: dry powder recovery tank

Claims (3)

[Claims] The present invention relates to a method for producing an earthy powder, which is a method of drying a mud to produce a powder, wherein the water content of the mud is determined at least according to a change in the average particle size and shape of the soil particles contained in the mud. Manufacture of soil-based powder characterized in that the water content is adjusted to fall within the range, and the flow of the mud after adjusting the water content is blown with hot air accompanied by a shock wave to evaporate water and obtain powder directly from the mud. Method. 2. The soil type powder according to claim 1, wherein a pulse jet engine is used as a device for generating hot air accompanied by a shock wave, and mud after adjusting the water content is supplied into the exhaust of the pulse jet engine. Manufacturing method. 3. The method according to claim 1, wherein an oxidizing agent is added to the hot air blown to the flow of the mud after adjusting the water content.