JP3436690B2 - Dewatering and solidification of high water content slurry - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for efficiently dewatering a highly water-containing slurry that is difficult to dewater, such as dredged bottom mud and construction sludge, and making effective use of a dewatered cake.

[0002]

2. Description of the Related Art In recent years, a lot of dredging work has been carried out in rivers and lakes for the purpose of improving water quality, but the treatment of a large amount of dredged bottom mud has become a problem. In addition, construction sludge discharged from construction sites has a shortage of disposal sites, so there is an urgent need to improve the efficiency of treatment technology and the development of effective utilization technology. Since most of these dredged bottom mud and construction sludge are highly water-containing slurries and are difficult to handle such as transportation, they are dehydrated to reduce the volume. As the dehydration treatment method, various mechanical methods represented by sun drying or filter press are adopted, but sun drying requires a vast treatment area and a long treatment time, so that dredged bottom mud and construction sludge In many cases, since the particles are fine and the dredged bottom mud contains a large amount of organic matter, its dehydration is generally very difficult. Not only is mechanical dewatering inevitably high in processing costs, but the dewatering method adopted is not sufficient for some target soils, and it is easily fluidized or re-muddyed, and reused as civil engineering materials or landfill soil. If it is difficult to use as.

In such a case, a cement-based solidifying material or a lime-based solidifying material is further added to the soil or the dehydrated cake after the dehydration processing, or a mechanically-dehydrated material is added in advance to the cement-based solidifying material or the lime-based solidifying material. Is added to secure strength. The former method has a drawback that it is difficult to mix it with a solidifying material because the treated soil after dehydration treatment has an insufficient strength but is difficult to obtain uniform improved soil. On the other hand, in the latter method of adding mechanical dewatering treatment to a material to which a solidifying material has been added in advance, not only the solidifying strength is improved, but also uniform mixing is possible, so that homogeneous improved soil can be obtained. Become. Further, since the initial dehydration rate is higher than that in the case of using a commonly used inorganic or organic flocculant, there is also an advantage that the dehydration treatment becomes easy. However, it is possible to avoid a decrease in the dehydration rate due to repeated treatment due to the clogging of the filter caused by the product formed by the hydration reaction of the solidified material particles that have entered the filter eye and the precipitate formed by the elution alkaline component being carbonated on the filter surface. Not only that, but due to the action of the alkaline component contained in the added solidifying material, the organic matter contained in the dredged bottom mud and various sludges is eluted into the liquid phase, which has the drawback of incurring additional costs for the treatment. There is. In addition, when the treatment target is dredged soil, it is generally performed to return it to the original water area because there is not enough disposal site for the dehydrated cake after the treatment. Elution of organic matter may be a problem. Therefore, it has been desired to solve the above problems associated with the dehydration method in which the solidifying material is added in advance, and make it truly practical.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reduce the dehydration rate due to filter clogging during repeated treatments and to suppress the elution of organic substances into the post-treatment liquid, and to suppress the elution of organic substances. It is an object of the present invention to provide a method for dehydrating and solidifying a highly water-containing slurry that gives a dehydrated cake of high strength.

[0005]

The present invention has achieved the above object by providing the following dehydration and solidification method for a high water content slurry. The high water content slurry is divided into two, and one slurry is a mixture of one or more selected from activated carbon, incinerator ash containing carbon and uncombusted carbon, and aluminum sulfate, polyaluminum chloride, sodium aluminate. And a treatment material comprising one or a mixture of two or more selected from sodium silicate to prepare an A mud slurry having a pH of 5.8 to 8.5,
The other slurry contains limes, Portland cement,
A mixture of one or more kinds selected from alumina cement and blast furnace slag, or a treating material in which gypsum is further mixed is added to prepare a B mud slurry, and first, the A mud slurry is dehydrated. A method for dehydrating and solidifying a highly water-containing slurry, which comprises performing the dehydration treatment of the slurry of B mud, and then performing the dehydration treatment of the slurry of B mud through the dehydrated cake of A mud.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The dewatering and solidifying method for a highly hydrous slurry of the present invention will be described in detail below. According to the present invention, a high water content slurry which is a mud to be dehydrated is separated into two, and one of the treated materials of different types is added to one of the separated slurry to obtain an A mud slurry. One is added to the other slurry to form a B mud slurry, and the A mud dewatering cake obtained by the dewatering treatment of the A mud slurry is used in combination with the original filter as a filter medium constituent part in the dewatering treatment of the B mud slurry. In this way, fine particles of cement or lime in the B mud slurry are captured to prevent the filter from being clogged by the fine particles and to increase the strength of the B mud dehydrated cake obtained by the dehydration treatment of the B mud slurry. Neutralize and adsorb the alkali eluted from the solidifying material added to the mud slurry and the organic substances eluted from the high water content slurry that is the mud to be dehydrated by the action of the alkali. While preventing carbonation of a filter surface of the alkaline component, the pH and organic matter of the processed liquid, in which additional processing is to permit maintenance to unwanted proper value.

In the present invention, not only one dehydration cycle of the A mud slurry and B mud slurry but also a plurality of dehydration cycles can be constituted. Also, the ratio of the A-mud slurry to the B-mud slurry is set to 1: 9 to 5: 5, preferably 2: 8 to 4: 6 (weight basis) in terms of starting soil, to obtain good results. be able to.
Here, “starting soil conversion” means conversion into high water content slurries which are A and B mud slurries at the time of collecting high water content slurry. When the proportion of the A mud slurry is lower than 10%, the absolute amount of acidic substances such as clay minerals contained in the A mud slurry is reduced, and the ability to neutralize the dissolved alkaline in the B mud slurry is reduced. Depending on the characteristics of the mud to be treated, additional alkali neutralizer may be required. In addition, the ratio of the A mud slurry is 5
If it is more than 100%, it is necessary to increase the amount of the additive material in order to secure the dehydration rate of the A mud slurry, and since the proportion of the B mud slurry becomes relatively small, the entire dehydrated cake after treatment The solidification strength may decrease.

One or a mixture of two or more kinds selected from activated carbon, unburned carbon-containing incinerated ash, and zeolite, which is added to one of the above-mentioned slurries to obtain the A-mud slurry, is used as a dehydration aid for the A-mud slurry itself. Of course, it works as an organic matter adsorbent in the filtrate of the B mud slurry, so it is an important component in the treatment of mud containing a large amount of organic matter. Here, as the activated carbon, for the liquid phase, it is possible to use a granular product or a powdered product which is commercially available for the gas phase,
In particular, powdery products for the liquid phase are preferable because they have a high adsorption effect and give good results. Further, as the unburned carbon-containing incineration ash, pulverized coal boiler ash that uses various coals as fuel, fluidized bed boiler ash, papermaking sludge incineration ash, and the like can be used. In particular, 5% by weight or more of unburned carbon is contained. Is desirable. Further, as the zeolite, any of synthetic products having various pore shapes, natural products in the form of powder and particles can be used.

Similarly, one or a mixture of two or more selected from aluminum sulfate, polyaluminum chloride, sodium aluminate and sodium silicate, which is added to the above one slurry to obtain the A mud slurry, is agglomeration of the A mud slurry. At the same time as functioning as a material, the hydrolysis product has a pH adjusting function that also functions as an alkali neutralizing material for the filtrate of the B mud slurry. This neutralization mechanism is
Aluminum hydroxide generated in the mud dehydrated cake and the aluminol group (-Al-OH) and silanol group (-Si-OH) on the surface of the silica gel particles react with calcium ions in the filtrate of the B mud slurry to generate hydrogen. It is thought that this is due to the release of ions.
Since clay particles and organic substances in the mud slurry are also contained to some extent, it is considered that an excellent pH adjusting function is exerted by their combined action. Further, due to the pH decrease due to the neutralization, a part of the organic matter eluted from the B mud slurry is precipitated and captured in the A mud dehydrated cake, and the COD of the filtrate of the B mud slurry is collected.
There is also a side effect of decreasing.

Here, as aluminum sulfate, various commercially available products having different alumina contents, for example, alumina 8
Both liquids of 14% by weight and solids of 14% by weight or more can be used. As the polyaluminum chloride, a liquid commercial product having an alumina content of 10 to 11% can be used. As the sodium aluminate, those commercially available as an aqueous solution of various concentrations or a powdery solid can be used. As the sodium silicate, liquid products that are commercially available as various types of water glass, as well as powders of single anhydrous salts such as sodium orthosilicate and sodium metasilicate, and hydrates can be used.

These treatment materials functioning as an aggregating agent for the A mud slurry can be added individually or as a mixture in the form of a liquid or powdery solid, and their hydrolysis products, aluminum hydroxide and silica gel. With respect to the above, it is desirable to form the slurry in the A mud slurry from the viewpoints of improving the dehydration rate, uniformity of mixing, and activation of the particle surface.

The pH of the A mud slurry is 5.8 to 8.5,
It is necessary to adjust it to preferably 6.0 to 7.5. When the pH of the A mud slurry deviates from the range of 5.8 to 8.5, A
Not only is it necessary to neutralize the filtrate after dewatering the mud slurry, but the acid- and alkali-soluble components contained in the A-mud slurry before the addition of the treatment material are eluted, and the COD of the filtrate is
As a result of not only causing rise and coloration but also being competitively adsorbed at the adsorption point of the organic adsorbent in the treated material,
This leads to a decrease in the effect of adsorbing and removing organic substances in the B mud slurry during the dehydration treatment of the B mud slurry.

To adjust the pH of the A mud slurry, firstly, different kinds of aggregating agents having different pH values, that is, aluminum sulfate and polyaluminum chloride, which are acidic substances, are used.
Alkali substances such as sodium silicate and sodium aluminate are used individually or in combination, but if necessary, various acids or alkalis such as sulfuric acid, hydrochloric acid, slaked lime, quick lime, caustic soda are used. It can also be added as a regulator.

A obtained by dehydration treatment of A mud slurry
The mud dewatering cake is used as a filter material and an adsorbent for the B mud slurry. For this reason, it is desirable that the A-mud dehydrated cake have excellent filtration characteristics and adsorption characteristics. There is a close relationship between the alkali neutralizing ability of the A-mud dehydrated cake and the organic matter adsorption ability. For example, the alkali-neutralizing ability of the A-mud dehydrated cake is saturated and the amount of alkali eluted in the B-mud slurry can be treated. When it disappears, even if there is a sufficient excess amount of the organic matter adsorbent under the condition that the alkali neutralizing ability is not saturated, the organic matter treating ability of the A mud dehydration cake is significantly reduced, and as a result, the B mud slurry dehydration treatment is performed. COD of later filtrate
This leads to an increase in the temperature, which is not desirable.

In the present invention, the pH and COD of the filtrate at the end of the dehydration treatment of the B-mud slurry show environmentally unproblematic values, and the filtration rate of the A-mud slurry is the B-mud slurry carried out through the A-mud dehydrated cake. Since it is possible to obtain preferable results by setting the treating material to be added to the A mud slurry so as to be higher than the dehydration rate of
The type and amount of the treatment material added to the A mud slurry is preferably adjusted appropriately according to the characteristics and properties of the mud to be dehydrated, and the type and amount of the treatment material added to the B mud slurry selected accordingly. There are various substances with different chemical species, morphology, water content, etc. that can be used as treatment materials, and the addition amount naturally changes accordingly, but in general dredged soil, the above A mud slurry is used. 1 to 8 parts by weight of aluminum sulfate and / or polyaluminum chloride (as alumina), 2 to 40 parts by weight of sodium aluminate and / or sodium silicate (as solid), activated carbon and unburned carbon Treated material containing 1.5 to 80 parts by weight of incinerated ash and / or zeolite, in terms of solid,
It is preferable to add 100 to 800 kg per 1 t of dry soil of the slurry to obtain an A mud slurry, since an A mud dehydrated cake having excellent filtration characteristics and adsorption characteristics can be obtained.

On the other hand, one or a mixture of two or more kinds selected from limes, Portland cement, alumina cement and blast furnace slag added to the other slurry to obtain the B mud slurry, or further gypsum. The mixed treatment material has a solidifying action or an aggregating action, and is added as a single component or a plurality of components depending on the characteristics of the B mud slurry. By adding the treatment material, the strength of the dehydrated cake after the dehydration treatment and the filtration rate of the B mud slurry can be increased. Here, as limes, quick lime,
Any of decalcified products of slaked lime and dolomite and digested products thereof can be used, and those having a particle size of 100 mesh or less are particularly preferable in terms of the effect of increasing the processing speed. Further, as the Portland cement, commercially available products such as normal, early strength, moderate heat, and low heat cement can be used, and among them, early strength cement is preferable from the viewpoint of increasing filtration rate and solidification strength. Also,
Alumina cement is a cement containing calcium aluminate as a main component, and one having a property of imparting early strength by selecting an appropriate hardening accelerator and a property of low alkali elution is used. As the blast furnace slag, crushed iron-making water granulated slag is used. Further, as the gypsum, any of anhydrous, semi-water and dihydrate gypsum can be used.

The B-mud slurry containing these treatment materials is agitated and mixed. At that time, since the solidification reaction of the treatment material proceeds, the dehydration rate, for example, the filtration rate in the case where the filtration method is adopted, increases with stirring and mixing time. The amount of the organic substances dissolved in the liquid phase may increase. Therefore, the stirring and mixing time after the addition of the treatment material is set to an appropriate value empirically depending on the properties of the mud to be dehydrated, but it is usually in the range of 1 to 10 minutes.

In the treatment material added to obtain the B mud slurry, limes mainly affect the dehydration rate, and cement and gypsum are components that affect the solidification strength of the dehydrated cake. In order to obtain a dehydrated cake with sufficient and not too high strength at a sufficient dehydration treatment speed, depending on the characteristics of the mud to be dehydrated, the mixing ratio of hydraulic components, the type and composition of adsorbent, and the addition of treatment Although the amount will be appropriately selected, in general dredged soil, 30-60 parts by weight of limes, Portland cement and / or alumina cement 30-is added to the slurry of the B mud slurry.
It is preferable to add 50 to 300 kg of a treating material composed of 70 parts by weight and 5 to 30 parts by weight of gypsum per 1 t of dry soil of the slurry because good results can be obtained.

The mechanical dewatering device usable in the practice of the present invention is capable of dewatering the B mud slurry through the A mud dewatering cake and removing the B mud dewatering cake and the A mud dewatering cake as peeling bodies. It needs to be possible. Further, as a method for dehydration treatment, either a filtration method or a centrifugal separation method can be used, and in particular, a filtration method, particularly a filtration method using a filter press, is easy to operate, has a treatment effect, a treatment speed and a treatment cost in every aspect. Is the most preferred method.

When a filter press is used for the dehydration treatment, the A-mud slurry having a volume of 1.5 times or more of the filter chamber volume is put into the dehydration treatment, and then the B-mud slurry is put inside the produced A-mud dehydrated cake. By incorporating it, not only the entire surface of the filter medium can be covered with the A mud dehydrated cake, but also a dehydrated cake having a sufficient thickness for filtering the B mud slurry can be obtained. Further, the structure in which the B mud dehydrated cake is wrapped in the A mud dehydrated cake also has an effect of suppressing the elution of organic substances from the dehydrated cake after the dehydration treatment.

Depending on the fractionation ratio and the water content ratio of the high water content slurry which is the target soil for dehydration treatment, the A mud slurry capacity may be less than 1.5 times the filter chamber volume of the filter press. In this case, dehydration can be carried out after adding water to make up for the deficiency.

The hydrated A-mud slurry may cause turbidity in the filtrate at the start of filtration. In this case, in the subsequent dehydration cycle, the filtrate having a lot of turbidity can be used as water for adding water to the A-mud slurry and the dehydration process can be performed again to make the discharged filtrate clean. .

One feature of the dewatering and solidifying method of the present invention is that clogging of the filter medium is greatly suppressed by the effect of the A-mud dewatering cake, and the processing speed does not decrease when the filter medium is repeatedly used.

When a filter press is used, switching between the A mud slurry and the B mud slurry fed into the filter press is usually performed before the pressurizing pump. Upon completion, in the next dehydration cycle, the B mud slurry remaining in the line after the switching valve will be dehydrated first, which may lead to clogging of the filter medium and an increase in the filtrate COD. In such a case, the A mud slurry is separated into A ₁ mud slurry and A ₂ mud slurry, first the A ₁ mud slurry is dehydrated, and then the B mud slurry is injected.
After dehydration treatment of the B mud slurry through A ₁ mud dehydrated cake, further driving the A ₂ mud slurry, subjected to dehydration treatment of the A ₂ mud slurry through A ₁ mud dewatered cake and B mud dehydrated cake, the A _1, B It can be avoided by performing dehydration treatment of the A ₂ mud slurry using a filter press. In particular, it is preferable to drive the A ₂ mud slurry in an amount equal to or larger than the line volume from the switching valve to the filter press after the B mud slurry.

According to the method of the present invention, a high-strength dehydrated cake having a structure in which the B-mud dehydrated cake is wrapped with the A-mud dehydrated cake is obtained, which is a problem when the dehydrated cake is reused, particularly when it is reduced to water. It is possible to reduce the elution amount of alkalis and organic substances that tend to become. In this case, the degree of crushing when the dehydrated cake is reduced into water, that is, the degree of exposure of the surface of the dehydrated cake affects the elution amount, so it is desirable to put the dehydrated cake in water in a shape as large as possible. However, depending on the situation of the construction site, crushing of the dehydrated cake may progress, and elution of alkali or organic matter from the B mud dehydrated cake may become a problem. In such a case, it is also possible to suppress elution by covering the interface between the dehydrated cake and the surrounding environment with sand or soil, which is a measure for preventing elution that is usually performed, but the dehydration solidification of the present invention In the construction method, it can be carried out by neutralizing the alkali in the B mud dehydrated cake that causes elution.

A specific method thereof is a method of adding an acid to the A ₂ mud slurry at the time of driving the A ₂ mud slurry at the time of performing the dehydration treatment of the A ₁ , B and A ₂ mud slurry described above. A more preferable result can be obtained by adjusting the volume of each of the A ₁ and A ₂ mud slurry and the addition amount of the acids so that the A ₂ mud slurry to which the acids have been added is completely spread over the B mud dehydrated cake. . By the way, in order to neutralize the alkali in the B mud dehydration cake, B before dehydration treatment
The method of directly adding the acids to the mud slurry may destroy the agglomerate structure, resulting in an extremely low dehydration rate. On the other hand, in the above method, since the neutralization treatment is performed in a state where the aggregated particles in the dehydrated cake are in contact with each other and stabilized, it is considered that the aggregation structure is less likely to be broken and the influence on the filtration rate is small. In this case, the dewatering rate of the B mud slurry is naturally not affected at all.

Acids used for neutralization include carbon dioxide gas,
Examples thereof include inorganic acids such as hydrochloric acid and sulfuric acid, and acidic metal salts such as aluminum sulfate, polyaluminum chloride and iron chloride.
The use of sulfuric acid and carbon dioxide is preferable in terms of cost. This neutralization treatment generally reduces the strength of the B mud dehydrated cake, but in the case of carbon dioxide gas, the degree of reduction is the smallest, and is a particularly preferable material. The concentration and amount of the acids to be added will be determined in consideration of the amount of alkali contained in the B mud slurry, the properties of the dehydrated cake, and the handling safety, but use as little concentration as possible. Preferably.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is in no way limited by these examples. In addition, "%" means "% by weight" unless otherwise specified. (1) Dehydration target mud The characteristics of the high-water-content slurries (lake dredged soils I and II) used in the examples and comparative examples as the dehydration target mud are shown in Table 1 below.
Shown in.

[0029]

[Table 1]

(2) Treatment Material The materials of the treatment materials used in Examples and Comparative Examples are as follows. Aluminum sulphate: Alumina 17% powdered commercial product, Asada Chemical Co., Ltd. Sodium aluminate: Alumina 56% powdered commercial product, Sumitomo Chemical Co., Ltd. Sodium silicate: Liquid commercial product, Central Glass Co., Ltd. ,
Water glass No. 3 polyaluminum chloride: 10% alumina content aqueous solution, Asada Chemical Co., Ltd. Zeolite: Commercial natural zeolite, 0.6 mm under product, Akita activated carbon: Waste water treatment powder, Nimura Chemical Co., Ltd. Coal ash: Pulverized coal boiler containing 8% unburned carbon Boil ash Slaked lime: Commercial product with particle size of 200 mesh or less, manufactured by Ube Materials Co., Ltd. Special issue S Quick lime: Commercial product with particle size of 100 mesh or less, Ube Materials Co., Ltd. Made of high strength cement: Commercial product, Ube Industries, Ltd. Alumina cement: Commercial product, Asahi Glass Co., Ltd., No. 1 blast furnace slag: Commercial product, Kawasaki Steel Co., Ltd., Revertment anhydrous gypsum: Commercial Natural anhydrous gypsum, from Thailand In addition, in the following examples, the A mud treatment material is the treatment material added to obtain the A mud slurry, and the B mud treatment material is
B: A treatment material added to obtain a mud slurry.

Examples 1 to 11 and Comparative Examples 1 to 7 Lake dredged soil I (high water content slurry) was used as a mud to be dehydrated, and a pressure Nutschie type filter was used as a dehydrator to examine the filtration characteristics. The lake dredged soil I (500 ml) was divided into two portions, and a treatment material was added to each of them to perform dehydration treatment. Preparative ratio (ratio of high water content slurry made into A mud slurry without addition of treatment material and high water content slurry made into B mud slurry without addition of treatment material, hereinafter referred to as "A / B ratio"), treatment material type and treatment The conditions are shown in Tables 2 and 3 below. The A and B mud slurries after the addition of the treating material were subjected to a pressure dehydration treatment at a pressure of 6 kgf / cm2 using a pressure nutche type filter manufactured by Shoei Kagaku Co., Ltd. First, the A mud slurry was filtered, and immediately before the shrinkage cracks were formed in the dehydrated cake, the B mud slurry was cast on the A mud dehydrated cake to filter the B mud slurry.

The following measurements were carried out to evaluate the effect of dehydration treatment. The time required to obtain 300 ml of the filtrate (excluding the switching time from the A mud slurry to the B mud slurry) was measured and used as the filtration time. The strength of the B mud dewatering cake was 2 mm after the obtained dewatering cake was cured in the wet air for 7 days and a 3 mm diameter needle was penetrated into the dewatering cake at a speed of 1 mm / min.
It was calculated by converting the resistance value at the time of penetration into uniaxial compressive strength. The filtrate pH and COD are respectively JIS-K-0102 1
2.1 and JIS-K-010217 were measured. Further, the properties (coloring, turbidity) were visually observed. The results are shown in Tables 2 and 3 below. In Tables 2 and 3, "B mud strength" means the strength of the B mud dehydrated cake.

[0033]

[Table 2]

[0034]

[Table 3]

As shown in each of the examples in Table 2, the high water content slurry which is the mud to be dehydrated is divided into two, and the treatment material according to the present invention is added to each of them to obtain an A mud slurry and a B mud slurry. By first performing the dehydration treatment in the order of the A mud slurry and then the B mud slurry, a dehydrated cake having high strength can be obtained in a short time. The filtrate has a pH close to neutral and low COD.
It showed a value, was colorless and transparent, and did not require any additional treatment. On the other hand, as shown in Table 3, in the case of dehydration treatment without fractionation, in addition to the filtrate being colored, at least one of filtration time, dehydration cake strength, filtrate pH, and COD was used. Does not reach a satisfactory value.

Example 12 and Comparative Examples 8 and 9 Here, filtration dehydration is repeated without replacing the filter cloth, and it is shown that the dehydration solidification method of the present invention is effective in suppressing clogging of filter media. At the end of each filtration cycle, while removing the produced dehydrated cake, the A mud slurry → B mud slurry filtration cycle was repeated in the same manner as in Examples 1 to 11,
The time required for filtration was measured. The results are shown in Table 4 below. In the dehydration solidification method of the present invention, it is understood that the initial dehydration rate is high, and the decrease in speed is slight even after repeated filtration, and clogging of the filter medium is significantly suppressed.

[0037]

[Table 4]

Examples 13 to 16 Here, the mud to be dehydrated was replaced with the lake dredged soil II shown in Table 1, and the dehydration was carried out by a small filter press (filter chamber shape: length 60 cm × width 60 cm) manufactured by Rasa Industry Co., Ltd. × Thickness 3c
The example performed using m) is shown. The processing steps are shown in FIG. In FIG. 1, the high water content slurry which is the dewatering target mud in the raw mud storage tank 1 is sent to the mixing tanks 4A and 4B by the transfer pump 2. At this time, the valves 3A, 3B
It is possible to switch the transfer slurry by switching. Further, a water addition line 6 is provided in the mixing tank 4A, so that the volume can be increased by water addition when the slurry volume is less than 1.5 times the filter chamber volume. The high water content slurry sent to the mixing tanks 4A and 4B is mixed and stirred with the processing materials sent from the processing material tanks 5A and 5B, respectively, and then sent to the filter press 10 through the driving pump 9 and 6 kgf / It is dehydrated at a pressure of cm ² . Also here, by switching the valves 7A and 7B, the A mud slurry and the B mud slurry fed into the filter press can be switched. The filtrate from the filter press is discharged through the filtrate tank 11.
In the figure, 8 is an acid tank, 12 is a stirrer, and 13 is a water tank. Dehydration was terminated when the filtrate discharge rate per filtration chamber was 0.1 liter / min or less, and the filtrate was measured for pH, COD, and properties in the same manner as in Examples 1 to 12, and dehydrated. The properties of the cake were examined by the following methods.

First, the thickness of the A-mud layer (precoat layer) in a plate-shaped dehydrated cake having substantially the same shape and size as the filter chamber was measured in the peripheral portion and the central portion around the liquid delivery port.
Then, 5 cm in diameter from the dehydrated cake that had been cured in the wet air for 7 days.
The cylindrical block of was cut out in the thickness direction to be stacked at a height of 10 cm to prepare a test piece, and a uniaxial compression test was performed by a method based on JIS-A-1216. In addition, 5 cm long × 5 cm wide × height 3.
A 3 cm block was placed in a 1 liter container in three steps with spacers so that each surface was exposed, immersed in distilled water, sealed and allowed to stand for 7 days, then the pH of the aqueous phase and CO
D was measured and the dissolution test from the dehydrated cake was performed.

The processing conditions and measurement results are shown in Table 5 below.
Filtration time (dehydration time), filtrate properties, dehydrated cake strength,
Elution amount from cake (elution COD)
It can be seen that the dehydration solidification method of the present invention gives satisfactory results.

[0041]

[Table 5]

[0042] Example 17-22 In this example, fractionating A mud slurry A ₁ mud slurry and A ₂ mud slurry, subjected to dehydration treatment of A ₂ mud slurry after dehydration treatment of A ₁ and B mud slurry, B mud An example of neutralizing the dehydrated cake is shown. The lake dredged soil II was separated into two, and the treating material was added to each to obtain the A mud slurry and the B mud slurry. The A mud slurry was further separated into two kinds of A ₁ and A ₂ mud slurries. After successively with dehydration treatment of A ₁ mud slurry → B mud slurry, the A ₂ mud slurry implantation, it was subjected to dehydration treatment, and a part of the driving start of the A ₂ mud slurry acids from Sanso 8 Except that it was added
It carried out by the same method as Examples 13-16. In addition, the addition of acids is performed by supplying an aqueous solution having a concentration of 2 to 10 mol / liter except carbon dioxide, and carbon dioxide is supplied from a cylinder at 7 kgf.
It was carried out by blowing gas at a pressure of / cm 2 for 10 minutes. The pH and COD of the filtrate, the strength of the dehydrated cake, and the dissolved organic matter (eluted COD) from the cake were measured in the same manner as in Examples 13 to 16. The processing conditions and the results obtained are shown in Table 6 below.

[0043]

[Table 6]

From the results of Table 6, according to the method of separating the A-mud slurry into two and adding the acid, the dehydration rate and the strength of the dehydrated cake are not significantly lowered, and the characteristics of the filtrate are
It can be seen that the amount of organic matter eluted from the dehydrated cake can be further reduced without affecting the properties.

[0045]

EFFECTS OF THE INVENTION The dehydrated cake obtained by the dehydration and solidification method of the present invention has a high solidification strength and a low organic matter elution amount, and therefore can be effectively used for embankment and backfilling.
In addition, there is no problem in the pH, COD, and properties of the treated water generated by dehydration, and the treated water can be discharged without additional treatment. Further, the dehydration and solidification method of the present invention uses an inexpensive material such as cement or lime as the main treatment material, and also has a large dewatering rate and excellent processing ability, so that the processing cost is also low. Have. That is, the present invention provides a method for dehydration and solidification of a highly water-containing slurry, which is excellent in performance and cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a flow when a dehydration process is performed using a filter press.

[Explanation of symbols] 1 raw mud storage tank 2 Transfer pump 3A, 3B flow path switching valve 4A, 4B mixing tank 5A, 5B processing material tank 6 water line 7A, 7B flow path switching valve 8 acid tank 9 Driving pump 10 Filter press 11 Filtrate tank 12 stirrer 13 aquarium

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihito Mori 1-1-13 Yamashita, Okayama City, Okayama Prefecture Incorporated in Omotogumi Co., Ltd. (72) Yukio Tasaka 1-12 Nishihonmachi, Ube City, Yamaguchi Prefecture No. 32 Ube Kosan Co., Ltd. Ube Head Office (72) Inventor Osamu Yoneda 1-12-12 Nishimotomachi, Ube City, Yamaguchi Prefecture Ube Kosan Co., Ltd. Ube Head Office (72) Inventor Shigeo Okabayashi Nishimoto Town, Ube City, Yamaguchi Prefecture 1-12-32 Ube Industries, Ltd. Ube Head Office (56) Reference JP-A-55-145512 (JP, A) JP-A-10-76298 (JP, A) JP-A-6-114209 (JP, 114-209) A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 11/00-11/20

Claims (7)

(57) [Claims] 1. A high-water-content slurry is divided into two, and one slurry contains one or a mixture of two or more kinds selected from activated carbon, incinerated carbon-containing incinerated ash and zeolite, and aluminum sulfate and polychlorination. aluminum,
By adding a treatment material consisting of one or a mixture of two or more selected from sodium aluminate and sodium silicate,
An A mud slurry having a pH of 5.8 to 8.5 was prepared, and the other slurry contained limes, Portland cement,
A mixture of one or more kinds selected from alumina cement and blast furnace slag, or a treating material in which gypsum is further mixed is added to prepare a B mud slurry, and first, the A mud slurry is dehydrated. Then, pour the B mud slurry and pass through the A mud dewatering cake.
A method for dehydrating and solidifying a high-water-content slurry, which comprises dehydrating mud slurry. 2. The method for dehydration solidification of a highly water-containing slurry according to claim 1, wherein the ratio of the A-mud slurry to the B-mud slurry is 1: 9 to 5: 5 (weight basis) in terms of starting soil. 3. When preparing the A-mud slurry, aluminum sulfate and / or polyaluminum chloride 1-8
1 part by weight (converted to alumina), 2 to 40 parts by weight of sodium aluminate and / or sodium silicate (converted to solid), activated carbon, unburned carbon-containing incinerated ash and / or zeolite 1.
The dehydration solidification method for a high water content slurry according to claim 1 or 2, wherein 100 to 800 kg of a treating material composed of 5 to 80 parts by weight is added per 1 t of dry soil of the slurry in terms of solid. 4. When preparing the B mud slurry, 30 to 60 parts by weight of limes, 30 to 70 parts by weight of Portland cement and / or alumina cement, 5 to gypsum.
The dehydration solidification method for a high water content slurry according to any one of claims 1 to 3, wherein 50 to 300 kg of a treatment material composed of 30 parts by weight is added per 1 t of dry soil of the slurry. 5. The method for dehydrating and solidifying a high water content slurry according to claim 1, wherein the dehydration treatment is performed using a filter press. 6. fractionating the A mud slurry A ₁ mud slurry and A ₂ mud slurry, is performed first dehydration treatment of A ₁ mud slurry, then implanted B mud slurry, said through A ₁ mud dehydrated cake B After dewatering mud slurry, A ₂
A method of dewatering the A ₂ mud slurry through the injection of mud slurry, the A ₁ mud dewatering cake and the B mud dewatering cake, and the dewatering of the A ₁ , B and A ₂ mud slurry using a filter press. The method for dehydrating and solidifying a high water content slurry according to 1. 7. A time of driving of the A ₂ mud slurry, adding acid to the A ₂ mud slurry, dewatering solidification method of high water slurry of claim 6 wherein.