JP2005305297A - Insolubilization and solidification system for heavy metal polluted soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insolubilization and solidification system for heavy metal polluted soil capable of excellently treating sludge having proper moisture, thereby satisfactorily insolubilizing heavy metals and efficiently performing the the insolubilization and solidification treatment of the heavy metal polluted soil. <P>SOLUTION: Fine particles which are adjusted into a water content suitable for granulation, contain the heavy metals and have grain sizes after washing/classification processing less than 0.5 mm and a soidifying material are quantitatively supplied to a continuous mixing granulator 11 by using a quantitative sludge supplier 7 and a quantitative solidification material supplier 8, respectively, and primary granulated material is manufactured. The primary granulated material and an insolubilizing material are supplied to a continuous agitation granulator 13 through the continuous mixing granulator 11 and a quantitative insolubilizing material supplier 15, respectively, and the primary granulated material is mixed, granulated and compacted to manufacture secondary granulated material. The surface of the secondary granulated material is coated with the insolubilizing material and the secondary granulated material is continuously discharged from the upper part of an agitation tank 13a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a system for insolubilizing and solidifying heavy metal-contaminated soil in which heavy metals are contained so as not to elute from incinerated ash, sludge, soil, sediment, stone powder, and regenerated powder to which heavy metals such as lead, arsenic, mercury, and cadmium are attached.

The following are known as this type of system.
A. First conventional example (see Patent Document 1)
The generated soil such as construction sludge generated in construction engineering works and construction sludge with high water content generated in excavation work is dehydrated with a dehydrator to the desired moisture content, and the dehydrated generated soil is absorbed by water. An agent and a solidifying agent are added, mixed by stirring and gelled, and then the internal substance is divided and granulated to produce stable quality granules.

B. Second conventional example (see Patent Document 2)
A solidifying agent is added to the high-moisture generated soil such as construction sludge during tunnel excavation work and dredged soil during dredging work, and a water-absorbing agent is added and stirred and mixed with a stirrer to dissolve the mixed soil. The material is supplied to a crushing and granulating machine, and the internal material of the generated soil is divided and granulated to generate a granular material.

C. Third conventional example (see Patent Document 3)
After precipitating dust generated from each steelworks such as a sintering furnace, blast furnace, electric furnace, converter, etc., the precipitate is dehydrated to obtain a filter cake having a moisture content of about 25 to 35%. In addition, quick lime powder and dry dust are mixed and agglomerated, and after sieving, the coarse particles are pulverized again, and the sieve is sent to a granulator for granulation treatment.

D. Fourth conventional example (see Patent Document 4)
The sludge generated from the water purification plant, the sludge accumulated in rivers, lakes, etc. is dewatered and crushed to a particle size of 5 mm or less, and the crushed material is granulated into a granular pellet by a stirring granulator, The pellets are dried to a moisture content of about 10% or less, and the dried pellets are fired at a firing temperature of about 800 to 1100 ° C.

E. Fifth conventional example (see Patent Document 5)
Cement and water glass solution are added to the raw material of industrial waste consisting of powder or mud and stirred to form a mud, and the mixture is rolled to form a large number of granules. Furthermore, after spraying a water glass solution on the granular material to coat the surface of the granular material, the granular material is dried and cured to prevent the toxic substances from eluting.

F. Sixth conventional example (see Patent Document 6)
Industrial waste is treated with a treating agent comprising a combination of an alkaline aqueous solution of an alkali metal salt and an acidic or neutral solution of a cobalt amine complex, and the industrial waste is treated within the range of 0.5 to 20 mm in the presence of cement and water. Granulated to a particle size, and the granulated material is covered with mortar to suppress elution of harmful heavy metals.

G. Seventh conventional example (see Patent Document 7)
After granulating the gypsum-based waste material to an appropriate particle size (in the case of coarse aggregate, particle size of 25 mm or less), the surface is made of cement-based material consisting of cement raw material and water. It is coated and carbonized by exposing to carbon dioxide under heat and pressure to obtain a waste gypsum-based aggregate on which a hard coating film with suppressed elution of the calcium sulfate component is formed.

H. Eighth conventional example (see Patent Document 8)
The soil contaminated with lead, hexavalent chromium, arsenic, selenium, etc., which is difficult to treat with cement, etc. is made muddy, and the specified water and magnesium oxide or magnesium oxide added with an acid solidification aid are added and solidified. It prevents elution of heavy metals into nearby soil.
JP 2003-126826 A Japanese Patent Laid-Open No. 11-343633 Japanese Patent Publication No.63-31276 Japanese Patent No. 2620742 Japanese Patent Laid-Open No. 11-333423 Japanese Patent Application Laid-Open No. 08-057443 JP 2001-097750 A JP 2002-206090 A

  However, in the case of the first to fourth conventional examples as described above, there is a drawback that elution cannot be prevented when the processed material contains heavy metal.

  In the case of the fifth to seventh conventional examples as described above, in any case, after forming a granular body with cement or water glass, it is coated with cement or water glass, or is carbonated under heating and pressure, The suppression of elution of heavy metals is achieved by physical containment, and the effect is still insufficient.

  In addition, the granulated product thus produced has a wide particle size distribution, and there is a drawback that reliability is lowered when heavy metals and the like are contained in coarse particles and fine particles.

  Further, in the case of the eighth conventional example, in the case of using magnesium oxide, the mixing accuracy between the soil and the treatment agent is not sufficient, and it is difficult to obtain high solidification strength, the insolubilizing effect of heavy metals and the long-term stability thereof. There was a problem in securing.

  This invention is made | formed in view of such a situation, and while the invention which concerns on Claim 1 treats the sludge which has a suitable water | moisture content well, and contains heavy metal well, those heavy metal contaminated soil The purpose of the invention according to claim 2 is to enable easy handling even when the amount of water is less than the appropriate amount of water. An object of the present invention is to satisfactorily contain heavy metals by properly treating sludge having a moisture content higher than an appropriate amount of moisture, and to efficiently insolubilize and solidify those heavy metal-contaminated soils.

The insolubilization / solidification system for heavy metal-contaminated soil of the invention according to claim 1 is provided in order to achieve the above-described object.
Sludge supply means for quantitatively supplying fine particles (hereinafter referred to as sludge) having a particle size of less than 0.5 mm after washing and classifying treatment containing heavy metal;
A solidifying material supply means for quantitatively supplying the solidifying material;
The sludge supplied quantitatively from the sludge supply means is received via the first transfer means, and the solidified material fixedly supplied from the solidification material supply means is received via the second transfer means to sludge and solidify. A continuous mixing granulator that continuously mixes and granulates the material to produce a primary granulated product,
An insolubilizing material supply means for quantitatively supplying the insolubilizing material;
The primary granulated product from the continuous mixing granulator is received through the third transfer means and the insolubilized material from the insolubilized material supply means is received through the fourth transfer means to mix the primary granulated product. A secondary agglomerated product is produced by granulation and compaction, and the surface of the secondary granulated product is coated with an insolubilizing material and continuously stirred and granulated.

(Action / Effect)
According to the structure of the insolubilization / solidification system of the heavy metal contaminated soil according to the first aspect, the sludge is supplied to the sludge supply means, the solidification material is supplied to the solidification material supply means, and the insolubilization material is supplied to the insolubilization material supply means. The primary granulated material is produced by mixing and granulating sludge and solidified material, the secondary granulated material is produced by mixing and granulating and compacting the primary granulated material, and the insolubilized material. The surface of the next granulated product can be continuously coated.

  Therefore, since sludge having appropriate moisture is mixed with the solidifying material, granulated and compacted before coating, the sludge can be treated well to contain heavy metals well.

  In addition, since the sludge is consolidated, the volume can be reduced and handling can be facilitated, and elution of heavy metals can be prevented in a high strength state and can be reused.

  In addition, since a series of treatments can be performed continuously, insolubilization and solidification treatment of heavy metal contaminated soil can be performed efficiently.

In order to achieve the above-described object, the invention according to claim 2
In the insolubilization / solidification system of heavy metal contaminated soil according to claim 1,
A continuous mixing granulator is provided with a spray nozzle for supplying appropriate moisture to the sludge.

(Action / Effect)
According to the structure of the insolubilization / solidification system for heavy metal contaminated soil of the invention according to claim 2, when the moisture contained in the sludge to be treated is small, for example, in the case of crushed stone sludge, the moisture content is 10 to 25 wt%, preferably Appropriate moisture can be supplied from the spray nozzle so as to obtain an appropriate amount of moisture, such as 15 to 20 wt%.

  Therefore, even when the amount of water is less than the appropriate amount, it can be easily dealt with by replenishing water and granulation can be performed effectively.

In order to achieve the above-described object, the invention according to claim 3
A mixing pulverizer that mixes and pulverizes fine particles (hereinafter referred to as sludge) having a particle diameter of less than 0.5 mm after washing and classifying treatment containing heavy metals and dry powder;
A solidifying material supply means for quantitatively supplying the solidifying material;
The sludge supplied quantitatively from the mixing crusher is received via the first transfer means, and the solidified material supplied quantitatively from the solidifying material supply means is received via the second transfer means, and sludge and solidified. A continuous mixing granulator that continuously mixes and granulates the material,
An insolubilizing material supply means for quantitatively supplying the insolubilizing material;
The primary granulated product from the continuous mixing granulator is received through the third transfer means and the insolubilized material from the insolubilized material supply means is received through the fourth transfer means to mix the primary granulated product. A secondary agglomerated product is produced by granulation and compaction, and the surface of the secondary granulated product is coated with an insolubilizing material and continuously stirred and granulated.

(Action / Effect)
According to the structure of the insolubilization / solidification system for heavy metal contaminated soil of the invention according to claim 3, sludge and dry powder are mixed in the mixed pulverizer, the solidification material is in the solidification material supply means, and the insolubilization material is in the insolubilization material supply means. To make primary granulated material by mixing and granulating sludge and solidifying material, mixing and granulating primary granulated material and secondary granulated material by compaction, and insolubilizing material The surface of the secondary granulated product by can be continuously coated.

  Therefore, since sludge having a water content higher than the proper water content is mixed with the solidifying material and granulated and compacted before coating, the sludge can be treated well to contain heavy metals well.

  In addition, since the sludge is consolidated, the volume can be reduced and handling can be facilitated, and elution of heavy metals can be prevented in a high strength state and can be reused.

  In addition, since a series of treatments can be performed continuously, insolubilization and solidification treatment of heavy metal contaminated soil can be performed efficiently.

  According to the heavy metal-contaminated soil insolubilization / solidification system of the first aspect of the present invention, the sludge is supplied to the sludge supply means, the solidification material is supplied to the solidification material supply means, and the insolubilization material is supplied to the insolubilization material supply means. To produce a primary granulated product by mixing and granulating sludge and solidifying material, mixing and granulating the primary granulated product and producing secondary granulated product by compaction, and secondary forming by insolubilizing material. The coating of the surface of the granules can be carried out continuously.

  Therefore, since sludge having appropriate moisture is mixed with the solidifying material, granulated and compacted before coating, the sludge can be treated well to contain heavy metals well.

  In addition, since the sludge is consolidated, the volume can be reduced and handling can be facilitated, and elution of heavy metals can be prevented in a high strength state and can be reused.

  In addition, since a series of treatments can be performed continuously, insolubilization and solidification treatment of heavy metal contaminated soil can be performed efficiently.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall schematic diagram showing an embodiment according to an insolubilization / solidification system for heavy metal-contaminated soil of the present invention. Contaminated soil containing heavy metal is washed with a primary washing machine 1 and washed with a belt conveyor 2. Transport to classifier 3.

  At the conveyance end of the belt conveyor 2, the purified soil having a particle size of 5 mm or more is taken out for reuse. In addition, cleaning wastewater generated in the primary cleaning machine 1 is also supplied to the cleaning / classifying machine 3.

  The cleaning / classifying machine 3 classifies 2 to 5 mm of purified soil and 0.5 to 2 mm of purified soil that have been detoxified by washing and removing harmful substances by washing, and removes them for reuse. The sludge is conveyed to the water treatment device 4.

  In the water treatment device 4, the water after the sludge is settled and separated and the sludge is removed is added with a cleaning aid such as a mineral acid, an organic acid, a surfactant and the belt conveyor 2 portion of the primary cleaning machine 1 and Recycle to washing / classifying machine 3.

  The sludge separated by the water treatment device 4 is dehydrated by the dehydrator 5 and then supplied to the insolubilization / solidification system 6 of the heavy metal contaminated soil. After granulation and solidification treatment and insolubilization treatment, the sludge is reused. Final disposal is planned.

  In the insolubilization / solidification system 6 of heavy metal contaminated soil, as shown in the overall configuration diagram of FIG. 2, the particle size after washing and classification treatment including heavy metal adjusted to moisture suitable for granulation is less than 0.5 mm. A sludge quantitative supply device 7 as a sludge supply means for quantitatively supplying fine particles (hereinafter referred to as sludge), and a solidifying material quantitative supply device 8 as a solidifying material supply means for quantitatively supplying a solidified material. Is provided.

  The first and second hoppers 9 and 10 and the continuous mixing granulator 11 are provided below the sludge fixed amount supply unit 7 and the solidifying material fixed amount supply unit 8, and the sludge fixed amount supply unit 7 is naturally dropped. The sludge supplied in a fixed amount is received through the first hopper 9 and the sludge supplied in a fixed amount by the natural fall from the solidifying material fixed supply device 8 is received through the second hopper 10 to continuously mix and granulate. In the machine 11, the sludge and the solidifying material are continuously mixed and granulated to produce a primary granulated product.

  A third hopper 12 and a continuous agitation granulator 13 are provided below the continuous mixing granulator 11, on the side of the continuous mixing granulator 11 and above the continuous agitation granulator 13. The primary hopper 14 is provided with a fourth hopper 14 and an insolubilizing material quantitative feeder 15 as insolubilizing material supply means for quantitatively supplying the insolubilizing material, and is supplied from the continuous mixing granulator 11 by natural fall. The granular material is received via the third hopper 12 and the insolubilized material quantitatively supplied from the insolubilized material quantitative feeder 15 by natural fall is received via the fourth hopper 14.

  In this continuous stirring granulator 13, the primary granulated material and the insolubilized material are respectively supplied to the position of about 1/3 from the rotation center of the stirring blade 13b in the stirring tank 13a of the continuous stirring granulator 13 for stirring. Based on the correlation between the rotational speed of the blade 13b and the height of the discharge gate (not shown) of the stirring tank 13a, the primary granulated material is mixed, granulated, and compacted to produce a secondary granulated material. The secondary granulated product having a larger particle diameter due to the progress is transferred to the upper part of the stirring tank 13a, the insolubilizing material is added, and the surface of the secondary granulated product is coated with the insolubilizing material and continuously from the upper part of the stirring tank 13a It is constituted so that it may exhaust.

  Although not shown, when the spray nozzle is installed in the continuous mixing granulator 11 and the amount of water contained in the sludge is less than the appropriate moisture, for example, in the case of crushed sludge, the water content ratio is 10 to 25 wt. %, Preferably 15 to 20 wt%, so that granulation can be performed effectively by spraying water as a binding liquid.

  Above the first hopper 9, there is provided a mixing / pulverizing machine 16 that mixes and pulverizes sludge and dry powder and supplies it quantitatively so that it can replace the quantitative mixing machine 7 for sludge. When it is more than the appropriate moisture, the sludge and the dry powder are mixed and pulverized so that the granulation by the continuous mixing granulator 11 can be effectively performed.

  Next, experimental examples will be described.

  Since it was difficult to obtain heavy metal contaminated sludge, we decided to create a simulated contaminated sludge.

That is, by adding an aqueous solution of arsenic (As) adjusted to a predetermined concentration to crushed stone sludge (average particle diameter D ₅₀ = 15.8 μm), and uniformly mixing and dispersing in a high-speed agitation granulator, Contaminated sludge was prepared. Here, Na ₂ HAsO ₄ was adopted as the arsenic reagent. A solidifying material was used as the solidifying material, and a cement system was used as the insolubilizing material (coating material).

  Each experimental condition is as follows.

(1) Simulated contaminated sludge (2) Granulated product of simulated contaminated sludge + solidified material (10 wt%) [batch type]
(3) Granulated product of simulated contaminated sludge + solidified material (10 wt%) [continuous type]
(4) Granulated product of (2) + insolubilized material (10 wt%)
(5) Granulated product of (3) + insolubilized material (10 wt%)
The ratio of the solidifying material added to the simulated contaminated sludge is 10 wt%. The insolubilizing material was 10 wt% with respect to the sludge.

  The elution amount of the contaminated soil was set to about 600 times the environmental standard, and experiments on insolubilization and solidification treatment were conducted by a continuous method and a batch method, and the elution amount was measured according to the Notification No. 46 method. The result is shown in FIG. The amount of elution of arsenic does not meet the environmental standards in the case of the continuous type and batch type in which only the solidifying material is added and mixed [conditions (2), (3)]. The reason why the continuous elution amount is larger than that of the batch type is considered to be due to the short residence time in the vertical continuous mixing granulator 11. However, it can be seen that by applying the coating treatment [conditions (4) and (5)], the elution amount is suppressed to an environmental standard or less. That is, it is clear that the formation of the insolubilized layer works effectively.

  The measurement result of the apparent density is shown in FIG. Here, the larger the apparent density, the heavier (the voids in the granulated particles are smaller). From the results of FIG. 4, it can be seen that the granulated particles subjected to the coating treatment are heavier than the contaminated sludge [conditions (4) and (5)]. That is, the amount is increased by adding a solidifying material and an insolubilizing material for insolubilization and solidification of arsenic, but the volume is reduced by granulation. The volume reduction rate for the contaminated soil was 21%. The volume reduction in this way is due to the shearing / rolling and spheroidization of the continuous stirring granulator 13.

  FIG. 5 shows the result of measuring the particle strength while paying attention to the granulated particles themselves. Since the particle strength was around 1.5 MPa, it was considered that it could be reused as an aggregate for concrete. Furthermore, since the solidified / insolubilized granulated particles are spherical, they are excellent in fluidity and easy to handle. It has been confirmed by a column test or the like that the granulated particles solidified and insolubilized are stable for a long period of time.

  In the above-described embodiment, the system is configured in a bowl shape so that the site area required for installation may be small. However, a horizontal conveyor may be provided for transfer between the processing machines.

  In view of this, a configuration in which sludge is transferred by natural dropping from the sludge quantitative supply device 7 or the mixing / pulverizing device 16 to the first hopper 9 on the continuous mixing granulator 11, and a horizontal conveyor instead of the configuration This is referred to as first transfer means.

  In addition, a configuration in which the solidified material is transferred by natural fall from the solidified material quantitative feeder 8 to the second hopper 10 on the continuous mixing granulator 11, a configuration in which a horizontal conveyor is used instead of the configuration, and the like. This is referred to as second transfer means.

  Moreover, the structure which transfers a primary granulated material by the natural fall to the 3rd hopper 12 on the continuous stirring granulator 13 from the continuous mixing granulator 11, the structure which uses a horizontal conveyor instead of the structure, etc. This is referred to as third transfer means.

  Further, the insolubilizing material is transferred from the constant amount feeder 15 for insolubilizing material to the fourth hopper 14 on the continuous stirring granulator 13 by natural fall, and a configuration using a horizontal conveyor instead of the configuration is used. This is referred to as a fourth transfer means.

  As solidification materials, Portland cement, mixed cement (blast furnace slag cement, fly ash cement, silica cement), alumina cement, cement-based solidification material (general soft soil, high organic soil, hexavalent chromium countermeasure solidification material, Dust suppressive solidifying material), magnesium oxide and the like. To them, coal ash, blast furnace slag, gypsum (half water, two water, anhydrous), quicklime, slaked lime, silica fume, limestone and the like may be added.

  Solidifying materials include ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, sodium sulfide, sulfur, phosphoric acid, sodium phosphate, hydroxide apatite, fluorapatite, chelating agents, hypochlorous acid Can be used in combination.

  That is, if the heavy metal is arsenic, ferric sulfate and ferric chloride are selected. In the case of total mercury or lead, sodium sulfide and a chelating agent are selected. In the case of hexavalent chromium or cadmium, sodium sulfide is selected. In the case of selenium, sodium sulfide and ferrous sulfate are selected. In the case of all cyan, hypochlorous acid is selected. Thus, what is necessary is just to select suitably according to the heavy metal in incineration ash, sludge, soil, bottom sediment, stone powder, and regenerated powder.

  As coating materials, in addition to the cement and auxiliary materials described above, various inorganic materials such as water glass, volcanic ash, silicate white clay, and polymer compounds such as EVA (ethylene vinyl acetate), acrylic, acrylic-styrene, urethane, silicone, etc. Various materials can be applied.

It is a whole schematic block diagram which shows the Example which concerns on the insolubilization / solidification system of the heavy metal contaminated soil of this invention. It is a whole block diagram which shows the insolubilization and solidification system of heavy metal contaminated soil. It is a graph which shows the measurement result of the elution amount of arsenic. It is a graph which shows the measurement result of an apparent density. It is a graph which shows the measurement result of particle strength.

Explanation of symbols

6 ... Insolubilization / solidification system for heavy metal contaminated soil 7 ... Sludge fixed quantity feeder (sludge supply means)
8 ... Fixed quantity feeder for solidification material (solidification material supply means)
DESCRIPTION OF SYMBOLS 11 ... Continuous mixing granulator 13 ... Continuous stirring granulator 15 ... Fixed quantity supply machine for insolubilization material (insolubilization material supply means)
16 ... Mixed crusher

Claims (3)

Sludge supply means for quantitatively supplying fine particles (hereinafter referred to as sludge) having a particle size of less than 0.5 mm after washing and classifying treatment containing heavy metal;
A solidifying material supply means for quantitatively supplying the solidifying material;
The sludge supplied quantitatively from the sludge supply means is received via the first transfer means, and the solidified material fixedly supplied from the solidification material supply means is received via the second transfer means to sludge and solidify. A continuous mixing granulator that continuously mixes and granulates the material to produce a primary granulated product,
An insolubilizing material supply means for quantitatively supplying the insolubilizing material;
The primary granulated product from the continuous mixing granulator is received through the third transfer means and the insolubilized material from the insolubilized material supply means is received through the fourth transfer means to mix the primary granulated product. A continuous agitation granulator for producing a secondary granulated product by granulation and compaction, coating the surface of the secondary granulated product with an insolubilizing material, and continuously discharging;
An insolubilization / solidification system for heavy metal contaminated soil. In the insolubilization / solidification system of heavy metal contaminated soil according to claim 1,
Heavy metal-contaminated soil insolubilization / solidification system with a continuous mixing granulator equipped with a spray nozzle that supplies moderate moisture to the sludge. A mixing pulverizer that mixes and pulverizes fine particles (hereinafter referred to as sludge) having a particle diameter of less than 0.5 mm after washing and classifying treatment containing heavy metals and dry powder;
A solidifying material supply means for quantitatively supplying the solidifying material;
The sludge supplied quantitatively from the mixing crusher is received via the first transfer means, and the solidified material supplied quantitatively from the solidifying material supply means is received via the second transfer means, and sludge and solidified. A continuous mixing granulator that continuously mixes and granulates the material,
An insolubilizing material supply means for quantitatively supplying the insolubilizing material;
The primary granulated product from the continuous mixing granulator is received through the third transfer means and the insolubilized material from the insolubilized material supply means is received through the fourth transfer means to mix the primary granulated product. A continuous agitation granulator for producing a secondary granulated product by granulation and compaction, coating the surface of the secondary granulated product with an insolubilizing material, and continuously discharging;
An insolubilization / solidification system for heavy metal contaminated soil.

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