JP2009028639A - Sludge treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge treatment method capable of obtaining regenerated soil having hardness required for reclamation use or the like from even sludge of a high water content and also obtaining the regenerated soil having such a property that pH is close to neutral when treating the sludge generated on a construction site or the like to obtain the regenerated soil. <P>SOLUTION: The sludge treatment method comprises: a solidifying process of mixing the sludge and a solidifying material and solidifying the sludge; a crushing process of crushing a solidified object solidified in the solidifying process to obtain debris; and a neutralization process of bringing a carbon dioxide containing gas steam-extracted from a cement manufacturing facility and the debris into contact with each other to obtain the regenerated soil whose pH is equal to or lower than 8.6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating sludge generated from a site such as civil engineering work, and more particularly to a method for treating sludge for treating sludge having a high water content generated from a site such as civil engineering work as reusable reclaimed soil. .

  In recent years, from the viewpoint of reducing the environmental load, it is desired to reuse sludge generated from a site such as civil engineering as soil or the like without being buried in the final disposal site. However, when the moisture content of the sludge is high, it cannot be used as it is as a reclaimed soil, and conventionally, a method of using it as a reclaimed soil after dewatering or solidifying the sludge has been studied. Yes.

  However, in order to reduce the moisture content of sludge by dehydration, dehydration equipment such as a filter press is required, and the cost required for the treatment of the sludge increases.

  On the other hand, regarding the solidification treatment, a method using a solidifying material such as cement or lime (Patent Document 1), a method using a solidifying material using hemihydrate gypsum as a main material (Patent Document 2), and the like are known.

JP 2004-203962 A JP 2005-218959 A

  However, in the method using a solidifying material such as cement or lime, the reclaimed soil after the treatment exhibits strong alkalinity, and the use of the reclaimed soil is limited, or consideration for the surrounding environment is required. There is a problem.

  In addition, in the method using a solidified material made of hemihydrate gypsum as a main raw material, it can be treated while maintaining a neutral pH, but it is difficult to make recycled soil with sufficient strength for sludge with a high water content. There is a problem that a predetermined effect cannot be obtained unless it is used in combination with a polymeric water-absorbing agent.

  The present invention has been made in view of the problems of the prior art as described above, and when sludge generated at a construction site or the like is processed into recycled soil, even if it is sludge having a high water content, it can be used for reclamation or the like. It is an object to provide a method for treating sludge that can be used as a reclaimed soil having a strength required for an application, and that can be a reclaimed soil having a pH close to neutrality.

In order to solve the above problems, the sludge treatment method according to the present invention comprises a solidification step of mixing sludge and a solidifying material to solidify the sludge, and crushing the solidified body solidified in the solidification step by crushing And a neutralization step in which the carbon dioxide-containing gas extracted from the cement production facility and the crushed material are brought into contact with each other to use the crushed material as treated soil having a pH of 8.6 or less.
According to the present invention, since the crushed material is neutralized using the carbon dioxide-containing gas extracted from the cement production facility, there is an effect that the pH after the treatment is stabilized. In addition, there is an effect that the cost required for the neutralization treatment is reduced, and the usage of the treated soil after the neutralization treatment can be expanded.

The sludge treatment method according to the present invention further includes a drying step for reducing the moisture content of the sludge by heat generated in a cement manufacturing facility before the solidification step.
According to the present invention, the amount of sludge is reduced by the drying step, and the amount of solidification material used in the solidification step can be reduced due to a decrease in moisture content, and the sludge treatment cost can be reduced. .

The sludge treatment method according to the present invention is characterized in that the solidified body is accelerated and cured by heat generated in a cement production facility.
According to the present invention, when solidification of sludge is promoted, it is possible to shift to the next step at an early stage and to crush the solidified body. Further, even if the amount of the solidifying material added is the same, the strength after solidification is increased, so that it becomes difficult to clog at the time of sieving after crushing, and the sieving becomes easy.

  As described above, according to the sludge treatment method according to the present invention, when the sludge generated at a construction site or the like is processed into recycled soil, the strength required for landfill use even if the sludge has a high water content. In addition, it is possible to obtain a reclaimed soil having a property that the pH is close to neutrality.

Hereinafter, the sludge treatment method according to the present invention will be described with reference to the drawings.
FIG. 1 is a flow chart showing an embodiment of a sludge treatment method according to the present invention. As shown in FIG. 1, the sludge treatment method 1 according to the present embodiment includes a drying step 2 for reducing the moisture content of the sludge by heat 11 generated by the cement manufacturing facility (shown in FIG. 2), and the moisture content. The solidification process 3 which solidifies the sludge mixed with the reduced sludge and the solidified material, the accelerated curing process 4 which performs the accelerated curing of the solidified body by the heat 12 generated by the cement manufacturing facility, and the solidified body which has been accelerated and cured The pulverized process 5 for pulverizing the slag into a predetermined particle size, the gas 13 having a high carbon dioxide concentration extracted from the cement production facility, and the crushed material obtained in the pulverized process 5 are brought into contact with each other to regenerate soil having a pH of 8.6 or less. And a neutralization step 6.

In the drying step 2, a high-temperature gas extracted from the cement production facility can be used as the heat source 11. More specifically, a high-temperature gas of 200 to 400 ° C. generated from the clinker cooler, a high-temperature gas sent from the preheater 31 to the chimney, or the like is extracted, and the high-temperature gas itself is used as a heat medium in the drying step 2, or Another medium that has been heat exchanged with the hot gas can be used as the heat medium in the drying step 2.
Moreover, in this drying process 2, it is preferable to make the temperature of the heat medium which contacts sludge directly or indirectly into 40 degreeC or more, and it is more preferable to set it as 100 degreeC or more.

  In the drying step 2, it is preferable to adjust the treatment temperature and treatment time so that the moisture content of the treated sludge is 30 to 70%, and the treatment temperature so that the moisture content is 30 to 40%. More preferably, the processing time is adjusted. If the moisture content of the sludge is 30 to 70%, it becomes possible to obtain a solid body with high strength by a relatively small amount of solidifying material in the solidification step 3, and it is not necessary to add water required for hydration. Show the effect.

  In the solidifying step 3, various types of cement, cement-based solidified material, quicklime, magnesium oxide, etc. can be used alone or in combination as a solidifying material. From the viewpoint of convenience when utilizing the above, various cements or cement-based solidified materials produced in the cement production facility can be suitably used.

The addition amount of the solidifying material is preferably 50 kg or more with respect to 1 m ^{3 of} sludge from the viewpoint of homogeneous mixing with sludge, and preferably 300 kg or less with respect to 1 m ^{3 of} sludge from the viewpoint of economy. .
Further, the three-day strength of the solidified solidified body is preferably 200 kN / m ² or more (uniaxial compression strength 50 kN / m ² ) or more, and 800 kN / m ² or more (uniaxial compression strength 200 kN / m). ² ) More preferably.

  The solidification step 3 is not particularly limited as long as sludge and solidification material are mixed and solidified. For example, the first step of mixing sludge and solidification material with a mixer; It can carry out by passing through the 2nd process of casting and solidifying the mixture obtained by one process in a mold.

In the accelerated curing step 4, it is preferable to heat the solidified body to be 30 ° C. or higher from the viewpoint of sufficiently exerting the promoting effect, and it is possible to prevent a decrease in strength due to deterioration due to high temperature. From the viewpoint, it is preferable to suppress the heating of the solidified body to 60 ° C. or less.
The heating time is not particularly limited, but is preferably 1 to 72 hours, and more preferably 1 to 24 hours.

In the accelerated curing process 4, a high-temperature gas extracted from a cement production facility can be used as the heat source 12. More specifically, a high-temperature gas of 200 to 400 ° C. generated from the clinker cooler is extracted, and the high-temperature gas itself is used as a heat medium in the accelerated curing process 4 or another medium heat-exchanged with the high-temperature gas. Can be used as a heat medium in the accelerated curing process 4.
The heat medium after being used as the heat source 11 in the drying step 2 can also be used as the heat source 12 in the accelerated curing step 4.

  The accelerated curing process 4 is not particularly limited as long as the accelerated curing of the solidified body can be performed by heat generated in the cement production facility. For example, the solidified body is accommodated in a container, and the container The heat medium can be introduced as an internal atmosphere and maintained at a predetermined temperature for a predetermined time, whereby the solidified body can be accelerated and cured.

In the crushing step 5, the solidified body has a particle size of 100 mm or less, preferably a particle size of 50 mm or less, more preferably a particle size of 10 mm or less. By crushing the solidified body, the solidified body can be efficiently neutralized in the subsequent neutralization step 6.
In addition, the particle size of the crushed material in this embodiment shall be determined by the mesh width of the sieve used when sieving the crushed material. That is, the crushed material having a particle size of 100 mm or less means a crushed material that has passed through a sieve having a mesh width of 100 mm.

  The crushing means in the crushing step 5 is not particularly limited, and any crushing device can be used. Moreover, you may crush, drying a crushed material.

In the neutralization step 6, the gas 13 having a high carbon dioxide concentration is preferably a gas having a carbon dioxide concentration of 0.5% by volume or more, more preferably 5.0% by volume or more. Is done.
As such gas, for example, as shown in FIG. 2, among the gases sent from the preheater 31 of the cement manufacturing facility 30 to the chimney, the gas 13 a discharged from the outlet of the preheater 31 and the raw material mill 32 are supplied. The gas extracted from the gas 13b or the gas 13c discharged | emitted from the exit of the electrostatic precipitator 33 can be mentioned. These gases have a carbon dioxide concentration of about 15% by volume, and are extremely suitable for the neutralization step. Among these, the gas 13c discharged from the outlet of the electrostatic precipitator 33 can be suitably used from the viewpoint that the humidity of the gas and the content of dust and impurities contained in the gas are small.

  Moreover, in this neutralization process 6, although the pH of the recycled soil after a process needs to be 8.6 or less, it is preferable to make pH into 8.0-8.3. By setting the pH of the reclaimed soil after treatment to 8.3 or less, the strength of the reclaimed soil when the reclaimed soil is backfilled can be more reliably prevented.

  The specific treatment method in the neutralization step 6 is not particularly limited as long as it is a method for obtaining a reclaimed soil exhibiting a predetermined pH by bringing a solidified body and a carbon dioxide-containing gas into contact with each other. For example, a method of circulating the gas in a container filled with the solidified body, a method of stirring the solidified body in a tank filled with a carbon dioxide-containing gas, or the like can be employed.

According to the present embodiment, the heat 11 in the drying step 11, the heat 12 in the accelerated curing step 4, and the gas 13 having a high carbon dioxide concentration in the neutralization step can be supplied from the cement production facility. Therefore, even sludge with a high water content can be treated stably and quickly at an extremely low cost, and the treated sludge can be reused for various purposes as recycled soil.
In addition, in the cement production facility, not only are there abundant gases containing high-temperature gas and high-concentration carbon dioxide, but also cement-based materials that can be used as a solidifying material are produced. Can be effectively used for sludge treatment.

  In addition, this invention is not limited to the said embodiment, Of course, it can change variously within the range which does not deviate from the summary of this invention.

  Examples of the present invention will be described below, but the present invention is not limited to the examples.

(Preparation of sample soil)
Using construction sludge (water content ratio 88.0%, hereinafter referred to as “current soil”) generated by shield construction, the current soil is naturally dried in a room at 20 ° C. and 60% RH for a predetermined period to a water content ratio of 67.1%. An adjusted one (hereinafter referred to as “adjusted soil A”) and an adjusted water content ratio of 37.3% (hereinafter referred to as “adjusted soil B”) were prepared. Table 1 shows the properties of the current soil used.

(Test method)
Hereinafter, the uniaxial compression test is measured according to JIS A 1216 “Soil uniaxial compression test method”, and the pH test is measured according to Geotechnical Society standard JGS 0211 “Soil suspension pH test method”. did.

(Test Examples 1-9)
Using the current soil, adjusted soil A, and adjusted soil B, 50 kg, 75 kg, and 100 kg of the solidified material are added and mixed to 1 m ^{3 of the} soil to be treated, and then placed in a cylindrical form frame of φ50 mm × height 100 mm. After 24 hours, the mold was removed to prepare a test specimen. Furthermore, this test body was covered with Saran wrap, hermetically cured in a curing tank at 20 ° C. and 95% RH until the age of 3 days, and the uniaxial compressive strength was measured. The results are shown in Table 2.

From Table 2, in the test example using the adjusted soil A and the adjusted soil B adjusted to a water content ratio in the range of 30 to 70%, compared with the current soil with a water content ratio of 88%, it is uniaxial with the same solidifying material addition amount The compressive strength is increased. In particular, in the test example using the adjusted soil B in which the water content ratio is adjusted to a range of 30 to 40%, it is recognized that the uniaxial compressive strength is greatly increased.
From this result, the amount of solidification material required to make the uniaxial compressive strength 200 kN / m ³ at the age of 3 days is about 75 kg for the current soil, about 60 kg for the adjusted soil 1, and about 50 kg for the adjusted soil 2 It is calculated that there is.

(Test Examples 10 to 14)
50 kg, 100 kg and 150 kg of solidified material were added to the adjusted soil A1 m ^{3 and} casted. After 24 hours, the mold was removed, covered with Saran wrap, a curing tank of 20 ° C./95% RH and 40 ° C./95% RH. Was cured in a curing tank for 24 hours, and the uniaxial compressive strength was measured. The results are shown in Table 3.

  As shown in Table 3, when the curing temperatures are 20 ° C. and 40 ° C., the uniaxial compressive strength is remarkably increased when the curing temperature is 40 ° C., and the curing temperature is set to 30 ° C. or higher. It can be seen that the period can be greatly shortened.

(Neutralization treatment and pH measurement)
As in Test Example 11 above, using adjusted soil A, 100 kg of solidified material was added to 1 m ^{3 of the} soil to be treated, casted, removed for 24 hours, ground with a hammer, and then sieved. A particle group X having a particle size of 4.25 mm to 9.5 mm and a particle group Y having a particle size of about 50 mm were prepared. These particle groups X and Y were each neutralized, and the pH was measured at a predetermined age.
The pH value measurement results for particle group X are shown in Table 4, and the pH value measurement results for particle group Y are shown in Table 5, respectively.
In the table, “granular” indicates a case where the neutralized particles are placed in water as they are and the pH is measured, and “pulverized” refers to the water after the neutralized particles are further finely crushed. It is the value which measured pH by putting it in.

As shown in Table 4, in the particle group X having a particle size of 4.25 mm to 9.5 mm, the pH exceeded 11 even after 14 days in the tank sealed curing, and the pH was 8. even after 14 days in the indoor exposure curing. to 8 or more at which the drops to a pH of 8.3 CO ₂ concentration after the lapse of 5% by volume of CO ₂ cured (1) in 24 hours, CO ₂ concentration of 15% by volume of CO ₂ curing (2) Then, the pH is 8.3 or less after 3 hours.
Further, as shown in Table 5, also in the particle group Y having a particle size of about 50 mm, the pH in the tank sealed curing and the indoor exposure curing is 11 or more even after 7 days, whereas the CO ₂ concentration is 5 volumes. % CO ₂ curing (1), pH drops to 8.3 after 3 days.
From these results, it can be seen that the treatment time can be greatly shortened by carrying out the neutralization treatment with a high CO ₂ concentration and the neutralization treatment with a small particle size.

(Measurement of strength after neutralization assuming backfill)
For the particle group X (particle size: 4.25 mm to 9.5 mm), a sample after 24-hour neutralization treatment with a sealed curing in a tank and a CO ₂ curing (1) is used, and a crushed material is assumed for backfilling. Was compacted in a mold, and the subsequent strength development was measured by uniaxial compressive strength. The results are shown in Table 5.

As shown in Table 6, the strength of the sample sealed and cured in the tank is increased to a value exceeding 1500 kN / m ^2, which is unfavorable for land use after landfill (for example, re-excavation). It is recognized that
On the other hand, in the sample cured with the CO ₂ curing (1) having a CO ₂ concentration of 5% by volume, the strength after the treatment hardly increases even after backfilling, and it is recognized that it is effective for re-digging and the like.

The flowchart which showed 1st embodiment of the processing method of the sludge which concerns on this invention. The figure which showed an example of the cement manufacturing equipment and illustrated the extraction location of the carbon dioxide containing gas collectively.

Explanation of symbols

1 Sludge treatment method 2 Drying process 3 Solidification process 4 Curing promotion process 5 Crushing process 6 Neutralization process 13 Gas with high carbon dioxide concentration extracted from cement production equipment 30 Cement production equipment

Claims (3)

  A solidification step of solidifying the sludge by mixing sludge and a solidifying material; a crushing step of crushing the solidified body solidified in the solidification step into a crushed product; a carbon dioxide-containing gas extracted from a cement production facility; A sludge treatment method comprising: a neutralization step of bringing the crushed material into contact with regenerated soil having a pH of 8.6 or less.   The sludge treatment method according to claim 1, further comprising a drying step of reducing the moisture content of the sludge by heat generated in a cement manufacturing facility before the solidification step.   The method for treating sludge according to claim 1 or 2, wherein the accelerated curing of the solidified body is performed by heat generated in a cement production facility.

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