JP7768581B2 - Construction sludge treatment device and construction sludge treatment method - Google Patents

Description

The present invention relates to a construction sludge treatment device and construction sludge treatment method for regenerating construction soil and construction sludge, which are industrial waste, into slurry-like fluidized treated soil that can be used as general-purpose sand, plastering sand, and other recycled sand, as well as backfill material.

Conventionally, construction sludge, which is generated at construction sites and contains a lot of moisture, has been treated as industrial waste and mixed with cement and other materials at intermediate treatment plants to produce liquefied treated soil for backfilling. Patent Document 1 provides an example of a system for producing liquefied treated soil by collecting construction mud at a factory and processing it. Patent Document 1 discloses a technology in which large gravel and stone fragments are removed from the mud collected at the factory, and the mud is stored at the factory in the form of a wet muddy liquid or in the form of a dehydrated substance. The specific gravity of the muddy liquid is adjusted according to the requirements of the site of use, and cement and other materials are mixed into the muddy liquid to produce liquefied treated soil.

Patent Document 2 also discloses a method for reusing and reducing the volume of construction waste soil and sludge, in which water is added to soil material made from construction waste soil and sludge to dissolve the soil, and gravel is removed. The resulting sludge and cement milk are then supplied to a truck mixer and mixed together to produce fluidized treated soil.

Patent Document 3 also discloses a simple method for supplying liquefied treated soil, in which water is mixed with the soil to loosen the soil, and then relatively large foreign objects are removed using a vibrating screen.

Japanese Patent Application Laid-Open No. 2006-051437 JP 2018-021378 A Japanese Patent Application Laid-Open No. 2021-070992

In the prior art described in Patent Documents 1 to 3, the construction soil and sludge generated at construction sites vary greatly in properties, with specific gravities ranging from 1.1 to 1.4 and pH levels ranging from 6 to 12. They are made from industrial waste sludge containing organic matter and cementitious substances, and as a result, there are differences in the strength, fluidity, separation resistance, and other performance characteristics of the recycled liquefied treated soil. Even if the amount of solidifying agent such as cement added is adjusted, liquefied treated soil with the desired properties cannot be obtained in strength and separation tests after production, resulting in a high level of waste.

Furthermore, problems with the treatment process include the steps of receiving, classifying, storing, mixing, and shipping. However, since the sand content varies during classification, there are large differences in the sand concentration of the stored raw materials, which can easily lead to variations in the quality of the produced liquefied treated soil. Furthermore, if the pH of the raw materials is high and the storage time during treatment is long, scale can form on the walls, mixing blades, and piping, which can cause blockages in the case of piping. This poses the problem of increased production downtime due to maintenance to remove the scale.

Furthermore, if the concentration of the raw material muddy water is low, it is necessary to increase the amount of solidification material added. However, many of the solidification material components are cement-based, which emits a lot of _CO2 , which poses problems not only in terms of cost but also in terms of the environmental burden. As demand for liquefied treated soil has increased in recent years, it has become important to find ways to turn a variety of raw materials (industrial waste sludge) into products that best meet needs. At the same time, from the perspective of the Sustainable Development Goals (SDGs), there is a demand for both reducing the amount of solidification material used and making effective use of raw materials.

The object of the present invention is therefore to provide a construction sludge treatment device and construction sludge treatment method that can use the increasingly diverse construction soil and construction sludge as raw materials to produce liquefied treated soil of the desired quality with a minimum amount of solidifying agent, and that can recover valuable sand.

The construction sludge treatment device of the present invention comprises:
A construction sludge treatment device that regenerates construction soil (solid) and construction sludge (liquid) into reclaimed sand and liquefied treated soil,
a soil receiving section into which construction soil is transported;
a sludge receiving section into which construction sludge is carried;
a crushing unit that crushes the construction soil and sand carried into the soil receiving unit and the construction sludge carried into the sludge receiving unit;
a classification unit that separates the material to be treated after being crushed by the crushing unit into recycled sand and suspended water;
a neutralization processing unit that adds a neutralizing agent to the suspended water separated by the classification unit to neutralize the suspended water;
a sedimentation and concentration section in which a flocculant is added to the suspended water neutralized in the neutralization section to flocculate suspended matter in the suspended water and obtain concentrated suspended water;
and a fluidized soil production section that adds a solidification material to the suspended water concentrated in the sedimentation concentration section to produce a slurry of fluidized soil.

Furthermore, the configuration of the construction sludge treatment device of the present invention is characterized in that the sludge receiving section includes a raw sludge pit for storing the construction sludge, and a sand divider for separating the construction sludge into solids and suspended liquid, and the sand divider includes a vibrating screen, a cyclone, and an adjustment tank.

The construction sludge treatment device described in claim 1, characterized in that the crushing unit includes a ball mill.

The construction sludge treatment device of the present invention is also characterized in that the classification section includes a spiral classifier, a vibrating sieve for draining, and a cyclone.

Furthermore, the construction sludge treatment device of the present invention is characterized in that the recycled sand is sand particles with an average particle size of 0.74 mm to 2 mm.

The construction sludge treatment method of the present invention is a construction sludge treatment method for regenerating construction soil and construction sludge into sand and liquefied treated soil,
a soil receiving process in which construction soil is transported;
a sludge receiving process in which construction sludge is transported;
a crushing step of crushing the construction soil and sand delivered in the soil receiving step and the construction sludge delivered in the sludge receiving step;
a classification step of separating the material to be treated after being crushed in the crushing step into recycled sand and suspended water;
a neutralization treatment step of neutralizing the suspension separated in the classification step by adding a neutralizing agent;
a sedimentation and concentration step of adding a flocculant to the suspension water neutralized in the neutralization treatment step to flocculate suspended matter in the suspension water to obtain a concentrated suspension water;
The method is characterized by including a fluidized-treated soil production process in which a solidifying material is added to the suspension water concentrated in the sedimentation concentration process to produce a slurry of fluidized-treated soil.

According to the present invention, by simultaneously treating construction soil and construction sludge, even raw materials containing a wide variety of soil, mud, sludge, and muddy water can be effectively utilized by reducing the amount of solidification material and regenerating them into slurry-like fluidized treated soil that can be used as sand with desired properties (general-purpose sand, plastering sand, etc.) or as backfill material, etc.

Furthermore, according to the present invention, by providing a neutralization treatment section before the sedimentation thickening section, scaling is less likely to occur on the walls, agitator blades, and piping, even when the incoming sludge contains a lot of calcium and has a high pH, thereby reducing production downtime due to maintenance to remove the scale and preventing piping blockage. Furthermore, even if the pH fluctuates due to differences in the calcium content of the incoming muddy water, fluctuations in the amount of solidifying agent added can be reduced, preventing deterioration in the performance of the liquefied treated soil and stabilizing its performance.

1 is a diagram showing the overall configuration of a construction sludge treatment apparatus according to one embodiment of the present invention. FIG. 2 is an enlarged view showing the configuration of the soil receiving section A. FIG. 2 is an enlarged view showing the configuration of the sludge receiving section B. FIG. 10 is an enlarged view showing a configuration in which a ball mill 28 is used in the crushing section C. FIG. 2 is an enlarged view showing the configuration of a classifying unit D. FIG. 2 is an enlarged view showing the configuration of the neutralization processing unit E. FIG. 1 is an enlarged view showing the configuration of a sedimentation thickening section F when a square thickener 57 is used as a sedimentation separation device that performs sedimentation and separation by adding a polymer flocculant. FIG. 2 is an enlarged view showing the configuration of the slurry storage tank section G. An enlarged view showing the configuration of the liquefied treated soil production section H. FIG. 2 is an enlarged view showing the configuration of the dehydration section I.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a diagram showing the overall configuration of a construction sludge treatment device 1 according to one embodiment of the present invention. The following description assumes that a construction sludge treatment method is carried out using the construction sludge treatment device 1. The construction sludge treatment device 1 according to this embodiment can be used to recycle treated soil, including construction waste soil, dredged soil, high-moisture muddy construction mud, construction sludge, and construction muddy water generated by ground excavation during construction work, into sand (general-purpose sand, plastering sand, etc.) and liquefied soil. Sand (general-purpose sand, plastering sand, etc.) is used for construction materials, parks, etc. Furthermore, liquefied soil has fluidity and self-hardening properties and is used for underground pipes, backfill soil for utility ducts, and filling cavities in building foundations. The construction sludge treatment device 1 includes a soil receiving section A, a sludge receiving section B, a crushing section C, a classification section D, a neutralization treatment section E, a sedimentation and thickening section F, a slurry storage tank section G, a liquefied soil production section H, and a dewatering section I.

(Section A for receiving soil and sand)
2 is an enlarged view showing the configuration of the soil receiving section A. The soil receiving section A includes a soil pit 2A into which solid construction sludge such as soil and sand is transported by a transport vehicle 10A such as a dump truck, an inclined sieve 3, a magnetic sieve 4, a transport conveyor 5, and a backhoe 7 equipped with a bucket that supplies treated soil 6 in the soil pit 2A to the inclined sieve 3.

Soil 6 to be treated, delivered into the soil pit 2A by a transport vehicle 10A, is supplied to the inclined sieve 3 by a backhoe 7. The inclined sieve 3 drops particles with an average particle size of 150 mm or less from the supplied soil 6 to the transport conveyor 5, and discharges particles with an average particle size of more than 150 mm to the rubble pit 2B by the transfer means 8. In addition, gravel that has fallen onto the sieve of the lower sieve of the vibrating sieve 13 is transferred from the sludge receiving section B to the soil pit 2A by the transfer means 17. Particles that pass through the inclined sieve 3 and the material to be treated transferred from the sludge receiving section are fed by the transfer conveyor 5 into the material receiving section 29 of the crushing section C. The transport conveyor 5 consists of a first conveyor 5A, a second conveyor 5B, and a third conveyor 5C, and a magnetic sieve 4 is placed above the third conveyor 5C on the downstream side in the transport direction to remove metals such as iron and nickel from the material being treated.

(Sludge receiving section B)
3 is an enlarged view showing the configuration of the sludge receiving section B. The sludge receiving section B includes a raw mud pit 11 for storing fluid construction sludge (fluid matter) and a sand divider 12 for separating the construction sludge into solids and suspended solids. The sand divider 12 includes a vibrating screen 13, a cyclone S1, and an adjustment tank 14.

Fluid construction sludge, such as mud and muddy water, is transported into the raw mud pit 11 by a transport vehicle 10B, such as a tanker truck. The space within the raw mud pit 11 is divided into a first raw mud pit tank 11A and a second raw mud pit tank 11B by a partition wall 11C. Construction sludge is transported into the first raw mud pit tank 11A from the transport vehicle 10B. Heavy solids such as sand and gravel in the construction sludge transported into the first raw mud pit tank 11A are allowed to settle, while liquids containing light solids flow over the partition wall 11C into the second raw mud pit tank 11B, where they are stored. Note that if the construction sludge being transported does not contain heavy solids such as sand and gravel, the construction sludge can be directly dumped into the second raw mud pit tank 11B. An agitation sand pump P1 is installed at the bottom of the first raw mud pit tank 11A, and a mixture of construction sludge settled in the first raw mud pit tank 11A and water containing heavy solids such as sand and gravel is sucked up by the agitation sand pump P1 and pumped through a pipe 15 connected to the discharge port of the agitation sand pump P1 to the treated material receiving section 29 of the crushing section C. A discharge pump P2 is installed at the bottom of the second raw mud pit tank 11B, and the liquid construction sludge at the bottom of the second raw mud pit tank 11B is transferred via a pipe 16 connected to the discharge port of the discharge pump P2 to the lower sieve of the vibrating screen 13 of the sand divider 12.

The vibrating sieve 13 is a two-tiered vibrating sieve, with the upper sieve having finer mesh than the lower sieve. The mesh sizes of the sieves range from 0.3 to 30 mm, with the upper sieve having finer mesh than the lower sieve. For example, the upper sieve has a mesh size of 0.5 mm and the lower sieve has a mesh size of 20 mm. The gravel on the sieve sieved out by the lower sieve of the vibrating sieve 13 is transferred to the sediment pit 2A by transfer means 17. The transfer means 17 may be, for example, a drop chute. A cyclone S1 is disposed above the vibrating sieve 13. The cyclone S1 has a supply port, a first outlet, and a second outlet. One end of pipe 18 is connected to the supply port, pipe 19 is connected to the first outlet, and pipe 20 is connected to the second outlet.

The adjustment tank 14 of the sand divider 12 has a partition wall 21. The partition wall 21 divides the space within the adjustment tank 14 into a settling chamber 22 and an agitation chamber 23. Fine particles separated by the cyclone S1 are supplied to the settling chamber 22 via a pipe 20 connected to the cyclone's second outlet. A discharge pump P3 is provided in the settling chamber 22. The other end of pipe 18 is connected to the discharge port of the discharge pump P3. The material in the lower layer of the settling chamber 22 is sucked into the discharge pump P3 and guided via pipe 18 to the supply port of the cyclone S1, where the solids are separated according to weight. Within the cyclone S1, heavy solids are returned to the upper sieve of the vibrating screen 13 via pipe 19, while lighter particles are supplied to the settling chamber 22 via pipe 20. The suspended water containing lighter solids from the settling chamber 22 overflows the partition wall 21 and flows into the agitation chamber 23.

A stirring blade 24 is disposed in the stirring chamber 23. The stirring blade 24 is mounted on a rotating shaft 25 that is driven to rotate around a vertical axis by a motor M1, and stirs the material to be treated in the stirring chamber 23 to prevent sedimentation and accumulation. An outlet is provided in the side wall of the stirring chamber 23, and one end of a pipe 26 is connected to the outlet. The other end of the pipe 26 is connected to the inlet of a discharge pump P4. One end of a pipe 27 is connected to the discharge outlet of the discharge pump P4, and the material to be treated is transferred via the pipe 27 and from the other end of the pipe 27 to the fluidization mixer tank 72 or the dewatered sludge tank 88. When the material is to be used in the fluidization mixer tank 72, dilution water is supplied to the stirring chamber 23 via pipe 87B by a dilution pump P16, and its specific gravity is adjusted.

(Crushing part C)
In the crushing section C, a crusher such as a ball mill, rod mill, or hammer mill can be used as the crusher. However, it is preferable to use a ball mill, which can obtain high-quality sand without excessive crushing and can achieve both mud crushing and sand classification. By using a ball mill, it is possible to crush the mud lumps while leaving the sand, and it is possible to maintain the properties of the mud water containing the crushed solids and ensure the amount of sand recovered as a valuable resource. Below, an example of using a ball mill in the crushing section C will be described.

Figure 4 is an enlarged view showing the configuration in which a ball mill 28 is used in the crushing section C. The ball mill 28 comprises a workpiece receiving section 29, a ball mill main body 30, and a sieving means 31. A dedicated hopper-shaped feeder is used for the workpiece receiving section 29. The ball mill main body 30 is cylindrical and has a rotating drum in which multiple iron balls are stored. The sieving means 31 is connected to the discharge outlet of the ball mill main body 30 and is formed into an approximately truncated cone shape using wire mesh. In this embodiment, a cylindrical sieving means with a truncated cone shape that widens in diameter toward the tip is preferred.

The material receiving section 29 of the crushing section C receives particles supplied from the sediment receiving section A, particle-containing water supplied from the sludge receiving section B via pipe 15, and washing water, and supplies this mixture to the ball mill main body 30. The particles supplied from the sediment receiving section A can be supplied from the sediment receiving section A by a transport means 9 such as a belt conveyor. The particle-containing water supplied from the sludge receiving section B is supplied from the bottom of the raw mud pit second tank 11B of the sludge receiving section B via pipe 15 installed from the sludge receiving section B by an agitation sand pump P1. The washing water is sucked up by a discharge pump P5 via pipe 85 installed from the circulating water tank 84 and supplied to the material receiving section 29. The circulating water tank 84 is a storage tank for storing the circulating water that circulates within the construction sludge treatment device 1 of this embodiment. As described below, the circulating water tank 84 is supplied with overflow water from the square thickener 57 in the sedimentation and concentration section F and filtrate from the filter press 76 in the dewatering section I. In addition, if there is a shortage of circulating water, make-up water is added from outside.

The ball mill main body 30 contains multiple iron balls in a cylindrical rotating drum. The impact of the iron balls falling as the drum rotates crushes the mixed material. For example, in a device with a rotating drum with a diameter of 2.1 m and a length of 3.3 m, 100 to 200 10 cm diameter iron balls are used. By using this type of ball mill, the material is stirred and crushed while being washed with wash water. This allows for the use of spherical weights that are lighter than those used in rod mills and rod scrubbers, and does not crush the raw material excessively finely. This allows for the production of recycled sand with an average particle size of 2 mm or less, which is highly useful as wall materials and fine aggregate for concrete mortar. Furthermore, when the iron balls wear out, ball mills simply require new iron balls to be replenished. This eliminates the need to replace worn rods, making them easier to maintain than rod mills and rod scrubbers.

The material to be processed, which is muddy water containing solids crushed in the ball mill main body 30, is discharged into the sieving means 31, which is connected to the discharge port of the ball mill main body 30. Uncrushed solids are separated using a truncated cone-shaped cylindrical wire mesh (trommel) that expands in diameter toward the tip. The uncrushed solids are collected in the overtank 32. The mesh size of the wire mesh of the sieving means 31 can be determined according to the particle size of the recycled sand to be reused. For example, if a wire mesh with a mesh size of 5 mm is used, versatile sand of 5 mm or less can be obtained. The muddy water (material to be processed) containing crushed solids that passes through the mesh of the wire mesh of the sieving means 31 is transferred to the classifying section D via the flow path 86.

(Classification Department D)
5 is an enlarged view showing the configuration of the classification unit D. In the classification unit D, the material crushed in the crushing unit C is separated into recycled sand and suspended water. The classification unit D is composed of a first classification unit D1, a second classification unit D2, and a raw water pit 37. The first classification unit D1 is composed of devices such as a spiral classifier 33 and a vibrating screen 36 for draining. The second classification unit D2 is composed of a cyclone S2 and a vibrating screen 46 for draining.

First, we will explain the first classification section D1. The spiral classifier 33 is composed of a pit 34 below the spiral classifier and a screw conveyor 35. The material crushed in the crushing section C is transferred to the pit 34 of the spiral classifier 33 via a flow path 86. It is preferable to position the sieving means 31 of the ball mill 28 higher than the pit 34 to allow the material to fall naturally. If the pit 34 is positioned directly below the sieving means 31 of the ball mill 28 to allow the material to fall naturally, the flow path 86 is not necessary. Large-grained crushed solids settle to the bottom of the pit 34 and are transported by the screw conveyor 35 to the draining vibrating screen 36. The suspended water containing small-grained crushed solids not transferred by the screw conveyor 35 overflows the pit 34 of the spiral classifier and flows into the raw water pit 37.

The draining vibrating sieve 36 is a vibrating sieve with 1.0 mm mesh. Muddy water containing large-grained crushed solids transported by the screw conveyor 35 falls onto the sieve, while coarse-grained recycled sand that does not pass through the sieve is collected in the sand yard 39 by the belt conveyor 38. The suspended water that passes through the sieve is transferred to the raw water pit 37.

Next, we will explain the second classification section D2. In the second classification section D2, a water-removing vibrating sieve 46 equipped with a cyclone S2 on top is used to classify finer sand than that obtained in the first classification section D1. The cyclone S2 is supplied with suspended water concentrated in the suspended water receiving pit 51A from the suspended water receiving pit 51A of the neutralization processing section E.

Cyclone S2 separates and collects large particles from the suspended water transferred via pipe 49 from the suspended water receiving pit 51A of the neutralization treatment unit E by centrifugation at the bottom of cyclone S2, and returns the particles to the sieve of the draining vibrating sieve 46 via pipe 44. The suspended water containing particles not collected by cyclone S2 overflows from the top of cyclone S2 and is discharged via pipe 45 located above cyclone S2 into the suspended water receiving pit 51A of the neutralization treatment unit E.

The suspended water supplied from cyclone S2 via pipe 44 to the draining vibrating sieve 46 is separated into recycled sand and suspended water by the draining vibrating sieve 46. By supplying wash water to the draining vibrating sieve 46 to wash the sand on the sieve, higher quality recycled sand can be produced. The recycled sand separated by the draining vibrating sieve 46 is collected in a sand yard 48 by a belt conveyor 47. The suspended water that passes through the sieve meshes of the draining vibrating sieve 46 is transported by gravity to the raw water pit 37.

The draining vibrating sieve 46 of the second classification section D2 can produce ultra-fine sand of 1.0 mm or less, and if the sieve opening is set to 0.8 mm, it can produce sand of 0.8 mm to 1.0 mm. This ultra-fine sand can be used for plastering sand, etc.

The mesh size of the draining vibrating sieve 36 in the first classification section D1 is set to 1.0 mm, and high-quality recycled sand can be produced by removing the fine SS particles and moisture with a dewatering sieve. When using a sieve with this mesh size, the sand that does not pass through the sieve has an average particle size of 1 mm to 2 mm, making it a highly versatile sand with excellent drainage. Furthermore, the sand that is not captured by the draining vibrating sieve 36, separated by the cyclone S2, and captured by the draining vibrating sieve 46 has an average particle size of 0.8 mm to 1 mm and can be used as plastering sand. By setting the mesh size of the draining vibrating sieve 36 to 1 mm and combining it with the cyclone S2 and the draining vibrating sieve 46, plastering sand with a fine average particle size can be obtained, allowing for effective use of recycled sand.

The raw water pit 37 is equipped with an agitator 40, which agitates the suspended matter in the suspended water received from the pit 34 below the spiral classifier, the draining vibrating sieve 36, and the draining vibrating sieve 46 to prevent settling and sedimentation. Any agitator 40 can be used as long as it is capable of agitating the suspended matter in the raw water pit 37 to prevent settling and sedimentation. However, an agitator 40 in which a rotating shaft 42 equipped with a stirring blade 41 is driven by a motor M2, as shown in Figure 5, is preferably used. The suspended water in the raw water pit 37 is transferred to the suspended water receiving pit 51A of the neutralization treatment unit E via a pipe 43 attached to the discharge pump P6.

(Neutralization processing section E)
The construction sludge and muddy water treated in this embodiment contain a large amount of cement components and therefore have a high pH value, and the wastewater produced during treatment needs to have its pH adjusted before being discharged. However, if the pH value is high during the treatment process, the treated material will solidify and adhere to the equipment as scale, causing problems such as the need to shut down the production equipment for maintenance. For this reason, in this embodiment, a neutralization treatment unit E is provided after the classification unit D.

Figure 6 is an enlarged view showing the configuration of the neutralization treatment unit E. The neutralization treatment unit E includes a dilute sulfuric acid tank 50 and a pH adjustment tank 51. The pH adjustment tank 51 is separated by a partition wall 51C into a suspended water receiving pit 51A and an adjustment and mixing tank 51B.

Suspended water is supplied to the suspended water receiving pit 51A from the raw water pit 37 of the classification section D via pipe 43, and suspended water is transferred from the cyclone S2 of the second classification section D2 via pipe 45. By retaining suspended water in the suspended water receiving pit 51A, suspended matter with a high specific gravity settles to the bottom, creating a difference in the concentration of suspended water between the top and bottom of the suspended water receiving pit 51A. The suspended water with a lower concentration of suspended matter at the top overflows the upper end of the partition wall 51C and flows into the adjustment mixing tank 51B. A discharge pump P15 is disposed at the bottom of the suspended water receiving pit 51A, and pipe 49 is connected to the discharge outlet of the discharge pump P15, supplying suspended water with a higher concentration of suspended matter to the cyclone S2 of the second classification section D2.

The adjustment stirring tank 51B is equipped with an agitator 52 for agitating the suspended water within the adjustment stirring tank 51B. Dilute sulfuric acid is drawn from the dilute sulfuric acid tank 50 by a metering pump P7 and injected into the adjustment stirring tank 51B via a pipe 53 to adjust the pH of the suspended water. Any agitator 52 can be used as long as it is capable of agitating the suspended matter within the adjustment stirring tank 51B without causing sedimentation or accumulation. However, an agitator 52 in which a rotating shaft 55 equipped with an agitator blade 54 is rotated by a motor M3, as shown in Figure 6, is preferably used.

pH adjustment can be performed by measuring the pH value in the adjustment stirring tank 51B, but more precise pH adjustment is possible by measuring the flow rate and pH value of the inflowing suspended solids and using feedforward or feedback control. Furthermore, by increasing the capacity of the pH adjustment tank 51, product variation can be prevented. The suspended solids whose pH has been adjusted in the pH adjustment tank 51 are transferred from the pH adjustment tank 51 by discharge pump P8 via pipe 56 to the settling and thickening section F. Furthermore, a portion of the pH-adjusted suspended solids may be transferred to the slurry storage tank 65 via pipe 56A branching off from pipe 56 to adjust the slurry concentration in the slurry storage tank.

The neutralization processing unit E is installed after the classification unit D, which prevents solidification due to the high pH of the suspended water and reduces production downtime for maintenance. Furthermore, by storing a large amount of suspended water in the pH adjustment tank 51, the concentration of suspended matter in the suspended water is made uniform, reducing variation in product quality.

(Sedimentation and concentration section F)
The settling and thickening section F is supplied with suspended water whose pH has been adjusted in the neutralization treatment section E. The pH-adjusted suspended water is suspended water in which fine solids are dispersed, and a flocculant is added in the settling and thickening section F before the water is sent to a settling device, where the flocculated suspended matter in the water is allowed to settle by gravity, separating the water into settled sludge and supernatant water. Various thickeners, such as circular thickeners and square thickeners, can be used as the settling device. The flocculant can be selected appropriately from inorganic flocculants, polymer flocculants, and the like.

Figure 7 is an enlarged view showing the configuration of the settling thickening section F when a rectangular thickener 57 is used as a settling separation device that adds a polymer flocculant and performs settling separation. The settling thickening section F includes a polymer dissolution tank 58 and a rectangular thickener 57. The polymer dissolution tank 58 stores the polymer flocculant in an agitated state. The polymer flocculant is injected from the polymer dissolution tank 58 into pipe 56 via pipe 59 by a metering pump P9. The polymer flocculant is mixed with the suspended water, the pH of which has been adjusted in the pH adjustment tank 51, in pipe 56 and then supplied to the rectangular thickener 57. The rectangular thickener 57 is a settling thickening tank equipped with a discharge screw 60 at its bottom. The suspended particles in the suspended water are flocculated by the polymer flocculant to form flocculated particles with a high settling velocity. These particles are then sedimented, concentrated, and separated by gravity, and deposited as thickened sludge at the bottom of the rectangular thickener 57. The thickened sludge is scraped around the intake port of the discharge pump P10 by the discharge screw 60, and is then transferred as concentrated suspended water by the discharge pump P10 through a pipe 61 installed at the discharge port at the bottom of the rectangular thickener 57 to a slurry storage tank 65 (described below). An overflow weir 62 is installed above the rectangular thickener 57, and clarified water overflows and is supplied to the circulating water tank 84 via a waterway 63.

(Slurry storage tank G)
FIG. 8 is an enlarged view showing the configuration of the slurry storage tank section G. The slurry storage tank section G includes a slurry storage tank 65 equipped with an agitator 64. Thickened sludge separated and settled in the square thickener 57 is supplied to the slurry storage tank 65 via pipe 61. A portion of the pH-adjusted suspension water may also be supplied via pipe 56A to adjust the slurry concentration. The slurry storage tank 65 is agitated by the agitator 64 to prevent the thickened sludge from settling and accumulating, maintaining the thickened sludge in a uniform state. While any agitator 64 may be used as long as it can agitate the thickened sludge without settling or accumulating, a preferred agitator 64 is shown in FIG. 8 , in which a motor M4 drives a rotating shaft 67 equipped with an agitator blade 66. The thickened sludge in the slurry storage tank 65 is supplied to the liquefied soil production section H via pipe 68 by a discharge pump P11, where it is used to produce liquefied soil. The excess concentrated sludge that is not used to produce liquefied treated soil is transferred to the dewatered sludge tank via pipe 68A branching off from pipe 68. The slurry storage tank 65 is also equipped with an agitation pump P12 and pipe 69, which circulates and agitates the slurry to prevent adhesion and solidification within the slurry storage tank.

(Fluidization treated soil production section H)
Figure 9 is an enlarged view showing the configuration of the fluidized soil production unit H. The fluidized soil production unit H includes a solidification material silo 70, a solidification material supply conveyor 71, a fluidization mixer tank 72, and a fluidized soil pit 73. The fluidization mixer tank 72 is a tank for producing fluidized soil. The fluidization mixer tank 72 receives the concentrated sludge from the slurry storage tank 65, the sludge to be treated in the mixing chamber 23 of the sludge receiving unit B, and the solidification material stored in the solidification material silo 70. The solidification material can be cement, a cement-based solidification material, lime, or the like, but cement is typically used. The solidification material is transported from the solidification material silo 70 to the fluidization mixer tank 72 by a solidification material supply conveyor 71. The solidification material supply conveyor 71 can be any type of conveyor, but a screw conveyor is preferred because it allows for easy adjustment of the input amount. Concentrated sludge from the slurry storage tank 65 is supplied via pipe 68 by discharge pump P11, and sludge from the agitation chamber 23 of the sludge receiving section B is supplied via pipe 27 by discharge pump P4. The concentrated sludge and solidification material introduced into the fluidization mixer tank 72 are mixed by agitator 74 to produce a slurry of fluidized treated soil. While agitator 74B alone may be used, a small agitator 74A is preferably installed below the water surface where the solidification material is introduced. The agitator 74A allows the solidification material remaining on the surface of the introduced muddy water to be mixed into the muddy water. If the concentration of the fluidized treated soil needs to be adjusted, dilution water can be supplied to the fluidization mixer tank 72 via pipe 87A by dilution pump P16 in the circulating water tank 84. The produced fluidized treated soil is transported via pipe 75 to the fluidized treated soil pit 73 for storage. It is preferable to transport the liquefied treated soil by placing the fluidization mixer tank 72 at a higher position than the liquefied treated soil pit 73 and allowing the liquefied treated soil to fall naturally.

(Dehydration part I)
FIG. 10 is an enlarged view showing the configuration of the dewatering unit I. The dewatering unit I is composed of a dewatered sludge tank 88, a filter press 76, a filtration tank 77, a neutralization tank 78, and other components. In the dewatering unit I, thickened sludge transferred from the slurry storage tank 65 via pipes 68 and 68A and sludge transferred from the agitation chamber 23 of the sludge receiving unit B via pipe 27 are supplied to the dewatered sludge tank 88. In the dewatered sludge tank 88, an agitator 89 agitates the sludge to prevent it from settling and accumulating, maintaining the thickened sludge in a uniform state and storing it. The agitator 89 may be any agitator capable of agitating the thickened sludge to prevent it from settling and accumulating. However, the agitator of the type used in the slurry storage tank 65 is preferably used. The sludge in the dewatered sludge tank 88 is supplied to the filter press 76 via pipe 90 equipped with a discharge pump P17, where it is separated into filtrate and dewatered cake. The filtrate is collected in a filtration tank 77, from which a portion is returned by a discharge pump P13 to a circulating water tank 84 via an installed pipe 79 and used to wash the ball mill 28, while the remainder is transferred via an installed pipe 80 to a neutralization tank 78. In the neutralization tank 78, the pH is adjusted to a pH of 5.8 to 8.6, which is the discharge standard based on the Water Pollution Control Act, and then the dehydrated cake is discharged via a pipe 81 by a discharge conveyor P14. The dehydrated cake is transported by an output conveyor 82 and an output conveyor 83 and stored, after which it is used as improved soil or discarded.

As described above, the construction sludge treatment device 1 can be used to implement an embodiment of the construction sludge treatment method. That is, the construction sludge treatment method according to this embodiment is a construction sludge treatment method for regenerating construction soil and construction sludge into recycled sand and fluidized soil, and includes a soil receiving process in which construction soil is delivered to soil receiving section A, a sludge receiving process in which construction sludge is delivered to sludge receiving section B, a crushing process in which the construction soil delivered in the soil receiving process and the construction sludge delivered in the sludge receiving process are crushed in crushing section C, and a classification process in which the material to be treated after being crushed in the crushing process is separated into recycled sand and suspended water. the suspension water separated in the classification step; a neutralization step in the neutralization treatment unit E, in which a neutralizing agent is added to neutralize the suspension water separated in the classification step; a sedimentation and concentration step in the settling and thickening unit F, in which a flocculant is added to the suspension water neutralized in the neutralization step to flocculate suspended matter in the suspension water and obtain concentrated suspension water; and a liquefied treated soil production step in the slurry storage tank unit G, liquefied treated soil production unit H, and dewatering unit I, in which a solidifying agent is added to the suspension water concentrated in the settling and thickening step to produce slurry-like liquefied treated soil.

In this embodiment of the construction sludge treatment method, by providing a neutralization treatment section before the settling and thickening section, scaling is less likely to occur on the wall surfaces, agitator blades, and piping, even when the incoming sludge contains a lot of calcium and has a high pH. This reduces production downtime due to maintenance to remove the scale and prevents piping blockage. Furthermore, even if the pH fluctuates due to differences in the calcium content of the incoming mud, fluctuations in the amount of solidifying agent added can be reduced, preventing deterioration in the performance of the liquefied soil and stabilizing the performance of the liquefied treated soil.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and improvements are possible without departing from the spirit of the present invention. It goes without saying that all or part of the components of each of the above-described embodiments can be combined as appropriate, provided that they are not inconsistent.

The construction sludge treatment device and construction sludge treatment method of the present invention can recycle construction sludge and muddy water, which are industrial waste, into slurry-like fluidized soil and sand (general-purpose sand, plastering sand, etc.) that can be used as backfill material, etc.

A Soil receiving section B Sludge receiving section C Crushing section D Classification section D1 First classification section D2 Second classification section E Neutralization treatment section F Settling and thickening section G Slurry storage tank section H Fluidized treated soil production section I Dewatering section M1 to M4 Motor P1 Agitation type sand pump P2 to P6, P8, P10 to P15, P17 Discharge pump P7, P9 Metering pump P16 Diluted water pump S1, S2 Cyclone 1 Construction sludge treatment device 2A Soil pit 2B Rubble pit 3 Inclined sieve 4 Magnetic sieve 5 Transfer conveyor 6 Soil to be treated 7 Backhoe 8, 9 Transfer means 10A, 10B Transfer vehicle 11 Raw mud pit 11A First raw mud pit tank 11B Second raw mud pit tank 11C Partition wall 12 Sand divider 13 Vibrating sieve 14 Adjustment tank 15, 16, 18, 19, 20 Pipe 17 Transfer means 21 Partition wall 22 Settling chamber 23 Stirring chamber 24 Stirring blade 25 Rotating shaft 26, 27 Pipe 28 Ball mill 29 Receiving section for material to be treated 30 Ball mill main body 31 Sieving means 32 Overtank 33 Spiral classifier 34 Pit 35 Screw conveyor 36 Water-removing vibrating sieve 37 Raw water pit 38 Belt conveyor 39 Sand yard 40 Stirring device 41 Stirring blade 42 Rotating shaft 43, 44, 45 Pipe 46 Water-removing vibrating sieve 47 Belt conveyor 48 Sand yard 49 Pipe 50 Dilute sulfuric acid tank 51 pH adjustment tank 51A Suspended water receiving pit 51B Adjustment mixing tank 51C Partition wall 52 Mixing device 53 Pipe 54 Mixing plate 55 Rotating shaft 56, 59, 61 Pipe 57 Square thickener 58 Polymer dissolution tank 60 Discharge screw 62 Overflow weir 63 Waterway 64 Mixing device 65 Slurry storage tank 66 Mixing plate 67 Rotating shaft 68, 69 Pipe 70 Solidification material silo 71 Solidification material supply conveyor 72 Fluidization mixer tank 73 Fluidization treated soil pit 74, 74A, 74B Mixing device 75 Pipe 76 Filter press 77 Filtration tank 78 Neutralization tank 79, 80, 81 Pipe 82, 83 Discharge conveyor 84 Circulating water tank 85 Pipe 86 Flow path 87A, 87B Pipe 88 Dewatered sludge tank 89 Agitator 90 Pipe

Claims (5)

A construction sludge treatment device that regenerates construction soil and construction sludge into reclaimed sand and liquefied treated soil,
a soil receiving section into which construction soil is transported;
a sludge receiving section into which construction sludge is carried;
a crushing unit that crushes the construction soil and sand carried into the soil receiving unit and the construction sludge carried into the sludge receiving unit;
a classification unit that separates the material to be treated after being crushed by the crushing unit into recycled sand and suspended water;
a neutralization processing unit that adds a neutralizing agent to the suspended water separated by the classification unit to neutralize the suspended water;
a sedimentation and concentration section in which a flocculant is added to the suspended water neutralized in the neutralization section to flocculate suspended matter in the suspended water, thereby obtaining a concentrated suspended water and clarified water;
a fluidized-treated soil production unit that adds a solidification material to the suspended water concentrated in the sedimentation concentration unit to produce a slurry of fluidized-treated soil;
a dehydration section for separating the suspension water concentrated in the sedimentation concentration section into a filtrate and a dehydrated cake;
a circulating water tank to which the clarified water obtained in the sedimentation thickening section, the filtrate separated in the dehydration section, and makeup water are supplied, and which supplies water to the disintegration section,
The construction sludge treatment apparatus is characterized in that the crushing unit includes a ball mill, and the water from the circulating water tank, the construction soil and sand, and the construction sludge are supplied to the ball mill. The construction sludge treatment device described in claim 1, characterized in that the sludge receiving unit includes a raw sludge pit for storing the construction sludge and a sand divider for separating the construction sludge into solids and suspended liquid, and the sand divider includes a vibrating screen, a cyclone, and an adjustment tank. The construction sludge treatment device described in claim 1, characterized in that the classification section includes a spiral classifier, a vibrating sieve for draining, and a cyclone. The construction sludge treatment device described in any one of claims 1 to 3, characterized in that the recycled sand is sand particles with an average particle size of 0.74 mm to 2 mm. A construction sludge treatment method for regenerating construction soil and construction sludge into reclaimed sand and liquefied treated soil, comprising:
a soil receiving process in which construction soil is transported;
a sludge receiving process in which construction sludge is transported;
a crushing step of crushing the construction soil and sand delivered in the soil receiving step and the construction sludge delivered in the sludge receiving step;
a classification step of separating the material to be treated after being crushed in the crushing step into recycled sand and suspended water;
a neutralization treatment step of neutralizing the suspension separated in the classification step by adding a neutralizing agent;
a sedimentation and concentration step in which a flocculant is added to the suspended liquid neutralized in the neutralization treatment step to flocculate suspended matters in the suspended liquid, thereby obtaining a concentrated suspended liquid and clarified water;
a fluidized-treated soil production step of adding a solidification material to the suspension water concentrated in the sedimentation concentration step to produce a slurry of fluidized-treated soil;
a dehydration step of separating the suspension water concentrated in the sedimentation concentration step into a filtrate and a dehydrated cake;
a circulating water step in which the clarified water obtained in the sedimentation and concentration step, the filtrate separated in the dehydration step, and makeup water are supplied to a circulating water tank, and the water in the circulating water tank is supplied to the disintegration step, and then circulated to the circulating water tank via the classification step, the neutralization treatment step, and the sedimentation and concentration step or via the classification step, the neutralization treatment step, the sedimentation and concentration step, and the dehydration step,
A construction sludge treatment method, characterized in that the crushing step includes a ball mill, and the water from the circulating water tank, the construction soil and the construction sludge are supplied to the ball mill.