JP2002254099A - Recovering method of fine powder of concrete sludge, device therefor and fine powder of concrete sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover the fine powder of concrete sludge which is good in quality and suitable for recycling by removing fine sand contained in wastewater formed by washing as much as possible. SOLUTION: The fine powder 15 contained in the wastewater 10 formed by washing in concrete treating facilities is removed so that a sand content can become 10 mass % or below (S1), and an inorganic flocculant 18 is added to the recovered water 16 thus obtained to separate supernatant water 19 of the recovered water and the sludge water (S2) from the recovered water. Then, the separated sludge water is dehydrated to form dehydrated cake 23 (S3), the dehydrated cake 23 is ground before hardened (S4) and rolled flatly in thickness of 10 to 15 mm, and the ground dehydrated cake is dried so as to achieve a water content of 50 to 60 mass % and its maximum particle size of at most 20 mm (S5), the dried sludge 26 thus obtained is finely ground with a grinding device 27 making use of wind power to produce fine and round particles (S6), and then the fine powder PDS of the concrete sludge is recovered by collecting the fine particle thus produced (S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to dry concrete sludge fine powder (PDS: Pulver) from wastewater generated from fields related to civil engineering such as construction sites, concrete product factories, ready mixed factories and crushed stone factories.
TECHNICAL FIELD The present invention relates to a method and an apparatus for collecting fine sludge of concrete sludge for collecting dried slurry.

[0002]

2. Description of the Related Art Concrete structures are widely used in Japan.
It was first built in 1982 and has been around for over 100 years. In the last few years, the time has come for rebuilding or remodeling and expansion of buildings, and there is a growing movement to recycle dismantled concrete blocks.

[0003] "Waste Disposal and Cleaning Law",
Construction waste materials, which are listed as one of the five stable items among industrial waste classified by the so-called Waste Disposal Law, promote effective use in the "Law Concerning the Use of Recycled Resources", the so-called Recycling Law. In addition, it is designated as a by-product whose quality should be devised so as to increase the recycling rate.

[0004] On the other hand, the situation of environmental measures on the side of supplying concrete is far behind. A common environmental problem for factories that supply concrete is the solid content in the wastewater from the washing of mixers and agitator trucks, as well as the wastewater from the processing of residual concrete and returned concrete (sand and gravel are collected and reused. Processing).
In the above-mentioned waste treatment method, the solid content called concrete sludge belongs to the category of sludge, and it is stipulated that when it is disposed of, it is disposed of in a managed landfill site. However, it is difficult to stably secure such a managed disposal site in the future from the viewpoint of cost and location conditions, and various methods for effectively utilizing sludge without discarding it have been proposed. Above all, the technology of drying and pulverizing sludge has attracted attention as a practical technology because of the wide range of use of the obtained granular sludge.

For example, Japanese Unexamined Patent Publication (Kokai) No. 7-315971 discloses that a raw dehydrated cake having a solid content of 20 to 70% by mass is dehydrated by a dehydrator such as a filter press or dried by solar drying or the like. Add water, waste water from a concrete plant, etc., mix and stir evenly with a mixer, dry granulate with a spray drier, and granulate or spherical with an average particle size of 50-100 μm. A method is disclosed in which sludge granules having excellent handling properties without waste are reused as silicate lime fertilizer.

[0006] Japanese Patent Application Laid-Open No. 9-217343 discloses that sludge separated from aggregate of remaining ready-mixed concrete contains 3 sludges.
After elapse of a predetermined curing time, the active dehydrated cake obtained by dehydration within 4 hours is granulated by a granulator to form a granular cake, which is cured for a predetermined number of days in a storage area of a canopy to obtain a water content of 22%. Drying and pulverizing processes are carried out to obtain a powder having a water content of 5 to 6% or less and a particle diameter of 0.15 mm or less. A reusing method for mixing in mud is disclosed.

Further, the present inventors have developed a technology for producing a dried sludge by pulverizing a dewatered cake having a water content of 30% or less by a drying treatment at the time of generation of raw con sludge with a wind pulverizer using a swirling air flow. Developed (Symposium on Effective Use of Concrete Sludge Proceedings 199
6.5). The powder and granules crushed by this wind crusher are J
IS R5201 Fine particles having a specific surface area of about 6800 cm ² / g according to the physical test method of cement can be used as a ready-mixed concrete admixture, a void filler, a lightweight embankment material, a soil improvement material, and the like.

[0008] As described above, by drying and granulating the raw consludge, the range of reuse of the raw consludge is also expanding. However, in the above-mentioned conventional methods for drying and granulating raw sludge, the efficiency of dewatering or drying the sludge is low, and the particle size of the obtained granules is limited.

In the method described in Japanese Patent Application Laid-Open No. 7-315971, since the sludge is dehydrated by a dehydrator or solar drying, it can be dehydrated only up to a water content of about 50%. Since the granules having the above-mentioned ratio are dried and granulated by a spray dryer, the granulated granules having an average particle size of only about 50 to 100 μm can be obtained.

According to the method described in JP-A-9-217343, it takes a long time to cure the dehydrated cake and the granular cake, and it is only possible to obtain a powdered or granular material having a particle size of about 150 μm or less. .

Also, in the method described in the above-mentioned collection of papers, the drying of sludge is simply performed by blowing hot air, so that the dewatered cake at the stage of being introduced into a wind pulverizer has a particle size of about 30 to 50 mm. Are relatively large, and the powder and granules obtained by the wind pulverizer have an average particle size of 10 to 20.
Only about μm can be obtained.

In order to solve such a problem, the present inventors have previously settled and separated sludge slurry generated in a ready-mixed concrete manufacturing plant or the like, dried and pulverized the sludge, and formed a powdery granular sludge. A method of treating sludge, wherein the sludge after the sedimentation and separation is dewatered to a water content of 60% or less, and the dewatered sludge is dried to a water content of 20% or less by hot air drying and a particle size of 15 mm or less during drying. A drying and pulverizing step of pulverizing, a pulverizing step of pulverizing the dried sludge after the drying and pulverizing step by a wind pulverization using a swirling air stream to a particle size having a Blaine specific surface area of 7000 cm ² / g or more; And a collecting process for collecting the powdery and granular sludge of the present invention was proposed and filed (Japanese Patent Application No. 11-194749).

[0013]

By the way, the fine sand content contained in the washing wastewater, when analyzing the chemical components of the recovered water,
An amount detected as an insoluble residue (Insol.),
In particular, it has been pointed out that, when a large amount of mud is contained, the properties of the concrete may be adversely affected if water containing the same is mixed and reused as water to produce concrete. Therefore, according to JIS regulations (JIS A 5308), the amount of sludge solid content is 3% by mass per unit cement.
However, if fine sand that is an impurity can be removed at the stage of treatment of washing wastewater, the sand content is low.
High quality recovered water can be obtained and can be used as unused resources.

However, in the above-mentioned method for treating sludge according to the above-mentioned application, no consideration is given particularly to the removal of fine sand, and it is not possible to obtain recovered water having a low sand content.

An object of the present invention is to remove fine sand contained in washing wastewater as much as possible and to recover high quality concrete sludge fine powder suitable for reuse.

[0016]

Means for Solving the Problems To solve the above problems, a method for recovering concrete sludge fine powder according to the present invention comprises:
A fine sand removal step of obtaining recovered water by removing fine sand contained in washing wastewater generated from concrete treatment facilities such as a concrete product factory and a ready mixed factory so that the sand content is 10% by mass or less; A coagulation sedimentation step in which an inorganic coagulant is added to the recovered water obtained in the sand removal step to separate and precipitate the collected water supernatant water and sludge water; and a sludge water separated in the coagulation sedimentation step is dewatered to be dehydrated. A dewatering process for producing a cake, a dewatering cake obtained in the dewatering process is crushed before curing, and a crushing process for flat rolling to a thickness of 10 to 15 mm; A drying step of drying the crushed dewatered cake so that the water content is 50 to 60% by mass and the maximum particle size is 20 mm or less, and the dried sludge obtained in this drying step is finely pulverized by a pulverizer using wind power. A pulverizing step for producing microparticles rounded and 砕化 a concrete sludge powder recovery method comprising the collecting step of collecting the fine particles produced by this grinding process.

Further, the concrete sludge fine powder recovery apparatus of the present invention has a sand content of 10% by mass or less of fine sand contained in washing wastewater generated from concrete treatment facilities such as a concrete product factory and a ready mixed factory. A fine sand removal means such as a wet cyclone to obtain the recovered water removed as above, and an inorganic coagulant added to the recovered water obtained by the fine sand removal means to separate and precipitate the recovered water supernatant water and sludge water. Precipitation means, a dewatering treatment means for producing a dewatered cake by dewatering the sludge water separated by the coagulation sedimentation means, and a dewatered cake obtained by this dewatering treatment means is crushed before curing to 10 to 15 mm And a dewatered cake crushed by the crushing means having a water content of 50 to 60% by mass and a maximum particle size of 20 mm.
Drying means for drying as follows, and fine pulverizing means for finely pulverizing the dried sludge obtained by this drying means with a pulverizing device using wind power to produce rounded fine particles,
A concrete sludge fine powder collecting apparatus including a collecting means for collecting fine particles produced by the fine pulverizing means.

According to the present invention, the component is CaO 30-40
%, SiO ₂ 10 to 20% by mass, average particle size 3 to 20 μm, specific surface area 4000 to 30000 cm ²
/ G, a high-quality concrete sludge fine powder (PDS) exhibiting the shape of rounded and rounded particles can be obtained, which can be mixed with a concrete admixture material, a powder material for high-fluidity concrete, Self-leveling material, air mortar, ground improvement material, and because it is alkaline, it can be used for a wide variety of applications such as neutralizers. Concrete sludge in the category of industrial waste sludge as PDS A recycling technique is provided.

The water content ratio used in the present specification is represented by the following formula: water content ratio = (initial mass−mass in absolutely dry state) / initial mass × 100 (%). On the other hand, the water content commonly used together with the water content ratio is represented by: water content = (initial mass−mass in absolutely dry state) / mass in absolutely dry state × 100 (%). Both can be converted by the following formula. Water content = water content / (water content + 1)

[0020]

Embodiments of the present invention will be described below. FIG. 1 is a process diagram showing the processing steps of the present invention, and FIG. 2 is a schematic diagram showing the configuration of the processing apparatus of the present invention. The process will be described with reference to the process diagrams and schematic diagrams.

S0: Aggregate recovery treatment In order to produce high-quality PDS, it is important to treat the washing wastewater 10, which is the first step, and use an aggregate recovery apparatus 11 such as a trommel or a sand screw in a preliminary stage. To remove large-size gravel, sand, etc. from the washing wastewater 10 and collect recovered aggregate 1
2, and the supernatant 13 is separated.

S1: Fine sand removal treatment Further, the fine sand content 15 contained in the supernatant liquid 13 is removed as much as possible using a wet cyclone 14 to obtain a sand content of 10%.
Mass% or less, preferably about 5% or less. The sand content in the ready-mixed concrete factory varies greatly depending on the factory in each region, and is in the range of 5 to 35% by mass. If the sand content exceeds 10% by mass, the concrete properties may vary greatly when producing concrete using sludge water containing the same, and when the concrete contains a large amount of mud, the concrete may become fresh. It has been pointed out that it adversely affects the properties. In order not to adversely affect the properties of the concrete, it is necessary to remove the fine sand contained in the washing wastewater as much as possible, and the sand content is reduced to 10% by mass or less. By this treatment, high-quality recovered water 16 is obtained.

In the wet cyclone 14, the washing wastewater containing fine sand is continuously passed through the conical side plate under pressure from the pump. The washing wastewater maintaining the speed passes through the inclined plate while rotating, and at this time, the heavy wastewater with the specific gravity rotates along the outer plate side while increasing the speed near the discharge port. If a negative pressure can be applied to the central part in this state, the washing wastewater having a low specific gravity can be pushed upward, and if the upper central hole is opened without load, sewage containing no fine sand can be discharged. As a result, the fine sand can be discharged from the lower part. The flow rate that generates a negative pressure in the central portion and the angle of the inclined plate that increases the rotation speed depend on the setting of the discharge port diameter.
If the wet cyclone is formed in a continuous layer type, the negative pressure can be amplified, and the fine sand removal rate can be further increased.

S2: Coagulation-sedimentation treatment The coagulation-sedimentation apparatus 17 is used to separate the recovered water of high quality into supernatant water 19 and sludge water. A coagulant is used in this treatment step in order to prevent solidification of the solids contained in the sludge water, to quickly separate the sludge, and to reuse the supernatant water 19 as mixing water for concrete. As a coagulant, a processing technology using a polymer-based coagulant has been developed and used, but it requires time until coagulation and sedimentation. Will be needed. In addition, the aggregates are sticky and difficult to reuse. Further, the solid content in the recovered water precipitates in a floc state, but the solid content contains a large amount of unhydrated cement, and is not hardened in water and retains the activity of the cement. If this is mixed into concrete, it can be expected to increase the strength. In the present invention, from the viewpoint of reusing treated water as a concrete material, an inorganic coagulant 1 that is harmless to the properties of concrete
8 (95% by mass or more, preferably 98% by mass or more) is indispensable. If the inorganic content is less than 95% by mass, the organic component may adversely affect the properties of the concrete, which is not preferable. As the inorganic coagulant 18, aluminum salts, calcium salts, and magnesium salts can be used. The sludge water separated by the coagulation sedimentation device 17 is settled in the concentration tank 20, and the supernatant water is supplied to the raw water tank 21.

S3: Dehydration treatment Sludge water supplied from the raw water tank 21 is supplied to the dehydration treatment device 2
Dewatering process 2 and dewatering cake 23 (sludge cake)
Is prepared. As the dehydration processing device 22, a dehydrator such as a filter press can be used.

S4: Disintegration treatment The dewatered cake 23 produced by the dehydration treatment S3 has a water content of about 50% by mass, so that it is hardened if left as it is, and only the surface is dried. Is very difficult to pulverize. Therefore, after the dehydrated cake 23 is prepared, it is immediately crushed by the crusher 24 to loosen it roughly. Such a process is an indispensable step for producing high-quality PDS. The crushing process is performed by flat rolling the dehydrated cake 23 to a thickness of 10 to 15 mm through rollers between the first crushing and flat rolling between the rollers before the drying process in the next secondary crushing.

S5: Drying Process The loosened dewatered cake is processed, for example, by a circulating belt conveyor dryer 25. In order to produce high-quality PDS, the water content is 10 to 30% by mass. It is indispensable to produce the dry sludge 26 which is preferably about 20% by mass and has a maximum particle size of 20 mm or less, preferably about 15 mm. At this time, the dryer 25 must be capable of providing uniform drying.
When the water content is more than 30% by mass, the dry sludge containing a large amount of moisture has a short time in the next step in the wind-type pulverizer 27 due to the action of gravity, so that only a powder having a large particle diameter can be obtained. There is a possibility that a very fine powder can be produced by adjusting the water content to less than 10% by mass,
Because it leads to an increase in the cost of the drying process and can produce the desired fine powder with a water content of about 20% by mass,
The water content was in the above range. The maximum particle size is 30mm
If it exceeds, the dried sludge becomes heavy, and the time required for the air crushing treatment is short due to the action of gravity, and only a powder having a large particle diameter can be produced, which is not preferable.

S6: Pulverization treatment The dried sludge 26 is pulverized by a wind-type pulverizer 27. The feature of this device is that angular particles can collide with each other in the wind to produce rounded fine particles. Conventionally, the cyclone method is often used for classification of powder, but can be used as a device mainly for pulverization by appropriately controlling the flow and flow rate of air flow, the amount of suction, the angle of the inclined plate, etc. .

S7: Collection Process In order to produce a high quality PDS 33, a well-known dry type cyclone 28 and a system in which a collector 30 is systemized in addition to the wind-type pulverizer 27 are used. The aforementioned wind mill 2
7 and the material separated by the dry cyclone 28 are transferred to a sieve 29, and powder particles having a particle diameter smaller than a certain particle size are sucked by a suction auxiliary device 31 and collected by a suction adjusting and collecting device 32.
The powder particles larger than a certain particle size separated by the sieve 29 are again conveyed to the wind mill 27 and pulverized. This improves the recovery rate. In this way, a high-quality PDS having a fineness (specific surface area) of 4000 to 30000 cm ² / g can be obtained. Table 1 shows the characteristics of the PDS of the present invention, such as the results of component analysis, along with Comparative Examples.

[0030]

[Table 1] Characteristics of PDS OPC: ordinary Portland cement PDS: finely ground dry sludge

FIG. 3 shows a micrograph showing the shape of each sample. As can be seen from Table 1 and FIG. 3, the PDS of the present invention has a rounded shape with sharp corners and a particle size smaller than the particle size distribution of concrete. When used, concrete is mixed with concrete in a state of filling gaps between cement particles, and a dense concrete product or structure can be constructed.

[0032]

As described above, according to the present invention, the following effects can be obtained. (1) By removing the fine sand content contained in the washing wastewater as much as possible, high-quality concrete sludge fine powder suitable for reuse can be recovered. (2) The recovered concrete sludge fine powder can be reused as a powder material for high-fluidity concrete, a self-leveling material, an air mortar, and a ground improvement material. (3) Since the recovered concrete sludge fine powder is alkaline, it can be used for various expanded applications such as neutralizers, and concrete sludge in the category of industrial waste sludge is recycled as PDS. Can be turned into resources.

[Brief description of the drawings]

FIG. 1 is a process chart showing the processing steps of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a processing apparatus of the present invention.

FIG. 3 is a micrograph showing the shape of each sample.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wash wastewater 11 Aggregate collection device 12 Collected aggregate 13 Supernatant liquid 14 Wet cyclone 15 Fine sand 16 Collected water 17 Coagulation sedimentation device 18 Inorganic coagulant 19 Supernatant water 20 Concentration tank 21 Raw water tank 22 Dehydration treatment device 23 Dehydration cake 24 Crusher 25 Dryer 26 Dry sludge 27 Wind-type pulverizer 28 Dry cyclone 29 Sieve 30 Collector 31 Suction auxiliary device 32 Suction adjustment collector 33 Fine pulverized dry sludge (PDS)

Claims (4)

[Claims] 1. Fine sand removal to obtain recovered water by removing fine sand contained in washing wastewater generated from concrete treatment facilities such as a concrete product factory and a ready mixed factory so that the sand content is 10% by mass or less. A coagulation sedimentation step of adding an inorganic coagulant to the recovered water obtained in the fine sand removal step and separating and precipitating the collected water supernatant water and sludge water; and A dewatering treatment step of producing a dewatered cake by dehydration treatment; a crushing treatment step of crushing the dewatered cake obtained in the dewatering treatment before curing and flat rolling to a thickness of 10 to 15 mm; The dewatered cake crushed in the crushing process has a water content of 5
A drying step of drying so that the maximum particle size is 20 mm or less at 0 to 60% by mass, and finely pulverizing the dried sludge obtained in this drying step with a pulverizer using wind power to produce rounded fine particles. And a collecting step of collecting the fine particles produced in the fine pulverizing step. 2. Fine sand removal to obtain recovered water by removing fine sand contained in washing wastewater generated from concrete treatment facilities such as a concrete product factory and a ready mixed factory so that the sand content is 10% by mass or less. Means, an inorganic coagulant is added to the recovered water obtained by the fine sand removing means, and a coagulating sedimentation means for separating and precipitating the collected water supernatant water and sludge water; and a sludge water separated by the coagulating sedimentation means. A dewatering treatment means for producing a dewatered cake by performing a dehydration treatment; a crushing treatment means for crushing the dewatered cake obtained by the dehydration treatment before curing and flat rolling to a thickness of 10 to 15 mm; The dewatered cake crushed by the crushing means has a water content of 5
Drying means for drying so that the maximum particle size is 20 mm or less at 0 to 60% by mass; and drying sludge obtained by the drying means is finely pulverized by a pulverizer using wind power to produce rounded fine particles. A concrete sludge fine powder recovery device, comprising: a fine pulverizing means for collecting fine particles produced by the fine pulverizing means; 3. The concrete sludge fine powder collecting apparatus according to claim 2, wherein the fine sand removing means is a wet cyclone. 4. A composition comprising 30 to 40% by mass of CaO and SiO
Containing _{2 to} 20% by mass, having an average particle size of 3 to 20 μm,
Fine concrete sludge powder having a specific surface area of 4000 to 30000 cm ² / g and having the shape of rounded particles with sharp corners.