JP4150234B2 - Sludge water treatment method for ready-mixed concrete - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for dewatering sludge water containing cement discharged after collecting aggregates such as gravel and sand from a raw concrete kneading facility and a remaining raw concrete processing step using a dehydrator. is there.
[0002]
[Prior art]
In the concrete mixing facility, sludge water containing cement such as washing water from the mixing facility and runoff from the ready concrete is discharged. In addition, in the processing process of ready-mixed concrete that is not used at concrete product factories and construction sites, sludge water containing cement after the collection of aggregates such as gravel and sand from ready-mixed concrete is similarly discharged. .
[0003]
The sludge water containing the cement is temporarily stored in the sludge tank and sent to a dehydrator such as a filter press to solidify the cement as a dehydrated cake and dehydrate it to make it stable. The treated water filtered by is stored in the treated water tank and reused as washing water and kneaded water in the facility, and the surplus treated water is discharged to the outside after adjusting the water quality such as pH value.
[0004]
Sludge water is dehydrated by placing the sludge water in the sludge tank in a static state for a certain period of time, allowing the cement contained in the sludge water to spontaneously settle, and not dewatering the sludge upper layer of the cement as it is. Then, the sludge water in which the cement in the lower layer is precipitated is sent to a dehydrator for dehydration treatment, and then sent to the treatment water tank.
This is performed in order to shorten the time required for the dewatering process as much as possible and to finish the dewatering process of the sludge water early.
[0005]
For example, when sludge water with a cement concentration of 3% is stored in a sludge tank with a capacity of 60 m ³ and placed in a static state for 3 hours and allowed to settle naturally, about 4/5 of the total sludge water amount is 0.1% with a cement concentration of 0.1%. Dilute upper layer sludge water becomes about 1/5 of the sludge water precipitated in the lower layer. When the sludge water settled in this lower layer is dehydrated and filtered to a sludge water with a cement concentration of 0.001%, the treated water tank has a sludge water with a 4/5 cement concentration and a 1/5 cement concentration of 0. .001% sludge water is mixed and sludge water with a cement concentration of 0.08% is stored in the entire treated water tank.
However, when the sludge water is discharged to the outside of the facility, the cement concentration needs to be 50 ppm (0.005%) or less, and the above method cannot discharge the sludge water to the outside of the facility. Therefore, it is necessary to dehydrate all the sludge water in the sludge water tank to reduce the cement concentration of all sludge water.
[0006]
Therefore, in order to release the sludge water to the outside of the facility, the entire amount of sludge water in the sludge tank is sent to the dehydrator and dehydrated to a uniform cement concentration. However, if the cement concentration of the sludge water in the treated water tank is set to 0.001% so that it can be discharged to the outside of the facility, the sludge water dehydration process takes time and is discharged from the facility one after another. It is difficult to perform dehydration without accumulating sludge water.
[0007]
[Patent Document 1]
JP-A-7-195099 [0008]
[Problems to be solved by the invention]
Therefore, in view of the above problems, an object of the present invention is to perform a step of dehydrating all sludge water in a sludge water tank in a short time in a method of dewatering sludge water using a dehydrator.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a sludge water treatment method in which sludge water containing cement content discharged from a raw concrete kneading facility is dehydrated by a dehydrator. Calculating a correlation curve between the throughput and the cement concentration of sludge water, detecting a deflection point on the correlation curve where the dewatering amount of the dehydrator starts to increase rapidly as the cement concentration of the sludge water decreases; It comprises a first step of dewatering sludge water below the cement concentration at the deflection point, and a second step of stirring the sludge water above the cement concentration at the deflection point in a sludge water tank.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a correlation curve between the amount of dewatering per unit time and the cement concentration of sludge water of three types of dehydrators having different treatment capacities of the dehydrators.
According to the correlation curve A between the dewatering amount per unit time of the dehydrator shown in FIG. 2 and the cement concentration of sludge water, when the cement concentration of sludge water falls below a certain value, the dewaterer becomes smaller as the cement concentration of sludge water becomes smaller. A point a at which the dewatering capacity of the water increases dramatically is detected. (Hereinafter, the point a on the correlation curve will be referred to as a deflection point.) The sludge water having a cement concentration equal to or less than the cement concentration at the deflection point a can be dehydrated in a large amount in a short time.
[0011]
In the sludge water filtration step, the cement content is filtered by passing the sludge water through a filter cloth provided in the dehydrator to obtain treated water. The cement content filtered by the filter cloth adheres to the filter cloth, and the adhesion of the cement content to the filter cloth increases by continuing the filtration of sludge water. At first, the cement adhering to the filter cloth as a thin film gradually adheres to the filter cloth as a thick layer, which prevents the sludge water from being filtered.
For this reason, when sludge water having a low cement content is used, the amount of dewatering per unit time of the dehydrator is large because there is little adhesion to the filter cloth and it does not hinder the filtration. On the other hand, when sludge water with a high cement content is used, it adheres to the filter cloth, hinders filtration and reduces the amount of dewatering per unit time of the dehydrator.
[0012]
Further, the cement concentration of the sludge water in the water surface portion of the sludge water tank that is not agitated is a numerical value smaller than the cement concentration at the deflection point, even if the cement content is not settled for a certain period of time due to natural sedimentation of the cement.
The present invention pays attention to the above points, and sends sludge water on the surface of the sludge tank to the dehydrator. A large amount of sludge water with a low cement concentration is preferentially dehydrated, and the high dewatering capacity is utilized for a short time. The sludge water having a high cement concentration is filtered with a small amount, so that the sludge water in all the sludge water tanks is dehydrated to further reduce the processing time.
[0013]
The deflection point of the correlation curve will be described. In the example of the deflection point a in the correlation curve A of the dehydrator shown in FIG. 2, the tangent of the point on the correlation curve is a numerical value with a high cement concentration on the right side of the graph of FIG. The region shows a small angle inclination near the horizontal, which means that the dewatering capacity does not vary greatly even if the cement concentration varies.
When the cement concentration becomes gradually smaller, the tangential slope gradually becomes larger, and the deflection point a where the dewatering capacity of the dehydrator is dramatically increased when the cement concentration is reduced in the vicinity of the tangential slope being about 45 °. Is obtained.
At the point where the cement concentration is smaller than the deflection point a, the slope of the tangential line suddenly becomes a large inclination of 45 ° or more. In these regions, the lower the cement concentration, the higher the dewatering ability, and the dewatering treatment is efficiently performed. It can be carried out.
The deflection point is located near the 45 ° point, which is the neutral point between 0 ° and 90 ° of the tangent slope at the point on the correlation curve. The transition of fluctuates extremely.
[0014]
Examples of the present invention will be described below.
A water supply pump for sending sludge water to a dehydrator is provided in a sludge tank for storing sludge water discharged from a facility. A water absorption pipe that sucks up sludge water from the sludge tank into the water supply pump is provided from the sludge water tank to the water supply pump, and a float (floating device) is provided at the intake port provided in the water absorption pipe. The intake port is adapted to move up and down, and the sludge water on the water surface is taken in and sent to the dehydrator.
The sludge water tank is provided with a stirring means for stirring the sludge water, and all the concentrations in the sludge water tank can be made uniform by stirring.
The treated water dehydrated by the dehydrator is stored in a treated water tank, reused as washing water or kneaded water in the facility, and discharged to the outside after adjusting the water quality such as pH value.
[0015]
FIG. 1 shows a flowchart of the dehydration process of the present invention.
In the first step 1 of the sludge water dehydration treatment, the sludge water in the sludge tank is not placed in a static state where the cement content is settled, and the intake port is located at the water surface. Immediately sludge water on the water surface is taken in and sent to the dehydrator. At this time, in order to maintain the state where the sludge water on the water surface portion has a low cement concentration, the stirring means is not operated and the sludge water is not stirred.
By not stirring, the cement concentration of the sludge water on the water surface is below the deflection point a on the correlation curve A, and the dewatering process of the dehydrator has a high dewatering capacity, so that a larger amount of sludge water can be processed in a short time. It becomes possible.
[0016]
For example, the cement concentration of sludge water on the water surface when stirring is not performed in sludge water having an average concentration of 3% is about 0.5% due to natural sedimentation of the cement.
According to the correlation curve A between the dewatering amount of the dehydrator and the cement concentration of sludge water shown in FIG. 2, the cement concentration at the deflection point a in this graph is about 3%, and the cement concentration of sludge water in the water surface is 0%. .5% is a concentration lower than this, so that the dehydrator has a high dewatering capacity.
As the sludge water dehydration proceeds, the amount of water in the sludge tank decreases and the water level drops. In order to continue sending sludge water on the water surface part with low cement concentration to the dehydrator, the intake port is equipped with a float, and even if the water level fluctuates up and down, the intake port moves along the top and bottom of the water surface. Can be placed on the water surface.
[0017]
As another example of moving the intake port, the position of the water surface is judged using a sensor, and the intake port is moved up and down to the position of the water surface part by an electric chamber or winch, or the position of the water surface is operated. The operator confirms it visually and manually operates the chamber. In the above example, the intake port is provided in the water absorption pipe sucked up by the water supply pump, but without providing the water absorption pipe connecting the sludge water tank and the water supply pump, the water supply pump is provided in the sludge water tank, The same effect can be obtained even if the water pump itself is moved up and down in accordance with the movement of the water surface by using a float or a chamber as in the above example using the mouth as an inlet.
[0018]
In the second step 2, when the amount of water in the sludge tank decreases, the cement concentration of the remaining sludge water increases, the cement concentration of the sludge water on the water surface approaches the deflection point a, and when the cement concentration increases, the dewatering capacity increases greatly. It will drop to.
Therefore, the sludge water is agitated by the agitation means provided in the sludge water layer to equalize the cement concentration of the sludge water in the water tank without extremely increasing it, and the sludge water is sent to the dehydrator while preventing the dewatering capacity from being lowered.・ Dehydrate all sludge water.
In addition, stirring the sludge water can also prevent deterioration in workability due to solidification of the cement component generated by increasing the cement concentration and adhesion to the water tank.
[0019]
In each correlation curve shown in FIG. 2, the amount of sludge water treated per unit time varies depending on the treatment capacity of each dehydrator, and the cement concentration at the deflection point of each correlation curve differs. This is because there is a difference in the surface area of the filter cloth for filtering the sludge water provided in each dehydrator due to the difference in the treatment capacity of each dehydrator. In the correlation curve C of the dehydrator having a large treatment capacity, the surface area of the filter cloth is also In the correlation curve A of a dehydrator having a large processing capacity, the filter cloth has a small surface area. For this reason, since the amount of the cement part filtered with a filter cloth each differs, a difference arises in the sludge water treatment amount per unit time, and the position of the deflection point also differs. For example, the cement concentration at the deflection point a in the correlation curve A of the dehydrator with a processing capacity of 78 L is 3%, and the cement concentration at the deflection point b in the correlation curve B of the dehydrator with a processing capacity of 138 L is 4%. The cement concentration at the deflection point c in the correlation curve C of the dehydrator with a capacity of 230 L is 5.5%, and the numerical value of the deflection point can vary depending on the processing capacity of each dehydrator.
[0020]
Through the above steps, sludge water can be dehydrated with respect to all sludge water, and treated water with a low cement concentration can be obtained. In addition, all sludge water can be dehydrated in a short time.
[0021]
【The invention's effect】
As described above, according to the present invention, since the sludge water in all the sludge water tanks is dehydrated, treated water having a low cement concentration can be obtained.
In addition, sludge water with a low cement concentration is dehydrated as the first step at the beginning of the dewatering process, so the initial dewatering capacity of the dewatering process is large and a large amount of sludge water can be treated, and the treated water is needed quickly. Sometimes we can respond urgently.
Similarly, since the initial dewatering amount of the sludge water is large, it is possible to easily cope with the sudden generation of sludge water, and the capacity of the sludge water tank can be reduced as compared with the conventional case.
[0022]
Furthermore, since sludge water with a low cement concentration is treated in the first step compared to the conventional dehydration step where the total amount of cement is uniform, it prevents the wear of the machine in the dehydration treatment and the amount of cement in the piping. Adhesion can be reduced.
Further, since the intake port moves along the upper and lower surfaces of the water surface, the sludge water in the water surface portion with a low cement concentration is always sent to the dehydrator, so that the dehydrator can maintain the first high dewatering capacity.
[Brief description of the drawings]
FIG. 1 is a flowchart of a dehydration process according to the present invention.
FIG. 2 shows a correlation curve between the amount of dewatering per unit time of the dehydrator and the cement concentration of sludge water.
[Explanation of symbols]
1 1st process 2 2nd process

Claims (3)

Correlation curve between the amount of dewatering per unit time of the dehydrator and the cement concentration of the sludge water in the sludge water treatment method in which the sludge water containing cement discharged from ready-mixed concrete mixing equipment is dehydrated by the dehydrator The deflection point on the correlation curve where the dewatering amount of the dehydrator begins to increase sharply as the cement concentration of sludge water decreases is detected, and sludge water below the cement concentration of the deflection point is dewatered. A method for treating sludge water of ready-mixed concrete, comprising: a first step of performing a dehydration process by stirring sludge water having a cement concentration at the deflection point or higher in a sludge water tank. The method for treating sludge water of ready-mixed concrete according to claim 1, wherein the cement concentration of sludge water at the deflection point is 3 to 6%. The intake port for sending sludge water from the sludge water tank to the dehydrator is provided in the water surface portion in the first step, and the intake port moves along the top and bottom of the water surface. Of raw concrete sludge water treatment.

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