JP2016165694A - Raw concrete car washing water pH lowering device and fresh concrete car washing water pH lowering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pH lowering device and method of ready-mixed concrete vehicle washing water, for solving problems that a conventional technique holds, i.e., lowering the pH of ready-mixed concrete vehicle washing water while suppressing exhaust gas of a ready-mixed concrete vehicle during washing, free from the need of a large amount of carbon dioxide and a specific material, and free from the need of special power force for sending exhaust gas of a ready-mixed concrete vehicle into ready-mixed concrete vehicle washing water.SOLUTION: A pH lowering device of ready-mixed concrete vehicle washing water includes; a water pouring port for pouring washing water; a storage chamber for storing washing water; and an air sending part for sending exhaust gas discharged from a ready-mixed concrete vehicle into the storage chamber. The pH of washing water is lowered by sending exhaust gas into the storage chamber by exhaust pressure of the ready-mixed concrete vehicle, and passing exhaust gas through washing water in the storage chamber so as to make oxidation elements of exhaust gas and alkaline elements of washing water react.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for lowering the pH of washing water (hereinafter referred to as “raw concrete vehicle washing water”) generated when washing a concrete concrete car (hereinafter referred to as “raw concrete car”), and more specifically. Specifically, the present invention relates to an apparatus and a method for lowering the pH of raw concrete car washing water using exhaust gas discharged from the raw concrete car.

  Concrete is a major construction material together with steel, and is used in various structures including civil engineering structures such as dams, tunnels, and bridges, and architectural structures such as housing complexes and office buildings. In general, concrete is manufactured in a factory or an on-site plant, transported to the vicinity of the target mold, and placed. Thus, concrete has a state before hardening and after hardening, and concrete which is before hardening, that is, a state in which cement, water, aggregate, and the like are mixed is called ready-mixed concrete or fresh concrete. Here, for the sake of convenience, the uncured concrete is referred to as “green concrete”. A dedicated vehicle that transports ready-mixed concrete is also called an agitator car or a truck mixer truck.

  The ready-mix car has a drum for storing the ready-mixed container during transportation, and a part of the ready-mixed container remains even after the placement is completed. Cleaning is mainly performed using water, but the raw concrete car washing water discharged by washing naturally contains raw concrete, and since the pH of the raw concrete is 12 to 13, this raw concrete car washing water is also strongly alkaline. Indicates.

  Strong alkaline raw car washing water is neutralized and released. FIG. 6 is an explanatory diagram showing a conventional technique for neutralizing raw concrete car washing water. Conventionally, as shown in this figure, raw car cleaning water is once stored in the raw water tank, then the supernatant of the raw water tank is pumped up and transferred to the neutralization treatment layer, and a large amount of carbon dioxide gas is sent at high pressure to send the raw Car wash water is neutralized. In other words, a large amount of carbon dioxide gas is required to neutralize the ready-mixed vehicle washing water, and a power device for sending carbon dioxide gas at a high pressure is required.

  Therefore, Patent Document 1 proposes a technique of reusing as a backfill material in order to effectively utilize raw consludge neutralized at a cost (a part contained in raw concrete car washing water).

JP 2014-087723 A

  If the technique proposed in Patent Document 1 is used, the raw consludge can be reused as a backfill material by neutralization. However, the technique of Patent Document 1 has a problem in that it requires a ferrous sulfate, a polymer flocculant, and an inorganic powder, and also requires a stirring and mixing device, which requires considerable cost.

Further, the conventional technique shown in FIG. 6 also has a problem that a considerable cost is required as described above. In addition, when cleaning the ready-mix car, the car engine is operated to rotate the drum. As a result, exhaust gas (CO ₂ ), that is, greenhouse gas, is discharged during cleaning. Also had.

The object of the present invention is to solve the problems of the prior art, that is, to reduce the pH of raw concrete car washing water while suppressing the exhaust gas (CO ₂ ) of the raw concrete car during washing, and a large amount of carbonic acid. No pH or special material is required, and no special power is required to send the exhaust gas from the ready-mixed vehicle to the ready-mixed vehicle washing water. To provide a lowering method.

  The present invention has been made in view of the fact that the pH of raw car cleaning water is lowered by utilizing exhaust gas discharged from the raw control car during cleaning, and is based on an unprecedented idea. It is a thing.

The raw-con car washing water pH lowering device of the present invention includes a water injection port for injecting cleaning water, a storage chamber for storing the cleaning water, and an air supply unit for supplying exhaust gas discharged from the raw-con vehicle into the storage chamber. It is a thing. The exhaust gas is fed into the storage chamber by the exhaust pressure of the raw concrete vehicle, and further, the exhaust gas passes through the cleaning water of the storage chamber, so that the acidic component (CO ₂ ) of the exhaust gas and the alkaline component of the cleaning water Reacts and the pH of the wash water decreases.

  The device for lowering the pH of the ready-mixed vehicle washing water according to the present invention may be provided with a partition plate. The partition plate is formed in a wave shape or an uneven shape so as to be a barrier against the passage of the exhaust gas, and the exhaust gas obstructed by this shape stirs the washing water in the storage chamber, As a result, the neutralization reaction is promoted. Therefore, this partition plate is installed in the storage chamber and above the exhaust gas.

  The method for lowering the pH of raw concrete car washing water according to the present invention is a method comprising a water storage process and an air supply process. In the water storage step, the wash water is stored in the storage chamber, and in the air supply step, the exhaust gas discharged from the raw control vehicle is supplied into the storage chamber only by the exhaust pressure of the raw control vehicle. A partition plate formed in a wave shape or an uneven shape is installed on the upper surface of the storage chamber so as to be a barrier against the passage of exhaust gas. When the exhaust gas sent through the cleaning water in the storage chamber is blocked by the shape of the partition plate, the cleaning water and the exhaust gas are agitated, and the neutralization reaction is promoted. The

The raw-con car washing water pH lowering device and the raw-con car washing water pH lowering method of the present invention have the following effects.
(1) Since the pH of raw concrete vehicle washing water is remarkably lowered, the amount of carbon dioxide used can be greatly reduced when finally neutralizing with muddy water treatment equipment.
(2) The exhaust gas (CO ₂ ) discharged from the ready-mixed vehicle during cleaning can be reduced, that is, the amount of greenhouse gas (CO ₂ ) emitted can be suppressed.
(3) Even if the exhaust pressure is low due to the raw concrete car, the exhaust gas can pass through the raw concrete car washing water. As a result, a special power unit is not required and can be implemented at a low cost.
(4) By providing the partition plate in the pH reducing device for the raw concrete car washing water, the raw concrete car washing water and the exhaust gas are agitated, and the neutralization reaction is further promoted.

The flowchart which shows the main processes of the pH reduction method of raw concrete car washing water. The model figure for demonstrating the pH fall method of raw concrete car washing water. Sectional drawing which shows the detail of the pH reduction apparatus of the raw concrete car washing water of this invention. And pH of fresh concrete car wash water in the washing of the fresh concrete vehicle 100, a graph showing the amount of CO ₂ mixed concrete vehicles wash water absorbed. The graph showing the amount of carbon dioxide gas required in order to neutralize raw concrete car washing water (per unit water quantity). Explanatory drawing which shows the prior art which neutralizes raw concrete car washing water.

  An example of an embodiment of the pH reducing apparatus for raw concrete car washing water and the method for lowering the pH of raw concrete car washing water according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a flowchart showing main processes of a method for lowering the pH of raw-con car washing water, and FIG. 2 is a model diagram for explaining a method for lowering the pH of raw-con car washing water.

  The ready-mixed vehicle 100 in which the transported live-con is placed is moved to a predetermined cleaning place and cleaned (Step 10). The raw water tank 200 is installed at the washing place, and the raw concrete car washing water generated by washing the raw concrete car 100 is drained into the raw water tank 200 (Step 20). In addition, since cleaning of the ready-mixed vehicle 100 is performed while rotating the drum, the engine of the ready-mixed vehicle 100 is always operating during cleaning.

  Next, a part of the raw concrete car washing water (for example, the supernatant) stored in the raw water tank 200 is pumped up to reduce the pH of the raw concrete car washing water according to the present invention 300 (hereinafter simply referred to as “pH lowering apparatus 300”). (Step 30). Therefore, the pH lowering device 300 may be disposed near the raw water tank 200.

  Here, the pH lowering apparatus 300 will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view showing details of the pH lowering device 300. As shown in this figure, the pH lowering device 300 includes a substantially rectangular parallelepiped water tank 301 including a top plate, a bottom plate, and four side plates. And in this water tank 301, the space (henceforth a "storage chamber") which can store raw concrete car washing water is formed. In addition, a part of the water tank 301 (for example, a top plate or a side plate) is provided with an opening (hereinafter, referred to as a “water injection port”) for pouring the water-con-vehicle washing water.

  Also, a part of the water tank 301 (for example, a top plate or a side plate) is provided with an opening (hereinafter referred to as “air supply port 302”) for supplying exhaust gas from the raw concrete vehicle. An air supply pipe 303 for guiding the exhaust gas flowing in from the port 302 is also provided. Here, for convenience, the air supply port 302 and the air supply tube 303 are collectively referred to as an “air supply unit”.

  In the storage chamber, partition plates 304 supported by a plurality (three in the figure) of support bodies 304 are installed. As will be described later, the partition plate 305 is used to block the passage of exhaust gas so that it stays in the raw concrete car washing water for a long time. Therefore, the outlet of the air supply pipe 303 is located below the partition plate 305, and the exhaust gas discharged from here passes below the partition plate 305. In other words, an exhaust gas ventilation path is formed by the partition plate 305 and the bottom plate of the water tank 301.

  The lower surface of the partition plate 305 (that is, the surface in contact with the exhaust gas) has a wavy or uneven shape so as to be a barrier against the passage of the exhaust gas. On the other hand, the partition plate 305 is inclined and arranged so that the exhaust gas can pass through the lower surface of the partition plate 305 even at a low exhaust pressure. Specifically, the partition plate 305 is arranged so as to have an upward slope from the start side (left side in the figure) to the end point side (right side in the figure) of the exhaust gas ventilation path. In other words, the ventilation path of the exhaust gas gradually increases in size from the starting point side to the ending point side.

  Exhaust gas that has passed through the lower surface of the partition plate 305 passes from an opening (hereinafter referred to as “exhaust port 306”) provided in a part of the water tank 301 (for example, a top plate or a side plate) to the outside of the pH reducing device 300. Released. Moreover, the ready-mixed vehicle washing water whose pH has been sufficiently lowered is discharged to the outside of the pH lowering device 300 by opening the drain valve 307.

  Returning to FIG. 1, the subsequent processing will be described. A part of the raw concrete car washing water is poured from the water inlet of the pH lowering device 300 (Step 30), and a predetermined amount of raw concrete car washing water is stored in the storage chamber. At this time, the storage height (in other words, the water depth) of the ready-mixed vehicle washing water may be set to be low to some extent. For example, it is within 50 cm, desirably 35 cm to 45 cm. In the present invention, as the pressure for the exhaust gas to pass through the raw concrete car washing water, the exhaust pressure provided in the raw concrete car is used. That is, it is necessary to push the exhaust gas at a relatively low pressure. Therefore, it is better to reduce the water pressure acting on the exhaust gas, that is, to reduce the storage height of the raw concrete car washing water to some extent.

  When a predetermined amount of raw concrete vehicle washing water is stored in the storage chamber, exhaust gas discharged from the raw concrete vehicle 100 is supplied to the storage chamber (Step 40). As described above, during the cleaning of the ready-mixed vehicle 100, the engine is operating and exhaust gas continues to be discharged. In the present invention, this exhaust gas is effectively utilized. Specifically, an exhaust pipe is connected to the exhaust port (muffler) of the ready-mixed vehicle 100, and one end of the exhaust pipe is connected to the air supply port 302 of the pH lowering device 300. As a result, the exhaust gas discharged from the ready-mixed vehicle 100 is discharged from the muffler through the exhaust pipe, the air supply port 302, and the air supply tube 303 into the ready-mixed vehicle washing water stored in the storage chamber.

The exhaust gas discharged into the ready-mix vehicle washing water cannot smoothly pass due to the partition plate 305 becoming an obstacle, and as a result, stays in the ready-mixed vehicle washing water for a long time. Further, due to the effect of the wavy (or uneven) shape of the partition plate 305, the exhaust gas passes through the raw concrete car washing water while stirring. Thus, since the exhaust gas passes through the raw concrete car washing water while stirring for a long time, the exhaust gas and the raw concrete car washing water react efficiently, and the pH of the raw concrete car washing water decreases. More specifically, the pH of the raw concrete car washing water is lowered by the neutralization reaction between the acidic component (particularly CO ₂ ) contained in the exhaust gas and the alkaline component (Ca (OH) ₂ ) contained in the raw concrete car washing water. Go.

  When the exhaust gas is supplied for a predetermined time (Step 40), the pH of the raw concrete car washing water in the storage chamber is measured (Step 50). If the measured pH has not reached (exceeded) a preset reference pH (for example, PH10, PH11, etc.), it is determined that the pH of the ready-mixed vehicle washing water has not sufficiently decreased (Step 60, No), the exhaust gas is continuously supplied (Step 40). On the other hand, if the measured pH is lower than the reference pH, it is determined that the pH of the raw concrete car washing water has sufficiently decreased (Step 60, Yes), and is charged into the secondary neutralization device 400 (FIG. 2) and carbon dioxide 500 Neutralize with (Step 70). The neutralization treatment here is performed using conventional techniques.

Hereinafter, experimental results conducted by the inventors of the present application in order to confirm the effects of the present invention will be described. FIG. 4 is a graph showing the pH of raw concrete car washing water during washing of the raw concrete car 100 and the amount of CO ₂ absorbed by the raw concrete car washing water. During cleaning, the drum of the ready-mixed vehicle 100 repeats low-speed rotation and high-speed rotation.

As can be seen from FIG. 4, during the cleaning of the ready-mixed vehicle 100, the pH of the ready-mixed vehicle washing water (0.4 m ³ ) decreased from 12.09 to 10.55 in 6 minutes.

Next, how much the reduction of the pH of the ready-mixed vehicle washing water can reduce the amount of carbon dioxide necessary for the final neutralization will be described. It is known that when the temperature is constant, the product of the hydrogen ion concentration [H ⁺ ] and the hydroxide ion concentration [OH ⁻ ] in the aqueous solution is constant, and the following equation is established.
[H ⁺ ] [OH ⁻ ] = 10 ⁻¹⁴ (at 25 ° C.)
That is, if the pH of raw concrete car washing water is n, [H ⁺ ] = 10 ⁻ⁿ , the ^hydroxide ion concentration in the raw concrete car washing water can be expressed as follows.
[OH ⁻ ] = 10 ⁻¹⁴ / 10 ⁻ⁿ (mol / L)
Therefore, in order to neutralize the raw concrete car washing water, an amount of [H ⁺ ] corresponding to the gram equivalent of [OH ⁻ ] = 10 ^{− (14−n) in} the raw concrete car washing water is necessary, and carbon dioxide gas When neutralizing with, the required amount of carbon dioxide is expressed by the following equation. In the formula, X is the amount of carbon dioxide (kg), Q is the amount of water (m ³ ), and M is the molecular weight of carbon dioxide (44 g / mol). However, the amount obtained by the following equation is a theoretical value, and the actual amount is usually calculated by multiplying by a safety factor (for example, 3).
X = Q × 10 ^{− (14−n)} × M
FIG. 5 is a graph showing the above equation, and is a graph showing the amount of carbon dioxide gas required to neutralize raw car cleaning water (per unit water amount).

For example, a ready-mixed concrete vehicles cleaning water 1 m ³ of pH 12, for ready-mixed concrete vehicles cleaning water 1 m ³ of pH 11, try each amount of carbon dioxide required (theoretical value) determined.
[In the case of pH 12]
X1 = 1 × 10 ^{− (14−12)} × 44 = 0.44 (kg)
[In the case of pH 11]
X2 = 1 × 10− ^(14-11) × 44 = 0.044 (kg)
Thus, it can be seen that the amount of carbon dioxide used can be significantly reduced simply by lowering the pH from pH 12 to pH 11. As shown in FIG. 4, according to the present invention, the pH of the ready-mixed vehicle washing water can be lowered, that is, the amount of carbon dioxide used in the neutralization treatment (Step 70) as the final step can be greatly reduced. . In particular, as can be seen from FIG. 5, the effect of the present invention is greater as the pH of the ready-mixed vehicle washing water is higher (for example, about 12).

  The apparatus for reducing the pH of raw concrete car washing water and the method for lowering the pH of raw concrete car washing water according to the present invention can be suitably used in various concrete construction sites including tunnels, raw concrete manufacturing factories, and the like. Considering that the present invention provides a cleaning method for a ready-mixed vehicle in consideration of the global environment, it can be said that the invention can be used not only industrially but also can make a great social contribution.

100 raw concrete car 200 raw water tank 300 pH reducing device for raw concrete car washing water of the present invention (pH lowering device)
301 Water tank (for pH lowering device) 302 Air feeding port (for pH lowering device) 303 Air feeding tube (for pH lowering device) 304 Support body (for pH lowering device) 305 Partition plate (for pH lowering device) 306 (pH lowering device) )) Exhaust port 307 Drain valve (for pH lowering device) 400 Secondary neutralizer 500 Carbon dioxide

Claims (3)

In the device that lowers the pH of the wash water discharged from the ready-mixed concrete car,
A water inlet for pouring the washing water;
A storage chamber for storing the wash water injected from the water injection port;
An air supply unit for supplying exhaust gas discharged from the ready-mixed concrete vehicle into the storage chamber;
The exhaust gas is fed into the storage chamber by the exhaust pressure of the ready-mixed concrete vehicle,
Ready-mixed concrete car cleaning, wherein the pH of the cleaning water is lowered by passing the exhaust gas supplied into the storage chamber through the cleaning water stored in the storage chamber Water pH lowering device. In the storage chamber, a partition plate is installed above the exhaust gas,
The partition plate is formed in a wave shape or an uneven shape so as to be a barrier against the passage of the exhaust gas,
2. The pH reduction apparatus for fresh concrete car washing water according to claim 1, wherein the exhaust gas obstructed by the shape of the partition plate agitates the washing water in the storage chamber. In the method of lowering the pH of the washing water discharged from the ready-mixed concrete vehicle,
A water storage step of storing the wash water in a storage chamber;
An air supply step of supplying exhaust gas discharged from the ready-mixed concrete vehicle into the storage chamber by exhaust pressure of the ready-mixed concrete vehicle,
On the upper surface of the storage chamber, the partition plate formed in a wave shape or an uneven shape is installed so as to be a barrier against the passage of the exhaust gas,
The exhaust gas fed into the storage chamber passes through the wash water stored in the storage chamber, and the exhaust gas blocked by the shape of the partition plate passes through the storage chamber. The method for lowering the pH of washing water for ready-mixed concrete vehicles, wherein the pH of the washing water is lowered by stirring the washing water.

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