JP6519778B2 - PH reduction device for fresh concrete car washing water and pH lowering method for fresh concrete car washing water - Google Patents

Description

  The present invention relates to a technology for lowering the pH of cleaning water (hereinafter, referred to as "clean vehicle wash water") produced when cleaning a ready-mixed concrete vehicle (hereinafter, "clean vehicle"), and more specifically In particular, the present invention relates to an apparatus and method for reducing the pH of fresh water wash water using exhaust gas discharged from a fresh water vehicle.

  Concrete is a major construction material as well as steel materials, and is used in various structures including civil engineering structures such as dams, tunnels and bridges, and building structures such as apartment buildings and office buildings. Concrete is generally manufactured at a factory or an on-site plant, transported to the vicinity of a target form, and cast. Thus, concrete has a state before and after hardening, and before hardening, that is, concrete in which cement, water, aggregate and the like are mixed is referred to as fresh concrete or fresh concrete. Here, for convenience, the unhardened concrete is referred to as "green concrete". In addition, a dedicated car for transporting ready-mixed concrete is also referred to as an agitator car or a truck mixer, but here, it is referred to as a ready-mixed car.

  The fresh concrete car is provided with a drum for containing the fresh concrete at the time of transportation, and even after the completion of the placement, some of the fresh concrete remains, so that the inside of the drum is cleaned after the work. Washing is mainly carried out using water, but the fresh water wash water discharged by washing naturally contains fresh water, and since the pH of fresh water is 12 to 13, the fresh water wash water is also strongly alkaline. Indicates

  Strong alkali clean vehicle washing water is released after being neutralized. FIG. 6 is an explanatory view showing a conventional technique for neutralizing fresh cleaning car wash water. As shown in this figure, conventionally, fresh concrete car washing water is temporarily 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 the large carbon dioxide gas is sent under high pressure. The car wash water is neutralized. In other words, in order to neutralize the fresh cleaning car wash water, a large amount of carbon dioxide gas is required, and further, a power unit for feeding carbon dioxide gas at high pressure is required, which causes considerable cost.

  Then, in patent document 1, in order to effectively utilize the fresh concrete sludge (one part contained in a fresh concrete car washing water) which costed and was neutralized, the technique recycled as a backfill material is proposed.

JP, 2014-087723, A

  By using the technique proposed in Patent Document 1, it is possible to reuse the raw concrete sludge as a backfill material by neutralization. However, the technique of Patent Document 1 requires the preparation of ferrous sulfate, a polymer coagulant, and an inorganic powder, and also requires a stirring and mixing apparatus, resulting in a problem of considerable cost.

In addition, the prior art shown in FIG. 6 also has a problem that it also costs a considerable cost as described above. In addition, the car engine is operated to rotate the drum when washing the fresh concrete car, but as a result, the exhaust gas (CO ₂ ) of the fresh concrete car, that is, the greenhouse gas is discharged during the washing I also had.

The object of the present invention is to solve the problems of the prior art, that is, to reduce the pH of fresh cleaning car wash water while suppressing the exhaust gas (CO ₂ ) of fresh control car during cleaning, and to reduce the amount of carbonated water. The pH reduction device for fresh water wash water and the pH of fresh water wash water that do not require gas or special materials, and do not require any special power to send exhaust gas from fresh concrete vehicles into fresh water wash water. It is to provide a method of decline.

  The present invention was made focusing on the point of lowering the pH of the fresh cleaning vehicle wash water by utilizing the exhaust gas discharged from the fresh storage vehicle during cleaning, and is carried out based on an unprecedented idea. It is

The apparatus for lowering pH of fresh car wash water according to the present invention includes a water injection port for injecting wash water, a storage chamber for storing wash water, and an air supply unit for feeding exhaust gas discharged from the fresh car into the storage room. It is The exhaust gas is fed into the storage chamber by the exhaust pressure of the fresh concrete car, and the exhaust gas passes through the cleaning water of the storage chamber, thereby causing the acid component (CO ₂ ) of the exhaust gas and the alkaline component of the cleaning water React and the pH of the wash water drops.

  The apparatus for lowering pH of fresh car wash water according to the present invention may be provided with a partition plate. The partition plate is formed in a wave shape or a concavo-convex shape so as to be a barrier to the passage of exhaust gas, and the exhaust gas blocked in passage by this shape stirs the cleaning water in the storage chamber, As a result, the neutralization reaction is promoted. Therefore, the partition plate is installed in the storage chamber above the exhaust gas passing therethrough.

  The method for lowering the pH of the ready-mixed vehicle washing water according to the present invention is a method comprising a water storage process and an air supply process. In the water storage process, the flush water is stored in the storage chamber, and in the air supply process, the exhaust gas discharged from the fresh concrete car is fed into the storage room only by the exhaust pressure of the fresh concrete car. In addition, on the upper surface of the storage chamber, a partition plate formed in a wave or concavo-convex shape so as to be a barrier to the passage of exhaust gas is installed. When the supplied exhaust gas passes through the cleaning water of the storage chamber, the passage of the exhaust gas is impeded by the shape of the partition plate, whereby the cleaning water and the exhaust gas are agitated to promote the neutralization reaction. Ru.

The pH lowering device for fresh car washing water according to the present invention and the method for lowering the pH of fresh car washing water have the following effects.
(1) Since the pH of the fresh concrete vehicle washing water is significantly lowered, the amount of carbon dioxide gas to be used can be significantly reduced when it is finally neutralized in the turbid water treatment facility.
(2) It is possible to reduce the exhaust gas (CO ₂ ) emitted from the fresh concrete car during the cleaning, that is, to suppress the emission of greenhouse gas (CO ₂ ).
(3) Even if the exhaust pressure is low due to the fresh concrete car, exhaust gas can pass through the fresh water wash water of the fresh concrete car. As a result, it can be implemented at low cost without the need for a special power plant.
(4) By providing a partition plate in the pH lowering device for the clean vehicle cleaning water, the clean vehicle cleaning water and the exhaust gas are stirred, and the neutralization reaction is further promoted.

The flowchart which shows the main processes of the pH fall method of a fresh concrete car washing water. The model figure for demonstrating the pH fall method of a fresh concrete car washing water. Sectional drawing which shows the detail of the pH fall apparatus of the fresh concrete car wash water of this invention. FIG. 7 is a graph showing the pH of fresh water wash water during cleaning of the fresh food vehicle 100 and the amount of CO ₂ absorbed by the fresh water wash water. The graph showing the amount of carbon dioxide gas required in order to neutralize fresh-con car washing water (per unit water quantity). Explanatory drawing which shows the prior art which neutralizes cleaning vehicle car wash water.

  One example of an embodiment of the apparatus for lowering pH of fresh car wash water and the method for lowering pH of fresh car wash water according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a flow chart showing the main processing of the method for lowering the pH of fresh cleaning car wash water, and FIG. 2 is a model diagram for explaining the method for lowering pH of fresh cleaning car wash water.

  The ready-to-stock vehicle 100, which has completed the placement of the ready-mixed concrete delivered, moves to a predetermined washing place to perform washing (Step 10). The raw water tank 200 is installed at the washing place, and the fresh concrete car cleaning water generated by the washing of the fresh concrete car 100 is drained into the raw water tank 200 (Step 20). In addition, since cleaning of the fresh concrete car 100 is performed while rotating the drum, the engine of the fresh concrete car 100 is always operating during cleaning.

  Next, a portion (for example, the supernatant) of the ready-to-use vehicle wash water stored in the raw water tank 200 is pumped up, and the fresh solution vehicle wash water pH reduction device 300 of the present invention (hereinafter simply referred to as “pH decrease device 300”) ) Is supplied (Step 30). Therefore, the pH reduction device 300 may be disposed near the raw water tank 200.

  The pH reducing device 300 will now be described in detail with reference to FIG. FIG. 3 is a cross-sectional view showing the details of the pH reduction device 300. As shown in FIG. As shown to this figure, the pH fall apparatus 300 is equipped with the water tank 301 of the substantially rectangular parallelepiped comprised by the top plate, the baseplate, and four side plates. Then, in the water tank 301, a space (hereinafter, referred to as a "storage chamber") in which fresh cleaning car wash water can be stored is formed. In addition, an opening (hereinafter, referred to as a “water injection port”) for injecting fresh cleaning car wash water is provided in a part of the water tank 301 (for example, a top plate or a side plate).

  In addition, an opening (hereinafter referred to as "air supply port 302") for supplying exhaust gas from a fresh concrete car is provided in a part of the water tank 301 (for example, a top plate or a side plate). There is also provided a flue 303 for guiding the exhaust gas flowing in from the mouth 302. Here, for convenience, the air supply port 302 and the air supply pipe 303 are collectively referred to as an “air supply unit”.

  In the storage chamber, a partition plate 304 supported by a plurality (three in the drawing) of supports 304 is installed. As will be described later, this partition plate 305 is for obstructing the passage of exhaust gas so as to stay for a long time in fresh cleaning car wash water. Therefore, the outlet of the air supply pipe 303 is located below the partition plate 305, and the exhaust gas discharged from the passage passes below the partition plate 305. In other words, the partition plate 305 and the bottom plate of the water tank 301 form an exhaust gas passage.

  The lower surface of the partition plate 305 (that is, the surface in contact with the exhaust gas) has a wave-like or uneven shape so as to be a barrier to the passage of the exhaust gas. On the other hand, the partition plate 305 is arranged to be inclined so that the exhaust gas can pass through the lower surface of the partition plate 305 even with a low exhaust pressure. Specifically, the partition plate 305 is disposed so as to have an upward slope from the start side (left side in the drawing) to the end side (right side in the drawing) of the exhaust gas passage. That is, the venting path of the exhaust gas is such that the venting cross section gradually increases from the starting point side to the end point side.

  Exhaust gas that has passed through the lower surface of the partition plate 305 is transmitted to the outside of the pH reducing device 300 through an opening (hereinafter referred to as “exhaust port 306”) provided in a part of the water tank 301 (for example, top plate or side plate). Released. In addition, fresh vehicle car wash water whose pH has dropped sufficiently is discharged to the outside of the pH reducing device 300 by opening the drain valve 307.

  Returning to FIG. 1, the subsequent processing will be described. A part of the ready-to-use vehicle wash water is injected from the water inlet of the pH reduction device 300 (Step 30), and a predetermined amount of ready-to-use vehicle wash water is stored in the storage chamber. At this time, it is preferable to set the storage height (so to speak, the water depth) of fresh cleaning car wash water low to some extent. For example, it is within 50 cm, preferably 35 cm to 45 cm. In the present invention, the pressure for the exhaust gas to pass through the cleaning water of the fresh concrete car uses the exhaust pressure of the fresh concrete car. 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 fresh concrete cleaning water to some extent.

  When a predetermined amount of fresh concrete wash water is stored in the storage chamber, the exhaust gas discharged from the fresh storage vehicle 100 is sent to the storage chamber (Step 40). As described above, during the cleaning of the fresh concrete vehicle 100, the engine is operating and exhaust gas continues to be discharged. In the present invention, this exhaust gas is effectively used. Specifically, an exhaust pipe is connected to the exhaust port (muffler) of the fresh concrete vehicle 100, and one end of the exhaust pipe is connected to the air supply port 302 of the pH reduction 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 wash water stored in the storage chamber.

The exhaust gas discharged into the ready-to-use vehicle wash water can not pass smoothly due to the partition plate 305 becoming an obstacle, and as a result, will stay in the ready-to-use vehicle wash water for a long time. Furthermore, due to the effect of the wave-like (or uneven) shape of the partition plate 305, the exhaust gas passes while stirring the fresh cleaning car wash water. As described above, since the exhaust gas passes through the cleaning car wash water while stirring for a long time, the exhaust gas and the cleaning car wash water efficiently react, and the pH of the cleaning car wash water decreases. More specifically, due to the neutralization reaction between the acidic component (especially CO ₂ ) contained in the exhaust gas and the alkaline component (Ca (OH) ₂ ) contained in the clean vehicle wash water, the pH of the fresh product wash water decreases Go.

  After the exhaust gas is supplied (Step 40) for a predetermined time, the pH of the fresh cleaning car wash water in the storage chamber is measured (Step 50). If the measured pH does not reach (exceed) a reference pH (a threshold value, such as PH10 or PH11, for example) which is set in advance, it is judged that the pH of the car wash water is not sufficiently lowered (Step 60, No), the exhaust gas is continuously supplied (Step 40). On the other hand, when the measured pH is lower than the reference pH, it is judged that the pH of the fresh cleaning car wash water is sufficiently lowered (Step 60, Yes), and injected into the secondary neutralization device 400 (FIG. 2) and carbon dioxide 500 And neutralize (Step 70). In addition, the neutralization process here is performed using the conventional technique.

Hereinafter, the experimental result which the inventor of this application implemented to confirm the effect of this invention is demonstrated. FIG. 4 is a graph showing the pH of fresh concrete wash water during washing of the fresh stock car 100 and the amount of CO ₂ absorbed by the fresh control car wash water. During cleaning, the drum of the stock truck 100 is rotating at low speed and high speed repeatedly.

As can be seen from FIG. 4, while cleaning the stock vehicle 100, the pH of the stock vehicle wash water (0.4 m ³ ) drops from 12.09 to 10.55 in six minutes.

Next, it will be described how much reduction in the pH of the ready-to-use vehicle wash water can reduce the amount of carbon dioxide gas required for final neutralization. If 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 known to hold.
[H ⁺ ] [OH ⁻ ] = 10 ⁻¹⁴ (at 25 ° C.)
That is, assuming that the pH of the ready-to-use vehicle wash water is n, [H ⁺ ] = 10− ⁿ , the ^hydroxide ion concentration in the ready-to-use vehicle wash water can be expressed as follows.
^{[OH -] = 10 -14 /} 10 -n (mol / L)
Therefore, in order to neutralize fresh vehicle wash water, an amount of [H ⁺ ] corresponding to the gram equivalent of [OH ⁻ ] = 10 ^{− (14-n)} in fresh vehicle wash water is required, and carbon dioxide gas In the case of neutralization with, the required amount of carbon dioxide gas to be used 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 substantial amount is usually calculated by multiplying the safety factor (for example, 3).
X = Q x 10- ^(14-n) x M
FIG. 5 is a graph of the above equation, and is a graph showing the amount of carbon dioxide gas required to neutralize fresh clean vehicle wash water (per unit water amount).

For example, the amount of carbon dioxide gas (theoretical value) required for 1 m ³ of fresh car wash water at pH 12 and 1 m ³ of fresh water wash wash at pH 11 will be determined.
[In the case of pH 12]
X1 = 1 x 10- ^(14-12) x 44 = 0.44 (kg)
[In the case of pH 11]
X2 = 1 x 10- ^(14-11) x 44 = 0.044 (kg)
Thus, it can be seen that the amount of carbon dioxide gas used can be significantly reduced simply by lowering the pH 12 to the pH 11. As shown in FIG. 4, according to the present invention, it is possible to lower the pH of the fresh concrete washing water, that is, to significantly reduce the amount of carbon dioxide gas used in the neutralization process (Step 70) which is the final step. . In particular, as can be seen from FIG. 5, the effect exhibited by the present invention is greater as the pH of the fresh cleaning car wash water is higher (for example, about 12).

  The apparatus for lowering pH of fresh car wash water and the method for lowering pH of fresh car wash water according to the present invention can be suitably used in various concrete construction sites including tunnels, fresh concrete manufacturing plants and the like. If the present invention provides a cleaning method for fresh concrete vehicles in consideration of the global environment, it can be said that the invention can be expected not only to be industrially usable but also to be expected to contribute significantly to society.

100 Fresh-con vehicle 200 Raw water tank 300 pH lowering device (pH-lowering device) of fresh-con vehicle washing water of the present invention
301 Water tank 302 (pH reduction device) Air supply port 303 (pH reduction device) Air tube 304 (pH reduction device) Support body 305 (pH reduction device) Partition plate 306 (pH reduction device) 306 (pH reduction device) ) Exhaust port 307 (of pH lowering device) drain valve 400 secondary neutralization device 500 carbon dioxide gas

Claims (2)

In an apparatus for lowering the pH of the washing water discharged from a ready-mixed concrete vehicle,
A water inlet for injecting the washing water;
A storage chamber for storing the wash water injected from the injection port;
And an air supply unit for supplying the exhaust gas discharged from the ready-made concrete vehicle into the storage chamber,
The exhaust gas is supplied into the storage chamber by the exhaust pressure of the fresh concrete vehicle,
A partition plate is installed in the storage chamber above the exhaust gas passing therethrough,
The partition plate is formed in a wave or uneven shape so as to be a barrier to the passage of the exhaust gas.
The exhaust gas supplied into the storage chamber passes through the cleaning water stored in the storage chamber, and the exhaust gas whose passage is blocked due to the shape of the partition plate is the one in the storage chamber. The pH of the wash water is lowered by stirring the wash water, and the apparatus for lowering pH of fresh concrete car wash water. In the method of lowering the pH of the washing water discharged from a fresh concrete car,
A water storage step of storing the wash water in a storage chamber;
And an air supplying step of supplying the exhaust gas discharged from the ready-made concrete vehicle to the storage chamber by the exhaust pressure of the ready-made concrete vehicle.
The partition plate formed in a wave or concavo-convex shape is installed on the upper surface of the storage chamber so as to be a barrier to the passage of the exhaust gas,
The exhaust gas supplied into the storage chamber passes through the cleaning water stored in the storage chamber, and the exhaust gas whose passage is blocked by the shape of the partition plate is in the storage chamber The pH of the wash water is lowered by stirring the wash water of step 2.

Images