JP2570528B2 - Large-diameter pipe without dead water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-diameter pipeline which is used as a water supply underground at a large depth and does not generate dead water.

[0002]

2. Description of the Related Art A large-diameter pipeline for water supply pipes for supplying water is installed underground at shallow and medium depths, and has conventionally been used as existing equipment. Although there is no particular rule regarding the size of the large-diameter pipeline, the diameter that a person can enter and work on is 800 mm or more in diameter. It is intended to refer to a pipeline having the above diameter. Large-diameter pipelines installed underground at shallow and medium depths have, in principle, a pipe diameter that matches the planned water transmission and distribution volume.
Basically, the water storage function is not considered. For this reason, water does not accumulate in large-diameter pipelines installed underground at shallow and medium depths.

On the other hand, a concept of supplying drinking water and other drinking water using a large-diameter pipeline installed underground at a large depth has recently been announced by the Ministry of Health and Welfare and the Water Pipe Technology Center. ing. Under these plans, large-diameter pipelines installed underground at a large depth are expected to contribute to the block piping network of water distribution pipes, and need to have a water storage function (stock function). Have been.

[0004] Such a large-diameter pipeline installed underground at a large depth is required to have a storage function as described above, and is therefore used as a normal water supply pipe and a water distribution pipe. In comparison with large-diameter pipelines installed underground at shallow and medium depths, it is predicted that the ratio of water usage to storage capacity will be smaller, and the water retention time in pipelines will be relatively longer. Therefore, it is considered that there is a high possibility that the residual chlorine concentration in the tap water decreases. as a result,
There is a danger of dead water coming out of water taps (such as faucets in each household).

[0005] The Water Supply Law enforcement regulations stipulate that the water in the hydrant should be disinfected with chlorinated water so as to maintain the free residual chlorine at 0.1 ppm or more. Water is called "dead water".

[0006]

SUMMARY OF THE INVENTION
For large-diameter pipelines installed underground at deep depths, measures to prevent dead water, that is, the water at the hydrant must meet the above rules (free residual chlorine should be 0.1 ppm or more) It is. As a countermeasure, it is conceivable to inject a chemical for chlorine disinfection (hereinafter referred to as "chlorine agent") into tap water and disinfect it in the middle of a large-diameter pipeline installed underground at a large depth. . However, in the usual injection method, since the residual chlorine concentration is supplied while being non-uniform, there is a problem that the residual chlorine concentration is insufficient or an odor is generated due to an excessive amount. In addition, there is a problem that the amount of the chlorine agent used is generally large.

As described above, disinfection using a chlorine agent is performed by providing a disinfection facility in the middle of a large-diameter pipeline water distribution pipe and additionally injecting a chlorine agent. By the way, various techniques have been conventionally used for disinfecting and disinfecting equipment by injecting a chlorine agent, mixing and stirring of chlorine.
Hereinafter, these will be described. First, disinfection and disinfection equipment will be described. (1) Purpose of disinfection: Pathogens in raw water are usually largely removed by sedimentation and filtration at water treatment plants, but a small number may remain, so disinfection is performed to kill them. .

(2) Disinfection method: Disinfection of water is supposed to use chlorine (Ministry of Health and Welfare notification). Therefore, use other than chlorine is not allowed.

(3) There are the following three disinfection methods using chlorine. Use liquefied chlorine: Liquefied chlorine is liquefied chlorine gas at low temperature and high pressure. Use sodium hypochlorite: sodium hypochlorite is obtained by brine (fresh water) electrolysis. Use calcium hypochlorite (bleach). Among the above three methods, liquefied chlorine is overwhelmingly used. However, the method using sodium hypochlorite is increasing from the viewpoint of handling safety.

(4) The principle of chlorination. The method of chlorination in a water treatment plant is performed by a discontinuous point chlorination method. Hereinafter, the discontinuous point chlorination will be described. When a chlorinating agent is introduced into water containing ammonia and organic nitrogen compounds, the chlorine first reacts with the contents thereof to form combined residual chlorine. The combined residual chlorine increases as the chlorine injection rate increases, but when the chlorine injection rate reaches a certain amount, chloramine is oxidized to nitrogen gas and the residual chlorine concentration decreases. However, if the chlorine injection rate is further increased beyond that, the free residual chlorine concentration increases proportionately. This series of changes is shown in FIG.
FIG. 3 is a graph showing the relationship between the chlorine injection rate and the residual chlorine concentration. The minimum point of the residual chlorine concentration that occurs during this series of changes is called a discontinuous point (BREAK POINT). The method of injecting chlorine beyond this point to generate free residual chlorine and treat it is called the discontinuous point chlorine. Processing. Discontinuous point chlorination provides a sufficient disinfecting effect and is also effective as a method for removing iron and manganese.

(5) Chlorine disinfection equipment. Storage equipment. Since disinfection is indispensable for water purification treatment, it is necessary to provide sufficient room for the storage of disinfectants such as chlorine, and to always secure more than 10 days of usage. Liquefied chlorine containers include portable 50Kg or 1-ton iron containers and storage tanks installed at water treatment plants. In each case, prevent chlorine gas from leaking, prevent direct sunlight, and prevent moisture. Must be stored with great care. Since sodium hypochlorite is highly alkaline and corrosive, a corrosion-resistant material must be used for the storage tank. In addition, in order to prevent the available chlorine content from decreasing, it is necessary to store it while avoiding solar radiation and temperature rise, and to periodically measure the available chlorine content. Injection equipment. The chlorinator includes a dry type and a wet type. Commonly used is a wet injector. Wet injectors include pressure injectors and vacuum injectors. A pressure-type injector is a type in which chlorine gas is dissolved from the surface of water in a mixing bottle to produce chlorine water.A vacuum-type injector uses a vacuum force generated in an injector by pressurized water to generate chlorine gas. Is dissolved in pressurized water while sucking water to produce chlorine water. Piping for chlorine injection must be subjected to a pressure test and a leak test to prevent chlorine gas from leaking. Excluded equipment. Regarding chlorine gas, the Labor Standards Act stipulates a maximum allowable limit of 1 ppm during work. For liquefied chlorine, exclusion facilities such as a leak detector and a neutralizer during storage are to be provided according to general high-pressure gas safety regulations.

(6) Control of chlorine injection. The chlorine injection control includes constant value control, flow rate proportional control, and residual chlorine control. Hereinafter, the three injection controls will be described. Constant value control. It is used when the amount of treated water and the required amount of chlorine are small and a predetermined amount of chlorine can be maintained by injecting a substantially constant amount of chlorine. Flow proportional control. The amount of treated water is controlled. However, when the change in water quality is small and the required amount of chlorine is almost constant, it is used when a predetermined amount of residual chlorine can be retained by injecting a chlorine amount according to the change in the treated water amount. Residual chlorine control. A method of controlling residual chlorine as a target value when the amount of treated water changes and the required amount of chlorine changes.

Next, the mixing and stirring equipment will be described. As a mixing and stirring equipment for chlorination, there is a chlorine mixing well "Seki". As another mixing and stirring equipment, there is a mixing chamber system used for an emergency drinking water storage tank.

As a technique of the mixing chamber system, Japanese Utility Model Publication No. Sho 62-29431
In the official gazette, an emergency drinking water storage tank is disclosed (hereinafter, referred to as “
"Prior art 1"). FIG. 4 is a sectional view of a water storage tank showing the prior art 1. The mixing chamber system according to the prior art 1 is fixed by a diametrically extending support shaft that substantially engages with a circumferential cross-sectional position inside the main body of the water storage tank 7, and the longitudinal direction of the water storage tank 7. And a plurality of partition plates 10 (partition walls) each formed of, for example, a square plate, are arranged at a predetermined interval from each other, and a plurality of mixing chambers 9 are formed by the partition plates 10. The water flowing into the water storage tank 7 is
While repeating the mixing via, the process proceeds to the next mixing chamber 9 sequentially, whereby the water is replaced. This prior art 1 has the following features. Water circulation characteristics in the water tank vary depending on the number of mixing chambers. As shown in FIG. 5, the number of mixing chambers and the replacement time of fresh water have a relationship in which the replacement time becomes shorter as the number of mixing chambers increases, but the effect does not increase when the number of mixing chambers is a certain number or more. Note that the replacement time is represented by elapsed time (flow rate / water tank capacity = how many times the water tank capacity allows the water to be completely replaced). Aspect ratio of one mixing chamber (width / length) even for long pipes
When it is set to about 1.6, good mixing characteristics are exhibited. More importantly, the average flow velocity in the tank. It should exhibit good mixing properties even at low flow rates of 1.5 to 5.9 mm / sec.

[0015] In addition, good control is easy due to the additional injection of chlorine in the distribution reservoir, and it is difficult to control the post-chlorination treatment in the water treatment plant, and the additional injection of chlorine is necessary. , Already known.

An object of the present invention is to provide a disinfection facility in the middle of a large-diameter pipe installed underground at a large depth where the water storage time is long due to the storage function, based on the above-mentioned conventional technology. An object of the present invention is to provide a large-diameter pipeline in which dead water does not occur by performing additional injection of an agent.

[0017]

As described above, we have developed a technology for preventing dead water from occurring in a large-diameter pipeline installed underground at a large depth where the water storage time is long due to the storage function. I did my research. As a result, it has been found that a large-diameter pipeline free of dead water can be obtained by providing a disinfecting facility using a combination of the above-described conventional techniques and additionally injecting a chlorine agent in the middle of the large-diameter pipeline.

The present invention has been made based on the above-mentioned findings, and has a large-diameter pipe having a circular cross-section, which is provided underground at a large depth and through which water flows, and the large-diameter pipe. Between the inner peripheral surface of the large-diameter pipeline, which is fixed in the pipe-axis orthogonal direction of the large-diameter pipeline inside, and is provided at a predetermined interval in the pipe-axis direction of the large-diameter pipeline. A plurality of partition walls having a predetermined gap, and an inlet pipe connected to the large-diameter pipe between the partition walls, for flowing a chlorine agent into the large-diameter pipe. It is.

[0019]

According to the present invention, the ratio of the used water amount to the stored water amount is relatively small by providing two or more partitions provided in the large diameter pipeline in a direction perpendicular to the pipe axis of the large diameter pipeline at a predetermined interval. Even if the mixing and stirring of the chlorine agent and water are sufficiently performed,
No dead water is generated, and water can be easily replaced. In addition, as the number of partition walls is increased, the replacement time (water storage amount / used water amount) can be reduced. However, the effect saturates when the number of the partition walls exceeds a certain limit.

Next, the present invention will be described with reference to the drawings. FIG. 1 is a vertical longitudinal sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. 1 inside a large-diameter pipeline 1 with a circular cross section installed in a deep underground space
In the section, five partition walls 2 are provided at predetermined intervals in the pipe axis direction of the large diameter pipe line 1 in the pipe axis orthogonal direction. Each of the partition walls 2 is formed of a square plate whose four corners are in contact with the inner peripheral surface of the large-diameter pipeline 1. An inflow pipe 4 for flowing a chlorinating agent is connected to the large-diameter pipe 1 downstream of the most upstream partition 2a among the five partitions 2a. Further, an outflow pipe 6 is connected to the large-diameter pipe 1 on the upstream side of the most downstream partition 2b, and a sensor 5 for measuring the residual chlorine concentration is provided in the middle of the outflow pipe 6. .

The water in the large-diameter pipe 1 into which the chlorinating agent has flowed from the inflow pipe 4 passes through a gap between the peripheral portion of the plate forming the partition wall 2 and the inner peripheral surface of the large-diameter pipe 1. While repeating the mixing, the water proceeds sequentially downstream, and the water is replaced. In this embodiment, the number of the partition walls 2 is five (the number of the mixing chambers 3 formed by each partition wall 2 is four), but the number of the partition walls 2 is two or more (the number of the mixing chambers 3). The larger the number is (one room), the shorter the replacement time (water storage / water usage) can be. However,
When the number of the partition walls 2 exceeds a certain limit, the effect of shortening the replacement time is saturated. In the present invention, the number of the mixing chambers 3 is 3 to
Eight rooms are appropriate. Also, the aspect ratio of each mixing chamber 3 (horizontal /
1.64 is optimal for vertical). That is, the interval between the partition walls 2 (horizontal)
Is optimally 1.64 times the diameter (longitudinal) of the large diameter pipeline 1.
When the aspect ratio of the mixing chamber 3 is 1.64, the vortex does not become a stagnation area, but rather promotes the mixing process, and the fluid in the vortex is eventually carried downstream.

The chlorine agent flowing from the inflow pipe 4 includes:
Use either liquefied chlorine or sodium hypochlorite. Further, the position for injecting the chlorinating agent and the position of the device for generating hypochlorous acid may be on the ground or in a tunnel 8 provided with the large-diameter pipeline 1.

The injection control of the chlorine agent used in the present invention is desirably control of residual chlorine. This is because the present invention is suitable for operation in a low flow rate region. The residual chlorine concentration may be measured by the sensor 5 provided in the middle of the outflow pipe 6, and the measured amount may be used to control the injection amount of the chlorine agent. The chlorine agent injection equipment used in the present invention may be either a pressure type or a vacuum type.

As described above, a plurality of (five in this embodiment) partitions are provided in one section of the large-diameter pipeline, and a chlorine agent is injected from the inflow pipe 4 so that the inside of the section is
There is no excess or shortage of the residual chlorine concentration, and the residual chlorine concentration becomes uniform. Further, it is unlikely that the water once mixed and stirred uniformly in the compartment is separated. In addition, the amount of free residual chlorine consumed inside the large-diameter pipeline downstream can be set by calculation.
The standard value of 0.1 ppm or more can be satisfied. and,
The amount of the chlorine agent used can be reduced, and the production of trihalomethane and the like can be reduced.

Further, the present invention provides good mixing and stirring effects even when the average flow velocity of water in the large-diameter pipeline is as low as 1.5 to 5.9 mm / sec. The average flow velocity of a large diameter pipeline with stagnation is 10 mm / sec or less, and a sufficient effect can be expected even if the diameter is large. In particular, one of the reservoirs
The daily water supply is very low during the night and the average flow velocity is 10
mm / sec or less, and the effect of stirring and mixing by the large-diameter pipeline of the present invention can be sufficiently expected.

[0026]

As described above, according to the present invention, by making the concentration of the chlorinating agent injected into the pipeline uniform, drinking water suitable for drinking without generating dead water is supplied to the water tap. A large diameter pipeline that can be supplied is obtained, and thus
An industrially useful effect is provided.

[Brief description of the drawings]

FIG. 1 is a vertical longitudinal sectional view showing one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a graph showing a relationship between a chlorine injection rate and a residual chlorine concentration.

FIG. 4 is a sectional view of a water storage tank showing the prior art.

FIG. 5 is a graph showing the relationship between the number of mixing chambers and fresh water replacement time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Large-diameter pipe line 2 Partition wall 2a The most upstream partition wall 2b The most downstream partition wall 3 Mixing chamber 4 Inflow pipe 5 Sensor 6 Outflow pipe 7 Water storage tank 8 Tunnel 9 Mixing chamber 10 Partition plate.

Claims (2)

(57) [Claims] 1. A large-diameter pipe having a circular cross-section, which is provided underground at a large depth and through which water flows, and is fixed in a direction perpendicular to a pipe axis of the large-diameter pipe inside the large-diameter pipe. ,and,
A plurality of partition walls having a predetermined gap between the large-diameter pipeline and an inner peripheral surface of the large-diameter pipeline, provided at predetermined intervals in the pipe axis direction of the large-diameter pipeline, and the large-diameter space between the bulkheads. A large-diameter pipeline in which dead water is not generated, comprising: an inflow pipe connected to the pipeline for flowing a chlorine agent into the large-diameter pipeline. 2. The large-diameter pipeline without dead water according to claim 1, wherein the partition has a square plate body whose four corners contact the inner peripheral surface of the large-diameter pipeline. .