How to supply oxygen to stagnant water

Abstract

To provide an oxygen supply method capable of easily supplying oxygen to water stagnating in a waterway. [Solution] The oxygen supply method is a method for supplying oxygen to first water stagnating in a waterway. The oxygen supply method includes an arrangement step of arranging a submersible pump P and a hose H connected to the submersible pump P so as to suck in second water having a larger amount of dissolved oxygen than the first water and supply it into the waterway, and a supply step of operating the submersible pump P to supply the second water from the hose H into the waterway.

Description

[Technical field]

[0001] The present invention relates to a method for supplying oxygen to stagnant water. [Background technology]

[0002] In power plants, waterways are installed to take in and release cooling water used to cool steam. Because these waterways are open to the sea, marine organisms such as mussels that invade from the sea are attached to them. For this reason, if the intake and release of cooling water is stopped when power generation is stopped, the dissolved oxygen in the stagnant water in the discharge channel may become insufficient, causing the marine organisms to die and resulting in black water and foul odors. To solve these problems, various methods have been developed. For example, Patent Document 1 discloses a method of supplying oxygen to stagnant water by blowing air taken from the atmosphere into the stagnant water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-21646 Summary of the Invention [Problem to be solved by the invention]

[0004] The method of Patent Document 1 is extremely useful because it can prevent the death of marine organisms in stagnant water. However, depending on the shape of the waterway, divers must go underwater to install and remove the hose, which is time-consuming and labor-intensive.

[0005] The present invention has been made against this background, and has an object to provide an oxygen supply method that can easily supply oxygen to water stagnating in a waterway. [Means for solving the problem]

[0006] In order to achieve the above object, the oxygen supply method of the present invention comprises the steps of: 1. An oxygen supply method for supplying oxygen to first water retained in a waterway, comprising: an arrangement step of arranging a pump and a hose connected to the pump so as to suck in second water having a larger amount of dissolved oxygen than the first water and supply the second water toward the waterway; a supplying step of supplying the second water from the hose into the water channel by operating the pump; Includes. Effect of the Invention

[0007] According to the present invention, it is possible to provide an oxygen supplying method that can easily supply oxygen to water stagnating in a waterway. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2A is a plan view showing water flowing in both drainage channels according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view of the drainage channel in FIG. 2A taken along line AA. [Diagram 2] FIG. 2A is a plan view showing a state in which water is stagnant on one side of a discharge channel according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view of the discharge channel in FIG. 2A taken along line BB. [Diagram 3] 2 is a graph showing the change over time in the amount of dissolved oxygen in Example 1. [Figure 4] FIG. 13 is a photograph of the exterior of the hydraulic model in Example 2. [Diagram 5] FIG. 13 is a photograph of the upstream exterior of the hydraulic model in Example 2. [Figure 6] 6(a) to 6(c) are graphs showing the change over time in the amount of dissolved oxygen in Example 2. [Figure 7] 13(a) to 13(d) are diagrams showing average flow velocity vectors obtained by image analysis using fluorescent particles having a particle size of 0.6 mm or more in Example 3. FIG. [Figure 8]13(a) and (b) are diagrams showing average flow velocity vectors obtained by image analysis using fluorescent particles having a particle diameter of less than 0.6 mm in Example 3, and streamlines connecting the average flow velocity vectors, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an oxygen supply method according to an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals.

[0010] The oxygen supply method according to the embodiment is a method for supplying oxygen to water stagnating in a waterway by supplying water obtained from a waterway through which water flows toward the waterway in which water stagnates. Since the water obtained from the waterway through which water flows has a larger amount of dissolved oxygen than the water stagnating in the waterway, supplying such water can increase the amount of dissolved oxygen in the water stagnating in the waterway. The amount of dissolved oxygen is also called DO (Dissolved Oxygen) and indicates the amount of oxygen dissolved in the water. The water stagnating in the waterway is an example of the first water, and the water obtained from the waterway through which water flows is an example of the second water.

[0011] If marine life lives in a waterway with stagnant water, the marine life consumes the oxygen in the water, and if oxygen is not supplied, the amount of dissolved oxygen in the water in the waterway will gradually decrease. On the other hand, if water with a high amount of dissolved oxygen is supplied to a waterway with stagnant water, the amount of dissolved oxygen in the water in the waterway can be restored, and an environment in which marine life can survive in the water can be maintained. Below, we will explain using as an example the discharge channel of an operating power generation unit as a waterway with flowing water, and the discharge channel of a stopped power generation unit on the premises of the same power plant as a waterway with stagnant water.

[0012] Next, an example of the configuration of the tailrace of each power generating unit will be described with reference to FIG. 1. The arrows in FIG. 1 indicate the flow of water. Parts of each tailrace extend in parallel while adjacent to each other and separated by concrete walls. The tailrace is, for example, a waterway with a closed cross section (closed cross section waterway) and is formed by connecting multiple box culverts. The box culvert is a box-shaped concrete structure buried in the ground. Each tailrace extends downstream from a separate tailrace pond and discharges water toward a tailrace outlet that is open into the sea. Shellfish such as mussels enter the tailrace with the current of seawater and attach to the wall of the tailrace.

[0013] Each discharge channel is provided with a number of manholes MH that connect to the ground GL and extend downward. The manholes MH are installed at intervals along the length of each discharge channel, and each has a removable lid attached. The manhole MH closest to the discharge reservoir is configured so that a gate can be installed to block the flow of water from the discharge reservoir. When the lid of the manhole MH is removed, for example, a submersible pump can be lowered into the water or a hose connected to the submersible pump can be positioned toward the water surface. The above is the configuration of the tailwater channels for each generating unit.

[0014] Next, a flow of an oxygen supply method carried out by a user in a water discharge channel according to an embodiment will be described with reference to Fig. 2. As in Fig. 1, arrows in Fig. 2 indicate the flow of water. First, the manhole MH closest to the tailrace pond in each of the two adjacent tailrace channels is opened.

[0015] Next, in the discharge channel of the power plant to be inspected, a gate G is installed in the manhole MH on the tailrace pond side, and the tailrace pond upstream of gate G is drained while water is left stagnant downstream of gate G. At this time, no gate is installed in the other discharge channel, and water continues to flow from the tailrace pond side. Inspection of each part of the power plant, including the tailrace pond, can be carried out in this state. In the discharge channel of the power plant to be inspected, water remains stagnant downstream of gate G, so dissolved oxygen gradually decreases due to oxygen consumption by marine organisms. Note that the discharge channel is affected by the ocean tide level, but since the top of the discharge channel is lower than the lowest tide level, the water level does not decrease even if water stagnates in the discharge channel.

[0016] Next, the submersible pump P is placed in the waterway through which water is flowing, and the hose H connected to the submersible pump P is placed toward the waterway in which the water is stagnating (placement process). Specifically, the hose H connected to the submersible pump P is placed in the manhole MH of the waterway in which the water is stagnating, with its opening facing downward.

[0017] Next, by operating the submersible pump P, water is sucked from the discharge channel where water is flowing and supplied to the discharge channel where water is stagnating (supply process). In this process, the submersible pump P sucks water from the manhole MH of the other discharge channel, and after pulling it up to the height of the ground GL using the hose H and moving it over the ground GL, it is dropped into the manhole MH of one of the discharge channels from the opening of the hose H. When the water that falls into the manhole MH hits the water surface in the discharge channel, the water that is hit is mixed up and down in the water, and then flows toward the discharge outlet while being dispersed up and down. In addition, since water is injected into the discharge channel while the opening of the hose H is placed in the atmosphere, the amount of water injected into the discharge channel can be kept constant even if the water pressure in the discharge channel fluctuates due to the change in the sea tide level. Moreover, since the hose H is simply placed in the manhole MH, no construction such as gate modification is required, and the process can be carried out quickly and at low cost.

[0018] The amount of water injected is set so that the amount of dissolved oxygen in the water in the discharge channel where water is stagnant is equal to or greater than the control value. The control value of the amount of dissolved oxygen is set in advance, taking into consideration the type and amount of marine organisms attached to the discharge channel and the seawater temperature, so that the marine organisms living in the discharge channel can secure the oxygen they need to survive. It should be noted that the higher the seawater temperature, the more active the marine organisms become and the greater their oxygen consumption. As an example, if the main marine organisms are mussels and the seawater temperature is about 20°C, the control value of the amount of dissolved oxygen should be set to 2 mg / l. The discharge amount of the submersible pump P installed underwater in the discharge channel is selected according to the amount of water injected, and multiple units may be installed underwater.

[0019] Once the inspection of the generator unit is complete, the operation of the submersible pump P is stopped, and the submersible pump P and hose H are removed from the manhole MH of each discharge channel. Next, the gate G is removed from the manhole MH of the discharge channel where water has accumulated, and the cover of the manhole MH of each discharge channel is returned to its original position, completing the entire process. The above is the flow of the oxygen supply method in the discharge channel.

[0020] As described above, the oxygen supply method according to the embodiment includes an arrangement step of arranging a submersible pump P and a hose H connected to the submersible pump P so as to suck in water having a greater amount of dissolved oxygen than the water stagnating in the waterway and supply it into the waterway, and a supply step of supplying water having a greater amount of dissolved oxygen than the water stagnating in the waterway from the hose H into the waterway by operating the submersible pump P. This makes it possible to easily supply oxygen to the water stagnating in the waterway.

[0021] The present invention is not limited to the above-described embodiment, and the following modifications are possible.

[0022] (Modification) In the above embodiment, the waterway where water is retained and the waterway where water flows are both discharge channels with closed cross sections, but the present invention is not limited to this. Waterways formed with closed cross sections other than discharge channels, for example, closed cross sections of intake channels, water supply pipes, sewerage pipes, and pipelines, may also be used. Furthermore, each waterway may be a waterway with an open cross section (open cross section waterway), for example, a river, a canal, an irrigation channel, or a drainage channel.

[0023] In the above embodiment, water is obtained from a waterway where water flows, but the present invention is not limited to this. Water may be obtained from any water source as long as the water has a higher amount of dissolved oxygen than the water stagnating in the waterway. For example, a submersible pump P may be installed in the sea, and a hose H connected to the submersible pump P may be used to pump water into a manhole MH in the waterway where the water is stagnating.

[0024] In the above embodiment, the water is knocked down from the manhole MH of the waterway through which the water is flowing, but the present invention is not limited to this. For example, the water may be discharged by bringing the opening of the hose H close to the water surface of the waterway, or by disposing the opening of the hose H underwater.

[0025] In the above embodiment, the submersible pump P is used to obtain and release water, but the present invention is not limited to this. For example, a pump connected to both a suction hose and a release hose may be installed on land, the suction hose may be installed in a manhole MH of a waterway where water is flowing, and the release hose may be installed facing the manhole MH of a waterway where water is stagnating.

[0026] In the above embodiment, the pump is constantly operated so that the amount of dissolved oxygen in the water in the waterway where water is stagnant is equal to or greater than the control value, but the present invention is not limited to this. For example, a dissolved oxygen meter may be installed in the waterway where water is stagnant, and the dissolved oxygen meter may be communicatively connected to a control device that controls the operation of the pump via a wired or wireless communication line. The control device may include a memory and a processor, and may acquire the amount of dissolved oxygen measured by the dissolved oxygen meter by executing a program stored in the memory with the processor, and may control the pump to operate when the amount of dissolved oxygen is less than the control value.

[0027] The above-mentioned embodiments are merely examples, and the present invention is not limited to these, and various embodiments are possible without departing from the spirit of the invention described in the claims. The components described in the embodiments and modifications can be freely combined. In addition, inventions equivalent to the inventions described in the claims are also included in the present invention.

[0028] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples.

[0029] Example 1 In Example 1, it was verified whether it would be possible to recover dissolved oxygen by injecting water into the retention and discharge channel of a power generating unit undergoing regular inspection. In the retention and discharge channel, a gate was inserted into the manhole, causing water to accumulate downstream of the gate. In this verification, water was injected by knocking it down from a manhole that did not require gate modification. For water injection, a 6-inch submersible pump (displacement volume 3.3 m) was used. 3 / min) and water was taken from the tailwater of an adjacent operating power plant.

[0030] In order to understand the effect of changes in the amount and duration of water injection on the recovery of dissolved oxygen, tests were conducted under the following four conditions, and the amount of dissolved oxygen was measured for each: Condition 1: Three pumps operated 8 hours a day (intermittent operation), Condition 2: Three pumps operated 24 hours a day (constant operation), Condition 3: Two pumps operated 24 hours a day (constant operation), and Condition 4: One pump operated 24 hours a day (constant operation).

[0031] Dissolved oxygen was measured by dropping a portable multi-purpose water quality meter (ProDSS) into the manhole at the regular times of 8:00, 12:00, and 16:00 every day, and measurements were taken for 2 minutes in the upper, middle, and lower sections of the spillway, and the average value was calculated for each section. The upper, middle, and lower sections are 3.4 m, 2.0 m, and 0.6 m above the bottom of the spillway, respectively.

[0032] The results are shown in Figure 3. As expected, when no water was injected, a decrease in dissolved oxygen occurred due to marine life. Specifically, 96 hours after the gate was inserted into the manhole, the amount of dissolved oxygen in the upper part of the waterway fell below 2 mg / l, the amount necessary for marine life to survive. When tests were then conducted under condition 1, the amount of dissolved oxygen recovered once after water was injected, but by the next day it had fallen below the control value. Under condition 2, which was conducted subsequently, the necessary amount of dissolved oxygen could be maintained, but under conditions 3 and 4, the amount of water injected was less than under condition 2, resulting in a shortage of dissolved oxygen. From the above, it was confirmed that dissolved oxygen can be restored by constantly injecting a certain amount of water into the water retention discharge channel.

[0033] Example 2 In Example 2, a hydraulic model simulating a power plant's tailrace was used to investigate the position at which injected water would flow evenly within the tailrace. First, a 1 / 20 scale acrylic resin model (acrylic model) was created as shown in Figure 4. The cross section of the tailrace is a square with each side measuring 0.2 m. As the tailrace is 5 m long, the capacity of the tailrace that can be filled with water is 0.2 m. 3 (200L).

[0034] As shown in Figure 5, connectors were installed on the side wall on the upstream side of the model to allow water to be injected into the water from the upper, middle, and lower levels, and a structure simulating a manhole MH was also installed so that water could be knocked down from above. The upper, middle, and lower water injection connectors were installed 17 cm, 10 cm, and 3 cm from the bottom, respectively, taking into account the actual spillway. The model spillway was set up horizontally. This is because the actual spillway has a gradient of about 1 / 2000, and when this gradient is applied to the model, the difference in height is 2.5 mm for a length of 5 m, making the gradient negligible.

[0035] In the verification of the water injection position, first, the amount of dissolved oxygen was reduced by releasing nitrogen gas into the water in the model. Specifically, air stones were placed at five locations at the bottom of the model, and nitrogen gas was supplied to each air stone via a hose for 90 minutes, moving oxygen into the nitrogen gas bubbles and reducing the amount of dissolved oxygen in the water in the model. Next, water was injected into the model from each injection location using a pump, and a dissolved oxygen meter was inserted through the air holes at each of the measurement points A to E in Figure 4 to measure the time change in the amount of dissolved oxygen at each of the measurement points A to E. The water injection time was 5 hours, which is equivalent to 24 hours in the actual machine. The amount of water injected per unit time was 1.2 l / min, which is equivalent to 2.2 m of actual water. 3 / min. Measurement points A to E are located 50cm, 150cm, 250cm, 350cm, and 450cm away from the upstream side end face, respectively. The temperature of the injected water during the test was 6°C higher than the water temperature in the model (because the warm discharged water is 6°C higher than the seawater temperature).

[0036] As a result, at measurement point D, as shown in Figure 6(c), no significant difference was observed in the dissolved oxygen recovery tendency due to the difference in water injection position. However, at measurement points B and C, as shown in Figures 6(a) and (b), MH knock-down water injection was significant in terms of the dissolved oxygen recovery tendency.

[0037] Example 3 Next, the flow at each water injection position was visualized using a particle tracking method, and the water flow was analyzed. Specifically, fluorescent particles were poured into the manhole MH using the model of Example 2 as it was, and the fluorescent particles were tracked following the movement of the water by shooting with a high-speed video camera while irradiating it with a laser light source and performing image analysis. Other conditions were the same as in Example 2.

[0038] The fluorescent particles were divided into two groups: those with particle diameters of 0.6 mm or more, and those with diameters of less than 0.6 mm, and image analysis was performed on each group. Fluorescent particles with diameters of 0.6 mm or more tend to sink and are difficult to diffuse throughout, but are easy to visualize. On the other hand, fluorescent particles with diameters of less than 0.6 mm tend to spread throughout as they do not sink easily, but are difficult to visualize. Note that in this test, fluorescent particles with diameters of less than 0.6 mm could also be visualized by adjusting the lighting.

[0039] First, we will show the results of image analysis using fluorescent particles with a particle diameter of 0.6 mm or more. As shown in Figures 7(a)-(c) in order, in the upper stage water injection, middle stage water injection, and lower stage water injection, the fluorescent particles flowed while concentrating on the upper, middle, and lower sides of the channel, respectively. On the other hand, in the MH knock-down water injection, as shown in Figure 7(d), the fluorescent particles moved up and down near the MH, so that the fluorescent particles flowed uniformly on the downstream side.

[0040] Next, we will show the results of image analysis using fluorescent particles with a particle diameter of less than 0.6 mm. In the case of water injection by MH knocking, the average flow velocity vector is distributed over the entire area as shown in Figure 8(a), and the flow lines are widely spread as shown in Figure 8(b), which indicates that the injected water is uniformly diffused. From the above, it can be understood that water injection by MH knock-off easily restores dissolved oxygen from upstream to downstream, and the injected water flows uniformly from upstream to downstream. [Explanation of symbols]

[0041] H hose G Gate MH Manhole P Submersible pump

Claims

1. 1. An oxygen supply method for supplying oxygen to first water retained in a waterway, comprising: an arrangement step of arranging a pump and a hose connected to the pump so as to suck in second water having a larger amount of dissolved oxygen than the first water and supply the second water toward the waterway; a supplying step of supplying the second water from the hose into the water channel by operating the pump; 2. A method for supplying oxygen comprising the steps of:

2. The pump is a submersible pump that is installed underwater. The method for supplying oxygen according to claim 1.

3. A manhole is provided above the waterway, the manhole being connected to the ground and extending downward; In the supplying step, the second water sucked by the pump is dropped into the manhole. The method for supplying oxygen according to claim 1 or 2.

4. In the waterway, a gate is installed in the manhole to block water flowing from the upstream side of the gate. The method for supplying oxygen according to claim 3.

5. The second water is water flowing in a waterway different from the waterway. The method for supplying oxygen according to claim 1 or 2.

6. The waterway is a discharge channel for a generating unit under inspection, The waterway different from the waterway is a discharge channel for a power generating unit in operation installed in the same power plant premises as the power generating unit under inspection. The method for supplying oxygen according to claim 5.

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