Method for supplying oxygen to remaining water

Abstract

To provide an oxygen supply method that can easily supply oxygen to water remaining in a waterway.SOLUTION: An oxygen supply method is a method for supplying oxygen to first water remaining 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 that second water having a greater amount of dissolved oxygen than the first water is sucked in and supplied into the waterway; and a supply step of operating the submersible pump P to supply the second water through the hose H into the waterway.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Power plants are equipped with waterways for receiving and discharging cooling water used to cool steam. Because these waterways are open to the sea, marine organisms such as blue mussels that invade from the sea attach to them. Therefore, if the intake and discharge of cooling water are 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. Various methods have been developed to solve these problems. 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] Japanese 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 as it can prevent the death of marine organisms in stagnant water. However, depending on the shape of the waterway, it is necessary for divers to go underwater to install and remove the hose, which requires time and effort.

[0005] The present invention has been made based on the above 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: An oxygen supply method for supplying oxygen to first water stagnating in a waterway, comprising: an arrangement step of arranging a pump and a hose connected to the pump so that second water having a larger amount of dissolved oxygen than the first water can be sucked and supplied into the waterway; a supplying step of supplying the second water from the hose into the water channel by operating the pump; Includes: [Effects of the Invention]

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

[0008] [Figure 1] FIG. 1(a) is a plan view showing water flowing in both discharge channels according to an embodiment of the present invention, and FIG. 1(b) is a cross-sectional view of the discharge channel in FIG. 1(a) taken along line AA. [Figure 2] FIG. 1(a) is a plan view showing a state in which water is stagnating on one side of a discharge channel according to an embodiment of the present invention, and FIG. 1(b) is a cross-sectional view of the discharge channel in FIG. 1(a) taken along line BB. [Figure 3] 1 is a graph showing the change in the amount of dissolved oxygen over time in Example 1. [Figure 4] FIG. 10 is a photograph of the exterior of the hydraulic model in Example 2. [Figure 5] FIG. 10 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 in the amount of dissolved oxygen over time in Example 2. [Figure 7] 10(a) to 10(d) are diagrams showing average flow velocity vectors obtained by image analysis using fluorescent particles having a particle diameter of 0.6 mm or more in Example 3. FIG. [Figure 8]10(a) and 10(b) are diagrams showing the mean flow velocity vectors obtained by image analysis using fluorescent particles with a particle diameter of less than 0.6 mm in Example 3, and the streamlines connecting the mean flow velocity vectors, respectively. DETAILED DESCRIPTION OF THE INVENTION

[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 designated by the same reference numerals.

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

[0011] If marine life lives in a waterway with stagnant water, the marine life will consume 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 dissolved oxygen content is supplied to a waterway with stagnant water, the amount of dissolved oxygen in the water in the waterway will be restored, and an environment in which marine life can survive in the water will be maintained. Below, we will explain using as examples the discharge channel of an operating power generation unit as a waterway with flowing water, and the discharge channel of a power generation unit that is shut down on the same power plant premises as a waterway with stagnant water.

[0012] Next, an example of the configuration of the discharge channels of each power generation unit will be described with reference to FIG. 1. Arrows in FIG. 1 indicate the flow of water. Parts of each discharge channel extend adjacent to each other and parallel to each other, separated by concrete walls. The discharge channels are, for example, waterways with closed cross sections (closed-section waterways) and are formed by connecting multiple box culverts. Box culverts are box-shaped concrete structures buried underground. Each discharge channel extends downstream from a separate discharge pond and discharges water toward a discharge outlet that opens into the sea. Shellfish such as mussels enter the discharge outlet with the current of seawater and attach to the walls of the discharge channels.

[0013] Each discharge channel is equipped with multiple 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 cover. 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. Removing the cover of the manhole MH makes it possible, for example, to lower a submersible pump into the water or position the hose connected to the submersible pump toward the water surface. The above is the configuration of the discharge channels for each generating unit.

[0014] Next, the flow of the oxygen supply method carried out by the user in the discharge channel according to the 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 discharge pond in each of the two adjacent discharge channels is opened.

[0015] Next, in the discharge channel of the power plant to be inspected, gate G is installed inside manhole MH on the tailrace pond side, and the tailrace pond upstream of gate G is drained while water remains stagnant downstream of gate G. At this time, no gates or other gates are installed in the other discharge channel, and water continues to flow from the tailrace pond side. In this state, inspections of each part of the power plant, including the tailrace pond, can be carried out. 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 ocean tides, but because the top of the discharge channel is lower than the lowest tide level, the water level does not decrease even if water remains stagnant 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 where water is stagnating (placement process). Specifically, the hose H connected to the submersible pump P is placed in the manhole MH of the waterway where water is stagnating so that its opening faces downward.

[0017] Next, submersible pump P is operated to suck water from the flowing discharge channel and supply it to the stagnant discharge channel (supply process). In this process, submersible pump P sucks water from manhole MH of the other discharge channel, and then uses hose H to raise it to ground level GL and move it over the ground level GL. After that, the water is dropped from the opening of hose H into manhole MH of one discharge channel. When the water falling into manhole MH hits the water surface of the discharge channel, it is stirred up and down in the water and then flows toward the discharge outlet while remaining dispersed up and down. Furthermore, because water is injected into the discharge channel while the opening of hose H is open to the atmosphere, the amount of water injected into the discharge channel can be maintained constant even if the water pressure in the discharge channel fluctuates due to changes in the ocean tide level. Moreover, because only hose H is placed inside manhole MH, no construction work 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 dissolved oxygen content of the water in the discharge channel where water is stagnant is above the control value. The control value for dissolved oxygen is set in advance to ensure that the marine organisms living in the discharge channel have enough oxygen to survive, taking into account the type and amount of marine organisms attached to the discharge channel and the seawater temperature. It is important to note 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 around 20°C, the control value for dissolved oxygen should be set to 2 mg / L. The discharge volume of the submersible pump P installed underwater in the discharge channel is selected according to the required amount of water injection, and multiple pumps may be installed underwater.

[0019] Once the inspection of the generator unit is complete, 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 manhole MH cover of each discharge channel is returned to its original position, completing the entire process. The above is the flow of 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 that water having a higher dissolved oxygen content than the water stagnating in the waterway can be sucked in and supplied into the waterway, and a supply step of supplying water having a higher dissolved oxygen content 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] (Variation) In the above embodiment, the waterways where water stagnates and the waterways 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, such as closed 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), such as a river, canal, irrigation channel, or drainage channel.

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

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

[0025] In the above embodiment, a submersible pump P is used to acquire 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, with the suction hose installed inside a manhole MH in a waterway where water is flowing, and the release hose installed facing inside a manhole MH in 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 waterway where water is stagnating is equal to or greater than the control value. However, the present invention is not limited to this. For example, a dissolved oxygen meter may be installed in the waterway where water is stagnating and 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 execute a program stored in the memory in the processor to obtain the amount of dissolved oxygen measured by the dissolved oxygen meter and control the pump to operate when the amount of dissolved oxygen is below the control value.

[0027] The above-described embodiments are merely examples, and the present invention is not limited to these. Various embodiments are possible within the scope of the invention as set forth in the claims. The components described in the embodiments and modifications can be freely combined. Furthermore, inventions equivalent to the inventions set forth 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 the recovery of dissolved oxygen could be expected by injecting water into the reservoir discharge channel of a power generating unit undergoing periodic inspection. In the reservoir discharge channel, a gate was inserted into a manhole, causing the downstream side of the gate to be in a reservoir state. In this verification, water was injected by knocking it down through 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 discharge channel of an adjacent power generating unit in operation.

[0030] In order to understand the effect that changes in water injection volume and duration have 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 operating 8 hours a day (intermittent operation), Condition 2: Three pumps operating 24 hours a day (constant operation), Condition 3: Two pumps operating 24 hours a day (constant operation), and Condition 4: One pump operating 24 hours a day (constant operation).

[0031] To measure the amount of dissolved oxygen, a portable multi-purpose water quality meter (ProDSS) was dropped into the manhole at regular times every day at 8:00, 12:00, and 16:00, and measurements were taken for two minutes in the upper, middle, and lower sections of the discharge channel, 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 discharge channel, respectively.

[0032] The results are shown in Figure 3. As expected, when no water was injected, the dissolved oxygen level decreased due to marine life. Specifically, 96 hours after the gate was inserted into the manhole, the dissolved oxygen level in the upper part of the waterway fell below 2 mg / L, the amount necessary for marine life to survive. When the test was then carried out under condition 1, the dissolved oxygen level recovered once after water was injected, but by the next day it had fallen below the control value. Under condition 2, which was carried out subsequently, the necessary dissolved oxygen level was 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 stagnation discharge channel.

[0033] Example 2 In Example 2, a hydraulic model simulating the discharge channel of a power plant was used to investigate the water injection position where injected water flows evenly within the discharge channel. First, a 1 / 20 scale model (acrylic model) made of acrylic resin (shown in Figure 4) was created. The cross section of the discharge channel is a square with sides of 0.2 m. Since the length of the discharge channel is 5 m, the volume of water that can be filled in the discharge channel 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 poured into the water from the upper, middle, and lower levels, and a structure simulating a manhole (MH) was also installed to allow water to be poured down from above. The upper, middle, and lower water injection connectors were located 17 cm, 10 cm, and 3 cm from the bottom, respectively, taking into account the actual discharge channel. The model discharge channel was set up horizontally. This is because the actual discharge channel has a gradient of about 1 / 2000, and when this gradient is applied to the model, the difference in elevation over a length of 5 m is 2.5 mm, making the gradient negligible.

[0035] To verify 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, causing the oxygen to move 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 dissolved oxygen meters were inserted through the air holes at each of measurement points A to E in Figure 4 to measure the time change in the amount of dissolved oxygen at each of measurement points A to E. The water injection time was 5 hours, which is equivalent to 24 hours in the actual equipment. The amount of water injected per unit time was 1.2 l / min, which is equivalent to 2.2 m of water in the actual equipment. 3 / min. Measurement points A to E were located 50cm, 150cm, 250cm, 350cm, and 450cm away from the upstream side end face, respectively. The injected water temperature during the test was 6°C higher than the water temperature inside the model (because the warm discharged water is 6°C higher than the seawater temperature).

[0036] As a result, as shown in Figure 6(c), at measurement point D, no significant difference was observed in the tendency for dissolved oxygen to recover due to differences 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 tendency for dissolved oxygen to recover.

[0037] Example 3 Next, the particle tracking method was used to visualize the flow at each water injection position and analyze the water flow. Specifically, fluorescent particles were poured into the manhole MH using the model from Example 2 as is, and the fluorescent particles were tracked by shooting with a high-speed video camera while irradiating it with a laser light source and analyzing the images. The 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 particle diameters of less than 0.6 mm, and image analysis was performed on each group. Fluorescent particles with particle diameters of 0.6 mm or more tend to sink and are difficult to diffuse throughout the sample, but are easy to visualize. On the other hand, fluorescent particles with diameters of less than 0.6 mm tend to sink and are easy to diffuse throughout the sample, but are difficult to visualize. In this test, fluorescent particles with diameters of less than 0.6 mm could also be visualized by adjusting the lighting.

[0039] First, we present the results of image analysis using fluorescent particles with a particle diameter of 0.6 mm or more. As shown in Figures 7(a) to 7(c) in order, in the upper, middle, and lower water injection stages, the fluorescent particles remained concentrated at the upper, middle, and lower parts of the channel as they flowed. On the other hand, in the MH knock-down water injection stage, as shown in Figure 7(d), the fluorescent particles moved up and down near the MH, resulting in a uniform flow of fluorescent particles downstream.

[0040] Next, we 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 knocking down MH, the mean flow velocity vector is distributed throughout the entire area as shown in Figure 8(a), and the streamlines are widely spread as shown in Figure 8(b), which indicates that the injected water is uniformly dispersed. From the above, it can be understood that water injection by MH knock-off facilitates the recovery of 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. An oxygen supply method for supplying oxygen to first water stagnating in a waterway, comprising: an arrangement step of arranging a pump and a hose connected to the pump so that second water having a larger amount of dissolved oxygen than the first water can be sucked and supplied into the waterway; a supplying step of supplying the second water from the hose into the water channel by operating the pump; An oxygen supply method comprising:

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

3. A manhole is provided in the waterway, In the supplying step, the second water sucked by the pump is dropped into the manhole. The oxygen supply method 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 oxygen supply method according to claim 3.

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

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

Images