JPH0557367B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Purpose of the Invention [Field of Industrial Application] The present invention relates to a method for preventing the intrusion of jellyfish into seawater intakes used for various types of industrial water, fisheries water, and the like.

[Conventional technology] Large amounts of seawater are used in cooling systems at chemical factories, thermal power plants, nuclear power plants, etc., but sometimes when jellyfish appear in large numbers in the sea,
Jellyfish cling to seawater intake screens and clog them, making it extremely difficult to take in seawater, resulting in situations where operations at factories, power plants, etc. have to be suspended.

In addition, in the aquaculture fishing industry that has become popular in recent years along the coast, if the seawater inflow network is closed due to an abnormally large number of jellyfish, it is difficult to replenish fresh seawater to the aquaculture facility. This can lead to serious losses such as the death of fish and shellfish.

There are several types of jellyfish that often occur in large numbers in the coastal waters of Japan, such as the moon jellyfish, red jellyfish, octopus jellyfish, Echizen jellyfish, andon jellyfish, among others, the moon jellyfish has a high occurrence frequency and has caused problems in seawater intake. It is the most common and therefore the most well known. Taking the moon jellyfish as an example, an overview of its ecology is as follows.

Many young jellyfish bodies appear in the sea around April every year, and by May and June, they are only about 1 cm in diameter, but they grow rapidly in early summer, and grow until October to November.
By the end of the year, the diameter of the umbrella becomes over 10cm, and the year is over. The lifespan is less than 2 years, and the diameter of the umbrella for large solids is 20
~30cm, reaching a wet weight of 300-800g.

In the morning and evening, and during the daytime on cloudy days, they swim on the surface of the ocean, and during the daytime on clear skies, they mostly swim in the middle layer from the surface to a depth of 2 to 3 meters. These jellyfish gather together under the influence of tides and wind, forming large band-shaped or oval-shaped communities. At night, the jellyfish stop swimming, so the group settles to the sea floor and floats around.

An example of a dense community at the sea surface is an area of approximately ^1500m2 , with an average umbrella diameter of
There are as many as 70 19.5cm moon jellyfish in every ^cubic meter of seawater, giving the sea a milky white color. For example, if such seawater is taken in at a flow rate of 3000 ^m3 per minute at a thermal power plant, the amount of jellyfish that collect on the intake screen will reach 30 tons (wet weight) in 30 seconds, and this will be removed by machinery. It is almost impossible to eliminate them in a short period of time.

By the way, rotating screens are installed as a jellyfish collection device in the headraces of thermal or nuclear power plants, but if there are too many jellyfish, the screens will become covered with jellyfish and water will not flow through the headraces. ,
At the same time, the screen may also become unable to rotate due to large water pressure.

Therefore, as a prior art, Japanese Patent Application No. 1983-4681 discloses a method for collecting water jellyfish that gather at a seawater intake.
This is housed in a closed container that has a supply port, a discharge port, and a steam inlet that can be opened and closed, and pressurized steam is introduced through the steam inlet to decompose and dissolve the water jellyfish, and the liquid melt is taken out from the discharge port. A method for completely disposing of water jellyfish has been described, which is characterized by the It is necessary to install the facility close to the water intake, which requires a huge amount of equipment and energy, making it expensive, and it is difficult to operate it all the time because it is impossible to predict when an abnormality will occur. They are completely powerless against it.

On the other hand, JP-A No. 51-139146 discloses a collection fence in which a large number of long and narrow iron plates are fixed in parallel by a machine at intervals that do not allow jellyfish to pass through, and the lower part of the plate is supported by pillars. The fence is installed along the inner circumferential surface of the headrace channel, facing diagonally upward from the bottom in the downstream direction, with the top end slightly protruding from the water surface, and a jellyfish receiving box and a work scaffold are placed near the top end of this collection fence. A method for collecting jellyfish in cooling water at a power plant is also described, which is characterized by the provision of jellyfish in cooling water at a power plant, but this is also not something that can be completely disposed of; If the collected jellyfish are crushed into small pieces and dumped into the sea, it will cause water pollution.If the jellyfish are transported to a land-based waste disposal site and disposed of by burial, filth will be spread during transportation, causing harmful effects, filling the disposal site, and creating a bad odor. All of them have the disadvantage of easily inducing environmental pollution, and they are also completely useless for aquaculture facilities built offshore, and the equipment itself is too large, but if poorly managed, dead jellyfish and General garbage, waste plastics, and other driftwood and other waste materials tend to clog and become dams, causing various problems such as the need for constant monitoring personnel. In either case, it is not practical and leads to the death of the jellyfish, and the world generally thinks that jellyfish are harmful and useless in the sea, but in reality they feed on red tide plankton and contribute to the purification of the sea. However, we must not forget that we ourselves play an important role in properly maintaining the marine ecosystem by becoming food for fish, and that the destruction of this ecosystem will lead to the destruction of the natural environment. It should be remembered.

[Problems to be Solved by the Invention] The present invention solves the drawbacks and problems of the prior art, has versatility, can effectively cope with aquaculture facilities built offshore, and exterminates jellyfish. The aim is to provide a method to prevent jellyfish from entering seawater intakes, etc., without destroying the ecosystem.

(2) Structure of the invention [Means for solving the problem] According to the present invention, air is supplied into the sea where jellyfish are swimming or sinking, and air bubbles are introduced into the inner cap and stomach cavity of the jellyfish. By floating it on the sea surface and damming it with a fence installed on the sea surface, it is possible to prevent it from entering seawater inlets and the like.

The body of a jellyfish has a specific gravity that is only slightly higher than that of seawater, but when air bubbles are taken into the stomach cavity through the inside of the umbrella or further through the mouth, the specific gravity of the jellyfish's body immediately becomes lower than that of seawater, and as a result, it loses its swimming ability. They are lost, float to the surface, and accumulate on the sea surface. Although the effect is the same with gases other than air, such as carbon dioxide or water vapor, it is practically most convenient to use air.

Air is supplied into the sea in the form of fine bubbles (0.1 mm to 2 cm) through perforated pipes, porous air diffusers, etc. on the sea floor or at a position midway between the sea bed and the sea surface. The bubbles cross the jellyfish's entry route.
It is possible to simply form the jellyfish in rows, but this is less effective against jellyfish that are facing sideways or on their backs, so it is preferable to form the jellyfish in 2 to 8 rows at appropriate intervals to be on the safe side.

The most effective air supply rate is 100 ml to 30 ml ^/ m3 of seawater per minute when jellyfish are present so densely that they cause problems with water intake. When the air supply rate is less than 100 ml per minute, it takes a long time for all the jellyfish to surface, which is not practical.
On the other hand, when the air supply rate exceeds 30 per minute,
The disadvantage is that the upward flow becomes too strong, causing the jellyfish's body to turn over, making it easier for the air bubbles accumulated in the cap to escape, impairing floating accumulation.

An example of a jellyfish levitation experiment using a moon jellyfish is shown below. 1 in an aquarium with a length of 1.8m, a width of 0.6m, and a height of 1m.
Fill the tank with ³ m3 of seawater (specific gravity: 1.02582), let 500, 90, or 30 moon jellyfish of different sizes swim around, and blow air into bubbles with a diameter of 1 to 3 mm using an air stone at the end of a vinyl tube inserted into the bottom of the tank. It was fed at a rate of 4 per minute. The time required for all jellyfish to float to the surface and accumulate was as follows.

500 jellyfish with an umbrella diameter of 8 to 12 cm...34 seconds 90 jellyfish with an umbrella diameter of 15 to 20 cm...1 minute 4 seconds 30 jellyfish with an umbrella diameter of 21 to 26 cm...1 minute 40 seconds Jellyfish floated like this can be easily prevented from entering the seawater intake or inflow side by damming it with a floating fence that follows the sea level, fences, etc. installed on the sea surface. The location to install fences, etc. is between the place where air is supplied into the sea and the seawater intake or seawater inflow side, but it depends on the depth of the sea, the speed of the tide and ocean current, the time it takes for the jellyfish to surface, etc. Determine an appropriate distance from the air supply location, taking into account the amount of air accumulated.

The width of the fence below the sea surface is usually about 60 cm, but when there is a large accumulation of jellyfish or when the waves are strong, the width is extended further downward. Further, in order to prevent jellyfish from passing under the fence and entering the fence, the fence may be installed with the lower end thereof extending in an L-shape in the direction of the jellyfish's intrusion direction.

It is not necessary to arrange fences etc. in a shape that surrounds the seawater intake or seawater inflow side, but instead, the jellyfish that have floated and accumulated are placed on ocean currents, tides, etc., and are guided by natural oceanographic removal methods in a direction that does not interfere with water intake or inflow. It is also a good idea to set up a system that allows the user to leave the room.

When a water intake is provided in an inland area via a long intake channel from the coast, the present invention can be applied to the intake channel. However, regarding the disposal of jellyfish caught on the water intake screen,
This is not a preferred method because it usually causes many of the problems mentioned in the prior art example.

By applying the present invention, a jellyfish that takes in air bubbles and floats to the surface will, within a few days, when its body is turned over by the impact of the waves, the air bubbles will be released from the umbrella and it will be able to swim normally. Air bubbles taken into the gastric cavity also escape through the jelly of the umbrella, and the through hole soon heals naturally and returns to its normal state. As described above, the present invention has the excellent feature of preserving the marine ecosystem in its natural state without causing environmental pollution.

Example 1 Aspects of the present invention will be explained using a first example.
Figures 1 and 2 show a seawater intake in a chemical factory located 0.5 to 2.5 m below the base level of the coast.
This figure shows how to prevent jellyfish intrusion when 6000 m ³ of seawater is taken in per hour through the bar screen 3 in the screen room 2.

Portable air compressors 4, 4' are placed on land and connected to air supply pipes 6, 6' on the seabed G by pressure-resistant rubber pipes 5, 5'. The two air supply pipes 6, 6' are kept at an interval of about 1 m, and are fixed close to the seabed G by sinkers 7, 7'.
Each pipe 6, 6' is a hard vinyl chloride pipe with an outer diameter of 34 mm connected with a rubber joint, and has a length of approximately 200 m.
It has an extension of 0.5 mm in diameter along both sides of the pipe wall at 1 cm intervals, and air is supplied from each compressor 4, 4' at a gauge pressure of 7 Kg/cm ² and a rate of 5 m ³ per minute. and bubbles a are ejected.

The average water depth of the air supply pipes 6, 6' is approximately 2.5 to 4.5 m depending on the tide, and the width of the air bubble a at the sea surface F is approximately 1.5 m.
The amount of seawater directly above 6' is estimated to be ^750-1350m3 , and the air supply rate corresponds to about 7-13 air per minute per ^1m3 of seawater.

On the other hand, a fence 8 is installed at a position near the water intake 1, which is approximately 50 m horizontally away from the positions of the air supply pipes 6 and 6'. Fence 8 is made of rubber and is sea level F.
It has a vertical width from float 9 to a water depth of 60 cm,
It is fixed in place with a sinker 10. The jellyfish J that has taken in the air bubbles a and floated to the surface is stopped by this sea level following floating type fence 8.

The air supply pipes 6, 6' and the sea level following flotation type fence 8 do not necessarily have to be installed in an arc as shown in the figure, but can be installed according to changes in the direction of invasion of the jellyfish J crowd, the passage of ships, etc. , may be changed as appropriate.

By the above measures, it was possible to intake seawater completely free of jellyfish J from the seawater intake port 1. In addition, Jellyfish J, which had been dammed up, was washed away by the currents caused by the tides to areas where it did not interfere with water intake.

Example 2 Next, aspects of the present invention will be explained using a second example.

Figures 3 and 4 show a part of the ocean with a fishing net 11.
We will show you how to prevent jellyfish from entering when the inside of the enclosure is used as a fish farming facility. The fishing net is held tied to a wooden frame 12 fixed to the sea surface F. The arrows in the figure indicate the direction in which the jellyfish J crowd moves along with the current.

An air compressor 13 is mounted on a ship S parked on the sea, and connected to an air supply pipe 15 in the sea through a pressure-resistant rubber pipe 14. The air supply pipe 15 has a total length
It is 120m long, has the same structure as Example 1, and is 4m below the sea level with the float 16 and sinker 17.
is fixed in position. Air is supplied to the pipe from an air compressor 13 at a gauge pressure of 5 kg/cm ² and a rate of 1 m ³ per minute, and bubbles a are ejected. The width of the bubble a row at the sea surface F is about 50 cm, and the amount of seawater directly above the air supply pipe 15 is estimated to be about 240 m ³ , so the air supply rate corresponds to about 4.2 per minute per 1 m ³ of seawater.

A fence 18 is installed at a position about 20 m or more away from the air feed pipe 15 toward the fish farming facility. Fence 18 is made of rubber and is float 1 at sea surface F.
It has a vertical width from 9 to 1.5 m in depth, and is fixed in a predetermined position by a sinker 20.

The jellyfish J, which floated up by taking in the air bubbles a, is stopped by the sea level following floating type fence 18,
The water is then guided and washed away using a natural ocean removal method in a direction that does not impede water intake for fish farming facilities.

By taking the above measures, the fish nets in the fish farming facility were not blocked by jellyfish J, and fresh seawater could be continuously taken in.

(3) Effects of the invention Thus, according to the present invention, the construction of equipment is easy, the construction period is short even if the scale is large, and the construction and operating costs are economical. It can be applied to any environment such as a deep place, and the construction form can be freely adapted to the target, and it is versatile and flexible.There is no need to bring the jellyfish to land and exterminate them, and the number of monitoring and collection workers is saved. It has the advantage of keeping the ecosystem healthy by allowing it to float and does not cause pollution problems.

In addition, the air supplied into the sea has excellent water purification power, and high-quality cooling seawater can always be taken in from the seawater intake, which has a positive impact on industrial equipment. The water purification effect and the agitation effect of air bubbles solve many of the pollution problems that have occurred in the past, and as a result, red tides no longer occur. Fish, shellfish, and seaweed tend to prefer fresh air bubbles, so they attract fish and jellyfish. It has the effect of suppressing the abnormal occurrence of jellyfish by feeding on jellyfish, and it also improves the natural environment, contributing to the reproduction of marine animals and plants, and having a positive impact on fishing, aquaculture, and cultivation, which not only affects the jellyfish problem but also the surrounding environment. The benefits are immeasurable.

[Brief explanation of the drawing]

Figures 1 and 2 are plan views and explanatory diagrams showing a first embodiment of the method of the present invention in a chemical factory, and Figures 3 and 4 show a second embodiment of the method of the present invention in a fish farming facility. FIG. 2 is a plan view and an explanatory diagram thereof. 1... Seawater intake, 4, 4', 13... Air compressor, 6, 6, 15... Air supply pipe,
8, 18... Fuens, 9, 16, 19... Float, 11... Fish net, 12... Wooden frame, F... Sea surface, a... Bubbles, J... Jellyfish, G... Seabed, S
……ship.

Claims (1)

[Claims] 1. A floating fence or net that follows the sea level and has the required water depth width from a float connected to a sinker with ropes or steel cables on the seabed is installed on the sea surface in the vicinity facing the seawater intake or seawater inflow side, and jellyfish groups are established. Air is supplied into the sea outside the fence or net where the jellyfish swim or settle and at an appropriate distance required for the jellyfish to surface, causing the group of jellyfish to rise to the sea surface, and the fence or net is used to remove the seawater. A method to prevent jellyfish from entering seawater intakes, etc., by temporarily blocking the intrusion into the intake or seawater inflow side, and then guiding the jellyfish away by using a natural oceanographic removal method that uses tidal currents to move the jellyfish to areas where they do not interfere with water intake.