WO2024039247A1

WO2024039247A1 - Transfer of fish from a first tank to a second tank

Info

Publication number: WO2024039247A1
Application number: PCT/NO2023/000003
Authority: WO
Inventors: Aga Morten
Original assignee: Searas As
Priority date: 2022-08-15
Filing date: 2023-08-14
Publication date: 2024-02-22
Also published as: NO20220881A1

Abstract

A solution for the gentle transfer of marine organisms from a first tank to a second tank at a higher level is described. The first tank is pressurized, and gas is introduced into the pipeline between the two tanks.

Description

Title: Transfer of Fish from a First Tank to a Second Tank

Field of Invention

The present invention pertains to a device and method for enhancing the lifting height in the process of pumping fish within a primarily vertical pipe system. The method involves the introduction of gas into a water flow at a lower section of the vertical pipe system, resulting in a lighter liquid column within the pipe. This introduction of gas at the lower end of the primary vertical pipe system decreases liquid density, thereby extending the lifting height for the water. Consequently, this provides an exceptionally gentle means of lifting fish by a few additional meters. The gas or air injection into the pipe system is combined with the pressurization of the tank from which the fish are to be transferred.

Background of the Invention

With the growing environmental challenges connected to open-sea farming of marine species, an increasing portion of production is shifting to closed tanks. Meeting the demand for increased production and yield necessitates the transfer of fish from one tank to another as they grow. The value of the water, which houses marine organisms, makes it impractical to move fish by emptying these large tanks, as it is time-consuming and costly. Hence, the fish must be transferred along with the water to a new tank, while maintaining consistent tank levels. Maximizing tank volumes for production and ensuring maximum biomass in the tanks at all times are the goals.

Fish transfer comprises two primary steps: initially, the fish must be brought to a specific location, and then the fish are moved or transferred to another tank. The herding process is crucial as it induces stress reactions in the fish, leading to increased oxygen consumption and carbon dioxide release. This stress can cause the fish to stop eating. Simultaneously, the actual transportation of fish can subject them to significant mechanical and physical stresses, particularly when the fish are large (3-7 kg). It is essential that both the guiding and the transfer process are as gentle as possible. Description of Prior Art

Fish transfer typically occurs from a lower level to a higher level, and various methods are currently employed for this purpose. These methods include directing the fish into a pipe system for further transportation. Standard fish pumps or tank pressurization systems are utilized to convey fish through pipes to a different location. Often, a combination of these methods is employed.

Several patents exist concerning fish transfer. Some are mentioned below along with comments:

Patent number NO306142 illustrates an alternating fish elevator.

Patent number NO325942 depicts a device for extracting fish from a trawl into a vessel.

Patent number NO341228 outlines a solution where fish are lifted in a vacuum, sorted, and then released into tanks. This system constitutes a completely closed system in which a vacuum is maintained throughout the entire process, encompassing a fish-receiving tank, a sorting mechanism, and a pump to create pipe system circulation for the transfer of water and fish. A vacuum pump sustains the vacuum within this closed system. While effective, this solution is complex and costly, requiring large tanks and systems to be placed under vacuum conditions.

The present invention can be used in conjunction with existing methods and provides a gentle means to enhance the lifting height for these methods.

Object of the Invention

The object of the invention is to provide a system for transferring fish gently from a source tank (e.g., a fish tank or wellboat) to another tank, often situated at a higher level. This system can be employed in conjunction with standard solutions like fish pumps or operate independently. The solution relies on pressurizing the source tank and introducing gas into the lower section of the pipe connecting the two tanks, preferably within a primarily vertical portion of the pipeline. This creates a lighter water column in the pipeline (lower self-weight), thereby increasing the lifting height of both the water and fish. The introduced gas can either be released directly into the air at the outlet, where water and fish are separated, or it can be part of a closed pipe system where a vacuum fan extracts air from the top. In this closed system, water and fish flow down into a tank with a water level significantly higher than the originating tank.

The primary objective of the invention is to elevate the lifting height of a fish transport system, ensuring the transportation process remains gentle on the fish. Current fish pumps designed to lift fish into a tank often have limitations regarding the size of fish they can accommodate. Summary of the Invention

The present solution incorporates two fundamental principles for transferring liquid and marine organisms from a closed first tank to a second tank:

Pressurizing the first tank, and

Introducing gas into the pipeline between the two tanks.

As such, the present invention encompasses a device for moving marine organisms from a first tank containing liquid at a specific level to a second tank positioned at a higher level. The device involves the use of a pipeline connecting the two tanks for the transfer of marine organisms. The first tank is sealed or closed, and pressurization of this tank is applied to force the liquid and marine organisms into the pipeline. Additionally, a compressor introduces gas into the lower portion (18a) of the pipeline.

In one embodiment, sections of the pipeline extend beneath the level of the tank on the wellboat.

In another embodiment, a siphon is used to draw liquid from the first tank into the second tank via the pipeline, facilitated by a vacuum pump that removes air from the top of the siphon. This process effectively transfers marine organisms and liquid to the second tank.

In yet another embodiment, the siphon returns the liquid to the first tank while retaining the marine organisms in the second tank.

In some embodiments, equipment components such as air pumps, air introduction systems, sensors, etc., may be installed on the wellboat.

In a second aspect, the invention pertains to a method for transferring marine organisms within a liquid, such as water, from a first tank to a second tank located at a higher level, wherein the method involves adding gas via a compressor into a vertical segment of a pipeline connecting the first tank to the second tank, wherein this addition of gas lightens the weight of the liquid within the pipeline, enabling the water and marine organisms to be raised to a higher level, and wherein, simultaneously, the first tank is pressurized using a compressor.

In one embodiment, a sensor monitors the liquid level in the tank and adjusts the gas injection rate into the pipeline accordingly.

In all aspects and embodiments outlined above, the marine organisms primarily refer to fish. Description of Figures

Preferred embodiments of the invention will be further elucidated with reference to the accompanying figures:

Figure 1 schematically illustrates a setup for transferring fish from a tank in a wellboat to a higher tank.

Figure 2 schematically outlines a solution in accordance with the invention, wherein fish from a tank in a wellboat are transferred to a higher tank. In this scenario, the tank on the wellboat is pressurized, and gas is introduced into the pipeline connecting the two tanks to extend the lifting height.

Figure 3 schematically demonstrates how the pipeline is extended into the tank on the wellboat, achieve greater vertical height for the added gas to act upon.

Detailed Description of Preferred Embodiments of the Invention

Figure 1 schematically illustrates how marine organisms 11, such as fish, can be transferred from the tank 10 on a wellboat 12 to a higher-level tank 34. This transfer can be carried out using conventional methods such as pumping and suction of fish through the pipeline 16. This can be quite rough, especially for larger fish, and the present invention seeks to establish a system where fish are transferred more gently.

Specific challenges that can be addressed by the invention include the transportation of fish from tank 10 on a wellboat 12 to a land-based facility, as shown in Figures 1-3. Typically, a land-based aquaculture facility can be located 3 meters above sea level. If the water level in the tank is 8 meters, there will be an 11-meter difference between the normal water level and the water level in the aquaculture tank 34. A typical wellboat designed to pump fish upwards may have a fish lifting height of 10 meters. The wellboat 12 closes the tanks 10 on the wellboat 12 and generates an overpressure in tank 10, providing a lifting height of typically 10 meters. This means that, for example, during low tide at 1 meter below normal sea level, the wellboat could lift 10 meters - 1 meter low tide = 9 meters above normal water level. The tank is at 11 meters (tank bottom 3 meters + water level in the tank 8 meters = 11 meters). This means that there is a shortfall of 2 meters in transporting the water from the wellboat into the aquaculture tank. Previous solutions have included a hatch in the aquaculture tank 34, located, for example, 3 meters below the normal tank level, and then lowering the water level in the tank below this hatch so that the wellboat 12 can pump water into the aquaculture tank 34. Figure 1 illustrates a traditional solution where the wellboat 12's pump delivers water and fish to a tank 34 where the water level is lowered by 3 meters (similar concept to patent application N020201424). A lowered tank 34 will have a higher fish density as the emptying of the wellboat 12 approaches its end. The example shows that the water volume in the tank is reduced by 3/8. The density in a tank used for fish farming can typically be 70 kg/m³ with water. Higher density requires more water circulation and opportunities to remove CO2 and add O2. In a holding tank used to store fish before they go to the slaughterhouse, higher densities can be expected since there is no feeding in the tank, and therefore, the O2 consumption will normally be lower. However, it is expected and observed that fish use a lot of O2 when stressed. This especially applies when they are pumped from a wellboat. It is therefore not desirable to have reduced water volume in the tank receiving the fish.

The present invention solves this challenge by having a compressor 18 supplement compressed air at the bottom 18a of the vertical pipeline 16 from tank 10 on the wellboat 12 to tank 34. When compressed air is blown into a vertical water column, the self-weight of the water in the water column is reduced. This will cause the water level to rise higher. In addition, tank 10 on the wellboat is pressurized further to promote the transport of fish through pipeline 16.

Figure 2 shows how air is blown into the vertical pipe 16. Assuming (example 1) that the pipe 16 is approximately 9 meters long, and it flows at 200 liters per second in the pipe 16, blowing in about 20 liters per second of air will cause the liquid column to rise approximately 0.9 meters since there is about 10% air in the water in the vertical section. The pressure at which the air is pumped into the pipe 16 is directly related to the height of the liquid column. There are several ways to increase the lift of the water. The most straightforward is to increase the amount of air pumped into the pipe 16. However, there is a limitation to how much this can contribute because the density of the water with the air blown in will reduce the density and thus the lifting properties of the water. Normally, fish have approximately the same self-weight as water. When air is pumped into the water, the fish will have a higher self-weight. There will, therefore, be a limitation on the proportion of air to water with the consideration that the fish, with higher self-weight, can be lifted with the water.

Another method to increase the lifting height is to increase the distance from the point where the air is pumped into the vertical pipe to the top of the pipe 16, where water and air are discharged into the atmosphere. An installation where the height from the point where the air enters and to the outlet is increased to 12 meters (example 2), and 200 liters per second flow in the pipe, blowing in about 20 liters per second of air will cause the liquid column to rise approximately 1.2 meters, as there is about 10% air in the water in the vertical part. This is compared to 0.9 meters from example 1. It is possible to arrange the system so that the vertical part from where the air enters to the outlet is such that the height allows the water to be lifted to the desired level. One can imagine that the air enters 30 meters below the outlet, which would provide a potentially much higher lifting height.

Figure 2 is a sketch of a system where a tank 10 contains liquid, such as water and marine organisms, such as fish, to be moved up one level. In the embodiment shown in Figure 2, the tank 10 is a wellboat 12. An air compressor 14 pumps compressed air into tank 10 on the wellboat 12, for example, up to a maximum of 1 bar. This pressure will push the water out of the wellboat 12 through a pipeline 16 to a vertical level in the pipeline (indicated as A in Figure 2), which corresponds to the pressure above the liquid level in tank 10. The details of wellboat design will not be discussed here, but typically, the available pressure and accompanying water level will be sufficient for the water to start flowing through the pipeline 16 to the outlet 16a. In other words, the outlet must be below level A where the pressure can lift the water. We can see from Figure 2 that the remaining height (indicated as B in Figure 2) is the height that remains to lift the water before it starts flowing from tank 10 on the wellboat 12 to outlet 16a.

Figure 2 also shows an air compressor (18) that pumps air into the vertical pipeline (16) through the inlet point (18a). This air compressor (18) has the capacity to inject air at a pressure that typically exceeds the pressure at the inlet point (18a) of the pipeline (16) and at a rate that eases the flow of the liquid, causing the water to overflow at the outlet (6). The underlying principle for increasing the lifting height is that the density of the liquid column is reduced by introducing gas or air at the bottom (25) of the pipeline (16).

The process that initiates the transfer of fish from the wellboat to the fish tank may involve the wellboat (12) pressurizing the tank (10) with a compressor (14) and pumping up a liquid column in the vertical pipe (16). Subsequently, a pressure sensor (20) can measure the pressure at the inlet (18a). The pressure will correspond to the height of the water column in the vertical pipeline (16). This height will vary due to several factors, including the pressure in the wellboat tank (10), the water level in the wellboat tank (10), tides, water density, and more. Typically, there is a barrier (22), such as a grate, at the inlet (18a) to the pipeline (16) on the wellboat (12) that transports fish to the outlet (16a). This barrier prevents fish from entering but allows water to pass through. When the pressure is measured by sensor 20, the air pump (18) will inject air into the vertical pipe (16) at a quantity and pressure that generates the desired flow of water from tank 10 in the wellboat (12) to outlet 16a based on the pressure recorded by sensor 20. The water flow will be recorded in a water flow meter (24) as water overflows at outlet 16a and returns to tank 10 in the wellboat (12), where a water pump (26) pumps the water back into tank 10. The return water pump (26) needs to overcome the pressure in tank 10. Once a stable and desired water flow is established, the fish can be released by opening the barrier (22). The fish at the inlet of the open barrier (22) will be sucked up into the pipeline (16) and transported to the outlet (16a). In this case, the water can flow back to tank 10 in the wellboat 12 without the need for the pump (26) to operate. This is because the water level in the return pipe (28) will have a higher pressure head than the counterpressure in tank 10. Changes in the water level in tank 10 can be monitored by sensor 20. This may be due to changes in tides or ballasting of wellboat 12, level regulation in tank 10, etc. The amount of air pumped by pump 18 at inlet 18a will then vary based on the desired water flow. When fish and water reach outlet 16a, the water from tank 10 in wellboat 12 will flow back to the wellboat 12, while fish will pass over a grate (30) with an opening that prevents fish from passing through. Smaller fish, such as wrasse, etc., as well as water, will pass through the grate (30). The fish will then be transferred to a new water system. The driving force in this system is a water pump (32) with the capacity to move water in a way that allows fish to flow from the grate (30) to the new tank (34). Water pump (32) can typically draw water from an intake well, or when transferring fish between different tanks, it can draw water from one of the tanks (10, 34). This may involve a new transport channel or a piping system (36) that moves fish to a new tank (34). The water level (indicated as C in Figure 2) in the tank (34) receiving fish will typically be lower than the outlet in the piping system (36), allowing water to flow freely into tank 34. Different solutions may also be employed to separate water before it enters tank 34. It's also possible to use a similar solution of injecting air into a vertical pipe to further lift the water in this water system. When all the fish are gathered at the inlet of tank 10 and have exited tank 10, the system should run for a period to ensure that all the fish have been transferred to the new tank (34). Water levels are indicated in the sketch. LAT (Lowest Astronomical Tide) (indicated as D in Figure 2) can serve as a reference low water level for lifting fish into the new tank (34). The tanks typically have a bottom located at 3 meters (E in Figure 2) above sea level (F in Figure 2).

An alternative solution could be to move all or some of the equipment components onto the wellboat.

Claims

Patent Claims

1. A device for transferring marine organisms (11) from a first tank (10) containing liquid at a given level to a second tank (34) at a higher level, characterized in that a pipeline (16) is arranged between the first tank (10) and the second tank (34) for transferring the marine organisms, and the first tank (10) is closed and pressurized to force the liquid and the marine organisms (11) into the pipeline (16), and a compressor (18) supplies gas to a lower portion (18a) of the pipeline (16).

2. A device according to claim 1, characterized in that portions of the pipeline (16) extend below the level of the tank (10) on the wellboat (12).

3. A device according to claim 1, characterized in that liquid is drawn from the first tank (10) through the pipeline (16) to the second tank (34), by providing a siphon between the two tanks (10,34), by a vacuum pump drawing air from the top of the siphon, and transferring the marine organisms and liquid to the second tank (34).

4. A device according to claim 3, characterized in that a siphon returns the liquid to the first tank (10), while the marine organisms (11) remain in the second tank (34).

5. A device according to claim 1, characterized in that parts or all of equipment such as air pumps, air injection, sensors, etc., are installed on said wellboat (12).

6. A method for transferring marine organisms (11) in a liquid, such as water, from a first tank (10) to a second tank (34) at a higher level, characterized in that gas is added via a compressor (18) in a vertical section of a pipeline (16) between the first tank (19) and the second tank (34) to reduce the specific gravity of the liquid in the pipeline (16) so that the water and marine organisms (11) are lifted to a higher level, while the first tank (10) is pressurized via a compressor (14).

7. A method according to claim 1, characterized in that a sensor (20) detects the liquid level in the tank (10) and regulates the amount of gas pumped into the pipeline (16).

8. A method according to claim 1, characterized in that said marine organisms (11) are fish.