EP2916937A1

EP2916937A1 - Device for mixing of gaseous liquid in liquid

Info

Publication number: EP2916937A1
Application number: EP13852582.9A
Authority: EP
Inventors: Victor Fiveland
Original assignee: Artec Holding As
Current assignee: Artec Holding As
Priority date: 2012-11-06
Filing date: 2013-10-30
Publication date: 2015-09-16
Also published as: NO335343B1; CL2015001114A1; NO20121306A1; EP2916937A4; WO2014073974A1

Abstract

Injector for mixing of gas-enriched liquid into flowing liquid, whereby the device comprises an inlet (10), and an outlet means (12) for the gas-enriched liquid arranged to be mounted into a pipe (11) with the flowing liquid. The outlet means (12) is provided with one or more outlet apertures (13) through which the gas-enriched liquid can flow. A piston (14) is arranged movable within the outlet means (12) between a closed position where it blocks all flow of gas-enriched water through the outlet apertures (13), an intermediate position where the piston (14) opens up for larger flow area (13) for flow of gas-enriched liquid, and an open position where the gas-enriched liquid can flow out through all flow area in the outlet apertures (13).

Description

Device for mixing of gaseous liquid in liquid

The present invention is related to an injector for mixing of gaseous liquid in liquid, in accordance with the preamble of patent claim 1.

Background Proper water quality is one of the most important criteria for well-being, optimum growth and quality of fish in land-based fish farming industry. The water must exhibit correct temperature, oxygen content, pH and salinity, and this is being monitored thoroughly. The oxygen saturation in water from the outlet from the fish vessels/containers is monitored continuously, and the oxygen supply is controlled to obtain optimal oxygen content. The fish rearing vessels are supplied with a flow of fresh water, in the following also denoted as "crude water", to maintain the water quality.

To dissolve more oxygen gas in fish rearing vessels in fish farming units, it is known to bleed a partial flow of the water, such as 20% of the total water intended for a compartment of fish rearing vessels. If the partial flow is set under a pressure of 4 bars in a container (often in combination with an ejector), typically 10 times as much oxygen gas is being dissolved in the oxygen-enriched water as in natural water. At 4 bars, water can in theory keep 20 times more oxygen gas than water in equilibrium with oxygen at atmospheric pressure, but then the efficiency of the process equipment is 100%. SMormally, a realistic efficiency is 50% or slightly higher.

Accordingly, in fish farms every fish rearing container exhibit 2 water sources: one source of "non- oxygenated" crude water and a source of "highly oxygenated" crude water. The term "non- oxygenated" water is meant to inciude water where the partial pressure of the oxygen in the water is substantially equal to the partial pressure of oxygen in the surrounding atmosphere, or in other words water being in equilibrium with air. The term "highly oxygenated" or "oxygen- enriched" water is meant to include water being pressurized to provide a supersaturated concentration of oxygen dissolved in water compared to water at equilibrium with air. The highly oxygenated crude water is intermixed with the non-oxygenated water immediately before the water is supplied into the container. The amount of oxygen being intermixed with the crude water is controlled by controlling the mixing ratio between incoming crude water and oxygen-enriched crude water. In accordance with the prior art, the mixing ratio is controlled by adjusting a membrane valve, preferably a pneumatic membrane valve. However, the pressure of the highly oxygenated water is decreased to about 2.5 bars to provide a static pressure a little higher than what is required to prevent oxygen gas from being released from the water. This water at 2.5 bars is ejected to a ring main. Frequency controlled water pumps controlled with regard to pressure keep the water pressure substantially constant.

The problem with this prior art system is the risk of degassing of oxygen gas downstream of the membrane valve because of reduced water pressure between valve and mixing point. Degassing results in free gas within the pipes, and this can clog the water flow as a whole to one or more fish rearing containers. If the water containing free gas is injected into the fish rearing container, the gas can result in flocculation, and change the flow regime of the water in the fish rearing vessel. Moreover, free gas cannot be absorbed through the gills of the fish and is therefore classified as lost with a deteriorated economy as a result. The prior art method of mixing oxygenated water with crude water, results in a high risk of degassing of already dissolved oxygen. In addition, nitrogen gas in the water may be redirected with an increased risk of "decompression sickness". Moreover, this prior art solution is vulnerable in that the equipment can be destroyed at low outdoor temperatures, since pressurized water dried with a adsorption drier is required. Moreover, the equipment is expensive to buy.

US Patent No. 5,277,250 discloses an injector for supplying a treatment chemical into a fluid flowing within a pipe and to perform distribution of the chemical in the fluid flow. The chemical is injected through an elongate perforated pipe "quill" to obtain an improved intermixing of the chemical in the fluid flow.

Another example of liquid injection through a perforated pipe into flowing liquid can be found in GB 2 164 021 A.

Object

An object of the present invention is to provide a device for intermixing gas-enriched liquid in liquid, particularly oxygen-enriched water in crude water, whereby the device is to provide optimal mixing in a short period of time and avoid problems with degassing prior to intermixing. Moreover, another object is to provide a simple and quick control of the gas quantity being mixed in and that the device should be reliable independent of weather conditions. Finally, an object is that the device shall be inexpensive at purchase or operation.

The invention

The object is obtained by an injector in accordance with the characterizing part of patent claim 1. Further beneficial features appear from the dependent claims. The invention is applicable to intermixing of gas-enriched liquid in another bulk phase of liquid. However, in the following, the invention is described for mixing of water supplied with additional oxygen, hereinafter denoted as oxygenated water or oxygen-enriched water, in crude water, without being interpreted as limiting to the scope of the invention as defined in the claims. However, the invention is not limited to intermixing of oxygenated (supersaturated with oxygen) water in a flow of crude water (water saturated with oxygen or water in equilibrium with oxygen in the surrounding atmosphere), but can equally be applied for intermixing of other liquid types supersaturated with one or more gases in a bulk phase of a liquid having a normal saturation of the gas in question. The invention is related to a device for intermixing gas-enriched liquid in flowing liquid, also denoted as "injector". The injector comprises an outlet means for the gas-enriched liquid arranged to be fixed into a pipe of the flowing liquid. The term "pipe" is here meant to include any type of flow conduit for liquid. The outlet means is provided with one or more outlet ports through which the gas-enriched liquid can flow. Moreover, the injector is provided with an inlet for the gas- enriched liquid for supply of gas-enriched liquid at gauge pressure into the injector. The inlet is at its end connected to a source of the gas-enriched liquid (not described further here). In accordance with the invention, a piston is arranged within the outlet means to form a tight connection with the internal periphery of the outlet means. The piston is arranged movable between a closed position where it blocks all flow of gas-enriched liquid through the outlet ports, an intermediate position where the piston opens for a larger flow area for flow of gas-enriched liquid, and an open position where the gas-enriched liquid can flow out through all available flow area in the outlet ports. It is important to note that the primary function of the piston is to control available flow area at a given point in time and accordingly flow volume. The piston is not utilized as any displacement means to pump gas-enriched liquid into the bulk phase. The injector in accordance with the invention possess several advantages obtained in relation to the prior art. The oxygen supersaturated water keep the gas in a best possible manner (minimum degassing) since the static pressure of the water is maintained all the way to the point of intermixing. The pressure drop across the flow area occurs in the point of intermixing and we avoid pockets, pipe sections or other water-filled parts having a lower pressure, which would be the situation if a valve was used outside the main pipe.

The injector is formed of any appropriate material suitable of guiding the liquid intended to flow through the same, which will be within the scope of a person skilled in the art. The injector is attached in a gas and liquid tight manner to the main pipe in any suitable manner, such as using a flange, gasket and nut. However, this will be within the scope of a person skilled in the art and is not described in further detail here.

The injector is preferably located so that the outlet means for oxygen-enriched crude water extends perpendicular into the main pipe of the flowing bulk phase with crude water, whereas other angles may also be contemplated. The outlet means is to extend a certain distance into the main pipe, preferably beyond the center of the main pipe but not that far that it contacts the pipe at the opposite side. As mentioned above, the outlet means is provided with one or more apertures in the periphery, whereby the apertures can be distributed along the periphery and/or in the elongate extension of the outlet means. The apertures form the outlet means of the oxygen- enriched water and lead into the internal of the main pipe when the injector is mounted to the main pipe.

In a preferred embodiment the outlet means is formed as a pipe fitting extending from the device and into the main pipe and radially into the flow of crude water. The term "pipe fitting" is in this context meant to be a short pipe, whereby the pipe may exhibit an arbitrary geometry. Mutual dimensions are selected according to demand with regard to dimensioning of surrounding apparatuses and plant, and will be within the range of a person skilled in the art.

Preferably, the piston is formed of POM (polyoxymethylene) or similar material, having a diameter equal to the internal diameter of the outlet means. The piston rod extends from the piston and through the injector and is at the opposite end connected to an actuator able to move the piston rod and then the piston, preferably stepless, between a closed (inner or internal) position, an arbitrary intermediate position where a part of the available flow area of the outlet apertures is exposed to guide oxygen-enriched water into the bulk phase of flowing crude water in the main pipe, and a completely open (outer or external) position where all available flow area of the outlet apertures is exposed for a through flow. The piston is in the "outer" position arranged to the end of the outlet means, whereas the piston in the "inner" position is retracted beyond the outlet apertures and in this manner blocking all through flow of oxygen-enriched crude water.

The flow characteristic of the outlet means depends on the size and geometry of the apertures, and may be changed/controlled by amending size and geometry of the apertures. For example, symmetrical slits will provide a different flow characteristic than triangular or circular apertures. In an alternative embodiment, the outlet means is replaceable so that the outlet means can be changed for another one having different apertures, as desired. In a preferred embodiment of the present invention, the device is arranged in a manner that the piston rod extends in a straight line from the piston in the outlet device and through the injector. The piston rod is connected to an actuator which pushes the piston rod to move the piston between an open (outer) and closed (inner) position, and in a manner that controls the amount of oxygenated water being mixed into the crude water.

In a particularly preferred embodiment of the injector, the inlet for oxygenated water is arranged at an angle with the outlet means, preferably 90 degrees or more, and in an embodiment like this the piston rod can extend in a straight line from the piston and out of the device. Then the connection between the piston rod and the actuator pushing the piston rod therefore can be arranged external to the device itself.

In a particularly preferred embodiment of the present invention like this, the actuator can be attached on top of the device and being connected to the piston rod with a bracket. In this way, a compact unit with little space requirement is obtained. The piston rod will extend out of the device and moves linearly forwards and backwards by the actuator. To prevent the rod from being bent transversely, a preferred embodiment of the invention is provided with a guide, whereby the bracket connecting the piston rod and actuator are extending along the same.

Example

In the following, the invention is described with reference to attached drawings, where

Fig. la illustrates a preferred embodiment of the injector in accordance with the present invention in a side view, attached to a pipe which is leading crude water,

Fig. lb is a drawing similar to Fig. la, but having a radial section through the main pipe and with the injector viewed from above,

Fig. 2 illustrates the injector of Fig. 1 in a partial section,

Fig. 3 shows a piston and a piston rod, and Fig. 4a-4c show different embodiments of the outlet means of the device.

The injector illustrated in Fig. la, lb and 2 comprises an inlet 10 and an outlet means 12 extending into a pipe, hereinafter denoted as main pipe 11, which is guiding crude water to a land-based fish farm, a group of fish rearing containers or one single fish rearing container. The injector is arranged to inject oxygen-enriched water at gauge pressure into the main pipe, i.e., the oxygen- enriched water is at a pressure higher than the pressure in the water flowing in the main pipe. The outlet means 12 is formed as a pipe fitting having an outer end located within the main pipe 11 guiding crude water, and an inner end in a flow connection with the injector. The outlet means 12 located within the main pipe 11 is provided with numerous outlet apertures 13. Oxygen-enriched water is introduced into the inlet 10 to the device and out of the outlet apertures 13 i the outlet means. The outlet apertures 13 may have different geometries, as shown in Fig. 4a-4c. In the embodiment shown in Fig. la and 2 the outlet apertures are formed as in Fig. 4a, and the slits 13 are arranged so that the oxygen-enriched water will flow radially into the flow of crude water in the pipe (the flow direction of the bulk phase is indicated by the arrows B in Fig. la), to obtain an optimal mixing of oxygen-enriched water and crude water. Fig. lb shows an example of a preferred embodiment where a pipe-shaped outlet means 12 is fixedly connected to the main pipe 11 and extends radially into the latter. A slit shaped outlet aperture 13 is formed in each surface of the outlet means 12, here two slit shaped outlet apertures 13 allowing the water to flow out through the outlet means and into the bulk phase of the flowing water in a direction substantially perpendicular to the flow direction of the bulk phase (flow direction of the oxygen-enriched crude water is indicated by the arrows P in Fig. lb). This provides a particular good mixing of oxygen- enriched water.

A piston 14 is arranged inside the pipe fitting 12 and being connected to a piston rod 15, as shown in Fig. 2 and 3. The piston 14 is arranged to form a seal to the internal of the outer end of the pipe section 12, whereas all available flow area is available for guiding oxygen-enriched water into the flowing bulk phase of water. The flow of the oxygen-enriched water from the outlet means 12 through the outlet apertures 13 is indicated by the arrows P. In the illustrated embodiment, the piston 14 is formed of POM and exhibits a diameter corresponding to the internal diameter of the pipe fitting. In the preferred embodiment of Fig. 3, the piston 14 is connected to the piston rod 15 in that the piston has a through bore which accommodates the piston rod. The through bore can be threaded and correspond to threads 22 on the outer end of the piston rod. In the embodiment illustrated in Fig. 3, the piston rod 15 is connected to the piston 14 in that the piston rod exhibits a constriction or narrowing 23 in outer end, so that the piston 14 abuts the step of the constriction 23, and moreover in that a nut 24 is attached to the other side of the piston 14. At the opposite end, the piston rod 15 is connected to an actuator 16, whereby the actuator 16 moves the piston rod 15 linearly and thus moves the piston between an "inner" and "outer" position, from an end position to an opposite end position, respectively. In the illustrated Embodiment, the outlet means is arranged perpendicular to the inlet, and the piston rod 15 extend linearly from the piston 14 and out through an opening 17 in the device, at the angle between the inlet and outlet. The opening 17 is formed in a manner that the piston rod 15 can move linearly through the same, whereas liquid or gas cannot seep out through the same. This can be solved in numerous ways, which will be within the scope of a person skilled in the art. In this embodiment, the actuator 16 is located outside the device, and is preferably arranged atop the device so that the piston in the actuator 16 moves in parallel with the piston rod 15, and is connected to the same with a bracket 18.

To prevent the piston rod from being bent transversely and to decrease wear of gaskets etc., the device is provided with a guide 19 extending from the device and at a distance corresponding to the distance between inner and outer position of the piston 14. In the embodiment shown, the guide is formed with sides and bottom, whereby the bracket 18 can abut the sides and bottom of the guide 19. In a particularly preferred embodiment, the piston rod 15 is extended so that the end of the rod extends through the distal end 20 of the guide both when the piston 14 is in its inner and outer positions. The actuator 16 can be of any actuator type, e.g., hydraulic, pneumatic, or electric, which will be within reach of one skilled in the art.

When oxygen is to be supplied to the water, the actuator 16 is activated, whereupon the piston 14 is guided to the outer end of the pipe fitting 12, and oxygen-enriched water flows through the device and out through the apertures 13 in the pipe fitting. The travel distance of the piston 14 towards the end of the pipe fitting depends on the amount of oxygen to be supplied to the water, since the piston with increasing movement towards the end opens up for more and/or larger apertures 13. When the oxygen amount is to be decreased, or if no more oxygen is to be supplied to the water, the actuator 16 is reactivated, whereupon the piston 14 is moved towards the device so that the apertures 13 are being closed totally or partially. In the illustrated embodiment, the device is provided with a threaded sleeve 21 to enable attachment into a drain, a manometer/pressure transmitter, frost pin or similar (not shown). In this way, the pressure can be monitored to avoid degassing. The pressure in the device is monitored and compared to the oxygen saturation in the water after mixing with the oxygen- enriched water, to obtain optimal conditions. The amount of oxygen-enriched water to be supplied varies from one fish rearing vessel to another because of different number of fish, stress, fish size, flow rate, varying amount of fish feed, and similar. Therefore, the oxygen is metered automatically in all the fish rearing vessels, and highly oxygenated water is supplied in an amount as needed by controlling the piston position automatically via a controller. The control technique is not described in further detail here, since this knowledge is considered to be within the scope of a person skilled in the art.

The invention is described above with reference to a preferred embodiment illustrated in the attached drawings, and for use with fish farms ashore. This is only done to illustrate the invention and shall by no means be interpreted as limiting the invention as defined in the attached claims.

Claims

1. An injector for intermixing gas-enriched liquid in flowing liquid, whereby the device comprises an inlet (10) for gas-enriched liquid, from an external source, to the injector, and an outlet means (12) for the gas-enriched liquid arranged to be mounted into a flow conduit (pipe) (11) with the flowing liquid, whereby the outlet means (12) is provided with one or more outlet apertures (13) through which the gas-enriched liquid can flow out into the bulk phase of the flowing liquid, characterized in that a piston (14) is arranged within the outlet means (12) to establish a tight connection with the internal periphery of the outlet means (12), whereby the piston (14) is arranged movable between a closed position, where it blocks all flow of gas-enriched liquid through the outlet apertures (13), an intermediate position where the piston (14) opens up for a larger flow area (13) for flow of gas-enriched liquid, and an open position where the gas-enriched liquid can flow out through all available flow area in the outlet apertures (13).

2. The injector of claim 1, characterized in that the gas is oxygen or an oxygen-containing gas and that the liquid is water.

3. The injector of claim 1, characterized in that the piston (14) is connected to an actuator (16) via a piston rod (15), so that the actuator (16) can move the piston (14) in relation to the outlet means (12).

4. The injector of claim 3, characterized in that the actuator (16) is arranged outside the injector.

5. The injector of claim 4, characterized in that the actuator (16) is connected to the piston rod (15) via a bracket (18).

6. The injector of claim 1, characterized in that the inlet (10) and outlet means (12) for gas- enriched liquid is arranged in a mutual angle of at least 90 degrees.

7. The injector of claim 6, characterized in that a piston rod (15) which is connected to the piston (14), extend linearly from the piston (14) and out of the injector beyond the liquid inlet (10) and the outlet means (12).

8. The injector of claim 7, characterized in that the outlet means (12) exhibits two slit shaped outlet apertures (13) arranged mutually opposite, so that the liquid flow radially (P) out into the pipe (11) and perpendicular to the flow direction (B) of the bulk phase of the flowing liquid.