High-flow, high-pressure inline saturator system and method thereof

There is provided an inline saturator system and method for gas exchange with an aqueous-phase liquid. The system includes a pressure vessel, configured to receive a first liquid and a first gas from external sources and to discharge a second liquid and a second gas from the pressure vessel, and a gas infusion device situated within the pressure vessel. The gas infusion device is configured to receive the first liquid and first gas, to facilitate gas exchange therebetween, producing the second liquid and the second gas, and to discharge the second liquid and second gas into the pressure vessel. The system further includes a recirculation system configured to direct a portion of liquid within the pressure vessel back into the saturator device, where injection of the redirected liquid into the gas infusion device forces the first liquid into the gas infusion device for the gas exchange.

TECHNICAL FIELD

The invention relates generally to systems and a method that dissolve gas into a liquid and, more particularly, to inline saturator systems for use in aquaculture.

BACKGROUND

Whether dealing with fish, shell fish, or crustaceans in the aquaculture and wild fisheries industry, it is critical to be able to control the dissolved gas environment in the associated water. In general, there are two issues that must be controlled: maintaining sufficient dissolved oxygen for respiration, and removing the dissolved carbon dioxide resulting from respiration.

It is generally understood that higher levels of dissolved oxygen in the water have a positive influence on the health and growth rate of fish. Within the aquaculture industry, the usual approach to maintaining dissolved oxygen levels involves the injection of oxygen gas through one or more high-pressure venturi nozzles.

While this approach is viable, it also increases the total gas pressure, which in turn, tends to cause the oxygen to bubble out of the water. It is also known that the overall dissolved gas pressure can play a significant role in fish health and growth rate, etc. As such, a further issue concerns the fact that prolonged exposure to an elevated total gas pressure can be a health hazard to the biomass in the water.

SUMMARY

This disclosure provides an inline saturator system for gas exchange with an aqueous-phase liquid, the system comprising:

a pressure vessel configured to receive a first liquid and a first gas from external sources, and to discharge a second liquid and a second gas from the pressure vessel;

a gas infusion device situated within the pressure vessel, the gas infusion device configured to receive the first liquid and first gas, to facilitate gas exchange between the first liquid and first gas, producing the second liquid and the second gas, and to discharge the second liquid and second gas into the pressure vessel; and

a recirculation system configured to redirect a portion of liquid within the pressure vessel back into the saturator device;

wherein injection of the redirected liquid into the gas infusion device forces the first liquid into the gas infusion device for the gas exchange.

This disclosure also provides a method for gas exchange with an aqueous-phase liquid, the method comprising:

injecting a first liquid and a first gas into a pressure vessel;

directing the first liquid and the first gas through a gas infusion device situated within the pressure vessel, the gas infusion device configured to facilitate gas exchange between the first liquid and the first gas, producing a second liquid and a second gas;

redirecting a portion of the second liquid back into the saturator device; and

discharging the remaining second liquid out of the pressure vessel;

wherein the redirection of the second liquid into the gas infusion device draws the first liquid into the gas infusion device for the gas exchange.

Advantages and features of the invention will become evident upon a review of the following detailed description and the appended drawings, the latter being briefly described hereinafter.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS SHOWN IN THE DRAWINGS

An example embodiment of a saturator system10, a double array saturator system100, and methods of their use will be discussed. Saturator system10will first be described.

As shown inFIGS.1-6, saturator system10generally includes a pressure vessel12, two saturation devices14, a recirculation system16, and a control system.

Pressure vessel12in this example embodiment is generally cylindrical in shape, having a 2.15 meter length with a diameter of 0.61 meters. Pressure vessel12comprises an input port18situated in the middle of pressure vessel12for receiving a first liquid from an external source and an output port20for discharging a second liquid that is different from the first liquid, from pressure vessel12. Output port20is positioned below input port18, external to pressure vessel12. Overall, saturator system10has a height of about 1.023 meters.

Input port18is covered by a shut-off valve (not shown) and downstream from input port18is positioned a flow rate sensor22for monitoring the flow of the first liquid into pressure vessel12. Output port20is also covered by a back-pressure control valve24positioned upstream of output port20for maintaining fluid pressure within pressure vessel12. Both input port18and output port20each have a diameter of about 0.203 meters.

Pressure vessel12includes a gas inlet26for receiving a first gas, and a gas outlet28for discharging a second gas, that is different from the first gas, from pressure vessel12. Gas inlet26is further in fluid communication with gas manifolds27situated within pressure vessel12. Gas manifolds27are situated adjacent to and are in fluid communication with saturator devices14. Saturator device14is also referred herein to as a gas infusion device.

Gas outlet28in the depicted embodiment includes an air eliminator30and a pressure relief valve32, both in fluid communication with pressure vessel12. Both are adapted to transfer gas from within pressure vessel12to the atmosphere.

Pressure vessel12is made of a steel alloy, particularly 316 stainless steel, to enable it operate in a salt-water environment. Further, pressure vessel12is an ASME-certified pressure vessel, rated for an operating pressure of 100 psi.

Pressure vessel12has two pressure-rated doors34with seals. Doors34cover openings on opposed sides of pressure12, through which a user may access the internal space within pressure vessel12for cleaning and maintaining of components inside pressure vessel12.

A mechanical means, or a baffle36, is further situated within pressure vessel12. Baffle36is adapted to mechanically direct the first liquid from input port18to saturator devices14.

Saturator devices14are situated within pressure vessel12and are positioned on either side of input port18, orientated generally parallel with one another. Each gas infusion device14has a first end portion38, for receiving the first liquid and discharging the second gas, and an opposed second end portion40for receiving the first gas and discharging the second liquid into pressure vessel12. Each gas infusion device14further has a fibre module array42situated between the end portions where fibre module array42is made up of a polymer coated microporous fiber material. In the present embodiment, saturator devices14are the saturator or gas infusion device disclosed in U.S. Pat. No. 7,537,200, to Glassford, Oct. 31, 2003.

Recirculation system16includes a suction nozzle44and two discharge nozzles46, which are all in fluid communication with pressure vessel12.

Suction nozzle44is positioned proximate second end portion40of gas infusion device14to draw a portion of liquid into recirculation system16. One discharge nozzle46is positioned adjacent each first end portion38of each gas infusion device14to inject the portion of liquid back into gas infusion device14.

Recirculation system16includes a pump48(seeFIGS.6-8) operatively coupled between suction nozzle44and discharge nozzles46, pump48being adapted to drive fluid from suction nozzle44to discharge nozzles46.

Recirculation system16further includes two eductors50, one eductor50operatively coupled between each discharge nozzle46and its corresponding gas infusion device14.

Eductors50are made of metal, and in the present embodiment, made of 316 stainless steel. In this manner, eductors50are adapted to operate in a high-pressure, salt-water environment.

The control system (not shown) is operatively coupled to the flow rate sensor22and back-pressure control valve24. The control system further includes a pressure sensor52situated within pressure vessel12, which is adapted to measure the fluid pressure within pressure vessel12, and a regulator (not shown) on gas inlet26.

Saturator system10, has mounts54fixed to, and extending from, pressure vessel12. Mounts54are mechanical means which allow saturator system10to be secured to the ground, a vertical wall and/or to another saturator system10as described below.

Whereas a specific embodiment of saturator system10is herein shown and described, variations are possible. In some examples, pressure vessel12contains two or more gas inlets26, two or more air eliminators30, and/or two or more suction nozzles44.

In other examples, rather than a two saturator devices14, pressure vessel12may instead house one or more than two saturator devices14.

As well, instead of the saturator devices being positioned side-by-side and orientated parallel with one another in an upright position (i.e. linear horizontally) within pressure vessel12, in other examples, the multiple saturator devices14are oriented in one of the following ways: linear vertical, planar horizontal, planar vertical, or arbitrarily.

In other examples, rather than using a single pump, saturator system10includes two or more pumps as part of its recirculation system16.

Double Array Saturator System

As shown inFIGS.6-8, double array saturator system100generally includes two saturator systems10with a shared recirculation system16and a common pump48. Mounts54allow one pressure vessel12to be secured on top of or above the other pressure vessel12.

In the shown embodiment, each pressure vessel12houses two saturator devices14therein. Each pressure vessel12also has its own corresponding suction nozzle44and two discharge nozzles46, which are all in direct fluid communication with pump48.

Whereas a specific embodiment of double array saturator system100is herein shown and described, variations are possible.

In some examples, each pressure vessel12and saturator devices14may be varied as noted above.

In others examples, instead of pressure vessels12being positioned one on top of the other in parallel (i.e. linear vertically), in other examples, the multiple pressure vessels12are oriented in one of the following ways: linear horizontal, planar horizontal, planar vertical, or arbitrarily.

Double array saturator system100may instead have two recirculation systems16(with a pump48each), one operatively coupled to each pressure vessel12.

Independent Use

Both saturator system10and double array saturator system100are for use in conducting a gas exchange with an aqueous-phase liquid inline with a tank of water. While the tank is not shown, both saturator system10and double array saturator system100are understood to be coupled to the tank with piping extending from their input ports18and output ports20. Movement of liquid through the use of systems10and100are indicated by dashed arrows in the Figures. While not shown in the drawings, the saturator systems may also be used in a contained, open body of water.

The first liquid is injected into pressure vessel12through input port18, and directed towards first end portion38of saturator devices14by baffle36. The first gas is also injected into vessel12through gas inlet26and directed to gas manifolds27, which are adjacent second end portion40of each gas infusion device14.

Simultaneously, a portion of fluid that is proximate second end portion40of gas infusion device14is drawn by pump48through suction nozzle44. The portion of fluid is redirected and pumped through discharge nozzles46and through eductors50, which are positioned adjacent first end portion38of saturator devices14. The force of the redirected fluid as it travels through eductor50draws and drives the first liquid into first end portion38of gas infusion device14.

In gas infusion device14, the first liquid and the first gas interact with the fibre module array, which facilitate a gas exchange between the first liquid and first gas as both fluids travels through gas infusion device14. This exchange produces the second liquid and the second gas, which are both discharged from second end portion40of gas infusion device14into the pressure vessel.

While most of the second liquid will be then discharged from pressure vessel12through output port20, some of the second liquid will be drawn by pump48through suction nozzle44into recirculation system16. This liquid is then redirected to first end portion38of gas infusion device14through discharge nozzle46. This redirected second liquid will then be pumped through eductor50and used to draw the first liquid into gas infusion device14for the gas exchange.

As noted above, both saturator system10and double array saturator system100are adapted for operation under pressure. In that regard, the control system uses information from flow rate sensor22and pressure sensor52to maintain the pressure within pressure vessel12at a predetermined level. The control system drives back pressure control valve24and pump48in order to maintain sufficient head to drive fluid through gas infusion device14and to maintain fluid pressure under low-flow conditions. In the present embodiment, the control system drives pump48so as to ensure that the pressure in gas infusion device14is at least 20 psi.

The control system also uses information from flow rate sensor22to determine the amount of the first gas required by each gas infusion device14. The control system controls the regulators connected to gas inlets26on pressure vessel12. The control system may be configured to detect the vibration of pump48in order to monitor the pump's mechanical health.

In order to maintain a generally stable total gas pressure, the second gas is released through air eliminator30to the atmosphere. For safety, pressure relief valve32may also be used to further release gases from pressure vessel12into the atmosphere.

Whereas a specific embodiment of the method is herein shown and described, variations are possible.

In other examples, the control system drives pump48may be adapted to ensure that the pressure in saturator system10is up to 65 psi.

Combined Use

Both saturator system10and double array saturator system100may be used simultaneously with one or more lift pumps situated within the body of water.

The lift pumps are configured to remove carbon dioxide gas from the water. An example of such a lift pump is disclosed in U.S. 62/607,385. Each lift pump includes a gas input and perforations to enable water to enter the lift pump.

The perforations are situated on a plate for gas to pass through, where the plate positioned upstream from a mixing chamber, through which water enters the lift pump and where the gas forms bubbles which improve gas lift. The perforated plate is made by additive manufacturing with precise hole dimensions and hole spacing.

As the gas is bubbled into the water through the plate, it reduces the water density so that the water rises through the lift pump, thus enabling more water to enter through the perforations. As the water rises, dissolved CO2in the water is exchanged with the injected air based on Henry's Law, such that the partial pressure of dissolved CO2in the water will work to match the partial pressure of CO2in the air.

Used together in this manner, the saturator system oxygenates the body of water, while the one or more lift pumps remove the dissolved CO2and remediates the ammonia to form nitrate.

Such a system may further include one or more oxygen tanks connected to the saturator system for supplying oxygen to the saturator system, and a compressor coupled to lift pumps to supply ambient air to generate the lift.

Such a system may also have a gas regulator operatively coupled between the oxygen tanks and the saturator system to regulate the flow of gas into the saturator system, a dissolved oxygen sensor positioned within the body of water, a saturator feed pump in fluid communication with the body of water, adapted to draw and direct water from the body of water into the saturator system, and an ammonia sensor positioned within the body of water.

A control and monitoring system may be in place to communicate with, control and coordinate each of the above components. For example, the compressor can be activated to engage the lift pumps in response to the detected concentration of ammonia rising above a maximum level. The compressor may then be disengaged to deactivate the lift pumps in response to the detected concentration of ammonia falling below a minimum level. In a similar manner, the gas regulator and the saturator feed pump may be activated and controlled in response to the detected concentration of oxygen falling below a minimum level. The gas regulator and the saturator feed pump may also be deactivated accordingly.

Whereas a specific embodiment of the method is herein shown and described, variations are possible.

Testing

The following tests were conducted. The first gas used was oxygen and the first liquid was oxygen-poor and carbon dioxide-rich saltwater or oxygen-poor and carbon dioxide-rich freshwater.

Requirements

The tests were set up by connecting the suction and discharge pipes, respectively, to the inlet port and the outlet port of the saturator system, the other ends of the pipes were placed in the tank of water, on opposite sides of the tank to ensure good circulation of oxygenated water. The pressure control valve is positioned between the saturator system and the discharge pipe to the tank.

Background measurements of the water tank were taken, noting salinity, temperature, total gas pressure and oxygen readings.

A small amount of oxygen is fed to the unit to keep the fibers of the saturator devices clear of water.

The variable speed pumps are then turned on to allow water from the tank to flow into and fill the pressure vessel and the pipes.

The pressure control valve is partially closed to increase the pressure within the pressure vessel to the desired level.

By adjusting the water flow and pressure within the pressure vessel, the desired predetermined parameters are eventually achieved. The parameters for the trials are set out in Table 1 below.

The recirculation pump is then turned on and increased until there is at least 30 PSI differential between the recirculation pump pressure and the unit pressure.

The oxygen is turned on at the desired level.

The saturator system was then run for the predetermined desired time.

The saturator system is then shutdown in reverse order, i.e. first the oxygen is turned off, then the recirculation pump, and then pressure.

Readings are taken for oxygen, temperature, and total gas pressure and compared to the previous values. Previous values are those of water at sea level, that being 100% oxygen saturation, 15 Degrees C., at 760 mmHg (100% total gas pressure). If the tank did not mix properly, several locations will have to be measured to get a full profile on the tank.

Based on these comparisons, it was determined how much oxygen was added to the water and how much other gas was removed.

A number of tests were run according to the following rationale, and the results illustrated in the noted Figures.

FIG.9is a sample graph explaining the elements of the graphs in the subsequent Figures.A: Point at which the pump was turned onB: Trial name indicating salinity, pressure in pounds per square inch, water flow in liters per minute and Oxygen flow in liters per minute (corrected for pressure)C: Calculated grams of oxygen infused per minuteD: The theoretical value that should be obtained based on our internal modelsE: Actual Oxygen percent saturation readingsF: Time during which Oxygen was added

FIGS.10-28show percent saturation data using the saturator system ofFIG.6.Trial 1: This test was preformed as a first attempt to replicate the most basic function of the unit in fresh water (FW) to see if it compared favorably to the models. SeeFIG.10.Trial 2: This test was preformed as an attempt to replicate the most basic function of the unit in fresh water at an known operating pressure for smaller units. SeeFIG.11.Trial 3a: This test was preformed to see if there was an issue with the right array. SeeFIG.12.Trial 3b: This test was preformed to see if there was an issue with the left array. SeeFIG.13.Trial 4: This test was preformed at an increased differential pressure in the arrays and an account taken for the volume of piping in the experiment. SeeFIG.14.Salt water (SW) trial 1: This test was preformed as a first attempt to replicate the most basic function of the unit in salt water at an increased differential to see if it compared favorably to the models. SeeFIG.15.SW trials 2, 3, 5, 7, 8, 9, 10, and 11: These trials were performed to push the limits of the device and see how accurate our current modeling system reflected reality in salt water. SeeFIGS.16-23.FW trials 1-5: These trials were performed to push the limits of the device and see how accurate our current modeling system reflected reality in fresh water. SeeFIGS.24-28.

The outcome for the salt water and fresh water trials (corresponding toFIGS.15-27) are also summarized in Table 1 below.

The tests show that levels of oxygen could be infused at levels not previously possible with conventional equipment while keeping the total gas pressure (TGP) relatively unchanged. For example, in Saltwater trial 11, the saturator system was operated at 65 internal psi, with water flow at 8000 L/min and oxygen flow at 245 L/min. While dissolved oxygen levels reached 447 percent saturation, the overall total gas pressure change was only 6.5 percent.

In comparison, existing saturator devices can only dissolve oxygen in water to reach 300 percent saturation, while the overall total gas pressure change is usually 140 percent, which is lethal to aquatic life.

As such, an advantage of the use of the present saturator system10and/or double array saturator system100is that the oxygen could be infused into the water at nearly ten times the amount of oxygen that would be infused by using the prior art saturator device while the total gas pressure in the liquid remains relatively unchanged.

Another advantage of the present saturator system is that it enables gas to be infused into an aqueous liquid under pressure with a high flow rate without increasing or significantly increasing the total gas pressure in the liquid.

The invention should be understood to be limited only by the accompanying claims, purposively construed.