The present disclosure relates to desalination. More particularly, the present disclosure relates to a centrifugal system and method to aid in desalination of water.
Because human life depends upon fresh water, there is a constant need to find new sources or to uncover ways of producing fresh water. Due to the amount of saltwater on the planet, there is an obvious need to convert the salt water to fresh water. As a result, several desalination methods exist in the art, including ultrasonic methods, electrolysis, and other specialized pumping. However, these methods of desalination are very expensive, which prohibits them from being widely utilized. As a result, water shortages and droughts continue to exist for societies, even when those societies are next to oceans—our largest bodies of water. For example, California constantly faces water shortages and droughts despite being on the coast.
Much of the cost of desalination results from the energy consumption required to produce it. Most current methods of desalination rely on pressure. Currently, massive pumps are used to produce the pressure needed for desalination. As a result, these pumps consume a massive amount of energy, making them cost-prohibitive for many uses. Further, a majority of the energy placed into the system is lost in the saline concentrate produced as part of the filtration process. Accordingly, if a system and method could reduce the energy required to desalinate, the cost would decrease, thereby allowing wider use of desalinating technology and societies being less susceptible to droughts during dry seasons.
Therefore, there remains a need for a system and method that can desalinate water at significantly reduced cost and that can prevent loss of energy in the system. The present reverse osmosis centrifuge disclosed herein solves these and other problems.
In one embodiment, a reverse osmosis centrifuge comprises a support shaft, a plurality of receiving tubes, a plurality of housings with filters therein, a plurality of departure tubes, and a permeate trough. The plurality of receiving tubes are coupled to a top of the plurality of housings, while the plurality of departure tubes are coupled to a bottom of the plurality of housings. As seawater enters the receiving tubes, it flows to the plurality of housings, where centrifugal force creates the permeate (i.e., fresh water) and concentrate (i.e., salt water) in the plurality of housings. The permeate exits the plurality of housings and is deposited into the trough. The concentrate travels through, and exits from, the plurality of departure tubes.
In one embodiment, a reverse osmosis centrifuge comprises a rotatable housing having a water inlet and a plurality of water outlet arms, the rotatable housing being motor controlled. Each water outlet arm extends radially from the rotatable housing, the distal end of each arm comprising a saltwater outlet and a freshwater outlet. The reverse osmosis centrifuge further comprises a trough for receiving the output from the saltwater outlet and freshwater outlet, the trough divided so as to ensure separation of the fresh water from the saltwater. In one embodiment, the housing is an oblate spheroid. As a result, the water therein easily flows to the plurality of water outlets and through each arm. Pressure builds at the end of each arm due to rotational forces and the length of the arms. Accordingly, the rotationally-induced pressure (which may be referred to as “centrifugal” force) provides for desalination at a lower energy cost.
The following descriptions depict only example embodiments and are not to be considered limiting in scope. Any reference herein to “the invention” is not intended to restrict or limit the invention to exact features or steps of any one or more of the exemplary embodiments disclosed in the present specification. References to “one embodiment,” “an embodiment,” “various embodiments,” and the like, may indicate that the embodiment(s) so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in one embodiment,” or “in an embodiment,” do not necessarily refer to the same embodiment, although they may.
Reference to the drawings is done throughout the disclosure using various numbers. The numbers used are for the convenience of the drafter only and the absence of numbers in an apparent sequence should not be considered limiting and does not imply that additional parts of that particular embodiment exist. Numbering patterns from one embodiment to the other need not imply that each embodiment has similar parts, although it may.
Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad, ordinary, and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described. As used herein, the article “a” is intended to include one or more items. When used herein to join a list of items, the term “or” denotes at least one of the items, but does not exclude a plurality of items of the list. For exemplary methods or processes, the sequence and/or arrangement of steps described herein are illustrative and not restrictive.
It should be understood that the steps of any such processes or methods are not limited to being carried out in any particular sequence, arrangement, or with any particular graphics or interface. Indeed, the steps of the disclosed processes or methods generally may be carried out in various sequences and arrangements while still falling within the scope of the present invention.
The term “coupled” may mean that two or more elements are in direct physical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other.
The terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments, are synonymous, and are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including, but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes, but is not limited to,” etc.).
As previously discussed, there remains a need for a system and method that can desalinate water at significantly reduced cost and that can prevent loss of energy in the system. As will be appreciated from this disclosure, the reverse osmosis centrifuge solves these problems and others.
Typical reverse osmosis systems for desalination comprise a reverse osmosis train (“RO Train”), which may include an intake, a high-pressure pump, a filter separated from the pump, and an energy recovery device. Filters used in reverse osmosis are unique because they require “Cross Flow Filtration.” To initiate the filtering process, the pump on typical RO Trains pushes salt water through the filter. With Cross Flow Filtration, a majority of the water mass moves across the filter, which is the saline concentrate. A desired feature of Cross Flow Filtration is that the large amount of concentrate acts as a cleanser as it moves across the filter, removing particles and prolonging the life of the filter. The water that does penetrate the filter is known as permeate and is often a small volume by percentage (e.g., 9%). The only valuable work produced by the reverse osmosis process is the permeate. However, energy is consumed by both the permeate and the concentrate. Because the concentrate is the waste product, the energy consumed by the concentrate is lost. To salvage some of the lost energy, energy recovery devices have been implemented in RO Trains. Energy recovery devices allow some of the energy that is placed into the system to be recovered. In particular, the energy recovery device was implemented in an attempt to transfer energy from the concentrate to the feed flow so as to not lose the majority of the energy consumed by the concentrate.
In contrast, the reverse osmosis centrifuge, described herein, generally conserves the energy of the concentrate by converting it to rotational energy. In one embodiment, the reverse osmosis centrifuge comprises a plurality of receiving tubes, a plurality of departure tubes, a support shaft, a plurality of housings with filters therein, and a trough. The plurality of receiving tubes are coupled to a top of the plurality of housings, while the plurality of departure tubes are coupled to a bottom of the plurality of housings. As seawater enters the receiving tubes, it flows to the plurality of housings, where centrifugal force creates the permeate and concentrate via the filters.
Centrifugal force (also known as a fictitious force) is an inertial force. This inertial force creates radial outward movement and pressure. Generally speaking, the faster an object is spinning, the greater the radially-outward force. This outward force creates pressure on seawater. The reverse osmosis centrifuge creates radial force on water entering the plurality of housings. The faster the plurality of housings spin, the greater the pressure. Unlike a RO Train, used in the prior art, where the pump is separated from the filter elements, the reverse osmosis centrifuge creates efficiencies by combining the pumping action and the filtration action into one revolving/centrifuge apparatus. Through the design of the reverse osmosis centrifuge, many major components of a RO Train become irrelevant. The two major components being replaced are the high-pressure pump and energy recovery device. Both of these devices are inherent features of the reverse osmosis centrifuge. It will be appreciated that the reverse osmosis centrifuge operates on the principle of taking water to a high pressure state, exhausting a fixed percentage of that water through the filters, and then recovering the energy in the concentrate water by taking it to a low pressure state before ejection through the plurality of departure tubes, thereby foregoing the need for an energy recovery device. Thus, and in stark contrast to the prior art, the reverse osmosis centrifuge is a cross flow filtration device that only exhausts energy into the filtered water (i.e., permeate) and not the concentrate.
As shown in
When the reverse osmosis centrifuge 100 begins to operate, saltwater enters the first trough 114 by way of a fluid inlet 122. While saltwater may enter the reverse osmosis centrifuge 100, it will be appreciated that the reverse osmosis centrifuge 100 may be used with salt-free water as well. A single fluid inlet 122 is shown; however, there may be a plurality of fluid inlets so as to deposit additional saltwater into the system. The shape and form of the fluid inlet 122 may also vary. For example, the fluid inlet 122 may be non-angled and have a large diameter. Further, in one embodiment, the first trough 114 may be sealed with, for example, a cap so that water entering through a sealed fluid inlet 122 can pressurize the system, preventing backflow of the seawater and providing for the removal of the viscous concentrate from the plurality of departure tubes 110. In one embodiment, water entering the fluid inlet 122 may be pressurized, such as by using a pump.
Referring to
In one embodiment, the plurality of housings 106 may be stacked vertically to increase permeate production, while maintaining the same square footage. Further, in one embodiment, the stacked housings 106 may have static turbines therebetween so as to drive feed flow. The plurality of housings 106 may be made of a fiberglass material that can compensate for pressure differential cycles during rotation, which creates better aerodynamics, structural resistance to a pressure differential, and vibration resistance. However, the plurality of housings 106 are not limited to fiberglass and may be other materials, such as aluminum, carbon fiber, plastic, etc.
In addition, the plurality of housings 106 may be a single unit that is seamless, airtight, and a smooth enclosure, thereby decreasing the windage effect. With the plurality of housings 106 being airtight, a body of air is sealed inside. At RPM, the body of air undergoes the same centrifugal and pressure gradient effects as the saltwater, forcing the air against the housing 106. If the plurality of housings 106 are not airtight, then unnecessary air consumption may occur. However, in some embodiments, the plurality of housings may be multiple sealable components that may be removably attachable and adjustable.
As shown in
Referring to
As shown in
The reverse osmosis centrifuge 100 requires no energy recovery device because the process of recovering energy from the concentrate is an inherent function of the reverse osmosis centrifuge 100 because the concentrate returns to the axis. To show this effect, an equation that returns the torque necessary to rotate the device at a given diameter, RPM/pressure, and flow rate is shown. The formula is W=Q [Pgauge+(½)p(Q{circumflex over ( )}2/A{circumflex over ( )}2) (½)p(w{circumflex over ( )}2)(r{circumflex over ( )}2). This equation is a simplified application of the first Law of Thermodynamics. For example, at a 36″ radius, 1097 rpm, 800 psi, and 6 gpm of flow, ˜4.15 kw is required for continuous rotation. At an 18″ radius, 3470 rpm, 2000 psi, and 20 gpm of flow, ˜33 kw is required for continuous rotation. The examples above illustrate the torque necessary assuming no energy recovery is used with the system, which means that the concentrate and permeate are being ejected at the circumference of the reverse osmosis centrifuge 100, similar to what is shown in
However, by moving the concentrate back to the center of the reverse osmosis centrifuge 100 by utilizing departure tubes 110, pressure/velocity is converted back into rotational energy. To illustrate this effect, a simple modification can be made to the flow rate equation. As an example, and to show the effect of the concentrate moving toward the center, at a 36″ radius, there is 800 psi, 6 gpm of concentrate flow toward the filter, 0.25 gpm of permeate production, and 5.75 concentrate flow leaving the filter traveling back toward the radius. As long as the flow is moving outward, the flowrate is a positive number; if the flow is moving in the opposite direction, the flowrate is a negative number. For continuous rotation, ˜4.15 kw is required for 6 gpm flow, and ˜−3.97 kw is required for 5.75 gpm return flow. 4.15 kw −3.97 kw=−0.18 kw (permeate energy consumption).
It should be noted that the difference between these two values is the energy required to produce the permeate. As shown and described above, the reverse osmosis centrifuge 100 only exhausts energy into the permeate production and none into the concentrate, which is a significant improvement over the prior art. In contrast, the prior art RO Trains exhaust energy into the permeate production and the concentrate, thus necessitating the use of an energy recovery device.
Further, the fluid pressure gradient is an inherent effect of the reverse osmosis centrifuge 100. At a given RPM, as fluid moves outward from the radius (i.e., axis), the fluid pressure increases. Pressure in the reverse osmosis centrifuge 100 is a function of the Specific Gravity of the solution, RPM, and the distance from the center of the axis. The following equation illustrates this relationship and the units are in Pa and Meters. The equation is PSI=5.4831 (r{circumflex over ( )}2)(RPM{circumflex over ( )}2). As an example of how this equation is applied, at a 24″/0.6096 m radius, an RPM of 2708 is required to create 800 psi/5.5 MPA of fluid pressure. At a 96″/2.4384 m radius, an RPM of 411 is required to create 800 psi/5.5 MPA of fluid pressure. In the examples above, as the radius increases, the RPM necessary to create a given fluid pressure decreases, and as the radius decreases, the RPM must then increase. Those familiar with fluid dynamics will appreciate that there will be some variance in the formulas above due to temperature, viscosity, and other variables, but the above formulations illustrate the technology and may be adaptable to conditions by those in the art.
Therefore, in one method of use, saltwater enters the reverse osmosis centrifuge 100 at first position 103 located at the center, vertical axis (i.e., shaft 102). As the reverse osmosis centrifuge 100 rotates on the support shaft 102 (i.e., shaft 102 spins/rotates on its longitudinal axis), saltwater is forced radially outward through the plurality of receiving tubes 104. As the saltwater travels outwardly from the center, the water pressure increases and reaches its max pressure at the housings 106, located at a second position 125, containing the filter 108. The permeate then exits into the trough 112 and the concentrate returns to the center axis, at a third position 135, via departure tubes 110. Because the concentrate returns to center, its pressure is recovered prior to leaving the system. It will be appreciated that while receiving tubes 104 and departure tubes 110 are used as examples, other components (e.g., trays) and methods of moving water from a first, centered position, to a second, radially distant, position for filtering, and then returning concentrate to a third, centered position, may be used and do not depart herefrom.
In one embodiment, as shown in
In one embodiment, a reverse osmosis centrifuge comprises a rotatable housing, having an oblate spheroid form factor, having a water inlet and a plurality of water outlet arms. The rotatable housing is motor controlled so as to be easily rotatable (i.e., spinnable). As the rotatable housing spins, water in the rotatable housing is forced outward into the plurality of outlet arms. Each outlet arm extends radially from the rotatable housing. As water travels through each outlet arm, pressure increases. Accordingly, a desalination membrane or filter is positioned toward the distal end of each outlet arm where pressure is the highest. As a result, of the pressurized separation, concentrate exits a concentrate outlet and permeate exits the permeate outlets. The reverse osmosis centrifuge further comprises a trough for receiving the output from the concentrate outlets and permeate outlets, the trough divided into a concentrate trough and permeate trough so as to ensure separation of the permeate from the concentrate. The concentrate trough having a concentrate outlet and the permeate trough having a permeate outlet. In one embodiment, the concentrate trough is located near the axis of rotation.
Exemplary embodiments are described above. No element, act, or instruction used in this description should be construed as important, necessary, critical, or essential unless explicitly described as such. Although only a few of the exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in these exemplary embodiments without materially departing from the novel teachings and advantages herein. Accordingly, all such modifications are intended to be included within the scope of this invention.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/859,786, filed on Jun. 11, 2019, which is incorporated herein by reference.
Number | Date | Country | |
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62859786 | Jun 2019 | US |