REVERSE OSMOSIS CENTRIFUGE

The reverse osmosis centrifuge converts rotational energy into fluid velocity and conserves the energy placed into the concentrate. As concentrate travels back towards the center of the reverse osmosis centrifuge, the velocity of the fluid is converted into rotational force, thus conserving energy placed into the concentrate. To accomplish this, the reverse osmosis centrifuge includes 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. Centrifugal force creates the permeate and concentrate. The permeate exits the plurality of housings and is deposited into the permeate trough. The concentrate travels through, and exists from, the plurality of departure tubes.

TECHNICAL FIELD

The present disclosure relates to desalination. More particularly, the present disclosure relates to a centrifugal system and method to aid in desalination of water.

BACKGROUND

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.

SUMMARY OF EXAMPLE EMBODIMENTS

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.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

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.

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 inFIGS. 1-5, in one embodiment, a reverse osmosis centrifuge100comprises a support shaft102, a plurality of receiving tubes104, a plurality of housings106with filters108(e.g., reverse osmosis membranes) therein, a plurality of departure tubes110for the outlet of concentrate, and a permeate trough112. The reverse osmosis centrifuge100may be six feet in diameter and eight feet tall. However, the reverse osmosis centrifuge100is not limited to those dimensions and may be other dimensions, depending upon the available energy input and desired output amount. The support shaft102may receive a first trough114and a second trough116. The support shaft102may rotate (e.g., motor-controlled), thereby rotating the first and second troughs114,116coupled thereto. In an alternate embodiment, the support shaft102may be static while the first and second troughs114,116have bearings and be motor-controlled so as to rotate around the support shaft102. The first trough114comprises a first support shaft aperture118so as to receive the support shaft102at a first end103(FIG. 4). The first trough114further comprises a plurality of first apertures120. While a plurality of apertures120are shown, it will be appreciated that one or more apertures may be used on the first trough114. Further, the plurality of receiving tubes104are coupled to the plurality of apertures120via a securement mechanism, such as glue, crimping, twist and lock, threads, screws, etc.

When the reverse osmosis centrifuge100begins to operate, saltwater enters the first trough114by way of a fluid inlet122. While saltwater may enter the reverse osmosis centrifuge100, it will be appreciated that the reverse osmosis centrifuge100may be used with salt-free water as well. A single fluid inlet122is 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 inlet122may also vary. For example, the fluid inlet122may be non-angled and have a large diameter. Further, in one embodiment, the first trough114may be sealed with, for example, a cap so that water entering through a sealed fluid inlet122can pressurize the system, preventing backflow of the seawater and providing for the removal of the viscous concentrate from the plurality of departure tubes110. In one embodiment, water entering the fluid inlet122may be pressurized, such as by using a pump.

Referring toFIGS. 5-6, as saltwater enters the fluid inlet122, it is deposited into the first trough114and flows into the plurality of receiving tubes104. The plurality of receiving tubes104are also coupled to receiving apertures124on a top126of the plurality of housings106. In a similar manner to the fluid inlet122, the plurality of receiving tubes104may be a different shape, diameter, or both. The saltwater deposited into the plurality of receiving tubes104is eventually deposited into the plurality of housings106, at a second position125that is radially distant to the shaft102, via gravity and centrifugal force. The plurality of housings106may be vertically positioned, allowing gravity to induce the feed flow (flow of saltwater through the reverse osmosis centrifuge).

In one embodiment, the plurality of housings106may be stacked vertically to increase permeate production, while maintaining the same square footage. Further, in one embodiment, the stacked housings106may have static turbines therebetween so as to drive feed flow. The plurality of housings106may 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 housings106are not limited to fiberglass and may be other materials, such as aluminum, carbon fiber, plastic, etc.

In addition, the plurality of housings106may be a single unit that is seamless, airtight, and a smooth enclosure, thereby decreasing the windage effect. With the plurality of housings106being 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 housing106. If the plurality of housings106are 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 inFIG. 7-8, the filter108may be positioned inside, and coupled to, the plurality of housings106. The filter108may be coupled to the plurality of housings106with an attachment mechanism, such as glue. It should be noted that the filter108follows the contours of the housing106. In other words, the curvature of the filter108and the inside of the plurality of housings106matches the curvature of the reverse osmosis centrifuge100, which makes use of the pressure gradient effect. By compartmentalizing each filter108into an individual housing106, centrifugal force can be easily transferred into the saltwater, rather than using a larger cylindrical filter known in the prior art. Centrifugal force creates pressure and pushes the saltwater into the filter108. The saltwater flowing across the filter108becomes concentrate, while the salt water/feed flow is pressurized against the filter108, and permeate is collected on the other side of the filter108. The filter108may separate the concentrate and permeate flow paths. The filter108may be a graphene filter, a film composite membrane, a cellulose triacetate membrane, cellulose acetate, or any other type of filter. Further, the filter108may have fibers that are cylindrical, spiral, etc. It will be appreciated that the geometries of the filter108and the housings106allow the exact cross flow rate induced by gravity. In other words, the saltwater falls through the concentrate flow path in the filter108due to gravity. Because the first position103(centered at the axis) is in the highest position, and the second, radially distant position125(distal end of the receiving tubes104) is in a lower vertical position, gravity aids in the overall flow of the saltwater to the filter. Additionally, because the concentrate outlet is located at a third position135, which is lower than both the first and second position103,125, respectively, gravity aids in the concentrate returning to the axis (shaft102). However, a pump may also be used in some embodiments so as to increase the flow rate. The permeate is ejected through a permeate outlet128, which is located at a bottom130(FIG. 8) of the plurality of housings106, and into a permeate trough112where it may exit the reverse osmosis centrifuge100.

Referring toFIG. 9, while the permeate is deposited into the permeate trough112, the concentrate is removed from the plurality of housings106by the plurality of departure tubes110that are coupled to the housings106by a plurality of departure apertures131(shown inFIG. 8). More specifically, the plurality of departure tubes110are coupled to the second trough116at a bottom of the reverse osmosis centrifuge100, through a plurality of second apertures132. The second trough116may also be coupled to the support shaft102via a second aperture134, at a third position135, which is vertically aligned with the first position103. After the plurality of departure tubes110are coupled to the second trough116, at the third position135, the concentrate may exit therefrom. The plurality of departure tubes110may be a variety of shapes and sizes. In one embodiment, the diameter of the departure tubes110may be smaller in diameter than the diameter of the receiving tubes104. This may be beneficial to aid in overcoming the loss of pressure due to the permeate that leaves the system. In other words, a smaller diameter departure tube110increases pressure to account for the pressure lost by the permeate, thereby bringing the system into equilibrium once again. Additionally, because the concentrate is denser than the incoming water in the receiving tubes104, a higher pressure in the departure tubes110may be needed in some scenarios. Further, a pump may be utilized to increase the pressure in the departure tubes110, either alone or in combination with smaller diameter departure tubes110. Additionally, the angle of the plurality of departure tubes110may change depending on the dimensions of the reverse osmosis centrifuge100.

As shown inFIG. 10, the path of the feed flow resembles a “U” shape where the feed flow enters through the fluid inlet122at the first position103. The flow path then gradually travels away from the first position103, located on the vertical axis, to create more fluid pressure, where it reaches its max pressure at the plurality of housings106at the second position125. The concentrate then gradually returns to center where it exits the plurality of departure tubes110at the second trough116at the third position135which is also located on the vertical axis. The objective of this geometry of the reverse osmosis centrifuge100is to maintain energy conservation in the feed flow. As the feed flow travels outward from the center, the centrifuge100adds energy to the fluid, which is manifested in a fluid velocity or centrifugal force. As the feed flow travels back towards the center, energy in the fluid is recovered through decreased velocity/centrifugal force, which aids in maintaining the rotation of the centrifuge100. The necessary energy to drive the reverse osmosis centrifuge100is the difference between the quantities of feed flow traveling out versus in relative to the center of the reverse osmosis centrifuge100. More specifically, when saltwater enters the plurality of receiving tubes104, the saltwater is at a first, low pressure138. As the saltwater travels down the plurality of receiving tubes104, the pressure increases to a second, medium pressure140due to the rotational force. Lastly, after saltwater enters the plurality of housings106, the saltwater is at a third, high pressure142(which occurs at second position125) where it meets the filter108and is separated into two flow paths, permeate and concentrate. It will be appreciated that there is no mechanical wear or interfering surfaces in the high pressure region (second position125) of the fluid, which may prevent wear on the reverse osmosis centrifuge100. When the concentrate leaves the filter108and housing106, it leaves in a reversed manner from how the saltwater entered. That is, from high pressure to low pressure as it is released via the plurality of departure tubes110at the third position135. It should be noted thatFIG. 10illustrates an increase in pressure by the lines gradually becoming closer together as it moves away from the support shaft102. In addition, referring toFIG. 10, the reverse osmosis centrifuge100may comprise support structures144. The support structures144may be an aluminum, steel, or composite bracing. In some embodiments, the support structures144may be disks placed around the support shaft102and coupled to the plurality of housings106. The support structures144may maintain the integrity of the apparatus when rotating so that the apparatus does not collapse or become otherwise damaged.

The reverse osmosis centrifuge100requires no energy recovery device because the process of recovering energy from the concentrate is an inherent function of the reverse osmosis centrifuge100because 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 centrifuge100, similar to what is shown inFIG. 11and discussed later herein.

However, by moving the concentrate back to the center of the reverse osmosis centrifuge100by utilizing departure tubes110, 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 centrifuge100only 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 centrifuge100. At a given RPM, as fluid moves outward from the radius (i.e., axis), the fluid pressure increases. Pressure in the reverse osmosis centrifuge100is 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 centrifuge100at first position103located at the center, vertical axis (i.e., shaft102). As the reverse osmosis centrifuge100rotates on the support shaft102(i.e., shaft102spins/rotates on its longitudinal axis), saltwater is forced radially outward through the plurality of receiving tubes104. As the saltwater travels outwardly from the center, the water pressure increases and reaches its max pressure at the housings106, located at a second position125, containing the filter108. The permeate then exits into the trough112and the concentrate returns to the center axis, at a third position135, via departure tubes110. Because the concentrate returns to center, its pressure is recovered prior to leaving the system. It will be appreciated that while receiving tubes104and departure tubes110are 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 inFIG. 11, a reverse osmosis centrifuge200comprises a substantially oblate spheroid housing202and water inlet204. The housing202comprises a first funnel206coupled to a first outlet arm208and a second funnel210coupled to a second outlet arm212. As a result, as the housing202spins, water is forced radially outward, where it is funneled through first funnel206and second funnel210to outlet arms208,212, respectively. As shown, the housing202and outlet arms208,212may be supported by framework214. Framework214may be supported using cables216that are coupled to center support218. As appreciated, the support framework214spins with the housing202. Again, water easily flows to the plurality of water outlets arms208,212and pressure builds at the end of each arm due to rotational forces and the length of the arms208,212. Accordingly, the rotationally-induced pressure (which may be referred to as “centrifugal” force) provides for desalination at a lower energy cost since the rotational pressure is more easily sustained than traditional pump pressures. This is due to the use of bearings to aid in the rotation of the housing202and framework214. In other words, the housing202and framework coupler220are able to rotate (i.e., spin) on the center support218through the use of bearings. Once the reverse osmosis centrifuge is spinning, it takes less energy to maintain the spinning than a traditional pump uses, particularly if high-quality, low friction bearings are used. As a result, pressure at the ends of arms208,212is maintained with less energy input. Additionally, there is no mechanical wear or interfering surfaces in the high pressure region of the fluid. As water travels through each outlet arm208,212, pressure increases. Accordingly, a desalination membrane or filter is positioned toward the distal end of each outlet208,212arm where pressure is the highest. The reverse osmosis centrifuge200may further comprise a trough222having a concentrate trough224and a permeate trough226for receiving the output from a concentrate outlet228and a freshwater outlet230. As a result, the reverse osmosis centrifuge desalinates water at a reduced energy cost, which translates into a reduced monetary cost, making the desalinating technology more readily available. It should be noted that, as mentioned earlier, the reverse osmosis centrifuge200does not return the concentrate to center, and is therefore not as efficient as other embodiments described herein.

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.