System and method for separation of solids from a liquid

Abstract

A system and method to separate a solid from a liquid, such as desalination to remove salt from saltwater, atomizes the liquid to create liquid droplets. The droplets have a surface area great enough that the liquid can be rapidly vaporized into a process air stream traveling through a container. The droplets may be approximately 20 pm in diameter, in an example. The exhaust of the container is connected to a particle separator via ducting. The moist gas exiting the particle separation unit passes through a condenser to drop the gas temperature below the dewpoint. The result is a transition from gas to liquid, after which the resulting solids-free liquid may be recovered. The process may alternatively be used to recover a desired solid from a liquid.

Description

SYSTEM AND METHOD FOR SEPARATION OFSOLIDS FROM A LIQUIDBACKGROUND OF THE I NVENTION

[0001] Seawater has served as a source for salt for thousands of years. Salt has many uses including flavoring of foods, preservation of foods, etc. Early harvesting of salt from seawater primarily focused on evaporation of the water using solar energy, thereby leaving the salt behind. This requires vast surface areas to provide the required mass of salt.

[0002] As human populations and technologies have expanded, so too has the demand for salt, paralleled by an increased need for freshwater. In regions where freshwater resources are already scarce, rapid population growth poses a significant constraint on sustainable development and the population capacity of these areas.

[0003] Multistage flash desalinators are an effective technology, but something more efficient was needed for larger onshore applications. In the late 1960's and early 1970' s, reverse osmosis (hereinafter referred to as "RO") systems were tested for their ability to desalinate seawater for drinking water and industrial applications. Today, more than 21,000 RO desalination plants are operating around the globe, with Saudi Arabia having the largest systems.

[0004] RO systems are unable to capture all of the water from the seawater input into these processes. For example, with RO systems approximately 42% of the water input into the system is recovered. The remaining 58% (which contains most all the salt from the original input stream and is termed "reject brine") must be disposed of. This disposal is typically done by pumping the reject brine back into the ocean. The release point (usually miles offshore) for the reject brines is very often a direct threat to the flora and fauna in the area near these injection points.

[0005] An improved system and method for separating a liquid from solids within the liquid, such as in the application of desalination, is therefore desired.SUMMARY OF THE INVENTION

[0006] The present invention is directed to a system and method to separate solids from a liquid, such as but not limited to desalinating saltwater, by atomizing the liquid. The resulting liquid droplets having a surface area great enough that the liquid can be rapidly vaporized into a process gas stream traveling through an enclosure. In certain embodiments, the droplets areapproximately 20 pm in diameter. The exhaust of the container is connected to a particle separator via ducting. The moist gas exiting the particle separation unit passes through a heat exchanger to drop the gas temperature below the dewpoint. The result is a transition from gas to liquid, after which the resulting liquid (separated from the solids) may be recovered.

[0007] In certain embodiments of the present invention, the system and method allows for a desalination system capable of recovering up to 95% of water from seawater or other saltwater sources.

[0008] In certain embodiments of the present invention, the system and method generates little or no reject brine.

[0009] In certain embodiments of the present invention, the system and method does not require any disposal of brine back into oceans or other disposal locations.

[0010] These embodiments are not limited to the removal of salts from water only. Separation of milk solids (also known as "powdered" milk) is another application for this process in certain embodiments of the invention. The protein, sugars, etc. suspended in milk are separated from the liquid phase. The volatilize water is recondensed and reused as water for cattle, etc.

[0011] Recovery of sugar from sugarcane processing is another application for this process in certain embodiments of the invention. The juices of the sugarcane are mechanically separated from the solids of the sugarcane. This liquid is processed to yield a high concentration of sugars. The present invention may be utilized to further dewater the sugar crystals to near dryness.

[0012] In another application, this process in certain embodiments can remove proteins from suspension such as those found in certain pharmaceutical processes.

[0013] Yet another application of this process in certain embodiments is the removal of microorganisms, e.g., yeast and bacterial from suspension in the aqueous phase.

[0014] These and other features, objects and advantages of the present invention will become better understood from a consideration of the following detailed description of the preferred embodiments and appended claims in conjunction with the drawings as described following:BRI EF DESCRI PTION OF DRAWINGS

[0015] Fig. 1 is an architectural diagram providing an overview of a system according to an embodiment of the present invention.

[0016] Fig. 2 is a diagram illustrating liquid jet breakup at different relative pressures between a liquid and surrounding gas at the atomizer.

[0017] Fig. 3 is an elevational cut-away view of a gas-assisted atomizer according to an embodiment of the present invention.

[0018] Fig. 4 is a diagram illustrating flow in a flow-blurring atomizer according to an embodiment of the present invention.

[0019] Fig. 5 is a diagram illustrating ultrasonic atomization.

[0020] Fig. 6 is a perspective view of an ultrasonic atomizer according to an embodiment of the present invention.

[0021] Fig. 7 is an illustrating of an electrostatic atomizer according to an embodiment of the present invention.

[0022] Fig. 8 is an elevational cut-away view of a rotary atomizer according to an embodiment of the present invention.DETAI LED DESCRIPTION OF TH E I NVENTION

[0023] Before the present invention is described in further detail, it should be understood that the invention is not limited to the particular embodiments described, and that the terms used in describing the particular embodiments are for the purpose of describing those particular embodiments only, and are not intended to be limiting, since the scope of the present invention will be limited only by the claims.

[0024] A system and method for implementation of the present invention may be described with reference to Fig. 1. In this embodiment the system is used for desalination of wastewater or seawater, but the invention is not so limited.

[0025] As a first step, the wastewater 10 is cleaned of any suspended material such as seaweed, trash, aquatic life, and any other suspended particle larger than 50 pm. The water is introduced to air stripper 14, and pressure is introduced by pressurized air source 12. This begins the process of removing suspended particles. Next, the resulting water is sent to electrocoagulation processor 16, which continues the process of removing particles larger than 50 pm. Then the water is sent to settler / clarifier 18 to complete the cleaning process. Solids / sludge 22 are separated from the water by settler / clarifier 18.

[0026] In alternative embodiments, any sort of solids, such as metals, organics, and organics, may be removed in this way. Flocculation methods may include chemical flocculation. Filtration may be, for example, through clays, activated charcoal, or sand. Coagulation may be alternatively performed through air stripping followed by gas filtration.

[0027] Next, the clean water is atomized into droplets at atomizer 20, using pressurized air 12.(The alternative technologies for implementing atomizers 20 will be discussed in more detail below.) In certain embodiments, the diameter of the droplets is about 20 pm, or averages (arithmetic mean) to about 20 pm. In certain embodiments, the size of the largest droplets may be up to 25 pm. In certain embodiments, the size of the droplets may vary across a range with a minimum value of 5 pm and a maximum value of 35 pm. In certain embodiments, the size of the droplets may vary across a range with no minimum value (or a 0 pm minimum value) and a maximum value of 50 pm.

[0028] The surface area of these droplets is great enough that the water can be rapidly vaporized into the process air stream 12 which is traveling through atomizers 20. The exhaust of atomizers 20 is connected to a dust collection system 24. Process air stream 12 may be created, for example, using centrifugal fans and flowers or axial fans, as non-limiting examples. The system may be designed to either push gas through atomizers 20 or to pull gas through atomizers 20, in alternative embodiments.

[0029] Dust collection 24 may be implemented in a number of ways in various alternative embodiments. These implementations may include, by way of example and not limitation, cartridge filters, bag filters, cyclone filters, and any combination thereof. Another alternative embodiment would perform separation by volume expansion of the gas flow. Part of the output of dust collection 24 may be sent to solids / sludge 22.

[0030] The saturated air 26 exiting atomizers 20 and dust collection 24 passes through condensers 30 that can sufficiently drop the air temperature below the dewpoint, causing the gaseous purified water 28 to transition to liquid water. This purified water 28 is then recovered as fresh water. Salt may also be recovered for disposal or use in various applications for which salt is desired. In an embodiment, the system as shown in Fig. 1 may recover 95% of the freshwater from the input wastewater stream 10.

[0031] The condensation process at condensers 30 occurs when air comes into contact with a cold surface whose temperature is below the dewpoint temperature of the air. This cold surface may be achieved through methods such as vapor compression cycles, absorption refrigeration cycles, reversed Brayton cycles, or thermoelectric cycles, as non-limiting examples.

[0032] With reference now to Fig. 2, an embodiment of the invention wherein atomizers 20 use hydraulic or pressure atomization may be described. In this method of atomization, liquid is forced through a small orifice or nozzle 32 at high pressure, resulting in the formation ofdroplets 34. In the case where the liquid pressure of the input mixture is larger than the air pressure, then relatively course droplets are formed, as shown in part (a) of Fig. 2. In the case where the liquid pressure of input mixture is much larger than the air pressure, then relatively fine droplets are formed, as shown in part (b) of Fig. 2. The balance of pressures should be such that sufficiently small droplets 34 are formed such that the surface area of the droplets is high enough relative to their liquid volume for liquid / gas separation to take place as described herein.

[0033] With reference now to Fig. 3, an atomizer 20 of the air (gas-assisted) atomization type may now be described. In air (or another gas, such as steam, nitrogen, hydrogen, etc.) atomization, the liquid is atomized by passing it through a nozzle 32. Nozzle 32 has a central bore 34 through which the liquid passes, and one or more outer bores 36 through which the gas passes. The gas is directed by outer bores 36 into the stream of liquid from central bore 34 as the liquid exits central bore 34 The energy from the gas striking the liquid stream breaks up the liquid into droplets.

[0034] With reference now to Fig. 4, an atomizer 20 using flow blurring may now be described. Flow blurring is a type of atomization that occurs when the backflow 38 of a gas creates a pattern of small disturbances in the flow of a liquid. Nozzle 32 in this case is designed to create this backflow 38 as the gas is introduced to the liquid on the upstream side of nozzle 32.

[0035] With reference now to Figs. 5 and 6, an atomizer 20 using ultrasonic atomization may be described. Ultrasonic atomization involves the use of ultrasonic vibrations to break up the liquid into fine droplets 34. In this case, an ultrasonic energy source 36, such as a piezoelectric crystal, may create the ultrasonic vibration as a result of a high-frequency input voltage 40. In one configuration, the ultrasonic energy force is sandwiched between a reflecting horn 38 and an atomizing horn 42, the latter of which is connected to nozzle to provide longitudinal vibration to nozzle 32. Liquid arriving at inlet 42 passes through these components to nozzle 32, where the vibration imparted to the liquid results in fine droplets 34.

[0036] With reference now to Fig. 7, an atomizer 20 using electrostatic (or electrohydrodynamic) atomization may be described. In electrostatic atomization, an electrical field is applied to the liquid as it passes through nozzle 32, causing it to break up into charged droplets 44. These charged droplets may then be directed and controlled using electric fields. The electric field is implemented by connecting nozzle 32 (functioning as one electrode) to high- voltage power supply 46, with high-voltage power supply 46 also being connected to a targetelectrode 48. In alternative embodiments, either nozzle 32 or target electrode 48 may be the anode or cathode, depending upon the polarity of high-voltage power supply 46. Nozzle 32 in this case may be a syringe pump.

[0037] With reference now to Fig. 8, an atomizer 20 using rotary (centrifugal) atomization may now be described. In rotary atomization, the liquid is spun at high speeds in a cavity 50, and then forced through a nozzle 32. Nozzle 32 in this embodiment may be of a rotary or disk shape, with the nozzle 32 discharging at the periphery of the disk. The cavity 50 and nozzle 32 may be driven by a motor 52, which provides the source of rotation.

[0038] Each atomization system has its own advantages and disadvantages, and the choice of method in different embodiments of the invention depend upon factors such as the desired droplet size, flow rate, viscosity of the liquid, surface tension, and application requirements.

[0039] It may be understood from the foregoing description that the system and method described may allow for the separation of all dissolved solids from liquids via the generation of microdroplets using atomizers. This atomization process creates microdroplets with vast surface area relative to the volume of liquid, and thus can be quickly volatilized in an incoming gas stream. This may take place at temperatures where the dissolved solids are still solids, and thus these solids may be removed in a solid state. In this state, the solids (a non-limiting example being salt) may be physically removed from the gas stream.

[0040] In an alternative process focused on liquid recovery rather than solids recovery, the vaporized liquids are recovered by dropping the temperature below the dewpoint for the liquid. In one implementation, the temperature of the vaporized liquid may be lowered by condensing the vaporized liquid on the surface of cooler materials.

[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, a limited number of the exemplary methods and materials are described herein. It will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein.

[0042] All terms used herein should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0043] When a grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included.

[0044] When a range is stated herein, the range is intended to include all sub-ranges within the range, as well as all individual points within the range.

[0045] When "about," "approximately," or like terms are used herein, they are intended to include amounts, measurements, or the like that do not depart significantly from the expressly stated amount, measurement, or the like, such that the stated purpose of the apparatus or process is not lost.

[0046] All references cited herein are hereby incorporated by reference to the extent that there is no inconsistency with the disclosure of this specification.

[0047] The present invention has been described with reference to certain preferred and alternative embodiments that are intended to be exemplary only and not limiting to the full scope of the present invention, as set forth in the appended claims.

Claims

CLAIMS1. A system for separating solids from a liquid, comprising: an atomizer configured to atomize the liquid into droplets; a container connected to the atomizer, the container configured to receive the droplets and a process gas stream; a particle separator connected to the container via ducting, the particle separator configured to separate solid particles from the process gas stream; and a condenser connected to the particle separator, the condenser configured to cool the process gas stream below its dew point to condense vapor in the process gas stream into a liquid.

2. The system of claim 1, wherein the atomizer is configured to produce droplets with an average diameter of about 20 pm.

3. The system of claim 1, wherein the atomizer is configured to produce droplets with a diameter in a range of 5 pm to 35 pm.

4. The system of claim 1, wherein the atomizer is selected from the group consisting of a hydraulic atomizer, a gas-assisted atomizer, a flow-blurring atomizer, an ultrasonic atomizer, an electrostatic atomizer, and a rotary atomizer.

5. The system of claim 1, further comprising an electrocoagulation process unit configured to remove suspended material from the liquid prior to atomization.

6. The system of claim 1, wherein the particle separator is selected from the group consisting of a cartridge filter, a bag filter, a cyclone filter, and combinations thereof.

7. The system of claim 1, wherein the liquid comprises saltwater comprising water and salt, and the system is configured to recover up to 95% of the water from the saltwater.

8. The system of claim 1, wherein the liquid comprises sugar water comprising pure water and sugar, and the system is configured to recover up to 95% of the pure water from the sugar water.

9. The system of claim 1, wherein the liquid comprises a water and protein suspension, and the system is configured to recover up to 95% of the water from the water and protein suspension.

10. The system of claim 1, wherein the liquid comprises a water and microbial cell suspension, and the system is configured to recover up to 95% of the water from the microbial cell and water suspension.

11. The system of claim 7, further comprising a salt recovery unit configured to collect separated salt particles.

12. The system of claim 1, wherein the condenser is configured to implement a cooling method selected from the group consisting of vapor compression cycles, absorption refrigeration cycles, reversed Brayton cycles, and thermoelectric cycles.

13. The system of claim 4 comprising a gas-assisted atomizer, wherein the gas-assisted atomizer comprises a nozzle with a central bore for liquid passage and one or more outer bores for gas passage.

14. The system of claim 4 comprising an ultrasonic atomizer, wherein the ultrasonic atomizer comprises an ultrasonic energy source, a reflecting horn, and an atomizing horn connected to a nozzle.

15. A method for separating solids from a liquid, comprising: atomizing the liquid into droplets; introducing the droplets into a process gas stream within a container; vaporizing the droplets into the process gas stream; separating solid particles from the process gas stream using a particle separator; cooling the process gas stream exiting the particle separator below its dew point; and condensing vapor in the cooled process gas stream to recover the liquid separated from the solids.

16. The method of claim 15, wherein atomizing the liquid produces droplets with an average diameter of about 20 pm.

17. The method of claim 15, wherein atomizing the liquid produces droplets with an average diameter in a range of 5 pm to 35 pm.

18. The method of claim 15, wherein atomizing the liquid is performed using an atomizer selected from the group consisting of a hydraulic atomizer, a gas-assisted atomizer, a flow-blurring atomizer, an ultrasonic atomizer, an electrostatic atomizer, and a rotary atomizer.

19. The method of claim 15, further comprising removing suspended material from the liquid using an electrocoagulation process prior to atomizing the liquid.

20. The method of claim 15, wherein separating solid particles is performed using a particle separator selected from the group consisting of a cartridge filter, a bag filter, a cyclone filter, and combinations thereof.

21. The method of claim 15, wherein the liquid comprises seawater comprising water and salt, and the method recovers up to 95% of the water from the seawater.

22. The method of claim 15, wherein cooling the process gas stream is performed using a method selected from the group consisting of vapor compression cycles, absorption refrigeration cycles, reversed Brayton cycles, and thermoelectric cycles.

23. The method of claim 18, wherein atomizing the liquid using a gas-assisted atomizer comprises passing the liquid through a central bore of a nozzle and passing a gas through one or more outer bores of the nozzle.

24. The method of claim 18, wherein atomizing the liquid using an ultrasonic atomizer comprises generating ultrasonic vibrations using an ultrasonic energy source, reflecting the vibrations with a reflecting horn, and transmitting the vibrations to the liquid through an atomizing horn connected to a nozzle.

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