Patent Grant
12017155
The present invention relates generally to devices and methods for phase separation of aqueous mixtures. More specifically, the present invention relates to phase separation devices and methods using electrosorptive cavitation.
Many industrial processes involve one or more phase separation steps in which aqueous mixtures are processed to separate hydrophilic and hydrophobic phases or components, and/or to separate out contaminants, desirable products, or other components present in an aqueous mixture. In the field of algae processing, for example, algal lipids or oils are extracted from algae cultivated in an aqueous environment. Phase separation is also performed as part of waste water management operations, and in industrial mining operations, for example.
Lipid extraction and/or phase separation of aqueous mixtures may be costly, time-consuming, and/or may involve high energy demands. By way of example, algal biofuel production typically involves cell disruption, harvesting, de-watering, and lipid extraction steps. Such harvesting and de-watering has conventionally involved filtration, reverse osmosis, electrocoagulation-electroflocculation (EF-EC), centrifugation, and/or drum drying for concentration, and lipid extraction involving disruption or conversion of algae using pressure, stress, heat, or solvent treatment.
Currently, mechanical and high energy cell disruption methods such as high-pressure homogenisers or sonication typically involve an energy input in the order of hundreds of MJ kg−1 of the dry mass. Heat based approaches following the concentration of the biomass to at least 10 wt % may also lead to a lower quality of fuel while consuming the biomass, complicating recovery of other potentially valuable products. In addition, many laboratory process methods are not readily scalable, making commercial or pilot scale biofuel production difficult.
Hydrodynamic cavitation (HC) has been previously used for cell disruption, however the cell disruption by HC was periplasmic and thus mainly confined to the cell wall and membrane, and involved solvents for extraction following the HC process and additional unit operations for separation of the phases.
Alternative, additional, and/or improved devices and/or methods for phase separation of aqueous mixtures are desirable.
In certain embodiments, there are provided herein devices and methods for phase separation of aqueous mixtures using electrosorptive cavitation. Cavitation of aqueous mixtures may be used to generate a cavitated aqueous mixture, which may be subjected to electrosorption, thereby providing phase separation of the aqueous mixture. Such combination of cavitation and electrosorption as described herein may be used to achieve phase separation in a variety of different aqueous mixtures, including algal aqueous mixtures and/or mining or waste water aqueous mixtures, for example.
In an embodiment, there is provided herein a phase separation device for performing phase separation of an aqueous mixture, said device comprising:
In an embodiment of the above device, the device may be a lipid extraction and phase separation device for performing phase separation of an aqueous mixture, said device comprising:
In another embodiment of the above device or devices, the cavitated aqueous mixture may comprise cavitation voids comprising vapour, and the electrosorptive phase separation of the cavitated aqueous mixture may include electrosorptive vapour bubble generation.
In still another embodiment of the above device or devices, the electrosorption assembly may perform electrosorptive phase separation including microflotation.
In yet another embodiment of the above device or devices, the cavitation assembly may comprise a tangential flow aqueous mixture inlet, a vortex stabilizer in communication with the inlet, and a nozzle in communication with the vortex stabilizer, the nozzle comprising a divergent outlet in communication with the electrosorption assembly.
In another embodiment of the above device, the vortex stabilizer may comprise a vortex stabilizer insert comprising a conical portion having a longitudinal slit for allowing vortexing aqueous mixture to exit the vortex stabilizer and enter the nozzle.
In yet another embodiment of the above device or devices, the nozzle may comprise a restriction flow channel having a length L and a diameter d, wherein the restriction flow channel receives the aqueous mixture and directs the aqueous mixture to the divergent outlet.
In another embodiment of the above device, the restriction flow channel may have a d/L ratio of about 0.005-0.02.
In still another embodiment of the above device or devices, d may be about 0.03-0.0625 inches.
In another embodiment of the above device or devices, the divergent outlet may comprise a conical channel which progressively widens toward the electrosorption assembly with a divergent angle of about 30°-45°.
In still another embodiment of the above device or devices, the divergent outlet may have a diameter to length ratio of about 0.1875-0.3.
In another embodiment of the above device or devices, the electrosorption assembly may comprise a cathode and an anode, the cathode forming an outer shell defining an interior core, with the anode disposed within the core. In certain embodiments, the cathode may comprise a conductive spiral tube with a central core, and the anode may comprise a conductive member disposed within the central core. In certain embodiments, the cathode may comprise a longitudinal tube, coil, spiral, or other suitable structure, and may define an interior core having a longitudinal axis along which the anode is disposed. The cathode may be substantially continuous, or may comprise a series of individual members longitudinally oriented in series.
In yet another embodiment, the cathode may comprise a conductive spiral coil or tube comprising two or more turns, wherein each turn, in combination with the anode, may form a distinct electrochemical cell. In certain embodiments, the cathode may comprise an array of rings aligned in series, each forming a distinct electrochemical cell in combination with the electrode. The person of skill in the art having regard to the teachings of the instant application will be aware of suitable cathode/anode configurations, and will be able to select a suitable cathode/anode configuration suitable for a particular application.
In still another embodiment of the above device or devices, the cathode may comprise a carbon-based fiber conductive material, anodized aluminium, TiO2, brass, or stainless steel.
In yet another embodiment of the above device or devices, the device may be configured vertically or on an incline, such that the electrosorption assembly receives the cavitated aqueous mixture at a bottom end thereof and performs electrosorptive phase separation of the cavitated aqueous mixture as the cavitated aqueous mixture moves toward a top end of the electrosorption assembly, the top end being elevated relative to the bottom end. In certain embodiments, the cavitated aqueous mixture may exit the top end of the electrosorption assembly and be collected in a floatation cell or other phase separation tank.
In still another embodiment of the above device or devices, the electrosorption assembly may comprise a cathode and an anode, the cathode forming an outer shell defining an interior core, and the anode disposed within the core.
In yet another embodiment of the above device or devices, the cathode may comprise a continuous conductive member.
In another embodiment of the above device or devices, wherein the cathode may comprise a plurality of individual conductive members longitudinally aligned in series.
In still another embodiment, the cathode may comprise a tube, spiral, or coil. In yet another embodiment, the cathode may comprise two or more tubes, spirals, coils, or rings, or a combination thereof. In another embodiment, the tube, spiral, or coil may define a helix comprising two or more turns, wherein each turn, in combination with the anode, forms a distinct electrochemical cell. In still another embodiment, the cathode may comprise two or more spaced apart rings aligned in series, which form, in combination with the anode, a plurality of distinct electrochemical cells.
In certain embodiments, there is provided herein a method for continuous phase separation of an aqueous mixture, said method comprising:
In another embodiment of the above method, the cavitating the aqueous mixture produces cavitation voids comprising vapour within the cavitated aqueous mixture, and wherein the electrosorptive phase separation of the cavitated aqueous mixture induces electrosorptive vapour bubble generation.
In yet another embodiment of the above method or methods, the electrosorptive phase separation may include microflotation.
In still another embodiment of the above method or methods, the step of cavitating may comprise passing the aqueous mixture through a cavitation assembly as defined hereinabove.
In another embodiment of the above method or methods, the step of performing electrosorptive phase separation may comprise passing the cavitated aqueous mixture through an electrosorption assembly as defined hereinabove.
In another embodiment of any of the above device or devices, the aqueous mixture may comprise a microalgal culture. In certain embodiments, the microalgal culture may comprise Chlorella vulgaris algal biomass, Scenedesmus algal biomass, or a combination thereof, for example.
In still another embodiment of any of the above method or methods, the aqueous mixture may comprise a microalgal culture. In certain embodiments, the microalgal culture may comprise Chlorella vulgaris algal biomass, Scenedesmus algal biomass, or a combination thereof, for example.
In another embodiment of the above device or devices, the electrosorptive phase separation may include algal lipid extraction.
In another embodiment of the above method or methods, the electrosorptive phase separation may include algal lipid extraction.
Described herein are devices and methods for phase separation of aqueous mixtures using electrosorptive cavitation. Cavitation of aqueous mixtures may be used to generate a cavitated aqueous mixture, which may be subjected to electrosorption, thereby providing phase separation of the aqueous mixture. By way of example, in certain embodiments, the devices and methods described herein may be for lipid extraction from a lipid-containing aqueous mixture, such as an algal aqueous mixture. In such embodiments, cavitation of the aqueous mixture may generate a cavitated aqueous mixture comprising algal biomass, lipids, and water, which may be subjected to electrosorption. It will be appreciated that embodiments and examples are provided for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way.
In an embodiment, there is provided herein a phase separation device for performing phase separation of an aqueous mixture, said device comprising:
In another embodiment, there is provided herein a method for continuous phase separation of an aqueous mixture, said method comprising:
As will be understood, the aqueous mixture may be any suitable aqueous mixture comprising water and one or more suitable components to be separated therefrom. By way of example, suitable aqueous mixtures may include algal aqueous mixtures and/or mining or waste water aqueous mixtures. In certain embodiments, the aqueous mixture may include industrial waste water, or industrial mining waste water. The aqueous mixture may comprise, for example, marine algae, freshwater algae, microalgae, colloidal waste water, mine effluent, gold mine effluent, cement mine effluent, and/or waste water from a gold ore processing and refining operation, metallurgical coal production, another suitable mine water application, and/or a municipal sewage water treatment, for example. The skilled person having regard to the teachings herein will be aware of suitable aqueous mixtures for which phase separation may be desired.
It is contemplated herein that, in certain embodiments, the aqueous mixture may include an aqueous mixture for which removal of oxyanions such as Arsenic and Selenium may be desired; recovery of base and/or precious metals from effluents may be desired; cyanide destruction may be desired; ammonia removal may be desired; fermentation process water treatment may be desired; removal of contaminants from oils may be desired; and/or lignocellulosic biomass pre-treatment may be desired.
As will be understood, phase separation may include any suitable separation of aqueous mixture components, and may involve partial, substantial, or full phase separation. In certain embodiments, hydrophobic components and/or components having low water solubility present in the aqueous mixture may be separated from a water fraction. By way of example, phase separation may involve formation of separate hydrophobic (i.e. oil, lipid, or oleaginous) and hydrophilic (i.e. water) layers, or isolation/extraction of hydrophobic (i.e. oil, lipid, hydrocarbon) components from the aqueous mixture, or isolation/extraction of mixture components having low or reduced solubility in water, or collection of mixture components such as metals or other cations/anions (which may be, optionally, oxidized) and/or lipids and/or other hydrophobic components on the respective cathode or anode portion of the electrosorption assembly, or any combination thereof.
In certain embodiments, phase separation devices as described herein may be in fluid communication with one or more conventional separation systems, wherein processed liquids exit the phase separation device and enter the conventional separation system for further phase separation and/or isolation. By way of example, phase separation devices as described herein may be in fluid communication with one or more settling chambers, flotation tanks, or skimming tanks (see, for example, U.S. Pat. No. 8,968,571, which is herein incorporated by reference in its entirety) which receive processed sample from the phase separation devices as described herein and allow for further phase separation thereof.
The skilled person will recognize that phase separation as described herein may be used, in certain embodiments, to separate and/or isolate particular components of a given aqueous mixture, and/or to extract/remove particular contaminants from a given aqueous mixture, for example. In certain embodiments, phase separation may involve extraction of desirable components such as, for example, algal lipids/oils, lignocellulosic material, or valuable metals from an aqueous mixture. In certain other embodiments, phase separation may involve regeneration of waste water through removal of one or more hydrophobic or metal contaminants. As will be recognized, the components to be extracted or separated from the aqueous mixture via phase separation will depend on the particular aqueous mixture used, and the particular downstream application(s) of the aqueous mixture and/or component(s) separated therefrom.
The cavitation assembly may be any suitable assembly which can receive the aqueous mixture to be processed, and cavitate the aqueous mixture to produce a cavitated aqueous mixture. As will be understood, the cavitation assembly may process (i.e. cavitate) the aqueous mixture to form cavitation voids comprising vapour in the aqueous mixture. In certain embodiments, and without wishing to be bound by theory, at least some of such cavitation voids may collapse, thereby generating nuclei which may assist in electrosorptive phase separation in the electrosorption assembly, as described in further detail below. As will be understood, in certain embodiments, the cavitation assembly may comprise a nozzle, in which the aqueous mixture is received and directed to a divergent outlet section, as described in further detail below. The skilled person having regard to the teachings herein will be aware of suitable cavitation assembly designs, and will be able to select a suitable cavitation assembly for the particular application.
Where, for example, an algal aqueous mixture is to be processed, cavitation by the cavitation assembly may result in at least some disruption or breakage of the algal cell, thereby exposing desirable algal components such as, for example, algal lipids, which may collect on the cavitation voids. Where, for example, a mining waste water aqueous mixture is to be processed, cavitation by the cavitation assembly and action of the forming/collapsing cavitation voids may result in formation of at least some hydroxyl radicals, which may oxidize metals in the mining waste (i.e. an advanced oxidation (AOP) process), thereby altering metal solubility and/or preparing the metals for cathode attachment in the electrosorption assembly. As will be understood, in certain embodiments, chemical oxygen demand (COD) of an aqueous mixture may be altered by treatment described herein.
In certain embodiments, the cavitation assembly may comprise a tangential flow aqueous mixture inlet, a vortex stabilizer in communication with the inlet, and a nozzle in communication with the vortex stabilizer, the nozzle comprising a divergent outlet in communication with the electrosorption assembly. The tangential flow aqueous mixture inlet and vortex stabilizer may generate a swirl or spiral flow of the aqueous mixture entering the nozzle. The nozzle section may receive the spiral-flowing aqueous mixture, and direct the mixture to a divergent outlet section, as described in further detail below. In certain embodiments, the vortex stabilizer may comprise a vortex stabilizer insert comprising a conical portion having a longitudinal slit for allowing vortexing aqueous mixture to exit the vortex stabilizer and enter the nozzle.
In certain embodiments, the cavitation assembly may comprise a nozzle which may comprise a restriction flow channel having a length L and a diameter d, wherein the restriction flow channel receives the aqueous mixture and directs the aqueous mixture to the divergent outlet. In still another embodiment, the restriction flow channel may have a d/L ratio of about 0.005-0.02, for example. In yet another embodiment, d may be about 0.03-0.0625 inches, for example. In another embodiment, the divergent outlet may comprise a conical channel which progressively widens toward the electrosorption assembly, with a divergent angle of about 30°-45°, for example. In still another embodiment, the divergent outlet may have a diameter to length ratio of about 0.1875-0.3, for example.
The electrosorption assembly may be any suitable assembly which can receive the cavitated aqueous mixture, and perform electrosorptive phase separation of the cavitated aqueous mixture. As will be understood, the electrosorption assembly may comprise a cathode and an anode, to which certain components of the aqueous mixture may attach or agglomerate, thereby facilitating their separation from the aqueous mixture, for example. In certain embodiments, and without wishing to be bound by theory, the electrosorption assembly may multiply cavitation voids in the cavitated aqueous mixture through an advanced oxidation process, thereby providing electrosorptive vapour bubble generation. In certain embodiments, such electrosorptive vapour bubble generation may facilitate phase separation via microflotation. The skilled person having regard to the teachings herein will be aware of suitable electrosorption assembly designs, and will be able to select a suitable electrosorption assembly for the particular application.
In certain embodiments, for example, the electrosorption assembly may comprise a cathode and an anode, the cathode forming an outer shell defining an interior core, with the anode disposed within the core. By way of example, the cathode may comprise a conductive spiral tube with a central core, and the anode may comprise a conductive member disposed within the central core. In certain embodiments, the cathode may comprise, for example, a longitudinal tube, coil, spiral, or other suitable structure, and may define an interior core having a longitudinal axis along which the anode is disposed. The cathode may be substantially continuous, or may comprise a series of individual members longitudinally oriented in series. In yet another embodiment, the cathode may comprise a conductive spiral coil or tube comprising two or more turns, wherein each turn, in combination with the anode, may form a distinct electrochemical cell. In certain embodiments, the cathode may comprise an array of rings aligned in series, each forming a distinct electrochemical cell in combination with the electrode. The person of skill in the art having regard to the teachings of the instant application will be aware of suitable cathode/anode configurations, and will be able to select a suitable cathode/anode configuration suitable for a particular application.
Where, for example, an algal aqueous mixture is to be processed, electrosorptive phase separation by the electrosorption assembly may result in at least some attachment and/or aggregation of algal lipids/oils on the surface of a cathode portion of the electrosorption assembly. Without wishing to be bound by theory, it is believed that algal lipids/oils may accumulate on cavitation voids, nuclei, and/or other voids or vapour bubbles created by action of the cavitation and/or electrosorption assembly, which may then become attached to the cathode portion of the electrosorption assembly. Collapse of cathode-attached cavitation voids and/or other voids or vapour bubbles having algal lipids or oils attached thereto may further promote algal lipid or oil clumping or agglomeration at the cathode. Algal lipids or oils may then be retrieved from the cathode, and/or may be retrieved through flotation or other density separation, for example. By way of example, liquid exiting the electrosorption assembly may be allowed to phase-separate, and the lipid-rich layer may be collected. In certain embodiments, electrosorptive vapour bubble generation in the electrosorption assembly may facilitate phase separation through phase separation, particularly where algal-size bubbles (i.e. about 2-5 μm) are generated through regulation of pressure, flow, and/or energy applied at the electrosorption assembly.
Where, for example, a mining waste water aqueous mixture is to be processed, electrosorptive phase separation by the electrosorption assembly may include accumulation of cationic or oxidized metal species at the cathode, and anionic species at the anode. Action of the hydroxyl radicals resulting from formation/collapse of cavitation voids may result in oxidation of metals in the mining waste, thereby altering metal solubility and/or facilitating metals attachment to the cathode of the electrosorption assembly and corollary anions formed are further reduced in the process.
In certain embodiments, the electrosorption assembly may comprise a cathode and an anode, the cathode comprising a conductive spiral coil or tube defining an inner central core or passage, and the anode comprising a conductive member axially disposed within the central core or passage. In certain embodiments, the conductive spiral coil or tube of the cathode may comprise two or more turns, wherein each turn, in combination with the anode, may form a distinct electrochemical cell. As such will be understood, in certain embodiments, the anode of electrosorption assemblies as described herein are not sacrificial anodes, and the skilled person may therefore select an appropriate anode material accordingly.
In certain embodiments, the spiral cathode and anode may be enclosed within an outer shell, such that the cavitated aqueous mixture exiting the cavitation assembly (and having a spiral flow pattern) may encounter a flow channel having a substantially circular cross-section defined by the outer shell, and may become exposed to the cathode and anode of the electrosorption assembly as it passes through the flow channel. In certain embodiments, the spiral flow of the cavitated aqueous mixture passing through the flow channel, and the spiral structure (i.e. handedness, etc.) of the cathode may be matched, thereby providing reduced fluid flow resistance through the electrosorption apparatus and providing increased contact and residence time between the cavitated aqueous mixture and the electrosorptive assembly.
In certain embodiments, the cathode of the electrosorption assembly may comprise a carbon-based conductive material, copper, aluminium (with and without anodization), TiO2, brass, or stainless steel. In certain embodiments, the anode of the electrosorption assembly may comprise carbon, stainless steel, iron, or aluminium (anodized or non-anodized). The person of skill in the art having regard to the teachings provided herein will be able to select suitable cathode and anode materials based on the particular application, particular contaminants involved, desired effluent discharge limits, and/or other such considerations.
In further embodiments the phase separation device may be configured vertically or on an incline, such that the electrosorption assembly receives the cavitated aqueous mixture at a bottom end thereof and performs electrosorptive phase separation of the cavitated aqueous mixture as the cavitated aqueous mixture moves toward a top end of the electrosorption assembly, the top end being elevated relative to the bottom end. In certain embodiments, the cavitated aqueous mixture may exit the top end of the electrosorption assembly and be collected in a flotation cell or other phase separation tank.
The illustrated phase separation device (1) comprises a cavitation assembly (2) for cavitating an aqueous mixture to produce a cavitated aqueous mixture, and an electrosorption assembly (3) for receiving the cavitated aqueous mixture and performing an electrosorptive phase separation of the aqueous mixture.
Phase separation device (1) comprises a cavitation assembly (2), which is configured to receive the aqueous mixture to be processed, and cavitate the aqueous mixture to produce a cavitated aqueous mixture. The cavitation assembly (2) cavitates the aqueous mixture to form cavitation voids comprising vapour in the aqueous mixture, at least some of which may collapse, thereby generating nuclei which may assist in electrosorptive phase separation in the electrosorption assembly (3), as described in further detail below. Cavitation by cavitation assembly (2) results in at least some, or a majority of, the disruption or breakage of the algal cells of the aqueous mixture, thereby exposing desirable algal lipids, which collect on the surface of cavitation voids (bubbles) through lipid-bubble surface forces.
As shown in figure detail in
Low to high pressure (1724-11721 kPa, for example), which may depend on concentration of algal culture, algal cell size and shape, and/or desired throughput/flowrate, for example, may be applied to the tangential flow aqueous mixture inlet (6), and the tangential flow aqueous mixture inlet (6) and vortex stabilizer (7) may generate a swirl or spiral flow of the aqueous mixture entering the nozzle (13). In certain embodiments, for example, low pressure may be applied, such as a pressure of about 240 kPa to about 1825 kPa for example about 1724 kPa, and flow may be adjusted accordingly to maintain quality of lipid formed. The nozzle (13) may receive the spiral-flowing aqueous mixture, and direct the mixture to the divergent outlet (9). In the illustrated cavitation assembly (2), the vortex stabilizer (7) may comprise a vortex stabilizer insert (10) comprising a conical portion (11) having a longitudinal slit (12) for allowing vortexing aqueous mixture to exit the vortex stabilizer (7) and enter the nozzle (13). Vortex stabilizer insert (10) is shown in further detail in
Nozzle (13) comprises a restriction flow channel (8) having a length L and a diameter d (see
The cavitation assembly (2) cavitates the aqueous mixture to form cavitation voids comprising vapour in the aqueous mixture, at least some of which may collapse, thereby generating nuclei which may assist in electrosorptive phase separation in the electrosorption assembly (3). Aqueous mixture passing through divergent outlet (9) experiences partial pressure drop below the vapour pressure, resulting in the formation of such cavitation voids. When such cavitation voids collapse, sites of high-energy are created due to micro-implosions, resulting in generation of nuclei which enhance bubble production rate during electrosorption. In certain embodiments, and without wishing to be bound by theory, the bubble nuclei formed during cavitation may enhance the rate of formation of bubbles in the electrosorption and may lead to the propagation of bubble clouds. Lipid bubble attachment may occur in the bubble clouds, and lead to sorption of bubbles on the surface of the electrode.
Divergent outlet (9) of cavitation assembly (2) is in communication with electrosorption assembly (3), allowing cavitated aqueous mixture to exit cavitation assembly (2) and enter electrosorption assembly (3). In illustrated phase separation device (1), the cavitation assembly (2) and the electrosorption assembly (3) are coupled together via flange (14) as shown in
Electrosorption assembly (3) receives the cavitated aqueous mixture from the cavitation assembly (2), and performs electrosorptive phase separation of the cavitated aqueous mixture. As shown in
In phase separation device (1), electrosorption assembly (3) comprises a cathode (4) and an anode (5), the cathode (4) comprising a conductive spiral coil defining an inner central core or passage, and the anode (5) comprises a conductive rod-shaped member co-axially disposed within the central core or passage defined by the spiral-shaped cathode (4). The conductive spiral coil of cathode (4) comprises multiple turns, wherein each turn, in combination with the associated portion of anode (5), forms a distinct electrochemical cell. In the device of this example, one or more anode separators (16) as shown in
Although depicted as a spiral coil in this example, it will be understood that the cathode may adopt other suitable configurations. For example, in certain embodiments, the cathode may be configured as a longitudinal tube, coil, spiral, or other suitable structure, and may define an interior core having a longitudinal axis along which the anode is disposed. The cathode may be substantially continuous, or may comprise a series of individual members longitudinally oriented in series. The cathode may comprise a conductive spiral coil or tube comprising two or more turns, wherein each turn, in combination with the anode, may form a distinct electrochemical cell. In certain embodiments, the cathode may comprise an array of rings or other such units aligned in series, each forming a distinct electrochemical cell in combination with the anode. The person of skill in the art having regard to the teachings of the instant application will be aware of suitable cathode/anode configurations, and will be able to select a suitable cathode/anode configuration suitable for a particular application.
In this example, spiral cathode (4) and anode (5) are enclosed within an outer shell (15), which comprises a pipe or tube, such that the cavitated aqueous mixture exiting the cavitation assembly (2) (and having a spiral flow pattern) encounters a flow channel having a substantially circular cross-section defined by the outer shell (15) pipe, and becomes exposed to cathode (4) and anode (5) of the electrosorption assembly (3) as it passes through this flow channel. The spiral flow of the cavitated aqueous mixture passing through the flow channel, and the spiral structure (i.e. handedness, etc.) of cathode (5) are matched, thereby providing reduced fluid flow resistance through the electrosorption apparatus (3) and providing increased contact and residence time between the cavitated aqueous mixture and the electrosorptive assembly (3).
Cathode (4) of the electrosorption assembly (3) may comprise, for example, a spiral wound carbon-based fiber conductive material, activated or impregnated cloth conductive material, anodized aluminium, iron, TiO2, brass, or stainless steel, or other suitable conductive material. In phase separation device (1), a central core positive conductive source attached to an AC power input serves to enhance the advanced oxidation generated by cavitating nuclei, resulting in lipid-biomass-water phase separation through lipid-bubble interactions and reduced polarity of the algal cells rendering their effective separation and flotation of the lipid and algae phases with eventual settling of algae (by gravity) in the flotation cell in a single step.
In certain embodiments, the anode of the electrosorption assembly may comprise carbon, stainless steel, iron, or anodized aluminium. As will be understood, electrosorption assembly (3) performs electrosorptive function, and therefore does not comprise a sacrificial anode. As will be understood, electrosorption is based on sorption of material or contaminant on the electrodes, and does not involve release of electrode material. The electrode is thus non-sacrificial in the case of electrosorption.
Electrosorptive phase separation by electrosorption assembly (3) results in at least some attachment and/or aggregation of algal lipids/oils on the surface of cathode (4) of the electrosorption assembly (3). Without wishing to be bound by theory, it is believed that algal lipids/oils may accumulate on cavitation voids, nuclei, and/or other voids or vapour bubbles created by action of the cavitation and/or electrosorption assembly, which may then become attached to cathode (4) of electrosorption assembly (3). Collapse of cathode-attached cavitation voids and/or other voids or vapour bubbles having algal lipids or oils attached thereto may further promote algal lipid or oil clumping or agglomeration at cathode (4). Algal lipids or oils may then be retrieved from cathode (4), and/or may be retrieved through floatation or other density separation, for example. By way of example, liquid exiting electrosorption assembly (3) may be allowed to phase-separate, and the lipid-rich layer may be collected. In certain embodiments, electrosorptive vapour bubble generation in electrosorption assembly (3) may facilitate phase separation through phase separation, particularly where algal-size bubbles (i.e. about 2-5 μm) are generated through regulation of pressure, flow, and/or energy applied at the electrosorption assembly. Energy input by electrosorption assembly (3) may multiply cavitation voids in the cavitated aqueous mixture via an advanced oxidation process, thereby providing electrosorptive vapour bubble generation. Such electrosorptive vapour bubble generation may further facilitate phase separation via microflotation. Without wishing to be bound by theory, in certain embodiments, cavitation bubbles may be considered as nuclei which collapse with high intensity and tensile forces in algae culture, for example. This may allow for early nuclei to form in the electrosorption section and cause increased bubble generation. Separation may occur by lipid-bubble attachment with algae, the separated layers travelling up the tube into a microflotation cell, which may accelerate separation of phases, for example.
Phase separation device (1) described in this Example is designed to operate in single step-fashion, without requiring addition of added chemicals, solvents, flocculants, adsorbents, or pH buffer agents (it will be recognized that nutrients supplied to the culture during the algal growth in the photobioreactors may be present in examples where an algal aqueous mixture is to be processed). The combination of hydrodynamic cavitation and electrosorption design in a single step as described in this example may allow for scale-up and reduced complexity for one-step processes for both extraction and separation.
As will be recognized, phase separation device (1) employs electrosorption. Electrosorption is generally considered as potential-induced adsorption of molecules on the surface of charged electrodes, and is used herein for separation of phases with the use of high specific-area electrodes. Electrosorption involves charging and discharging the electrical double layer at the surface of electrodes by applying potential or current. In this respect, electrosorption is distinguished from conventional electrochemical or Faradaic processes such as electrocoagulation or electroflocculation, and offers in-situ regeneration of adsorbent with good energy consumption compared with the other separation processes (see, for example, Yang, K. L., Ying T-Y, Yiacoumi, S., Tsouris, C and Vittoratos, S. Electrosorption of Ions from Aqueous Solutions by Carbon Aerogel: An Electrical Double-Layer Model, Langmuir, 2001, 17 (6), pp 1961-1969; herein incorporated by reference in its entirety).
The phase separation device of this Example has been tested for continuous flow operation of up to about 1.5 L/min in the processing of algal aqueous mixtures having an algal concentration of about 0.1 g/L and 1 g/L.
A series of experiments were designed and performed in order to test phase separation of algal aqueous mixtures using phase separation devices as described herein. Testing included analysis of individual cavitation assemblies and electrosorption assemblies, and testing of combined electrosorptive cavitation phase separation devices as described herein.
The following tables provide experimental set-up and processing conditions of various experiments designed to assess the electrosorptive cavitation devices described herein. Experimental observations for each test are provided, along with accompanying figure(s) depicting experimental setup and processed samples produced.
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Experimental setup, and processed sample produced, shown in
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Experimental setup, and processed sample produced, shown in
These experiments were performed to examine the effect of magnetism on the electrosorption process. Phase separation was obtained using a spinning magnetic stirrer. Under the conditions tested, the phase separation occurred after a long time, and no specific benefit was observed using a magnet. However, conductivity increase, as shown in Tables 13 and 14 (among others) showed shorter phase separation periods.
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
A series of experiments were designed and performed in order to test capacitance-based separation using reduced cross-sectional area. The following tables provide experimental set-up and processing conditions of a series of tests which were performed. Experimental observations for each test are provided, along with accompanying figure(s) depicting experimental setup and processed samples produced.
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
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Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
Experimental setup, and processed sample produced, shown in
FAME (Fatty Acid Methyl Ester) analysis experiments were performed to assess lipid extracts and dried algal biomass products produced according to methods described herein (see Example 5).
The following table (Table 32) provides results of FAME analysis of 4 samples: CV2 Biomass, CN2 Biomass, CV2 Lipid, and CN1 Lipid. Experimental protocol is provided in Example 5. Two biomass samples (CN2 and CV2) from the 1500 psi and 18 psi experimental runs in Example 5 were submitted for spectroscopic analysis and 1 lipid sample from the 18 psi run (CN1) was also analyzed. Lipids were extracted from CV2 biomass with solvents using modified Bligh and Dwyer method and then analyzed as shown in Table 32.
Materials and Methods
Experimental Protocol
Direct trans-esterification-saponification by NaOH followed by BF3-catalyzed methylation was performed. Protocol was as follows:
Where AX=area counts of EPA or DHA; AIS=area counts of internal standard (tricosylic acid methyl ester), CFX=theoretical detector correlation factor for EPA or DHA (0.99 for EPA, 0.97 for DHA); WIS=weight of IS added to sample in mg; WS=sample weight in mg; and 1.04 is factor necessary to express result as mg fatty acid/g sample.
The weight of the rest of the fatty acids were also calculated using the same formula as described above, assuming that all fatty acids regardless of the structure have the same response as the internal standard (i.e. theoretical detector correlation factor is equal to 1).
Reference: AOAC official method 991.39. Fatty acids in encapsulated fish oils and fish oil methyl and ethyl esters. Gas chromatography methods.
Two high pressure tests (1500 psi) were performed, and in both tests no changes occurred after 30 min and 60 min settling periods (i.e. no separation was seen in collection tanks located at the top of the vertical system). During the low pressure tests, a previous batch of C. sorokiniana showed very clear separation in the collection vessel. See Example 6 for experimental protocol details. The high and low pressure experiments performed at 1500 psi and at 18 psi described are the “1” and “2” samples reported in Table 32.
Experimental Protocol:
Algal culture (Chlorella vulgaris) was received from Symbiotic Algae Inc. The received culture was obtained nutrient-depleted and with a low conductivity of 680 uS/m and was not stressed during operation to produce lipids. To find out the dry content of wet algae, 2.0 g of wet algae was dried in an oven overnight at 105° C. and the dry content was calculated. Multiple tests were performed using 400 ml (lab scale) to 20 L batches (pilot scale) in the electrosorptive cavitation system under low to medium to high pressure cavitation (18 psi, 250 psi, 800 psi and 1100 psi). The system is connected to an AC power input (36 V, 10 amps) that serves to enhance the advanced oxidation generated by cavitating nuclei and results in lipid-biomass-water phase separation through lipid-bubble interactions and reduced polarity of the algal cells rendering their effective settling in a single step. There are several experiments carried out to validate the developed system from laboratory scale to pilot scales.
In certain embodiments, electrosorptive cavitation may be a continuous process and may be further designed to operate in a single step without the addition of added chemicals, flocculants, adsorbents, or pH buffer agents beyond the nutrients supplied to the culture during the algal growth in photobioreactors. Electrosorptive cavitation process may include a batch/continuous electrosorptive-cavitating flow system to perform both extraction and separation processes by applying a complex cavitating flow which applies a high pressure to a tangential flow inlet.
A summary showing differences between low and high pressure electrosorptive cavitation is benchmarked against a system with electrosorption only:
Chlorella vulgaris with
Chlorella vulgaris with
Chlorella vulgaris with
Chlorella vulgaris with
Additional experiments testing treatment of algal culture were performed. Algal culture (Chlorella vulgaris) was tested. The culture was nutrient depleted, and was reported with a low conductivity of 680 μS/m and was not stressed during operation to produce lipids. Two pails of samples were brownish in color, with a distinct odour of degradation. It can be inferred that the samples may have partially degraded due to storage time and/or temperature.
Multiple tests were performed using 20 L batches and electrosorptive cavitation treatment. Results are shown below for both low and high pressure cavitation. Algae cells were analyzed using a microscope and were observed to be between 2 and 7 microns in size. The culture was separated and water samples and both culture and water samples are prepared for spectroscopic analysis. The conditions of operation and collected results are summarized in the following
Tables and Figures.
Chlorella vulgaris algae
Experimental setup, and processed sample produced, shown in
Chlorella vulgaris algae with nutrient
Experimental setup, and processed sample produced, shown in
Chlorella vulgaris algae with nutrient
Experimental setup, and processed sample produced, shown in
Chlorella vulgaris algae with
Experimental setup, and processed sample produced, shown in
Chlorella vulgaris algae with
Experimental setup, and processed sample produced, shown in
Chlorella vulgaris algae with
Experimental setup, and processed sample produced, shown in
Experiments were performed with mine water, and metals separation was assessed following treatment. The experimental results demonstrated a significant reduction in metals content in the water.
Mine affected water was subjected to electrosorptive cavitation in a laboratory scale system. Mine affected water, rich in aluminium, iron and sulphate was batch tested with electrosorptive cavitation in the system described earlier for algae-water-lipid extraction and phase separation.
During the test, 20 L of mine water was subjected to electrosorptive cavitation and samples were collected for ICP analysis. ICP results are shown below:
1. Extraction of Lipids from Chlorella sorokiniana
Chlorella sorokiniana samples treated by cavitation demonstrated an increasing trend of crude lipid recovery relative to biomass loading, approaching 50% recovery in the lipid fraction at 0.1 wt % dry solids biomass loading. Results are shown below in Table 40, and in
2. Conductivity Analysis of Different Algal Cultures
Results are shown below in Table 41. With the exception of C. vulgaris, the culture conductivity generally increased following ultrasound treatment compared to untreated samples, indicating the release of polar intracellular components.
Botryococcus #66-02
Chlorella vulgaris #208-01
Chlorella sorokiniana #282-02
Scenedesmus sp. #173-13
Soybean oil, a high viscosity liquid, was subjected to cavitation and did not demonstrate a significant change using either low or high frequency cavitation. 200 mL samples were treated with varying times and duty cycles at varying frequency at 4/6 amplitude. Viscosity was recorded pre and post-treatment. Results are shown below in Table 42.
As a slight change was observed in the case of lower frequency operations, electrosorptive cavitation at higher flow rates may allow for a higher removal efficiency.
Dispersions were prepared in 20 L BBM/tap water at 720 μS and used for two runs at low/high pressure. Lipids accumulated in the collections float cell were skimmed along with the biomass with clear high conductivity water without biomass in the continuous operation. Due to lipid bubble attachment, the cells were found to be trapped in the interstitial spaces between the lipid-bubble generated froth. To overcome this separation issue, in the last trials, collected foam was broken in a sieve, centrifuged, and the top foam layer collected by aspiration for CHCl3 extraction to achieve better separation with minimal water present. Solids separated by centrifugation were freeze-dried to determine the final dry biomass to establish stoichiometry. Results are shown below in Table 43.
Botryococcus
Botryococcus
During the operation, the electrosorptive system was operated at 30V DC and 10 A to obtain clear water flow without any lipids or biomass.
During this study, the focus was on determining the technology potential for low lipid yielding algae and to compare the potential of the electrosorptive cavitation method of the present application (eCav) to electrosorption or cavitation independently. Lipid extraction recovery was greater following treatment, and conductivity also increased indicating lipid release.
Untreated samples were compared to cavitation, 5 min 36 V electrosorption, and electrosorptive cavitation treatment. Micrographs of treatments (
Results:
Biomass yield was nearly 2× for electrosorption treatment as compared to untreated samples or treatment by cavitation alone, and was similar to electrosorptive cavitation, where the precipitates of the ionic species were not observed. Supernatants following centrifugation after electrosorption were much clearer than untreated samples or those treated by cavitation alone. Micrographs (
Due to the brackish nature of the growth media, the system is subjected to other contaminants and the precipitation of the ionic species is critical and can be represented by reduced conductivity.
Electrosorptive cavitation conductivity decrease is substantially higher than cavitation as the advanced oxidative process initiated during cavitation is further enhanced by the immediate initiation of electrosorption, an advanced oxidation process that does not release lipids but the initiated cavitation voids propagate further energy dissipation and resulting added lipid due other than promoting agglomeration of algal cells. Thus, an indication of the benefits of electrosorptive cavitation is provided through the higher conductivity and pH within the solution. To confirm the findings, the micrographs shown in
1. Development of an Optimum Condition for Selenium Removal from Coal Mine Affected Waters
A range of advanced oxidation treatment methods were applied in addition to electrosorptive cavitation on coal mine waters to determine the removal efficiency. Ultrasound based methods are limited for large scale mine waters. The objective of this work was to develop an approach to address high volume (throughput) treatment to remove selenium from coal mining affected waters.
Modified coal mining effluent water with initial pH 7.68. Different experimental conditions as below:
The selenium concentration was measured by using UV-Vis spectrophotometry after each treatment. The tests were repeated three times. The results were compared with the blank solutions with known concentration of selenium. All the results obtained by UV-Vis were compared with ICP-MS results for validation of the method. The UV-Vis spectra of sample analysis are presented in
Tuning of Cavitation System: Using the above conditions, cavitation in the electrosorptive cavitation system was operated at a reduced pressure to only form incipient cavities.
2. Gold Mine Process Water Treatment
i. Selenium Removal
A sample of gold mine processing water, sample CAV-S2, was obtained from a gold refining operation. Treatment was focused on selenium removal only. As seen below in Table 46, substantial reduction of selenium from the original mine water (at a concentration of Se=1 ppm) to 0.369 ppm was achieved through this treatment. Results for samples CAV-S10, CAV-S11 AND CAV-S12 show the effects of change in cavitation pressure on selenium removal in the electrosorptive cavitation system.
i. Salt Removal
Treatment of gold mining and extraction waters that are not selenium rich necessarily contain contaminants, such as salt and copper. Table 47 shows the salt and copper removal efficiency at incipient cavitation conditions of 250 psi and electrosorption operation a 30 V and 10 A.
To demonstrate that the two processes involved in the present apparatus and method cannot be de-coupled with equal results, the electrosorptive cavitation equipment was operated (i) as a continuous electrosorptive cavitation process, and (ii) as 2 different process stages with an intermediate tank after cavitation that was pumped at the same flow rate using a separate pump into the electrosorptive process stage.
An aqueous feed consisting of Botryococcus braunii culture dispersed at 0.5 g/L in basal mineral media with conductivity of 720 μS was subjected to 2 different configurations 1. Electrosorptive cavitation and subjected to low pressure cavitation at 300 psi fed directly into the electrosorptive system at 36 VDC/10 A without additional residence time and 2. The same culture was subjected to low pressure cavitation and the cavitation outlet flow was collected in a reservoir and then pumped into the electrosorption system An aqueous feed consisting of Botryococcus culture dispersed at 0.5 g/L in basal mineral media with conductivity of 720 μS was subjected to cavitation through a nozzle at 300 psi, and directly fed into a column containing steel coil and aluminum rod electrodes at 36 VDC/10 A for electrosorption.
To compare the effect of separate cavitation and electrosorption treatments in sequence, the feed was also run through the cavitation nozzle followed by a resting period of 5 minutes, to allow dissipation of generated cavitation bubbles prior to electrosorption. It was then passed through the electrode column at the same flow rate used in the integrated cavitation-electrosorption experiment, producing similar residence times in each treatment but removing any synergistic effects caused by the presence of active cavitation bubbles during electrosorption with a 5 minute residence time in the process.
Photographs of the samples, micrographs of the biomass, and optical density measurements were taken and are shown in Table 48 below and in
Optical density measurements were reduced by approximately 50% relative to the feed, indicating removal of biomass from the dispersion.
Gold mine effluent water with a high turbidity of 5.4 was subjected to electrosorptive cavitation (e-Cav) and the water quality is reported below in Table 48. Assays performed to determine metals content before and after e-Cav show that there is a significant reduction in sodium (reduced by ˜45%). This indicates that the process can be applied for de-salting applications from mine water effluents.
To examine the impact of lower feed turbidity on the same mine affected water, pre-treated samples with reduced turbidity were subjected to the electrosorptive cavitation process. The initial and processed effluent characteristics are shown below in Table 49.
The e-Cav process shows a reduction in metals with a significant reduction in selenium—a hard to remove contaminant.
The selenium extraction results described herein were further benchmarked with a best available technology—ion exchange process.
To compare the performance of ion exchange vs. electrosorptive cavitation, the same water sample was run through the e-Cav system and the effluent selenium concentration was determined to be 8 ppb consistently for over 100 bed volumes (equivalent).
Benchmarking of the process with the same metallurgical coal affected mine water was also performed using a speciality oxy-anion adsorbent. (See
One or more illustrative embodiments have been described by way of example. It will be understood to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.
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| PCT/CA2018/050299 | 3/13/2018 | WO |
| Publishing Document | Publishing Date | Country | Kind |
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| WO2018/165750 | 9/20/2018 | WO | A |
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