The present invention pertains to an induced cavitation mixing and separation apparatus and system for mixing and breaking up waxes and solid masses in heterogeneous mixtures in a pressure controlled environment.
The process of dewaxing, or removing fats and waxes from crude oil plant extracts, is also called winterization. Dewaxing or winterization traditionally involves using a combination of organic solvents and controlled cooling to facilitate fat and wax separation from material soluble in the liquid solvent. In traditional winterization, ethanol or another organic solvent requires distillation to obtain the desirable soluble oil. The distillation and removal of organic solvent from the desired oil can be a complex and lengthy process depending on the purity level required.
Carbon dioxide (CO2) fluid extraction, separation, and purification, is becoming an important commercial and industrial process due to the usability of CO2 in chemical separation in addition to its low toxicity, non-flammability, low cost, and low environmental impact. The relatively low temperature of the process and the stability of CO2 also allows many compounds to be extracted with little damage or denaturing. In addition, the solubility of many extracted compounds in CO2 varies with pressure, permitting selective separations. Carbon dioxide behaves as a gas in air at standard temperature and pressure (STP), and its physical state can be tuned by controlling temperature and pressure in a closed system or closed environment. CO2 extraction can be used, for example, for analytical purposes, decaffeination or component removal from a plant material, in winterization to separate fats and waxes from plant extracts, and for separating and collecting desired products from plant products such as terpenes and essential oils. Compared to other forms of extraction and separation, the use of carbon dioxide is also advantageous because the CO2 solvent can be easily separated from the extract by evaporation. By using liquid CO2 as the solvent in winterization, the solvent separation process is simplified, as CO2 evaporates at a much lower temperature than the compounds of interest and therefore can be easily evaporated by raising the temperature or lowering the pressure of the mixture.
In closed systems and in pressure controlled environments where CO2 is held at conditions in or around the critical point or saturation line, such as in a subcritical extraction, both liquid and vapour CO2 can exist simultaneously in the system. In these types of pressurized closed systems, integrated mechanical mixing can be challenging due to the extreme and sealed conditions inside the vessel and system. In one example of a system for collecting particles using high pressure supercritical fluid processing, U.S. Pat. No. 9,925,512 to Johnson et al. describes a filtration system for processing particles suspended in supercritical fluid, optionally using a vibrating member or mesh.
Powered ultrasonic mixers are used to apply sound energy in ultrasonic frequencies (>20 kHz) to agitate particles in a sample for various purposes such as the extraction of multiple compounds from plants, microalgae and seaweeds, and to break up larger aggregates or emulsify fluids. Sonication can be used, for example, for the production of nanoparticles, such as nano-emulsions, nanocrystals, liposomes and wax emulsions, as well as for treating wastewater, degassing, extraction of polysaccharides and oil from biological materials, extraction of anthocyanins and antioxidants, petroleum processing such as in crude oil desulfurization and cracking, production of biofuels, cell disruption, polymer and epoxy processing, adhesive thinning, and many other processes. Sonication has also been used widely in various industrial processes such as in the production of pharmaceuticals, cosmetics, ink, paint, coating, nanocomposites, pesticides, fuels, and food, as well as in water treatment, wood treatment, metalworking, and many other industries. Ultrasonic mixing can also potentially lower processing costs in industrial processes by speeding up mixing and chemical processes.
In practice, ultrasonic waves travel as a successive series of compressions and rarefactions along the direction of wave propagation through the liquid medium. Ultrasonic mixers or sonicators produce and propagate these sound waves through a solvent or fluid medium. Liquids can be treated by creating ultrasonic waves, such as with an elongate ultrasonic horn moving longitudinally in the mixing vessel to create longitudinal mechanical waves inducing pressure variations which generates lower pressure cavitation bubbles as they transmit through a liquid medium. Other devices are also known that create cavitation bubbles by inducing pressure variations in a liquid, such as various types of shear mixers. During ultrasonic mixing, a tiny cavity is created and is filled with vapor from the liquid solvent when the attraction forces between the liquid molecules became weaker and less than the negative pressure of the cyclic rarefaction. Cavitation occurs when the pressure in a location decreases below the vapour pressure of the liquid solvent, forming an acoustic cavitation bubble of gaseous solvent. Once the local pressure returns to the vapour pressure of the liquid solvent, the cavitation bubble collapses back to liquid form. The cavitation or collapse of these low pressure microbubbles transform applied pressure into mechanical energy upon collapse by creating pressure shocks from bubble collapses, sending out local shock waves, which can cause breakup of local particulate and emulsification.
In high pressure closed vessel separations, one challenge in using cavitation technology is that pressures on the cavitation inducing device inside the vessel in the use of high frequency vibrations in combination with high vessel pressure can vibrate the vessel and cause undue stress in the system. In one example, U.S. Pat. No. 7,762,715 to Gordon et al. describes a device for processing petroleum crude oil in a flow-through hydrodynamic cavitation apparatus with channels to create cavitation by way of directing fluid pressure and fluid flow. By forcing fluids into the flow-through hydrodynamic cavitation apparatus, chemical reactions and/or changes physical properties of the fluid are induced to change the physical properties of the crude oil.
In high pressure systems such as those required to maintain CO2 in a liquid state, the solvent needs to be maintained at relatively high pressures, which creates a challenge for powered ultrasonic and cavitation inducing mixers where the transducer or motor is located outside of the mixing vessel. There remains a need for an induced cavitation mixing apparatus capable of operating at subcritical fluid solvent conditions.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.
An object of the present invention is to provide an induced cavitation mixing apparatus for mixing and breaking up waxes and solid masses in heterogeneous mixtures in a pressure controlled environment. Also provided is a device, system and method for mixing of components of a pressure controlled closed environment.
In an aspect there is provided a cavitation mixing apparatus comprising: a cavitation mixing vessel comprising a material inlet and a discharge outlet, the cavitation mixing vessel capable of containing pressurized liquid CO2; a cavitation inducing device mounted inside the cavitation mixing vessel; an electrical connection for connecting the cavitation inducing device to a power supply through the cavitation mixing vessel; and a cavitation mixer mount for mounting the cavitation inducing device inside the cavitation mixing vessel, the cavitation mixer mount comprising at least one fluid channel for equalizing pressure of CO2 around the cavitation mixer inside the cavitation mixing vessel.
In one embodiment of the apparatus, the cavitation inducing device is an ultrasonic mixer.
In another embodiment of the apparatus, the ultrasonic mixer has a frequency of at least 20 KHz.
In another embodiment of the apparatus, the ultrasonic mixer produces an ultrasonic vibration at a frequency of between 20 KHz to 1.0 MHz.
In another embodiment of the apparatus, the cavitation inducing device is a high shear cavitation mixer.
In another embodiment, the apparatus further comprises an injection tube to direct crude oil proximate the cavitation inducing device.
In another embodiment of the apparatus, the cavitation mixer mount comprises a plurality of fluid channels.
In another aspect there is provided a cavitation dewaxing system comprising: a carbon dioxide reservoir for containing liquid carbon dioxide; a cavitation mixing vessel comprising an encapsulated cavitation inducing device; a separation vessel; and an evaporation vessel.
In one embodiment of the system, the cavitation inducing device is an ultrasonic mixer.
In another embodiment of the system, the cavitation inducing device is a high shear cavitation mixer.
In another embodiment, the system further comprises a carbon dioxide condenser.
In another embodiment of the system, the separation vessel comprises a filter.
In another embodiment, the system is a passive circulation system.
In another aspect there is provided a method of separating oils from a crude plant oil mixture, the method comprising: injecting crude plant oil into a mixing vessel comprising pressurized liquid carbon dioxide; and mixing the crude oil with the liquid carbon dioxide under pressure using by powered induced cavitation, the cavitation mixing vessel comprising an encapsulated cavitation inducing device.
In one embodiment of the method, the induced cavitation is provided by an ultrasonic mixer.
In another embodiment of the method, the induced cavitation is provided by a high shear mixer.
In another embodiment of the method, the pressure of liquid carbon dioxide in the mixing vessel is 80 to 15,000 psi.
In another embodiment of the method, the method is in a batch, semi-continuous, or continuous industrial process.
In another embodiment, the method further comprises filtering the crude oil and liquid carbon dioxide mixture, and evaporating off the carbon dioxide to isolate a purified plant oil.
For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:
Unless defined otherwise, 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.
As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.
The term “comprising” as used herein will be understood to mean that the list following is non-exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s) and/or element(s) as appropriate.
As used herein, the term “closed system” refers to an enclosed environment which limits material flow with the environment and where temperature and pressure are controlled. In a closed system, pressure is maintained in a controlled environment by limiting and controlling material and solvent influx and outflow and keeping the system largely closed from the external environment. In application, in systems that use CO2 as a solvent, this means maintaining the system above a pressure that enables stabilization of liquid CO2.
As used herein, the term “subcritical” refers to a physical state of a fluid wherein the fluid can exists as gas or vapour, liquid, or combination of both vapour and liquid. Subcritical fluids are fluids which are compressed below their critical temperatures, yet kept in the liquid state and used above their boiling points with the use of pressure. Subcritical fluid states vary along a range of temperatures and pressures and are unique to each fluid, which includes solvents, liquids, and the same with dissolved and/or emulsified materials therein. Subcritical conditions for CO2 are shown in
As used herein, the term “closed,” as it refers to a system or apparatus, refers to one or more connected vessels that are sealed to the environment. Such systems can optionally be pressurized and are sufficiently sealed such that they can retain an internal pressure, or can contain a solvent from evaporation or leak outside of the system. Closed systems are particularly useful for maintaining increased pressures with pressurized solvents.
As used herein, the term “induced cavitation” refers to cavitation applied to a fluid where the cavitation is created by a powered device. This is in contrast to passive cavitation which can be caused by structural features as a result of fluid flow, such as, for example, barriers or obstacles such as fins, filters, meshes, and the like.
Herein is described a cavitation mixing system and induced cavitation mixing apparatus capable of operating at subcritical solvent conditions in a pressure controlled environment. The present system and apparatus can be used for winterization and dewaxing of plant materials, as well as other industrial and chemical processes that benefit from cavitation mixing in a closed environment, particularly those which operate in subcritical solvent conditions in closed systems. By inputting cavitation energy into a closed, induced cavitation mixing vessel, solvent and solute mixtures can benefit from cavitation mixing in a pressurizable closed environment in batch, semi-continuous, or continuous industrial processes. The presently described induced cavitation mixer or mixing apparatus is operable at subcritical conditions and can be used in closed systems and pressure controlled environments.
Cavitation involves the phenomenon of vapor bubble formation in the solvent fluid experiencing reduced pressure, which is followed by violent bubble collapse. The phenomenon is named cavitation because cavities form when the fluid pressure has been reduced to the vapor pressure of its constituent(s), in this case liquid carbon dioxide. The vapor bubbles expand as they move and suddenly collapse. The violent collapse causes sudden, localized increases in temperature and pressure, as well as tiny but powerful micro jets which hold an enormous amount of kinetic energy and cause physical damage to circulating crude oil and wax particulate, breaking apart the particulate. Particulate disruption caused by the cavitation improves access of the solvent to desirable oils inside the wax particulate and increases the yield from extractive and separative processes.
The present apparatus and separation vessel with integrated induced cavitation mixing device are compatible with the high pressures required for subcritical fluid dewaxing and separation, as well as other processes that benefit from induced cavitation in closed system mixing in a pressure controlled environment. A commonly used subcritical solvent is liquid carbon dioxide, however it is understood that other solvents may be used, as well as combinations of solvents with and without CO2. Carbon dioxide will be referred to herein as an example solvent, however it is understood that the presently described devices, apparatus and methods can be used with any subcritical fluid, or any solvent or industrial mixing process done in a closed or pressure-controlled environment. The present apparatus can also be used in standard or atmospheric solvent conditions and under other temperatures and pressures where solvent is retained inside a closed vessel system or in a closed process.
The critical point of CO2 is easily accessible as it has a critical temperature of 31° C. and critical pressure 73.9 bar (72.9 atm). Above the critical point CO2 behaves as a supercritical fluid above its critical temperature (304.25 K, 31.10° C., 87.98° F.) and critical pressure (72.9 atm, 7.39 MPa, 1,071 psi, 73.9 bar). Subcritical solvents are of interest when extracting yields with increased volumes of terpenoids, flavonoids, and other such volatile plant materials at least because subcritical carbon dioxide runs at milder separation parameters than other solvents, targeting those volatile compounds. Through only modest changes in the temperature and pressure, the physical properties of CO2 can be manipulated. CO2 can be a stable liquid from about 80 psi and roughly −57° C. which would prove a very low pressure extraction with very low solubility, however the pressure of CO2 can be increased so long as the process stays below 31° C., which is the critical temperature limit.
The solvent power of subcritical fluids is dependent on the temperature utilized and temperature helps to increase solvency. In contrast, pressure is used to help retain the liquid state of the fluid. Subcritical separations at low temperature and low pressure take more time than superfluid separations, but they can be used effectively to retain the essential oils terpenes and other sensitive chemicals within the plant. Subcritical CO2 separation is often preferred because the milder conditions result in production of a lighter colored extract, fewer waxes, and resins, and retention of more volatile oils. Subcritical separation can also be used effectively to scrub the extractant matrix of any valuable compounds and achieve a full-spectrum extraction. In any closed system with controlled pressure, embedded mixing systems can improve extraction efficiency as well as product yield and purity by improving in situ mixing.
The CO2 solvent is supplied to the cavitation dewaxing assembly from fluid reservoir 102 to cavitation mixing vessel 104, optionally with the use of a fluid pump. The assembly can also be set up as a passive circulation system using only fluid flow through temperature control, and the optional addition of a pump can be used with either liquid (cooling and pumping) or vapor recovery (compressing and cooling), and could be added in different positions on the process flow. The fluid reservoir 102 holds the fluid solvent at a temperature and pressure to maintain the subcritical fluid properties of the solvent. Preferably the subcritical fluid is saturated liquid CO2. The CO2 reservoir can be further chilled via a refrigerated jacket to maintain CO2 in a liquid phase. The assembly can further comprise a working fluid accumulator which can also be used to store liquid/gas subcritical working fluid. Working fluid is the general term of circulating fluid which is being used as a solvent in the extraction or separation process. In the present system the preferred working fluid is CO2, optionally mixed with a co-solvent which stay in a liquid phase through the process. Some optional co-solvents include ethanol, methanol, hexane, heptane, propane, butane, and combinations thereof. Co-solvents may be used in ratios from 0 parts to 100:1 (co-solvent:input material) with a total solvent ratio from 1:1 to 100:1 (solvent solution:oils). Multiple injection nozzles may also be provided in the system for one or more additional oils and/or co-solvent injection into the system. The flow rate of CO2 through the system and control of the flow rate can be passive by controlling the rate of evaporation, or active by pumping such as by controlling the flow of liquid inlet, or both. A high pressure multi-phase pump can also handle subcritical fluid solvents by enabling both the compression of gasses and/or the pumping of a fluid. Any pump known to the skilled person useful in subcritical fluid systems may be used, such as, for example, a liquid pump optionally in combination with one or more suitable compressor. An optional cross flow heat exchanger can also be used to control the temperature of CO2 as required. From the fluid reservoir 102, CO2 is provided to cavitation mixing vessel 104 where temperature and pressure conditions are adjusted to the desired conditions to maintain a balance of liquid and gas CO2 in the vessel. Following emulsification the solution travels into the separation/filter vessel 106 where the density of CO2 can be controlled by adjusting the temperature to promote density separation of compounds. For example in isobaric condition of 500 psi CO2 has a density from 1.08 g/ml @−30C to 0.94 g/ml @−2C, as shown in
The separation/filter vessel 106 is preferably located below the cavitation mixing vessel 104 such that the separation/filter vessel 106 can be gravity-assisted to fill completely with the mixed CO2/extract mixture from the cavitation mixing vessel 104. The separation/filter vessel 106 can also be cooled by a refrigerated jacket. In the assembly shown, the oil/extract mixture is gravity fed into the top of the separation/filter vessel 106 in such a way as to cause as little agitation inside the separation vessel as possible. The separation/filter vessel 106 will begin to accumulate the solidified fats and waxes near the top as the oils and waxes separate from the CO2 mixture due to low temperatures. A separation vessel inlet tube 126 on the inlet of separation/filter vessel 106 allows incoming CO2/extract mixture from the cavitation mixing vessel 104 to pass through any oil layer in the separation/filter vessel 106 without excessive agitation. A filter element 130 at the bottom of the separation/filter vessel 106, optionally sintered and/or made from stainless steel, can prevent fats and waxes from exiting the vessel while allowing the remaining CO2 mixture with desired compounds for collection (minus the fats and waxes) through. An evaporation vessel inlet tube 124 on the evaporation vessel 108 is preferably located at the same height as the separation vessel inlet. A high purity gas filter can also be integrated into the system assembly as a variety of locations as needed. In particular, a coalescing high purity gas filter can be used to scrub any leftover compounds and water vapor from the gas stream. Other optional components which can be integrated into the assembly can include one or more of a condensing heat exchanger, an air cooled process chiller to cool accumulator and/or condenser, an air compressor, and a hot water circulating system for the heat exchanger.
The system assembly can also optionally have an electronic control system having circuitry, hardware, and software for controlling and reporting one or more of: inputting batch parameters; separation tracking; monitoring and recording system parameters at defined intervals; printing batch records with associated pressures and temperatures; controlling separation parameters based on user input to adjust pressure, temperature, flow, or other process parameters; initiating cleaning cycles; detecting system failures; initiating emergency shutdown procedures; and connecting to one or more networks for monitoring and reporting. The electronic control system can comprise one or more microcontrollers connected wired or wirelessly to one or more sensors, the one or more sensors for detecting, for example, pressure, temperature, fluid flow, and other fluid properties such as colour, viscosity, turbidity, and other properties. The assembly can further comprise one or more shunts or valves which can direct small amounts of process fluid to sensor or analytical devices to test, monitor, and control aspects of the separation/extraction, optionally providing feedback information to the system to change one or more physical parameters of the process. In one example, the operation of the cavitation mixer in the separation/filter vessel 106 can be adjusted to increase or decrease speed or frequency to provide optimal cavitation for the material being processed. Other physical parameters that can be controlled using the control system include but are not limited to pressure, temperature, fluid flow rates. In addition, the separation system can further comprise one or more electric heaters, electric motor controls, emergency stop circuitry, or automatic closure of an accumulator tank, and automatic switching of process valves, all of which can be optionally monitored and controlled by the control system. An in situ measurement device can also be used for determining the completion and real time separation rate of the extracted material, in one example, of dissolved plant extracts and cannabinoids. The system or assembly itself can be integrated directly into a CO2 extraction process, where the input material is the extraction collection material.
Cavitation mixer 202 shown comprises a piezoelectric transducer 204 connected to an electrical power source to generate an ultrasonic vibration, which is transferred to an optional sonotrode booster 208 connected to sonication horn 206 with horn end 210. Piezoelectric transducer 204 is joined to the horn 210 optionally through a vibration transmitting block or sonotrode booster 208, which is used to amplify the vibration amplitude generated by the transducer 204, as the vibration amplitude of the transducer itself is sometimes not sufficient for mixing in many industrial processes. The optional sonotrode booster 208 can thereby provide an acoustic gain to the ultrasonic vibrations. The sonication horn 206 can have a variety of shapes and sizes, and can be conical, straight, or barbell shaped as desired. The horn end 210 configuration can be variable in size, cross-sectional shape, and surface area and can be pointed, flat, rounded, and have a variety of cross-sectional areas and shapes. The booster, horn, or both can also clad or plated with a reflective material that reflects ultrasonic vibrations or lessens loss of ultrasonic energy being transmitted to the horn.
The cavitation mixing vessel 200 accepts a metered amount of raw plant oils and waxes, also referred to as crude oil, through material inlet 222 with optional extended injection tube 244 and uses a cavitation mixer attachment to combine the extract with incoming clean CO2 fed through solvent inlet 212 from the CO2 reservoir. Homogeneous discharge outlet 214 just below the fluid interface 230 directs CO2 solvent mixed with cavitation-treated and solubilized or emulsified oils and waxes out of the cavitation mixing vessel 200. The cavitation mixing vessel 200 is cooled through a refrigerated jacket and cooling jacket 224 with cooling jacket port 226 to maintain the liquid phase of CO2 inside the vessel and to extract the heat input from the cavitation mixing vessel 200. The raw oil in the plant extract benefits from thorough mixing provided by cavitation to separate the fats and waxes from the desired compounds. The mixing time and amount in a continuous feed process can be controlled by the injection rate of the raw extract into the cavitation mixing vessel 200 and the injection rate of clean solvent through solvent inlet 212. The end surface of the induced cavitation device or cavitation mixer 202 is preferably positioned in a location within the effective zone of cavitation below the fluid interface 230 as initiated by the mixing device relative to the injection tube 244 such that crude oil is directed in the immediate vicinity of the horn end 210 of cavitation mixer 202. The liquid flow path inside the vessel is such that the entering liquid and crude oil strikes the end of the horn at a direction normal to the horn end 210, then flows across the surface of the horn before leaving the cavitation mixing vessel 200. The cavitation mixing vessel 200 has a high pressure electrical pass through fitting 216 for supplying power to the induced cavitation mixer 202, and adjacent pressure safety valve 218 and pressure sensor 220. The ultrasonic energy generated by the sonotrode can have a frequency in the range of, for example, 20 KHz to 1.0 MHz, or preferably from 20 KHz to 70 KHz. The frequency of the current is chosen to be the resonant frequency of the tool, so the entire sonotrode acts as a half-wavelength resonator, vibrating lengthwise with standing waves at its resonant frequency. The amplitude of sonotrode vibration is generally small, ranging from about 13 to 130 micrometres.
All publications, patents and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
This application claims priority to United States provisional patent application U.S. 62/788,038 filed 3 Jan. 2019, the contents of which are hereby incorporated by reference herein in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/CA2020/050001 | 1/2/2020 | WO | 00 |
Number | Date | Country | |
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62788038 | Jan 2019 | US |