Apparatus and method for free fall electrostatic separation of glandular trichomes

Abstract

An apparatus for electrostatic separation of glandular trichomes from plant biomass, comprising a dispenser, a vibrating sifter or hopper (1), a free-fall separation chamber with oppositely charged metal electrodes (4) and a DC power source for applying a voltage to the electrodes.

Description

FIELD OF INVENTION

[0001] This invention relates to a method and apparatus for the free fall electrostatic separation of glandular trichomes from a plant biomass.BACKGROUND OF INVENTION

[0002] Glandular trichomes (further "trichomes") are specialized hair-like structures on the surface of certain plants, primarily serving protecting and metabolic roles, such as protection against herbivores and pathogens, temperature and water control, and pollinator attraction. In this regard, the function of the glandular trichomes is to secrete and store complex secondary metabolites and phytochemicals (e.g., terpenoids, phenylpropanoids, flavonoids, etc.) via secretory cells. As such, and as a result of natural biological processes, trichome heads accumulate and contain large amounts of biological compounds which have widespread therapeutic, pharmaceutical, and nutraceutical applications. In order to concentrate these biological compounds, the trichomes must be separated from plant biomass.

[0003] Prior art describes wet and dry methods of trichome separation. A dry one is preferable for saving the integrity of water-soluble biological compounds. Dry separation is based on the differences in mechanical properties of trichomes and plant biomass. Usually, it includes mechanical separation by using frictional, centrifugal and gravitational forces or their combination.

[0004] One method of dry separation is screening the dried plant powder, containing a mixture of trichomes and plant biomass to screen out glandular trichomes (US Patent 10,512,938 B2, 2019). This method uses the difference in density of trichome heads and plant biomass. The disadvantage of this method is that it is extremely sensitive to operating parameters such as temperature, humidity, and particle size. The deviation from optimal conditions causes a loss of yield or product purity.

[0005] Another dry separation method, so-called "static tech", is based on triboelectric charging due to the mechanical rubbing of dry plant powder on the sifting screen. Due to the different chemical compositions, the plant biomass and trichomes are getting different charges, which allows the hand-pick collection of trichome heads with vinyl gloves or parchment paper. However, this method is not scalable, labour-intensive, and requires trained personnel to achieve the desired quality and purity of the end product.

[0006] Yet another method of dry separation is based on the electrostatic separation of trichomes from a sample of plant biomass (EP4549025A1). The method and apparatus for electrostatic separation include a dispenser, pipeline, injector and separation chamber. The principle of separation is based on the difference in mechanical and electrical properties of trichomes and plant biomass. In this method, powdered plant biomass with trichomes is pneumatically supplied to a pipeline and injected into a separation chamber at the linear velocity of 1.5-1.9 m / s. At this speed, the mechanical force acting on particles exceeds the electric force, which decreases the efficiency of electrostatic separation. Also, electrostatic forces between oppositely charged fine particles are stronger than the effect of external electric forces. This creates a problem of clumping particles into clusters, which impedes separation in a static electric field.SUMMARY OF THE INVENTION

[0007] The primary object of this invention is to eliminate the inefficiency of the prior art of electrostatic separation of trichomes by using free-fall separation of finely dispersed particles. A further object of this invention is to provide a new simple and efficient design of an electrostatic separator. A further object of this invention is to provide a solution for controlled declumping of charged particles. These objects are achieved by the subject-matter of the independent claims. Further embodiments can be found in the dependent claims.

[0008] The invention provides a solution for the uniform suspension of particles in air volume between electrodes to increase their exposure to the electric field during settling in the gravitational field. A further object of this invention is to extend the functionality of the principal design, allowing optimization of electrostatic separation based on real-time imaging of the particle distribution.

[0009] The problem of minimizing mechanical force, acting on the particles at the point of injection is addressed by using their free-fall in the gravity field. In free-fall electrostatic separation fine particles are suspended in the air in a diffused state. The principle of free-fall electrostatic separation is based on the difference in particle charge, which determines their free-falling trajectory in the unidirectional electric field. The advantage of free fall over air-forced separation is related to increased residence time in the separation chamber, which improves the separation effect in the external electric field.

[0010] The problem of clumping is addressed by using a vibrating sifter with a fine screen to declump charged particles before feeding them into the separation chamber. The advantage of introducing a sifter is related to the minimization of particle-particle interaction, which improves the separation effect in the external electric field.

[0011] The invention disclosed herein is unique and novel in several ways: (1) Unlike the methods and apparatus described in the prior art, the method according to the invention, includes preliminary declumping of charged particles, which improves their separability in the electric field. (2) The vibrational motion of the sifter / shaker facilitates the mechanical separation of trichome heads from stalks. (3) The steady-state laminar flow of finely dispersed particles before electrostatic separation prevents the secondary clamping of charged particles. (4) The free-falling of finely dispersed particles in a gravity field allows longer residence time and better separation of oppositely charged particles in the electric field. (5) Long vertical electrodes provide prolonged residence time of particles to the electric field and therefore, a better separation effect. (6) Unlike the methods and apparatus described in the prior art, the method according to the invention, improves the quality of electrostatic separation of oppositely charged trichome heads and stalks or other contaminants. (7) Unlike the methods and apparatus described in the prior art, the purity of the end product could be further improved to 99.99% due to the multiple recirculation of separated material through the system. (8) Unlike the methods and apparatus described in the prior art, the method according to the invention, eliminates the need for additional components to achieve a similar result. (9) Unlike the methods and apparatus described in the prior art, the method, according to the invention, eliminates the need for compressed gas to achieve a similar result. This is a significant achievement due to the undesirable effects presented by the use of compressed gas, including the need to dry the gas, the expense of supplying the gas, and because the method promotes light particles to become airborne. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] To complete the description and provide for better understanding of the invention, a drawings is provided. Said drawing illustrates a preferred embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the latter can be carried out.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0013] With reference to FIG 1, a basic electrostatic separation unit according to the embodiments of the technology is presented. FIG 1 illustrates vibrational sifter or hopper 1 and separation chamber 2 with oppositely charged parallel plate rectangular electrodes 4 (longer than wider), connected to the frame of the separation chamber through insulators 3. The dry plant powder with particle size ranging from about 20 to about 300 microns is automatically supplied to vibrating sifter 1. After sifter or hopper 1 finely dispersed particles are introduced into the center of separation chamber 2 by gravity. The laminar flow of the particles into the separation chamber is maintained by the steady-state flow of plant material into the vibrating sifter, controlled by an electronic device.

[0014] Due to the different chemical compositions, plant particles in dry plant biomass have different charges. Trichome heads have a negative charge. During storage, transportation and handling, plant biomass could acquire a positive charge due to the electrostatic induction from negatively charged trichome heads. It results in the mutual attraction of oppositely charged particles and the formation of clusters. This natural phenomenon of clumping particles makes their electrostatic separation difficult.

[0015] Declumping of particles is possible by pre-processing of plant biomass mixture in a vibrating sifter, which would allow mechanical separation of oppositely charged particles and partial separation of trichome heads from stalks, which is usually achieved by mechanical rubbing of dry plant biomass on the sifting screen. Vibrational sifting produces a laminar flow of finely dispersed particles, suspended in the air, which minimizes particle-particle interaction. This cloud of finely dispersed particles is immediately introduced into the electrostatic separator by gravity without disturbing laminar flow.

[0016] Further separation of trichome heads from the plant biomass is based mainly on the difference in their electrostatic charge. Particles are free-falling in the space between two electroconductive plate electrodes 4. The electrodes are oppositely charged by a high-voltage power supply, which provides an electric field depending on the voltage and the distance between electrodes. Both electrodes 4 are insulated using an electrical insulator 3, to prevent the formation of an electrical arc to the grounded metal construction (if in fact optionally metallic) of the separation chamber. Parallel orientation (with an angle of maximum 15 degrees) of electrodes is necessary to create a uniform electric field along the pathway of charged particles. In a free-fall separator electric force dominates over mechanical and gravity forces. This electric force, acting on the particles, results in the attraction of negatively charged particles (trichome heads) to the positively charged electrode, while positively charged particles are attracted to the negatively charged electrode. Uncharged or lost charge particles do not change free-fall trajectory and land in a collection bin.

[0017] [POWER SUPLY] In one embodiment direct current or DC power is used to create an electrostatic field between two electrodes. In another embodiment, the DC voltage is applied at varying pulse widths and pulse frequencies. In one embodiment the shape of the voltage pulses could be square or triangular or sawtooth or a mixture of these. In one embodiment the power source may derive power from the electric grid or solar cell or battery or wind turbine to power the electrostatic separation unit. In one embodiment, the voltage from the power source to the electrodes is controlled using a control unit.

[0018] [CONTROLS] In one embodiment, the flow of dry plant powder into a vibrational sifter is controlled by a regulator. In one embodiment, the flow of dry plant powder into a vibrational sifter is controlled using an airflow regulator. In one embodiment, the flow of dry plant powder is controlled using a vacuum control device. In one embodiment, the flow control devices can be dynamically actuated through electronic means. In one embodiment, the air temperature can be controlled using a temperature-sensing device to a pre-set temperature. In one embodiment, the air humidity can be controlled using a dehumidifying device to a pre-set humidity. In one embodiment, the moisture content of the dry powder is measured by sensors and used for adaptive self-tuning of control variables. In one embodiment, the rate of accumulation of the material on the vibrational sifter is monitored by sensors and used for adaptive self-tuning of the flow rate.

[0019] In one embodiment, the product rate and purity at the output of the system is controlled by controlling the electrical power applied to the unit(s). In one embodiment, the product rate and purity at the output of the system is controlled by controlling the electric field applied across the electrodes in the unit(s). In one embodiment, the product rate and purity at the output of the system is controlled by controlling the flow rate of the dry plant material fed to the module. If the particles dispersion and separation quality is continuously monitored by machine vision, all variables are controlled using a programmed and / or adaptive control system to achieve a desirable flow rate and separation quality.

[0020] In a particular embodiment, controlled dispensing is achieved with a vibrating hopper (with rounded edges and vibrators to prevent agglomeration) of dried or frozen plant biomass (20-300 µm) containing glandular trichomes from trichome-bearing plants (e.g., *Cannabis spp.*). A Steady-state feeding through a straight pipeline (minimizing tribo effects) into a vibrating laminar diffuser (1-60 Hz) mechanically declumps aggregates (essential for enabling separation based on natural charges), detach heads from stalks, and generate a laminar, finely dispersed particle cloud. The gravitational introduction of said cloud into a free-fall electrostatic separation chamber is done without compressed gas, added charging media, or artificial tribocharging. Separation in a uniform electrostatic field (DC or pulsed) between long (>1 m), is achieved by parallel, oppositely charged plate electrodes (width 10-100 cm for scalability), wherein naturally negatively charged trichome heads deflect to the anode, positively charged biomass / stalks to the cathode, and neutrals fall centrally. Real-time monitoring of particle dispersion and trajectories is done via machine vision (e.g., high-speed cameras analyzing deflection angles and flow uniformity). Adaptive control (e.g., PID algorithms) adjusts feed rate, vibration frequency / amplitude, voltage, polarity, and environmental parameters (humidity 10-30% RH, temperature 10-25°C) based on machine vision data to optimize separation efficiency; Self-cleaning of electrodes is done via rotation and non-conductive dielectric scrapers to remove adhered trichomes without downtime. The collection of heads, tails, and middlings fractions is done in a tray. Recirculation of middlings / tails through steps 2-8, with corona discharge electrodes neutralizes induced net charges to prevent re-agglomeration, achieving purity >99.9%.

[0021] [APPLICATIONS] In one embodiment, the separated trichome fraction is used for medicinal and cosmetic purposes. In one embodiment, the separated trichome fraction is used for direct human consumption. In another embodiment, the separated trichome fraction with a purity of 90-95% is used for further purification to 99,99%. In particular, the applications are useful in the pharmaceutical and nutraceutical industry.

[0022] [SCALABILITY] The process can be scaled to produce a highly refined product at a low processing cost. The separation rate can be increased through an increased surface of the electrode system, adjustment of particle flow rate, or a parallel / series combination of basic electrostatic units.Examples

[0023] EXAMPLE 1. Cannabis or other trichome-bearing plants collected from the field were dried to a moisture content of 0.06-0.15 g / g dry matter at a temperature of 15.5 °C. Dried flowers were separated from stems, stalks, and branches using manual or mechanical methods. Dry plant biomass containing glandular trichomes was sifted using a rotary vibrating sieve or similar device with an upper 250-micron stainless steel mesh and a lower 74-micron mesh screen. The result is a powder colloquially known as kief or hash. In a specific use case, the dry powder contains glandular and other types of trichomes, pistils, trichomes stalks, pollen, dirt, and fine particles of plant material with particle size distribution from 10 to 300 microns. The dry powder was further sifted on a 250 and 74-micron screen. With the initial size of glandular trichomes in the range of 74-250 microns, 98% of trichomes fall in the range from 74 to 200 microns.

[0024] Pre-processed dry plant powder was immediately fed into a vibrational sifter or hopper for further mechanical separation before electrostatic separation. Mechanical separation on the vibrational sifter resulted in the detachment and liberation of most of the glandular trichome heads from the attached stalk, which is critical for further electrostatic separation, mostly determining yield and product purity.

[0025] Finely dispersed particles are fed into the electrostatic separation apparatus, controlling material feed rate, dispersion quality, air temperature and humidity. Two fractions are created-a heads fraction containing mainly trichome heads and a tails fraction containing mainly undesired plant biomass. Particles that did not manage to separate are immediately reprocessed through recirculation of the material.

[0026] Fractions are periodically examined under a microscope to evaluate purity and to determine the percentage of heads in the tail fraction. The process of electrostatic separation can be repeated as necessary to achieve the desired purity.

[0027] EXAMPLE 2. Cannabis or other glandular trichome-bearing plants are collected from the field. Fresh flowers were separated from stems, stalks, and branches using manual or mechanical methods. Plant biomass containing glandular trichomes is refrigerated and sifted under cold temperatures of under 0 °C, using a rotary vibrating sieve or similar device with an upper 190 to 250-micron stainless steel mesh and a lower 25 to 74-micron mesh screen. Temperature is achieved using liquid Carbon Dioxide, Liquid Nitrogen, Dry Ice, or by processing in a cold environment, be it natural or artificially cold. The result is a powder colloquially known as kief or hash. In a specific use case, the dry powder contains glandular and other types of trichomes, pistils, trichomes stalks, pollen, dirt, and fine particles of plant material with particle size distribution from 10 to 300 microns. The dry powder was further sifted on a 250 and 74-micron screen, maintaining the cold chain throughout the process. The initial size of glandular trichomes is in the range of 74-250 microns, 98% of trichomes fall in the range from 74 to 200 microns. Initial mechanical treatment on the sieve resulted in the detachment and liberation of most of the glandular trichome heads from the attached stalk, which was critical for further electrostatic separation, mostly determining yield and product purity.

[0028] Pre-processed dry plant powder was stored in the freezer under temperature of minus 18°C. After several days of storage, the signs of material clumping have been observed. Cold material was fed into the vibrational sifter. Mechanical separation on the vibrational sifter resulted in the declumping of particles, which was crucial for further electrostatic separation, mostly determining yield and product purity.

Claims

1. An apparatus for electrostatic separation of glandular trichomes from plant biomass, comprising: - a dispenser, - a vibrating sifter or hopper (1), - a free-fall separation chamber with oppositely charged metal electrodes (4) and a DC power source for applying a voltage to the electrodes.

2. The apparatus of claim 1, wherein the dispenser has dispenser control means for providing a steady-state stationary flow of plant material into the vibrating sifter or hopper by changing a feeding rate of plant material.

3. The apparatus of any of the previous claims, wherein the vibrating sifter or hopper is capable of vibrating with a frequency ranging from about 1 to about 60 Hz.

4. The apparatus of any of the previous claims wherein the voltage of the DC power source is applied at varying pulse widths and pulse frequencies.

5. The apparatus of any of the previous claims, wherein the electrodes (4) are provided with a rotating mechanisms and dielectric scrapers for self-cleaning.

6. The apparatus of any of the previous claims, further provided with machine vision means for continuously monitoring the dispersion of thricomes and separation quality.

7. The apparatus of any of the previous claims, further provided with a programmed and / or adaptive control system for changing temperature, flow rate and or humidity to achieve a desirable flow rate and separation quality.

8. The apparatus of any of the previous claims, further comprising a recirculation component configured to recirculate at least a portion of the thricomes through the free fall separation chamber.

9. A method for electrostatic separation of glandular trichomes from a sample of dried or frozen plant biomass using the apparatus of any claims 1-10, the method comprising: • dispensing a sample, the first sample containing glandular trichomes; • steady-state channeling of the first sample into the vibrational sifter for declumping particles; • gravitational feeding of finely dispersed particles to the electrostatic separator; • maintain conditions of laminar flow to allow the attraction of free-falling charged particles to the surface of a charged electrode.

10. The method of claim 11, wherein the first sample comprises a particulate size ranging from about 20 to about 300 micrometers.

11. The method of any claims 11- 12, wherein the dispenser has a flow regulation component that maintains the steady-state flow of the thricomes into the vibrational sifter or hopper for mechanical declumping and fine scattering of the thricomes.

12. The method of any claims 11- 13, where electrostatic separation is controlled by electric force on the particles over the length of the separation chamber.

13. The method of any claims 11- 151, further comprises recirculating at least a portion of the thricomes.

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