Patent Application
20240229299
This relates to extracting natural fibres from a fibre feedstock, and in particular using reactive oxidizing agents in water.
Hemp is a well-known source of fibre that may be used as a textile. However, to be useful, the natural glue-like compounds that bind the fibres together in the hemp stalks must be removed. This may be referred to as “degumming”. Traditionally, this is done using a mechanical separation, but the process may also be accomplished by other means. U.S. Pat. No. 8,591,701 (Sung et al.) entitled “Extraction of Hemp Fibres” describes an example of an extraction process that uses various chemicals in a water bath. Other sources of natural fibre, such as flax, may also require processing to extract the desired fibres.
According to an aspect, there is provided a method of extracting natural fibres from fibre feedstock, the fibre feedstock comprising gum between the natural fibres, the method comprising introducing fibre feedstock into water; introducing a first oxidizing agent into the water and causing the first oxidizing agent to partially react with the gum; selectively introducing a second oxidizing agent into the water to react with the partially reacted gum, the second oxidizing agent being more reactive than the first oxidizing agent, and removing released fibres from the water.
According to other aspects, the method may comprise one or more of the following features, alone or in combination: the fibre feedstock may be contained within a water-permeable container placed in a tank filled with water, and may further comprise the step of agitating the fibre feedstock in the water by rotating the container; the first oxidizing agent my comprise oxygen, ozone, or a mixture of oxygen and ozone; the first oxidizing agent may be introduced using a manifold, a diffusion apparatus, or combinations thereof; the second oxidizing agent may comprise hydroxyl radicals; introducing hydroxyl radicals may comprise generating the hydroxyl radicals in the water; wherein selectively introducing the second oxidizing agent may comprise concentrating the hydroxyl radicals in a limited volume of the tank; the second oxidizing agent may be introduced into the water after the reactive oxygen generates reaction products; the method may comprise the step of exposing the fibre feedstock to UV light, to ultrasonic energy, or combinations thereof; and the method may further comprise the step of removing the gases and dissolved gases from the water by selectively injecting compressed air into the water.
According to an aspect, there is provided an apparatus for extracting natural fibres from fibre feedstock that comprises gum between the natural fibres, comprising a tank that contains water, the tank being capable of receiving the fibre feedstock, an agitator for agitating the fibre feedstock in the water, a source of a first oxidizing agent, a source of a second oxidizing agent, wherein the second oxidizing agent is more reactive than the first oxidizing agent, a controller that: controls the source of the first oxidizing agent to introduce the first oxidizing agent into the water, the first oxidizing agent being capable of partially reacting with the gum of the fibre feedstock, and selectively controls the source of the second oxidizing agent to introduce the second oxidizing agent into the tank to react with the partially reacted gum.
According to other aspects, the apparatus may comprise one or more of the following features, alone or in combination: the fibre feedstock may be contained within a water permeable container within the tank, and the agitator comprises an actuator that rotates the container; the first oxidizing agent may comprise oxygen, ozone, or a mixture thereof; the source of the first oxidizing agent may comprise a diffuser and/or manifold in the tank; the source of the second oxidizing agent may comprise a generator that generates hydroxyl radicals; the apparatus may further comprise an ultrasonic transducer, a UV light source, or both an ultrasonic transducer and a UV light source in the tank; and the apparatus may further comprise an air injector adapted to inject air into the water of the tank and controlled by the controller.
According to an aspect, there is provided a method of extracting natural fibres from fibre feedstock that comprises gum adhered to the natural fibres, the method comprising introducing the fibre feedstock into water, in a first stage, injecting an oxidizing agent into the water and permitting the oxidizing agent to react with the gum, the oxidizing agent inducing an oxidation reduction potential (ORP) in the water, and wherein a sufficient amount of oxidizing agent is introduced to achieve a first ORP level and, in a second stage, controlling the amount of oxidizing agent introduced into the water to reduce the ORP and maintaining the ORP within a predetermined range that is less than the first ORP level and permitting the oxidizing agent to continue reacting with the gum, and removing released fibres from the water.
According to other aspects, the method may comprise one or more of the following features, alone or in combination: the first ORP level may be at least 500 mV; the method may further comprise the step of filtering the water to remove released gum after the first ORP level has been achieved; the predetermined range may be between 150 mV and 300 mV; the gum may comprise proteins, and in the first stage, the oxidizing agent denatures at least a portion of the proteins on exterior surfaces of the fibre feedstock; a second oxidizing agent may be injected into the water during or after the second stage; and the water may be agitated during the first stage and the second stage.
These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
An apparatus and method for extracting natural fibres from fibre feedstock that comprises gum between the natural fibres will now be described with reference to
The method described herein relates to the extraction of natural fibres by removing or breaking down the natural glue-like compounds that bind the fibres together. The glue-like compounds may include cellulose, hemicellulose, proteins, lignin, saccharides, pectins, wax, hydrotropes, and other biological compounds as well as some other trace elements. These compounds, which may vary between different sources of fibre, will be referred to collectively as “gum”, and the release of the natural fibres from the gum will be referred to as “degumming”. Suitable feedstocks for the process described herein may include hemp, flax, ramie, or other similar sources of natural fibres that must be degummed to obtain useful fibres. The fibre feedstock used in the process below may be subjected to pre-processing steps that may involve mechanically or biologically breaking down and/or separating portions of the vegetation, such as decortication or retting, to separate some or all of the tough, woody portion of a hemp plant from the soft exterior to facilitate treatment of the portion of the vegetation from which the natural fibres will be extracted. Another pre-processing step may include a wash cycle, which may involve injecting water, agitating, and removing the water, to remove easily separable material from the fibres and reduce the amount of material to be treated during the process discussed below. These pre-processing steps will not be described further. In the discussion below, it will be assumed that the fibre feedstock comprises decorticated, raw fibre or an equivalent. This may vary depending on the pre-processing steps employed, and the treatment process described herein may be modified to account for the feedstock to be treated.
The method may start by introducing fibre feedstock into water and, while agitating the fibre feedstock in the water, introducing a first oxidizing agent into the water. The first oxidizing agent is caused to react partially to the gum. A second oxidizing agent is selectively introduced into the water to react with the partially reacted gum to release the fibres from the fibre feedstock. The released fibres are removed from the water.
In one example, the method may use a first oxidizing agent and a second oxidizing agent that is more reactive than the first oxidizing agent. The first oxidizing agent may be easier and/or less expensive to produce, or more readily available in large quantities, and may be used to complete a portion of the reaction used to extract the natural fibres. The second oxidizing agent, which is more reactive than the first oxidizing agent, may be used to complete the reactions necessary to extract the natural fibres. It will be understood that the endpoint of the reaction will depend on the quality of fibre that is to be extracted and the type of fibre feedstock that is being treated, and that in some examples, more or less of a second oxidizing agent may be used to extract a particular grade of fibre. By using separate oxidizing agents, a less expensive oxidizing agent may be used to break down the less stable components of the gum, and a second, more reactive oxidizing agent may be used to compete the extraction by breaking down more stable components of the gum. Care may be taken in the type and concentration of oxidizing agents as well as the reaction time to avoid unnecessary or excessive damage.
The first oxidizing agent may be oxygen (O2), ozone (O3), or a mixture of both. In one example, commercially available equipment may produce a stream of 85% oxygen, 10% ozone, and 5% other gases. The second oxidizing agent may be hydroxyl radicals (OH), which are more reactive than oxygen or ozone, but also more difficult to produce and use. This second oxidizing agent may be used to further break down the remaining gum and/or oxidation products remaining after the reaction with the first oxidizing agent.
Referring to
Referring to
In the plumbing system the water may start in reservoir 102, pass through a pre-screen assembly 138, recirculation filters 116, additional treatment filters 120 and diffusers 112 before being used in tank 11, and returned to reservoir 102.
The plumbing system may also include pump 104, venturi (not shown), and UV sterilizer 114.
The electrical system may be centered around a centralized control panel that houses the electrical components, switches, and indicators, such as: power supply, disconnect/lockout, control panel, circuit breakers, door switches, float switches, relays, and contactors. A source of electricity 140 provides power to components that needs it through electrical connections 142.
The pump control may include various controllers and sensors other than those depicted, such as a door switch, a float switch, a pump relay, a pump contactor, a pump switch, and signal to oxygen and ozone relay.
The gas system may collect air from an ambient air source 160 to supply O2 source 106 and O3 source 108, which may be introduced into the water through gas diffusers 112.
The gas control may include oxygen control components, such as signal receiver from pump contactor, O2 door switch, oxygen relay/contactor, and an O2 generator. The gas controller may include ozone control components, such as a signal receiver from pump contactor, O3 door switch, ORP analyzer, O3 relay/contactor, O3 pressure switch, O3 solenoid, and plasma board.
The UV control, ultrasonic control and fan may each include an on/off signal from PLC, a door switch, and/or an on/off switch, as required.
Also shown in
Referring again to
Once the reaction has progressed to a certain point, an additional oxidizing agent may be introduced in a more selective manner to target the remaining gum, such as components that may take longer to react, or are unable to be reacted by the first oxidizing agent, but may react further with an additional, more aggressive oxidizing agent. The additional oxidizing agent may be hydroxyl radicals. The second oxidizing agent may be introduced in various ways. If the second oxidizing agent is hydroxy radicals, given their instability, the hydroxyl radicals may be generated in situ, such as through photolysis of precursors such as hydrogen peroxide 132 that is introduced into tank 11 and/or ozone. A catalyst, such as titanium dioxide, may also be used to produce hydroxyl radicals. The further oxidizing agent may be generated in situ using UV lights 34 (shown in
Apparatus 10 may have a controller 20 that controls the introduction of the agent(s) and the related equipment described herein. Controller 20 may have an interface such as a touch interface 122 that display indicators and may include manual controls. Controller may controlled manually, may have instructions to automatically control the equipment based on readings, or may have a combination of manual and automated controls.
The fibre feedstock may be treated by controlling the concentrations of one or more oxidizing agents in the reaction vessel to control the reaction kinetics within tank 11 at different stages of the treatment process, and to promote the reaction of the oxidizing agent with the gum while minimizing reactions with the fibre. In addition to breaking down the gum, the oxidizing agents may also be used to bleach the hemp fibres by allowing the oxidising agents, such as ozone and peroxide, to continue reacting with the organic material in the hemp fibres, and in particular, the colouring agents in the hemp fibres.
An example of a process to extract hemp fibre will now be described. The example may be adapted to extract other types of fibres, and may be modified to include different oxidizing agent, different equipment, etc. to achieve the desired results. To start, pre-processed hemp fibre feedstock may be placed into a container 22, which is water impermeable, for treatment where ozonated/UV irradiated water is passed through container 22 and fibres. The feedstock and/or water may be agitated to encourage thorough mixing and even treatment. Natural glues are oxidized into water soluble organic compounds that may be removed from the fibres by the flowing or agitated water. The soluble organic compounds may undergo further redox reactions while in solution with oxidizing agents, or may be filtered out in some cases using recirculating filters 116 and/or water filters 120. At certain points in the cycle the system may manipulate the conditions for Advanced Oxidation reactions to take place between pre-determined set points. O.R.P. (Oxidation Reduction potential) readings may be taken using O.R.P probe 128 and analyzer 126 and may be used, along with other measurements, to determine treatment cycle end point or transitions between treatment stages. Referring to
The fibre may be considered a media in a closed water treatment loop. The contaminants are removed as they are drawn into solution from the natural fibres being treated. This may be implemented as a batch process that may take, for example, 2-6 hrs depending on variables. Periodically more intensive water treatment cycles may be run to remove specific contaminants with all the same equipment. In some cases, it may be more efficient to use a continuous process rather than a batch process. In a continuous process, the equipment may be modified to move the hemp fibres between treatment steps in different tanks 11 through the process, similar to a wool scour system. The components will be similar to those discussed above, but separated into separate tanks 11 or steps.
Through appropriate design, it may be possible to create an environment inside the process where oxidation conditions are capable of removing the unwanted organic compounds to achieve “degumming” of natural fibres. This process may use components that are designed for use in the water treatment industry, which is beneficial as the equipment is designed for large scale continuous operation and long service life at a reduced cost relative to custom-designed equipment.
Oxidation Reduction Potential (O.R.P.), typically measured in millivolts, may be used as a tool to control the oxidation process. Ozone reactions typically occur in a predictable pattern that correlates to O.R.P. readings. These measurements may be used in a few ways. First it may indicate when certain groups of reactions are occurring. This ability to control which type of reactions are most likely to occur may be used to improve or optimize the process and the quality of the output fibre. When the process starts, the O.R.P. may be between, for example, 175-225 mV. The first batch of reactions may occur around 240 mV. The system may reach this O.R.P. level and stay there until those reactions are complete. Selection of the oxidizers and the manner in which they interact with the fibre being treated affect the amount of oxidizers required, the output fibre characteristics, and the treatment cycle time. Introduction of more reactive oxidizers in a controlled manner drastically reduces the time required for treatment. Then O.R.P. will typically jump to the next level where a new set of reactions take place and maintain constant until those reactions are complete, then the O.R.P. will again increase. This process continues until a target O.R.P. is reached and maintained for a set time period, after which the full treatment cycle may be considered to be completed. When the data is charted on a line graph it will typically show a step-like structure where the flat areas indicate O.R.P. levels where certain groups of reactions take place. Each of the steps are optimized to breakdown targeted organic compounds or products of the reactions in the preceding steps.
Another function of an O.R.P. probe and analyzer is to cycle on and off the gas equipment to prevent wastage and improve efficiency. When a certain O.R.P. range is entered into controller 20, which may be a programmable logic controller (P.L.C.) that is used as controller 20 of the process as a whole, it may be used to control the gas equipment to reduce energy consumption by only generating the minimum required amount of treatment gasses required for treatment.
In some examples, the O.R.P. may be controlled at different levels for different treatment stages. For example, in an initial stage, an oxidizing agent, such as ozone, may be injected into the slurry of water and feedstock until a relatively high O.R.P. is reached relative to the other treatment stages, such as around 500-700 mV. This level of O.R.P. may be achieved by injecting a relatively high concentrations of the oxidizing agent. During this stage, the oxidizing agent will react with the gum that is easily-accessible on the hemp fibres, such as gum that is on the outer surface, and allow it to be separated from the fibres. It has been found that this initial “Shock” step may be useful in denaturing proteins that are part of the gum and carried by the hemp fibres, allowing them to be separated from the hemp fibres. The denatured proteins may then be either filtered out, such as in recirculating filters 116, or decomposed by allowing the oxidation reaction to continue. This may be particularly useful when targeting gum or proteins on the outer surface. In a subsequent stage, the amount of oxidizing agent being injected may be reduced or temporarily stopped, allowing the reaction to slow. It has been found that the oxidizing agent reacts with both the hemp fibres and the gum, but that it reacts more readily with the gum. As the gum is found between fibres, slowing the reaction (as indicated by a reduced O.R.P., such as to the levels indicated above) allows the oxidizing agent to react with the less-accessible gum targeted while reducing damage to the hemp fibres.
The reaction may end when a desired quality of hemp fibre is achieved. Depending on the intended use or further processing steps, the acceptable amount of gum may vary. In some cases, it may be desirable to remove substantially all of the gum and/or to bleach the hemp fibres. This may be achieved by varying the treatment time and the strength and concentration of the oxidizing agent(s) used. In some cases, an additional, stronger oxidizing agent may be added as discussed above to provide additional control over the reaction.
During the degumming process, the fibres may be degummed in different ways. In one method, ozone may be added to a point where the fibre feedstock is subjected to hydrotrope oxidation and protein denaturing reactions. Once these steps are complete, the ORP will rise to approximately 600-650 mV at which point the supply of ozone may be shut off and the denatured protein and other components may be filtered off in a wash/filtration process. After the wash/filtration process is complete, the ozone may be reintroduced to maintain an ORP of approximately 600-650 mV to complete the reaction with gum that is between fibres and/or to bleach the fibres. When the reactions are complete, the ozone reactions may increase to approximately 700 mV, indicating that the degumming reactions are complete. In some cases where more gum is permitted in the final product, a different ORM may indicate that the reaction is complete.
In some cases, the gum content on the fiber may be naturally low, meaning there is less gum to be removed to meet set specifications. In these cases the gum content between fibers is significantly less. A similar process may be used as described above, however once the wash/filtration process is complete the ozone will be reintroduced to maintain an ORP of approximately 300-500 mV to ensure full reaction with gum in between fibres is complete, without bleaching the fibres. When the reactions are complete the ozone reactions will increase to approximately 600 mV and the degumming reactions may be considered complete. In this example, the ORP remains high enough without additional ozone added.
The treatment may proceed in batches, which each stage being performed in the same tank, or it may be a progressive system, where the feedstock is transferred between different tanks. For example, a first tank may have a high concentration of an oxidizing agent, and the feedstock may be transferred to another tank once the reaction has reached a desired end point. For example, once the ORP has reached a desired level, indicating a suitable amount of protein has been denatured, the fibre feedstock may be transferred to a wash tank to separate the protein. The fibre feedstock may then be transferred to subsequent tank with a lower concentration of an oxidizing agent to target the less accessible gum carried by the fibres. Rather than perform each task in a single tank, a series of wash, rinse, and reaction vessels may be used with the same or different reactants and different equipment to allow the treatment to proceed as desired, which may include a bleaching tank. Transferring between tanks may be facilitated by placing the fibre feedstock in a porous container as discussed above.
In general, introducing smaller gas bubbles will improve the overall efficiency of the reactions that occur in solution. When small gas bubbles are in solution, they have an extremely large surface area available for oxidation reactions compared to larger bubbles. When gas bubbles are small enough, they are not affected by buoyancy and become suspended in solution for extended periods of time. These bubbles then become susceptible to electromagnetic forces allowing reactions targeting covalent bonds to be preferred. This prevents the waste of valuable treatment gases that otherwise would rise to the surface and escape out the vent and require removal from the exhaust gas stream. Micro bubbles of the same gas repel each other due to having the same electrical charge this acts to further diffuse the gasses within the treatment water. The equipment may be designed to improve gas diffusion at low pressure.
In one example, referring to
The pH of the water may also be controlled to adjust the reaction within the vessel. For example, a higher pH may be used to increase the speed of the ozone reactions. If the pH is raised through the addition of caustic, the caustic may also help scour gum, such as proteins, from the hemp fibres. In one example, a pH of around 10 was found to be beneficial. As with the O.R.P. discussed above, the pH may vary between treatment stages between a more aggressive reaction and a less aggressive reaction.
In one example, the main treatment gases may be ambient air, oxygen and ozone. Both concentrated gases may be generated onsite with the consumables being ambient air and electricity.
Oxygen (O2) may be taken from the atmosphere (about 21%) and concentrated to around 85-90% or more. This may be done via a pressure swing adsorption system called an oxygen concentrator. Referring to
Ozone (O3) may also be generated onsite by flowing oxygen gas through an ozone generator 108 based on oxygen from vessel 106. In one commercially available ozone generator, electrical arcs are discharged to split O2 molecules into individual oxygen atoms. A portion of these oxygen atoms combine with other oxygen molecules to create ozone. Ozone is very reactive relative to oxygen and has a relatively short half-life. Even in the absence of all other substances, ozone will typically degrade back to molecular oxygen (O2) in a relatively short time. As such, ozone is typically generated at the point of use.
Carbon dioxide (CO2) may be added to lower the pH of the process water, if necessary, to enhance treatment and assist in precipitating dissolved metals in the water treatment cycle.
The phrase “Advanced Oxidation Process” (AOP) may refer to the creation of extremely reactive species of particles called free radicals. Free radicals typically have a life span of seconds so they must be created at or extremely close to the point of treatment. There are multiple separate mechanisms in the process that can create the specific particles required for the Advanced Oxidation Process to occur, examples of which are discussed below.
UV systems 32 and 34 in tank 11 may operate at different wavelengths of ultraviolet light. Referring to
There are several reactions in AOP that may be promoted, resulting in free radical particles being present inside the fibre treatment chamber when the AOP systems are operated. A full explanation of the reactions and products of those reactions goes beyond the scope of the present discussion, except to state that oxidation reactions typically happen in a particular sequence that is not random and that may be measured and monitored. Ozone prefers particular reactions over others and with proper control compounds may be predictably reacted out in a sequence that may correlate to a particular O.R.P. level in the water. While the series of reactions of ozone may happen in a relatively linear predictable pattern, the AOP may be less predictable. This may be due to the tendency for free radical particles to react with the closest possible compound or molecule rather than “searching” for a preferred reaction. This makes the introduction of these free radical particles an important consideration. Used at the right time in the degumming process, AOP may assist ozone and oxygen in the oxidation of organic compounds. Care must also be taken to avoid damaging the natural fibres being treated by AOP reactions. Timing, dosage, and duration may be variables controlled by a controller in the operation of the AOP systems discussed herein.
Another function of the AOP systems besides reducing the treatment time may be to provide treatment to the process water and react with or precipitate compounds that ozone cannot or is less likely to remove alone. Natural fibre typically contain traces amounts of elements and compounds that do not readily react with ozone. These compounds are present in relatively small concentrations but may build up as the water is reclaimed and reused. A combination of oxidizers may be used to precipitate molecules or elements that may be resistant to oxidation reactions. Once precipitated, they may be removed from the water with appropriate filtration. This may be performed continuously, or periodically when required.
There may be one or more separate UV systems. In addition to UV lights 32 and 34 depicted in
In some examples, hydrogen peroxide may be introduced in relatively small amounts and at pre-determined points in the process, such as via a venturi and a dosing pump, represented by H2O2 injection block 132 shown in
Referring to
In designing the various components, care should be taken to select materials that are resistant to the oxidizing agents and other equipment used herein. Suitable materials may include P.V.C., Polyethylene, and Stainless Steel.
Referring to
Referring to
Referring to
Walls of tank 11 and the mechanisms inside it may be constructed from stainless steel. In
Natural fibre may be loaded into containers 22 and lowered onto mounts 28 inside the tank 11. Containers 22 may be slowly rotated to stir the fibre during treatment, for example, at approximately 10 RPM, and helps to prevent short circuit flow paths within the fibre. Promoting even treatment of all fibres helps produce predictable, consistent results when degumming natural fibres as product consistency often improves the value to purchasers of the separated fibres. An ultrasonic transducer 36 may also assist in preventing pockets of lower treatment.
Tank 11 may have one or more compressed air manifolds 38 for introducing compressed air, such as for a degassing cycle described below. A diffused gas manifold 40 may also be included for introducing the first oxidizing agent.
To increase the number of AOP reactions, the design may include UV sterilizers placed at points in the system so that free radicals created are present in the treatment chamber and in contact the fibre being treated. As these particles react relatively fast, UV lights may be mounted directly in tank 11 and inline where needed.
It was found that, after running the process for a number of cycles, heavy metals dissolved from the natural fibre were found to have accumulated in the treatment water. Metals may be removed by precipitation and filtration. Using the system to increase the ORP may precipitate certain metals so they can be filtered out of the treatment water. Reaching ORP levels that allow metals to precipitate may require extremely efficient diffusion and high purity ozone. During a treatment cycle, a bypass may be opened to a bank of assorted filters that removes suspended particles and precipitated metals. Running the system in the water treatment cycle may only be done once the treatment water requires. If it is deemed beneficial, H2O2 may be injected to assist with the water treatment cycle. Running at high ORP levels for extended periods may be hard on components of the system. Being a closed loop recirculation system once the desired ORP level is reached, the filtration step may take a relatively short amount of time after which the system may be returned to the regular treatment cycle settings.
Once certain stages of treatment have been accomplished, a degassing cycle may be initiated to remove residual oxidizers prior to the next treatment step, for example, after completing a treatment cycle and prior to opening the treatment chamber. During this cycle, gas generating equipment may be shut down and a solenoid valve to compressed air manifolds 38 may be opened along the bottom of tank 11. Coarse air bubblers may be used to remove the dissolved gasses from the water inside tank 11. Depending on the design, compressed air may be injected using the same manifold used for ozone and oxygen.
Referring to
In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.
The scope of the following claims should not be limited by the preferred embodiments set forth in the examples above and in the drawings but should be given the broadest interpretation consistent with the description as a whole.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2022/050551 | 4/8/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63172428 | Apr 2021 | US |
