WO2023142511A1

WO2023142511A1 - Filter-free, sweeping acoustic wave separation apparatus for separating micro-sized materials from a fluid

Info

Publication number: WO2023142511A1
Application number: PCT/CN2022/123217
Authority: WO
Inventors: Lei Yao; John Leung; Kin Sang SIU; Him Ching YEUNG
Original assignee: The Hong Kong Research Institute Of Textiles And Apparel Limited
Priority date: 2022-01-28
Filing date: 2022-09-30
Publication date: 2023-08-03

Abstract

An apparatus of a micro-sized material separation system by using sweeping acoustic wave to collect and agglomerate micro-sized material from a fluid medium such that the micro-sized material can be trapped and controlled easily for possible after-treatment. It allows continuous flow and processing of the subject fluid medium, and continuous collection of targeted micro-sized material without any chemicals involved. The micro-sized materials can be any matter including but not limited to, dust, particulates, fibers, cells, etc. It has great application potential in areas requiring water purification and particularly in textile industry for recycling of synthetic fibers from laundry sewage water.

Description

FILTER-FREE, SWEEPING ACOUSTIC WAVE SEPARATION APPARATUS FOR SEPARATING MICRO-SIZED MATERIALS FROM A FLUID

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from the U.S. provisional patent application number 63/304,159 filed on January 28 ^th, 2022, and the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention generally relates to an apparatus of a micro-sized material separation system by using sweeping acoustic wave to collect, concentrate and agglomerate those micro-sized materials from a fluid medium such that they can be trapped and controlled easily for possible after-treatment.

BACKGROUND

Microplastic (MP) is defined as plastic debris with dimension within 5mm. In recent years, rich amount of MP has been found in the marine environment. It has been estimated that there is around 51 trillion MP particles in the ocean and the amount is expected to keep increasing. These MP will be in taken by zooplankton, invertebrates and small fish, and thus get into the food chain. It is concerned that MP will endanger the natural environment, and potentially affect human health. The harmful effect of MP to human body is yet fully understood, but it has already gotten increasing concern. The risk of health problem can still be expected due to toxic chemical additives carried by MP getting into human body. Plastic material is usually manufactured with additives like stabiliser, plasticisers, flame retardants and pigments. It is estimated that, per 150 million tonnes of plastic in the oceans, 23 million of which are additives. Besides, contaminants can be absorbed into the plastics. These additives and contaminants would be released when the plastic is in taken.

Laundry of synthetic clothes is taken as main sources of MP, which represents about 35%in primary sources. The global use of synthetic fibers in apparel have kept increasing. The mechanical and chemical stresses experienced by the synthetic textile material is the main reason to cause the MP fibers to detach from yarn of synthetic clothes during washing process in laundry. This implies that it is expected that more and more MP fibers will be released during laundry of synthetic clothes in manufacturing and household washing.

Although sewage water from laundry is supposed to pass through wastewater treatment plants (WWTPs) , it is found that part of the MP will still get into the oceans directly due to their small dimensions. Reloading the effluent water to sediment tank to remove the MP inside would be feasible, but it would need double processing capability (double time, facility or land may be needed) to reprocess the huge volume of cleaned water, which is too costly to afford.

Though membrane-type filters may help capture the MP fibers, the effect is highly dependent on whether filters are handled properly by the consumers (e.g. regular filter cleaning and replacing, proper MP fibers discharging) . Regular replacement of membrane-type filters would also mean more material waste and consumption.

Although ultrafine (UF) filter is able to filter MP at nano size, its reliability may not make it suitable to filter MP. Firstly, there is a fouling problem that will block the pores of the UF filter. Secondly, upon collision by MP, the UF filter membrane would be corroded due to abrasion, which will finally lead to leakage of MP and frequent replacement of filter. This leakage is hard to detect as well.

Acoustic manipulation technique is becoming popular in technology development in recent years, especially in the field of biology and life science. A lot of other techniques have been applied on particle manipulation before, but acoustic manipulation technique is found to be most effective.

Acoustic manipulation technique can be applied in an apparatus of the MP fiber separation system with a filter-free design to separate MP fiber from a fluid medium such as, but not limited to, sewage water discharged from laundry. Currently, there are no existing MP fiber separation systems, which provide a continuous operation of separation and collection of MP fiber by acoustic technique. The apparatus can offer a promising efficiency of MP separation and collection in continuous operation. It is expected that the apparatus can just not be limited to sewage water treatment, but further inspire in developing other machines for removing the MP from other industrial production sources or even the MP existing in marine environment.

The separation chamber of the apparatus will have innovative designs which can facilitate effective and efficient separation and collection of MP fiber. The apparatus can be operated continuously i.e. little reset is required. No chemical is required in using this apparatus. The apparatus will therefore be more cost-effective and efficient for applying in the textile recycling industry. This apparatus can allow business or education institute to easily present the acoustic separation effect concept to bring up the awareness of reuse and saving of resources.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides, among other possible advantages, a low-cost, filter-free apparatus to separate micro-sized materials including, but not limited to MP fiber, from a fluid medium including, but not limited to laundry sewage water. The present invention can efficiently trap, sweep, separate and collect the micro-sized materials from the fluid medium by applying an acoustic wave across the fluid medium. It allows continuous flow and processing of the subject fluid medium, and continuous collection of targeted micro-sized material without any chemicals involved. The micro-sized materials can be any matter including but not limited to, dust, particulates, fibers, cells, etc. The fluid medium can be, but not limited to, water. For example, the MP fiber collected and agglomerated can be taken easily for further treatment and/or recycling. For example, recovered fiber may be blended with virgin for making new clothing. This would bring great benefit to the textile industry as well as the environment.

The present invention employs sweeping acoustic waves generated by ultrasonic transducers to trap, separate, sweep and concentrate the micro-sized materials from the fluid medium. The innovative design of the apparatus facilitates gathering, concentration and collection of the micro-sized materials at one end, at which a collection system and the like is installed. Concentrated micro-sized material with the fluid medium is diverted to another chamber and the like at which the fluid medium will be removed. Subject to the nature of the micro-sized materials to be collected, the micro-sized materials left will undergo an agglomeration process to form a large-scale matter which is easy to be removed and handled for possible future treatment and/or recycling.

The present invention has various advantages in micro-sized material separation and collection. The use of acoustic waves provides an efficient way to separate and collect those micro-sized materials in high-volume and high flow-rate fluid medium. Micro-sized particulates larger than 20μm or fibers longer than 20μm can be separated and collected efficiently. The sweeping acoustic wave with the aid of the innovative design of the acoustic chamber sweeps and further concentrates the trapped micro-sized materials at one end for easy and continuous collection.

In a first aspect, the apparatus of the present invention mainly includes three key parts, namely acoustic separation module, collection module and fluid flow system.

In certain embodiments, the acoustic separation module includes a flow chamber and an acoustic chamber. The acoustic chamber incorporates one or more transducers and provides virtual transducers by reflection effect to trap, direct and concentrate micro-sized materials towards the collection points. Two embodiments of the acoustic chamber with different geometrical configurations are described in detail hereinafter. Other designs with the same and/or similar concepts can also be used as the acoustic separation module.

In certain embodiments, the flow chamber and the acoustic chamber are communicative with and oriented substantially perpendicular to each other, e.g., connected to each other to form a T-shape structure. The flow chamber can be, but not limited to, circular or rectangular in shape. In certain embodiments, the shape of the inlet and outlet sections of the flow chamber are configured to serve a specific purpose. There are at least one fluid inlet and one fluid outlet at two different ends of the flow chamber, respectively. The fluid medium with micro-sized materials, including, but not limited to textile sewage water, flows from the fluid inlet of the flow chamber, fills up both the flow chamber and the acoustic chamber, and then flows out from the fluid outlet. The cross-section of the acoustic chamber can be in, but not limited to, circular, quadrilateral or rectangular shape, depending on the shape of the ultrasonic transducers installed at its open end. One or more ultrasonic transducers are disposed at one end of the acoustic chamber proximal to the flow chamber. In certain embodiments, the ultrasonic transducer (s) is/are operated in oscillating, periodic or pulsed signal of sweeping ultrasonic frequencies. An opposite end of the acoustic chamber is configured to have one or more reflective interior surfaces being one or more reflectors for formation of acoustic standing wave at sweeping frequencies from the acoustic waves generated by the one or more transducers. The reflector (s) can be in shape of a polyhedron including, but not limited to, a cone, regular or irregular right pyramid such as square-based pyramid, hexagonal-based and octagonal-based pyramid, being oriented in a way that a tip of each of the polyhedral reflectors points to the center of gravity in order to facilitate gathering and concentration of micro-sized materials at the tip of the reflector (s) .

In various embodiments, the collection module is connected to the tip of the reflector (s) by a needle valve and the like, which is controlled by a sensory system such as, but not limited to, turbidity meter to monitor the concentration of the micro-sized materials at the tip. When the concentration is sufficiently high, the sensory system will send signal to the needle valve to let the concentrated micro-sized materials with the fluid medium flow out drop by drop to minimize the amount of fluid medium that needs to be removed in later process. Subject to the nature of the micro-sized materials, the fluid medium will then be removed while the micro-sized materials left will undergo an agglomeration process to form a large-scale item for easy handling for possible future treatment.

In certain embodiments, the acoustic separation module is configured to have the flow chamber oriented in a horizontal position and communicated with one end of the acoustic chamber being oriented vertically. In such a configuration, the fluid medium can be flown horizontally through the flow chamber while the acoustic wave generated by the transducer (s) at the one end of the acoustic chamber can travel vertically downward toward the opposite end, i.e., the tip of each of the reflector (s) .

In various embodiments, the fluid medium can be, but not limited to, laundry sewage water. The ultrasonic transducer (s) can be made of, but not limited to, piezo- electric material and they are operated in sweeping ultrasonic frequencies in a range of 1kHz to 100MHz, depending on the size of micro-sized materials needed to be removed.

In certain embodiments, the fluid flow system connects the acoustic separation module via the fluid inlet and outlet of the flow chamber to form a closed circulation system. In certain embodiments, the fluid flow system includes an infeed tank, a reducer, a residue tank, pipes, gauges, flow meters, water pumps, pressurized air and its relevant components, etc. Untreated fluid medium containing micro-sized materials is fed into the infeed tank. The fluid medium with micro-sized materials is then driven to flow through the whole system by water pumps or air pressure, by which the flow rate of the fluid medium inside the system is adjusted. The treated fluid medium is collected at the residue tank while trapped and concentrated micro-sized materials with small amount of fluid medium are collected at the collection module.

In a second aspect, the acoustic separation module of the present apparatus in the first aspect can be operated separately as a standalone acoustic separator, and the acoustic separator includes most of the features of the acoustic separation module in various embodiments of the present invention, but also includes more than one acoustic chamber when needed.

In a third aspect, the present invention provides a method for filter-free, chemical-free, sweeping acoustic wave separation method for separating micro-sized materials from a fluid, the method comprising:

treating the fluid flowing through the acoustic separation module of the apparatus described herein comprising providing sweeping acoustic waves in a direction substantially perpendicular to a fluid flow direction of the fluid along a longitudinal section of the flow chamber of the acoustic separation module by operating one or more ultrasonic transducers disposed at one end of an acoustic chamber of the acoustic separation module at sweeping acoustic frequencies such that the acoustic waves trap, transfer and concentrate the micro-sized materials at a tip of the acoustic chamber which is disposed at an opposite end of where the one or more ultrasonic transducers is/are disposed;

separating the micro-sized materials from the sweeping acoustic wave-treated fluid in the acoustic chamber of the acoustic separation module by controlling a valve of a collection module subject to one or more parameters measured by one or more sensing mechanisms disposed at or adjacent to the valve for monitoring a concentration of the micro-sized materials in the fluid at the tip of the acoustic chamber; when a concentration of the micro-sized materials in the fluid at the tip of the acoustic chamber is detected to be sufficiently high, the valve will be opened to allow the micro-sized materials and residual fluid accompanying therewith to release from the tip of the acoustic chamber into a collection chamber of the collection module;

heating the residual fluid and the micro-sized materials collected into the collection chamber to a vaporization temperature that the fluid is just converted into vapors, and discharging the vapors out of the collection module;

processing the collected micro-sized materials into a form that is readily recyclable or for subsequent processing by one or more mechanisms including physical and mechanical means;

circulating the sweeping acoustic wave-treated fluid from the flow chamber to a collection container of the fluid flow system for subsequent use or recycling.

In certain embodiments, the interior surfaces are configured to be reflective in a direction towards the tip of the acoustic chamber such that acoustic waves at sweeping acoustic frequencies initially generated by the one or more ultrasonic transducers are reflected by each of said reflective interior surfaces when the acoustic waves are incident to said reflective interior surfaces, in order to provide the sweeping acoustic waves for the fluid flowing therethrough.

In certain embodiments, the sweeping acoustic frequencies are in a range of about 1kHz to 100MHz.

In certain embodiments, the sweeping acoustic frequencies are between 2.2MHz and 2.3MHz with a sweep period of about 0.5s and a peak-to-peak voltage of about 40V.

In certain embodiments, the flow rate of the fluid fed into the acoustic separation module is about 20L/hr by one or more means including, but not limited to, water pumps, air pressure or gravity.

The present apparatus or acoustic separator described herein may also be used in other applications including, but not limited to, treating wastewater or industrial sewage, recycling micro-sized materials from a fluid of wastewater or industrial sewage, based on the sweeping acoustic waves generated by the present apparatus or acoustic separator according to certain embodiments of the present invention.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Other aspects of the present invention are disclosed as illustrated by the embodiments hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings, where like reference numerals refer to identical or functionally similar elements, contain figures of certain embodiments to further illustrate and clarify various aspects, advantages and features of the apparatus of the micro-sized material separation system by using acoustic effect to collect and agglomerate micro-sized materials discharged from a fluid medium without chemical condition as disclosed herein. It will be appreciated that these drawings and graphs depict only certain embodiments of the invention and are not intended to limit its scope. The micro-sized material separation system as disclosed herein will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1A schematically depicts an acoustic separation module of the present apparatus according to certain embodiments of the present invention;

FIG. 1B shows a transparent view of the acoustic separation module as shown in FIG. 1A;

FIG. 2 shows a side view of the acoustic separation module as shown in FIG. 1A;

FIG. 3 shows another side view of the acoustic separation module as shown in FIG. 1A;

FIG. 4 shows a bottom view of the acoustic separation module as shown in FIG. 1A;

FIG. 5 shows some possible shapes of the reflector (s) of acoustic chamber of the acoustic separation module of the present invention;

FIG. 6 is a plot of frequency of the ultrasonic wave generated by the transducer against time;

FIG. 7 is an image showing, from side view, the acoustic separation of MP particles in a pyramid-shaped reflector in the acoustic chamber according to certain embodiments of the present invention;

FIG. 8 is an image showing, from bottom view of the reflector, the acoustic separation of MP particles in the pyramid-shaped reflector in the acoustic chamber;

FIG. 9A schematically depicts an acoustic separation module of the present apparatus according to other embodiments of the present invention;

FIG 9B shows a transparent view of the acoustic separation module as shown in FIG. 9A;

FIG. 10 shows a side view of FIG. 9A;

FIG. 11 is another side view of FIG. 9A;

FIG. 12 schematically depicts the collection module of the present apparatus according to certain embodiments of the present invention;

FIG. 13 is a flow diagram of the present apparatus including the fluid flow system, acoustic separation module and collection module according to certain embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to an apparatus of a micro-sized material separation system by using sweeping acoustic wave to collect, concentrate and agglomerate those micro-sized materials from a fluid medium such that they can be trapped and controlled easily for possible after-treatment. It allows continuous flow and processing of the subject fluid medium, and continuous collection of targeted micro-sized material without any chemicals involved. The micro-sized materials can be any matter including but not limited to, dust, particulates, fibers, cells, etc. The fluid medium can be, but not limited to, water.

In the following detailed description, the method, system, apparatus and device are merely exemplary in nature and are not intended to limit the disclosure or its application and/or uses. It should be appreciated that a vast number of variations exist. The detailed description will enable those of ordinary skill in the art to implement an exemplary embodiment of the present disclosure without undue experimentation, and it is understood that various changes or modifications may be made in the function and arrangement of methods, systems and devices described in the exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims. The exemplary embodiments may not be limited to the precise embodiments described below, and may be practiced without some of these specific details. In other instances, structures and methods have not been described in detail, if already well known.

Acoustic separation technique captures particles by formation of a standing wave. In fluid, when particles inside experience a standing wave, an acoustic radiation force would exert on the particles and push them to nodal plane or anti-nodal plane, depending on acoustic contrast factor

which is affected by the value of density and compressibility of the particles and surrounding liquid. If

is positive, particle will be pushed to nodal plane. If

is negative, particle will be pushed to the anti-nodal plane. The force magnitude would also depend on other parameters like particle volume, acoustic wave pressure and the wavelength of the acoustic wave. The equations of the acoustic radiation force are: -

where P ₀ is the pressure amplitude, V the volume of the particle, λ the acoustic wave length, while β and ρ refer to the compressibility and the mass density of the fluid and the particle, indicated by subscripts w and c, respectively. The acoustic contrast factor (ACF) ,

determines the direction of the acoustophoretic force.

Although the separation target of the present invention is initially MP fiber, it should be understood that the present invention is capable to separate substantially all micro-sized materials such as, but not limited to, dust, fibers, particulates, cells, etc. with non-zero acoustic contrast factor

from a fluid medium by the acoustic separation module.

For easy illustration of the operation of the present invention, MP fibers are taken below as an example of separation target. MP fibers can be, but not limited to, polyethylene terephthalate (PET) fiber, acrylic fiber and nylon fiber, which are the main synthetic fibers being used in consumer market. This is a novel apparatus and beneficial for textile recycling industry.

The physical properties and

coefficients of various synthetic fibers are shown at Table 1. It shows that most of the common synthetic fibers have positive

that means those fibers will be pushed to the nodal plane by the acoustic radiation force.

Table 1

The present invention has three key parts, namely acoustic separation module, collection module and fluid flow system. Two specially designed acoustic separation modules (Designs 1 &2) are illustrated below as examples of the operation of the separation system. Other designs with the same and/or similar concepts can also be used as the acoustic separation module.

Those two acoustic separation modules (Designs 1 &2) use the same design of collection module and fluid flow system. Designs 1 &2 are illustrated below in details: -

Design 1 –Pyramid-shaped Reflector

The Acoustic Separation Module of Design 1 includes a T-shaped flow chamber cum acoustic chamber as shown in FIG. 1A and FIG. 1B. FIG. 1B is the transparent view of FIG. 1A such that the inner structure of the Acoustic Separation Module can be shown easily.

FIG. 1A shows the structure of Design 1 of the T-shaped flow chamber 101 cum acoustic chamber 102; FIG. 1B shows the internal structure of the T-shaped flow chamber 101 cum acoustic chamber 102. Fluid medium with MP fibers is fed at inlet 103 into the flow chamber (highlighted in dashed line box) . The shape of the flow chamber 101 is specially designed to minimize the accumulation of micro-sized materials inside the flow chamber. The acoustic chamber 102 (highlighted in dotted line box) is perpendicular to the flow chamber 101 to form a T-shaped apparatus and it is, but not limited to, rectangular shape depending on the shape of the ultrasonic transducer installed at its open end 105. Another end of the acoustic chamber is a reflector 106, which is specially designed in pyramid-shape, for the transducer for efficient formation of acoustic standing wave at sweeping frequencies. The flow chamber 101 and the acoustic chamber 102 are connected to each other in T-shape, i.e. the flow chamber 101 and the acoustic chamber 102 are installed perpendicular to each other. The shape of the flow chamber 101 is specially designed to minimize the accumulation of MP fibers inside the flow chamber. There is an inlet 103 and an outlet 104 at 2 ends of the flow chamber respectively. The fluid medium with MP fiber, for example textile sewage water, flows from the inlet 103, fills up both the flow chamber 101 and the acoustic chamber 102, and then flows out from the outlet 104. The acoustic chamber 102 is in rectangular shape in Design 1 and it can be in, but not limited to, circular and rectangular shape depending on the shape of the ultrasonic transducer installed at its open end 105. The ultrasonic transducer is operated in oscillating, periodic or pulsed signal of sweeping ultrasonic frequencies. Another end of the acoustic chamber is a reflector 106, which is specially designed in a regular-based right pyramid shape in Design 1, for the transducer for efficient formation of acoustic standing wave at sweeping frequencies.

The reflector 106 can be in shape of a polyhedron including, but not limited to, a cone, and regular or irregular right pyramids including but not limited to, square-based pyramid, hexagonal-based and octagonal-based pyramid as shown in FIG. 5.

As an example, a 2MHz PZT-4 transducer was installed in the acoustic chamber of design 1 as shown in FIGs. 1A and 1B. The transducer was driven by a linear swept frequency signal as in FIG. 6, which shows the change in sweeping frequencies applying on micro-sized materials in the acoustic chamber over time. The frequency of the ultrasonic wave would increase continuously from a minimum to a maximum and then drop back to minimum value to complete a cycle. The frequency range of the sweep was between 2.2MHz and 2.3MHz such that the transducer was operated near at its resonance frequency of 2.25MHz. The sweep period was 0.5s. The peak-to-peak voltage across the transducer was 40V pk-pk. The flow rate of water with MP particles was about 20L/hr. FIGs. 7 and 8 show the acoustic separation of MP particles in the pyramid-shaped reflector in the acoustic chamber. Trains of MP particles were observed to be swept towards the pyramid-shaped reflector by the acoustic wave generated by the transducer. Due to the pyramid shape, reflection on each side of the pyramid could be considered as formation of virtual transducers, which generated acoustic wave perpendicular to the original source. The acoustic waves from these virtual transducers together with the original transducer resulted in formation of sweeping wave towards the tip/apex of the reflector. Therefore, MP particles were trapped, swept and concentrated at the tip/apex, where they were collected by the Collection Module. FIG. 4 shows the pyramid-shape reflector 106 and the tip/apex 107 from the bottom view.

The reflector 106 is specially designed in pyramid shape in Design 1. When the primary acoustic wave hits on the surface of the reflector 106, the wave will be reflected perpendicular to the primary wave. The surface can thus be regarded as “mirrors” which create multiple virtual transducers in corresponding directions. Therefore, the primary wave and the reflected wave form a standing wave inside the pyramid-shape reflector region of the acoustic chamber and thus make it efficient in trapping, gathering and concentration of MP fiber towards the tip/apex 107 of the reflector 106. Thus, this pyramid-shaped reflector is an innovative design to enhance the collection efficiency. It can be in shape of a polyhedron including, but not limited to, a cone and regular or irregular right pyramids, including but not limited to square-based pyramid, hexagonal-based and octagonal-based pyramid as shown in FIG. 5.

The inlet section 108 of the flow chamber is designed in pyramid shape such that i) it can reduce the chance of MP fiber accumulation inside the flow chamber and thus MP fiber can more easily be driven by the fluid medium towards the acoustic chamber for acoustic separation; ii) it can reduce the turbulence effect while the fluid medium flow from a narrower inlet to a wider flow chamber.

FIGs. 2 and 3 show the inlet section 108 and the outlet section 109 of the flow chamber, respectively. The inlet section is designed in pyramid shape such that i) it can reduce the chance of accumulation of micro-sized materials inside the flow chamber and thus those micro-sized materials can more easily be driven by the fluid medium towards the acoustic chamber for acoustic separation; ii) it can reduce the turbulence effect while the fluid medium flow from a narrower inlet to a wider flow chamber. The cross-section area of the outlet section 109 of the flow chamber is designed to decrease gradually along the way from the acoustic chamber 102 to the outlet. Its cross-section area is designed to decrease gradually along the way from the acoustic chamber 102 to the outlet 104. When the whole acoustic separation module is set up in substantially a vertical orientation, i.e. the flow chamber is in horizontal position and on top of the vertical acoustic chamber, the outlet section 109 can be regarded as an inclined plane with decreasing cross-section area directing the fluid medium towards the outlet 104, which is located at the highest point of the acoustic separation module. In case where some MP fibers can escape from the acoustic waves by chance, this design can minimize the amount of those untrapped MP fibers from flowing back to the fluid stream while laminar flow inside the flow chamber is maintained.

Design 2 –V-shaped Acoustic Chamber

The acoustic separation module of Design 2 including a T-shaped flow chamber cum acoustic chamber are shown in FIGs. 9A and 9B. FIG. 9B is the transparent mode of FIG. 9A such that the inner structure of the separation module can be shown easily. The flow chamber 901 and the acoustic chamber 902 are connected to each other in T-shape, i.e., the flow chamber 901 and the acoustic chamber 902 are installed substantially perpendicular to each other. There is an inlet 903 and an outlet 904 at 2 ends of the flow chamber 901 respectively. The fluid medium with MP fiber, for example textile sewage water, flows from the inlet 903, fills up both the flow chamber 901 and the acoustic chamber 902, and the flows out from the outlet 904. The acoustic chamber 902 is, but not limited to, rectangular shape depending on the shape of the ultrasonic transducers installed at its open end 905. Two ultrasonic transducers (905a, 905b) are installed in V-shape such that they are perpendicular to each other. They are operated in oscillating, periodic or pulsed signal of sweeping ultrasonic frequencies. Another end of the acoustic chamber are their respective reflectors (906a, 906b) for formation of acoustic standing wave at sweeping frequencies. As the 2 transducers are installed perpendicular to each other, the resulting standing wave formed would be pointing downward to the tip 907 at the bottom of the acoustic chamber.

As a demonstration, two 2MHz PZT-4 transducers were installed in the acoustic chamber of Design 2 as shown in FIGs. 9A and 9B. The transducers were driven by a linear swept frequency signal as in FIG. 6. The frequency range of the sweep was between 2.2MHz and 2.3MHz such that the transducers were operated near at theirs resonance frequency of 2.25MHz. The sweep period was 0.5s. The peak-to-peak voltage across the transducers were 40V pk-pk. The flow rate of water with MP particles was about 20L/hr. As the 2 transducers were installed perpendicular to each other, the resulting standing wave formed would be pointing downward to the tip 907 at the bottom of the acoustic chamber and thus it was efficient in trapping, gathering and concentration of MP fiber towards the tip 907, where they were collected by the collection module. FIGs. 10 and 11 show the inlet section 908, and the outlet section 909 of the flow chamber 901, respectively.

Collection Module

The collection module including a needle valve 1201 with a sensory system 1202 and a collection tank 1204 equipped with a hot plate 1203 is shown in FIG. 12. The collection tank 1204 is connected to the acoustic separation module via the needle valve 1201 and the like, which is controlled by the sensory system 1202 such as, but not limited to turbidity meter, to monitor the concentration of MP fibers at the collection point of the acoustic separation module. When the concentration is high enough, the sensory system 1202 will send signal to the needle valve 1201 to let the fluid medium with the concentrated MP fibers out drop by drop to the collection tank 1204 in order to minimize the amount of fluid medium that needs to be removed in later process.

The collection tank 1204 is equipped with a hot plate 1203 which is pre-set at temperature as high as 90℃. Therefore, the fluid medium such as water in the collection tank 1204 evaporates while the MP fiber left inside the collection tank would undergo an agglomeration process to form a large-scale item for easy handling for possible future treatment. The molding temperature ranges of various synthetic fibers is shown in Table 2.

Table 2

	Molding Temperature (℃)
Nylon 6	40 –90
Polyethylene (PE) (high density)	10 –80
Polyethylene terephthalate (PET)	80 –120
Polypropylene (PP)	30 –80
Polystyrene (PS)	30 –60

After a sheet of plastic is formed by merging of MP fiber on the hot plate 1203, mechanical method can be applied to remove with aid of some technique, for examples but not limited to, applying a PTFE Teflon layer on the hot plate, or using the difference in thermal expansion to loosen the sheet of plastic from the hot plate by freezing.

Therefore, the present invention in principle can operate continuously and automatically to trap, concentrate, collect and agglomerate the MP fiber. Only regular removal of agglomerated MP from the hot plate is required without stopping the system flow. In this connection, the collection module plays an important role in the continuous operation of the present apparatus.

Subject to the nature of the fluid medium and the micro-sized materials needed to be separated, the temperature of the hot-plate in the collection module or even the fluid removal methodology of the collection module can be changed and varied so as to suit the evaporation temperature of the fluid medium and/or specific requirement of the target micro-sized materials.

Fluid Flow System

The fluid flow system connects the acoustic separation module via the inlet and outlet of the flow chamber to form a closed circulation system as shown in FIG. 13. It includes, but not limited to, an infeed tank 1301, a reducer 1302, a residue tank, pipes, gauges, flow meters, water pumps, pressurized air and its relevant components 1304, etc. Untreated fluid medium containing MP fiber is fed into an infeed tank 1301, which is connected to a reducer 1302 to prevent accumulation of MP fiber inside the tank. The reducer 1302 is then connected to the inlet of the acoustic separation module via pipes, which are made of, but not limited to, stainless steel. The outlet of the acoustic separation module is connected to a residue tank 1303 for collection of the treated fluid medium.. The fluid medium with MP fibers in the infeed tank 1301 is driven to flow through the whole system, including the Acoustic Separation Module and Collection Module, by one or more means including, but not limited to, water pumps, air pressure, and gravity, at flow rate of about 20L/hr. The treated fluid medium is collected at the residue tank while trapped and concentrated MP with small amount of fluid medium are collected at the collection module as shown in FIG. 12.

To optimize the micro-sized material separation apparatus for different sources/nature of the fluid medium, different parameters can be varied, including, but not limited to the followings: the frequencies, amplitudes and sweeping time of the ultrasonic waves; flow rate of fluid medium; dimensions and/or design of the flow chamber and/or acoustic chamber; sensitivity of the sensory system of the needle valve 1201, etc. One of the main purposes of the optimization is to achieve a maximum capacity from a limited space and miniaturizing the entire system including utilities and support system, together with a layout that allows efficient and robust operations for providing a micro-sized material separation method and system using sweeping acoustic waves as a sole source of separation power.

The invention can be partially or fully automated in order to improve product output quality. The micro-sized materials collected and agglomerated in the collection module have been studied and shown to have possible usage and recycling potential.

The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising, ” “having, ” “including, ” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to, ” ) unless otherwise noted.

INDUSTRIAL APPLICABILITY

The present system can help the textile industry to separate MP fibers from laundry sewage water generated during manufacturing and washing. It can help reduce and relieve the impact of release of MP fibers to marine environment and thus enhance the sustainability of the textile industry. The MP fibers collected could be further processed and recycled for making new clothing or other potential applications. Therefore, it can simultaneously minimize the demand for virgin fibers and thus contribute to mitigate textile waste problem. The textile industry in Hong Kong and elsewhere will be benefited as they can reuse the recycled fibers for making new clothing, thus reducing the procurement demand for virgin fibers.

Since the present invention is capable to separate all other micro-sized materials such as, but not limited to, dust, fibers, particulates, cells, etc., the present invention is applicable to all kinds of water purification. The present invention not only provides a promising continuous flow of operation of separation and collection, but also provides a post-treatment of the collected materials which then can be handled more easily for further process/recycling/treatment. Its potential application will be, but not limited to, MP fiber separation and recycling from laundry sewage water in textiles industry, and water purification in water treatment plants. In short, the present invention is also beneficial to both textile industry and environment.

Improvements on the present invention includes system production capacity enhancement and fabric separation accuracy. These improvements will allow better separation quality and time, and reduce manpower requirements.

Claims

A filter-free, sweeping acoustic wave separation apparatus for separating micro-sized materials from a fluid, collecting, and agglomerating the separated micro-sized materials, the apparatus comprising:

an acoustic separation module;

a collection module; and

a fluid flow system,

the acoustic separation module comprising a flow chamber and an acoustic chamber communicating with each other and being oriented in two different directions,

the flow chamber comprising a fluid inlet communicating with a fluid outlet of the fluid flow system; and a fluid outlet communicating with a fluid inlet of the flow chamber of the acoustic separation module, the flow chamber having an increasing cross-sectional area in a longitudinal direction from the fluid inlet towards a center thereof and a decreasing cross-sectional area in the longitudinal direction from the center towards the fluid outlet thereof such that accumulation of the micro-sized materials inside the flow chamber is minimized, thereby directing the micro-sized materials towards the acoustic chamber more easily in the presence of the fluid for acoustic separation,

the acoustic chamber comprising one or more ultrasonic transducers and being geometrically configured to form an inverted polyhedral reflector with tapered sides and a tip at which at least three tapered sides meeting with each other, and each interior surface of the inverted polyhedral reflector being reflective to reflect initial acoustic waves generated by one or more ultrasonic transducers and/or reflected acoustic waves by one or more preceding, reflective interior surfaces to result in a series of sweeping acoustic waves travelling towards the tip,

the collection module configured to communicate with the tip of the acoustic chamber, monitor flow of fluid from the tip when there is a sufficiently high concentration of micro-sized materials in the fluid at the tip, and heat the fluid collected from the tip of the acoustic chamber.
The apparatus of claim 1, wherein the flow chamber and acoustic chamber are oriented substantially perpendicular to each other such that a T-shape structure is formed wherein the tip of the acoustic chamber points to the center of gravity.
The apparatus of claim 1 or 2, wherein the reflector (s) of the acoustic chamber is in shape of a polyhedron including a plane, an inverted cone-shaped or pyramid-shaped structure where the tip thereof points to the center of gravity.
The apparatus of claim 1 or 2, wherein the one or more ultrasonic transducers is/are operated in oscillating, periodic or pulsed signal of sweeping ultrasonic frequencies.
The apparatus of claim 4, wherein the sweeping ultrasonic frequencies are in a range of about 1kHz to 100MHz.
The apparatus of claim 4, wherein the one or more ultrasonic transducers is/are made of piezoelectric material.
The apparatus of claim 4, wherein two of the transducers are disposed substantially perpendicular to each other at one end of the acoustic chamber.
The apparatus of claim 1 or 2, wherein the fluid is initially fed by the fluid flow system into the inlet of the flow chamber and then flows through the flow chamber until the fluid meets the acoustic waves generated by the one or more transducers which travel in an overall direction substantially perpendicular to the flow direction of the fluid in the flow chamber such that the micro-sized materials in the fluid are separated from the fluid by the acoustic waves and collected at the tip of the acoustic chamber, while the fluid after being treated by the acoustic waves continues to travel longitudinally within the flow chamber until reaching the fluid outlet thereof to circulate back to the fluid flow system where the inlet of the fluid flow system communicates with the fluid outlet of the flow chamber.
The apparatus of claim 8, wherein the fluid flow system comprises an infeed container, a reducer, a residue container, a plurality of pipes, gauges, flow meters, water pumps and an air pressurizer.
The apparatus of claim 9, wherein the fluid containing the micro-sized materials is fed from the infeed container, through the reducer which communicates with the inlet of the flow chamber, into the acoustic chamber.
The apparatus of claim 9, wherein the residue container communicates with the fluid outlet of the flow chamber to receive the fluid from the acoustic chamber after said separation of the micro-sized materials.
The apparatus of claim 10, wherein the fluid in the infeed container is driven to flow through the whole system by one or more means comprising water pumps, air pressure and gravity.
The apparatus of claim 8, wherein the collection module collects the micro-sized materials separated from the fluid by the acoustic waves in the acoustic chamber together with any residual fluid accompanying the separated micro-sized materials at one end of the collection module, and transfers the collected micro-sized materials and the residual fluid to an opposite end of the collection module where a heating element with a vaporization temperature is provided to heat the collected residual fluid until the residual fluid is evaporated and vapors arising therefrom are discharged from the collection module, while the collected micro-sized materials are further agglomerated into a large-scale aggregate for subsequent treatment.
The apparatus of claim 13, wherein the collection module comprises a valve disposed at the one end thereof and incorporated with one or more sensing mechanisms to monitor the change in concentration of micro-sized materials along a path which the micro-sized materials are received from the tip of the acoustic wave chamber to the one or more sensing mechanisms.
The apparatus of claim 14, wherein the valve is controlled by a sensory system connected to the one or more sensing mechanisms such that when the concentration of the micro-sized materials at the tip of the acoustic chamber is detected to be sufficiently high, the valve is opened to allow both the micro-sized materials and the accompanying residual fluid to release from the tip of the acoustic chamber dropwisely and subsequently the micro-sized materials and the accompanying residual fluid are collected in a collection chamber of the collection module at where the heating element is disposed.
The apparatus of claim 13, wherein the vaporization temperature is at about 90 to 100 ℃.
The apparatus of claim 13, wherein the large-scale aggregate of micro-sized materials is formed by one or more processes comprising thermal and/or mechanical processes.
The apparatus of claim 17, wherein the large-scaled aggregate is formed by applying heat at a temperature from 10 to 120 ℃.
The apparatus of claim 19, wherein the heating element comprises a release mechanism such that after the micro-sized materials are heated to form a layer of materials, the release mechanism facilitates removal of the layer of materials from the heating element.
The apparatus of claim 19, wherein the release mechanism comprises one or more methods of coating a high temperature resistant synthetic polymer layer containing carbon and fluorine on the heating element, a mechanical method to remove the layer of materials, and a method of thermal expansion followed by freezing.
The apparatus of claim 1, wherein the micro-sized materials comprise particulates, fibers, dust, cells, and any materials with a non-zero acoustic contrast factor separable from the fluid by the acoustic separation module.
The apparatus of claim 1, wherein the fluid comprises water sewage from sources including textile and apparel industries, fabric manufacturing and processing industries, plastic industries, medical equipment industry, and/or laundry operations.
A filter-free, chemical-free, sweeping acoustic wave separation method for separating micro-sized materials from a fluid, the method comprising:

treating the fluid flowing through the acoustic separation module of the apparatus according to any one of claims 1 to 22 comprising providing sweeping acoustic waves in a direction substantially perpendicular to a fluid flow direction of the fluid along a longitudinal section of the flow chamber of the acoustic separation module by operating one or more ultrasonic transducers disposed at one end of an acoustic chamber of the acoustic separation module at sweeping acoustic frequencies such that the acoustic waves trap, transfer and concentrate the micro-sized materials at a tip of the acoustic chamber which is disposed at an opposite end of where the one or more ultrasonic transducers is/are disposed;

separating the micro-sized materials from the sweeping acoustic wave-treated fluid in the acoustic chamber of the acoustic separation module by controlling a valve of a collection module subject to one or more parameters measured by one or more sensing mechanisms disposed at or adjacent to the valve for monitoring a concentration of the micro-sized materials in the fluid at the tip of the acoustic chamber; when a concentration of the micro-sized materials in the fluid at the tip of the acoustic chamber is detected to be sufficiently high, the valve will be opened to allow the micro-sized materials and residual fluid accompanying therewith to release from the tip of the acoustic chamber into a collection chamber of the collection module;

heating the residual fluid and the micro-sized materials collected into the collection chamber to a vaporization temperature that the fluid is just converted into vapors, and discharging the vapors out of the collection module;

processing the collected micro-sized materials into a form that is readily recyclable or for subsequent processing by one or more mechanisms including physical and mechanical means;

circulating the sweeping acoustic wave-treated fluid from the flow chamber to a collection container of the fluid flow system for subsequent use or recycling.
The method of claim 23, wherein the interior surfaces are configured to be reflective in a direction towards the tip of the acoustic chamber such that acoustic waves at sweeping acoustic frequencies initially generated by the one or more ultrasonic transducers are reflected by each of said reflective interior surfaces when the acoustic waves are incident to said reflective interior surfaces, in order to provide the sweeping acoustic waves for the fluid flowing therethrough.
The method of claim 23 or 24, wherein the sweeping acoustic frequencies are in a range of about 1kHz to 100MHz.
The method of claim 25, wherein the sweeping acoustic frequencies are between 2.2MHz and 2.3MHz with a sweep period of about 0.5s and a peak-to-peak voltage of about 40V.
The method of claim 23 or 24, wherein the air pressure in the infeed container is elevated to about 2 to 5 bars.
The method of claim 26, wherein flow rate of the fluid fed into the acoustic separation module is about 20L/hr by one or more means comprising water pumps, air pressure and gravity.
A filter-free, chemical-free, acoustic separator for separating micro-sized materials from a fluid, the separator comprising a flow chamber and at least one acoustic chamber communicating with each other and being oriented in two different directions,

the flow chamber comprising a fluid inlet and a fluid outlet for input and output of the fluid, respectively, and being configured to have an increasing cross-sectional area in a longitudinal direction from the fluid inlet towards a center thereof and a decreasing cross-sectional area in the longitudinal direction from the center towards the fluid outlet thereof such that accumulation of the micro-sized materials inside the flow chamber is minimized, thereby directing the micro-sized materials towards the acoustic chamber more easily in the presence of the fluid for acoustic separation,

the acoustic chamber comprising one or more ultrasonic transducers and being geometrically configured to form an inverted polyhedral reflector with tapered sides and a tip at which at least three tapered sides meeting with each other, and each interior surface of the inverted polyhedral reflector being reflective to reflect initial acoustic waves generated by one or more ultrasonic transducers and/or reflected acoustic waves by one or more preceding, reflective interior surfaces to result in a series of sweeping acoustic waves travelling towards the tip
The separator of claim 29, wherein the one or more ultrasonic transducers is/are operated in oscillating, periodic or pulsed signal of sweeping ultrasonic frequencies.
The separator of claim 29 or 30, wherein the reflector of the acoustic chamber is in shape of a polyhedron including a plane, an inverted cone-shaped or pyramid-shaped structure where the tip thereof points to the center of gravity.
The separator of claim 29 or 30, wherein the flow chamber and one of the acoustic chambers are oriented substantially perpendicular to each other such that a T-shape structure is formed wherein the tip of the acoustic chamber points to the center of gravity.
The separator of claim 30, wherein the sweeping ultrasonic frequencies are in a range of about 1kHz to 100MHz.
The separator of claim 30, wherein the one or more ultrasonic transducers is/are made of piezoelectric material.
The separator of claim 30, wherein at least two of the transducers are disposed substantially perpendicular to each other at one end of the acoustic chamber.
A method for treating wastewater or industrial sewage based on sweeping acoustic waves comprising using the apparatus according to any one of claims 1 to 22.
A method for recycling micro-sized materials from a fluid of wastewater or industrial sewage based on sweeping acoustic waves comprising using the apparatus according to any one of claims 1 to 22.