Patent Publication Number: US-2015085599-A1

Title: Continuous magnetic mixing system with flexible geometric mixing zone

Description:
TECHNICAL FIELD 
     The present teachings relate to the field of fluid manufacture and, more particularly, to a method and system for mixing a fluid, for example in a continuous mixing system. 
     BACKGROUND 
     In industry, batch processes may be used to form a desired quantity of a material such as a fluid. However, it is typically difficult to control and minimize batch-to-batch variations. Once quality standards for a particular batch are not met, the entire batch is often rejected and scrapped prior to completion of the batch to prevent further waste of raw materials. 
     In many batch processes, mixing of a fluid may be a critical process that determines an overall performance of the completed material. For example, in applications where small-sized particles are produced, achieving the small scale and uniform distribution of the particles is determined by the mixing process. Present mixing methods and systems may provide less than uniform mixing efficiency across an entire mixing zone. Mixing may be localized at a central mixing point, for example where an impeller tip for agitation of the fluid is located. Mixing efficiency may decay with increasing distances of the fluid from the impeller tip. Dead spots or shallow spots with inefficient mixing resulting from, for example, fluid turbulence may be distributed along edges of a shaft to which the impeller is mounted. Additionally, a curved vessel or container may result in insufficient mixing. 
     Other mixing systems and methods may generate more complex setups and have other undesirable characteristics, such as an increased number of mechanical parts that must be serviced and repaired. In another type of system, acoustic techniques have been employed in an attempt to avoid inefficient mixing. An acoustic mixing system may include a non-contact technique to provide micro scale mixing within a micro zone of about 50 μm in a closed vessel. However, generating an acoustic wave relies on mechanical resonance as controlled by engineered plates, eccentric weights, and springs. Particular care and protection of the mechanism to generate mechanical resonance is typically used as small turbulence may damage the system. Therefore, the overall service life of an acoustic system is limited to the effective lifetime of the mechanical components. Thus, such systems are not free of mechanical maintenance. Further, acoustic energy decays at increasing distances of the fluid away from the acoustic wave source. 
     Though batch processing is a common manufacturing technique that is sufficient for many technologies, it can be wasteful and may complicate future project planning. Continuous processing of a material may be practiced, depending on the industry. See, for example, published US Pub. 2011/0015320 and U.S. Pat. No. 8,168,699, each of which is incorporated herein by reference in its entirety. In continuous processing (i.e., continuous flow process or continuous production), processing of dry or fluid material occurs continuously rather than in batch processing. Constant efforts to prompt new and facile process with compact system design and effective energy saving would be beneficial for process maintenance, lowering production costs, and enhanced process robustness. 
     Thus, there is a need for a new and improved mixing method and system that overcomes various problems that may be encountered with some conventional systems. 
     SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments of the present teachings. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description presented later. 
     In an embodiment of the present teachings, a system for mixing a fluid may include a first electromagnet phase and a second electromagnet phase, a receptacle for receiving a fluid to be mixed, wherein the receptacle is interposed between the first electromagnet phase and the second electromagnet phase, and a controller configured to activate the first electromagnet phase out of sync with the second electromagnet phase. 
     In another embodiment of the present teachings, a method for continuous mixing of a fluid may include pumping a fluid to be mixed into a mixing receptacle, introducing a plurality of magnetic particles into the fluid to be mixed, activating a first electromagnet phase, and activating a second electromagnet phase out of sync with the activation of the first electromagnet phase as the fluid to be mixed and the magnetic particles are within the mixing receptacle, thereby altering a travel path of the plurality of magnetic particles within the fluid to be mixed, wherein the mixing receptacle is interposed between the first electromagnet phase and the second electromagnet phase. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and together with the description, serve to explain the principles of the disclosure. In the figures: 
         FIG. 1  is a cross section depicting a mixing zone in accordance with an embodiment of the present teachings; and 
         FIG. 2  is a schematic perspective depiction (ghost view) of a mixing zone in accordance with an embodiment of the present teachings. 
     
    
    
     It should be noted that some details of the FIGS. have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The disclosed embodiments relate generally to a method and system for magnetic actuated mixing which use magnetic particles and electromagnetic field to facilitate the mixing. The disclosed embodiments may be used in many different applications, including for example, preparing toners, inks, wax, pigment dispersions, paints, photoreceptor materials, pharmaceuticals, and the like. 
     In an embodiment of the present teachings, a continuous magnetic mixing apparatus and process can be used during the manufacture of a fluid such as a solid powder or liquid material. Various geometric designs of the mixing zone are contemplated. As an embodiment may use micro size magnetic particles for mixing, the embodiment does not require an external mixer and thus the mixing zone may be designed with a desired shape to enhance production or mixing. A varying magnetic field may be provided by one or more electromagnets. The mixing zone may include a horizontal flowing direction, a vertical flowing direction, or a flowing direction that is between horizontal and vertical. An embodiment may allow for the increase of reactant loading in a compact layout, thus enhancing heat transfer effectiveness, reducing manufacturing cost, alleviating difficulty on machining process, and providing a system that is accessible and easily maintained. 
     An exemplary mixing zone  11  of a mixing system, apparatus, or structure  10  and process in accordance with an embodiment of the present teachings is depicted in the cross section of  FIG. 1 . The  FIG. 1  system may include a receptacle  12 , for example a mixing tube  12  as depicted in  FIG. 1 , such as a glass, plastic, polymer, quartz, or metal receptacle interposed between at least a first electromagnet phase  14  and an opposing second electromagnet phase  16 . In an embodiment, the first electromagnet phase  14  and the second electromagnet phase  16  may be two phases of a single electromagnet. In another embodiment, the first electromagnet phase  14  may be a first phase of a first electromagnet and second electromagnet phase  16  may be a first phase of a second electromagnet. An apparatus in accordance with the present teachings may include more than two electromagnets or electromagnet phases, such as an electromagnet coil that surrounds the mixing tube  12  with a plurality of electromagnets, or a single electromagnet having more than two phases. 
     During a continuous mixing process, a fluid  18  to be mixed is injected or otherwise dispensed through a tube inlet  20  into a hollow center  22  of the mixing tube  12 . In an embodiment, a plurality of magnetic particles  24  may be mixed into the fluid  18  prior to injection into the mixing tube  12 . In another embodiment, the mixing tube  12  may include a magnetic particle inlet  26  through which magnetic particles  24  are injected into the fluid  18  as the fluid  18  is injected into the mixing tube  12 . 
     In an embodiment, the magnetic particles may be micro sized or nano sized. For example, the magnetic particles may be between about 10 nanometers (nm) and about 10 millimeters (mm), or between about 200 nm and about 5 mm, or between about 1000 nm and about 1 mm. Further, the magnetic particles  24  may include, for example, iron (e.g., carbonyl iron), cobalt, nickel, and mixtures or alloys of these metals. Additionally, to reduce chemical reactivity of the magnetic particles with the fluid  18 , each magnetic particle may be encapsulated within a chemically inert material such as a polymer. A diameter of the hollow center  22  of the mixing tube  12  may be determined by the desired flow rate of the fluid  18 , a viscosity of the fluid  18 , and the diameter of the plurality of magnetic particles  24 . In general, the diameter of the hollow center  22  may be, for example, between about 10 times and about 100 million times the average diameter of the plurality of magnetic particles  24 , or between about 100 times and about 1 million times the average diameter of the plurality of magnetic particles  24 . 
     As the fluid  18  and magnetic particles  24  flow through the mixing tube  12 , each electromagnet phase  14 ,  16  is pulsed out of phase (i.e., out of sync) with the other electromagnet phase(s) to form a varying magnetic field  28  that drives the magnetic particles  24  to move through the fluid  18 . Movement of the magnetic particles  24  through the fluid  18  generates turbulence within the fluid  18 , thereby mixing the components of the fluid  18 . The frequency and amplitude of the electromagnet phase pulses may be determined in part by the viscosity of the fluid  18  and the size and shape of the magnetic particles  24 . In a two-electromagnet phase embodiment, the two electromagnet phases  14 ,  16  may be activated out of sync, for example 180° out of sync, so that the magnetic particles  24  pulse back and forth within the mixing tube  12 . In an embodiment, an axis of each electromagnet phase  14 ,  16  is parallel with an axis of the mixing tube  12 , such that the mixing tube  12  is interposed between the two electromagnet phases  14 ,  16 . 
     To further enhance mixing or to extend the time the fluid remains in the mixing zone  11  (i.e., the fluid residence time), the mixing tube  12  may include various shapes such as the coil shape depicted in  FIG. 1 . A coil shape effectively increases the length of travel of the fluid within the mixing zone  11  compared to, for example, a straight mixing tube, and therefore increases mixing time for a given fluid velocity through the mixing tube  12 . A coil shape further increases turbulence within the fluid and may therefore improve mixing. In this embodiment, the length of the coiled mixing tube within the mixing zone  11  may be substantially longer than the width of the mixing zone  11  itself, thus providing a compact mixing apparatus design. The mixing tube  12  may be positioned along a generally horizontal axis, a generally vertical axis, or at an oblique axis. 
     Once the fluid travels through the mixing zone  11  of  FIG. 1 , the fluid  18  may be ejected or expelled from the mixing tube  12  through a mixing tube outlet  30 , for example into another mixing tube  31  to route the fluid to another location. In an embodiment, the magnetic particles  24  are inert, for example if coated with a material such as a stable polymer, which stays suspended within the fluid during use of the fluid. One magnetic particle  24  having a coating  25  is depicted in  FIG. 1 . The magnetic particles  24  used for mixing of the fluid may provide some utility during use of the fluid, for example as a dry lubricant that forms a plurality of micro- or nano-sized bearings. In another embodiment, the magnetic particles  24  may be removed from the fluid for recycling or for reuse during subsequent fluid mixing. In an embodiment, magnetic particles  24  may be removed or filtered from the fluid  18  by passing the fluid  18  and magnetic particles  24  through a collector  33  that is in fluid communication with the mixing tube outlet  30 . In an embodiment, collector  33  may be a mesh filter, wherein openings through the mesh are smaller than the magnetic particles  24 . In another embodiment, collector  33  may be a magnet over which the magnetic particles  24  are passed to remove the magnetic particles  24  from the non-magnetic fluid  18 . In another embodiment, collector  33  may be a centrifugal filter that removes  24  from the fluid  18  using a centrifugal process, as long as the process does not result in undue separation of the mixed components of the fluid  18 . 
     The  FIG. 1  system thus improves mixing of the fluid  18  by electrically activating the electromagnet phases (which may be two or more phases of two or more electromagnets, or two or more phases of a single electromagnet) to magnetically control the movement of the magnetic particles  24  through the fluid  18 . An embodiment may further include other elements that improve mixing of the fluid  18 . For example,  FIG. 1  further depicts one or more heating and/or cooling structures  34  that provide a heating and/or cooling zone. The heating and/or cooling structures  34  may be an electric heater/cooler, a blower, etc. having an output  36  that changes the temperature of the fluid  18  within the mixing tube  12 . In an embodiment, the heating and/or cooling zone may be an area interposed between the one or more heating and/or cooling structures  34 . In another embodiment, the heating/cooling zone may be an area where the temperature of the fluid  18  is influenced or changed by structures  34 . The heating and/or cooling zone may be congruent or non-congruent with the mixing zone  11 , for example depending on the length of the heating and/or cooling structures  34  or the area where temperature is influenced by structures  34 . It will be appreciated that structure  34  may be a single heating and/or cooling structure  34  that surrounds the cooling zone, or a plurality of individual structures that cooperate to heat and/or cool the fluid  18  as it passes through the mixing zone  11 . Heating the fluid  18  with structures  34  may be useful in decreasing the viscosity of the fluid  18  within the mixing tube  12  and increasing the speed of a chemical reaction between the components within the mixing tube  12  in certain uses. Cooling the fluid  18  with structures  34  may be useful in increasing the viscosity of the fluid  18  within the mixing tube  12  and decreasing the speed of a chemical reaction between components within the mixing tube  12  in certain uses. 
       FIG. 2  is a schematic perspective depiction of a system  40  in accordance with an embodiment of the present teachings having a plurality of electromagnet phases, for example eight electromagnet phases  42 A- 42 G that completely surround the mixing tube  12  through 360°. The electromagnet phases  42 A- 42 G may be a eight of phases of a single electromagnet, or eight phases of eight different electromagnets. Each electromagnet phase  42 A- 42 G may be independently powered through a power and ground connection (only one of which is schematically depicted in  FIG. 2 ) to each electromagnet phase. A power supply  44  may be used to power the electromagnets  42 A- 42 G, and may also power a controller  46 . The controller  46 , through an independent signal  48 A- 48 G to each electromagnet phase  42 A- 42 G, activates each electromagnet phase in succession to control the movement of the magnetic particles  24  within the fluid  18  in the mixing tube  12 . The controller  46  may include electronics such as control relays for switching the direction of the magnetic field between the two or more electromagnet phases. 
     Thus, an arrangement of the mixing tube  12  and actuation of the electromagnet phases  42 A- 42 G by the controller  46  may be designed to provide efficient mixing of the fluid  18  within the mixing tube  12  within a mixing zone  11  that is compact. For example, in an embodiment, the mixing tube  12  may coil in a first direction (for example clockwise or counterclockwise) from the bottom to the top. The fluid  18  may be dispensed into the mixing tube  12  through the inlet  20  at the bottom of the mixing tube  12  and mixed within the mixing tube  12  using the magnetic particles  24 . After mixing, the fluid  18  exits through the mixing tube outlet  30 . 
     In an embodiment, the controller  46  may activate each electromagnet phase  42 A- 42 G successively in a second direction that is opposite to the first direction (for example counterclockwise or clockwise) such that the magnetic particles  24  resist the flow of the fluid  18  from the inlet  20  to the mixing tube outlet  30 , thus providing a higher turbulence within the fluid for effective mixing of fluid  18  components within the mixing tube  12 . Further, the controller  46  may vary the direction of the electromagnet phase activation from counterclockwise to clockwise during the mixing process to further increase turbulence. Various other magnetic particle  24  travel patterns and mixing tube arrangements are contemplated. 
     Thus, an embodiment of the present teachings may include a continuous magnetic mixing process and structure that has minimal geometric limitations on the size and shape of the mixing zone  11 . The apparatus and process does not require an external mixer such as an impeller. The mixing zone  11  as depicted in  FIG. 1  may be designed with arbitrary three dimensional (3D) shape such as the coil depicted. A varying magnetic field is provided by two or more electromagnetic phases with flexible design consideration, for example, with respect to a horizontal, vertical, or oblique flowing direction. The design may increase reactant loading in a compact layout, enhance heat transfer effectiveness, reduce manufacturing costs, alleviate difficulty on machining process, and allow for simpler maintenance compared to some mixing systems. A continuous mixing system in accordance with an embodiment of the present teachings may have a decreased size, reduced equipment complexity and machining strictness, and enhanced energy utilization, for example heat transfer efficiency. Magnetic particles are introduced into a fluid including one or more components to be mixed. A magnetic field is supplied and varied along the flowing direction to introduce designed travel patterning of the magnetic particles in the flow. This process may introduce continuous mixing in any geometric design of the mixing zone, such as a coil-shaped mixing zone. 
     The continuous mixing process and structure may be used during the manufacture of various materials such as during the preparation of printer and other toners, inks, wax, pigment dispersions, paints such as latex paints, photoreceptor materials, pharmaceuticals, and the like. 
     It will be understood that the embodiments depicted in the FIGS. are generalized schematic illustrations and that other components may be added or existing components may be removed or modified. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present teachings are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc. 
     While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. For example, it will be appreciated that while the process is described as a series of acts or events, the present teachings are not limited by the ordering of such acts or events. Some acts may occur in different orders and/or concurrently with other acts or events apart from those described herein. Also, not all process stages may be required to implement a methodology in accordance with one or more aspects or embodiments of the present teachings. It will be appreciated that structural components and/or processing stages can be added or existing structural components and/or processing stages can be removed or modified. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of” is used to mean one or more of the listed items can be selected. Further, in the discussion and claims herein, the term “on” used with respect to two materials, one “on” the other, means at least some contact between the materials, while “over” means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required. Neither “on” nor “over” implies any directionality as used herein. The term “conformal” describes a coating material in which angles of the underlying material are preserved by the conformal material. The term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims. 
     Terms of relative position as used in this application are defined based on a plane parallel to the conventional plane or working surface of a workpiece, regardless of the orientation of the workpiece. The term “horizontal” or “lateral” as used in this application is defined as a plane parallel to the conventional plane or working surface of a workpiece, regardless of the orientation of the workpiece. The term “vertical” refers to a direction perpendicular to the horizontal. Terms such as “on,” “side” (as in “sidewall”), “higher,” “lower,” “over,” “top,” and “under” are defined with respect to the conventional plane or working surface being on the top surface of the workpiece, regardless of the orientation of the workpiece.