Patent Publication Number: US-2023149866-A1

Title: Wet atomization apparatus and method

Description:
TECHNICAL FIELD 
     The present invention relates to a wet atomization apparatus and a wet atomization method both for atomizing particles contained in a fluid to be processed (herein also referred to as “process-target fluid”). More specifically, the present invention relates to a wet atomization apparatus and a wet atomization method both capable of advanced atomization of particles contained in a process-target fluid by a simple process of moving the process-target fluid forward and backward in a thin tube. 
     BACKGROUND ART 
     A conventional apparatus equipped with a wet jet mill processing section as described in Patent Literature (hereinafter, referred to as PTL) 1 is known. The wet jet mill processing section ejects a process-target fluid, in which the particles are contained, from one or two nozzles at ultra-high pressure, thereby atomizing the particles contained in the process-target fluid. 
     PTL 1 describes a slurry producing apparatus in which a following process is performed: a slurry precursor formed in mixing tank  11  by mixing a solvent and powder is discharged from mixing tank  11  by liquid supply pump  13 ; the slurry precursor is pressurized to have a pressure of, for example, 10 MPa or more by pressure booster  14 , and is ejected into collision unit (wet jet mill processing section)  15 ; after subjected to a wet jet mill treatment in the unit, the slurry precursor is introduced into mixing tank  11  by circulation pump (circulation section)  17 ; and a small amount of powder is mixed into the slurry precursor in mixing tank  11 . By repeating the above process a predetermined number of times, a slurry having a desired powder concentration is produced, and then valve  18  is switched to guide the produced slurry to slurry tank  19 . 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1 
         Japanese Patent Application Laid-Open No. 2010-77001 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The slurry producing apparatus described in PTL 1 have the following problems. In addition to the use of two pumps, liquid supply pump  13  and circulation pump  17 , provision of pressure booster  14  after liquid supply pump  13  is necessary; further, the provision of mixing tank  11  for mixing a solvent and powder and slurry tank  19  for receiving the produced slurry at different positions is also necessary. As a result, the apparatus becomes large and expensive, and as a slurry precursor is ejected by using liquid supply pump  13  and pressure booster  14 , advanced atomization with the use of the slurry producing apparatus is difficult. 
     The present invention has been made to solve such problems, and an object of the present invention is to provide a wet atomization apparatus, with a reduced size and a simple structure, and a wet atomization method both capable of advanced atomization of particles contained in a process-target fluid. 
     Solution to Problem 
     To achieve the above object, the invention of claim  1  is configured as a wet atomization apparatus for atomizing particles contained in a process-target fluid. The wet atomization apparatus includes a process-target fluid storing container for storing the process-target fluid; a syringe including a gasket configured to be slid on an inner peripheral wall of the syringe by a plunger; a thin tube having one end inserted in the process-target fluid storing container and another end connected to the syringe; and a control section that performs control of the plunger to move forward and backward, wherein under the control by the control section, an atomization process is performed at least once in which the plunger is moved backward to allow the process-target fluid in the process-target fluid storing container to flow into the syringe via the thin tube so as to be stored in the syringe and the plunger is moved forward to return the process-target fluid stored in the syringe into the process-target fluid storing container via the thin tube. 
     In the invention of claim  1 , the invention of claim  2  is configured such that the thin tube is detachably connected to the syringe. 
     In the invention of claim  1  or  2 , the invention of claim  3  is configured such that a diameter of the thin tube is determined according to the particle size of the particles contained in the fluid process-target fluid. 
     In the invention of claim  1  or  2 , the invention of claim  4  is configured such that a length of the thin tube is determined according to the particle size of the particles contained in the process-target fluid and a desired atomization degree. 
     In the invention of any one of claims  1  to  4 , the invention of claim  5  is configured such that the control section controls a speed of the process-target fluid extruded via the thin tube by the plunger in such a way that the flow of the process-target fluid in the thin tube becomes turbulent, and controls the number of times the atomization process is performed by a reciprocating operation of the plunger to a predetermined number of times. 
     The invention of claim  6  is configured as a wet atomization method for atomizing particles contained in a process-target fluid. The wet atomization method includes: inserting one end of a thin tube into a process-target fluid storing container for storing the process-target fluid; connecting another end of the thin tube to a syringe including a gasket configured to be slid on an inner peripheral wall of the syringe by a plunger; and performing an atomization process at least once in which the plunger is moved backward to allow the process-target fluid in the process-target fluid storing container to flow into the syringe via the thin tube so as to be stored in the syringe and the plunger is moved forward to return the process-target fluid stored in the syringe into the process-target fluid storing container via the thin tube. 
     In the invention of claim  6 , the invention of claim  7  is configured such that the thin tube is detachably connected to the syringe. 
     In the invention of claim  6  or  7 , the invention of claim  8  is configured such that a diameter of the thin tube is determined according to the particle size of the particles contained in the fluid process-target fluid. 
     In the invention of claim  6  or  7 , the invention of claim  9  is configured such that a length of the thin tube is determined according to the particle size of the particles contained in the process-target fluid and a desired atomization degree. 
     In the invention of any one of claims  6  to  9 , the invention of claim  10  is configured such that a speed of the process-target fluid extruded via the thin tube by the plunger is controlled in such a way that a flow of the process-target fluid in the thin tube becomes turbulent, and the number of times the atomization process is performed by a reciprocating operation of the plunger is controlled to a predetermined number of times. 
     Advantageous Effects of Invention 
     The present invention is configured as a wet atomization apparatus for atomizing particles contained in a process-target fluid. The wet atomization apparatus includes a process-target fluid storing container for storing the process-target fluid; a syringe including a gasket configured to be slid on an inner peripheral wall of the syringe by a plunger; a thin tube with one end inserted in the process-target fluid storing container and the other end connected to the syringe; and a control section that performs control of the plunger to move forward and backward. In the wet atomization apparatus, an atomization process is performed at least once, and in the atomization process, by the control performed by the control section, the plunger is moved backward to allow the process-target fluid in the process-target fluid storing container to flow into the syringe via the thin tube so as to be stored in the syringe, and the plunger is moved forward to return the process-target fluid stored in the syringe into the process-target fluid storing container via the thin tube. Therefore, the invention has the effects that allows the provision of a wet atomization apparatus, with a reduced size and a simple structure, and a wet atomization method both capable of advanced atomization of particles contained in a process-target fluid. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a side view of a wet atomization apparatus of an example according to the present invention; 
         FIG.  2    is a front view of the wet atomization apparatus illustrated in  FIG.  1   ; 
         FIG.  3    is a side view of the wet atomization apparatus illustrated in  FIG.  1    at the start of its operation; 
         FIGS.  4 A to  4 C  are diagrams explaining the operation of the wet atomization apparatus illustrated in  FIG.  1   ; 
         FIGS.  5 A and  5 B  are diagrams explaining the operating principle of the wet atomization apparatus illustrated in  FIG.  1   ; 
         FIG.  6    is a flowchart explaining an exemplary operation of the wet atomization apparatus according to the present invention; and 
         FIG.  7    is a graph in which the decrease of the particle size (size/nm) with respect to the number of times (step number) the atomization process is performed by the forward and backward movement control of actuator  23  is plotted with the use of thin tube  30  having a diameter of 0.762 mm and a length of 65 cm, and of calcium carbonate particles/SOFTANOL aqueous solution having a calcium carbonate concentration of 0.1 mg/ml and a SOFTANOL concentration of 0.05 mg/ml as a process-target fluid. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, at least one example of the present invention will be described in detail with reference to the drawings attached to the application. 
       FIG.  1    is a side view of a wet atomization apparatus of an example according to the present invention.  FIG.  2    is a front view of the wet atomization apparatus illustrated in  FIG.  1   .  FIG.  3    is a side view of the wet atomization apparatus illustrated in  FIG.  1    at the start of its operation. 
     Wet atomization apparatus  100  of the present example in  FIGS.  1  to  3    atomizes the particles contained in a process-target fluid stored in process-target fluid storing container  10 . Wet atomization apparatus  100  can be used alone, but can also be used, for example, as a particle atomization apparatus before a well-known jet mill. 
     Syringe  20  includes gasket  22  that slides on the inner peripheral wall of the syringe. Gasket  22  is operated so as to be slid forward and backward by plunger  21  connected to gasket  22 . 
     Thin tube  30  is detachably connected to one end of syringe  20  via adapter  31 . The distal end of thin tube  30  is inserted into process-target fluid storing container  10  as illustrated in  FIGS.  1  to  3    when a process-target fluid stored in the process-target fluid storing container  10  is subjected to an atomization process. 
     One end of plunger  21 , which moves gasket  22  forward and backward, is connected to gasket  22 , and the other end of plunger  21  is connected to actuator  23  that is controlled to move forward and backward by ball screw  420  of control section  40 . 
     Ball screw  420  is driven by motor  410 . That is, first pulley  412  is attached to rotating shaft  411  of motor  410 , and second pulley  421  is attached to one end of ball screw  420 . Belt  430  is contained between first pulley  412  and second pulley  421 . 
     As illustrated in  FIG.  2   , two linear guides  440   a  and  440   b  for guiding actuator  23  are respectively provided on both sides of ball screw  420 . 
     When motor  410  rotates in the normal direction, the rotation of motor  410  is transmitted to ball screw  420  via first pulley  412 , belt  430 , and second pulley  421 . The resulting normal rotation of ball screw  420  causes actuator  23  to move downward, and plunger  21  pushes gasket  22  in syringe  20  downward accordingly, moving gasket  22  forward in syringe  20 . 
     When motor  410  rotates in the reverse direction, the rotation of motor  410  is transmitted to ball screw  420  via first pulley  412 , belt  430 , and second pulley  421 . The resulting reverse rotation of ball screw  420  causes actuator  23  to move upward, and plunger  21  moves gasket  22  in syringe  20  upward accordingly, moving gasket  22  backward in syringe  20 . 
     As described above, thin tube  30  is connected to one end of syringe  20 , and the distal end of thin tube  30  is inserted in process-target fluid storing container  10 . Therefore, when gasket  22  moves backward in syringe  20  due to the upward movement of actuator  23 , a process-target fluid in process-target fluid storing container  10  is introduced into syringe  20  via thin tube  30 .  FIGS.  1  and  2    illustrate this state. 
     From this state, when actuator  23  moves downward to push gasket  22  down in syringe  20 , the process-target fluid in gasket  22  flows through thin tube  30  at a predetermined speed and returns into process-target fluid storing container  10 . 
     In wet atomization apparatus  100  of the present example, particles contained in a process-target fluid stored in process-target fluid storing container  10  are atomized by utilizing the flow of the process-target fluid in thin tube  30  caused by the forward movement of gasket  22  in syringe  20 . 
     Next, the details of the atomization process will be described with reference to  FIGS.  4 A to  5 B . 
     As described above, wet atomization apparatus  100  of the present example performs the atomization process with the use of syringe  20 . In the atomization process, particles contained in a process-target fluid stored in process-target fluid storing container  10  are atomized by utilizing the flow of the process-target fluid formed in thin tube  30 . 
       FIGS.  4 A to  4 C  are diagrams explaining the operation of the wet atomization apparatus illustrated in  FIG.  1   .  FIGS.  5 A and  5 B  are diagrams explaining the operating principle of the wet atomization apparatus illustrated in  FIG.  1   . 
       FIG.  4 A  illustrates the state of syringe  20  at the start of the atomization process. In the state illustrated in  FIG.  4 A , the process-target fluid is stored in process-target fluid storing container  10 . 
     From this state, when actuator  23  is moved upward to move gasket  22  in syringe  20  backward, the process-target fluid in process-target fluid storing container  10  passes through thin tube  30  to move into syringe  20  as illustrated in  FIG.  4 B . 
     When actuator  23  is then moved downward to move gasket  22  in syringe  20  forward, the process-target fluid in syringe  20  is introduced into thin tube  30  and forms a flow of the process-target fluid in thin tube  30  as illustrated in  FIG.  4 C . 
       FIGS.  5 A and  5 B  schematically illustrate the velocity distribution of the flow of a process-target fluid formed in thin tube  30 .  FIG.  5 A  illustrates the case of V 1  in which the flow of the process-target fluid in thin tube  30  is relatively slow, and  FIG.  5 B  illustrates the case of V 2  in which the flow of the process-target fluid in thin tube  30  is relatively fast. 
     As is clear from  FIG.  5 A , the speed difference between the part near the side wall of thin tube  30  and the central part of thin tube  30  is not large in the case of V 1  in which the flow of the process-target fluid in thin tube  30  is relatively slow. In this case, the flow of the process-target fluid in thin tube  30  is considered to be a laminar flow. On the other hand, as illustrated in  FIG.  5 B , the speed difference between the part near the side wall of thin tube  30  and the central part of thin tube  30  increases in the case of V 2  in which the flow of the process-target fluid in thin tube  30  is relatively fast. In this case, the flow of the process-target fluid in thin tube  30  is considered to be a turbulent flow. 
     When the flow of the process-target fluid in thin tube  30  becomes turbulent, the probability of collision between particles contained in the process-target fluid in thin tube  30  increases dramatically, possibly enabling highly efficient atomization of the particles contained in the process-target fluid in thin tube  30 . 
     When actuator  23  reaches the lower limit position, that is, the state illustrated in  FIG.  4 A , one atomization process is completed. This atomization process is repeated until a desired satisfactory atomization degree is obtained. 
     The diameter of thin tube  30  should be set according to the diameter of the particles contained in a process-target fluid in order to enable highly efficient atomization of the particles in thin tube  30 . 
     The diameter of thin tube  30  should be set to a diameter smaller than the maximum diameter of the particles contained in the process-target fluid in order to enable highly efficient atomization of the particles in thin tube  30 . 
     As for the length of thin tube  30 , it is considered that the longer the length of thin tube  30  becomes, the higher the efficiency of atomization of the particles in thin tube  30  becomes. It is thus preferable to determine the length according to the diameter of the particles and the desired atomization degree. 
     There are also an optimum speed of flow of the process-target fluid in thin tube  30  and an optimum number of times the atomization process is performed in order to enable highly efficient atomization of particles contained in the process-target fluid in thin tube  30 . 
     For the highly efficient atomization, the wet atomization apparatus of the present invention employs the following configurations. 
     1) As thin tubes  30 , a plurality of thin tubes is prepared according to the particle size of particles contained in the process-target fluid, which is to be stored in process-target fluid storing container  10 , and adapter  31  is used for detachably connecting these thin tubes to syringe  20  individually. 
     2) The diameter of thin tube  30  to be connected to syringe  20  is determined according to the particle size of the particles contained in the process-target fluid. 
     3) The length of thin tube  30  to be connected to syringe  20  is determined according to the particle size of the particles contained in the process-target fluid and the desired atomization degree. 
     4) The flow velocity of the process-target fluid flowing in thin tube  30  is controlled in such a way that the flow of the process-target fluid becomes turbulent. 
     5) The number of times the atomization process is performed by the forward and backward movement of gasket  22  in syringe  20  is controlled to a predetermined number of times according to the desired atomization degree. 
       FIG.  6    is a flowchart explaining an exemplary operation of the wet atomization apparatus according to the present invention. 
     In  FIG.  6   , from the state illustrated in  FIG.  4 A , which is the starting point of the atomization process according to the present invention, motor  410  is rotated in the reverse direction (step  601 ). Due to the reverse rotation of motor  410 , actuator  23  moves upward, and accordingly, plunger  21  moves gasket  22  in syringe  20  upward, that is, gasket  22  is moved backward in syringe  20 . As a result, the process-target fluid in process-target fluid storing container  10  is introduced into syringe  20  through thin tube  30 . 
     Whether or not actuator  23  reaches the upper limit position is then checked (step  602 ), and when actuator  23  does not reach the upper limit position (NO in step  602 ), the processing returns to step  601  and the reverse rotation of motor  410  is continued. 
     When it is determined in step  602  that actuator  23  reaches the upper limit position, that is, reaches the state illustrated in  FIG.  4 B  (YES in step  602 ), motor  410  is controlled to rotate in the normal direction (step  603 ). Due to the control of motor  410  to rotate in the normal direction, actuator  23  moves downward to push gasket  22  down in syringe  20 , that is, in the state illustrated in  FIG.  4 C . From this state, the process-target fluid in gasket  22  is returned into process-target fluid storing container  10  at a predetermined speed through thin tube  30 , thereby atomizing the particles contained in the process-target fluid. 
     Whether or not actuator  23  reaches the lower limit position is then checked (step  604 ), and when actuator  23  does not reach the lower limit position (NO in step  604 ), the processing returns to step  603  and the normal rotation of motor  410  is continued. When it is determined in step  604  that actuator  23  reaches the lower limit position, that is, reaches the state illustrated in  FIG.  4 A  (YES in step  604 ), then checked is whether or not the number of times the atomization process is performed by the control of actuator  23  to move forward and backward (herein also simply referred to as “forward and backward movement control of actuator  23 ”) reaches a predetermined number (set value) set in advance (step  605 ). 
     When the number of times the atomization process is performed by the forward and backward movement control of actuator  23  does not reach the predetermined set value set in advance (NO in step  605 ), the processing returns to step  601 , and the processing from steps  601  to  605  is repeated. When it is determined in step  605  that the number of times the atomization process is performed by the forward and backward movement control of actuator  23  reaches the predetermined set value set in advance (YES in step  605 ), the atomization process is terminated. 
     In the following, an example of actual atomization of particles by the above-described atomization processing method will be described. 
     In the present example, the atomization process of calcium carbonate particles is performed with the use of thin tube  30  having a diameter of 0.762 mm and a length of 65 cm, and of calcium carbonate particles/SOFTANOL aqueous solution having a calcium carbonate concentration of 0.1 mg/ml and a SOFTANOL concentration of 0.05 mg/ml as a process-target fluid. 
       FIG.  7    is a graph in which the decrease of the particle size (size/nm) with respect to the number of times (step number) the atomization process is performed by the forward and backward movement control of actuator  23  is plotted. 
       FIG.  7    clearly shows that the particle size (size/nm) gradually decreases as the number of times (step number) the atomization process is performed by the forward and backward movement control of actuator  23  increases. 
     In the above embodiment, a configuration of a single syringe system with one syringe is used. Such a configuration may employ a double syringe system with two syringes or a multi-syringe system with three or more syringes. 
     The reasons for employing the double syringe system or a multi-syringe system are as follows: with a single syringe, atomization may take longer time when the amount of process-target fluid is large; and when the particle size of particles contained in the process-target fluid is large, it is necessary to replace the thin tube with another thin tube having a different diameter and length for the desired atomization. 
     Employing the double syringe system or a multi-syringe system can shorten the time for the desired atomization of the process-target fluid. In addition, in the configuration in which two or more syringes connecting thin tubes of different diameters and lengths are provided, and the atomization process is performed by alternately using the plurality of syringes, continuously performing of the atomization process becomes possible without replacing the thin tube. 
     One example of the present invention is described above; however, the present invention is not limited to the above-described example. Within the scope of the technical idea of the present invention, many modifications are possible from ordinary creative ability of a person skilled in the art. 
     REFERENCE SIGNS LIST 
     
         
           10  Process-target fluid storing container 
           20  Syringe 
           21  Plunger 
           22  Gasket 
           23  Actuator 
           30  Thin tube 
           31  Adapter 
           32  Second pulley 
           33  Nut part 
           40  Control section 
           410  Motor 
           411  Rotating shaft 
           412  First pulley 
           420  Ball screw 
           421  Second pulley 
           430  Belt 
           440   a,    440   b  Linear guide 
           100  Wet atomization apparatus