Patent Publication Number: US-2023149951-A1

Title: Separation device and separation system

Description:
TECHNICAL FIELD 
     The present disclosure relates to separation devices and separation systems, and specifically, to a separation device for separating solid substances contained in a gas from the gas and a separation system including the separation device. 
     BACKGROUND ART 
     Conventionally, known as a separation device is a centrifuge including a chamber having a cylindrical confinement wall and a driving rotor having a plurality of blades fixed to a shaft (Patent Literature 1). 
     The cylindrical confinement wall surrounds the shaft and is disposed coaxially with the shaft. Each blade is disposed between the shaft and the cylindrical confinement wall and is coupled to the shaft. Here, the cylindrical confinement wall has an inlet opening (inlet), and an outlet opening (outlet), and a removal opening (discharge port). The removal opening is located closer to the outlet opening than to the inlet opening. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: U.S. Pat. No. 5,149,345 A 
     SUMMARY OF INVENTION 
     Separation devices are desired to be improved in their separative performance of separating solid substances contained in a gas from the gas. 
     It is an object of the present disclosure to provide a separation device and a separation system which are configured to improve separative performance of separating solid substances contained in a gas from the gas. 
     A separation device according to an aspect of the present disclosure includes a casing, a rotor, and a blade. The casing has a gas inlet, a gas outlet, and a solid substance discharge port. The rotor is disposed inside the casing. The rotor is rotatable around a rotation central axis extending along an axial direction of the casing. The blade is disposed between the casing and the rotor. The blade is configured to rotate together with the rotor. The blade has a first end adjacent to the gas inlet and a second end adjacent to the gas outlet. The casing has a space extending to the solid substance discharge port with respect to the second end of the blade in the axial direction. The separation device further includes a separating wall. The separating wall separates the space into a first region on an inner side and a second region on an outer side when viewed in the axial direction of the casing. 
     A separation system according to an aspect of the present disclosure includes the separation device and a driving device. The driving device is configured to rotationally drive the rotor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a separation device according to an embodiment; 
         FIG.  2    is a sectional view of the separation device, wherein an external cover is mounted on the separation device, and a rotation central axis is shown in this sectional view; 
         FIG.  3    is a cross-section view of the separation device, wherein this cross-section view corresponds to a cross-section surface along line III-III of  FIG.  2   ; 
         FIG.  4    is a cross-section view of the separation device, wherein this cross-section view corresponds to a cross-section surface along line IV-IV of  FIG.  2   ; 
         FIG.  5    is a schematic configuration diagram of a separation system including the separation device; 
         FIG.  6    is a view of a simulation result of pressure distribution inside a casing of the separation device; 
         FIG.  7    is a view of a simulation result of a trajectory of a particle with the separation device; 
         FIG.  8    is a view of a simulation result of a trajectory of another particle with the separation device; and 
         FIG.  9    is a sectional view of a separation device of a first variation of the embodiment, wherein an external cover is mounted on the separation device, and a rotation central axis is shown in this sectional view. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A separation device and a separation system according to an embodiment will be described below with reference to the drawings. Note that the embodiment to be described below is a mere example of various embodiments of the present disclosure. Rather, the embodiment to be described below may be readily modified in various manners depending on a design choice or any other factor without departing from the scope of the present disclosure. The drawings to be referred to in the following description of the embodiment are all schematic representations. Thus, the ratio of the dimensions (including thicknesses) of respective constituent elements illustrated on the drawings does not always reflect their actual dimensional ratio. 
     (1) Overview 
     The separation device  1  is provided on an upstream side of, for example, an air conditioning facility having an air blowing function and is configured to separate solid substances in air (gas). The separation device  1  is installed on a rooftop of a facility (e.g., a dwelling house) having a flat roof or on ground. The air conditioning facility is, for example, an air blowing device configured to blow air from the upstream side to a downstream side. The air blowing device is, for example, an electric fan. The air conditioning facility is not limited to the air blowing device but may be, for example, a ventilating device, an air conditioner, an air supply cabinet fan, or an air conditioning system including an air blowing device and a heat exchanger. The flow rate of air caused by the air conditioning facility to flow to the separation device  1  is, for example, 50 m 3 /h to 500 m 3 /h. The outflow volume of air from the separation device  1  toward the air conditioning facility is substantially equal to the flow rate of air flowing through the air conditioning facility. 
     As shown in  FIGS.  1  to  4   , the separation device  1  includes a casing  2 , a rotor  3 , and blades  4 . Moreover, a separation system  10  includes the separation device  1  and a driving device  11  as shown in  FIG.  5   . 
     The casing  2  includes a gas inlet  21 , a gas outlet  22 , and a solid substance discharge port  23 . The rotor  3  is disposed inside the casing  2 . The rotor  3  is rotatable around a rotation central axis  30  extending along an axial direction D 1  of the casing  2 . The blades  4  are disposed between the casing  2  and the rotor  3 . The blades  4  rotate together with the rotor  3 . Each blade  4  has a first end  41  adjacent to the gas inlet  21  and a second end  42  adjacent to the gas outlet  22 . The casing  2  has a space  25  extending to the solid substance discharge port  23  with respect to the second ends  42  of the blades  4  in the axial direction D 1  of the casing  2 . 
     The solid substance discharge port  23  is a hole for discharging solid substances contained in, for example, air to an outside of the casing  2 . The solid substance discharge port  23  connects an inside space of the casing  2  and an outside space of the casing  2  to each other. In other words, the inside and the outside of the casing  2  are in communicative connection with each other via the solid substance discharge port  23 . The separation device  1  generates, in the casing  2 , an airflow swirling in the casing  2  when the rotor  3  rotates. In the separation device  1 , part of a flow path from the gas inlet  21  toward the gas outlet  22  is formed between the casing  2  and the rotor  3 . 
     The separation device  1  further includes a separating wall  5 . The separating wall  5  is disposed in the space  25 . The separating wall  5  separates the space  25  into a first region R 1  on the inner side and a second region R 2  on the outer side when viewed in the axial direction D 1  of the casing  2 . 
     The separation device  1  is configured to cause air flowing from the upstream side into the casing  2  to flow to the downstream side while the separation device  1  helically rotates the air around the rotor  3 . In the present embodiment, “upstream side” means a side (primary side) from which an arrow representing an air-flowing direction is directed. Moreover, “downstream side” means a side (secondary side) to which the arrow representing the air-flowing direction is directed. The separation device  1  is used, for example, in a posture where the gas outlet  22  is located above the gas inlet  21 . In this case, the separation device  1  is configured such that air flowing through the gas inlet  21  formed in the casing  2  into the flow path is caused to helically rotate around the rotor  3  to move to the gas outlet  22 . 
     The separation device  1  has the solid substance discharge port  23  in order to discharge the solid substances contained in the air flowing in the casing  2  to the outside of the casing  2 . Thus, at least some of the solid substances contained in the air flowing in the casing  2  through the gas inlet  21  of the casing  2  are discharged to the outside of the casing  2  through the solid substance discharge port  23  in the course of passing through the flow path. 
     Moreover, the separation system  10  includes the driving device  11  in addition to the separation device  1  as described above. The driving device  11  rotationally drives the rotor  3 . That is, the driving device  11  rotates the rotor  3  around the rotation central axis  30 . The driving device  11  includes, for example, a motor. 
     Examples of the solid substances in the air include fine particles and dust. Examples of the fine particles include particulate matter. Examples of the particulate matter include primary particles emitted directly to air as fine particles and secondary particles emitted to the air as a gas and formed into fine particles in the air. Examples of the primary particles include soil particles (e.g., yellow dust), powder dust, vegetal-origin particles (e.g., pollen), animal-origin particles (e.g., spores of mold), and soot. Examples of the particulate matter include PM1.0 and PM2.5 (fine particulate matters), PM10, and SPM (suspended particulate matter) classified based on their sizes. PM1.0 refers to fine particles passing through a sizing device with a collection efficiency of 50% at a particle size of 1.0 μm. PM2.5 refers to fine particles passing through a sizing device with a collection efficiency of 50% at a particle size of 2.5 μm. PM10 refers to fine particles passing through a sizing device with a collection efficiency of 50% at a particle size of 10 μm. SPM refers to fine particles passing through a sizing device with a collection efficiency of 100% at a particle size of 10 μm, and SPM corresponds to PM6.5 to PM7.0 and refers to fine particles slightly smaller than PM10. 
     (2) Details 
     As described above, the separation device  1  includes the casing  2 , the rotor  3 , the blades  4 , and the separating wall  5 . As shown in  FIGS.  1  and  2   , the separation device  1  further includes an outlet tubular part  6 , a rectifying structure  8 , and a structure  9 . Moreover, the separation system  10  includes the separation device  1 , the driving device  11 , and a control device  12 . 
     A material for the casing  2  is, for example, but is not limited to, metal but may be a resin (e.g., ABS resin). Moreover, the casing  2  may include a metal part made of metal and a resin part made of a resin. 
     The casing  2  includes: a tubular part  20  having a first end  201  and second end  202 ; and a bottom part  24  which closes an opening of the second end  202  of the tubular part  20 . In the separation device  1  according to the embodiment, the casing  2  has a bottomed tubular shape. The axial direction D 1  of the casing  2  is a direction along the central axis of the tubular part  20 . 
     The tubular part  20  has a small diameter portion  211 , an expanding diameter portion  212 , and a large diameter portion  213 . In the tubular part  20 , the small diameter portion  211 , the expanding diameter portion  212 , and the large diameter portion  213  are arranged in this order in the axial direction D 1  of the casing  2 . In the tubular part  20 , the small diameter portion  211  has the gas inlet  21 . The large diameter portion  213  has the gas outlet  22  and the solid substance discharge port  23 . The gas inlet  21 , the gas outlet  22 , and the solid substance discharge port  23  are open at lateral sides of the casing  2 . In the axial direction D 1  of the casing  2 , the gas inlet  21 , the solid substance discharge port  23 , and the gas outlet  22  are arranged in this order. On one plane orthogonal to the axial direction D 1  of the casing  2 , a part (downstream end) of the solid substance discharge port  23  overlaps the gas outlet  22  (see  FIG.  4   ). 
     The small diameter portion  211  has the gas inlet  21 . The small diameter portion  211  is in the shape of a cylinder having both bottom surfaces which are open. The gas inlet  21  is formed in a side surface of the small diameter portion  211 . The gas inlet  21  is formed in the small diameter portion  211  near a bottom part  2111  of the small diameter portion  211 . 
     The casing  2  includes a plurality of gas inlets  21 . Each gas inlet  21  is substantially ¼ arc shape. 
     The large diameter portion  213  is in the shape of a cylinder having both ends which are open. The large diameter portion  213  surrounds the rotor  3 . In the axial direction D 1  of the casing  2  (axial direction of the large diameter portion  213 ), the length of the large diameter portion  213  is longer than the length of the rotor  3 . The inner diameter and the outer diameter of the large diameter portion  213  are uniform over the entire axial length of the large diameter portion  213 . The outer diameter and the inner diameter of the large diameter portion  213  are respectively larger than the outer diameter and the inner diameter of the small diameter portion  211 . 
     The solid substance discharge port  23  is formed in an outer peripheral surface  27  of the casing  2  (here, an outer peripheral surface of the large diameter portion  213 ). The solid substance discharge port  23  is formed as a slit extending along the axial direction of the large diameter portion  213  (axial direction D 1  of the casing  2 ). The solid substance discharge port  23  is formed in a portion of the large diameter portion  213 , the portion corresponding to the space  25 . 
     The solid substance discharge port  23  is apart from the gas inlet  21  in the axial direction D 1  of the casing  2  and is in communicative connection with the inside and outside of the tubular part  20  (large diameter portion  213 ) between the first end  201  and the second end  202  of the tubular part  20 . The solid substance discharge port  23  extends in a direction along one tangential direction of an inner peripheral surface  26  of the casing  2  (an inner peripheral surface of the large diameter portion  213 ) when viewed in the axial direction D 1  of the casing  2 . Here, the one tangential direction is a direction along a rotation direction A 1  (see  FIGS.  3  and  4   ) of the rotor  3 . 
     More specifically, the inner surface of the solid substance discharge port  23  has, as shown in  FIGS.  3  and  4   , an inner front surface  232  located frontward and an inner rear surface  231  located rearward in a direction along the rotation direction A 1  of the rotor  3 . 
     The inner rear surface  231  is connected to the inner peripheral surface  26  of the casing  2  (the inner peripheral surface of the large diameter portion  213 ). The inner rear surface  231  has an outer end P 12  away from the rotor  3  and an inner end P 11  near to the rotor  3 . The outer end P 12  is located frontward of the inner end P 11  in the rotation direction A 1 . In a cross-section orthogonal to the axial direction D 1  of the casing  2 , the inner rear surface  231  extends in a tangential direction of the inner peripheral surface  26  at the inner end P 11  of the inner rear surface  231 . 
     The inner front surface  232  has an outer end P 22  away from the rotor  3  and an inner end P 21  near to the rotor  3 . The outer end P 22  is located frontward of the inner end P 21  in the rotation direction A 1 . In short, in the separation device  1 , the solid substance discharge port  23  in the casing  2  has the inner rear surface  231  and the inner front surface  232  respectively located rearward and frontward in the rotational direction A 1  of the rotor  3 . In a cross-section orthogonal to the axial direction D 1  of the casing  2 , the inner front surface  232  is substantially parallel to the inner rear surface  231 . 
     The casing  2  (large diameter portion  213 ) has a plurality of (in the illustrated example, two) solid substance discharge ports  23 . The two solid substance discharge ports  23  are on opposite sides of the outer peripheral surface of the large diameter portion  213 . In the separation device  1 , solid substances passing in the vicinity of the inner peripheral surface  26  of the casing  2  (here, an inner peripheral surface of the large diameter portion  213 ) can be discharged through the solid substance discharge ports  23 . 
     The separation device  1  includes a guide wall  28 . The guide wall  28  are provided on the casing  2 . The separation device  1  includes a plurality of (in the example shown in the figure, two) guide walls  28 . The two guide walls  28  correspond to the two solid substance discharge ports  23  on a one-to-one basis. 
     Each guide wall  28  extends from the inner peripheral surface  26  of the casing  2  inward of the casing  2 . One surface of each guide wall  28  is flush with the inner front surface  232  of the solid substance discharge port  23 . Each guide wall  28  extends along the inner front surface  232  of the solid substance discharge port  23  from the inner peripheral surface  26  of the casing  2  to one center line of the casing  2  (one center line of the large diameter portion  213 ; shown by long dashed short dashed line in  FIGS.  3  and  4   ). The one center line is orthogonal to the rotation central axis  30  of the rotor  3  and is orthogonal to the one tangential direction. 
     The large diameter portion  213  has the gas outlet  22 . The gas outlet  22  is formed in a side surface of the large diameter portion  213 . The gas outlet  22  is formed near the bottom part  24  of the large diameter portion  213 . The gas outlet  22  is apart from the gas inlet  21  in the axial direction D 1  of the casing  2  and is in communicative connection with the inside and the outside of the tubular part  20  (large diameter portion  213 ) between the first end  201  and the second end  202  of the tubular part  20 . The gas outlet  22  is adjacent to one solid substance discharge port  23  of the two solid substance discharge ports  23 . The gas outlet  22  is located frontward of the solid substance discharge ports  23  adjacent thereto in the rotational direction A 1  (see  FIGS.  3  and  4   ) of the rotor  3 . 
     The expanding diameter portion  212  is connected between the small diameter portion  211  and the large diameter portion  213 . The expanding diameter portion  212  has a first end adjacent to the small diameter portion  211  and a second end adjacent to the large diameter portion  213 . The first end of the expanding diameter portion  212  is connected to the small diameter portion  211 . The inner space of the expanding diameter portion  212  is communicated with the inner space of the small diameter portion  211 . The second end of the expanding diameter portion  212  is connected to the large diameter portion  213 . The inner space of the expanding diameter portion  212  is communicated with the inner space of the large diameter portion  213 . The expanding diameter portion  212  has a taper cylindrical shape of which the outer diameter and the inner diameter gradually increase toward the large diameter portion  213  as the distance from the small diameter portion  211  increases in the axial direction D 1  of the casing  2 . The outer diameter and the inner diameter of the expanding diameter portion  212  at the end adjacent to the small diameter portion  211  in the axial direction D 1  of the casing  2  are respectively the same as the outer diameter and the inner diameter of the small diameter portion  211 . The outer diameter and the inner diameter of the expanding diameter portion  212  at the end adjacent to the large diameter portion  213  in the axial direction D 1  of the casing  2  are respectively the same as the outer diameter and the inner diameter of the large diameter portion  213 . That is, the opening area of the expanding diameter portion  212  gradually increases as the distance from the gas inlet  21  increases in the axial direction D 1  of the casing  2 . 
     The outlet tubular part  6  is connected to the casing  2 . The outlet tubular part  6  is, for example, connected to the gas outlet  22  at the outer peripheral surface  27  of the casing  2  (large diameter portion  213 ). The outlet tubular part  6  has an inner space  60  that is communicated with the inner space of the tubular part  20  (the inner space of the large diameter portion  213 ) via the gas outlet  22 . 
     The outlet tubular part  6  is a duct for feeding the gas from which solid substances have been separated to the outside of the casing  2 . The outlet tubular part  6  extends, from the outer peripheral surface  27  of the casing  2 , in a direction intersecting with each of a radial direction of the casing  2  at a position where the gas outlet  22  is provided and the axial direction D 1  of the casing  2 , when viewed in the axial direction D 1  of the casing  2 . The outlet tubular part  6  has a rectangular tubular shape. In the outlet tubular part  6 , an opening on an opposite side of the outlet tubular part  6  from the gas outlet  22  has a square shape, but the shape of the opening is not limited to this example. 
     The rotor  3  is disposed inside the casing  2  coaxially with the casing  2 . Saying “disposed coaxially with the casing  2 ” means that the rotor  3  is disposed such that the rotation central axis  30  (see  FIG.  2   ) of the rotor  3  coincides with the central axis  29  of the casing  2  (central axis of the large diameter portion  213 ). Examples of a material for the rotor  3  include a polycarbonate resin. 
     In a direction along the rotation central axis  30  of the rotor  3 , the rotor  3  has a length shorter than the length of the large diameter portion  213  in the axial direction D 1  of the casing  2 . 
     The rotor  3  has, for example, a circular truncated cone shape. The rotor  3  has a first end  31  adjacent to the gas inlet  21  and a second end  32  adjacent to the gas outlet  22 . The rotor  3  has a circular truncated cone shape whose diameter gradually increases from the first end  31  toward the second end  32 . The rotor  3  is disposed in the large diameter portion  213  in the vicinity of the expanding diameter portion  212  in the axial direction of the casing  2 . 
     In the separation device  1 , a plurality of (here, 24) blades  4  are disposed between the casing  2  and the rotor  3 . That is, the separation device  1  includes the plurality of blades  4 . In the separation device  1 , the plurality of blades  4  are disposed between the casing  2  and the rotor  3 . The plurality of blades  4  are connected to (coupled to) the rotor  3  and are apart from the casing  2 . The plurality of blades  4  rotate together with the rotor  3 . 
     The plurality of blades  4  are provided to the rotor  3  over the entire length of the rotor  3  in a direction along the axial direction D 1  of the casing  2 . That is, the plurality of blades  4  are provided from the first end  31  to the second end  32  of the rotor  3 . Examples of a material for the plurality of blades  4  include a polycarbonate resin. In the separation device  1 , the same material is adopted for the rotor  3  and the plurality of blades  4 , but this should not be construed as limiting the disclosure. The material for the rotor  3  and the material for the plurality of blades  4  may be different from each other. The plurality of blades  4  may be formed integrally with the rotor  3 , or each of the plurality of blades  4  may be formed as members separated from the rotor  3  and may be fixed to the rotor  3 , thereby being connected to the rotor  3 . 
     Each of the plurality of blades  4  is disposed such that a gap is formed between each blade  4  and the casing  2  when viewed in the axial direction D 1  of the casing  2 . In other words, the separation device  1  has a gap between each of the plurality of blades  4  and the inner peripheral surface  26  of the casing  2 . In the radial direction of the rotor  3 , the distance between a protruding tip end of each of the plurality of blades  4  and an outer peripheral surface  37  of the rotor  3  is shorter than the distance between the outer peripheral surface  37  of the rotor  3  and the inner peripheral surface  26  of the casing  2 . 
     Each of the plurality of blades  4  is disposed in a space (the flow path) between the outer peripheral surface  37  of the rotor  3  and the inner peripheral surface  26  of the casing  2  to be parallel to the rotation central axis  30  of the rotor  3 . Each of the plurality of blades  4  has a flat plate shape. Each of the plurality of blades  4  has a trapezoidal shape having a height in the direction along the rotation central axis  30  of the rotor  3  viewed in a thickness direction defined with respect to each of the plurality of blades  4 . Each of the plurality of blades  4  is tilted by a prescribed angle (e.g., 45 degrees) to one radial direction of the rotor  3  when viewed form the second end  202  of the tubular part  20  in the direction along the axial direction D 1  of the casing  2 . In this embodiment, each of the plurality of blades  4  has a tip end adjacent to the casing  2  and a base end adjoining the rotor  3 , and the tip end is located rearward of the base end in the rotation direction A 1  (see  FIGS.  3  and  4   ) of the rotor  3  in a protrusion direction from the rotor  3 . That is, in the separation device  1 , each of the plurality of blades  4  is tilted to the one radial direction of the rotor  3  by the prescribed angle (e.g., 45 degrees) in the rotation direction A 1  of the rotor 3. The prescribed angle is not limited to 45 degrees but may be an angle greater than 0 degree and less than or equal to 90 degrees. For example, the prescribed angle may be an angle within a range from 10 degrees to 80 degrees. Each of the plurality of blades  4  is not necessarily tilted with respect to the one radial direction of the rotor  3  by the prescribed angle in the rotation direction A 1  of the rotor  3  but may have, for example, an angle of 0 degree with respect to the one radial direction of the rotor  3 . That is, the plurality of blades  4  may radially extend from the rotor  3 . As illustrated in  FIGS.  3  and  4   , the plurality of blades  4  are disposed to be apart from each other at equal angular intervals in a circumferential direction of the rotor  3 . The “equal angular interval” as used herein is not limited to only the case of a strictly equal angular interval but may be, for example, an angular interval within a prescribed error range (e.g., ±10% of the prescribed angular interval) with respect to a prescribed angular interval. 
     In the axial direction D 1  of the casing  2 , the length of each of the plurality of blades  4  is equal to the length of the rotor  3 . In this embodiment, the length of each of the plurality of blades  4  is not limited to the case of being equal to the length of the rotor  3  but may be longer or shorter than the length of the rotor  3 . 
     In the axial direction D 1  of the casing  2 , the length of each of the plurality of blades  4  is shorter than the length of the tubular part  20 . In the direction along the rotation central axis  30  of the rotor  3 , the length of each of the plurality of blades  4  is shorter than the distance between an end of the large diameter portion  213  at the side of the expanding diameter portion  212  and the solid substance discharge port  23 . 
     Each of the plurality of blades  4  has a first end  41  adjacent to the gas inlet  21  and a second end  42  adjacent to the gas outlet  22  and the solid substance discharge port  23  in the axial direction D 1  of the casing  2 . The first end  41  of each of the plurality of blades  4  is an end (upstream end) adjacent to the first end  201  of the tubular part  20  in the axial direction D 1  of the casing  2 . The second end  42  of each of the plurality of blades  4  is an end (downstream end) adjacent to the second end  202  of the tubular part  20  in the axial direction D 1  of the casing  2 . 
     The casing  2  has the space  25  extending to the solid substance discharge port  23  with respect to the second end  42  of each blade  4  in the axial direction D 1  of the casing  2 . In the separation device  1 , the solid substance discharge port  23  is at a location where the solid substance discharge port  23  overlaps the space  25  in a direction orthogonal to the rotation central axis  30 . That is, the solid substance discharge port  23  is at a location where the solid substance discharge port  23  overlaps the space  25  in the direction orthogonal to the axial direction D 1  of the casing  2 . Moreover, in the separation device  1 , the solid substance discharge port  23  is at a location where the solid substance discharge port  23  does not overlap each blade  4  in the direction orthogonal to the rotation central axis  30 . That is, the solid substance discharge port  23  is at a location where the solid substance discharge port  23  does not overlap each blade  4  in the direction orthogonal to the axial direction D 1  of the casing  2 . In other words, each blade  4  is not in a projection area of the solid substance discharge port  23  when the casing  2  is viewed laterally. 
     In the separation device  1 , the ratio of the length of the space  25  to the sum of the length of each blade  4  and the length of the space  25  in the axial direction D 1  of the tubular part  20  is, for example, greater than or equal to 0.2 and less than or equal to 0.8 and is, for example, 0.55. 
     In the separation device  1 , the structure  9  is disposed in the space  25 . The structure  9  has, for example, a cylindrical shape. The structure  9  is disposed coaxially with the rotor  3 . The structure  9  is connected to the rotor  3 . The structure  9  has a first end  91  and a second end  92  in the axial direction. The first end  91  of the structure  9  is connected to the second end  32  of the rotor  3 . The second end  32  of the structure  9  is farther away from the rotor  3  than the first end  91  is in the axial direction D 1  of the casing  2 . The outer diameter of the structure  9  is equal to the outer diameter of the rotor  3  at the second end  32 . The structural body  9  may be, for example, apart from the rotor  3  and supported by the casing  2  via one or a plurality of beams. The structure  9  may rotate together with the rotor  3  or may rotate independently of the rotor  3 . 
     In the separation device  1 , the space  25  is defined between the casing  2  and the structure  9  at a position between the second end  42  of each blade  4  and the solid substance discharge port  23 . In short, the space  25  in the separation device  1  is defined as an area surrounded by the second end  42  of each blade  4 , the inner peripheral surface  26  of the casing  2 , and an outer peripheral surface of the structural body  9 . 
     The rectifying structure  8  is disposed between the gas inlet  21  and the rotor  3  inside the casing  2  and is configured to rectify a flow of a gas flowing into the casing  2 . The rectifying structure  8  has, for example, a circular truncated cone shape and is disposed inside the expanding diameter portion  212 . The rectifying structure  8  is disposed such that the central axis of the rectifying structure  8  coincides with the central axis  29  of the casing  2 . Thus, in the separation device  1 , the gas flowing through the gas inlet  21  into the casing  2  is easily introduced into a location far from the outer peripheral surface  37  of the rotor  3  and close to the inner peripheral surface  26  of the casing  2  in the radial direction of the rotor  3 . The rectifying structure  8  may be, for example, supported by the casing  2  via one or more beams or may be coupled to the rotor  3 . 
     As described above, the separation device  1  further includes the separating wall  5  disposed in the space  25 . The separating wall  5  has an axis along the axial direction D 1  of the casing  2  and has a tubular shape having openings on both sides in the axial direction of the separating wall  5 . More specifically, the separating wall  5  has a round tubular shape. The separating wall  5  separates the space  25  into the first region R 1  on the inner side and the second region R 2  on the outer side when viewed in the axial direction D 1  of the casing  2 . 
     In the axial direction D 1  of the casing  2 , the length of the separating wall  5  is shorter than the length of the space  25 . In the axial direction D 1  of the casing  2 , the length of the separating wall  5  is shorter than the length of the solid substance discharge port  23 . The separating wall  5  is at a position where the separating wall  5  overlaps the blades  4  in the axial direction D 1  of the casing  2 . 
     The separating wall  5  has a first end  51  adjacent to the gas inlet  21  and a second end  52  adjacent to the gas outlet  22 . In the axial direction D 1  of the casing  2 , a gap (first gap) is provided between the first end  51  of the separating wall  5  and the second end  42  of the blade  4 . In the axial direction D 1  of the casing  2 , a gap (second gap) is provided between the second end  52  of the separating wall  5  and the bottom part  24  of the casing  2 . The first region R 1  and the second region R 2  are in communicative connection with each other via the two gaps (the first gap and the second gap). 
     The inventors of the present application analyzed the airflow in the casing  2  for each of the separation device  1  of the embodiment and a separation device  1  of a comparative example having the same structure as that of the embodiment except that the separating wall  5  is not provided. The airflow in the casing  2  of each of the separation device  1  and the separation device of the comparative example can be inferred from a result of simulation performed by using, for example, fluid analysis software. As the fluid analysis software, for example, ANSYS® Fluent® may be adopted. 
     As the result of the simulation, the inventors of the present application have found that in each of the separation device  1  of the embodiment and the separation device of the comparative example, the velocity vector of the flow velocity of a gas in the space  25  tends to be negative and tends to be positive respectively in a relatively inner region (the first region R 1 ) and in a relatively outer region (the second region R 2 ) in the direction perpendicular to the axial direction D 1  of the casing  2 , where a direction from the gas inlet  21  toward the gas outlet  22  along the axial direction D 1  of the casing  2  is defined as the positive direction. Therefore, in each of the separation device  1  of the embodiment and the separation device of the comparative example, it has been found that when the solid substances (particles) conveyed toward the gas outlet  22  by the airflow directed toward the gas outlet  22  in the relatively outer region are not discharged through the solid substance discharge port  23  before reaching the bottom part  24 , the solid substances (particles) conveyed toward the gas outlet  22  may be by the airflow directed toward the gas inlet  21  in the relatively inner region and may return toward the gas inlet  21 . 
       FIG.  6    shows an example of the result of the simulation by using the fluid analysis software for an airflow in the casing  2  of the separation device  1  of the embodiment. In  FIG.  6   , a region RO shaded with dots in the space  25  shows a region in which for the velocity vector of the flow velocity of a fluid in the casing  2 , the flow velocity is negative, where the direction from the gas inlet  21  toward the gas outlet  22  along the axial direction D 1  of the casing  2  is defined as the positive direction. Further, a region not shaded with dots in the space  25  shows a region in which the velocity vector of the flow velocity is positive. Although illustration is omitted, it has been confirmed that also in the separation device of the comparative example, distribution of velocity vectors of flow velocities in the space  25  is the same as that in  FIG.  6   . 
     As the result of the simulations, it has further been found that in the separation device of the comparative example, solid substances passing through the relatively inner region and returning toward the gas inlet  21  may move relatively outward due to centrifugal force in the course of returning toward the gas inlet  21 , be carried by the air stream, and move toward the gas outlet  22  again. In short, in the separation device of the comparative example, it has been found that when solid substances are not discharged through the solid substance discharge port  23  before reaching the bottom part  24 , the solid substances may reciprocate (vibrate along the axial direction D 1 ) between the gas outlet  22  and the gas inlet  21  in the vicinity of the gas outlet  22 , and may stay in the vicinity of the gas outlet  22 . The solid substances staying in the vicinity of the gas outlet  22  may be discharged through the gas outlet  22  but not through the solid substance discharge port  23 . 
     In contrast, the separation device  1  includes the separating wall  5  disposed in the space  25 . The separating wall  5  separates the space  25  into the first region R 1  on the inner side and the second region R 2  on the outer side when viewed in the axial direction D 1  of the casing  2 . The first region R 1  on the inner side is a region in which for the velocity vector of the flow velocity of a gas in the space  25 , the velocity vector of the flow velocity tends to be negative, where the direction from the gas inlet  21  toward the gas outlet  22  along the axial direction D 1  of the casing  2  is defined as the positive direction. In other words, the first region R 1  is a region in which the gas flows in a direction from the gas outlet  22  toward the gas inlet  21 . The second region R 2  on the outer side is a region in which for the velocity vector of the flow velocity of a gas in the space  25 , the velocity vector of the flow velocity tends to be positive, where the direction from the gas inlet  21  toward the gas outlet  22  along the axial direction D 1  of the casing  2  is defined as the positive direction. In other words, the second region R 2  is a region in which the gas flows in a direction from the gas inlet  21  toward the gas outlet  22 . In short, for the velocity vector of the flow velocity of a gas in the space  25 , a vector obtained by subtracting the velocity vector (the average of velocity vectors) of the flow velocity in the first region R 1  from the velocity vector (the average of velocity vectors) of the flow velocity in the second region R 2  is positive, where the direction from the gas inlet  21  toward the gas outlet  22  along the axial direction D 1  is defined as the positive direction. 
     In the separation device  1 , when solid substances that have not been discharged through the solid substance discharge port  23  before reaching the bottom part  24  return toward the gas inlet  21 , the separating wall  5  prevents the solid substances from moving relatively outward in the course of their returning toward the gas inlet  21 . That is, when solid substances (particles) passing through the second region R 2  and moving toward the gas outlet  22  reach the bottom part  24  and then pass through the first region R 1  to return toward the gas inlet  21 , the separating wall  5  prevents the solid substances from moving from the first region R 1  to the second region R 2  in the course of their returning toward the gas inlet  21 . This reduces the possibility that the solid substances stay in the vicinity of the gas outlet  22  and reduces the possibility that the solid substances are discharged through the gas outlet  22 , thereby improving separative performance of separating solid substances contained in a gas from the gas. 
     Further, in the separation device  1 , the solid substances that have returned to the vicinity of the blades  4  while passing through the first region R 1  move, for example, through the gap (first gap) between the separating wall  5  and the blades  4  to the second region R 2 , and then pass through the second region R 2  again to move toward the gas outlet  22 . Therefore, these solid substances are more likely to be discharged through the solid substance discharge port  23  in the course of passing through the second region R 2  again and moving toward the gas outlet  22 . Thus, in the separation device  1 , the separative performance of separating solid substances contained in a gas from the gas can be further improved. 
     As shown in  FIG.  2   , an outer cover  7  may be optionally attached to the separation device  1 . The outer cover  7  has a bottomed cylindrical shape. The outer cover  7  covers the casing  2  at the side of the bottom part  24 . Although not shown, the outer cover  7  has an opening, a cut-out, or the like for exposing the outlet tubular part  6 . The outer cover  7  prevents particles discharged through the solid substance discharge port  23  from scattering away from the separation device  1 . 
     As shown in  FIG.  5   , the separation system  10  includes the separation device  1  and the driving device  11  configured to rotationally drive the rotor  3  of the separation device  1 . The driving device  11  includes, for example, a motor configured to rotationally drive the rotor  3 . The driving device  11  may be configured such that a rotation shaft of the motor is directly or indirectly coupled to the rotor  3  or such that rotation of the rotation shaft of the motor is transmitted to the rotor  3  via a pulley and a rotary belt. The motor may be disposed inside the casing  2  or may be disposed outside the casing  2 . The rotational velocity of the rotor  3  rotationally driven by the driving device  11  is, for example, 1500 rpm to 3000 rpm. 
     The separation system  10  further includes the control device  12  configured to control the driving device  11 . The control device  12  includes a computer system. The computer system includes, as principal hardware components, a processor and memory. The processor executes a program stored in the memory of the computer system, thereby implementing functions as the control device  12 . The program may be stored in advance in the memory of the computer system. Alternatively, the program may also be downloaded over a telecommunications network or be distributed after having been recorded in some non-transitory storage medium such as a memory card, an optical disc, or a hard disk drive, any of which is readable for the computer system. The processor of the computer system includes one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). As used herein, the “integrated circuit” such as an IC or an LSI is called by a different name depending on the degree of integration thereof. Examples of the integrated circuits include a system LSI, a very large-scale integrated circuit (VLSI), and an ultra large-scale integrated circuit (ULSI). Optionally, a field-programmable gate array (FPGA) to be programmed after an LSI has been fabricated or a reconfigurable logic device allowing the connections or circuit sections inside of an LSI to be reconfigured may also be adopted as the processor. The plurality of electronic circuits may be collected on one chip or may be distributed on a plurality of chips. The plurality of chips may be collected in one device or may be distributed in a plurality of devices. As mentioned herein, the computer system includes a microcontroller including one or more processors and one or more memory elements. Thus, the microcontroller is also composed of one or more electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit. 
     (3) Operation of Separation Device and Separation System 
     In the separation device  1  according to the embodiment, the rotation direction A 1  (see  FIGS.  3  and  4   ) of the rotor  3  is, for example, a clockwise direction when the rotor  3  is viewed from the bottom part  24  in the axial direction D 1  of the casing  2 . The separation system  10  rotationally drives the rotor  3  by the driving device  11 . 
     In the separation device  1 , rotation of the rotor  3  provided with the blades  4  enables force to be applied to air flowing in the inside space (flow path) of the casing  2  in a rotation direction around the rotation central axis  30 . In the separation device  1 , the rotation of the rotor  3  rotates the plurality of blades  4  together with the rotor  3 , which results in that the velocity vector of the air flowing through the inside space of the casing  2  has a velocity component in a direction parallel to the rotation central axis  30  and a velocity component in the rotation direction around the rotation central axis  30 . In sum, in the separation device  1 , rotation of the rotor  3  and each blade  4  generates a swirling airflow in the casing  2 . The swirling airflow is a three-dimensional helically rotating airflow. 
     In the separation device  1 , solid substances contained in the air flowing in the casing  2  receive centrifugal force in a direction toward the inner peripheral surface  26  of the casing  2  from the rotation central axis  30  of the rotor  3  while the air helically rotates in the inside space of the casing  2 . The solid substances receiving the centrifugal force move toward the inner peripheral surface  26  of the casing  2  and helically rotate along the inner peripheral surface  26  in the vicinity of the inner peripheral surface  26  of the casing  2 . Then, in the separation device  1 , some of the solid substances in the air are discharged through the solid substance discharge port  23  in the course of passing through the inside space of the casing  2 . The centrifugal force that acts on the solid substances is proportional to the mass of the solid substances. Thus, the solid substances having a relatively large mass are likely to reach the vicinity of the inner peripheral surface  26  of the casing  2  earlier than the solid substances having a relatively small mass. 
     In the separation device  1 , the swirling airflow (swirling flow) is generated in the inside space of the casing  2 , and therefore, some of the solid substances (e.g., dust) in the air flowing in the casing  2  through the gas inlet  21  of the casing  2  are discharged through the solid substance discharge port  23 , and air (purified air) from which the solid substances have been separated (removed) flows out through the gas outlet  22  of the casing  2 . 
     The separation device  1  has the space  25  in the casing  2 . Therefore, for example, even when an eddy flow is generated in a gap between two blades  4  adjacent to each other in the rotation direction A 1  of the rotor  3  between the outer peripheral surface  37  of the rotor  3  and the inner peripheral surface  26  of the casing  2 , the eddy flow is readily rectified into the helical airflow in the space  25  on the downstream side of each blade  4 . Particles having a large particle size tend to deviate from the airflow when receiving the centrifugal force, approach the inner peripheral surface  26  of the casing  2 , and are easily discharged through the solid substance discharge port  23 . In contrast, particles having a small particle size strongly tend to move with the airflow, but in the separation device  1 , the airflow is readily rectified into the helical airflow swirling along the inner peripheral surface of the casing  2  in the space  25  on the downstream side of each blade  4 , and thus, the particles having a small particle size are also easily discharged through the solid substance discharge port  23 . 
     Moreover, the separation device  1  includes the separating wall  5 , and thus, when solid substances passing through the second region R 2  and moving toward the gas outlet  22  reaches the bottom part  24 , passes through the first region R 1 , and then returns toward the gas inlet  21 , the separating wall  5  prevents the solid substances from moving to the second region R 2  in the course of their returning toward the gas inlet  21 . This reduces the possibility of solid substances (particles) staying in the vicinity of the gas outlet  22 . This can reduce the possibility that the solid substances are discharged through the gas outlet  22 , thereby improving the separative performance of separating solid substances contained in a gas from the gas. In addition, particles that have returned to the vicinity of the blade  4  while passing through the first region R 1  pass through the second region R 2  again and move toward the gas outlet  22 , and therefore, the particles are easily discharged through the solid substance discharge port  23  in the course of moving toward the gas outlet  22 . 
     For the separation device  1 , the inventors of the present invention simulated, by using software for particle trajectory analysis, the simulation results obtained by using the fluid analysis software. As a method of the particle trajectory analysis, a Discrete Phase Model (DPM) may be adopted. In  FIGS.  7  and  8   , examples of trajectories of particles in the casing  2  of the separation device  1  according to the embodiment are shown in thick lines.  FIG.  7    shows an example of the trajectory of a particle that passes through the second region R 2  in the space  25 , moves toward the gas outlet  22 , and is discharged through the solid substance discharge port  23  without reaching the bottom part  24 .  FIG.  8    shows an example of the trajectory of a particle that passes through the second region R 2  in the space  25 , moves toward the gas outlet  22 , reaches the bottom part  24 , passes through the first region R 1 , returns toward the gas inlet  21 , then passes through the second region R 2  again moves toward the gas outlet  22 , and is discharged through the solid substance discharge port  23  in the course of moving toward the gas outlet  22 . In particular, as shown in  FIG.  8   , in the separation device  1 , the solid substance passing through the second region R 2  in the space  25  and moving toward the gas outlet  22  reaches the bottom part  24 , passes through the first region R 1 , returns to the vicinity of the blade  4 , and then, in the course of passing through the second region R 2  again and moving toward the gas outlet  22 , the particle can be discharged through the solid substance discharge port  23 . 
     Regarding separation characteristics of the separation device  1 , the separation efficiency tends to increase as the rotational velocity of the rotor  3  increases. Moreover, regarding the separation characteristics of the separation device  1 , the separation efficiency tends to increase as the separation particle size increases. In the separation device  1 , for example, the rotational velocity of the rotor  3  is preferably set such that fine particles larger than or equal to a prescribed particle size are separated. The fine particles having the prescribed particle size are assumed to be, for example, particles having an aerodynamic diameter of 2 μm. The term “aerodynamic diameter” means the diameter of a particle which is in terms of aerodynamic behavior, equivalent to a spherical particle having a specific gravity of 1.0. The aerodynamic diameter is a particle size obtained from the sedimentation rate of a particle. Examples of the solid substances which are not separated by the separation device  1  and which remain in air include fine particles having a particle size smaller than the particle size of fine particles to be separated by the separation device  1  (in other words, fine particles having a mass smaller than the mass of the fine particles to be separated by the separation device  1 ). 
     (4) Advantages 
     The separation device  1  according to the embodiment includes the casing  2 , the rotor  3 , and the blades  4 . The casing  2  includes the gas inlet  21 , the gas outlet  22 , and the solid substance discharge port  23 . The rotor  3  is disposed inside the casing  2  and is rotatable around the rotation central axis  30  extending along the axial direction D 1  of the casing  2 . The blades  4  are disposed between the casing  2  and the rotor  3  and rotate together with the rotor  3 . Each blade  4  has the first end  41  adjacent to the gas inlet  21  and the second end  42  adjacent to the gas outlet  22 . The casing  2  has the space  25  extending to the solid substance discharge port  23  with respect to the second end  42  of each blade  4  in the axial direction D 1  of the casing  2 . The separation device  1  further includes the separating wall  5  which separates the space  25  into the first region R 1  on the inner side and the second region R 2  on the outer side when viewed in the axial direction D 1  of the casing  2 . 
     The configuration described above enables the separative performance of the separation device  1  according to the embodiment to be improved. 
     (5) Application Example of Separation Device 
     The separation device  1  is disposed on the upstream side of an air filter such as a high efficiency particulate air filter (HEPA filter) disposed on the upstream side of an air conditioning facility in an air purification system to be installed in, for example, a dwelling house. The “HEPA filter” is an air filter which has particle collection efficiency of higher than or equal to 99.97% of particles having a particle size of 0.3 μm at a rated flow rate and whose initial pressure loss is 245 Pa or less. For the air filter, a particle collection efficiency of 100% is not an essential condition. Providing the separation device  1  to the air purification system enables the air purification system to suppress the fine particles such as dust contained in air from reaching the air filter. Thus, the air purification system enables the life of, for example, an air filter provided on the downstream side of the separation device  1  to be prolonged. For example, the air purification system enables pressure loss to be suppressed from increasing due to an increase in gross mass of, for example, fine particles collected by the air filter. Thus, the air filter in the air purification system may be replaced with a reduced frequency. The configuration of the air purification system is not limited to a configuration in which the air filter and the air conditioning facility are housed in different housings, but the air filter may be provided in the housing of the air conditioning facility. In other words, the air conditioning facility may include an air filter in addition to the air blowing device. 
     (6) Variation of Embodiment 
     The embodiment is a mere example of various embodiments of the present disclosure. Various modifications may be made to the embodiment depending on design and the like as long as the object of the present disclosure is achieved. 
     For example, in a first variation of the embodiment, the separation device  1  does not have to include the structure  9  as shown in  FIG.  9   . In this case, the separating wall  5  may be at a position where the separating wall  5  overlaps the rotor  3  in the axial direction D 1  of the casing  2 . Of course, even when the separation device  1  is not provided with the structure  9 , the separating wall  5  may be at a position where the separating wall  5  overlaps the blades  4  in the axial direction D 1  of the casing  2  (see  FIG.  2   ). 
     In a variation, the shape of the separating wall  5  is not limited to a cylindrical shape but may be a tapered cylindrical shape with the diameter at the side of the first end  51  being smaller than the diameter at the side of the second end  52 , or the diameter at the side of the second end  52  being smaller than the diameter at the side of the first end  51 . 
     In a variation, the separation device  1  may include a plurality of separating walls  5 . The plurality of separating walls  5  may include two separating walls  5  having the same diameter and coaxially arranged so as not to overlap each other in the axial direction D 1 , or may include two separating walls  5  having different diameters and coaxially arranged so as to overlap or not to overlap each other in the axial direction D 1 . 
     In a variation, the length of the solid substance discharge port  23  (the dimension of the casing  2  along the axial direction D 1 ) may be appropriately adjusted according to the separative performance required for the separation device  1 . 
     In a variation, the solid substance discharge port  23  is not limited to being at a location where the solid substance discharge port  23  does not overlap the blades  4  in the direction orthogonal to the rotation central axis  30  but may be at a location where the solid substance discharge port  23  at least partially overlaps the blades  4  in the direction orthogonal to the rotation central axis  30 . In this case, as viewed in the axial direction D 1  of the casing  2  (i.e., as viewed in the direction along the rotation central axis  30 ), the solid substance discharge port  23  does not overlap with any of the plurality of blades  4 . In this case, for example, the protruding length of the plurality of blades  4  from the outer peripheral surface  37  of the rotor  3  is determined such that each blade  4  does not collides with the solid substance discharge port  23 . 
     In a variation, the number of the solid substance discharge ports  23  formed in the casings  2  is not limited to two, but the casings  2  may have one solid substance discharge port  23  or may have three or more solid substance discharge ports  23 . 
     In a variation, the plurality of solid substance discharge ports  23  are not limited to having the same shape but may have different shapes. 
     In a variation, a discharge tubular part extending in a direction in which the solid substance discharge port  23  is open may be formed at the peripheral edge of the solid substance discharge port  23  in the outer peripheral surface  27  of the casing  2 . 
     In a variation, each of the plurality of blades  4  has a tip end adjacent to the casing  2  and a base end adjoining the rotor  3 , and the tip end is located frontward of the base end in the rotation direction A 1  of the rotor  3  in the protrusion direction from the rotor  3 . 
     In a variation, each of the plurality of blades  4  may have a shape having one or more curved portions in the shape of, for example, an arc. 
     In a variation, each of the plurality of blades  4  may have a helical shape around the rotation central axis  30  of the rotor  3 . Here, “helical” is not limited to a helical shape with one or more turns but includes a shape corresponding to part of the helical shape with one turn. 
     In a variation, the rotor  3  may have a columnar shape. 
     In a variation, the rotor  3  may have a bottomed tubular shape having a bottom wall adjacent to the gas inlet  21 . When the rotor  3  has the bottomed tubular shape, the rotor  3  preferably includes a reinforcing wall on its inside. 
     In a variation, the rotor  3  may include a plurality of rotary members. For example, the structure  9  may constitute a part of the rotor  3 . In this case, in the rotor  3 , for example, the rotary members aligned in a direction along the central axis  29  of the casing  2  are coupled to each other. 
     In a variation, the structure  9  may have a columnar shape or any other shape such as a truncated cone shape. 
     In a variation, the structure  9  may be provided with a reinforcing wall therein. 
     In a variation, the casing  2  may have a plurality of gas outlets  22 . In this case, the casing  2  may have a plurality of outlet tubular parts  6 . The plurality of outlet tubular parts  6  may be aligned in the outer circumferential direction of the casing  2  or may be located at different locations in the axial direction D 1  of the casing  2 . Further, as long as the separation device  1  has the gas outlet  22 , the separation device  1  does not have to have the outlet tubular part  6 . 
     In a variation, the gas flowing through the gas inlet  21  of the casing  2  into the casing  2  is not limited to air but may be, for example, exhaust gas. 
     (7) Aspects 
     Based on the embodiment, the variations, and the like described above, the following aspects are disclosed. 
     A separation device ( 1 ) of a first aspect includes a casing ( 2 ), a rotor ( 3 ), and a blade ( 4 ). The casing ( 2 ) includes a gas inlet ( 21 ), a gas outlet ( 22 ), and a solid substance discharge port ( 23 ). The rotor ( 3 ) is disposed inside the casing ( 2 ). The rotor ( 3 ) is rotatable around a rotation central axis ( 30 ) extending along an axial direction (D 1 ) of the casing ( 2 ). The blade ( 4 ) is disposed between the casing ( 2 ) and the rotor ( 3 ). The blade ( 4 ) is configured to rotate together with the rotor ( 3 ). The blade ( 4 ) has a first end ( 41 ) adjacent to the gas inlet ( 21 ) and a second end ( 42 ) adjacent to the gas outlet ( 22 ). The casing ( 2 ) has a space ( 25 ) extending to the solid substance discharge port ( 23 ) with respect to the second end ( 42 ) of the blade ( 4 ) in the axial direction (D 1 ). The separation device ( 1 ) further includes a separating wall ( 5 ). The separating wall ( 5 ) separates the space ( 25 ) into a first region (R 1 ) on an inner side and a second region (R 2 ) on an outer side when viewed in the axial direction (D 1 ) of the casing ( 2 ). 
     With this aspect, when solid substances (particles) passing through the second region (R 2 ) and moving toward the gas outlet ( 22 ) reach the gas outlet ( 22 ), pass through the first region (R 1 ), and then return toward the gas inlet ( 21 ), the solid substances are prevented from moving to the second region (R 2 ) in the course of returning toward the gas inlet ( 21 ). This reduces the possibility of the solid substances staying in the vicinity of the gas outlet ( 22 ). This reduces the possibility that the solid substances are discharged through the gas outlet ( 22 ), thereby improving the separative performance of separating solid substances contained in a gas from the gas. 
     In a separation device ( 1 ) of a second aspect referring to the first aspect, the separating wall ( 5 ) has a tubular shape having an axis along the axial direction (D 1 ) of the casing ( 2 ) and having openings on both sides in the axial direction. 
     This aspect improves the reliability of separation of the first region (R 1 ) and the second region (R 2 ) in the space ( 25 ) and improves the separative performance of separating solid substances contained in a gas from the gas. 
     In a separation device ( 1 ) of a third aspect referring to the second aspect, the separating wall ( 5 ) has a round tubular shape. 
     This aspect further improves the reliability of separation of the first region (R 1 ) and the second region (R 2 ) in the space ( 25 ) and improves the separative performance of separating solid substances contained in a gas from the gas. 
     In a separation device ( 1 ) of a fourth aspect referring to any one of the first to third aspects, for a velocity vector of a flow velocity of the gas in the space ( 25 ), a vector obtained by subtracting a velocity vector of a flow velocity in the first region (R 1 ) from a velocity vector of a flow velocity in the second region (R 2 ) is positive, where a direction from the gas inlet ( 21 ) toward the gas outlet ( 22 ) along the axial direction (D 1 ) of the casing ( 2 ) is defined as a positive direction. 
     This aspect improves the separative performance of separating solid substances contained in a gas from the gas. 
     In a separation device ( 1 ) of a fifth aspect referring to any one of the first to fourth aspects, the separating wall ( 5 ) is disposed at a position where the separating wall ( 5 ) overlaps the blade ( 4 ) in the axial direction (D 1 ) of the casing ( 2 ). 
     With this aspect, a region in the space ( 25 ) which overlaps the blade ( 4 ) in the axial direction of the casing ( 2 ) is separated into the first region (R 1 ) and the second region (R 2 ). 
     In a separation device ( 1 ) of a sixth aspect referring to any one of the first to fifth aspects, the solid substance discharge port ( 23 ) is formed as a slit in an outer peripheral surface of the casing ( 2 ), the slit extending along the axial direction (D 1 ). 
     With this aspect, the solid substances (particles) passing through the second region (R 2 ) and moving toward the gas outlet ( 22 ) are easily discharged through the solid substance discharge port ( 23 ) in the course of moving toward the gas outlet ( 22 ), thereby improving the separative performance of separating solid substances contained in a gas from the gas. 
     In a separation device ( 1 ) of a seventh aspect referring to the sixth aspect, the solid substance discharge port ( 23 ) has a part overlapping the gas outlet ( 22 ) on one plane orthogonal to the axial direction of the casing ( 2 ). The part of the solid substance discharge port ( 23 ) is disposed rearward of the gas outlet ( 22 ) in a rotation direction (A 1 ) of the rotor ( 3 ). 
     With this aspect, the solid substances (particles) are easily discharged through the solid substance discharge port ( 23 ), thereby improving the separative performance of separating solid substances contained in a gas from the gas. 
     A separation device ( 1 ) of an eighth aspect referring to any one of the first to seventh aspects further includes a structure ( 9 ) disposed along the rotation central axis ( 30 ) of the rotor ( 3 ). The structure ( 9 ) is at least partially in the space ( 25 ). 
     With this aspect, the space ( 25 ) between the structure ( 9 ) and the casing ( 2 ) is separated into the first region (R 1 ) and the second region (R 2 ). 
     A separation system ( 10 ) of a ninth aspect includes the separation device ( 1 ) of any one of the first to eighth aspects, and a driving device ( 11 ) configured to rotationally drive the rotor ( 3 ). 
     This aspect improves the separative performance of separating solid substances contained in a gas from the gas. 
     Note that constituent elements according to the second to eighth aspects are not essential constituent elements for the separation device ( 1 ) but may be omitted as appropriate. 
     REFERENCE SIGNS LIST 
     
         
           1  Separation Device 
           2  Casing 
           21  Gas Inlet 
           22  Gas Outlet 
           23  Solid Substance Discharge Port 
           25  Space 
           3  Rotor 
           30  Rotation Central Axis 
           4  Blade 
           41  First End 
           42  Second End 
           5  Separating Wall 
           9  Structure 
           10  Separation System 
           11  Driving Device 
         D 1  Axial Direction 
         R 1  First Region 
         R 2  Second Region