Patent Publication Number: US-2019176106-A1

Title: Device for treating material, comprising a container

Description:
The invention relates to a device for treating material with a container, in which is arranged a stirrer that can be rotated around a central axis, and with a first deflecting device, which is arranged in the container above the stirrer, so as to deflect a material flow conveyed by the stirrer to the middle of the container. 
     Different kinds of stirrers are known, which as a rule are open toward the top. Therefore, the material flow is stirred in the stirrer container, and material that is upwardly stirred in the process makes its way toward the top until gravity pulls it back down again. 
     Publications WO 2011/144196, WO 2012/041269 and WO 2013/135224 show material handling devices with containers, which are shaped in such a way that the material flow conveyed by the stirrer through the inner container wall is deflected toward the center of the container above the stirrer. A central screw guides the material out of an upper area of the container to the stirrer, and from there the material flow wanders radially outward, upward and, guided by the deflecting device, toward the middle of the container. 
     It was found that, in particular when treating coarse materials, clumps arise that are poorly dissolved in the stirrer, if at all. 
     Therefore, the object of the invention is to further develop such devices in such a way as to avoid clump formations. 
     This object is achieved with a generic device, in which the stirrer has a coaxial axle body, the diameter of which in the area of the stirrer measures at least one fourth the diameter of the stirrer. 
     In order to use the stirrer in the radially outer and also in its radially inner area, it has previously been proposed that that the functional areas of the stirrer be arranged on an axle with a small diameter. The material here gets into the middle of the stirrer, and then from the radially inner areas to the radially outer areas of the stirrer. 
     The circumferential speed is relatively low in the radially inner areas of the stirrer, so that undesired clumps are most likely to form there. Clump formation can hardly be avoided even by using spiral feeders and specially shaped stirrer arms. 
     Therefore, the invention is based on the knowledge that the central area of the stirrer in which the axle lies is of secondary importance for stirrer function given the low acceleration present there, and thus should be configured as a coaxial axle body with an enlarged diameter. The coaxial axle body denotes a body formed by the axle itself, a cylinder arranged around the central axle or another body configured so as to keep this middle area free of material. As a result, the material is only treated by the stirrer in an area spaced apart from the middle of the stirrer, and the central area is not accessible for the material, so that no clumps can form there either. However, the circumferential speed is so high in the radially outer area that a good circulation is achieved there, eliminating any concern over clumping. 
     In order to achieve an especially good circulation at a low energy outlay, it is proposed that the container underneath the stirrer have a base, and that a distance between the base and deflecting device measure at most half the maximum diameter of the container between the base and deflecting device. 
     It is advantageous that the distance between the central axle and radially outer container inner wall in the area of the stirrer correspond to about the distance between the base and deflecting device. “About” here means a deviation of at most 30%, and preferably of at most 20%, from the larger distance. 
     The base can here be designed as a continuous floor surface, as in a kneader, or as a perforated sheet, as in a conditioner. 
     The stirrer or arms of the stirrer should reach as far as possible into the radially outer areas of the container, so that no dead zones come about. Therefore, it is proposed that the diameter of the stirrer measure at least 70%, preferably at least 80%, of the maximum diameter of the container in the area of the stirrer. 
     An advantageous embodiment provides that the stirrer have one or several arms, which extend radially outward from the central axle body. 
     An especially simple embodiment provides that the first deflecting device have a circular blank with a central, free passage that is arranged in the container. In a simple embodiment, this is a horizontal sheet with a centrally free passage, which makes it possible to load the container with material. 
     The container can also be shaped in such a way that the first deflecting device consists of a constriction on the container. As a consequence, the container has a smaller diameter in the area of the deflecting device than below the constriction, and preferably also a smaller diameter than above the constriction. This makes it possible to use the area above the constriction as a feed and buffer area, while the reaction area with the stirrer lies below the constriction. 
     In order to induce a sufficient inward deflection of the material by means of the first deflecting device on the one hand, and be able to easily supply additional material in a central manner on the other, it is proposed that the first deflecting device have a central, free passage with a diameter of at least 0.8 m. For example, the free passage can have a diameter of less than 80% or even less than 60% of the maximum container diameter. 
     When using the kneader, the water level should lie in or above the constricted diameter. For example, if the constricted diameter is formed by a plate, the water surface lies in the plane of the plate or somewhat above it. This calms the water surface, and less energy is lost as the result of wave formation. 
     The free diameter is intended to make it possible to supply the solid to the lower area. This solid should automatically fall into the lower area, thereby eliminating the need for a feed screw. 
     In a device with two stirrers arranged one over the other, the deflecting device need not be made out of a solid material, since one material flow can serve as a respective deflecting device for the other material flow. For this reason, it is proposed that the first deflecting device be comprised of a material flow conveyed downwardly toward the middle of the container by an additional stirrer arranged above the first stirrer. 
     It was found that a conveyor arranged above the stirrer that conveys material to the stirrer is not necessary, and can even be harmful. For this reason, it is proposed that the container on the central axle have no conveyor that conveys to the stirrer, at least above the deflecting device. 
     Suitable as a buffer and for increasing the pressure in the stirrer area is a feed chamber, which is formed above the deflecting device as part of the container. This feed chamber can also be an additional container part, a collar or a cylindrical container part. 
     In particular when using the device as a kneader, it is advantageous that it have a tangential supply line to the container. As a rule, the feeder already provides the supplied material with a velocity component that can be used for relieving the stirrer given a tangential supply in the container. 
     Advantageous embodiment variants provide that a second concentric deflecting device be arranged above the stirrer. 
     This second deflecting device can have a tapered section, which is concentrically arranged above the stirrer. This tapered section is shaped like a cone or truncated cone, and makes it easier to direct the material in the device. 
     In particular for using the device as a kneader with a tangential inflow, it is proposed that the second deflecting device have a truncated cone that tapers toward the stirrer, so as to divert the material flow deflected radially inwardly to the central axle toward the stirrer. Given two stirrers located one over the other, two truncated cones are used in a corresponding embodiment, whose radially larger circular areas abut against each other. 
     By contrast, when a central inflow to the device is provided, it is advantageous for the second deflecting device to have a truncated cone that expands toward the stirrer, so as to divert the material flow to the outside. 
     Especially good mixing results are achieved with devices that have baffle plates on the radially outer container inner wall. For example, this is achieved with a container that has a circumferential wall, whose radially outermost area has at least one continuous kink with an obtuse angle open toward the container inner side. Two kinks are preferably provided, which also make it possible to provide an area of a perpendicular container wall between these kinks. 
     In a method for operating this device, a fill level above the first deflecting device is preferably set in the container. This provides a material buffer, and the material itself acts to exert pressure on the area in which the stirrer is located. For example, when inserting a plate, it should lie at the liquid level or only slightly thereunder. The liquid above the liquid level technologically only yields an elevated water pressure. The area above the constriction should therefore be only slightly flooded, or not at all. 
     In an advantageous procedure, the speed of the stirrer is lowered while filling as the load rises. 
     An average speed should lie at 3 to 10 m/s at the radially outermost stirrer end, with roughly 5 m/s being a good value in practice for combining good mixing with efficient energy input. 
     The speed of the stirrer can also be set so as to force the material into the radially outer areas of the container in such a way that all material is driven to the outside by the centrifugal force in the middle of the container, preferably in the area of at least 50% of the axis. 
    
    
     
       Advantageous embodiment variants of devices according to the invention are shown in the drawing, and will be explained in more detail below. 
       Shown on: 
         FIG. 1  is a simple embodiment of a device according to the invention with circular blank, 
         FIG. 2  is an embodiment of the device according to the invention with a truncated cone that expands toward the stirrer, 
         FIG. 3  is a device with a feed chamber, 
         FIG. 4  is a device with a tangential inflow and a truncated cone that tapers toward the stirrer, and 
         FIG. 5  is a device with two stirrers located one over the other. 
     
    
    
     The device  1  shown on  FIG. 1  has a container  2 , in which a screen plate  4  is arranged as the base  3 . A stirrer is provided concentrically to the cylindrical container  2  on a central axle  5  directly above the base  3 . Provided above the stirrer  6  as a first deflecting device  7  is a horizontally arranged circular blank  8  with a circular, central free passage  9 . 
     The stirrer  6  has a coaxial axle body  10 , from which six bent arms  11  radially extend. 
     The axle body  10  has a diameter  12  in the area of the stirrer  6  whose length measures at least one fourth of the diameter  13  of the stirrer  6 . 
     The stirrer  6  is driven by a gearbox  14  and a motor  5 . As a consequence, the arms  11  turn around the central axle  5 , so as to circulate material (not shown) between the circular blank  8  and base  3 . 
     To ensure that the material strikes the lower side of the circular blank  8  and is there diverted, the distance  16  between the base  3  and deflecting device  7  measures at most half the diameter  17 . The diameter  17  is the maximum diameter of the container  2  between the base  3  and deflecting device  7 . 
     When using the device, material with water above the circular blank  8  is put into container  2 . The material falls through the free passage  9  in the area below the circular blank  8  and onto the stirrer  6 . This stirrer  6  turns the material in the container  2  between the base  3  and deflecting device  7 , wherein the material is upwardly driven by the shape of the container  2  and stirrer  6  in the radially outer area, and flows toward the top until it strikes the lower side of the circular plank  8  and gets to the middle  18  of the container. The material there falls downwardly to the stirrer  6 , and is conveyed radially outwardly again by the stirrer  6 . 
     In particular given coarse or pasty material, this gives rise to high shearing forces between the material particles and a thorough mixing of the material. 
     The material has the lowest circumferential speed in the center of the stirrer  6 , which encourages the formation of clumps here. For this reason, the stirrer has the axial axle body  10 , which here prevents material from accumulating, and deflects the material radially outward And toward the stirrer arms  11 . 
       FIG. 1  shows an especially small stirrer. A stirrer is advantageously of the kind depicted in device  20 . The stirrer  21  here has a diameter  22  almost as large as the maximum diameter  23  of the container  24  between the deflecting device  25  and the base  26  of the container  24 . 
     In this exemplary embodiment, the deflecting device  25  is a container wall that faces radially inward from the maximum container diameter  21 , and forms a constriction  27  on the container. 
     Above the coaxial axle body  28 , this container has a tapered section  30  as a second deflecting device  29 , which is arranged concentrically above the stirrer  21 . This tapered section  30  is shaped like a cone or truncated cone, whose shell surface expands toward the stirrer. 
     A screen plate  31  is located below the stirrer  21 , and under that is the motor  32  as the drive for the stirrer  21 . 
     Material that gets tangentially (not shown) or from above into the container  24  is thus deflected radially outward to the stirrer  21  by the conical jacket surface of the tapered section  30 , and wanders upwardly along the inner wall of the container  24  in the radially outward area, so as to be deflected radially inwardly again by the deflecting device  25 . 
     The device  40  shown on  FIG. 3  has a funnel  41 , which transitions into a cylindrical collar area  42  and then into a feed chamber  44  bordered by a circular blank  43 . The container  45  expands below the circular blank  43 . The circumferential wall there has a first continuous kink  46  in the radially outermost area of the container  45 , which transitions into a short cylindrical jacket area  47 , and in so doing forms an obtuse angle  48  open toward the interior side of the container. This is followed toward the bottom by another kink  49 , which once again has an obtuse angle  50  open toward the container interior side  51 . 
     As a consequence, the material gets into the feed chamber  44  either via the funnel  41  or via a tangential supply line  52 , and from there to the tapered section  54  through the free passage  53 . In the exemplary embodiment, the free passage has a diameter  55  of about one meter. 
     The container  45  has no conveyor that leads to the stirrer  57  both on the central axle  56  and above and below the deflecting device  43 . 
       FIG. 4  also shows a device  60  with a second concentric deflecting device  61  above the stirrer  62 . By contrast, this second deflecting device  61  has a truncated cone  63  that tapers toward the stirrer  62 . This truncated cone  63  takes the material conveyed through the tangential inflow  64  into the container  65 , which is stirred by the stirrer  62  and flows upwardly in radially outer areas of the container  65 , and guides it back down to the stirrer  62 . This is accomplished by means of a conical circumferential surface  67  that is concentric to the central axle of the container  65 . 
     The gearbox  69  of the motor  68  drives the stirrer  62 , which stirs the material in the container  65 , during which the material is first made to flow upwardly by the stirrer shape, centrifugal forces and shape of the inner wall  70  of the container  65 . The material then gets to an inner container wall  71  above the stirrer  62 , which as the first deflecting device deflects the material toward the central axle  66 . The material is then deflected back down to the stirrer  62  via the conical jacket surface  67  of the truncated cone  63 . The material thus circles around a central annular axis of a torus and stirrer and container shape, and the deflecting devices are designed so as to, if at all possible, produce no areas with an especially low speed. This leads to an intensive mixing, and prevents clump formation. 
     In the device  80  shown on  FIG. 5 , the first deflecting device need not necessarily be a container wall or container insert, but rather can also be provided by a second material flow. This device  80  has a container  81 , in which a first motor  82  and a first gearbox  83  drive a first stirrer  84  in the container  81 . Located above that is the second motor  85 , which drives a stirrer  87  in the container  81  via a second gearbox  86 . The stirrer  87  thus produces a downward material flow, while the stirrer  84  produces an upward material flow. At the location where these material flows meet, the lower material flow forms a deflecting device for the upper material flow, and the upper material flow forms a deflecting device for the lower material flow. The material flow  88  generated by the second stirrer  87  thus forms the first deflecting device for the material flow  89  produced by the stirrer  84  toward the container middle  90 . 
     Arranged in the middle of the container as a coaxial axle body is a double tapered section  91 , which has a lower conical jacket surface  92  that tapers toward the stirrer, so as to deflect the material flow  89  toward the stirrer  84 . 
     The upper side of the double tapered section  91  has a conical jacket surface  93  that tapers toward the stirrer  87 , which deflects the material flow  88  toward the stirrer  87 . 
     As evident from the device shown on  FIG. 3 , it is advantageous that the fill level (not depicted) in the container be set above the first deflecting device  43 . As a result, the feed chamber  44  along with the chamber above that up to the funnel  41  can be used as a storage space for material, and a liquid material or a filling with liquid or water produces a hydrostatic pressure that acts on the material in the area of the stirrer  57 . 
     In order to achieve the desired material flow in the container  45 , it is proposed that the speed of the stirrer be lowered while filling the container  45  with material as the load increases. This makes it possible to achieve an especially intensive circulation of the material at a low power consumption.