Patent Publication Number: US-11642700-B2

Title: Screen apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/EP2018/080436 filed Nov. 7, 2018, and claims priority to German Patent Application No. 10 2017 221 731.6 filed Dec. 1, 2017, the disclosures of which are hereby incorporated by reference in their entirety. 
     BACKGROUND 
     Field of the Invention 
     The invention relates to a screen apparatus for screening granulate, in particular moist and/or dry granulate, comprising a screen housing having a base, a cover and a side wall, an inlet for the granulate arranged on the screen housing, an outlet for the sieved granulate arranged on the screen housing, a screen arranged in the screen housing and an inlet for transfer air. 
     Related Art 
     Screen apparatuses for granulates, in particular for a wet granulation process or a drying process in a screening process downstream of a fluidisation apparatus have long been the state of the art. The known screen apparatuses are filled via an inlet for the granulate arranged on the cover of the screen apparatus and emptied following the screening process via an outlet arranged after a suction shoe in the base of the screen apparatus. Here, transport of the granulate from the inlet to the outlet takes place, by way of example, via a gravity feed or pneumatic delivery. 
     The disadvantage of such screen apparatuses for granulates known from the state of the art, in which the, for example, moist granulate has to be transferred to a dryer is that these screen apparatuses have or require a large construction height and thus the space must also be available to create a process engineering system equipped with a known screen apparatus. Furthermore, the known screen apparatuses have the disadvantage that due to the at least to some extent conical form of the suction shoe of the screen housing of the known screen apparatus, as a result of buildup and adhesions of granulate in the conically shaped region (suction shoe) of the screen housing the product transfer of screened granulate is significantly restricted. 
     SUMMARY  
     The object of the invention is to provide a screen apparatus which minimises buildup or adhesions of granulate and at the same time requires a lower construction height of the screen housing and therefore eliminates the disadvantages from the state of the art. 
     This object is achieved with a screen apparatus of the abovementioned type, in that the outlet for the screened granulate (product) arranged on the screen housing is arranged in the side wall of the screen housing. In this way the required construction height of the screen apparatus is advantageously reduced, whereby installation in existing, for example process engineering, systems is simplified. The construction height is, by way of example, considerably reduced through the elimination of the conical region, also known as a suction shoe, below the screen, that is necessary according to the state of the art. In this way, buildup or adhesion of granulate in the screen housing, but in particular in the region of the screened granulate outlet, is prevented whereby throughout the operation a sufficiently fast and sufficiently good product transfer of the screened granulate is ensured. Through the compact design according to the invention, firstly there is a saving on the necessary construction height of the screen apparatus due to the elimination of the suction shoe and at the same time the inner surface of the screen housing in contact with the product is also reduced. 
     Particularly preferably, the screen apparatus according to the invention is used for screening moist and/or dry granulate, particularly preferably for a wet granulation process or a drying process in a fluidisation apparatus, by way of example a screening process downstream of a fluidised bed or similar. 
     In an advantageous configuration the screen housing has a cylindrical design, wherein the side wall of the screen housing has an at least partially conical form. As a result of such a geometrical configuration of the screen apparatus further space, including installation space, is saved whereby integration of the screen apparatus according to the invention into existing systems can be further improved. 
     In particular, it has been shown that particularly preferably the outlet for the screened granulate (product) arranged on the screen housing is arranged tangentially to the side wall of the screen housing. Through the arrangement of the outlet for the granulate tangentially to the side wall of the screen housing an optimised discharge of the screened granulate is achieved. In addition, through the tangential arrangement buildup or adhesions in the region of the outlet are minimised and a faster and trouble-free transport of the screened granulate is ensured. 
     In a preferred embodiment, the outlet for the screened granulate is arranged above the inlet for transfer air. Through the tangential flow/movement of the transfer air in the screen housing the centrifugal forces act on the granulate and drive or carry it upwards. Thus, it is advantageous to arrange the outlet for the screened granulate (product) above the inlet for the transfer air. 
     In addition, the screen apparatus is preferably designed so that the configuration of the screen arranged in the screen housing corresponds to the design of the screen housing. Thus, the inner surface in contact with the product is reduced, i.e. the available areas for buildup or adhesions in the screen housing are minimised, so that a faster and trouble-free transport of the screened granulate is ensured. 
     In a preferred configuration of the screen apparatus according to the invention, the screen apparatus has a grinding body arranged in particular in the screen housing. The advantage of a grinding body arranged in the screen housing is that in this way pressing of the granulate through the screen can be improved. By means of the grinding body the screening process is therefore optimised. 
     In an embodiment of the screen apparatus preferred in this regard, the grinding body arranged in the screen housing is arranged above the screen. The grinding body arranged in the screen housing is rotatably arranged; particularly preferably the grinding body can be driven by a motor, in particular an electric motor. Thus, the screening process is further optimised. 
     The configuration of the grinding body arranged in the screen housing is particularly preferably corresponds to the design of the screen. This matching of the grinding body to the shape of the screen considerably improves the performance of the screening process, since the granulate to be screened is pushed by means of the grinding body matched to the shape of the screen through the screen under a continuous and even pressure. 
     In a further preferred embodiment of the screen apparatus according to the invention, the screen apparatus has an inlet for transfer air, wherein the inlet for transfer air is preferably arranged on the side wall of the screen housing, particularly preferably tangentially to the side wall of the screen housing. Transfer air denotes gaseous media, preferably air, but also inert gases. Through the supply of transfer air, product transport is improved. In addition, in the screen housing of the screen apparatus an air flow is created, which minimises or totally prevents buildup or adhesions of granulate on the inner surface of the screen housing. In particular, the preferably lateral, but particularly preferable tangential, arrangement of the inlet for transfer air creates very good flow conditions for the transfer air in the screen housing for preventing buildup or adhesions of granulate and in connection with the granulate transport through the outlet. 
     According to a further preferred embodiment of the screen apparatus according to the invention, the screen apparatus has a rotor disc, which is in particular arranged between the screen arranged in the screen housing and the base of the screen housing and particularly preferably has at least a partially conical configuration. The advantage of a roto disc arranged between screen and base in the screen housing is that this serves to protect the seal below the screen and to prevent the product remaining on the base, i.e. on the lower horizontal level of the screen housing. 
     Particularly preferably, the rotor disc is arranged on a shaft driven by a motor, whereby an improved transfer of the screened granulate is ensured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention is explained in more detail below with reference to the attached drawing. Which shows as follows: 
       DETAILED DESCRIPTION 
         FIG.  1    a simple schematic representation of a basic design of a granulation line from the state of the art with a screen apparatus on the outlet of a high-shear granulator; 
         FIG.  2    a cross section of a detailed view of a screen apparatus from the state of the art according to detail A of  FIG.  1   ; 
         FIG.  3    a cross section of a first exemplary embodiment of a screen apparatus according to the invention with an outlet for the granulate arranged laterally on the screen housing and an inlet for the transfer air arranged laterally on the screen housing; 
         FIG.  4    a cross section of a second exemplary embodiment of a screen apparatus according to the invention with a rotor disc arranged in the screen housing and an outlet for the granulate arranged laterally on the screen housing according to sectional plane X-X in  FIG.  5   ; 
         FIG.  5    a top view of the second exemplary embodiment of the screen apparatus according to the invention with an outlet for the granulate arranged laterally on the screen housing and an inlet for the transfer air arranged laterally on the screen housing; 
         FIG.  6    a cross section of a schematic representation of a high-shear granulator with screen apparatus according to the invention arranged thereon; and 
         FIG.  7    a top view of the schematic representation shown in  FIG.  5    of a screen apparatus according to the invention arranged on a high-shear granulator. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a simple schematic representation of a basic design of a granulation line  1  known from the state of the art. In order, by way of example, to pass the moist granulate from a high-shear granulator  2  to a dryer  3  a transfer of the granulate is required. This transfer is carried out either by gravity feed of the dryer  3  or by pneumatic delivery. In the case of gravity feed, the granulate drops, propelled by its own weight, into the dryer  3 . However, this type of feeding requires a large installation height and the available space to create the granulation line  1 . In the granulation line  1  shown in  FIG.  1   , between the high-shear granulator  2  and the dryer  3  a screen apparatus  4  is shown on the outlet of the high-shear granulator  2 . The outlet of the screen apparatus  4  is connected to the dryer  3  by a flexible hose line  5 . 
       FIG.  2    shows a cross section of a detailed view of a screen apparatus  4  known from the state of the art according to detail A from  FIG.  1    for performing the granulate screening process, in particular for a screening process downstream of a wet granulation process or a drying process in a fluidised bed. 
     The screen apparatus  4  comprises a cover  6  and a screen housing  8  having a side wall  7 . Furthermore, the screen housing  8  also has an inlet  9  for the granulate arranged in the cover  6  of the screen housing  8  and an outlet  10  arranged on the screen housing  8 . In the screen housing  8  a screen  11  for screening the granulate is arranged such that all granulate entering via the inlet  9  is captured by the screen  11 . In the screen housing  8  the screen  11  is also associated with a grinding body  14  rotatable on a shaft  12  driven by a motor M in the direction of arrow  13 . In order to ensure the transfer of the granulate, by way of example, into a dryer  3  following screening, above and below the screen  11  of the screen apparatus  4  transfer air is fed in via inlets. The feeding in of transfer air to the screen apparatus  4  is carried out above the screen  11  via a first inlet  15  arranged in the cover  6  and via a second inlet  16  arranged after the screen  11 . 
     The granulate, which is emptied via the inlet  9  arranged in the cover  6  into the screen apparatus  4 , is pressed by the rotating grinding body  14  through the mesh of the screen  11 . At the start of the emptying of the granulate of the, in the exemplary embodiment, upstream high-shear granulator  2 , most of the granulate is emptied in one action into the screen  11  of the screen apparatus  4 . Thus, before and after the screen  11  arranged in the screen housing  8  blocking of the inlet  9  and the outlet  10  of the screen apparatus  4  often occurs. Blocking occurs, by way of example, due to buildup or adhesions of granulate on the inner surface  17  of the screen housing  8  in contact with granulate, preferably in the conically shaped region  18  of the screen housing  8 , since the conically configured region  18  considerably reduces the passage area of the screen housing  8  available for the granulate towards the outlet  10  of the screen housing  8 . By way of example, in actual applications the diameter of the screen housing  4  of 400 mm is reduced to a diameter of the outlet  10  of 100 mm. Furthermore, in the configuration of the screen apparatus  4  known from the state of the art, rounded chunks of granulate, which cannot be transported through the screen  11  usually form and remain in the screen  11  as wastage. 
       FIG.  3    illustrates a cross section of a first exemplary embodiment of a screen apparatus  104  according to the invention with an outlet  110  for the granulate to be screened arranged laterally on the screen housing  108  and an inlet  116  for transfer air arranged laterally on the screen housing  108 . 
     The screen apparatus  104  according to the invention for performing the granulate screening process, in particular for a screening process downstream of a wet granulation process or a drying process in a fluidised bed, according to the first exemplary embodiment comprises a screen housing  108  with a base  119 , a cover  106  and a side wall  107 . In addition, the screen apparatus  104  has an inlet  109  arranged on the screen housing  108 , an outlet  110  arranged on the screen housing  108 , a screen  111  arranged in the screen housing  108  and a grinding body  114  arranged in the screen housing  108 , wherein the outlet  110  arranged on the screen housing  108  is arranged in the side wall  107  configured as a single piece of the screen housing  108 , particularly preferably tangentially to the side wall  107  of the screen housing  108 . While the product flow in the screen apparatus known in the the state of the art took place from top to bottom, in the new geometry according to the invention of the screen apparatus  104  the screened granulate is evacuated through the outlet  110  arranged on the side wall  107  of the screen housing  108 . 
     In the exemplary embodiment according to  FIG.  3   , the screen housing  108  has a cylindrical design that is conical over its full installation height H, and tapers from the cover  106  to the base  118  of the screen housing  108 . Other design configurations are conceivable. In the first embodiment, the side wall  107  is designed as a one-piece conically-shaped side wall  107 . However, the side wall  107  can also be multipart, e.g. having at least two side wall sections. In addition, a plurality of inlets  109  and outlets  110  can also be arranged on the screen housing  108 . The number, position and/or geometry of the inlets  109  may vary. With regard to the outlets  110 , at least the number and/or geometry may vary. The position of the outlets  110  is at least restricted to the extent that at least one of the outlets  110  is arranged laterally on the screen housing  108 . 
     The screen apparatus  104  shown in  FIG.  3    also comprises a grinding body  114  mounted on a shaft  112 , preferably rotatably driven by a motor M, particularly preferably an electric motor or similar, in the arrow direction  113 . The shape of the grinding body  114  is matched to the screen  111 , so that the granulate can be pressed under continuous and even pressure from the grinding body  114  through the mesh of the screen  111 . For a further improved transfer of the granulate to be screened through the screen apparatus  104  comprising the screen  111 , transfer air is fed to the screen apparatus  104  via the inlet  116 . In the exemplary embodiment an inlet  116  is arranged on the side wall  107  of the screen housing  108 . The inlet  116  can also be designed to have a variable number, position and/or geometry. The inlet for the transfer air  116  is preferably arranged below the outlet  110  for the screened granulate (product), and so the reverse of that shown in  FIG.  3   , laterally on the screen housing  108 . Through the tangential movement of the air, the centrifugal forces act on the granulate and drive or carry it upwards in the direction of the outlet  110  preferably arranged above the inlet for the transfer air  116 . 
     The geometries of the screen housing  108 , screen  111  and/or grinding body  114  are preferably, as also stated in the first exemplary embodiment, matched to one another in order to further optimise the screening process. Through the matching of the various geometries to one another, apart from a reduction in the installation height, through dispensing with an additional suction shoe the internal free surface of the screen apparatus, in particular of the screen housing, is minimised. 
     In the first exemplary embodiment shown in  FIG.  3    the granulate enters the screen apparatus  104  via inlet  109 . Due to the matched geometries of the screen housing  108 , screen  111  and grinding body  114  there is little buildup or few adhesions, since the inner surface  117  in contact with the granulate during the screening process is minimal. In addition, in the circumferential direction of the screen housing  108  fewer granulate adhesions or less buildup occur or these are transported away more quickly via the outlet  110 , since through the transfer air flowing laterally via the inlet  116  in conjunction with the inner surfaces  117  with minimal contact, optimised flow conditions can be created in the screen housing  108 . The screened granulate is evacuated through the outlet  110  arranged on the side wall  107  of the screen housing  108 . 
       FIG.  4    shows a cross section of a second exemplary embodiment of a screen apparatus according to the invention  204  with a rotor disc  220  arranged in the screen housing  208  and an outlet  210  for the granulate arranged laterally on the screen housing  208  according to sectional plane X-X in  FIG.  5   . 
     Like the first exemplary embodiment, the second exemplary embodiment according to the invention comprises a screen housing  208  with a base  219 , a cover  206  and a side wall  207 . Furthermore, the screen apparatus  204  also has an inlet  209  for the granulate arranged on the screen housing  208 , an outlet  210  for the screened granulate (product) arranged on the screen housing  208 , a screen  211  arranged in the screen housing  208  and a grinding body  214  associated with the screen  211  in the screen housing  208 , wherein the outlet  210  for the screened granulate arranged on the screen housing  208  is arranged in the side wall  207  of the screen housing  208 , particularly preferably tangentially to the side wall  207  of the screen housing  208 . The grinding body  214  associated with the screen  211  is rotatably arranged on a shaft  212  driven by a motor M, preferably an electric motor or similar, in the arrow direction  213 . The grinding body  214  is arranged above the screen  211  in the screen housing  208 , whereby the granulate to be screened is continuously pressed under constant pressure through the screen  211 . The screen apparatus  204  of the second exemplary embodiment according to  FIG.  4    has an inlet  216 , not shown here, for transfer air. 
     The statements made regarding the first exemplary embodiment according to the invention in relation to the side walls, inlet, transport air inlet and outlet and so on, are equally applicable to the second exemplary embodiment according to the invention. 
     The screen apparatus  204  according to the invention in the second exemplary embodiment has a cylindrical design of the screen housing  208 , wherein the design of screen housing  208  of the screen apparatus  204  is conical over its full installation height H of the screen housing  208 , and tapers from the cover  206  to the base  219 . The configuration of the screen  211  arranged in the screen housing  208  of the screen apparatus  204  corresponds to the design of the screen housing  208 . In addition, the configuration of the grinding body  214  arranged in the screen housing  208  of the screen apparatus  204  corresponds to the design of the screen  211 . Thus, screen housing  208 , screen  211  and grinding body  214  are optimally matched to one another. 
     Unlike the screen apparatus  104  of the first exemplary embodiment the screen apparatus  204  also has a rotor disc  220 . Here, the rotor disc  220  is arranged between the screen  211  and the base  219  of the screen housing  208  of the screen apparatus  204 . The rotor disc  220  is arranged on a shaft  212  that can be driven by the motor M. Thus, rotor disc  220  and grinding body  2014  are mounted on a shaft  212  and are always driven at the same speed of rotation. It is also conceivable for the rotor disc  220  and the grinding body  214  of the screen  211  to be drivable independently of one another, by way of example in each case by a separate motor, in particular an electric motor or similar. Here, the rotor disc  220  and the grinding body  214  are arranged on different shafts. Preferably, the rotor disc  220  of the screen apparatus  204  has an at least partially conical design. The arrangement of the rotor disc  220  serves to protect the seal below the screen  211  and to prevent product remaining on the base  219  and not being transported further in the direction of the suction of the outlet  210 . Thus, an even better and more complete transfer of the product is achieved and buildup or adhesions of the granulate in the region of the base  211  of the screen housing  208  and the side wall  207  of the screen housing  208  minimised. 
     A further improvement in the product transfer is achieved in that the inlet  216 , not shown here, for transfer air is arranged on the side wall  207  of the screen housing  208 ; preferably the inlet  216  not shown here, for transfer air is attached tangentially to the side wall  207  of the screen housing  208 . 
       FIG.  5    illustrates a top view of the second exemplary embodiment of the screen apparatus  204  according to the invention with an outlet  210  for the granulate arranged laterally on the screen housing  208  and an inlet  216  for transfer air. The grinding body  214  driven by a motor M and arranged on a shaft  212  is arranged above the screen  211  in the screen housing  208 , which has a cover  206 , not shown here, and a base  219 , not shown here, as well as a side wall  207 , and is located in the sectional plane X-X. The inlet  216  for the transfer air is arranged on the side wall  207  of the screen housing  208 , laterally offset from the sectional plane X-X. 
     By the rotation of the grinding body  214  in the arrow direction  213  the granulate is pressed or pushed through the screen  211 . The screening process is optimised by the transfer air that enters the inlet  216 . The combination of rotating grinding body  214  and transfer air results in an improved granulate screening process. 
       FIG.  6    shows a cross section of a schematic representation of a part of a high-shear granulator  2  with a third exemplary embodiment of a screen apparatus  304  according to the invention arranged on a high-shear granulator  2 . The inlet  316  for the transfer air is arranged tangentially to the cylindrical screen housing  308  of the screen apparatus  304 . The outlet  310  is similarly tangentially arranged on the cylindrical screen housing  308  of the screen apparatus  304 . In the exemplary embodiment, the inlet  316  is located in the horizontal sectional plane Y-Y through the screen apparatus  304 ; in the third exemplary embodiment the outlet  310  is located in the similarly horizontal sectional plane Z-Z through the screen apparatus  304 . In the third exemplary embodiment the horizontal sectional planes Y-Y and Z-Z are offset to one another above the installation height H of the screen housing  308  of the screen apparatus  304 . However, such an offset between sectional planes Y-Y and Z-Z is not absolutely essential. In the third exemplary embodiment, the transfer air is fed to the screen housing  308  of the screen apparatus  304  through the inlet  316  and compared to the discharge of the screened granulate through the outlet  310  of the screen housing  308  of the screen apparatus  304  is located in a higher position of the screen housing  308  of the screen apparatus  304  in the x-direction. 
     The statements made regarding the first exemplary embodiment according to the invention in relation to the side walls, inlet, transport air inlet and outlet and so on, are equally applicable to the third exemplary embodiment according to the invention. 
     The granulate coming from the high-shear granulator  2  enters the screen apparatus  304  and is pushed by a grinding body  314 , not shown here, through the screen  311  with continuous pressure evenly distributed across the screen  311 . Through the inlet  316  arranged in the upper region of the screen housing  308  tangentially to the side wall  307  of the screen housing  308  transfer air also enters the screen housing  304  of the screen apparatus  308  and a helical, downward airflow opposite to the x-direction is generated within the cylindrical screen housing  308  of the screen apparatus  304 . This airflow carries with it granulate that has built up or adhered on the way through the screen housing  308  to the screen housing  308  in the direction of the outlet  310  and thereby prevents a blockage of the screen apparatus  304  by the granulate itself. By means of the outlet  310  arranged tangentially to the side wall  307  of the screen housing  308  optimum suction of the granulate and the transfer air is ensured. 
       FIG.  7    shows a top view of the schematic representation shown in  FIG.  6    of a screen apparatus  304  according to the invention arranged on a high-shear granulator  2  according to the third exemplary embodiment. It is clear here that the inlet  316  for transfer air and the outlet  310  for the product are arranged on the same side of the screen housing  308 . Furthermore, both the inlet  316  and the outlet  310  run tangentially to the side wall  307  of the screen housing  308  of the screen apparatus  304 . 
     For each geometry of the screen apparatuses  104 ,  204  and  304  according to the invention that is used, it is sufficient to draw in the transfer air, preferably via an outlet  110 ,  210 , or  310  arranged tangentially to the side wall  107 ,  207  or  307  and thereby achieve a faster and more reliable product transfer.