Patent Publication Number: US-6338773-B1

Title: Device for dewatering solid/liquid suspensions, especially pulp suspensions

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is the national phase of International Application No. is a 371 of PCT/EP98/04045 filed Jul. 1, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for dewatering solid/liquid suspensions especially pulp suspensions, where the suspension is dewatered between two belts, one dewatering zone being designed as wedge zone. 
     This type of device is known, for instance, from AT 402.517. To achieve a high dryness, so-called S-module rolls with area pressing are used here, and subsequently also several press nips with line pressing. Due to the multiplicity of deflection and press rolls, the machine is comparatively long. 
     SUMMARY of the INVENTION 
     The aim of the invention is, therefore, to simplify the known device and to achieve a shorter and more compact design and thus to reduce costs. 
     According to the invention, this is achieved by the pair of rolls following the wedge zone imparting both area pressure and line pressure on the pulp web formed by the pulp suspension. By combining the S-module rolls imparting the area pressure with a press nip with line pressing force two rolls can be done without, which gives a far shorter and more compact design. With fewer rolls and bearings, costs can be saved. 
     An advantageous design of the invention is characterized by the wedge height at the outlet end, especially over the entire web width, being adjustable in its height. This allows production of the most varied basis weights. 
     A favorable advancement of the invention is characterized by the first combined deflection and press roll of the pair of rolls being arranged below the end of the wedge zone and directly adjacent to it, with the wedge zone possibly being extended beyond the first subsequent combined deflection and press roll and the opposite part reaching into the gap between the wire belt and the roll. This further shortens the machine, whereby through this design the pulp web between the wires is stabilized as far as into the first combined deflection and press roll, preventing the fibers from being shoved back and subsequently also lateral squeezing out of the pulp material ahead of the S-module and the press nip. Also, this prevents subsequent stretching of the kilter cake and thus re-wetting. Especially with hard to dewater material, the throughput performance of the dewatering unit is thereby increased. 
     An advantageous advancement of the invention is characterized by the wrap angle of the first combined deflection and press roll being between 10 and 90 degrees, preferably approximately 60 degrees. 
     An further advancement of the invention is characterized by the wrap angle of the second combined deflection and press roll being between 30 and 120 degrees, preferably approximately 100 degrees. 
     An advantageous development of the invention is characterized by the wrap angle/e being changeable, especially adjustable. 
     A favorable design of the invention is characterized by only one upper and/or lower deflection roll at the beginning of the wedge being in each case provided as stretcher roll immediately at the beginning of the wedge. This means that further rolls can be saved, which causes the system to be shortened accordingly and leads to essential cost savings. 
     A favorable advancement of the invention is characterized by the upper part of the wedge being especially automatically adjustable, for instance, elastically and by the opposite part being fixed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in the following in examples based on the drawings, in which 
     FIG. 1 shows a dewatering device according to the state of the art, 
     FIG. 2 a dewatering device as per the invention, and 
     FIG. 3 is a simplified, enlarged view of part of the S-module area of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The dewatering device  1  with a wedge area  2  and a further dewatering area, especially an S-module area  3 , is shown in FIG.  1 . Here the upper wire or filter belt  4  runs over an upper deflection roll  6  whose position can be adjusted and regulated, and subsequently over a deflection roll  7  into the wedge formed by the plates  10  and  11 . The second wire or filter belt  5  runs over a pertinent deflection roll  8  and a further deflection roll  9  also into the wedge. The material to be dewatered, for instance pulp, is also fed into the wedge through a headbox  12 . The upper part  10  of the wedge and the lower part  11  of the wedge are mechanically connected via a threaded spindle  13  and their spacing can be adjusted. After leaving the gap the belts  4  - and  5  with the interposed pulp web are deflected around S-module rolls  21  and  22 , which induces further dewatering. Here the upper part  10  of the wedge is adjustable in its height by a pneumatic or hydraulic hose. The compressed air or hydraulic fluid is fed through a connection  15 . To limit the minimum respectively maximum adjustment, stop screws  16  are used. A glide plate  17  serves to take up the axial forces. Furthermore a support  18  for cantilevering, i.e. for exchanging the endless wire belts, is provided. To ensure the least possible influence on the ambience, a hood  19  is integrated into the upper part  10  of the wedge and a filtrate tray  20  into the lower part  11  of the wedge. 
     It can be seen from FIG. 2 that the upper deflection roll  6 , whose position can be adjusted and regulated by a hydraulic or a pneumatic cylinder  7 ′, is the only deflection roll for the upper wire belt  4 . There is consequently no longer a lower deflection roll, whereby-a far more compact design can be achieved. The same applies by analogy to the lower deflection roll  8 , which can be adjusted and regulated by a hydraulic or a pneumatic cylinder  9 ′. The two S-module rolls  21 ,  22  are in this case designed as combined deflection and press rolls. Pressing the roll  22  to roll  21  is done by hydraulic cylinder  23 , giving a nip  24  with additional line force. Following this, further pairs of press rolls  25 ,  26  are provided so that at the end of the dewatering device the desired dryness can be achieved. 
     Here, the first combined deflection and press roll  21  of the roll pair is arranged below the end of the wedge zone  10 ,  11  and directly adjacent to it, with the wedge plate  10  being extended beyond the combined deflection and press roll  21  and the opposite part of the wedge plate  11  reaching into the gap between wire belt  5  and roll  21 . The wrap angle α of the first combined deflection and press roll  21  is approximately 60 degrees, the wrap angle β of the second combined deflection and press roll  22  approximately 100 degrees. The invention is not limited to the examples, for instance, the arrangement of the combined deflection and press rolls could be reversed, i.e. the first roll could be arranged on the top. Other adjustment and pressing mechanisms for the deflection and press roll are also possible.