Method and device for handling cellulose pulp

Abstract

The invention concerns a method and a device for the dilution of dewatered cellulose pulp that maintains a consistency of 30% or greater. By shredding of the pulp to a finely divided dry granulate, dilution to a homogeneous consistency in the medium consistency range can take place exclusively through hydrodynamic effects from the addition of dilution fluid. The dilution fluid is added to the granulate at a position at which the granulate is in free fall in a stand pipe 22, 40 and above a level Liq LEV of diluted pulp in the stand pipe. A number of nozzles are arranged around the periphery of the stand pipe, directed in towards the centre of the stand pipe, obliquely downwards in the direction of fall of the granulate. It is possible through this simplified procedure to avoid completely the conventional dilution screws, and this reduces the investment costs and is operating costs, while at the same time unnecessary mechanical influence of the pulp fibres can be avoided.

1 . A method for the removal of dewatered cellulose pulp from a dewatering press, comprising: 
 applying cellulose pulp to an outer surface of two counter-rotating dewatering drums of a dewatering press, the cellulose pulp having an initial consistency in a range of 4-12%;    feeding out the cellulose pulp after a final dewatering nip of the dewatering press in a form of a continuous dewatered mat that maintains a consistency of 30% or higher;    feeding the dewatered mat perpendicularly to a shredder screw having an axis of shredding that is arranged essentially parallel to axes of rotation of the dewatering drums and the shredder screw having an outlet defined therein at one end of a surrounding outer cover;    shredding the dewatered mat in the shredder screw to produce a granulated pulp having a normalized granulate size distribution in a range of 5-40 mm;    feeding out the granulated pulp from the outlet of the shredder screw to fall freely in a stand pipe connected to an outlet end of the shredder screw;    adding a dilution fluid under pressure into the stand pipe through a number of fluid jets arranged around a periphery of an upper end of the stand pipe and above a surface liquid level (Liq LEV ) of diluted granulated pulp established in LOWER END OF the stand pipe,    the added dilution fluid establishing a consistency of the diluted granulated pulp in a range of medium consistency 8-16%;    more than 75-90%, of the added dilution fluid being added through the fluid jets arranged above the surface liquid level (Liq LEV ) established in a lower end of the stand pipe;    exclusively diluting the granulated pulp under an influence of hydrodynamic effect from the addition of the dilution fluid through the fluid jet to reduce the consistency of the granulated pulp from 30% or higher at an upper end of the standpipe to a medium consistency of 8-16% at the lower end of the standpipe without using any mechanical agitators in the standpipe; and    feeding the diluted granulated pulp onwardly to subsequent treatment steps for the diluted granulated pulp by pumping the diluted granulated pulp from the lower end of the stand pipe.    
   
   
       2 . The method according to  claim 1  wherein the addition of dilution fluid from the fluid jets takes place in a form of pressurized fluid jets directed obliquely downwardly in a fall direction of the granulated pulp in the stand pipe  
   
   
       3 . The method according to  claim 1  wherein the fluid jets are directed at an angle of 45±15° relative to a vertical direction and a fall direction of the granulated pulp.  
   
   
       4 . A device for the removal of dewatered cellulose pulp from a dewatering press comprising: 
 a first rotatable drum in operative engagement with a second rotatable drum so that a dewatering nip is formed therebetween;    a dewatered mat disposed in the dewatering nip;    a shredder screw having an axis of shredding parallel to an axis of rotation of the rotatable drums, the shredder screw having an inlet defined therein for receiving the dewatered mat, the dewatered mat extending from the dewatering nip into the inlet of the shredder screw;    the shredder screw having means for shredding the dewatered mat into granulated pulp;    the shredder screw having an outlet defined therein;    a vertical stand pipe having an upper end connected to the shredder screw and in operative engagement with the outlet of the shredder screw, the standpipe having a lower end;    the upper end of the vertical standpipe having a pressurized chamber device arranged around a periphery of the standpipe, the pressurized chamber device containing a dilution fluid;    a plurality of nozzles extending through a wall of the pressurized chamber device so that an inside of the pressurized chamber device is in fluid communication with the stand pipe;    the lower end of the stand pipe having diluted granulated pulp disposed therein, the nozzles being directed towards the granulated pulp to dilute the granulated pulp with the dilution fluid above a level of diluted granulated pulp established in the lower end of the stand pipe; and    a pump arranged at the lower end of the stand pipe adjacent to a bottom of the stand pipe for forwarding the diluted granulated pulp to subsequent treatment steps.    
   
   
       5 . The device according to  claim 4  wherein at least four nozzles are arranged around the periphery of the stand pipe.  
   
   
       6 . The device according to  claim 5  wherein each nozzle is directed g towards a center of the stand pipe and obliquely downwards at an angle 45±15° relative to a vertical direction and a fall direction of granulated pulp.  
   
   
       7 . The device according to  claim 6  wherein all nozzles are connected to a common distribution chamber for the dilution fluids which is pressurized with a pressure-raising device means.