Abstract:
A solid bowl screw centrifuge includes a centrifuging chamber and a rotatable drum having a horizontal axis of rotation. The rotatable drum surrounds the centrifuging chamber. Also included is a rotatable screw arranged in the rotatable drum, at least one solids discharge, at least one liquid discharge duct and a peeling disk via which liquids are discharged through the liquid discharge duct. Further included is a blocking chamber connected to an output side of the peeling disk.

Description:
BACKGROUND 
     The present disclosure relates to a solid bowl screw centrifuge that includes a centrifuging chamber and a rotatable drum having a horizontal axis of rotation. The rotatable drum surrounds the centrifuging chamber. Also included is a rotatable screw arranged in the rotatable drum, at least one solids discharge, at least one liquid discharge duct and a peeling disk via which liquids are discharged through the liquid discharge duct. Further included is a blocking chamber connected to an output side of the peeling disk. The present disclosure further relates to a method for operation of the centrifuge. 
     A solid bowl screw centrifuge of the above-mentioned type is shown by German Patent Document DE 195 00 600 C1. German Patent Document DE 40 14 552 C1 shows a separator with a vertical axis of rotation having a peeling disk and a blocking disk between which a gas can be fed to prevent a degassing of solvents. 
     The solid bowl screw centrifuge disclosed in German Patent Document DE 43 20 265 A1 is equipped with a weir on the liquid outlet side, which weir has a passage. An orifice plate, which is stationary relative to the drum during its rotation, is assigned to the passage. By way of a threaded bush, this orifice plate is axially displaceable. By rotating the threaded bush, the distance between the weir and the orifice plate can be changed. The resulting change of the outflow cross-section causes a change of the liquid level in the centrifugal drum, so that a continuous adjustment of this liquid level can be achieved by displacing the orifice plate. 
     From German Patent Document DE 39 04 151 A1, a diaphragm plate situated on the screw is known. Nozzles on the outer circumference are used for minimizing the energy consumption. A processing of sensitive products with a gas-tight sealing-off with respect to the environment cannot be achieved by this construction. 
     From German Patent Document DE 198 30 653 C1 of the above-mentioned type, it is known to implement the liquid discharge of an open solid bowl screw centrifuge by of a peeling disk which is followed by a labyrinth seal, in order to return product droplets to the peeling disk. According to this construction, no sealing-off is required with respect to the exterior space. However, solid bowl screw centrifuges with peeling disks in which the product space is sealed off toward the outside are also in demand. The present disclosure addresses such a solid bowl screw centrifuge by simple constructive devices. 
     SUMMARY 
     The present disclosure relates to a sold bowl screw centrifuge that includes a centrifuging chamber and a rotatable drum having a horizontal axis of rotation. The rotatable drum surrounds the centrifuging chamber. Also included is a rotatable screw arranged in the rotatable drum, at least one solids discharge, at least one liquid discharge duct, and a peeling disk via which liquids are discharged through the liquid discharge duct. A blocking chamber is connected to an output side of the peeling disk and includes an annulus having a first siphon disk arranged therein. The blocking chamber is a hydrohermetic blocking chamber to seal off the centrifuging chamber from its surroundings via a sealing liquid that is independent of material to be centrifuged. A feed line is assigned to the blocking chamber to feed the sealing liquid. The rotatable screw includes a second siphon disk extending from the screw radially to the outside into the centrifuging chamber. 
     The present disclosure also relates to a method of operating the solid bowl screw centrifuge noted immediately above. The method steps include, turning on the centrifuge and feeding the sealing liquid that is independent of the material to be centrifuged through the feed line into the blocking chamber to seal off the centrifuging chamber from its surroundings. 
     The blocking chamber with the sealing liquid supply, which may be in combination with two blocking or siphon disks, permits a reliable sealing-off of the centrifuging chamber with respect to the surrounding atmosphere. In contrast, in German Patent Document DE 198 30 653 C1 of the above-mentioned type, the product can still come in contact with the surrounding atmosphere because of the labyrinth seal. 
     Blocking chambers are also known per se from centrifuges with a vertical axis of rotation, a separate sealing liquid also being guided into these blocking chambers (German Patent Document DE 196 31 226). Blocking chambers in the case of such separators are also known from German Patent Document DE 657 473. However, it has not been considered and apparently has not been seen as being beneficial to implement a blocking chamber in the case of centrifuges with a horizontal axis of rotation which blocking chamber is acted upon by a separate sealing liquid independent of the centrifuge material. 
     When a pressure is built up in the interior of the decanter or of the solid bowl screw centrifuge, a gas (such as CO2) dissolved in the centrifuge product (for example, a beverage) would under certain circumstances partially escape from the solid bowl screw centrifuge without a blocking chamber arrangement with two siphon disks and the sealing liquid feed. This is prevented by the centrifuge of the present disclosure. 
     By the blocking or siphon disk in the blocking chamber, sufficient pressure can be built up in a simple manner, so that a gas, such as CO2, is kept as a liquid. By varying the diameter of the blocking and siphon disk, the pressure in the blocking chamber can be varied, which amounts to up to 4 bar, and more particularly to 0.5 to 2.5 bar. The pressure influences the type of the conveyance of the solids and/or their consistency. 
     The feed line and a discharge bore lead into an annulus of the blocking chamber and permit the continuous feeding and discharging of the sealing liquid into the blocking chamber and out of the blocking chamber. As a result, a continuous cleaning of the blocking chamber can be implemented in a much simpler manner than in German Patent Document DE 196 31 226 A1. As a result, the forming of deposits in the blocking chamber of the present disclosure can be effectively prevented. The centrifuge of the present disclosure therefore also meets high hygienic requirements. 
     Since the liquid discharge takes place by a peeling disk, which is followed in a direct manner by the blocking chamber, a dissolved gas, such as CO2, can be kept at least largely as a liquid to be discharged or to be processed. This considerably simplifies the processing of products, such as beer. 
     The blocking chamber as well as the peeling disk are arranged on the drum side or toward the drum with respect to the main bearing or bearings of the drum. This permits a simple development of the construction. This also results not only in a durable sealing-off with respect to the surrounding atmosphere but, under certain circumstances, also in a sealing-off with respect to product contamination by oil mist of a liquid-side main bearing. 
     Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a solid bowl screw centrifuge, according to the present disclosure. 
         FIG. 2  is an enlargement of a portion of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a solid bowl screw centrifuge  1  with a rotatable drum  3  having a horizontal axis of rotation in which a rotatable screw  5  is arranged. The drum  3  and the rotatable screw  5  each include an essentially cylindrical section  43  and a conically tapering area or section  45 . 
     An axially extending centric feed pipe  7  is used for feeding the centrifuge material  8  by way of a distributor  9 , which is shown, for example, perpendicular with respect to the feed pipe  7 . The centrifuge material  8  is then fed into a centrifugal or centrifuging chamber  11  between the rotatable screw  5  and the drum  3 . 
     When, for example, a sludgy pulp is fed into the centrifuge  1 , solid particles S are deposited on or near a drum wall. A liquid phase L develops farther toward the inside of the drum  3 . 
     The screw  5 , disposed by bearing  6 , rotates at a slightly lower or higher speed than the drum  3  and conveys centrifuged solids S toward the conically tapering section  45  and out of the drum  3  via a solids discharge, shown, for example, by arrow and numerical designation  41 . 
     In contrast, the liquid phase L flows to a larger drum diameter at a rearward end of the cylindrical section  43  of the drum  3  and is guided there through a weir  15  into a peeling disk chamber  17  which axially adjoins the centrifuging chamber  11 . The peeling disk chamber  17  has a diameter which is smaller in comparison to a diameter of the centrifuging chamber  11 . 
     A peeling disk  19 , for discharging the liquid phase L, is arranged in the peeling disk chamber  17  (see also  FIG. 2 ), which is adjoined by a discharge duct  20  discharging the liquid phase L from the drum  3 . The peeling disk  19  is arranged directly on the feed pipe  7  which is stationary during an operation of the centrifuge  1 . A sealed-off gap-free arrangement is implemented between the peeling disk  19  and the feed pipe  7 . 
     In the conically tapering area  45  of the drum  3 , the screw  1 , in front of the solids discharge  41 , has a siphon disk  21  which extends from the screw  5  radially toward the outside into the centrifuging chamber  11  and the siphon disk  21  is immersed into a liquid level P 1 . 
     As a result of the immersion, an interior area or centrifuging area in the centrifuging chamber  11 , shown to the right of the siphon disk  21  in  FIG. 1 , is hermetically sealed off with respect to the surroundings or the surrounding atmosphere. It would also be conceivable to arrange additional siphon disks in the conically tapering area  45  of the drum  3  in order to influence the consistency of the centrifuged solids  5  in this manner (not shown here). 
     In the peeling disk chamber  17 , a ring disk or shoulder  23  is arranged on the side of the peeling disk  19  pointing to the centrifuging chamber  11 , which ring shoulder  23  extends radially from the inner circumference of the peeling disk chamber  17  toward the inside of the centrifuge  1 . 
     The liquid level P 1  forms between the siphon disk  21  and the ring shoulder  23  during the operation of the centrifuge  1  because the siphon disk  21  and the ring shoulder  23  overlap in the radial direction or because the siphon disk  21  and ring shoulder  23  are correspondingly adapted to one another. 
     In contrast, between the ring shoulder  23  and the peeling disk  19 , a liquid level P 2  extends to an inlet opening  25  (see  FIG. 2 ) of the peeling disk  19 . The liquid level P 2  can be varied by at least slightly throttling the peeling disk  19 . 
     On a side of the peeling disk  19  facing away from the ring shoulder  23  the peeling disk chamber  17  extends radially toward the inside close to the feed pipe  7  or to a diameter smaller than the diameter of the screw  5 , and leads into an axial passage  27 . Axial passage  27  is adjoined in an axial direction by an annulus  29 , which acts as a blocking chamber, also identified with numerical designation  29 . Blocking chamber  29  leads into an axial discharge duct  31  for sealing liquid SL on the outer circumference of the feed pipe  7 . The inside diameter of the discharge duct  31  for the sealing liquid SL is smaller than the inside diameter of the passage  27 , so that sealing liquid SL overflowing from the blocking chamber  29  flows out through the discharge duct  31 . 
     In the blocking chamber or annulus  29 , another siphon or blocking disk  33  is stationarily arranged on an inner circumference and extends from an inside of the drum  3  radially to an outside of the drum  3  into the blocking chamber  29 . 
     A feed line  35  arranged parallel to the feed pipe  7  on its outer circumference leads into the centrifuge  1  from the outside and permits a direct feeding of the sealing liquid SL, such as water, which is independent of the centrifuge material  8 , into the blocking chamber  29 . 
     A discharge bore  37  is on a circumference of the blocking chamber  29  at an acute angle with respect to an axis of rotation  47  of the drum  3  and extends radially to the outside out of the drum  3  permitting the continuous discharge of sealing liquid SL from the annulus  29 , which causes a cleaning of the blocking chamber  29 . 
     During an operation of the centrifuge  1 , that is, during rotations of the drum  3  and the screw  5  a liquid level P 3  of the sealing liquid SL forms in the block chamber  29 , which liquid level P 3  seals off the interior of the drum  3  against the surrounding atmosphere when the feeding amount of sealing liquid SL into the blocking chamber  29  is larger than the discharge amount, which is adjusted by a dimensioning of the discharge bore  37 . Excess water which does not flow off through the discharge bore  37  flows off through the discharge duct  31 . 
     By siphon disk  33  in the blocking chamber  29 , however, a sufficient pressure can be built up so that gas is kept as a liquid. By varying the diameter of the blocking and siphon disk  33 , the pressure in the blocking chamber  29  can be varied. The pressure influences the type of the conveyance of the solids  5  and/or their consistency. 
     Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The spirit and scope of the present disclosure are to be limited only by the terms of the appended claims.