Imperforate bowl: centrifugal separators – Process
Patent
1991-10-11
1994-10-18
Scherbel, David A.
Imperforate bowl: centrifugal separators
Process
494 6, 494 10, 494 36, 210376, B01D 2126, B01D 3306, B01D 4300
Patent
active
053563662
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the operation of a pusher centrifuge, in which a pusher plate is cyclicly moved relative to a perforated drum or basket in the axial direction between an advanced and a retracted position in a forward or reverse movement, the pusher centrifuge being discontinuously supplied with a material mixture in synchronous manner with the pusher cycle of the pusher plate and a solid cake is formed on the perforated drum.
DE-OS 19 39 211 discloses a pusher centrifuge, which has two centrifugal drums and in which the pusher members are moved cyclicly relative to the drums axially between an advanced and a retracted position. In the case of said pusher centrifuge fresh centrifugal material is constantly supplied by means of a pipe and is fed into one or other of the centrifugal drums. With respect to each drum, the fresh centrifugal material is supplied during the return movement of the particular pusher plates, beginning in the furthest forward position of the plates and continuing to their furthest rearward position. Thus, two feed zones of the pusher centrifuge are alternatively supplied with fresh centrifugal material.
It is disadvantageous in said pusher centrifuge that the solid cake dehumidified in the inner drum is initially pushed onto the outer drum and is not immediately supplied to a solid receiving area. Thus, on the outer drum the dehumidified solid cake is again moistened by the supply of fresh centrifugal material and must then be dehumidified again prior to the supply to the solid collecting area. Thus, there is no high dehumidified solid throughput. In addition, in said pusher centrifuge, the construction is complicated due to the use of two drums and two feed hoppers, so that it is expensive and fault-prone.
DE-OS 31 04 635 discloses a filling device for centrifuges, in which a pusher plate is moved relative to a drum constantly and in the axial direction between an advanced and a retracted position. The supply to the centrifugal drum is stopped during the forward movement of the pusher plate and before reaching the furthest forward plate position. At the start of the return movement of the pusher plate the supply of the fresh centrifugal material to the drum is recommenced, supply also taking place when the pusher plate has reached its completely retracted position. Consequently the drum is supplied with fresh centrifugal material on leaving the advanced position of the pusher plate and continues over and beyond the plate retracted position until, on its way to a completely advanced position, the pusher plate again interrupts the centrifugal material supply.
It is disadvantageous in said pusher centrifuge that the pusher plate does not completely strip off the solid cake being formed during its forward movement and instead zonally pushes said cake in front of it until the solid cake end has reached the drum end. However, during the forward movement of the pusher plate, the pressure rise only starts after a certain distance when the solid cake has already accumulated. Due to the very short pusher plate travel with respect to the drum length a reliable forward movement of the solid cake is not ensured, i.e. the cake will always increasingly accumulate. The consequence of the accumulation of the solid cake is that on the one hand the desired solid cake quantity is not pushed away from the drum and on the other the desired dehumidification in the rear drum area is no longer achieved, because the solid cake quantity significantly increases as a result of the accumulation and a low residual humidity level can no longer be achieved.
The object of the invention is to provide a process making it possible to obtain a particularly high mixture throughput with low residual humidity.
According to the invention this object is achieved in that at least most of the material mixture is only supplied when the pusher plate has commenced the reverse movement from the advanced position, that the mixture supply is completely ended by a material-dependent rest period prior to the time
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patent: 5021158 (1991-06-01), Schiele
Alexander Reginald L.
Scherbel David A.
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