Liquid purification or separation – Filter – Movable medium
Patent
1999-01-25
1999-12-21
Lithgow, Thomas M.
Liquid purification or separation
Filter
Movable medium
210109, 210111, 210137, 210143, 100118, 100151, 100152, 100153, B30B 924, B01D 3304, B01D 33056, C02F 1112
Patent
active
060036842
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for dewatering solid-liquid suspensions, in particular pulp suspensions, on which the suspension is dewatered between two belts, a dewatering zone being formed in the shape of a wedge zone.
Such devices, as are known from AT 385.793, for example, have the disadvantage of being severely limited in their production spectrum and in the obtainable dry content when producing mats with different basis weights. A fixed gap at the end of the wedge only allows a small, restricted range of basis weights. Here, a high basis weight yields a high dry content and a low basis weight a low dry content. If the pressure is too great at the end, particularly with pulps that are difficult to dewater, the pulp is squeezed out at the sides. Further due to the high pressure also the deckle sealing in the wedge zone may be damaged. As the basis weight rises, this leads to higher pressures and, as a result, the drive power the machine requires because of the frictional force is so great that the machine comes to a standstill.
The aim of the invention is, thus, to create a machine which also permits high dry content levels at high basis weights, without the pulp, particularly if it is difficult to dewater, being squeezed out at the sides or the deckle sealings being damaged, and where the risk of the machine coming to a standstill is virtually eliminated.
According to the invention, this is achieved by making the wedge height adjustable, particularly over the entire belt width, at the wedge outlet end, in particular automatically, e.g. elastically. Since the wedge height at the outlet end can be adjusted, the correct gap can always be set for the appropriate basis weight.
An advantageous further development of the invention is characterized by the top section of the wedge, or alternatively the bottom section of the wedge, being adjustable, in particular automatically, e.g. elastically. With these variants, the wedge can be set at the optimum height to suit the other structural features of the machine.
A favorable configuration of the invention is characterized by the adjustment being made using one or more pneumatic elements arranged over almost the entire machine width, with flexible tubes or pneumatic cylinders being provided as pneumatic elements. As an alternative, the adjustment can be made using one or more hydraulic elements arranged over almost the entire machine width, with bellows, flexible tubes or hydraulic cylinders being provided as hydraulic elements. By using pneumatic or hydraulic elements to set the wedge height at the outlet end, the gap can set itself automatically with the pressure occurring. Particularly the embodiment with flexible tubes or bellows extending over almost the entire machine permits the wedge height to be adjusted to suit the basis weight in this way, even if the pulp is not evenly distributed, for example if a wedge plate is slanted. By adapting to prevailing conditions, the machine also remains operative if there are brief pressure fluctuations in the pulp or if the mat is thicker or arches in places. Thus, greater reliability of service is provided.
A favorable further development of the invention is characterized by either the top section or the bottom section of the wedge being spring-supported.
A favorable configuration of the invention is characterized by the top and bottom sections of the wedge being connected mechanically, in particular adjustably, at the side of the headbox. Due to the mechanical connection between the top and bottom sections of the wedge on the side facing the headbox, corresponding influence can be exerted on the thickness of the filter cake produced and also on dewatering of the mat by the existing apropriate length of the wedge zone.
A favorable further development of the invention is characterized by the maximum and minimum gap adjustment being restricted by limit stops. By limiting the maximum adjustment, dewatering of the material is always guaranteed, whereas a restriction on minimum adjustment avoids damage to the machine in n
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Eickhoff Karl
Reck Georg
Scheucher Peter
Andritz-Patentverwaltungs-Gesellschaft m.b.H.
Lithgow Thomas M.
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