Helix centrifuge with removable heavy phase discharge nozzles

Details Helix centrifuge with removable heavy phase discharge nozzles Helix centrifuge with removable heavy phase discharge nozzles

2000-04-28

2001-09-18

Cooley, Charles E. (Department: 1723)

Imperforate bowl: centrifugal separators

Rotatable bowl

Including driven material-moving means therein

C494S056000

Reexamination Certificate

active

06290636

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a solid bowl helix centrifuge for continuous separation of free-flowing substances that have different densities, and particularly for continuously separating a solid-liquid mixture.
BACKGROUND OF THE INVENTION
DE-A 41 12 957 describes a solid bowl helix centrifuge somewhat similar to the solid bowl helix centrifuge whose principle features are indicated above. In the earlier-model, the rotor is delimited by face walls at both extremities and the decanting apertures in the wall of the cylindrical drum are very small; this has the effect of blocking the light phase that is to be decanted. The heavy phase is removed through narrow discharge apertures in the conical drum section. Since the face of the conical drum is closed, it is practically impossible to avoid clogging at this point. This in turn compromises the degree of purity of the light phase. The fact that the mixture to be separated enters the centrifuge in the front section of the cylindrical drum exacerbates this deficiency, since the heavy phase is deposited on the internal wall over the entire length of the rotor and must be transported from there by the scroll conveyor against the flow of the light phase. As a consequence, the scroll conveyor requires a relatively powerful motor.
A solid bowl helix centrifuge of the type disclosed herein is also shown and discussed in U.S. Pat. No. 5,792,039. Here too, the extremity wall of the conical drum is blind. In this case, the heavy phase that has entered the conical drum must be returned to the cylindrical drum axially of the scroll conveyor. To this end, the helices in the conical and the cylindrical drums are constructed to operate in opposing directions. The discharge ports for the heavy phase form a ring in the wall of the cylindrical drum and are arranged in such a way that they are axially offset toward the face wall of the cylindrical drum relative to the inlet apertures of the chamber in the hollow shaft. The effect of this configuration is that the heavy phase is moved in one direction within the conical drum and in the opposite direction in the cylindrical drum.
The disadvantages of the prior art are overcome by the present invention, and an improved solid bowl centrifuge is hereinafter disclosed which offers significant improvements over prior art centrifuges.
SUMMARY OF THE INVENTION
The centrifuge according to a preferred embodiment includes a rotor that consists of a cylindrical and a conical drum. The rotor wall is furnished with discharge ports for the heavy phase, and weirs for the light phase are arranged on the frontal wall of the cylindrical drum. The centrifuge includes a rotatable scroll conveyor inside the rotor for the purpose of transporting the heavy phase towards the discharge ports. A mixture feed pipe is arranged coaxially within the hollow shaft supporting the helix of the scroll conveyor, and opens into a chamber within the hollow shaft, from which chamber feed apertures lead to the helix.
The task of this invention has been to produce a helix centrifuge in which the heavy phase is conveyed from the chamber formed in the hollow shaft to the discharge ports by the shortest possible route and against the flow of the light phase without causing blockage in the conical drum.
With respect to a solid bowl helix centrifuge of such type, the present invention provides that, at least in the conical drum, the discharge ports take the form of nozzles that are followed by non-restrictive discharge ports in the end section of the conical drum for the heavy phase or a third, intermediate phase.
Functioning is further improved if the discharge ports in the form of nozzles are arranged in rings in the wall of the rotor and are on the same longitudinal section of the rotor or are axially offset relative to the end section of the conical drum.
The present invention represents a considerable advance over the prior art in that the heavy phase is transported to the discharge ports against the flow of the light phase immediately from the feed apertures, while the light phase migrates in the opposite direction towards the weirs in the face wall of the cylindrical drum, thereby avoiding the risk of renewed contamination with the heavy phase. Since the heavy phase is removed rapidly, the degree of purity of the light phase remains very high. There is an additional advantage in that the heavy phase has to travel only a short distance in the area of the chamber feed apertures. As a consequence, the spin drive of the scroll conveyor requires a low torque. Finally, the non-restrictive discharge ports are in the end section of the conical drum, so that a blockage cannot occur at this point, as would happen if larger particles of the heavy phase were unable to pass through the narrow discharge ports of the nozzles. If the distance radial to the rotor axis is small enough between the non-restrictive discharge ports and the nozzle discharge ports, the helix centrifuge may operate in three phase mode, in which an intermediate phase is discharged through the non-restrictive discharge ports.
The nozzle-shaped discharge ports in ring arrangements may be arranged on any longitudinal section of the rotor, and preferably on the conical drum, depending on the intended density and consistency of the heavy phase.
In an improved version of the invention, it may be advantageous if the conical drum is furnished with multiple discharge ports, arranged in rings at fixed axial intervals. It is then beneficial if the discharge ports of the nozzles that are located closer axially to the end section of the conical drum have a reduced aperture profile. In this way, it is possible to use the nozzles to separate different particle sizes in the heavy phase.
According to a further feature of the invention, provision has been made so that the nozzles are removable and screwed into threaded holes in the rotor wall. When the nozzles are not in place, these threaded holes may be plugged with screw bolts. This in turn allows he possibility of configuring a standard centrifuge in which, depending on the desired density and consistency of the heavy phase, the redundant discharge ports are closed off.
These and further objects, features and advantages of the present invention will become apparent from the following detail description, wherein reference is made to the figure in the accompanying drawing.


REFERENCES:
patent: 3575709 (1971-04-01), Ferney
patent: 4298159 (1981-11-01), Epper et al.
patent: 4339072 (1982-07-01), Hiller
patent: 5234400 (1993-08-01), Kluge
patent: 5252209 (1993-10-01), Retter
patent: 5342281 (1994-08-01), Unkelbach et al.
patent: 5545119 (1996-08-01), Schlip et al.
patent: 5584791 (1996-12-01), Grimwood et al.
patent: 5792039 (1998-08-01), Green et al.
patent: 3620912 (1987-12-01), None
patent: 4112957 (1992-10-01), None
patent: 670306 (1929-11-01), None
patent: 372679 (1932-05-01), None

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