Liquid purification or separation – Processes – Separating
Reexamination Certificate
2000-07-03
2001-06-19
Popovics, Robert (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S386000, C210S400000, C100S118000, C100S153000, C198S626300, C198S626500
Reexamination Certificate
active
06248245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of solid/liquid separation systems and, more particularly, to a belt press having an elliptically shaped inlet guide or grid which allows the pressure on a solid/liquid mixture in the belt press to be controlled.
2. Technical Considerations
Various systems are known in the art for dewatering solid/liquid mixtures, suspensions or slurries, such as sewage sludge or other flocculated or unflocculated slurries. Such mixtures, suspensions or slurries will be referred to hereinafter simply as “mixtures”. In cases where the solids are formed primarily of compressible, granular, fibrous or cellular components, belt presses are typically used to separate the solid components from the liquid components. Belt presses dewater the solid/liquid mixture by applying an increasing surface pressure to the mixture as the mixture is carried between two moving belts and through a series of press rollers.
One example of a prior art belt press is schematically shown and generally designated
10
in
FIG. 1
of the drawings. The belt press
10
has a frame
12
with an upper belt
14
and a lower belt
16
. The belts
14
and
16
are typically liquid permeable. The upper belt
14
is rotatably mounted around a plurality of guide rollers
18
. The lower belt
16
is independently, rotatably mounted around a plurality of guide rollers
18
′. The upper and lower belts
14
and
16
are looped around a series of press rollers
20
.
To dewater a solid/liquid mixture, the mixture is continuously fed into a feed box
22
located above the upper surface of the lower belt
16
. The feed box
22
distributes the mixture uniformly over the top of the lower belt
16
. The belts
14
and
16
are rotated in conventional manner, such as by electric motors turning the guide rollers
18
,
18
′. As the lower belt
16
moves toward the left, as shown in
FIG. 1
, the bottom of the lower belt
16
rides across a stationary inlet grid
24
fixedly mounted on the frame
12
. The inlet grid
24
has a flat or planar entrance portion
25
near the feed box
22
and a short, curved exit portion
26
at the other end. The exit portion
26
has a constant radius.
As the belts
14
and
16
rotate to the left, as shown in
FIG. 1
, the mixture enters a “wedge zone”
27
between the upper and lower belts
14
and
16
where pressure is applied to the mixture by the belts. As the mixture is pressed in the wedge zone
27
between the two belts
14
and
16
, liquid is pressed out of the mixture to start forming a sludge or filter cake between the upper and lower belts
14
and
16
. A pressing mechanism
28
, such as a plate or a series of rollers, is generally located above the lower portion of the upper belt
14
to press the upper belt
14
toward the lower belt
16
to increase the pressure on the mixture between the belts
14
and
16
. The exit portion
26
of the inlet grid curves downwardly to guide the upper and lower belts
14
and
16
, along with the filter cake trapped therebetween, around a perforated roller
29
where more liquid is pressed out of the filter cake. The belts
14
and
16
, along with the filter cake therebetween, move through the series of press rollers
20
. The press rollers
20
are arranged in decreasing diameters in a direction of movement of the belts
14
and
16
. The press rollers
20
provide an increasing compressive and shearing force on the filter cake to further dewater the filter cake. At the end of the series of press rollers
20
, the belts
14
and
16
separate and the dewatered filter cake is released and collected.
While generally adequate for dewatering sludge, such conventional belt presses
10
have several shortcomings. One problem with the known belt presses
10
is that if the pressure on the solid/liquid mixture between the belts
14
and
16
is increased too quickly, some of the mixture may be ejected sideways from between the belts
14
and
16
. Further, since the exit portion
26
is of constant curvature, it provides an increased pressure of about the same magnitude over its entire area. It is, therefore, difficult to gradually increase the pressure on the mixture as it moves through the wedge zone
27
. Additionally, the mechanical pressing mechanism
28
must be serviced and maintained to keep it in proper working order. Another problem with such known belt presses is that it is difficult to change the pressure profile on the filter cake to compensate for various viscosities or thicknesses of different materials to be filtered. While some belt presses provide for some adjustment in the wedge zone, this is generally accomplished by changing the convergence angle of the two belts. However, this adjustment typically also changes the pressure rise profile. That is, increasing the angle between the belts causes a more rapid pressure rise which must be accounted for by reducing the belt tension and, hence, the overall performance of the press.
Another known dewatering device is disclosed in U.S. Pat. No. 4,879,034 to Bastgen. This device consists of a frame carrying a supporting plate which is flexible so that the curvature of the supporting plate can be changed. The supporting plate can be formed of a number of separate plate parts which are joined together to form the flexible supporting plate. A series of movable members are attached along the supporting plate so that as the movable members are individually pivoted on the frame, the curvature profile of the supporting plate changes. However, this complex, multi-component plate construction adds to the cost of making, using, and maintaining the device.
Therefore, it is an object of the invention to provide a belt press of reduced complexity but which reduces the problems associated with known belt presses. It is additionally an object of the invention to provide a belt press having a pivotable inlet guide or grid to control the pressure on a solid/liquid mixture between the belts of the press. It is further an object of the invention to provide a belt press having an inlet guide in which the angle between the belts may be adjusted by moving an entrance end of the guide to control a tangent point of the upper belt on the lower belt without changing the curvature profile of the inlet guide. It is also an object of the device to provide a belt press which does not require a conventional mechanical pressing mechanism.
SUMMARY OF THE INVENTION
A belt press is provided having a frame with a first belt and a second belt rotatably mounted on the frame. A curved inlet guide is movably carried on the frame, the inlet guide having a decreasing radius from an inlet end to an exit end. The inlet guide has a fixed, i.e., non-changeable, curvature profile. A positioning assembly is mounted on the frame and attached to the inlet guide, preferably substantially adjacent the inlet end of the inlet guide, to move the inlet end of the inlet guide up and down with respect to the frame, e.g., by pivoting the exit end of the inlet guide on the frame.
A complete understanding of the invention will be obtained from the following description when taken in connection with the accompanying drawing figures wherein like reference characters identify like parts throughout.
REFERENCES:
patent: 3796148 (1974-03-01), Heissenberger
patent: 3796149 (1974-03-01), Heissenberger
patent: 3894486 (1975-07-01), Sparowitz et al.
patent: 3906853 (1975-09-01), Wohlfarter
patent: 3942433 (1976-03-01), Wohlfarter
patent: 3945789 (1976-03-01), Boman
patent: 3998149 (1976-12-01), Malarkey, Jr.
patent: 4147101 (1979-04-01), Heissenber et al.
patent: 4584936 (1986-04-01), Crandall et al.
patent: 4879034 (1989-11-01), Bastgen
patent: 5240609 (1993-08-01), Langley
patent: 5545333 (1996-08-01), Louden et al.
patent: 5592874 (1997-01-01), Blauhut
Flottweg Veronesi Separation Technology brochure “Solid-Liquid Separation and System Engineering”, Oct. 10, 1994, 4 pages.
Ashbrook Corporation
Popovics Robert
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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