Liquid purification or separation – Sectional chamber press type – With residue removal or liquid agitation
Reexamination Certificate
2001-05-09
2003-11-04
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Sectional chamber press type
With residue removal or liquid agitation
C100S197000, C100S211000, C210S227000, C210S230000, C210S231000
Reexamination Certificate
active
06641726
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a device for the continuous filtration of fluids by means of the pressure differential between the inlet and outlet, as well as the removal of residual amounts of the slurry by means of a pneumatic pressure medium before opening the device, said device having
a plurality of filter plates having a slot on both sides for seating a planar filter medium and equipped with drainage channels for the filtrate;
a plurality of membrane plates having connections, bores and recesses for the admission of the pressure medium, which membrane plates are covered on both sides with an elastic membrane such that a slurry chamber or a filter cake chamber is formed between the filter medium and the membrane;
corresponding recesses in the filter plates and membrane plates which when installed form at least one admission channel for the slurry and one drainage channel for the filtrate, and also having
end plates, retaining fixtures and clamping fixtures to connect the filter plates, membrane plates and frames to form a filter pack that can later be disassembled.
The invention also relates to a filtration and cleaning method. From the aspect of its structural design, such a device belongs to the group of devices known as filter presses. However, it is used for filtration like a plate filter, in which the filtrate is forced through the filter medium by means of the pressure differential of the fluid between the inlet and the outlet.
BACKGROUND OF THE INVENTION
A prior art example of a plate filter is disclosed in DE 39 06 816 C3. There are a plurality of filter plates arranged in parallel consolidated into a filter pack. When assembled, filter beds is pressed together between mating surfaces of the filter plates, which provide a seal between the slurry chambers and the filtrate chambers, and seal the entire filter pack to the outside.
A prior art example of a filter press is disclosed in DE 39 32 422 A1. The membrane plates alternately disposed between the usual filter plates comprise a circular frame with connections for the admission and drainage of a pressure medium, and a central wall, with a membrane attached to each side of a frame symmetrical to the central wall via a clamping ring. The axial length of the filter press is due to the cumulative width of the filter plates and the frame elements of the membrane plates. The space between the central wall of the membrane plate and the filter media attached to both sides of the filter plates is divided by the membranes into roughly equal sized suspension and pressure medium chambers. The frame elements have bead-like elevations extending along the axis of the filter device, over which elevations the membranes are stretched to improve their durability/stability when subjected to cyclic loads of up to 120 bar in these particularly critical areas. Because the membrane is stretched and arranged in this manner, the membrane is not extended but compressed when impinged by the pressure medium during the press process. As a result, the membrane never makes complete contact with the membrane plate when unpressurized, nor can the membrane make complete contact and lie flat against the filter plate when pressurized. Given the purpose of the generic device, the prior art filter press has an unnecessarily long axial length due to the pressure media chambers between the membranes and the central walls of the membrane plates. In other words, the space between the filter plate and the membrane plate that can be used as a slurry chamber is quasi halved because of the central position of the membranes, which under otherwise identical conditions also results in an oversized filter press.
The prior art also discloses filter devices in which pressurized membranes work in conjunction with filter cloths that must completely or partially match the change in shape of the membranes during filtration. In these cases, the membranes are equipped on the side facing the filter cloth with spacing cams so that the filtrate passing through the filter cloth can drain between the filter cloth and the membrane. Such membranes are unsuited for the intended application of the device according to the current invention.
SUMMARY OF THE INVENTION
The object of the current invention is therefore to refine a prior art device as described above for the filtration of fluids such that the residual losses can be significantly reduced compared to conventional plate filters without having to accept the disadvantages of prior art filter presses.
To achieve this object, the current invention teaches that the filter medium comprises sections of a sheet filter material mounted in the recesses of the filter plates; that the membranes, which when pressurized expand elastically to completely contact the filter plates or sheet filter material, have a smooth surface on both sides and make complete contact with the membrane plates when depressurized.
Sections of a proven and inexpensive sheet filter material can be used as the filter medium because the normal filtration process is the same as with conventional plate filters. Sheet filter material has a labyrinth-like depth filtration structure, which when used in conjunction with different surface charges permits both mechanical and adsorptive separation of particles along the relatively long path through the filtration medium. These materials, also known as filter beds, are special paperboards for the filtration of fluid media with the goal of removing coarse to super-fine particles, colloids, microorganisms and other undesirable components, and thus maintain the desired quality of the filtrate or to extract solid residues. These are manufactured using special paper machines, primarily Fourdrinier paper machines.
The raw materials are usually selected, bleached celluloses from conifer or deciduous woods of high purity, i.e. with high alpha content, selected diatomaceous earths and perlites, as well as manmade fibers such as polyolefin fibers, activated carbon, polyvinylpyrrolidone (PVP) or similar materials for special applications.
Most filter beds can be backed on the downstream side to prevent the loss of fibers during filtration without adversely affecting flowthrough. Certain approved resins can be used in small amounts to achieve specific effects (interfacial potentials, zeta potential).
The selection of raw materials, the processing thereof and the blending ratios together with other manufacturing parameters determine effectiveness and application.
The alternately disposed membrane plates are only activated when forcing residual amounts of the product from the slurry chamber prior to opening the device, and the remaining filtrate is forced by means of the pressurized membranes through the filter cake and the filter medium.
Because the slurry chamber is completely lined by the membrane when pressurized, it is possible to reduce the residual losses to nearly zero because the slurry chamber can be almost completely emptied by means of the membranes, and because the filter cakes are also mechanically pressed. The filter cake is solidified and nearly completely free of residual filtrate. The filter cake is almost completely dry and can be easily removed together with the filter medium after opening the filter device. The filter cake is thus prepared for further processing as is required in some filtration applications, such as the separation of blood plasma, for example.
A membrane that is smooth on both sides prevents filter cake constituents from sticking to the membrane, and also ensures that the drainage channels in the filter plates can be optimally covered when impinged with a fast-flowing detergent for cleaning.
The drainage channels on the filter plate are preferably vertical and horizontal grooves in the filter plate in the area of the groove for the sections of the sheet filter material.
The drainage channels on the filter plate are preferably vertical and horizontal grooves formed in the area of the slot in the filter plates for the sections of sheet filter material.
The horizontal and/or vertical
Drodge Joseph
H. Strassburger GmbH & Co. KG
Hudak, Shunk & Farine Co. LPA
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