Liquid purification or separation – Filter
Reexamination Certificate
1998-12-10
2001-04-03
Walker, W. L. (Department: 1723)
Liquid purification or separation
Filter
C210S321630, C210S321640, C210S321720, C210S321800, C210S321890, C210S346000, C210S450000
Reexamination Certificate
active
06209727
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device based on cross flow membrane filtration for separation of separable constituents from a liquid medium. Additionally the invention relates to a filter cassette and an abutment ring intended to be used in said separation device.
In a cross flow filter a liquid is supplied to a chamber comprising at least one dynamic membrane. The liquid being supplied is divided into a permeate flow penetrating the dynamic membrane and a reject flow flowing along the filter without penetrating it.
BACKGROUND OF THE INVENTION
Cross flow filtration apparatuses are described in the patent literature, for example, in the Swedish Publication Prints SE 451429, 457607, 459475, 463241 and 465040. Methods based on the use of such apparatuses are successfully applied for separating solid constituents from a liquid phase and for separation of liquid from liquid, for example, for separation of oil from water. The above mentioned Publication Print SE 463241 describes such a fluid/fluid separation method.
SE 459475 describes a separation device comprising several adjacently arranged cells.
FIG. 1
shows a section of such a stack. Each unit or cell consists of a plate
10
provided with a central opening through which extends a shaft
11
provided with rotor blades
12
. On each side of the plate
10
a filter
15
is fastened by means of clamp rings
13
and
14
. The liquid to be treated is supplied through a common channel
16
formed by through-holes in the plates
10
. The liquid stream is supplied into the chamber
17
, whereby part of it (the permeate) passes through the filter and is gathered via channels
18
in the plate to be finally discharged through a common outlet (not shown). The portion of the liquid flow (the reject) which does not penetrate through the filter, is discharged through holes in the plate. Said holes form a common conduit
19
for the outgoing reject. The liquid is pushed across the filter surface
15
by means of the rotor blades
12
.
When the filter is changed in the above mentioned device the plate containing the filter to be changed is taken out. The removing of the plate itself from the stack is carried out relatively easy in a way more closely described in the Publication Print in question. However, the removal of the used filter from the plate and inserting of a new filter is very time consuming and hard because the filter is fastened by means of numerous screws to the clamp rings securing the filter to the plate. This causes for its part long shutdowns in the separation plant.
SUMMARY OF THE INVENTION
According to the present invention a separation device is achieved in which it is possible to change the filters in a very easy and fast way. The invention is based on the idea of instead of fastening the filter directly onto the plate it is fastened on a frame constituting a separate unit or a so called filter cassette. Alternatively, the filter can be a rigid, self-supporting filter of a porous material, for example, a ceramic filter or the like. In this case a separate frame is not required in order to support the filter, instead the filter itself comprises the cassette. The cassette can easily be fitted in an abutment ring intended for the purpose. Thus the abutment ring and the cassette replace the above described plate provided with filters. The filter cassettes can be produced in advance and kept in stock to be at hand when the filter needs to be changed.
An essential advantage of the present invention is that the abutment rings together with the end plates, between which the abutment rings are pressed together, form the outer cover of the apparatus. Said construction is very advantageous with respect to mounting, especially when it comes to high filtration units. If the filtration unit would be positioned inside a separate cover the mounting of the cover would require a free space above the filtration unit corresponding at least to the height of the cover. Alternatively it could be possible to divide the cover vertically in separate portions, but such a solution would not be appropriate in practice. The abutment ring according to the present invention forms a portion of the outer cover of the apparatus corresponding to the thickness of the ring. The fitting and removal of said abutment rings requires minimal working space. Another essential feature of the abutment rings is that they form channels for the liquid streams in the separation device. Adjacent abutment rings form a common channel for the ingoing liquid flow, another common channel for the outgoing reject flow and a third common channel for the outgoing permeate. In addition each separate abutment ring contains channels for distributing incoming liquid over the filter and for gathering the reject flow which has not passed through the filter. Additionally each abutment ring comprises a channel for gathering permeate from the filter. A third essential feature of the abutment rings is that they form the frame for the separate cassettes, whereby the thickness of the abutment rings determines the mutual distance between the separate cassettes.
The invention will be described in greater detail with reference to the enclosed drawings, in which
REFERENCES:
patent: 3203549 (1965-08-01), Schaedler
patent: 4221663 (1980-09-01), Little
patent: 4650584 (1987-03-01), Macierewicz
patent: 5679249 (1997-10-01), Fendya et al.
patent: 943014 (1994-06-01), None
patent: WO 93/12859 (1993-07-01), None
Henttonen Vesa
Karlsson Claes
Leimu Pasi
Paatero Jaakko
Suikki Mikko
Burns Doane Swecker & Mathis L.L.P.
Ocampo Marianne
Valmet-Raisio OY
Walker W. L.
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