Note: Descriptions are shown in the official language in which they were submitted.
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1 The invention concerns a process for the continuous
thickening of suspensions in a filter concentrator with plug-
shaped filter elements.
From United States Patent 2,035,592 it is known to
provide a filter concentrator with filter elementshanging in a
pressure container. The totality of the filter elements ls
cleaned off in determined intervals by compressed air in counter-
stream, after interrupting the filtration. With this known con-
densor a continuous thickening or filtration is not possible.
For cleaning off the filter elements, the filtration must be
completely interrupted.
It is therefore an object of the present invention to
provide a continuous process for the thickening of suspension
during which the filtration does not have to be completely
interrupted.
This object is obtained according to the present in-
vention using a filter concentrator with plug-shaped filter
elements, which are removably fixed on individual collecting
pipes in a cylindrical container, with the process character-
ized as follows: without interrupting filtration, an individual
collecting pipe is disconnected and the filter elements of this
collecting pipe are freed of solids through pressure surge by way
of a flushing back agent, opposite to the direction of filtra-
tion.
As a rule, compressed air serves as flushing back
agent; however, one can also if necessary use inert gas such as
nitrogen or carbon dioxide. In addition, liquids such as water
or solvent can serve as flushing back agent. The flushing back
follows automatically, whereby the valves are operated pneuma-
tically or magnetically. It is expedient to use quickly operat-
ing valves. The flowing-off of the filtrate from the particular
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1 collecting tube being cleaned must be quickly interrupted,
whereby solely through the ensuing reversed push provided by
the flushing back a large portion of the solids is removed
from the filter elements and sinks to the bottom of the con~
tainer. The muddy material is periodically transferred from
the container across the bottom va:Lve. With use of gas or
air as flushing back agent, a ventilation valve located at
the highest part of the container lid provides for an out-
gassing.
The novel features which are considered character-
istic for the invention are set forth in particular in the
appended claims. The invention itself, however, both as to
its construction and its method of operation, together with
additional objects and advantages thereof, will be best under-
stood from the following description of specific embodiments
when read in connection with the accompanying drawing.
FIG. 1 shows a longitudinal section through the
filter concentrator according to the present invention;
FIG. 2 is a horizontal cross section along line A-A
of FIG. l; and
FIG. 3 is a front elevation view of the unit lying
outside of the container.
The filter tank 1 is provided with an inlet pipe con-
nection 2 for the slime or slurry to be filtered, an outlet pipe
connection 3 for the filtrate, as well as a ventilation connect-
ion 4 in the cover 5 and a discharge connection 6 in the apex of
the conical part of the tank. Behind the inlet pipe connection
2 is fixed a bafile plate 7. The outlet pipe connection 3 is
extended through a schematically represented tube part 8 and a
branch pipe 9. The tube 8 is closable through a valve 10, and
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1 the tube 9 through a valve ll. From connection 4 a conduit
12 leads to ventilation valve 13. The ventilation valve
13 is controlled by a level regulator 29, so that upon open-
ing of valve 13 only gas and no liquid can escape. The dis-
charge connection 6 is closed through a valve 14. In the in-
terior of the container 1 is fixed a collecting pipe 15 on a
flange 16. The collecting pipe 15 rests on the opposite side
upon a semicircular edge 17. The tank is fixed with its flange
18 on flange l9 of an intermediate ring 20.
The cover 5 is fixed with its flange 22 at the top flange 21
of the intermediate ring 20. The filter elements 23 are mounted
hanging in series on collecting tube 15 upon tube parts 24 and
fastenings 25.
In FIG. 2 the collecting tubes 15 are represented
disposed parallel in the filter tank. Each collecting tube is
connected across a connection 3 with the valves 10, 10', 10",
10"', 10'V, respectively. The conduits 26 lead to a collecting
conduit 27. On account of the view, only the valves are re
peatedly designated. The air conduit 28 is mounted above or
below the conduit 8. The tubes 9 lead across valves 11, 11',
ll", ll"', ll'V, respectively, to the tube parts 8.
In operation, liquid to be thickened in the filter
tank 1 is led across connection 2 by means of a not represented
pump. The baffle plate 7 prevents too strong a turbulence,
which could harm filter cakes deposited upon filter elements 23.
The liquid passes through from outside the filter agent of filter
elements 23. Metallic or textile webs come into question as
filter agents. The solids are deposited onto the webs of filter
elements 23, and form, according to their type, more or less
thick filter cakes. The filtrate flows across tube part 24 into
1 the collecting tube 15, the tube part 8 and -the open valve 10,
as well as the tube section ~6, into the filtrate collecting
tube 27.
After a period to be determined empirically, the valve
10 of one of the collecting tubes 15 is quickly closed, but the
filtration continues with all of the other collecting tubes.
After valve 10 has been closed, the quickly opening ~alve 11 is
operated, whereby air or some other flushing back agent brings
about a pressure surge across tube 8, which continues across the
liquid to such an extent that the filter cakes are cast ofE
: from elements 23. The filter cakes fall by gravity into the
apex of the conical part of the filter tank and are collected
there, from where, from time to time, they can be discharged
across valve 14 and connection 6. After throwing off the filter
cakes, which demands only a few seconds, the flushing back
valve 11 is again closed, the valve 10 opened, and the thicken-
ing continues with the uninterrupted series of filter.
In this manner, the collecting tubes 15 with filter
elements 23 fixed thereupon can be successively shut off, the
filter elements cleaned, and then the respective collecting
tube put back into opera-tion.
It is evident that in such a manner a practically
continuous thickening can be undertaken which is performed
completely automatically. The automatic operation is restric-
ted to quickly operating, periodically regulated valves.
Filtration tests with waste water from a biological
two-stage plant produce, with a laboratory filter plug with:one
element of the type with 170 cm total filter surface, an ini-
tial.performance of 6000 liters per m per hour~ After a drop
3~ in the efficiency of the filter unit during a -filtration period
of 5 minutes, to about 2000 liters per m2~h, the cleaning
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1 operation, i.e. flushing back, is performed, which requires
30 seconds, following which the total efficiency of the filter
elements is again reached.
It will be understood that each of the elements
described above, or two or more together, may also find a use-
ful application in other types of filtrations differing from
the types described above.
While the lnven-tion has been illustrated and described
as embodied in a process for the continuous thickening of suspen-
sions, it is not intended to be limited to the details shown,since various modifications and structural changes may be made
without departing in any way from the spirit of the present in~
vention.
Without further analysis, the foregoing will so fully
reveal the gist of the present invention that others can, by
applying current knowledge, readily adapt it for various appli-
cations without omitting features that, from the standpoint of
prior art, fairly constitute essential characteristics of the
generic or specific aspects of this invention.
