Note: Descriptions are shown in the official language in which they were submitted.
I
CONTI~UOUS-OP~RATION FILTRATION TECHNIQUE END EQUIPMENT
This invention is designed as a continuous operation filtration
technique that employs a moving endless fitter cloth or similar
onto which the sludge is fed at a certain feeding point and from
which the solid cake is removed at a later point, in regard to
the direction of rotation of the cloth.
In order to obtain high efficiency, it is of vital importance
that the properties of the filter cloth, screen or other medium
remain as constant as possible throughout the process. One gent
oral disadvantage of known filtration techniques in continuous
operation is the rapid blocking of the filter cloth which is
caused by particles embedding in the cloth. For this reason, the
filter cloth must be continuously washed during the process,
which can be done most effectively by means of the so called
reversed flow method.
The purpose of this invention is to provide a continuous-oper-
anion filtration technique in which the filter cloth or other
filter medium is cleaned by employing the reversed flow method
in a simpler and more effective way than before. It is kirk-
touristic of the invention that sludge is fed onto the cloth at
two points on different sides of the cloth; consequently, the
particles that the removal unit fails to remove are washed away
by the liquid passing through the cloth. In other words, this
invention makes it possible to clean the cloth automatically in
the course of the process wherefore no special cleaning open-
anions are required.
As such, the idea of using both sides of the filter cloth is a
known method The filtration process referred to does not, how-
ever, involve continuous operation, nor is the associated equip-
mint so designed as to provide sufficient cleaning by means of
the process itself. Therefore, the equipment is fitted with
separate cleaning devices which spray cleaning agent on both
sides of the cloth between filtration phases. This new invention
does not require such cleaning devices, although they can be used
in addition to the reversed flow.
Characteristic of one of the applications of this invention is
that the sludge to be filtered is compressed by an upper belt
which moves in the same direction as the cloth, along the length
of the cloth from where the sludge is introduced to where the
cake is removed. Pressure accelerates the separation of liquid
from solid particles in the sludge, effecting a powerful flow of
liquid through the cloth, which, in turn, removes the remaining
solid material from the other side of the cloth.
Characteristic of another application of this invention is that
pressure is applied to the sludge between the feeding and removal
points by means of rollers which force the filter cloth into a
bag-shaped form. In this way, sludge is prevented from escaping
..,',~.
owe
do
sideways, which is particularly important if the internal fake-
lion of solid particles is low.
The invention involves also equipment designed to utilize the
continuous-operation filtration technique described above This
equipment comprises a moving endless filter cloth, devices for
feeding the sludge on-to the cloth at a certain point as well as
devices for removal of the solid cake from the cloth at a certain
point which is located further on in the direction of rotation of
the cloth; it is characteristic of the equipment that it has two
separate feeding points and two separate removal points, so
positioned that sludge is fed on different sides of the cloth at
the two points, thus allowing the liquid passing through the
cloth to remove the solid matter that the removal unit failed to
remove.
The equipment designed on the basis of this invention can come
prose a compressing belt which moves in the same direction as the
cloth between the feeding unit and the removal unit, or the
equipment can be fitted with rollers, placed between the feeding
and removal units which apply pressure on the sludge by forcing
the cloth into a bag-shaped form.
The invention is presented in detail by means of the following
examples in which reference is made to the enclosed drawings
where
Figure 1 shows one type of filtration equipment based on the
invention; sludge is compressed by means of a belt `
Figure 2 shows II-II cross section of figure 1
Figure 3 depicts another filtration equipment based on -the
invention; the filter cloth is forced into a bag-shaped
form when pressure is applied on the sludge
Figure 4 shows IV-IV cross section of figure 3
figure 5 shows V-V cross section of figure 3
Figure 6 shows VI-VI cross section of figure 3 and
Figure 7 shows the equipment depicted in figure 3 from above
Figures 1 and 2 show the filtration equipment in which ultra
lion is effected by means of the continuous-operation filtration
cloth the equipment comprises two feeding units (2) which
feed the sludge (3) through pipes (4) onto the cloth (1). Both
feeding units (2) are succeeded by removal units (5) which remove
the solid cake (6) prom the cloth (1) by means of a scraper.
Between the feeding and removal units, the sludge is compressed
by the pressing belt (8) , or by rollers (9), which move in the
same direction as the cloth (1), ; additional support is provided
by the support belt (10) moving under the cloth. When the sludge
is coy pressed, the liquid passes through the filter cloth (1)
and support belt (10), as indicated by the arrows (11) in figure
1.
The essential point in the filtration process described in
figures 1 and 2 is that the sludge (3) is fed by the feeding
units (2) onto different sides of the cloth I In this process,
the liquid, separated from the sludge (3) and passing through the
cloth (1), removes the solid matter embedded in the cloth in the
preceding phase of filtration. Thus the process provides reversed
flow cleaning of the cloth, and no separate cleaning unit is
required.
The filtration process described in figures 3 - 7 differs from
the one presented in figures 1 and 2 in that the filter cloth
(1), and the net-like belt supporting it, are forced into a bag-
shaped form between the feeding and removal units. This is
achieved by means of rollers (12) which simultaneously effect the
separation of liquid from solid matter as indicated by arrows
(11) in figures 3 - 6. reversed flow cleaning of the cloth takes
place as described above; this process is especially suitable for
sludges with low internal friction which can in this way be
retained on the cloth during the compressing phase.
I-t is obvious to a professional that the applications of the
invention are not confined to the examples presented above; they
may vary within the framework of the enclosed patent claims.
