Note: Descriptions are shown in the official language in which they were submitted.
APPARATUS FOR THE TREATMENT OF LIQUIDS AND METHOD FOR CLEANING A
LAYER OF FIBRES IN SUCH AN APPARATUS
The invention relates to an apparatus for the treatment of
liquids by means of a layer of fibres, in particular for coales-
cing liquid particles, dispersed in a continuous liquid phase,
by means of a layer of fibres. The invention also relates to a
method for cleaning a layer of fibres in such an apparatus.
In the industry use is frequently made of an apparatus for
coalescing liquid droplets by means of a layer of fibres and
also of an apparatus for the filtration of sdid particles from
a liquid by means of a layer of fibres.
Inter alia from Applicant's British patent specification
No. 1,082,810, published 13th September, 1967, coalescers are
known which comprise a liquid supply, a layer of fibres held under
pressure by walls provided with openings and a liquid discharge,
wherein the liquid to be treated can be passed through the layer
of fibres.
A disadvantage of the known layers of fibres is that during
- the treatment of the liquid the openings between -the fibres
gradually become smaller, because solid contaminants present in
the liquid remain in the openings between the fibres.
This implies that the layers of fibres gradually become
clogged in the course of time and the effectiveness of the layers
of fibres decreases, as a result of which the layers of fibres
must frequently be replaced, which involves loss of time and
extra cost.
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The object of the invention is to provide an apparatus and a
method which enables the layers of fibres to be cleaned in a simple manner,
so that replacement of the layers of fibres is no longer necessary.
According to the invention, there is provided an apparatus for
treating liquids including a housing having an interior divided into three
spaces by a pair of perforated walls, the space between the walls containing
fibres secured to at least one of the walls, the walls being arranged to be
displaceable relative to each other from a position wherein the fibres are
held under pressure between the walls to a position wherein the fibres can
stretch themselves, and conduits communicating with the spaces located at
opposite sides of the pair of walls.
According to another aspect of the invention, there is provided
a method of treating a liquid by means of the apparatus stated in the preceding
paragraph including the steps of passing a contaminant-containing liquid via
the conduits through the perforated walls and the fibres arranged therebetween -~ -
under pressure, displacing the walls away from each other and causing a
second liquid to flow via the perforated walls and along the fibres such that -
contaminants present on or between the fibres are entrained by the second liquid,
and returning the walls to their original position and continuing the passage
of the contaminant-containing liquid.
The invention will now be illustrated further with reference to
an embodiment shown in the drawings, in which:
Figure 1 shows a longitudinal cross-section of a coalescer
according to the invention;
Figure 2 shows on an enlarged scale detail II of Figure l;
Figure 3 shows on an enlarged scale detail II of Figure 1 during
the cleaning of the fibres.
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The coalescer according to Figure 1 comprises a housing 1 provided
with a layer of fibres 2, which layer is held under pressure by means of walls
3 and 4, each provided with openings, for example walls consisting of per-
forated plates, of sieve plates or of a fabric made of metal threads or
plastic threads. The layer of fibres 2 consists of, for example, polypropylene
fibres, an end of each fibre being secured to the wall 3. To this end the
fibres may be secured directly to the wall 3, while it is also possible to
secure the ends first to a suitable network (not shown), which network is
secured to the wall 3. The apparatus further comprises a liquid supply 5 with :
a valve 6 and two liquid discharges 7 and 8 with valves 9 and 10
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respectively. The layer of fibres 2 is secured in a leak-proof
manner to the wall of the housing 1.
The liquid supply 5 is connected, for example, to a tank
(not shown) in which the liquid mixture to be treated can be
stored. The liquid discharge 7 is connected to a separator (not
shown). The liquid discharge 8 is connected, for example, to a
tank (not shown), in which the liquid with the contaminants from
the layer of fibres can be stored.
The operation of the coalescer is as follows:
Through the liquid supply 5 a liquid mixture, consisting
of a continuous liquid phase in which liquid droplets are dis-
persed, is passed through the wall 3 and subsequently through
the layer of fibres 2.
As the liquid mixture flows through the layer of fibres 2,
the liquid droplets coalesce to form larger drops which can be
readily separated from the continuous liquid phase in a separator
(not shown), known per se.
The speed at which the liquid mixture must be passed through
the layer of fibres 2 is dependent on the nature of the liquid
mixture to be treated. As is known, it is desirable to apply a
fibre diameter dependent on the average diameter of the liquid
droplets flowing into the layer of fibres.
The thickness of the layer of fibres 2 may vary widely.
The liquid mixture is preferably passed through the layer
of fibres 2 in a vertical direction, for which purpose the
housing 1 is positioned in such a way that the longitudinal axis
of the housing is vertical. If the specific gravity of the liquid
droplets to be coalesced is lower than that of the continuous
liguid phase, the liquid mixture is passed upwardly through the
layer of fibres 2, as shown in Figure 1. The liquid mixture is
passed downwardly through the layer of fibres 2 if the specific
gravity of the liquid droplets to be coalesced is higher than
that of the continuous liquid phase.
After the liquid mixture has left the layer of fibres 2
; 35 and has passed through the wall ~, the liquid mixture is passed
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to said separator through the liquid discharge 7, in which the
larger liquid droplets formed by coalescence are separated from
the continuous liquid phase.
After liquid has been passed through the layer of fibres 2
for some time, the pressure drop across the layer of fibres 2
increases and the effectiveness of the layer decreases, because
mainly solid contaminants present in the liquid mixture reduce
the free spaces between the fibres, with the result that the
coalescing effect of the layer of fibres 2 decreases. When the
coalescing effect of the layer of fibres 2 has fallen to a
certain value the layer of fibres 2 must be cleaned in order
to restore the effectiveness of the apparatus. Before proceeding
to clean the layer of fibres 2 the liquid discharge 7 is closed
by means of valve 9 and the liquid discharge 8 is opened by means
of valve 10.
The method for cleaning the layer of fibres 2 is as follows:
The wall 4 is displaced upwardly owing to which the distance
between the walls 3 and 4 become greater. The wall 4 is prefer-
ably displaced over a distance at least equal to the length of
the longest fibre in the layer of fibres 2, see Figure 3.
Subsequently, a liquid is passed along the fibres 14 via the
wall 3. The velocity of the liquid stream is now chosen in such
a way that the fibres 14 stretch themselves, see Figure 3. Solid
contaminants present on or between the fibres 14 are then
readily entrained by the liquid stream and removed through
the liquid discharge 8.
The cleaning liquid used can be the same liquid mixture as
is treated by the coalescer during normal operation. If this
liquid mixture is used as cleaning liquid, this mixture may, after
cleaning the fibres 14, optionally be returned through the liquid
; discharge 8 to the storage tank (not shown) for the liquid mixture
to be coalesced.
If the cleaning liquid used is another liquid than the
liquid mixture to be coalesced, which is frequently preferred,
the apparatus must be provlded with a separate liquid supply 11
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with a valve 12. During the normal operation of the coalescer
the supply 11 is closed. When the fibres 14 must be cleaned, the
liquid supply 5 is closed by means of valve 6 and the liquid
supply 11 is opened, enabling the cleaning liquid to be supplied.
The apparatus shown in Figure 1 is provided with one layer
of fibres 2. It is also possible to provide the apparatus with
several layers of fibres arranged in series. In that case each
layer of fibres is clamped between two appertaining walls
provided with openings. When in such a case the layers of fibres
must be cleaned, the distance between each pair of walls is
enlarged, preferably to at least the length of the longest fibre
in the relevant layer of fibres.
The hereinbefore described method for cleaning a layer of
fibres can also be used in a filtration apparatus for separating
solid particles of a certain size from a liquid by means of the
layer of fibres. The particles which are retained will gradually
clog the layer of fibres, as a result of which the good filtra-
tion effect of the layer of fibres decreases
Moreover, the invention is not limited to the use of flat
walls provided with openings. It is, for example, also possible
to use non-flat walls between which the layer of fibres is
- clamped, for example, corrugated or cylindrical walls. Further,
the said walls may also consist of a network or fabric of
threads.
Although in the embodiment described the walls between which
- the fibres are clamped are continuously held parallel to each
other, both during normal operation and during cleaning of the
fibres, this is not strictly necessary.
For the purpose of cleaning, the walls must be displaceably
arranged in the housing in such a manner that the fibres of the
layer of fibres can stretch themselves. To this end one of the
two walls can, for example, be so hingeably arranged that it
can be turned away before cleaning.
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Instead of threads or fibres of polypropylene, the layer of
fibres can also be made of threads or fibres of another suitable
material, for example glass.
In the embodiment shown, one end of each fibre 14 is
secured to the wall 3. Instead, it is possible to secure both
ends of each fibre to the wall 3. Another possibility is to
secure one end Or each fibre 14 to the wall 3 and the other
end of each fibre 14 to the wall 40
In the last mentioned case the walls 3 and 4 should not
be displaceable away from each other over a distance larger than
the length of the shortest fibre.
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