Note: Descriptions are shown in the official language in which they were submitted.
8~L
SEPARATING TWO IMMISCIBLE LI~UID PHASES OF ~IFFERENT
_
DENSITIES
The present invention relates to the separation of two
immiscible liquid phases of different densities which are mixed
with one another and in continuous flow.
The invention has particular application to the separation
of hydrocarbons contained in water to be discharged, for
example industrial water to be discharged or ballast water,
complying with the specifications contained in Resolution A 393
passed by the IMCO (Inter-Governmental Maritime Consulative
Organization) on the 14th ~ovember 1~7~ and which provides that
the content of hydrocarbons in effluents discharged from places
where machinery is accmmodated and from tanks must not be
higher than 100 ppm.
According to the invention there is provided apparatus for
separating two immiscible liquid phases of different densities,
comprising a decanting chamber provided with an inlet for
introducing a liquid to be treated and opening out between
walls which are oriented obliquely with respect to the
2~ direction of introduction, the said walls constituting two
deflectors located one below the other, and the inlet being
opposite the lower deflection.
Preferably, the deflectors respectively adjoin two
opposite walls of the chamber and cooperate with them to form a
baffle. According to another preferred feature of the
26 invention, the top of the lower deflector is located
substantially at the same level as the bottom of the upper
34~3~
deflector.
A separator which has a decanting chamber provided with an
inlet for introducing the liquid to be treated and which opens
out between walls which are oriented obliquely with respect to
the direction of introduction has been described in U.S. Patent
1,920,468.
The invention will be described in more detail, by way of
example, with reference to the drawings in which:-
Figure 1 is a basic schematic diagram of a separator
embodying the invention;
Figure 2 is a vertical section of an actual separator
embodying the invention;
~igure 3 is a horizontal section through tlle separator of
Figure 2 in the plane III-III of Figure 2, and
~igure 4 is a perspective view of the separator of Figure
2 which is restricted to certain elemen~s.
The separator shown diagrammatically in Figure 1 comprises
an enclosure 1 within which there are an inlet chamber 2, a
transfer chamber 3.~ and an outlet chamber 4.
The inlet chamber 2 is provided . with two deflectors S and
6 which form between them a space 7 into which opens an inlet 8
through which the liquid to be treated is introduced into the
separator.
The deflectors 5 and 6 are inclined walls which are
inverted with respect to the direction of introduction o~ the
26 liquid and which form with this direction of introduction
(assumed to be horizontal) identical or different opposite
accute angles a and b, preferably between 45 and 20,
4~3~
better still between 3S and 25 and optimally in the vicinity
of 300.
~ referably, the bottom 1~ of the upper deflector 5 is
located subs~antially level with the top 11 of the lower
deflector 6 as shown, and the inlet 8 is disposed just below
the bottom 10.
The liquid to be treated is, for example, ballast water
(the heavy phase) containing a hydrocarbon (the light phase)
which is to be separated so as to reduce the hydrocarbon
content of the water to a tolerable level before discharging
the water into the sea.
The major part of the separation is achieved by
~ecantation (gravity separation) in the inlet chamber 2.
In fact, the deflectors 5 and 6 and the walls 12 and 13 of
the chamber which respectively adjoin them constitute a baffle
having an upper exit sec~ion 14 through which the separated
light phase is evacuated towards the ~op of the inlet chamber
an~ a lower exit section 15 through which the heavy phase,
still containing an emulsion of the light phase, is evacuated
Z downwardly. The light phase which accumulates at the top of
the chamber 2 can be rernoved by any suitable means (indicated
diagrammatically by the arrow 16), while the havy phase (the
path of which is indicated diagrammatically by the arrow 17)
flows into the transfer chamber 3.
The chamber 3, which is located at a level lower than that
26 of the inlet chamber, is provided with means promoting
coalescence of the emulsion of the light phase which is still
contained in the heavy phase, these means, for example, being
~, .
constituted simply by a system of fins 1~, the axes of which
are horizontal, but which are themselves eiher horizontal or
inclines (as seen in a transverse plane). These fins are
slightly spaced one from another, for example with an interval
of less than lOmm, but nevertheless sufficient for a suitable
flow of liquid. By way of indication, an interval of 7 mm is
suitable for a flow of 500 litres per hour.
The fins have the effect of multiplying the area of
contact with the fluid and of reducing the distance of
decantation of the drops of the light phase. These will
naturally rise and apply themselves against the fin located
immediately above. They will coalesce with each other at the
surface of the fin, which, when it is sufficiently saturated,
will release the light phase at the outlet in the form of large
drops, which will decant easily in the outleL stage 4.
The outlet stage or cham~er 4 is provided with an
evacuation outlet 14 for the light phase at the top and with an
evacuation outlet 2~ for the havy phase at the bottom;
preferably, a screen 21 disposed between the coalescing chamber
3 and the outlet 20 prevents the outlet being a direct
extension of the fins 18 and creates a vertical speed reversal
favourable to decantation.
Figure 1 is only a basic view in the assumed case of a
prismatic apparatus with rectangular chambers. Figures 2 and
relate to an apparatus of the cylindrical type.
2G The apparatus shown in Figures 2 and 4 comprises two
vertical cylindrical walls 22 and 23 which define an annular
space between them.
1:~4~
The inlet 26 for the liquid to be treated opens into the
upper part of this space below a collar 24 adjoini~g the outer
cylindrical wall 22 and facing a collar 25 adjoining the inner
cylindrical wall 23. These collars, which are halves only of
truncated cones ~see Figure 4), perform the functions of the
deflectors 5 and 6, respectively, of the embodiment of ~'igure
1.
The heavy phase descends into a lower zone of the annular
space on one side of a vertical partition 27 and makes its way
horizontally towards the other side of this partitition,
passing through a set of horizontal fins 28 constituted by half
discs ancl which perform the function of the fins 18 of the
embodiment of Figure 1. I~hen the liquid arrives on the other
side of the partition 27, it passes into a tube 29, the inlet
of which is in the bottom part of the annular space. This
routeing of the liquid from one side of the partition 27 to the
other is shown diagramMatically by the curved line 30 in Figure
3.
The pipe 29 opens out inside the space 31 within the inner
wall 23, where the heavy phase is evacuated through a bottom
outlet 32, while the light phase is evacuated through a top
outlet 33. The space 31 constitutes the outlet chamber.
Moreover, the light phase which has been separated by the
action of the collars 24 and 25 is extracted through an outlet
34 at the top of the annular space.
26 The ligh~ phase outlets 33 and 34 may be under the control
of valves 35 and 36 operated by level detectors 37 and 38.
Figure 4 shows only the walls 22 and 23, the collars 24
~v~
and 25, some of the fins 2~, the vertical partition 27 and the
other vertical partition 39 against which the collars starting
from the partition 27 terminate.
It is to be noted that the coalescing chamber is of
particularly simple design and does not present the
inconvenience of apparatus having a coalescing cartridge. This
is permitted by the fact that the coalescing chamber has to
treat only a mixture which contains no more than residues of
hydrocarbons, the major part of the hydrocarbons having been
separated in the decanting chamber.
For example, a mixture containing 25% of hydrocarbons (by
weight) in water, injected at the inlet of the illustrated
apparatus can give a heavy phase (water) containing less than
50 ppm of hydrocarbons (by weight) after passing through the
apparatus.
The present invention is not restricted to the embodiments
which have been describe(l.
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