Note: Descriptions are shown in the official language in which they were submitted.
The present invention concerns the removal of oil
from an oil in water emulsion, In particular it relates to
an apparatus for the removal of oil from an efflllent stream
consisting of an oil in water emulsion, It also relates to
a process for removing oil from an oil in water emulsion.
According to the present invention we provide an
apparatus for the removal of oil ~rom an oil in water emul-
sion which comprises a vessel, inlet means for introducing
the effluent stream into the vessel on one side of a per-
forated barrier extending across the vessel, porous sockssealed in a water-tight manner into each of the perforations
in the barrier in such a manner that the socks protrude from
the barrier on the downstream side thereof, said socks causing
coalescence of the emulsified oil droplets as the emulsion
passes therethrough, means located downstream of the barrier
for removing coalesced oil droplets from the stream and out-
let means through which the stream can leave the vessel,
The vessel may have a rectangular cross section or
it may have a cylindrical or part cylindrical cross-section.
Alternatively it may merely have an undefined curved or
other cross section, The vessel may be made from either a
metallic, plastics or a cementitious material.
Preferably the apparatus is provided with means,
located upstream of the barrier, for removing solids from the
effluent stream before it is passed through the socks, other-
wise the interstices in the walls of the socks may block
with solids. The means for removing solids, which may be
either located in the vessel or externally of the vessel,
may comprise a coarse screen and/or a settlement zone,
In general a coarse screen will serve to remove large par-
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ticles present in the effluent stream and a settlement zonewill serve to remove silt and other dense, finely-divided,
solids present in the effluent stream
The barrier may be constructed from any suitable
material When the barrier is a permanent fixture in the vessel,
then conveniently the barrier i9 constructed from a plastics
material, a metallic material or concrete When the barrier is
in the form of a removable penstock it may be constructed
from a metallic material, a composite material or a plastics
material.
In a preferred apparatus, the barrier takes ~he
form of a plurality of stoplogs stacked one above the other.
In practice it may only be necessary to provide perforations
in the lower, say two or three, stoplogs in the stack, the
remaining stoplogs being imperforate and serving to accommodate
the pressure head loss across the barrier. The use of barrier
comprising a stack of stoplogs offers a number of advantages
They are cheaper and can be removed more easily than other
above-mentioned types of barrier. They also allow greater
flexibility in operation, for example the throughput of oil
in water emulsion, separation efficiency or life-time~ can be
increased by replacing imperforate stoplogs with sock-carrying
stoplogs
Irrespective of the nature of the barrier used in
the apparatus, it will be provided with aplurality of, prefer-
ably, rectangular perforations having a side length of the
order of 90 mmO
The socks have a shape resembling a test tube by
which we mean that they are closed at one end and open at
- 30 the other end, the open end of the sock being sealed in a
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water-tight manner to the barrier either within a perforation
or to the periphery of a perforation on the downstream side
of the barrier so that the effluent stream flows through the
perforations in the ~arrier and then into the socks. It then
passes through the walls of the socks and coalescence of oil
droplets occurs. Conveniently the socks are easily removed
from and easily attached to, the barrier should they need to
be replaced.
A feature of the apparatus in use is thatsthe~socks
are immersed in the effluent stream, the stream being forced
through the walls of the socks by maintaining a difference
in hydrostatic head on opposed sides of the barrier. To
ensure that the socks are immersed in the effluent stream,
the apparatus is provided with means for ensuring that an
appropriate water level is maintained. Conveniently this
is an outlet spillway with its sill level some distance above
the uppermost perforations in the barrier.
The required difference in hydrostatic head will~ of
course,
'
depend not only on the total surface area of the socks and
the required liquid throughput but also on the porosity of the
socks. In general with most fibrous structures and with the
surface areas envisaged, the difference in hydrostatic head
will be in the range of 10 cm to 2000 cm,
Accordingly we also provide a process for the removal
of oil from an effluent stream of an emulsion of oil in water
comprising passing the effluent stream into a vessel and through
the walls of a plurallty of socks of a porous material sealed
in a water-tight manner in perforations in a barrier extending
across the vessel so causing coalescence of oil drop~ets into
a form in which it rises to the surface of the stream and re-
moving the coalesced oil droplets from the stream,
In preference the socks are constructed from melded
fibrous structures comprising fibres having particles on
their surfaces which exhibit oleophilic and hydrophobic pro-
perties, By "melded" is meant a fabric having fibriform
structure comprising an assembly of composite filaments which
is consolidated by the bonding of the filaments at cross-
over points or junctions betweencontiguous filaments, thebonding being achieved by the activation of a potentially ad-
hesive component of the composite filaments.
In a preferred apparatus according to the invention
we provide means located immediately downstream of the barrier
f~r inducing laminar flow in the stream passing through the
barrier. Suitable means for this purpose are a series of
inclined parallel plates or tubes,
Conveniently oil which coalesces when the stream
passes through the socks is diverted from the main stream
by an underflow weir. Coalesced oil floats to the surface
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3\8[)4
and can be removed from time to time by an apparatus for
removing coalesced oil which floats to the surface by suction
or sXimming Alternatively some other means may be employed
for removing the coalesced oil
In the accompanying drawing which depicts the
apparatus of the invention,
Fig. 1 shows in cross-section a divided vessel
containing the fabric filter socks of the invention and
Fig~ 2 shows an alternative embodiment wherein
the vessel has inlet and outlet ports.
The invention will now be described by reference
to the following Examples:
- EXAMPLE 1
An apparatus was constructed in accordance with the
invention and as illustrated diagrammatically in longitudinal
cross-section in Fig. 1 of the accompanying drawings
A rectangular cross-section vessel 1 was constructed from
concrete and had a width of 1.43 m, a height of 1.365 m and
a total length of 14 m. A moveable perforated penstock 2
having the approximate dimensions 1 4 m wide and 2 0 m high
and made from 3/4 inch thick blockboard was housed in the
vessel~ The penstock was provided with lÇ drilled circular
holes 3 (not all shown in Fig. 1) of diameter 9 cms at locations
where, with the penstock in position, they would be submerged
in the effluent stream to be treated A gasket (not shown)
was provided between the penstock and the wall of the vessel
A melded fabric wherein the fibres are adhesively
bonded at cross-over points, 1l area bonded" of 180 g/square
metre, produced from staple fibres of oriented i e drawn sheath/
core heterofilaments in which the core (50% by total weight
~ .
8(~
of the total weight of the filament) was polyethylene tereph-
thalate of meltiny point 257OC and the sheath was a copolymer
of polyethylene terephthalate and polyethylene adipate
(85:15 mole ratio) of melting point 220C,was passed through
a 2% dispersion of silane coated silica particles (SILANOX 101
Reg TM manufactured by Cabot Corporation) in trichlorethylene.
The dried fabric was passed through a conveyor oven at 240C
at a conveyor speed of 2 metre/minute (oven length 1 3 metres)
then cooled and rinsed with water to remove lightly adhering
particles.
Socks were made from the above area bonded melded
fabric Each sock was made as layflat with a 25 mm wide
longitudinal polyethylene bonded lap joint. At the closed
end, the top and bottom of the layflat are polyethylene bonded
together over a 10 mm wide 170 mm radius curved strip sym-
metrical above the layflat centreline. The overall sock
length is 850 mm, the circumference of the mouth 355 mm
Effective sock area is 0 29 square metres
The socks 4 were fixed downstream of the holes in
the penstock in a water-tight manner so that the effluent stream,
of necessity, had to pass through the walls of the fibrous
socks
Downstream of the penstock the vessel was provided
with an underflow weir 5 through which the treated stream
could leave the vessel via an overflow spillway having its
sill level some distance above the drilled holes in the pen-
stock. The coalesced oil droplets 6 formed a layer 6a on
the surface of the stream, from where it could be removed
The apparatus was used to treat an effluent stream
from surface drainage over a three month period, and the
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following xesults were obtained on five, randomly selected,
non-consecutive days in that period
Average Maximum oil concentration Oil concentration
flow flow (ppm) at inlet (ppm) at outlet
Day (m3/hr) (m3/ hr)
l 30 37 6.1 1.4
2 28 28 110 2 7
3 86 597 5.3 2 2
4 39 100 38 4 6
28 28 ll 0 2
EXAMPLE 2
An apparatus was constructed in accordance wîth
the invention and as illustrated diagrammatically in cross-
section in Fig. 2 of the accompanying drawings.
A circular cross-section tank 7 was constructed
from steel and had a diameter of 2 6 metres and a total length
6 metres. Flanged pipes 8,9 were fitted to either end of the
tank to allow flow of water in and out of the tank Part of
the tank roof 10 was removed to allow access into the tank
Within the tank a frame tnot shown) was constructed which
held a series of stoplogs 11 which could be slid in and out
of the frame. Each stoplog had a width of 1500 mm and a
.. . .
depth of 300 mm. Up to 7 stoplogs could be slid into position
at any given time, The bottom 3 logs wexe each prov;ided with
8 square holes (not all shown in Fig. 2) of side length 90 mm
Rubber sealing gaskets (not shown) were provided between each
stoplog and the frame attached to the tank wall.
An area bonded melded fabric of 180 g/square metre,
produced from staple fibres of oriented i.e drawn sheath/core
heterofilaments in which the core (50% by total weight of the
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8C~
to~al weight of the filament) was polyethylene terephthalate
of melting point 257C and the sheath was acopolymer of poly-
ethylene terephthalate and polyethylene adipate (85:15 mole
ratio) of melting point 22C, was passed through a 2% dis-
persion of silane coated silica particles (SILANOX lOl Reg,
- TM manufactured by Cabot Corporation) in trichloethylene,
The dried fabric was passed through a conveyor oven at 2400C
at a conveyor speed of 2 metre/minute (oven length 1.3 metres)
then cooled and rinsed with water to remove lightly adhering
particles,
Socks 12 were made from the above area bonded melded
fabric, Each sock was made from a sheet l m long and 0~54 m
wide, first forming a tube by sewing the edges and then closing
the bottom of the tube by sewing. The overall sock length was
1 m and the diameter of the mouth was 160 mm. Effective sock
area was 0,50 square metres,
~ he socks were fixed downstream of the holes in
the stoplogs in a watertight manner as mentioned above so
that the effluent stream, of necessity, has to pass through
the walls of the fibrous socks,
Downstream of the barrier the apparatus was provided
with an underflow weir 13 through which the treated stream
could leave the channel via an overflow spillway 14 having
its sill level some distance above the drilled holes in the
penstock, The coalesced oil droplets 15 formed a layer 15a
on the surface of the stream, from where it could be removed,
The apparatus was used to treat an effluent stream
from surface drainage and produced a final effluent containin~
no visible oil.
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, ~ 3.
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