Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method and apparatus for the separation
of two immiscible liquids, especially but not exclusi~ely limited to removing
contaminating oil from water.
Water/oil separators for removing oil from water are generally based
on passing a waterJoil mixture through a coalescing media and then separating
the two liquids by gravity or, by using gravity separation alone associated
with sophisticated geometry within the separator. Coalescing materials in
fixed beds, expanded beds, mats, batts, cartridges, etc., are inherently
limited to low flow velocities through these media of something less than 0.5
ft/minute because at greater flow velocities the turbulence or agitation
created within these media tend to emulsify the contaminating oil rather than
- coalesce it. In order to achieve a higher degree of clarification of the
~ water effluent, smaller orifices between the material of the coalescing media
; are required. The smaller the orifices, the more severe the inherent tend-
ency of these coalescing media to clogging by fine particulate material,
necessitating more frequent cleaning or replacement. Progressive clogging
continually increases the restriction of flow through the coalescing media
bed. Each separator using these techniques is, therefore, a compromise
between the high degree of water clarification desired and the practical limits
- 20 imposed by the very low flow rate required to achieve it.
The use of gravity separation also imposes a similar compromise
between the degree of water clarification desired and the flow rate because
of the long time required to permit the various sizes of fine oil droplets to
rise to the surface. To achieve a reasonably high degree of water clarifica-
tion, a long residence time in a quiescent zone is required. This severely
reduces the flow rate through the separator and limits the degree of water
clarification which is practical.
The object of this invention is to provide a simple and economical
method and apparatus for removing contaminating oil from water, by which it
is possible to greatly increase the flow rate, eliminate clogging, insure
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continuous and uninterrupted operation, increase the degree of clarification
of the water effluent, recover more oil, and greatly reduce the size of the
apparatus which is required.
This invention is generally applicable to all oily substances sus-
ceptible to being coalesced in the presence of the continuous liquid. The
method and apparatus described herein are suitable for the separation of many
immiscible liquid combinations, so long as the coalescing granules selected
have an affinity for the suspended oily particles and not for the continuous
liquid phase. Since the invention, however, is primarily directed to the
removal of oily particles from water, the invention will be described with
reference to its normal form in which the contaminating material is oil, and
the aqueous liquid is water.
The method of this invention separates oil from a mixture of oil
in water by first passing the mixture upwardly in a column through an upwardly
unconfined mass of oleophilic granules having a specific gravity greater than
water with a velocity adequate to separate and lift the granules individually
so that they are completely free from mutual support in the upwardly rising
mixture within the column. The velocity should not be so great that it will
prevent the granules from descending against the flow of the mixture. It is
also preferable that the granules not strike a steeply inclined screen posi-
tioned above the mass of granùles. The granules move up and down within the
column and collect and coalesce the fine particles of oil within the mixture
and ~elease the surplus oil back into the rising mixture column in the form of
visible oil droplets. The rising mixture column then transports these large
oil droplets upwardly to a steeply inclined screen to force the oil droplets
to engage the screen. It is preferred to incline the screen at an angle of
at least about 75 to the horizontal which corresponds to a maximum of about
15 to the upward flow of the mixture column. These large oil droplets impinge
on the material of the inclined screen and form a film of oil on the material
of the said screen which is propelled upwardly by the force of the upward
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flow of liquid through the inclined screen. This moves the oil to a solid
oleophilic path, which is usually the wall of the container, and then up-
wardly to an oil storage chamber and oil outlet. The water passes upwardly
through the inclined screen, and then flows to a water receiving chamber and
water outlet.
Screens constructed and arranged to permit the passage of both oil
and water in a mixture thereof, in the direction of the main flow, are well
known. Screens constructed and arranged to permit the passage of oil and
prohibit the passage of water in a mixture thereof, in the direction of the
main flow, are also well known. However, the construction and arrangement of
a screen with associated apparatus to permit the passage of water and prohibit
the passage of oil is believed to be new, and is a feature of this invention.
I have discovered that a screen which is steeply inclined as
previously described will remove oil and permit the passage of water under
flow velocities varying from approximately 6-90 ft/minute. The flow of the
liquid at these velocities causes the oil film to be uniformly distributed on
- the material of the steeply inclined screen, and the force of the flow of
liquid through this steeply inclined screen propels the oil film under laminar
- flow conditions, along the material of the inclined screen in the general
direction of the flow without having the oil film exhibit any tendency to
reform into drops which might be released back into the water flowing through
the inclined screen. If, due to high oil concentration, the capacity of a
single inclined screen is exceeded, two or more inclined screens in series
can be uset to remove any oil droplets released by the first inclined screen.
In order to remove emulsified oil as well as visible oil droplets
from a fast moving oil-in-water mixture, it became necessary to depart from
conventional coalescing practices of fixed beds, expanded beds, coalescing
cartridges, etc. and seek a method which is devoid of agitation and turbulence
at high flow rates to prevent the reemulsification of the oil passing
from the coalescing media. Translating this into practice, it became nec-
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essary to create an environment in the coalescing zone in which each coales-
cing granule operated independently, and free from mutual support, to be
acted upon solely by the force of gravity with respect to the water-oil mixture
column. I have discovered that within the previously noted range of flow
velocities, individual granules of a mass of oleophilic granules will rise
and fall individually in an upwardly rising non-turbulent mixture column,
acted upon by the resistance of the granule to the upward direction of flow
of the mixture column and the downward velocity created by gravitational
acceleration. This creates a non-turbulent situation within the column
; 10 which favors coalescing emulsified particles as well as small visible oil
droplets, yet is without the subsequent agitation and turbulence necessarily
present in exiting from conventional fixed coalescing beds, expanded beds,
cartridges, etc., when flow velocities exceed approximately 0.35 ft/minute
through the small orifices of these media. With granules having specific
gravities varying from approximately 2.0 - 3.5, the flow velocities required
to activate the granules individually in the mixture column as described
above, are within the noted limiting flow velocities required for the satis-
factory operation of the steeply inclined screen.
As each oil coated oleophilic granule rises and falls vertically
in the non-turbulent rising mixture column, it cleanses a portion of the
mixture column of fine oily particles and coalesces them until an accumulation
of surplus oil on the granule is sheared off by the passing mixture column
- in the form of an oil droplet which is released back into the mixture column
and then transported upwardly with the mixture column (now largely free of -
fine oil particles) to be intercepted and extracted from the mixture column
by the steeply inclined screen as previously described.
This invention will be described employing a preferred construction
in which the separator has the form of a vertical cylinder, but the invention
is not restricted to cylindrical geometry.
There is no restriction as to size and a small separator would be
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applicable to a sm all industrial flow exiting into a sewer system. Of greater
importance in the light of the high flow rates permitted by this invention,
is the fact that separators of reasonable size are applicable to large indus-
trial systems such as an oil refinery, oil field, oil drilling platfo~m, harbor
terminals, heavy industrial installations, etc., with effluents exiting into
natural waters. It would be highly effective aboard ships for cleaning bilge
wastes and also for cleaning ballast water on oil tankers or other ships whose
wastes are contaminated with oily substances. It would be particularly appli-
cable to large oil spills at sea where a severe requirement exists to separate
oil rapidly from large volumes of sea water, simultaneously recovering the
oil and retu~ning clean water to the environment. When the concentration of
oil in the water is higher than can be efficiently handled with a single
separator, then two separators should be used in series.
The oleophilic granules which are employed may be of diverse
- character and are heavier than the water which is passed upwardly through
the granules. Silica particles of appropriate size can be used, but these
are preferably treated to increase their affinity for oil. Aluminum granules
are also useful. The preferred density of the oleophilic granules is in the
range of 2.0 - 3.5 as noted previously. Particle size is not of prime
significance, so long as the particle is able to resist being carried away
by the moving liquid. -
It is essential that the mass of oleophilic granules be unconfined
above the foraminous support which supports the granules when the apparatus
is not in use. If the granules are confined, then the granules are packed -
together by the moving liquid, and this severely restricts flow, and the
accumulation of material in the compacted bed further restricts flow. Also,
when the granules are packed together, severe reemulsification would result
at the high flow rates at which this separator is designed to operate.
It is stressed that the conventional coalescing media, relying on
small orifices for coalescence, becomes clogged with foreign particles in
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use and must be replaced or its materials must be cleaned frequently. In this
invention, the granules need not be replaced or cleaned since the surplus oil
collected by the granules is continuously removed therefrom. Fine particulate
material passes through this separator without clogging.
The invention will be more fully understood from the accompanying
drawings in which:
Figure 1 is a vertical cross-sec~ion of an illustrative separator
constructed in accordance with this invention, and employing a cylindrical
geometry,
Figure 2 is a simple schematic cross-section illustrating the method.
Figure 3 shows a modified cylindrical configuration in which the
- purified water passes straight through the separator with the oil being
tirectet into an annular chamber.
Pigure 4 is another vertical cross-section showing a rectangular
configuratio~ and using a steeply inclined screen in a "V" shape to direct
oil to flow to both sides. This unit is particularly adaptable to modular
construction within a common container.
Referring more particularly to Figure 1, a mixture of oil in water
prescreened to eliminate foreign particles larger than the screen size used
hereinafter to separate the oil is pumped to a separator assembly identified
generally by the numeral 10, The separator 10 has an inlet 11 at its lower
end through which the mixture flows into a mixture inlet chamber 12 which is
positioned at the bottom of a vertical tube 13. This tube 13 takes the form
of a container which is concentrically positioned within the outer walls of
casing 16 of the separator 10. This mixture inlet chamber 12 is formed
beneath a foraminous support 14 ~a screen) which is positioned above the bot-
tom of the tube 13 by means of a supporting structure 15.
Contained in tube 13 and resting on screen 14, aTe oleophilic
granules 17, these granules having a specific gravity greater than water as
previously explained.
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The inner container 13 is partitioned as shown at 18 so that the
screen 14 is divided into a series of side by-side zones. This is done when
the container 13 is large, and it serves to maintain an even distribution of
granules across the screen 14. As can be seen, the mixture passes through the
inlet 11 into the chamber 12, and passes upwardly as shown by arrows A with
sufficient velocity to lift the granules 17 as previously described, and then
through the inner container 13 toward an overhead steeply inclined screen
which is here constituted by a conical screen 19.
The upper end of the inner container 13 is notched forming teeth
20, and the upper end of the inverted conical screen 19 is secured to the
container wall below the lower end of the teeth 20. As a result, water
flowing upwardly through the container 13 will pass upwardly through the
inclined screen 19, and any drops of oil which have been released by the
granules 17 will be intercepted by the inclined screen 19, and form a film
. on the material of the screen. The upward pressure of the water passing
through the screen forces the oil upwardly on the screen until it contacts
the wall of container 13, and the oil will continue to move upwardly on
~` teeth 20 at the upper end of container 13. The screen, the wall of container
13, and the teeth 20 pro~ide a solid oleophilic path for the flow of oil to
storage.
The steeply inclined screen removes all the visible oil. The angle
of inclination which is needed is easily found for any screen by a brief check,
or it can be approximatet by tilting the screen until the eye can discern no
open spaces. An angle of at least about 75 to the horizontal is generally
required.
Overlying the upper end of the container 13 is a conical oil col-
lector 21, the teeth 20 contacting the interior of the conical collector 21.
As a result, the oil collected by the screen 19 is forced upwardly along the
oleophilic path until it reaches the conical collector 21 which leads to an
oil storage chamber 22 positioned at the upper end of the oil collector 21.
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The recommended oil-water interface level in the device is shown by the phan-
tom line X-X. An oil-water interface sensor and flow restrictor float 23 is
provided to prevent water from flowing upwardly out of the oil collector 21
via the oil outlet 24, When too little oil remains in collector 21, the
interface sensor 23 rises to prevent water from exiting via outlet 24.
At the same time that the oil is exiting from the separator 10
through outlet 24 as described, water which has passed through the screen 19
flows outwardly through the space between teeth 20 which extend above the
screen 19 and below the oil collector 21. The water, now free of oil, is
then passed through the annular chamber 25 formed between the exterior casing
16 of the separator and the container 13 to the water outlet 26,
The operation of the separator structure shown is extremely simple,
it being only necessary to pump the mixture through the separator, clean
; water exiting at 26, and the collected oil exiting at 24. The overall level
of liquid in the separstor shown by the phantom line Y-Y provides sufficient
pressure head to raise the oil levelto the oil outlet 24. A pressure actu-
: ated one way valve 27 in the inlet line 11 insures a minimum flow rate and
it also prevents back flow from accidental pressure drop or shutdown which
might result in oil entering the clean water exit route.
The structure shown enables satisfactory operation even when
the separator is tilted as might occur aboard ship. A skirt 28 which
tepends downwardly from the lower end of the conical oil collector is provided
to contain the water-oil interface level within collector 21 during tilts,
The method of this invention is simply shown in the schematic cross
section of Figure 2 which uses the same numbers employed in Figure 1.
As can be seen, the mixture of oily particles in aqueous liquid
enters at 11, and moves past valve 27 to a foraminous support 14. The mass
of oleophilic paTticles rests on screen 14 between levels A-A and B-B when
there is no flow. The optimum depth of the mass of granules at rest may vary
between about 6 to 18 inches in height, depending on the effectiveness of the
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particular granules. When the mixture is being pumped through the separator
with adequate velocity, the granules are lifted as individual granules free
fr~m the support of other granules, into a contact zone which lies generally
below the level C-C which is the bottom of the steeply inclined oil inter-
ceptor screen 19. The distance between the levels B-B and C-C is normally at
least 20 inches, and is more preferably at least 30 inches. The granules 17
rise and fall individually as indicated, effectively scrubbing the oily part-
icles out of the mixture, Ultimately, drops of oil D are released by the
granules 17, and these are propelled upwardly by the rising mixture until they
strike against the screen 19 merging into the oil film thereon. This film is
propelled upwardly to the top of the screen where it engages the side wall
of the container 13, the oil moving along a continuous oleophilic path to an
oil storage area 22. The level X-X identifies the oil interface, and Y-Y
identifies the water level at the water outlet 26. The oil exits via outlet
24.
Turning to Figure 3, the structure is very similar to that shown
in Figure 1, but the structure for the removal of oil and clarified water is
modified to simplify the structure and permit a plurality of separators to be
coupled within a common container.
Continuing to use corresponding numerals where appropriate, the
rising mixture passes through the cGntact zone below level C-C until it con-
tacts the conical screen separator l9. However, the top o~ the container 13
is not noSchet and, instead, a tube 31 is inserted so that the oil on conical
screen 19 is propelled upwardly and outwardly by the rising mixture to force
the oil onto the container wall 13 where it moves into an annular oil storage
cha~ber between the container 13 and the tube 31. This oil storage chamber
32 is closed at the top by a circular plate 33 which has an outlet 34 through
which oil may exit directly or may lead to an oil storage chamber which may be
common to several units. An oil-water interface sensor and valve arrangemen~
not shown may be used to maintain the oil-water interface at the leveI X-X
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in the common oil storage) but it is simpler to merely extend the outlet tube
above the water level Y-Y, as shown.
The water passing through screen 19 moves straight out through tube
31 to a tank 35. Many separator units would be positioned within tank 35
which would serve as a common receptor for all of the water which is purified.
Water exits from tank 35 via ports 36 which maintain the water level at the
level Y-Y.
Referring to Figure 4, the structure here is rectangular, rather
than cylindrical, the rectangular form being preferred where a plurality of
units are combined into a composite structure served by a common water receptor
as in Figure 3. Only the upper end of the structure in Figure 4 is shown since
this is all that is significant in this aspect of the invention. As will be
seen, the conical screen 19 is now transposed into a flat, V-shaped screen 40
so as to direct the oil which is intercepted by the screen to the parallel
side walls 41 and 42. The oil moving upwardly along the walls 41 and 42 finds
itself trapped within the closed oil storage chambers 43 and 44, respectively,
at the upper end of the structure, and the water passing through the screen
40 moves out of the apparatus, passing between the oil storage chambers
43 and 44. Where the unit is to be one of many within a common chamber,
the upper end of the unit between the chambers 43 and 44 is left open, and
the water simply spills out, thereby discharging into the common c~ntainer.
If the structure is to be used separately, then the upper end of the unit
can be closet, and the water can be piped off 85 desired from between the
oil chambers 43 and 44. Oil outlets 45 and 4~ are shown for tapping off the --
- oil which is collected in a common oil collector similar to that shown in
Figure 3.
It will also be appreciated that various adjuncts and controls
can be added but these are aspects of commercial Operation as opposed to the
; new oil removal structure, and the novel separation and recovery procedure.
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