Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Fteld of the Inventlon
This invention relate3 to a~pa~atus and process use~ul
~or desaltin~ and/ordehydratlng oll-contlnuous emulsions such as
crude petroleum 0113, althou~h the~ can be used ln the re~olutlon
o~ other e~ul~ions> whlch term is hereln used as lncluding dl~-
perslons. More particularly, th~ lnvention ~elates to such
appar2tus and praces~ employ~ng multlple electrode~dl~trlbutor
3ystem3 loczted ln a single ~esselO
Background Or the Inv~ntlo~
It is conventional to desalt or dehydrate oil-continuous
emulslons by in~roduclng such emul~ions dlrectly lnto an electric
z
treating field of suEficient intensity to coalesce the suspended
droplets of the dispersed phase into masses of sufficient size
to gravi-tate from the oil. The dispersed phase of such emulsions
is composed of a material, usually aqueous, that is sufficiently
immiscible with the oil to produce an internal or dispersed
phase. Initially, the dispersed droplets are of such small size
or are so stabilized that they will not readily gravitate from
the oil phase. E~owever, the electric field coalesces such dis-
persed droplets, and it is found that -the resulting coalesced
masses gravitate rapidly from the oil, usually in the same
container as that in which electric treatment taXes place. In
a desalting operation, a quantity of water may be mixed with the
incoming crude oil in a valve or other mixer, all as well known,
so that a more complete removal of salt from the oil may be
accomplished. Typical of such prior art dehydrator/desalters is
that described in U. S. Patent No. 2,880,158 to Delber W. Turner
and a version for use on shipboard described in U. S. Patent No.
3,736,245 to Frederick D. ~atson and Howell R. ~arvis. Other
related prior art U.S. Patents are the following:
2,033,446 2,527,690 2,848,412 3,250,695 3,592,756
2,072,888 2,543,996 2,892,768 3,531,393
2,4~3,646 2,557,847 2,894,895 3,577,336
and German Patent No. 1,014,076 ~Helmut Stock; August 22, 1957).
It is an object of this invention to provide a
dehydratinq~desalting apparatus, especially useful for desalting
crude oil, that employs multiple electrode/distributor system
located in a single vessel to achieve serial stage desalting and/
or vastly increased oil handling capacity in a parallel stage
operation.
A n~
Fu~ther objects oE the invention will be evident to
those skilled :in the art iu the course of the following
description.
Summary oE the Invention
In one particular aspect the present application, a
divisional of co-pencling Canadlan Application ~o. 319,414,
filed January 10, 1979, is concerned with the provision of
an apparatus for treatment of oil-continuous emulsions containing
a dispersed aqueous phase, said apparatus comprising a closed
vessel which is provided therein with a plurality of coalescing
stages, said stages being hydraulically substantially independent
to allow parallel stage operation, there being contained within
said closed vessel: a plurality of horizontally disposed planar
permeable electrodes in vertically spaced relationship, said
electrodes being adapted to provide superimposed electric fields
to cause coalescing of suspended droplets of the dispersed
aqueous phase; distributor means between each pair of adjacent
electrodes adapted to cause emulsion to flow between said
adjacent electrodes; conduit means for supplying emulsion to
said distributor means, said conduit means being common to each
of said distributor means; product withdrawal and outlet means
in the upper portion of said vessel; and water withdrawal means
in the lower portion of said vessel, sal.d permeable electrodes
and the vessel interior being adapted and arranged to permit
water to pass downwardly through said electrodes to the lower
portion of said vessel.
In another particular aspect the present application is
concerned with the provision of a process for treating a
petroleum oil comprising emulsifying said petroleum oil with
~ 3-
water to form an oil-cont:Lnuous emulsion containing a
dispersed aqueous phase, passing said emulsion horizontally
in a plurality of parallel stages between horiæontally
disposed permeable electrodes in vertically spaced relationship
contained in a single vessel, said stages being hydraulically
substantially independent, but with no impermeable barriers
between them~ whereby said emulsion in each stage is subjected
to an electric field provided by adjacent electrodes, the
electric fields in the several stages being superimposed, and
the suspended droplets of the dispersed aqueous phase are
coalesced, thereby breaking the emulsion, allowing de-emulsified
water to pass downwardly through said electrodes to the lower
portion of the vessel, allowing the treated petroleum oil to
rise and pass between the edges of the upper electrode and the
wall of the vessel, and w:ithdrawing the treated petroleum oil
from the upper portion of said vessel and water :Erom the lower
portion of said vessel.
In a further particular aspect the present application is
concerned with the provision of a process for treating an
oil-continuous emulsion containing water as a dispersed aqueous
phase, comprising passing said emulsion horizontally in a
plurality of parallel stages between horizontally disposed
permeable electrodes in vertically spaced relationship contained
in a single vessel, said stages being hydraulically substantially
independent, but with no impermeable barriers between them,
whereby said emulsion in each stage is subjected to an electric
field provided by adjacent electrodes, the electric fields
in the several stages being superimposed, and the suspended
droplets of the dispersed aqueous phase are coalesced, thereby
~ 3a-
breaklng the emuls:ion, allowing de-emulsified water to pass
downwardl~ through said electrodes to the lower portion of
the vessel, allowing the treated petroleum to rise and pass
between the edges of the upper electrode and the wall of the
vessel, and withdrawing the treated petroleum oil from the
upper portion of said vessel and water from the lower portion
of said vessel.
Detailed_Description of the Invention
The inventlon is il~ustrated by but not limited to the
following e~emplary embodiments.
~eferring to the drawings:
Fig. 1 is a transverse vertical cross section of one
embodiment of an electrical treater of the present invention
intended for serial stage operation.
Fig. 2 is a longitudinal vertical cross section taken
along line 2-2 of the electrical treater shown in Fig. 1.
Fig. 3 is a transverse vertical cross section of another
electrical treater of this invention intended for serial stage
operation.
Fig. 4 is a vertical cross section of yet another electrical
treater of this invention intended for serial stage operation.
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Fig. 5 i5 a vertical cross section of an electrical
treater oE this invenLion intended or parallel stage operatiOn.
Fig. 6 is a schematic :illustration of a vertical
cross section of a three stage series electrical treater of
~his inve~tion.
Eig. 7 is a transverse vertical cross section of
another embodiment of the electrical treater of present inven-
tion intended for parallel stage operation
Fig. ~ is a longitudinal vertical cross section
of the electric treater shown in Fig. 7.
~ igs. l and 2 illustrate one embodiment of the
invention, especially useful when it is desired to convert
an existing Petreco high velocity desalter to two stage series
operation. The desalter consists of a horizontally disposed
generally cylindrical vessel 1 having rounded ends 2, which
may suitably have a diameter of about 8 to 14 feet. Lengths
of about 25 feet and 49 feet and as much as 133 feet have
proved suitable with a 12 foot diameter vessel. Inside the
vessel 1 are three horizontally disposed planar electrodes 3,
4 and 5. ~pper electrode 3 and bottom electrode 5 extend
almost the entire length and width of the-vessel 1, electrode
5 being downwardly curved in the vicinity of its longit~ldinal
axis to accommodate distributor 6. These electrodes are
energized. Middle electrode 4, which is at ground potential,
is in contact with the wall of vessel 1. The electrodes 3,
4 and 5 are spaced about 6 to 15 inches apart, 10 inches being
very suitable. Each electrode may be permeable, eg, be a grid
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of metal rods or pipes, suitably of cold finished steel, of
a structure similar to that shown in Patent No. 2,8809158.
A distributor 6, serving as the first stage dis-
tributor, and shown here as a box-like conduit or header,
ex~ends horizontally for most of the length of vessel 1 just
under middle electrode ~!, to which it may be attached, and
along its longitudinal axis. Bottom electrode 5 may be down-
wardly curved as shown in the vicinity of its longitudinal
axis to accommodate distributor 6. Orifices 7 are provided in
the sides of the conduit all along its length. However,
instead of a box-like conduit, a pipe with holes drilled in
it may be substituted. Distributor 6 is supplied by mixing
valve 8 via conduit or riser pipe 9. Mixing valve 8 is supplied
by oil conduit 10 and water conduit 11, which may be connected
with pump 12 and recycle conduit 13, as shown, and/or a
fresh water source not shown. Interstage outlet collectors 14
which may be drilled pipes supported at the vessel wall wi~h
angle clips (not shown) extend longitudinally along the sides
of tank 1, and are connected to conduit lS which leads to oil
recycle pump 16 and thence to conduit 17. Conduit 1~, con-
nected to a fresh water source, leads into conduit 17, which
leads to mixing valve 19. A conduit 20 extends from mixing
valve 19 to distributor modules 21, which may be similar in
structure to that shown in Turner Patent No. 2,5~3,9~6 or
Turner Patent ~o. 2,527,690. Although three such modules are
shown here~ a lesser or greater number may be employed. For
example, in a 49 foot long vessel, four such modules may be
used. An outlet collector 22, which may be a pipe with holes
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~2
drilled in the upper wall, extencls horizontally along the top
of tan~ 1 and leads to outlet 23 and conduit 24. A waeer
effluent conduit 25 is connected to the lower part of vessel 1.
In operation, the temperature of the crude oil
depencls upon the crude specific gravity and the type of crude.
However, in many cases of crude oil, temperatures of between
about 100F. and 350F., with about 250 F. being optimum, are
used. The pressure must be sufficient to keep the oil and
water mixture liquid at the operating temperature. The crude
oil is charged by conduit 10 and water is added via conduit
11, which is supplied by recylce conduit 13. The oil may be
brought to the desired temperature by any suitable procedure,
such as by heat exchange with another refinery stream. The
amount of water added is suitably about 10% of the crude oil
charged. The two fluids are mixed in mixing valve 8 to form
an emulsion. The emulsion is carried through riser pipe 9
to the first stage distributor 69 from whence it flows between
middle electrode 4 and bottom electrode 5 in either direction
in a generally horizontal transverse direction toward the
sides of the vessel 1 where the interstage collectors 14 are
located. Water which has been thrown out of emulsion by the
electric field between electrodes 4 and 5 falls toward the
bottom of vessel 1, where a pool of collected water is main-
tained. The main portion of the treated oil is taken up by
collectors 14 and is pumped by interstage pump 16 to conduit
17. A 5~ addition of fresh water takes place in this conduit
and is emulsified into the oil by mixing valve 19. The second
stage emulsion thus formed is carried by conduit 20 to second
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stage distributors 21. fronl whence it flows between electrodes
3 and ~ in either direction, more or less transversely, to
the sides of the vessel 1. The treated oil passes upwardly
near the edge of electrode 3 and along the sides of the vessel
1 and leaves the vessel by means of outlet collector 22,
outlet 23 and conduit 24. The ar~ows shown in the figures
indicate the path of the fluids through the conduits and, in
a general way, ins;de the vessel 1.
The level of the interface 26 of the water with
the treated oil may be maintained automatically at the
desired position in the lower portion of vessel 1. As shown
in the drawings, this is accompl.ished by means of motor valve
27 on effluent conduit 25, which valve is actuated between
open and closed positions by a float 2~ connected to a control
unit 29, which delivers an actuating signal through an inter-
connection, indicated by dashed line 30, to valve 27. The .
10at 28 senses the water level interface 26, and the valve
27 is controlled to maintain the interface 26 at the desired
level in the lower portion of vesse:l 1. Other liquld level
control means for maintaining the interface 26 at the desired
level, such as an electrical capacitance probe, may be employed.
While the above described embodiment is of special
interest in the conversion of existing desalting units having
distributors 21 already present, desalters are also contem-
plated and within the scope of this invention wherein both
the first and second stage distributors may take the form of
the boxlike conduit 6 or drilled pipe. Similarly, both first
and second stage distributors may take the form of distributors
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21. Moreover, either or both stage distributors may be sup-
ported hy and supplied either from the top or bottom of vessel
l, or otherwise.
In the embodiment described above, the top and
bottom electrodes 3 and 5 are each energized with its own
transformers~ here not shown, and the middle electrode ~
is at ground potential. 'llowever, it is also contemplated and
within the scope o~ this invention that the top and middle
electrode be charged individually and the bottom electrode
grounded. A potential difference of about 15,000 to 33,000
volts may suitably be maintained between electrodes 3 and 4
and between electrodes 4 and 5. The energized electrodes may -
be opposed electrodes if single phase current is employed or
two legs of a three phase current (3 phase open A) where the
grounded electrode is the middle one. Moreover, if a three
phase system is used, all three electrodes may be energized.
The supports and circuitry for the electrodes are omitted in
Figs. l and 2 but may be the same as that shown in Fig. 3,
described below.
Fig. 3 is a representation of a vertical cross-
section of an embodiment of the invention using a horizontal
cylindrical vessel l with boxlike conduits 6 and 6a as distri-
butors in both stages and otherwise similar in its main features
and operation to thaL shown in Figs. l and 2. The reference
- numerals in this figure correspond to those employed in Figs.
l and 2 for the same or similar features.
In this embodiment distributors fi and 6a are both
fed from below by riser pipes 9 and 20, respecti,vely. The
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z
wa~er leaves vessel 1 by means of a single conduit 13 which
supplies recycle water to conduit 11 and effluent to conduit
25a. Motor valve 27 on conduit 25a is actuated by a signal
from con~rol unit 29. Upper electrode 3a in this embodiment
is upwardly curved in the vicinity of its longitudinal axis
to accommodate distributor 6a, being symmetrical in this respect
to bottom electrode 5.
Electrode 3a is suspended by one or more vertical
insulators 31 and rods 32, as required to support the weight
of the electrode. Similarly electrode 5 is suspended by one
or more vertical insulators 33 and rods 34. Electrodes 3
and 5 are energized by transformers 35 and 36, respectively.
The middle electrode 4 is at ground potential. It is suitably
fastened to the vessel 1, for example, by means of attached
rail bars 43, vessel 1 being grounded. As shown here, trans-
formers 35 and 36 are step up transformers having reactors
37 and 38 in series with the respect:ive primaries. The secon-
daries have one end grounded and energize conductors 39 and
40, respectively9 which connect through entrance bushings 41
and 429 respectively, to electrodes 3a and 5.
Fig. 4 is a representation of a vertical cross
section of a spherical desalter such as the Petreco spherical
desalter which has been converted to two stage series opera-
tion. The reference numerals in this figure also correspond
to those employed in Figs. 1 and 2 for the same or similar
features. Vessel lb is a spherical container which may have
a diameter of up to 42 feet, suitably 18 feet. In th;s embodi-
ment, both first and second stage distributors 6b and 21b are
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bro~ t in ancl 9upplic'cl from tlle bottom of the vessel. The
first stage dlstributor 6b is, as shown here, a circular box
suppl:Led by concluit 9b and built aronnd riser pipe 20b and
having orifices 7b around its periphery to control flow distri~
bution. Electrodes 3b, 4b ancl 5b are circular, as required to
fit the cross section of the spherical vessel lb, electrode 4b
being suitably fastened to the vessel lb, for example, by
means of attached rail bars 43b, vessel lb being grounded.
~ollectors l~b, which may be drilled pipes arcuately shaped
to conEorm to the sides of vessel lb, and supported at the
vessel wall with angle clips (not shown), are positioned to
take up the main portion of the oil treated in the first stage.
The treated oil is carried by conduit 1~5b to recycle pump 16.
The operation o~ this desalter is otherwise similar to the
embodiments described above.
In each of the above described embodiments, the
exit velocity from the drilled pipe distributor or the orifices
of the distributor 6 or 6b is such that there is enough iner-
tial energy to carry the emulsion in a horizontal plane between
the treating electrodes 4 and 5 or ~b and 5b to the interstage
collectors 14 or 14b. These collectors are located to collect
the first stage treated oil and some "override" of fluid from
the second stage of treatment. The interstage pumping rate is
controlled so that it exceeds the rate at which the treated
oil is withdrawn from the unit by the second stage outlet
collector. This may be accomplished by operating the recycle
pump 16 at a pumping rate 10 to 20% Easter than the initial
charging rate.
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Fig. 5 is a representation of a vertical cross
section of a (lesalter having two paral~el stages. Such a
system has the potential o~ doubling the oil handling capacity
of a typlcal sing]e electrode, single distributor system.
The reference numerals in this figure correspond to those
employed in Figs. 1 and 2 for the same or similar features.
In this embodiment, riser pipe 9c supplies both distributors
6c and 6d, shown here as the boxlike conduit type. In opera-
tion, about 5% of water by volume based on the oil feed is
introduced by conduit 18c and pump 16c and is mixed in mixing
valve l9c with crude oil introduced in conduit lOc. The
mixture then passes into conduit 9c. The oil-water mixture
is distributed in two parallel paths, one between electrodes
3c and 4c and tile other between electrodes 4c and 5c, elec-
trodes 3c and Sc being energized and 4c being at ground potential.
The oil-water mixture travels toward the sides of vessel 1 in
each instance and thence upward toward outlet collector 22c
where the treated oil is withdrawn. The salt containing water
is separated from the oil-water mixture by the passage between
tlle electrodes and drops downwards into the pool of water at
the bottorn of the vessel lc, the level of which, represented
by interface 26, is maintained by effluent conduit 25, float
283 control unit 29, interconnection 30 and motor valve 27,
as described in connection with Figs. 1 and 2.
Three or more separate electrode-distributor
systems can also be used if higher oil handling capacities are
desired.
Fig. 6. is a schematic representation of a vertical
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~æ
cross sec~ion of a desalter employing three desalting stages
in serics. Ihe reference numerals correspond to those
employed in Figs. 1 and 2 for the same or similar features.
In this embodiment, a fourth planar, horizontally disposed
electrode 44 is employed in addition to the three electrodes
3d, 4d and 5d, similar to those shown in the previously
described embodiments. Electrode 44 is positioned below
electrode 5d. Electrodes 3d, 5d and 44 are energized and
electrode 4d is at ground potential. An additional distributor
6g~ positioned between electrodes 5d and 44, is employed in
addition to distributors 6e and 6f and a second interstage
collector 14e is employed in addition to first interstage
collector 14e. The distributors are all shown as bo~like
conduits~ In this embodiment, distributor 6g serves as the
first stage distributor; distributor 6f as a second stage
distributor; and distributor 6e serves as a third stage distri-
butor. Fresh water for desalting is supplied to each desalting
stage, although recycle water may be employed in the first
stage. The treated product leaves the vessel 1 through outlet
coliectors 22d and water is removed through outlet 25d. The
various conduits, valves and pumps removing and supplying
fluids to and from the various stages and the electrical cir-
cuitry are not shown, but their nature will be evident from the
descriptions of the embodiments shown in Figs. 1 to 4.
In an analogous manner to that of Fig. 6, desalters
with more than three stages ~ay be constructed.
Figs. 7 and 8 are representations of transverse
and longitudinal cross sections, respectively, of the internal
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52
details of a desalter having two parallel staKes, such as
shown in Fig. 5. The embodiment shown is especially useful
in the conversion of an existing Petreco low velocity desalter
to parallel stage operation. The reference numerals in these
figures correspond to those employed in Figs. 1, 2, 3 and 5
for the same or similar features. As shown in Figs. 7 and 8,
the desalter comprises a horizontal cylindrical vessel le
with hemispheric heads 2e. Upper and lower portions, 6c
and 6d, respectively, of a box-like conduit type distributor
extend horizontally for most of the length of vessel le and
are equipped with rows of orifices 7c and 7d along its length
on both sides. The distributor is supplied with oil-water
emulsion produced by a mi~ing valve, not shown, by riser pipe
9d and riser pipe e~tension 9e. Grounded electrode 4e is
supported at the sides of vessel le and the distributor by
rail bars 43 and 44, respectively. Charged electrodes 3e
and 5e are supported by vertical insulators 31e and 33e~
respectively, and rods 32e and 34e, respectively, said insula-
tors being supported from the upper part of the wall of vessel
le, as by hooks 45 and 46, and stabilized structurally by tie-
rods 50, which also serve as electrical conductors. Power
is transmitted to the charged electrodes 3e and 5e by a wire
conductor 47 passing through entrance bushing stub 48, spring
contactor 49, ~ie-rods 50 and from thence by rods 34e to
electrode 5e and by monel tiller rope 51 and rods 32e to
electrode 3e. Outlet collector 22e, supplied with vortex
spoilers 52 at its intakes, leads to product effluent conduit
24e. The level of the interface 26 between the water and the
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i552
oil is maint<lined by a level controL, not sllown, which is
actuated by displacer hanger rod 53, connected to displacer
54, a weighted, tubular sealed float, which moves up and down
with the level change. (The water layer is not shown in
section so as not to obscure details of the drawing.) Dis-
placer 54 iS guided by displacer shield 55 which is supported
by supports 56. Displacer 54 is designed to exert a predeter-
min~d tension on rod 53 under the operating pressure and
temperature, with the bottom half of the displacer in the
water layer and the top half in the oil layer. Since there is
not a sharp demarcation between the two layers, displacer 54
is made long to allow for an emulsion of oil and water to
exist at the oil-water interface. The predetermined tension
on rod 53 is transmitted to a level control sensor instrument,
not shown , which converts the tension stress into torsion
which twists a torque tube. This in turn causes movement of
a Bourdon tube which affects the air being delivered to actuate
a water bleed valve, not shown on an effluent conduit, also
not shown, connected to outlet 25. A rise ln the water level
lessens the tension on rod 53 and a fall in the water level
increases it, causing the water bleed valve to open or close
and thus readjust the water level to balance the forces in
the control system. Water effluent outlet 25 is located in
the lower portion of vessel le. A low level float 57 operates
to maintain safety when vessel le is not liquid full. If
the liquid level falls to a predetermined position, electri-
cally conductive arm 59 attached to float lever 58, also
electrically conductive, makes contact with conductor 60,
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attached to tie-rod 50. Float lever 58 is connected to pivot
point 61 on support 62, which is connected structurally to
vessel le. When arm 59 contacts conductor 60, conductor 60
is thus electrically connected with the grounded vessel le.
Any vapor accumulation in vessel le concomitant with the drop
in liquid level thus causes float 57 to drop and a short cir-
cuit to occur. With the short circuit and resultant reactance,
the voltage to the transformer is so reduced that no high
voltage is admitted to electrodes 3e and 5e via conductor 47.
Therefore, the possibility of a spark and resulting explosion
if air were also present in the vapor is avoided. The mode
of operation of this embodiment is otherwise as described in
connection with Fig. 5, the path of the oil being shown by
the arrows.
A hori~ontal parallel stage desalter as above
described, measuring 8 feet in internal diameter and 6 feet
hori~ontally, tangent to tangent, was used to treat 48 API
waxy Michigan crude oil. The oil was treated at 260 F. with
l pint of liquid demulsifier consisting of a mixture of an
oxyalkylated plenol-formaldehyde resin, an ammonium salt of
an alkaryl sulfonate and an acylated polyalkanolamine, all
in solvent, added per lO00 barrels of crude oil (said demulsi-
fier being a Tretolite demulsifier of the Tretolite DS
series of demulsifiers~, the pressure differential across
the mixing valve being lO p.s.i.g., the voltage being 440
volts and the load lO amperes. A charge rate of 6500 barrels
per day was employed, the crude being desalted from 80 pounds
to l pound per thousand barrels of oil. Bottom sediment and
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water (~S&W) in and out was 0.2%. [n another run, at a
temperature of 253 F., the desalted oil conLained 18 pounds
per thousand barrels with 400 volts and a 23 ampere load.
Other Tretolite demulsifiers of the Tretolite DS series
or any functionally equivalent desalting liquid demulsifier
may also be used.
Other electrode arrangements than those described
in the above embodiment may be employed in parallel stage
desalting, for example, arrangements corresponding to those
described in connection with Figs. 1 and 2, above. Similarly
the oil temperature and pressure parameters and potential
difference between electrodes described in connection with
Figs. l and 2 apply also to parallel stage desalting.
The various distributors, collectors and electrodes
described above may be supported in part by conventional means
well known in the art, such as guy wires, in addition to
being supported by the conduits and other support means disclosed.
It will be apparent Erom the foregoing description
that the invention is not limited to a particular shape of
vessel, electrical circuitry, voltage employed, type of dis-
tributors, water level control means, arrangement of conduits,
etc. Many embodiments, modifications, developments, and
variations of forms are contemplated as long as they fall
within the broad scope of the appended claims.
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