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Патент USA US2412791

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Dec- 1'7, 1946-
|_. c. WATERMAN
‘ 2,412,791
_
METHOD FOR PURIFYING MINERAL OILS ‘.V
Original Filed March 4, 1940
2 SheetS-Sheet'l
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LOGAN C. W4 TERA/IAN
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Dec. 17, 1946.
|_' Q WATERMAN
2,412,791
METHOD FOR PURIFYING MINERAL OILS
Original Filed March 4, ‘1940
2 Sheets-Sheet 2
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‘B Y LOGAN C. MTERMAN
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Patented Dec. 17, 1946
‘j
2,412,791
UNITED STATES‘? PATENT .QlF‘ElQE‘ '
METHOD FOR PURIFYING MINERAL onts
Logan ClWaterman, Houston, Tex., assignor to a‘
Petrolite Corporation, Ltd., Wilmington, Del.,,a
corporation of Delaware
‘
, Original application March 4, 1940, Serial No.
322,093. Divided and this application October
13, 1941, Serial No. 414,791' '
2 Claims.
‘
,
(Cl. 204-190)
2
1.
This invention relates to method and appara- I '
tile for treating oils and, more particularly, to
an electric method and apparatus for the puri
?cation of crude petroleum.
'
Crude petroleum frequently contains water-_,
dispersible impurities. These impurities may be '
either molecularly or ionically dispersible in water
as _in the case of water-soluble salts, or dispersi
ble in water as solid particles as in the case of
particles of sand or silt having water-wettable or .
water-wet surfaces. These impurities are most
commonly represented by water-soluble salts
which may be present in the oil as crystals or,
more commonly, in the form of aqueous solutions
of brine dispersed as ?ne emulsi?ed droplets -
‘throughout the oil.
In United States Patent No. 2,182,145 to H. C.
Eddy, an electrical process for the removal of
l
with similar or other
droplets. "The degree‘ of Q
interfacial stabilization and the di?iculty of coa
lescing these droplets with other droplets, typi-‘
cally those of added relatively freshwater, may
be further increased by changes to which the oil
is subjected subsequent to its production. For
example, the oil as produced is normally at tem
peratures somewhat above normal atmospheric
‘temperature. As the oil cools, its solvent power
for emulsifying agents, such as asphalt, high mo
lecular weight acids, and the like,‘may decrease,
whereby these materials become more readily
available‘ for adsorption at and stabilization of
the interface. In additiomthe adsorbed mate
rials may be'reduced to below their melting point
by such cooling, whereby a solidi?ed interface
is formed which is very di?icult to treat.
'
The solvent power of the crude oil may also
saline and similar impurities from crude oil is
be decreased by partial vaporization of light by
disclosed, which provides for the subjection of a 20 drocarbons, such as may occur when the pressure
specially-formed synthetic emulsion to a high
on the freshly produced oil is substantially re
tension electric ?eld, thus producing coalescence
duced or where the oil is allowed to weather or
of the dispersed droplets of the emulsion into
is‘ctherwise stabilized, resulting in a condensa
masses of su?icient size to be readily removed
tion of heavy and/or solid emulsifying agents at
from oil by gravitational methods, including set
the interface.
‘
tling. The synthetic emulsion is formed by dis
Eliects other than reduced solvent power and
persing relatively fresh water in the oil to form
increased adsorption may also be involved in the
droplets which are coalesced with the brine drop
progressive increase in dif?culty of puri?cation
lets or other impurities in the oil by the action of
as an oil is processed and/or stored. For exam
the electric ?eld, whereby the impurities become so ple, the viscosity of the crude oil may become in;
associated with the large coalesced masses and
creased due to a lowered temperature and/or
are readily separable from the oil.
,
removal of light hydrocarbons, thus rendering the
It is an object of the present invention to pro
separation of impurities more dif?cult. The spe
vide improvements in method and apparatus rel
ci?c gravity is also modi?ed, thus resulting in a
ative to such an electric puri?cation process.
lower-gravity dilferential between the oil and
In view of the extensive utilization of this process for the removal of brine and other saline im
_water, with attendant, decrease in settling rates.
It is an object“ of the present invention to pro
purities> from crude oil. it is commonly termed a
vide-a process of the‘ kind described in which the
“desalting process.” It is generally agreed that
crude oil as it is produced from the well, particu
the salt or brine, whichris so frequently found 40 larly- an oil, susceptible to the above-described
associatedwith crude petroleum and which thus
stabilizing clients, is- advanced as a continuously
requires subjection of the crude oil to a desalting
.flowing stream up~t0 and through the steps of
process, becomes dispersed in the oil as the latter
removing water-dispersible impurities by'electric
is brought to the surface or otherwise subjected
coalescence with added ‘water, whereby the sta
to turbulent flow in the process of production. ~15 bilizing eifects of protracted storage are avoided.
For example, the production ?ow into the well
. It is afurther object to provide a process in
casingmay comprise admixed streams of crude
which such an, advancing stream is at all times
oil and brackish water and, in the turbulence of
maintained under superatmospheric pressure,
the ?ow to the surface and discharge from the
whereby volatile‘ constituents may be maintained
well, the brackish water or brine becomes dis :50 in theoil, .the retention of "these constituents
persed in ?ne droplets throughout the oil. These
serving to improve the'purl?cation by maintaim
droplets are eventually stabilized by the adsorp_
ing the oilin amore ?uid condition, by maintain
tion of emulsifying agents at their interface and,
ingpotential
stabilizingagents in a dissolved
as this adsorption progresses,- the droplets be
_~
~
- ,
come increasingly di?icult to treat or, coalesce - 7 state, and the like.
It is also‘ an object of the present invention
2,412,791
3
It is accordingly an object of the present in
' to provide a process in which such a stream is
vention to successively dehydrate and desalt a
continuously-advancing stream of oil maintained
under superatmospheric pressure and/ or temper
ature, more particularly when such a stream is
initially formed by a source well.
maintained at an elevated temperature or at least
withheld from prolonged exposure to low tem
perature, whereby precipitation and/or inter
facial adsorption of stabilizing agents is prevented
or
minimized.
‘
-
'
"
The steps of puri?cation, particularly the sep
Another object of the invention is to remove
free gas from the well-produced oil preparatory
aration of the electrically-coalesced masses of
dilute brine, are preferably effected in the sub
stantial absence of ebullition which is best pre
to further processing involving electrical puri?e
cation of the oil.
‘
i a
-
vented by imposing a pressure during treatment
Crude oils are normally subjected to a stabiliza
whichis'at least-as great as any minimum pres
sure t‘o'which the oil has been previously subjected, and which is greater than the vapor pres
pressure. In some instances, it is desirable to 15' sure of the oillatthe temperature of treatment.
Similarly, the imposed pressure should exceed the
stabilize the crude prior to desalting, as when
vapor. pressure of the water present in the treater.
relatively high temperatures are found desirable
It is accordingly an object of the present in
for desalting. Such stabilization, however, fre
tion process designed to remove'normally-gaseous
constituents, such as ethane, propane, butane,
etc., and to produce a crude of lowered vapor
‘ vention to provide a process for purifying a crude
quentlyvhastens the process of interfacial adsorp
tion, and I have found the puri?cation of a stabi
20 oil in which the crude oil production is main
lized crude is best accomplished directly subse
quent to stabilization without intervening stor
jeot to' superatmospher'ic pressure up to and in
tained as a continuouslyadvancing stream sub
cluding the ‘stepof separating water~dispersible
age. By combining stabilization with desalting,
impurities, said last step being carried out at
both processes are relatively high-temperature 25 a‘ superatmcspheric pressure not'less than the
previous" minimum pressure'to which said stream
I am also able to realize an economy in heat since
processes.
,
'
'
_ It is, accordingly, an object of the present in
issubjected.
‘
>
It is a further object of the present invention
vention to stabilize'a crude oil prior to‘ d'esalting
to provide a plurality of electric purifying units‘
, and preferably immediately prior thereto, as by
continuously advancing a stream of crude oil 30 arranged in parallel with ‘respect to a stream
of oil and to disperse water in such stream prior
through a-stabilizer and then through a desalter.
to its subdivision into parallel streams, whereby
In many instances, the stabilization prior to
a better and more uniform operation of severa
units may be obtained._'
I >
1
desalting need not be complete, whereby a por
tion of the volatile constituents may be retained
It is a further object to provide an automatic
in the oil during clesalting, the stabilization being 35
control for the removal of water from said units,
completed subsequent to the desalting.
whereby similar interiacial levels
be main
It is, accordingly, an object of the present in
tained in’ the several" units and whereby but one
vention to provide a process for removing salt and
control mechanism is needed for the plurality
similar impurities from petroleum in which the
steps incident to the salt removal are preceded, 40 of units.
It is also an object of the present invention
and in some instances followed, by the removal
to provide a pro-portioning control for the dis
of volatile constituents from the oil.
per'sal of water in the ?owing oil stream and to
It is a further object of the present invention
provide a means for controlling the rate of ?ow
to ‘provide a process of the kind described in
of oil‘ to the purifying units in response'to the
which the water-dispersible impurities are re
production of crude oil, more particularly in re
moved prior to the removal of all of the volatile
sponse to the level of said oil in ‘a surge tank.
constituentswhich'it is required to remove for
full stabilization of the crude.
‘ It is a further object of the present invention
'
to provide a pressure-responsive control for re
works best on oils of low water content. If the 50 moving puri?ed oil from the purifying units.
~Still further objects and aspects of the inven
oil 'produced’by the well contains but little water,
tion will become apparent in the following dis-~
for‘example not more than a'few per cent, it may
cussion of the drawings in which:
be desalted directly. Otherwise, the oil is best
Figure 1 is a schematic representation of ap
subjected to a dehydration treatment prior to de
salting in order to remove at least a portion of 55 paratus and flow lines suitable for carrying out
one embodiment of my invention; and
the aqueous brine in order to produce an oil or“
Figure‘2 is a cross-sectional‘ view of an elec
relatively low water content 'for subjection to
tric‘ treater adapted to coalesce and remove the
the'desalting' step‘. I ?nd that the steps of puri
dispersed phase from the synthetic ‘emulsion as
?cation are most effectively practiced onv a freshly
The electric puri?cation process of Eddy, supra,
dehydrated oil, possibly 'due to the fact that the 60
effect of‘ the chemical‘ or electric ?eld‘ employed
in dehydration persists for some time'and makes
the residual brine droplets more readily coalesci
ble with the added water.‘
' "It is an object of the present invention to de
hydrate and desalt successively a continuously
advancing stream of, crude oil, more particularly
, a stream having an uninterrupted flow from a
.produced in this process. '
‘ >
"
' ‘Referring more particularly to Figure l, a well
casing Iii‘ penetrates to oil-producing sands H
‘and provides a passageway for the crude oil, usual
ly coinmingled with more or less brine, to reach
65 the surface.
A ?owing pressure well' is indi- V
cated in the ‘drawings, it being understood that '
other types of production, e. g., pumping, are
likewise suitable in connection with the prac
By maintaining an advancing stream of oil
‘ ' ticeof the present process. The cil‘reaches the
70 ~surface at- a"press_ure '- dependent upon forma
undersuperatmospheric pressure, it may be very
advantageously subjected to successive dehydrae
in some instances, this pressure may be quite
source-well or a group oflwells,
_
r
_
tion and puri?cation steps, and such a, stream is
preferably maintained at superatmospheric tem
perature.
»
'
‘
tion llpressureand the depth oi‘the well, and,
high‘, for example, 2900 lbs/sq. in., or more. This
oil is transferred by means of a pipe l2 to a
75 choke valve l3 where the pressure is reduced‘ to
2,412,791
5
some suitable value, for example, about 400 lbs/sq.
in. From the choke valve I3, the mixture of gas
and crude oil enters a gas separator I4 from
whence high pressure gas is withdrawn by means
of a line I5, the liquid constituents or crude oil
collecting in the bottom of the separator I4 and
being withdrawn through a line It.
‘
6
tank 50 by means of lines 6| and 62, respectively.
By this means, a substantially constant level is
maintained in the tank ElLthe discharge of‘pump
v56 through line 5‘! being substantially equal to
the crude input in the tank 50 apart from the
slight decrease in volume due to withdrawal of‘
water and/ or vaporous constituents.
If desired, the crude may be further heated
A stream of relatively fresh water is introduced
during its passage along pipe I6 by means of a
into the stream of oil traversing line 5?, suitably
heat interchanger IT. The pressure on the ?ow; 10 by means of a pipe 10 opening into pipe: 51 at
ing stream is further reduced by passing through
juncture ‘II. If the rate of oil flow is relatively
constant, the stream of water may likewise be
20. ‘ Gaseous constituents may be removed from
constant in quantity. Where there is consider
the ?ash tower 20 by means of a line 2| feeding
able ?uctuation in oil ?ow, however, I prefer
into a low pressure gas manifold 22. Liquid con 15 to provide automatic proportioning between the
stituents are continuously removed from the bot~
streams of oil and water, whereby the latter may
tom of ?ash tower 20 by means of a pipe 25, the
be kept within the desired limits, suitably from
?ow being preferably regulated by an automatic
10 to 20% of the‘volume of oil.
a valve I8 whence the oil is led into a ?ash tower
valve 26 responsive to a float control 2'! asso
The drawings disclose a suitable means for
ciated with the tower 20 and adapted to open 20 automatically proportioning the two streams.
and close valve 20 in accordance with the liquid
Relatively fresh water derived from any suit'-‘
level in the flash tower 20.
‘
able source is‘ brought by means of a pipe ‘I2 to
If desired, the crude ?owing through the line
the suction of a centrifugal pump 13, the dis
25 may be passed through a meter 30 and may
charge of which into line '50 is controlled by
be admixed with oil ?owing in a manifold 3| 25 means of an automatic valve 14. A ?xed ori?ce
adapted to receive crude similarly produced from
80 is provided in line 51 to produce a pressure
other wells.
drop proportional to the square of the rate of
Further provision for modifying the temper
?ow of oil, and another ori?ce SI is positioned
ature of the crude ?owing through the line 25 is
in line 10 to produce the pressure drop propor
afforded by means of an interchanger 35. If this 80 tional to the square of the rate of ?ow of water.
crude contains substantial water, provision is
These differential pressures, that is, the pressures
made for the dehydration, or at least partial re
above and downstream from the respective ori
moval, of the emulsi?ed water from the crude.
fices, are ‘transmitted by means of ‘lines 82, 03,
If it is desired to dehydrate the crude chemi
84, and 85 to a control device 90 having a linkage
cally, a proportioned small stream of emulsion 35 means 9! to valve 14 and adapted to open said
breaking chemical may be supplied from a tank 35
valve when the pressure drop across the ori?ce‘
and introduced into the line 25 by means of a
8| is reduced below a predetermined ratio to the
valved line 31.
pressure drop across ori?ce 80 and to move the
valve 14 toward a closing position when the pres
If desired. the oil may be otherwise conditioned
for puri?cation, for example by means of electric 40 sure drop across the ori?ce 8| exceeds the pre
treatment. Various types of electrical dehydra
determined ratio. The control device 90 is indi
tors are available and, in the drawings, only a
cated only schematically since various devices well
very schematic representation of an electrical de
adapted to perform the desired functions are
hydrator is shown. Such a dehydrator comprises
known to the art.
‘
an outer shell 40, an inner electrode 4!, and a 45
Another modi?cation which is very advanta
transformer 42 supplying high potential alternat~
geous in certain instances when it is not desired
ing current to the inner electrode through an
to use the ori?ce plates and associated equipment
insulating bushing 43. The wet oil traversing
is to provide a linkage means, schematically indi
line 25 may be diverted by closing a valve 44 and
cated by dotted lines 05,‘ between valve ‘I4 and
opening a valve 55 into a line 45 serving to intro 50 linkage means 59 which serves to actuate the
duce the wet oil into the space between the inner
throttle valve 58 on the discharge of the oil pump
electrode 4! and the outer shell 40. If desired,
56. In this manner, the oil discharged from
dry oil may also be supplied to the treating space
pump 56 and the water discharged from pump
p by pumping through a valved line 41. The elec
‘I3 are simultaneously controlled in response to
trically-treated mixture is re-introduced into line 55 the oil level in tank 50.‘
25 by means of a transfer pipe 48 from which it
The water introduced into the flowing oil
?ows into a horizontally-positioned tank 50 in
stream at juncture ‘II’ is, in most instances, at
which the forward velocity of the advancing
least partially dispersed in the oil by the turbu
stream is su?iciently reduced to permit settling
lence of the ?owing stream, but to obtain the
of water from the treated mixture. This water 60 desired‘ degree of dispersion,‘ the commingled
may be withdrawn through a valve draw-off 1ine
stream is best subjected to a controlled agitation
iii. If desired, ‘further vapors'may be withdrawn
and shearing action, as by passage through a
from the oil in the tank 50 and passed to the
Weight-loaded valve I00. The dispersion formed
manifold 22 by means of the valved line 52.
in the valve I00 is passed into a header I0| where
The dehydrated oil is removed from tank ‘50 65 it is split into three streams which are passed by
by means of a pipe 55 connected to the suction of
means of lines I02, I03, and I04 into electric
a centrifugal pump 55. The discharge of the
,treaters I05, I06, and I01, respectively.’ In these
pump 55 is passed into a line 51, the flow through
treaters, the emulsion 'is subjected to-the action
which is controlled by means of an automatic
of an electric ?eld‘by means which will become
valve 58. The valve 58 is operatively connected 70 more clear in subsequent discussion of Figure 2,
by a mechanical; hydraulic, pneumatic, or elec
and the treated mixture is permitted to settle
trical means, or a linkage means, schematically
into, a lower body of water and an upper body of
indicated by numera1 59, to a ?oat (not shown)
relatively dry oil having a salt content below a
in ?oat housing 60 which is in free communica
specified value. The three treaters I05, I05,’ and
tion with the upper and lower portions of the 0 MT are preferably similarly constructed and
2,412,791?
.
8
chanically' and‘ electrically. connected therewith.
mounted at the same level so that the watercr
fluent lines. may be manifolded, thereby main;
taining. the interfacial level in each treater atv
is: a series of concentric rings I56 coaxial with
the'treater shell. Asimilar series of concentric
approximately the same height. In the form
shown in the drawings, a water manifold H0 is‘
shown which is in open communication with the
rings I51'is mounted on the top of cross bar I55.
The rings I56form a part of an electrode struc
lower portions of treaters I05, I 06, and I01 by
means of pipes III, H2, and II3, respectively.
One of the treaters, namely," treater I05, is‘pro
ries of rings I51 forms a part of an electrode
structure, designated generally as I6I. 'Also sus
pended from-the head plate I52>by means of an
insulator I65 is an electrode structure I66 co-'
operating with electrode structure I 60 to form an‘
upper treating space I61 and an electrode struc-r
ture I68 cooperating with the lower‘ electrode‘
structure I6I to form a lower treating space‘ I69.‘
videdwith a float chamber II5 openly communi—
eating. with the upper oil body by means of a
pipe IIB and with the lower water body by any
suitable means, typically by means of a pipe I I1.
As will presently be clear in the discussion of
Figure 2, this chamber houses a ?oat adapted to
follow the interfacial level between the oil and
water in the float chamber which corresponds to.
the interfacial level in treater I05. This float is
operatively connected to a valve I20 in manifold
IIO which serves to control the rate of discharge
of water from the manifold, The interfacial level
in treater I05 may thus be maintained substan
ture, designated generally as I60, and the se-'
L High potential alternating current is supplied by‘ '
means of transformers I10 and HI connected
in series with a ground I12 therebetween.
I60 and I6I by means of an insulated lead I14‘,
and the high potential terminal of'transformer;
I1I is electrically connected by means of insu
lated lead I15 to the electrode structures I66 and
tially uniform and at‘the desired height, and, be
cause of the manifold connections, the interfacial
levels in the other treaters are likewise main
tained at the same desired height.
The
high potential terminalof the transformer I10 isv
electrically connected‘ with electrode structures‘
I68.
.
I
The incoming emulsion flows through’ the pipe
I I02 which continues on into the interior of the
treater to rise vertically in a centrally-positionedv
pipe I30 terminating in a discharge nozzle I3I
positioned in the lower treating space I69 and
adapted to discharge the incoming emulsion ra¢
dially outward in a substantially horizontal plane
The automatic discharge or bleeding of the
water to maintain uniform interfacial levels is
accomplished irrespectiveof what the absolute
pressure in the treaters may be. I may, accord
ingly, provide a pressure-responsive control for
discharging the oil from the treater, whereby the
pressure therein may be maintained at any de
throughout the treating space I59:
'
In the electric ?eld, the droplets of the added»
sired value. For this'purpose, I withdraw oil from
water and droplets of brine or other suspended’
the upper portion of treaters I05, I06, and Hi1 :; ; impurities are coalesced to masses of sufficient‘
size to settle out from the oil andform- a body of "
by means of pipes I25, I26, and I21 which open
into the oil manifold I30 leading to the suction
of pump I3I. An automatically controlled valve
I32 is placed on the discharge line I33 of pump
I3I, the opening of which is made responsive to
the pressure in manifold I30‘by suitable pressure~
sensitive means I34 so arranged that, when the
pressure in manifold I30 exceeds the desired
pressure, valve I32 is adjusted to a greater open-‘
ing whereby the oil is'more rapidly removed from
the treating system and the pressure is reduced.
It will be» clear that the opposite reaction will
water or dilute brine E85 having an upper bound-7
ary or interface Hi6 separating it from a body of oil I81.
iii
-
'
Further electric treatment is also provided by
the upper treating space 561 through which the.
oil may pass as it rises or through which recycle;
currents may be set up due to the aspiratingef»
feet of the discharge nozzle 53!, and also by an.
auxiliary treating. field which is setup between
the charged electrode, structure iEI and the body
of water I85, the latter, together with the treater
occur to correct a- pressure which is below the
shell, being grounded by means of. the ground
desired operating pressure.
If it is, desired to further stabilize the oil sub
sequent to its desalting or puri?cation, a valve
I40 in 1ineVI33 may be closed and the oil passed
by means-of a pipe MI through a heat inter
changer I42 into a stabilization tower I43 from
which the undesired highly volatile constituents
may be removed by means of a line I44, the sta
bilized crude being withdrawn through a bot
tom line I45 and returned to the continuation of
line I33 from which it may be passed to further
Iiit.
distillation and/or crackingvequipment,’or, if__ it
is desired to store the crude, it may be‘ passed
through a cooler I46.
In instances whereit is
not desired or necessary to stabilize the crude, the
~
The float housing H5 is positioned exterior to
the shell I59 at a height corresponding to the de-.
sired height of the interface E36 and, as indicated:
above, communicates by- means of pipes H6 and
I I1 with the upper body of oil I81 and the lower
‘3 body of water I85, respectively. The ?oat. I95 is
shown connected by means of mechanical linkage
I35 to valve I28 on the water manifoldline I10;
it being understood that any suitable type of.
linkage or operative connection may be estab-.
lishedbetwcen the float
the automatic. valve.
The step of dispersing water in theflowing oil.
stream at juncture
and weightdoaded valve
I36, followed by subjection of the. emulsion thus.
formed to the action of an electric ?eld» toco-a»
valve I40- may be opened, permitting the crude
going through line I33 to flow directly to further (55" lesce the added water and saline or other .dis
persible impurities to massesseparable fromihe.
processing or to storage, as through cooler I46.
oil, and separating these masses .to obtain apuri
Figure 2 is a cross section showing details of
?edoil, as in treaters W5, W5, and I57’, constia:
treater I05. The treater comprises a cylindrical
tutes the desalting or puri?cation steps of the?
shell I50. closed at the ends by, bottom and top
plates HI and I52 through which the pipes III
‘and ‘I25 communicate with the interior of the
‘ shell I50. Suspended from the. head plate I52 by
present process. The fundamentalsof thisprocé.
CrEddy- pats“
ess arediscussed at, length in the
ent, supra, and need not be elaborated? on here.
means of. insulators I53 is a cross bar I54 from
As indicated above, the present improvement in;
which depends another cross bar I55. Suspended
immediately’ below the cross bar I54'and me
discovery that'the puri?cation process works best:
such puri?cation process rests, in part, upon the‘
aha-$91
10
es freshly-produced oil which is not allowed to
'age to the degree that brine particles become
highly stabilized with adsorbed emulsifying
vapor pressure, particularly if such minimum
pressure was maintained on the crude while the
latter was at elevated temperatures approaching
agents, and that any handling of the oil, either
those used in desalting, as in the ?ash tower 20 or
freshly produced or from storage, which increases
‘ tank 50. The advancing stream is preferably
the potential degree of adsorption such as cool
maintained at all times under super-atmospheric
ing, partial vaporization, or the like, should be
pressure, but it is usually desirable to provide re-,
succeeded as rapidly as possible by- subjection of
pressuring means, such as pump 56, immediately
the oil to the puri?cation process before addition
ahead of the desalting equipment in order that the ,
a1 stabilization of-the emulsion takes place to 10 advancing oil stream may be brought to a super
any substantial degree. The-present process also
atmospheric pressure greater than that minimum
presents further bene?cial factors by providing
superatmospheric pressure to which the oil has
for the dehydration of the oil immediately‘ prior
been previously subjected.
to desalting where dehydration is necessary, by
In many instances, the oil is best treated in a
providing for retention in the oil undergoing de 15 plurality of treaters, as shown in the drawings.
salting of volatile constituents inherently favor
It is highly desirable under such circumstances
able to the process of purification, and by pro
to maintain substantially the same conditions
viding various other factors.
as regards electric treatability, ‘and the like, in
‘ The stabilization of the crude may take place
each treater, whereby uniformity of treatment
in increasing degree in gas separator l4, flash 20 may be insured and the entire process of treat
tower» 20, tank 5E, and stabilization tower I43.
ment made more or less automatic. I ?nd that
In many instances, I prefer to conserve as much
the desired uniformity is very much more readily
of the more volatile constituents as is possible in
obtainable if the water is dispersed in the oil
the crude subjected to puri?cation since I ?nd
While ?owing as a single stream, whereby identical
that they exercise a bene?cial e?ect on the ease
25 portions of the dispersions thus formed may be
of coalescence and separation of the impurities
diverted to each treater.‘ The uniformity of
and,v accordingly, in such instances only the ex
treatment is further insured by maniiolding the
tremely volatile constituents, such as the ?xed
pressure-responsive oil discharge to each treater,"
gases, methane, ethane, and the like, and alpor
whereby the same desired operating pressure may
tion of propane and/or butane willbe removed
be maintained in each treater, and also by mani
prior to the puri?cation process, the crude being
folding the water draw-01f line so that the same
eventually stabilized and the requisite quantity
interfacial level may be established in each treat
of these volatile constituents being removed in
er, this latter factor being of substantial im-'
the ?nal ‘stabilization step in tower M3 subse
quent to puri?cation.
‘
-
portance in maintaining uniform auxiliary treat
_
In some instances, however, the advantages of
substantially higher temperatures or the im
practicality of maintaining excessive pressure in
the puri?cation step may overweight the advan
tages resident in the presence of lique?ed vola
tile constituents in the oil and, in such instances,
I may provide for the prior removal of these con
stituents so that there is substantial stabilization
of the crude oil prior to puri?cation, this greater
degree of stabilization being maintained by the
use of higher temperatures or lower pressures in
ingr?elds between the lower electrodes and the
body of water in each treater.
As one example of my process, crude oil con
taining 4 to 5% of water or brine, and from 150
to 800 grams of salt per barrel, was produced un
derpressure of about 2000 lbs/sq. in. and a tem
perature of about 150° F. The pressure on this,
crude was reduced in the gas trap 14 to about
400 lbs/sq. in. and‘the separated gases were sent
to'a vapor recovery process, the ?xed gases from
45 the vapor recovery being recompressed and sent
the ?'ash tower 2B and tank ‘50. The lower vapor
pressure of the oil thus processed permits the use
of higher temperatures without the imposition of
excessive pressures during the puri?cation proc
ess. The full advantages of this method of prior
stabilization are not realized, however, unless the
stabilization and puri?cation steps are made es
sentially ?ow line and consecutive so that the
back intoythe formation to vmaintain pressure.
The pressure was further reduced in flash tower
20 to less than 100 lbs/sq. in., the oil reaching the
, surgejtank 59 at a pressure of from 20 to 50
lbs/sq. in. and a temperature of from 150 to 170°
F'., depending upon the quantity of heat supplied
through interchangers 17 and 35. A small pro
portion of an emulsion-breaking chemical was
added to the stream entering tank 5i} by means
oil may be puri?ed as soon as possible after reof line 31 and some water or brine separated in
55
moval of the volatile constituents.
tank 50. The effluent oil from tank 56 contained
With most oils, a split stabilization process will
from 1 to 3% of water or brine. The oil was re
be found to work very well, i. e., the crude is par
pressured by means of pump 56 to a pressure of
tially stabilized to reduce the vapor pressure of
from 80 to.l20 lbs./sq. in. and a similar water
the oil to be puri?ed to a satisfactory working
pressure was developed by pump T3 for injection,
range and then, after puri?cation, the oil is fur 60 the water used for this purpose being a relatively
ther stabilized to the requisite low vapor pressure.
fresh water, that is, a water containing substan
It is highly desirable that the oil subjected to
tially less saline impurities than the brine asso
the puri?cation process be maintained under
ciated with the oil. .From 10 to 20% of water
suf?cient pressure to prevent any ebullition which
was added at the juncture point ‘H and dispersed
would otherwise interfere with the process of 65 by means of the weight-loaded valve I90, a pres
separating the coalesced masses. Accordingly,
sure drop being set up across this valve of from 40
the pressure imposed on the oil during the puri
to 80 lbs/sq. in., or thereabouts. The desalters or
?cation process should exceed the vapor pressure
purifying units were normally maintained at a
of the oil and/or water at the temperature em
pressure of 45 to 50 lbs/sq. in. and the puri?ed
70
ployed, and, in general, should be equal to or
greater than any previous minimum pressure to
which the oil has been subjected. The previous
minimum pressure to which the advancing stream
of oil has been subjected is determinative of its 75
oil ?owing therefrom contained about 1% of rel
atively fresh water, the salt content of the puri
?ed oil being less than 10 grams per barrel. This
puri?ed crude was re-pressured by means of
pump l3l to a pressure of about 175 lbs/sq. in.
32611125191
“11
stabilization tower M3, the bottoms of whichrep
resented a stabilized puri?ed crude suitable for
storage or ior direct charging into the usual dis
tillation unit.
12
oil from the upper ends of said separate settling‘
zones and combining these streams to form a
combined stream 10f‘ puri?ed oil; and throttling
the combinedstream of puri?ed oil while in
and heated in interchanger M2 for ?ashing in
creasing and decreasing the throttling action in
'
response to changes in pressure of said combined’
stream and in a manner to \maintain thepr-es
surein said settling zones substantially constant.
2. A process for removing water-dispersible
The details of the above examples are illustra
tiyie rather than limiting and various modi?ca
tionsof the described embodiments may be prac
ticed without departing ‘from the essence of my
invention as-cle?ned by the scope of the appended 10 impurities from any oil, which process includesthe
steps of: continuously mixing with a stream of
claims.
said oil a stream of relatively fresh water to form
‘II-‘his application is a division of my application
a stream of arti?cial oil-continuous emulsion;
Serial No. 322,093, entitled Method and apparatus
dividing the resulting .streamoi oil-continuous
for treating oil, ?led vMarch 4, 1940,
emulsion into a plurality of separate streams;
I claim as my invention:
establishing a plurality of separate high-in
1. A process for removing water-dispersible
tensity coalescing electric ?elds in a plurality of
impurities from a stream of crude oil containing
separated settling spaces disposed approximately
same and which stream is ?owing at a non-uni
at the same level, the number of ?elds and the
form rate, which process includes the steps of:
proportioning into said ?owing stream of oil and 20 number of settling spaces corresponding to’ the 7
number of said separate streams; delivering said
mixing therewith a stream of relatively fresh
purities; dividing this resulting stream of oil
continuous emulsion into a plurality of separate
separate streams respectively to said high-in
tensity electric ?elds to coalesce the dispersed
water and bring the water-dispersible impurities
into association therewith; separating the elec
tricallyetreated constituents of each separate
water to form a stream of arti?cial oil-‘continu
ous emulsion in which droplets of said relatively
fresh water coexist with water-dispersible im
streams; establishing a plurality of separate
stream in its corresponding settling zone to pro
high-intensity coalescing electric ?elds in a plu
duce therein bodies of puri?ed oil and separated
rating the electrically-treated constituents of
stream from the throttling‘position and in a man
ner to maintain the pressure in said settling zones
water, said separated‘ water now containing in
rality of separated settling spaces disposed ap-.
proximately at the same level, the number of so large measure the water-dispersible impurities;
withdrawing streams of oil ‘from the upper ends
?elds and the number of settling spaces corre
of said settling zones and combining these
sponding to the number of said separate streams;
streams; throttling the combined stream of puri
delivering said separate streams respectively to
?ed oil while increasing and decreasing the
said high-intensity electric ?elds to coalesce the
dispersed water and bring the water-dispersible 35 throttling action in response to changes in pres
sure of said combined stream at a position up
impurities into association therewith and sepa
each separate stream in its corresponding settling
substantially constant; withdrawing streams of
water simultaneously from each of said settling
zones and combining these streams; and con
trolling the rate of; ?ow of water in the combined
stream of water in response to changes in the
zone to produce therein bodies of puri?ed oil and
water, said separated water now containing in
large measure the water-dispersible impurities;
withdrawing streams of water simultaneously
from each of said settling zones and combining
said streams; controlling the rate of flow of
total amount of separated water in only one of
said separating zones and in a manner to main
tain the total amount of separated water in this
one of said separating zones substantially
‘water in the combined stream in response to
changes in the total amount of separated water
in only one of said separating zones and in a
manner to maintain the total amount of sepa
constant.
rated water in this one of said separating zones
substantially constant; withdrawing streams of
'
50
LOGAN C. WATERMAN.
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