Dec- 1'7, 1946- |_. c. WATERMAN ‘ 2,412,791 _ METHOD FOR PURIFYING MINERAL OILS ‘.V Original Filed March 4, 1940 2 SheetS-Sheet'l /N VE N 702/ ~ LOGAN C. W4 TERA/IAN 0%rmw, mm,‘ m @d; mw w RM Arrow/Ex: Dec. 17, 1946. |_' Q WATERMAN 2,412,791 METHOD FOR PURIFYING MINERAL OILS Original Filed March 4, ‘1940 2 Sheets-Sheet 2 1292:. A20 /5/ - M //0 . 2N ve/vroe/ ‘B Y LOGAN C. MTERMAN HARE/.5, mach; FOSTER drHARR/J ,4 rrozovsxs 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.