US2182145A - Process and apparatus for treating oil - Google Patents

Description

Dec. 5, 1939. H. c. EDDY PROCESS AND APPARATUS FOR TREATING OIL Filed Jan. 26, 1937- `l?, Sheets-Sheet l /NvE/vroR HAROLD C. EDDY HARRIS, KlEC/-ll FOSTER@ HARRIS Fwd AT TOR/vim.

Dec. 5, 1939. H. c, EDDY 2,182,145

` PRocEss AND APPARATUS FOR TREATING OIL Filed Jan. 26, 1957 2 Sheets-Sheet 2 mmwmz f /h/vvE/vrof'? 95 H ARoLD C. EDDY Y v HA RR/S, K/fcH, F05 TERa HA RR/ A T TOR/VE yq.

Patented Dec. 5, 1939 UNITED STATES I l 2,182,145 raocass Ann APPARTUS Fon.' 'rnEA'rrNG Harold C. Eddy, Los Angeles, Calif., assigner, by mesne assignments, to Petrolite Corporation, Ltd., Wilmington, Del., a corporation of Dela- Ware Application January 26, 1937, Serial No. 122,470

20 Claims.

oils may be substantially dry, or may contain a small proportion of water dispersed therein, the

percentage of water being very small and never exceeding more than a few per cent.

By way of example, the invention is well adapted to treatment of petroleum oils or other hydrocarbons preparatory to refining or cracking in subsequent refining steps. It is in this capacity of treating petroleum oils that the invention will be particularly described, though the same principles can be applied to the treating of other oils.

In modern refinery practice, it has been found that the oil reaching the refinery as a refinery charging stock contains various impurities. The water content thereof is usually low, seldom exceeding more than a few per cent. This water, if present, will be in the form of minute droplets dispersed in the oil and various impurities may be dissolved therein, for instance acids or various salts or both. Such salts may be calcium chloride, magnesium chloride, sodium chloride, etc. In addition, this oil may contain various other impurities dissolved in, or dispersed in the oil itself, as distinct from the water. For instance, this oil may contain acids or other impurities present in the oil itself. Such acids or other impurities may simultaneously exist in the oil and in the dispersed water droplets, if present.

It is an object of the present invention to remove impurities from oils preparatory to passage through subsequent refining equipment, these impurities being of such character that they will deleteriously affect the refining equipment, as by corroding the metal portions thereof or causing depositions thereon, and may deleteriously affect the finished product or products. f

For example, the deleterious reactions resulting from the presence of acids in the oil are well known. In addition, it has now been ascertained that certain salts present in the incoming oil will react under high temperature to form acids.

For instance, salts such as calcium chloride or magnesium chloride will react with water when at a temperature of approximately 250 F or oabove to form hydrochloric acid. Such acids are very corrosive. Reflneries faced with this problem have found it necessary to neutralize the effect of the acids by addition of ammonia, a procedure involving considerable expense. In addition, salts in the incoming oil are themselves deposited on tube walls, thus clogging the passages, for example rendering ineffective the desired heat transfer in the heat exchangers. Also, such salts appear to act as catalyzing agents tending to fuse coke to the heated tubes of the subsequent refinery equipment. Use of the present invention has made possible removal of a major portion of such impurities, thus increasing the life of the refinery equipment, very materially increasing the length of time that the equipment can be operated without cleaning, and resulting in the production of superior products, often with considerably increased yields. Relative to this last factor, a 6% increase in yield has sometimes been made in using the invention. In addition, if the invention is used in conjunction with a refining system producing asphalt, the asphalt will be of extremelyhigh solubility, meeting very exacting requirements often impossible to meet if the rening equipment isused on oil not subjected to treatment in accordance with the present invention.

Crude oil produced by most wells is in the form of anemulslon, containing from 10% to 80% water, usually in the form of brine. Various methods have been proposed for reducing this water content preparatory to distillation. Dehydration methods involving gravitational separation, chemical treatment, centrifugal treatment, application of heat, filtration, or use of an electric field have been proposed. If all of the water could thus be removed, the water-dissolved salts would likewise be taken out. However, no dehydration method has been found which will commercially accomplish such complete removal. Even with the best commercial dehydration methods/available, the resulting oil may often contain several hundred grams of salt per barrel, even if the water content has beenreduced to below .5%. For instance, subjection of many such crude oils to an electric field will cause coalescence of the water masses and produce an oil having a water content which is often below 1%. v Even then, however, the salt content of this water may be so high as to seriously affect subsequent renlng equipment. Even if successive dehydrating actions are utilized on the same oil, it will be found impossible to remove all of the water. Many of the oils presenting the greatest problems are those containing onlyv a small fraction of 1% of Wateroils which have been treated by the best known methods in an attempt to remove substantially-all of the water.

'I'he present purification process can be advantageously used on such previously dehydrated 5 oils, topped oils or other oils of low water content, and will remove a major portion of the impurities, for instance the salts, acids or other impurities dissolved in the water, or the acids or other impurities associated with the oil itself. The present purification process should thus not be confused with the usual dehydration processes. It can well start where other crude oil dehy- 'lrating processes end, and may receive a dehydrated oil ofvery low water content and on which the electrical dehydrating process as at present practised has no material dehydrating effect.

It will be clear, however, that the invention is not limited by processes to which the oil has pre- 2o viously been subjected before reaching the reiinery. It will particularly be described as purifying oil containing not more than a few per cent of water and such oil may be an oil which has been previously dehydrated byany known process, or an oil naturally containing this low percentage of water, or an oil resulting from mixing or blending oils of greater water content with oils of lower water content. In other instances, the

water may be the result of previously-performed steps, whether or not they are of a dehydrating character. The oils to which this invention is particularly applicable are those oils which have a very low water content, never more than a few per cent and usually less than two per cent,

though this water content may often be materially below one-half of one per cent. The 1nvention is also applicable to the removal of oilassociated impurities regardless of whether dispersed water droplets are present.

When treating an oil containing dispersed water droplets, it is an object of the present invention to add a controlled amount of water, and to control the mixing action to produce a resulting mixture in which a major portion of the original water droplets coexist with droplets of the added water. This mixture is then subJected to the action of an electric field where coalescence of the coexisting droplets takes place. It will thus be clear that it is not the intention of the present process to use such violent mixing as would cause the added water to become combined with the original water during the mixing step. The invention thus and in other ways departs from previous proposals, and it has been found that very emcient removal of impurities can be obtained by first forming a mixture containing coexisting droplets of the original and added water, and then electrically coalescing these droplets as. distinct from attempting to combine them during the mixing step.

Best results have been obtained on most oils if such mixing is used as to form a relatively loose emulsion or mixture. For instance, this relatively loose emulsion or mixture may desirably be of such a character that a major portion of the added water will gravitationally separate, partly as emulsion and partly as free water, if

the newly formed emulsion is allowed to stand.

quiescent for two or three days, at the existing elevated temperature.

mixing can be of such a character that about 90% of the water will thus separate.' It will be found, however, that this separated water will not contain any large portion of the salts or other waterdissolved impurities which are to be removed.

In some instances, the- However, if the mixture with its coexisting droplets is subjected to the action of an electric eld, it will be found that the droplets of the added water coalesce in large measure with the droplets of the original water under the action of the electric stress. When the coalesced masses are permitted to gravitationally separate, it will be found that a major portion of the water-dissolved impurities present in the incoming oil will now be associated with the settled water.

During this gravitational separation, the treated oil will rise. When analyzed, it will usually be found to contain minute droplets of water, predominantly droplets of the added water as distinct from droplets of the original water. Its salt content; will be only a small fraction of the salt content of the incoming oil. In some instances, more than 90% of the water-dissolved impurities are removed by the process. The process is fundamentally not a dehydration process. For instance, if the incoming oil contains 1% of brine dispersed in minute droplets of a size approximating one mu, the treated oil will usually contain. about the same amount of water, sometimes slightly more and sometimes slightly less, but the water will predominantly be in the form of minute droplets of the added water. The particle size may still be in the neighborhood of one mu. Thel net eii'ect of the process is thus to replace in large measure the droplets of original water in the oil with droplets o f the added water.

The added water can usually be taken from available sources. It need not be distilled water, and various so-called fresh waters can be used. The added Water may carry certain salts in low concentration, though it is essential that the added water should be relatively fresh so as not to contain the same salts in the same concentration as present in the original water droplets. Stated in other words, the added water must be of different composition from the water droplets present in the incoming oil, by which term I have reference to a difference in chemical composition or a difference in concentration, or both. Differently stated but of the same meaning, the added water should be substantially more free of the impurities to be removed than is the water forming the original water droplets with which the impurities are associated. It will be clear that, if the added water contains the same salts as are present in the original water droplets, but in lower concentration, the net salt content will be reduced by the process because of the replacement ofthe original water droplets by the added water droplets. On the other hand, the chemical composition of the added water may be different from that of the original water droplets, even though the concentration is higher. In this instance, replacement of the original water droplets by the added water droplets may give an oil in which the total salt content, expressed in grams per barrel, may be higher than that of the incoming oil, but the process may still be of utility in that the chemicals in the added water will not deleteriously affect the subsequent process, equipment or the products produced. Usually, however, the chemical composition of the added water is 'different from that of the original water droplets, and the concentration of the chemicals therein, if any, is considerably lower than the concentration of the original brine droplets.

In many instances, it has been found desirable to successively emulsify the oil and the added water so that no single emulsifying action need be excessively large. It has often been found desirable to perform the last emulsifying step immediately prior to introduction into an electric field, for instance by using an emulsifying means for discharging directly into the field, though this direct introduction is not invariably necessary, particularly on heavy oils.

From the standpoint of removing impurities dissolved in, or dispersed in, the oil, the present invention produces quite unexpected results. Assuming a substantially dry oil with acid dissolved therein, it has been found possible to add water and mix to form a relatively loose emulsion. If this added water is settled out, or other- Wise removed before subjection to an electric eld, it will be found that very little of the acid has entered the water. However, if the mixture is formed in accordance with the present invention and is subjected to the action of an electric field to coalesce the droplets of added Water, it will be found that these coalesced masses contain a major portion of the acid. Just why this is the case is not completely understood, though my tests definitely show that the electric field has some action tending to transfer the oil-dissolved acids or other impurities to the water. So also materials dispersed in the oil, for instance solid matter such as mud or sand, are similarly removed, but here again the process does not cause these materials to become largely associated with the water in the mixing step. The action of the electric field is relied upon in this regard.

In thus removing impurities dissolved in the oil, or molecularly or colloidally dispersed there-` in, it is not essential that the oil be substantially dry. Removal of such impurities is not defeated by the presence of water droplets, though the process 4is best adapted to oils containing not more than a few per cent of water. In some instances, such dispersed water droplets may carry certain salts, or even a portion of the acid, dis# solved therein. In such instance, the process will replace most of the original water droplets with droplets of the added water, and will also remove the impurities associated with the oil itself.

It is an object of the present invention toprovide a novel method and apparatus involving the use of one or more of the above concepts in the removal of impurities from an oil.

Various other objects and advantages will be evident to those skilled in the art from the following description of a selected embodiment of the invention. For purpose of-illustration, this embodiment will be described with reference to processing a petroleum oil preparatory to subjection to cracking temperatures in a refining installation.

Referring to the drawings:

Fig 1 is a pipe-line diagram of a refining system, very diagrammatically shown, and indicates one arrangement of the invention in conjunction therewith.

Fig. 2 is a sectional view of one type of emulsifying valve.

Fig. 3 is a vertical sectional view of the preferred form of electric treater diagrammatically illustrated in Fig. 1.

Fig. 4 is an enlarged fragmentary view of the upper and intermediate electrode structure.

Fig. 5 is a sectional view of the emulsifying valve discharging into the electric field.

Fig. 6 is a sectionalvview of the washing device of the invention.

In Fig. 1 I have very diagrammatically shown one type of refining system I0 comprising a fractionating means for removing various fractions ,II, I2, I3, and I4 are shown.

The refining unit Il is shown as including a still 2I, a tower 22, a heat exchanger 23, and a condenser 24. No attempt has been made to show reflux systems or specific details of these structures, such features being well known. in the art. Sufce it to say that the incoming oil to be refined is heated in the still 2| by any suitable heating means, the vapors moving through a pipe 25 to the tower 22. Vapors are discharged from this tower through a pipe 26 which communicates with one of two passages formed by the heat exchanger 23, vthese passages being in heattransferring relationship with each other. The vapors are somewhat cooled in the heat exchanger 23, being partially condensed therein, the discharge of this one passage communicating with a pipe 21 which conducts the vapors, and any condensate formed, to a pipe means in the condenser 24. Cool Water is circulated through this condenser, being introduced through a pipe 28 and Withdrawn through a pipe 29, flowing through a passage means which is in heat-transferring relationship with the vapors. These vapors are thus condensed, and the condensate is discharged through a pipe 30.

Similarly, the refining unit I2 includes a still 3|, a tower 32, a heat exchanger 33, and va condenser 34. The vapors move to the tower 32 through a pipe 35 and to the heat exchanger 33 through a pipe 36, moving to the condenser 34 through a pipe 31. The cooling water enters this condenser through a pipe 38 and is discharged through a pipe 39, the condensate being discharged through a pipe 40.

'I'he refining unit I3 is similarly constructed with a still 4I, a tower 42, a heat exchanger 43, and a condenser 44 to which the vapors are respectively delivered by pipes 45, 46, and 41. The Water enters the condenser 44 through the pipe 43 and is discharged through a pipe 49, the condensate being discharged through a pipe 50.

Relative to the refining unit I4, this unit includes a still 5I, a tower 52, a heat exchanger 53, and a condenser 54, to which vapors are delivered through pipes 55, 56, and 51. Water enters the condenser 54 through the pipe 58 and is discharged through the pipe 59, the condensate being discharged through a pipe 60.

These rening units are only diagrammatically shown and can be considerably varied in design without departing from the spirit of the invention. Thus, in many instances the stills and towers are combined, or various structures other than shown are utilized. However, in the rening units shown, as well as in other systems, the heat exchanger and the condenser form a heat-exchange means, and it is usually desirable to preliminarily heat the incoming dehydrated oil by use of such a heat-exchange means.

In the system shown the crude oil from the well is pumped through a pipe 65 to a suitable dehydrator 66 which separates a major part of the water content, the water being discharged through a pipe 61. This dehydrator may be of any suitable type, relying upon electrical, centrifugal, or chemical action, or upon the action of heat, or it may comprise merely a settling means. The function of this dehydrator is to produce a dehydrated oil having a low water content. 'I'his dehydrated oil is pumped from the pipe line with or without intermediate storage means may be utilized to connect the dehydrator to the tank 10. It will also be clear that any other method of forming or processing the oil to be treated may be used: In the subsequent description of the apparatus it will be assumed that this oil contains about 1% of water in which 4various impurities are dissolved, and that the oil itself contains acid dissolved therein.

This oil is pumped from the tank 10 by a pump 1| and moves through a, pipe 12 to one of the passages of the heat exchanger 23. Thereafter it moves through a pipe 13 through the heat exchanger 33 and discharges into a pipe 15 in heated condition.

In the system shown a stream of hot water is introduced-at right angles into the owing stream of dehydrated oil in the pipe 15 through a pipe 16, the flow being controlled by a valve 11. A preliminary mixture is formed when these liquids are brought into contact, and this mixing action may be the first of several used to form the resulting, relatively loose emulsion or mixture. This preliminary mixture .flows through a pipe 18 where further mixing may take place due to turbulent ow.

While various sources of water may be utilized, as above mentioned, the system shown in Fig. 1 utilizes the cooling water of the condenser 34 in this capacity. This water is heated during passage through this condenser and is delivered bythe pipe 39 to an auxiliary heater 19 where additional heat may be supplied thereto fo-r control purposes. Various types of heaters may be utilized, but I have found it very satisfactory to use exhaust steam for further heating water in the heater'19. This steam may be introduced through a pipe 80 connected to a suitable coil, the condensate being discharged through a pipe 8|. On the other hand, the steam may be introduced directly intov the Water if desired.

The heated water moves from the auxiliary heater 19 through apipe 82 to a pump 83 which develops s'uflicient pressure to force this hot wa` ter through the pipe 16 and into the flowing stream of dehydrated oil in the pipe 15.

Various means may be utilized for further mixing or emulsifying the preliminary mixture moving through the pipe 18. An emulsiiler is indicated by the numeral 85 as receiving this preliminary mixture and discharging same in emulsied condition into a pipe 86 leading to the electric treater 81. Such an emulsiiier may comprise any properly designed 'emulsifying device which forms an emulsion of the desired character by mechanical mixing, friction, centrifugal force, etc. One type of emulsiiler which I have found to be very simple and eiective is illustrated in Fig. 2 and comprises a weighted valve 88, a stem 89 of which is moved downward by a linkage including an arm 90 on which is adjustably positioned a weight 9|. The position of this weight on the arm 90 controls the pressure diilerential on opposite sides of the valve and controls the size of a passage 92 between a seat 93 and a valve member 94. It thus controls the emulsifying tendency.

As an auxiliary emulsiiier I have disclosed a pump 95 capable of withdrawing the preliminarily mixed liquid from the pipe 18 through a pipe 96 as controlled by a valve 91. This pump may be of any type serving to form the desired type of mixture, for instance, a properly designed and properly controlled centrifugal pump capable of forming the desired type of mixture without in itself causing a major portion of the original water droplets to coalesce with the added water during the pump-induced mixing action. The discharge of the pump 95 may be returned through a pipe 98 as controlled by a valve 99 to the pipe 18 ahead of the emulsier 85'. In this instance further mixing will take place in the emulsifler 85.y However, if this further mixing is not desired, the pump 95 may discharge into the pipe 86 through a pipe |00, the ow being controlled by a valve 0|. In some instances the pump 95 can be utilized for emulsifying purposes exclusive of the emulsier 85, in which event a valve |02`in the pipe 86 is closed. However, in most oils a pump-induced mixing action is not as desirable as the other mixing actions described. In other instances the emulsier 85 can be used to the exclusion of the pump 95 by opening the valve |02 and closing the valves 91, 99, and |0|. In other instances these emulsifying means may be used in conjunction with each other by closing a valve |83 in the pipe 18, the valves 91, 99, and |02 being open, the

valve 0| being closed.

In some instances the system will .work particularly well if the mixture owing through the pipe 18 is divided into two streams, one flowing through the emulsiiier 85 and the other flowing through the pipes 98 and |00 to by-pass the emulsiiier, joining with the stream delivered from this emulsifier at a point therebeyond. For instance, the valves 99 and |0I may be adjusted to control the amount of mixture which by-passes the emulsier. That portion of the stream which moves through the emulsifier will be more intimately mixed, and the by-passed stream will mix therewith when injected thereinto. The size of the added water droplets in the resulting mixture can thus be varied, for the droplets in the bypassed stream may be of an average size larger than those in the stream moving through lthe emulsiiier 85.

It is often desirable to mix the dehydrated oil and the added water in steps rather than completely mixing in a single device. This permits a gradual formation of the mixture which appears to be desirable in many instances, as distinct from a single and more violent mixing action. The emulsifier 85 and the pump 95 may serve to successively emulsify, as can also the pipes 18 and 86 if they are of small enough diameter to cause considerable turbulence and consequent mixing therein. In addition, it has-been found that in some instances better results can be obtained by further mixing immediately prior to injection into the electric eld. For this purpose the pipe 86 may be connected to an emulsifying distributor means |05 disposed in the electric treater 81 and best shown in Figs. 3 and 5.

Referring to Fig. 5, it will be noted that the pipe 86 carries a primarymember |06 which cooperates with a secondary member |01 in forming an annular discharge passage |08. Further mixing takes place as the liquids move through this annular discharge passage. It is often possible to movably mount the secondary member |01, resiliently moving it toward the primary member |06 so that the size of the annular discharge passage |08 is dependent upon the quantity of the mixture moving through the pipe 86. In accomplishing this result the secondary member |01 may be provided with a pin |08a guided in a spider |09 and carrying a spacer l0 at its lower end. A compression spring is disposed between the spider |09 and the spacer ||0 and serves to resiliently move the secondary member |01 downward. When no liquid is moving through the pipe 86, the members |06 and |01 will be in contact, but as soon as a flow is established the pressure will force the secondary member |01 upward a slight distance to open the annular discharge passage |08 in degree proportional `to the quantity of liquid'to be discharged.

'Ihe details of one type of treater 01 which I have found particularly advantageous in the process are best shown in Fig. 3. Referring tov this figure, this treater 81 provides a tank ||5 including a top member ||6 and abottom member ||1, this tank being grounded as indicated by the numeral H8.

Suspended from insulators ||9 is a live electrode means shown as including an upper live electrode |20 and a lower live electrode |2|, the latter being supported from and electrically connected to the upper live electrode |20 by rods |22.

Suspended from an insulator |24 and positioned between the upper and lower live electrodes |20 and |2| is an intermediate live electrode structure |25 respectively cooperating with the electrodes |20 and |2| in providing an upper treating space |26 and a lower treating space |21. I prefer to form the intermediate electrode structure |25 of two electrodes |28 and |29 connected by a support |30.

'I'he electrodes |20, |2|, |26, and |29 are preferably formed of interstitial character. A form of construction which I have found particularly desirable is illustrated in Figs. 3 and 4. Referring to the electrode |20, this electrode is shown as including a plurality of inner and outer rings |32 and |33 between. which extend rods or pipes |34. Pins |36 depend therefrom and carry a plurality of concentric rings |31 each of which provides a lower edge |38 adjacent which the electric field is very concentrated.

The electrode |28 is similarly formed with rods or pipes |40 extending outward from a support |4| and carrying upward-extending pins which in turn mount a plurality of concentric rings |43. The rings |43 are preferably disaligned from the rings |31 so that the most intense portion of any electric field established in the treating space |26-is inclined as indicated by dotted lines |44 in Fig. 4. Such an edge-to-edge field is very effective.

The electrode |29 is formed similar to the electrode |20 and provides downward-extending rings |50. Similarly, the electrode |2| is formed similar to the electrode |28'and provides upwardextending rings |5| so that a field is established in the treating space |21 similar to that previously described in the treating space |26. I have found it preferable to form the electrodes |2| and |23 of smaller diameter than the electrodes |20 and |20.

This type of electrode structure presents a minimum impedance to gravitational separation in the tank ||5, the rings and the supporting means therefor covering only a small fraction of the total cross-sectional area of the tank. Further, the interstitial nature of these electrodes permits free communication between the electric fields and facilitates rapid removal of coalesced wate'r masses therefrom.

Various means may be utilized for energizing the electrodes to establish electric fields in the treating spaces |26 `and |21. In the construction illustrated all of these electrodes are live,

relation.

the only grounded portions being the tank and the emulsifying distributor means |05, the latter discharging directly into the treating space |21 to move the emulsion outward therein and successively through the edge-to-edge fields. By proper design of the electrical system, the po-A tential between the intermediate electrode structure |25 and the electrodes |20 vor |2| can be made much higher than the potential between any of the live electrodes and ground. In Fig. 3 such a system is shown as including two transformers |60 and |6| connected in additive In this connection one terminal of each secondary winding is grounded as indicated by the numeral |62, the high tension terminal of the transformer |6| being connected by a conductor |63 to the intermediate electrode structure |25, and the high tension terminal of the transformer |60 is connected by a conductor |64 to the upper and lower live electrodes |20 and |2|. Suitable switches and control means limiting the current to the primaries of these transformers may be utilized, such means being well known in the art of electric dehydration of emulsions.

Assuming, for instance, that each transformer develops a potential of 12,000 volts, the potential across the upper treating space |26 will be 24,000 volts, as will also the potential across the lower treating space |21. However, the potential between the emulsifying distributor means |05 and the electrode |29, or the electrode |2|, will be only 12,000 volts.A Use of such a system tends to prevent short-circuiting to the emulsifying distributor means |05 and also permits introduction of the resulting mixture directly into a eld of vhigh voltage. I believe it to be new to utilize upper and lower live electrodes with an intermediate live electrode in this capacity, though various other electrode systems can be utilized without departing from the spirit of the present invention as applied to the removal of foreign matter from oils.

The action of the electric fields is to bring into contact and thus coalesce in large measure the co-existing original and added water particles of the newly formed mixture into masses of sufflcient size to gravitate from the oil. Thus, after the treater has been in operation for a period, the upper end of the tank ||5 will contain the treated oil and the lower end of the tank will contain a body of separated water. These bodies will separate at a rather definite surface or level indicated in Fig. 3 by the numeral |10. It is desirable to rather denitely control this level to prevent grounding of the electrode |2|. In this connection, it will be apparent that an electric field will be established in an auxiliary treating space |1| between the lower live electrode |2|`and the body of water in the bottom of the tank ||5. If the level |10 is carried 'too high, this auxiliary eld may short out. However, with proper control of the level |10, this auxiliary field can be utilized to further treat the settling water particles and can be used to break an inverse-phase or reverse-phase'emulsion, as will be hereinafter ldescribed.

To control the water level in the tank ||5, I have shown an automatic system including a pipe |15 communicating with the upper part of the tank ||5 and a pipe |16 communicating with a water draw-oil pipe |11 which opens on the lower end of the tank H5. I'he pipes |15 and |16 communicate with a float chamber |13 in which the oil and water are in surface contact at a levelcorresponding to the level |10. A properly balanced float |19 is disposed in the chamber |18, being so formed as to oat in water and sink in oil. The position of this oat will thus change in response to changes in the level |10. This float may be pivoted on a pin |80 connected to an arm I 8| which is connected to a valve |82 in the pipe |11 by any suitable means such as a link |83 connected to an arm |84 of the valve |82 pivoted at |85 and operatively connected to the stem |86 of this valve. If the water level rises, the valve |82 will thus be opened a further distance to drain additional quantities of water from the tank ||5 and thus maintain the water level constant. Various other systems for controlling the position of this water level may be utilized without departing from the spirit of the present invention.

I have found that in some instances there is a tendency for the settling coalesced water masses to carry downward therewith particles of oil. This is not conducive to a clean separation, and, if allowed to continue, will result in contaminated water bleeds, the oil being carried downward into v the body of water in the bottom of the tank. If this action takes place and is detrimental, it can be corrected by moving masses of water upward through the body of water to sweep out any oil present and prevent downward movement of oil toward the water draw-off pipe |11.

A system wh'ich I have found very satisfactory in this regard is illustrated in Figs. 3 and 6. Disposed above and in protecting relationship with the water draw-olf pipe |11, I illustrate a multiorifice discharge head |90. This head may be formed of a cap |92, best shown in Fig. 6, and provided with a plurality of orifices |93 formed to direct water upward and outward. Certain o1' these orifices may be vertically disposed, though best results are obtained if other orifices are angularly disposed relative to the horizontal. A plate |95 closes the cap |92 and receives a pipe |96 to which water is delivered by a pipe |91. The incoming water is thus sprayed into the body of water in the lower end of the tank ||5 to form water masses which slowly rise toward the surface |10 due to the inclined nature of the orices or to thermal action or to a diierence in density if the incoming water is fresh, or t0 various combinations of these factors. A desirable thermal eifect is obtained by delivering to the pipe |91 water which is slightly hotter than the water inthe bottom of the tank ||5. This may be accomplished by connecting the pipe |91 to the pipe 16, and thus to the discharge of the pump 83, the flow being controlled by a valve |99.

The action of these rising water masses is to sweep from the body of water in the bottom of the tank ||5 any oil or reverse-phase emulsion. The upward movement of the newly added water particles moves such a reverse-phase emulsion toward the surface 10 and thence into the auxiliary electric eld |1| in which such an emulsion is separated. 'I'his expedient of introducing Water masses into the body of water in an electric treater is particularly valuable when treating certain oils, and permits larger quantities of Water to be added to the incoming oil in the performance of the process herein disclosed in detail.

In some instances it is possible to accelerate the separation of the particles of oil in such a mass of Water by adding to the Water flowing through the pipe |91 a small quantity of a chemical deemulsifying agent. Various types of such agents are known. Particularly desirable results have been obtained by the use of a chemical de-emulsifying agent which is both oil soluble and water soluble though other rchemical de-emulsifying agents can be used.

The treated oil moves from the upper end of the tank ||5 through a pipe 200, the flow being controlled by a valve 20| which in turn assists in controlling the pressure in the tank ||5. I'his treated oil may be moved directly into the rening system, though I find it preferable to discharge same into a treated-oil storage tank 202 where some additional separation of the water will take place.

A pump 203 is shown for withdrawing the treated oil from the tank 202 and moving same through a pipe 204 to the heat exchanger 53. Additional heat is supplied at this point and the treated oil moves through a pipe 205 to the heat exchanger 53. Being thus additionally heated, the treated oil moves through the pipe 6| to the still 2|. Here certain lighter vfractions are removed, as previously described, the topped oil moving through a pipe 201 to the still 3|. This sequence is continued to remove successive fractions, and, in the embodiment shown, the heavier constituents of the oil finally move from the still 5| through a pipe 208 to a cracker 2|0. Various of such crackers are known in the art and need not be speciiically described. Usually, however, these crackers include a plurality of tubes which are externally heated and which conduct the heavier constituents of the oil. The heat supplied in the cracker 2|0 causesl cracking and vaporization, 'the vapors moving through a, pipe 2|| and being condensed in a condenser 2|2, the residue being discharged from the cracker 2| 0 through a pipe 2|5.

By way of example, and without limiting myself thereto, operating conditions and results with a typical oil will be given. The oil in this example contained only from .4% to .5% of water, but still contained from 100 to 250 grams of water-:dissolved salts per barrel, these salts being predominately magnesium chloride and calcium chloride. By use of this process, it was found possible to consistently lower the salt content to 10 grams per barrel or less, and in some instances to 5 grams per barrel. This oil was treated at a rate of 2250 barrels per day per treater, and the average water content of the treated oil was in this instance reduced to ,2%.

In this example, the incoming oil moved through the heat exchangers 23 and 33 and was raised to a temperature from to 150 F. 'Ihe water used in this example was withdrawn from several of the condensers 24, 34, 44 and 54, an expedient which can be utilized if desired, and was at a temperature of about 120 F., this temperature being increased in the heater 19 to a value of about 160 F., a temperature which, in this example,- was somewhat above the temperature of the oil in the pipe 15. The introduction of this water into the pipe 15 thus served to additionally heat the oil, and the temperature of the preliminary mixture entering the emulsifying means was approximately F.

In this example, the available water supply was fresh water which incidentally contained various salts in very small quantities. This was a typical water such as is used for drinking purposes and such as can be obtained from lak-es, rivers, domestic water supplies, etc. Percentages of water between 10% and 50% could be used with success, though approximately 20% of water gave 2,182,145 `best results in forming the resulting mixture.

Operation was slightly improved by jetting additional water upward in the body of water in the tank H5, the water thus introduced being at a temperature slightly higher than that of the water in the tank. However, the system operated entirely successfully without the addition of water at this point, though it was found that clearer water bleeds could be obtained by such injection.

'I'he degree of mixing was so controlled as to produce a relatively unstable mixture or emulsion in which a major portion of the .original water droplets coexisted with the droplets of the water at the time of introduction into the electric field. In this example, the mixture was not relatively stable, and substantially 90% of the water would gravitationally separate from the oil as free or emulsifled water if the mixture was allowed to stand quiescent for two or three days at its temperature of about 150 F. It was found that this type of emulsion could be produced by properly controlling one or more of the emulsifying means above-mentioned, but the best results were obtained when using a valve, such as shown in Fig. 2, in conjunction with the emulsifying distributor means |05.

It was found desirable in this example to carry a slight pressure in the electric treater 81. A pressure of 20 lbs/sq. in, gave very satisfactory results. The pressure drop across the emulsifying distributor means |05 was approximately 12 lbs/sq. in., and the pressure drop across the emulsifying valve, such as shown in Fig. 2, was approximately 10 lbs./sq. in. Additional drops in pressure due to pipe friction brought the pressure in the pipe 15 to approximately 50 lbs/sq. in.

The voltages mentioned above were used, and the water content of the treated oil was approximately .2%. Microscopic examination of the oil discharged from the upper end of the treater 81 showed the presence of minute water droplets of a size in the neighborhood of one mu, approximately the size of the original droplets present in the incoming oil. The oil withdrawn from the electric treater contained substantially -none of the original water droplets present in the incoming oil, those water droplets present in the treated oil being predominantly droplets of the added water. On the other hand, the water drawn from the treater was of a composite composition, containing the salts present both in the original water droplets and in the added water.

Prior to installation of the invention in this exemplary refinery, it was customary to treat this oil with large quantities of ammonia. By processing the oil as herein-disclosed before fractional distillation thereof, it was found possible to effect a saving of approximately $300.00 per month in the amount of ammonia utilized. In addition, if the refinery equipment was utilized on oil not treated by the process herein-described. it was found that even ii considerable quantities of ammonia. were utilized, the equipment could operate for only limited periods without clogging. For instance, it was necessary to clean the cracker every six or ten days and the stills every fifteen or twenty days. When processing th'e oil by the method herein-disclosed, it was found that the subsequent equipment could be operated continuously for thirty-five days or more before clogging of the cracker or other equipment took place to any detrimental extent. In addition, corrosion diillculties were minimized and better products produced. As illustrative of the latter factor, this refinery was unable to produce asphalt of the desired solubility prior to use of the present invention. Thereafter, the solubility of the asphalt was raised to 99.9%.

In general, it will be found that the process '5 operates best if various factors are controlled to bring them within the following concepts. It will be clear, however, that the following statements are to be applied to ranges, conditions or values which give best results, and that these will 10 varywith different oils, and that,` in some instances, they do not represent fixed limits but can be departed from in some degree if optimum results are not necessary. The following suggested values apply particularly to an oil containing water in which the impurities are dissolved:

As to the added water, various waters can be used, so long as this water is of different composition from that of the original water droplets, within the meaning of this term as hereinbeforedened. Based on the volume of the oil, various percentages can be used. The lower limit appears to be about 8%, and the upper limit appears to be determined only by the tendency to form inverse-phase emulsions in such amount as not to be readily treatable by the electric field. In

v some instances, 50% or somewhat more can be utilized. At the higher percentages, it is preferable to use the water spray in the bottom of the treater. With most oil, optimum results have been obtained between 15% and 25%, approximately 20% appearing to give the best results. The temperature of the water at the time it is introduced into the oil is not particularly critical and depends in part upon the temperature of the oil. In some instances, water can be introduced at room temperature, though better results have been obtained by use of water. at elevated temperatures. The usual temperature range is from 100 F. to 210 F. but higher temperatures can be used, up tothe boiling point at the pressure utilized.

As to the incoming oil, various oils can be successfully treated, so long as they do not shortcircuit the electrodes. The water present therein will be dispersed in the form of relatively small droplets, though the process is not limited by the exact size of these original droplets. It is particularly effective on oils in which these original water droplets cannot be separated conveniently or economically. It is not always necessary to heat the oil before injection of the added water, though heat usually improves the process. The temperature is not critical, and excellent results have been obtained with oils from 100 F. to 225 As to the resulting mixture or emulsion, the fundamental concept is to disperse droplets of the added water in the oil to coexist with the original water droplets. This can be done in various ways, and if a supplementary mixing action is used, it is very desirable that the mixing action should not be of such character as to itself cause a major portion of the original droplets to combine with the added water. The most desirable mixture is one in which a major portion of the original water droplets coexist with droplets of the added water until such time as it is subjected to the action of the electric field. Best results have been obtained from a resulting mixture in which the average size of the added water droplets is larger than the average size of the original water droplets. In addition. it is ofter. desirable to instances on certain oils without additional emulsifying means, or such a pump can be used in conjunction with the mixing action resulting from injection, or from the use of an emulsifying distributor means, or from both.

In other instances, an emulsifying valve, properly designed and properly controlled can be used, or this can be used in conjunctionwith any of the additional. emulsifying means above-mentioned. In some instances, particularly desirable Aresults have been obtained by dividing the stream of the preliminary mixture, moving a portion through a suitable emulsier and another portion in by-passing relation with this emulsier. The two streams join beyond the emulsifier and in so joining, an additional gentle mixing action is vobtained which rather uniformly distributes the droplets of the by-passed stream throughout the mixture which moves from the emulsier.

As a general rule, the desirable type of resulting mixture or emulsion requires a definitely limited mixing action. Intimate mixing, such as would result in homogenization, should be avoided. A centrifugal pump may be designed and operated to produce an emulsion departing from the desired character and is usually not the best type of emulsifying device to use, except that it will work successfully on certain selected oils if properly designed and controlled so as not too intimately to mix the oil and the added water. If a valve, such as shown in Fig. 2, is used as the emulsifying means, the desirable pressure drop thereacross will depend upon the oil being treated and upon the other emulsifying actions used, if any. In using such a valve with the water injection system shown and with the emulsifying `distributor means, a pressure drop thereacross from 3 lbs/sq. in. to 60 lbs/sq. in. has been used with success, though these limits can often be departed from.' From 5 lbs/sq. in. to 15 lbs/sq. in. is usually best in this regard.

In some instances, the mixture may desirably `be heated with or without heating the incoming oil or the water. Best temperatures of the resulting mixture when subjected to the eld are from F. to 190 F. though atmospheric tem- Deratures are sometimes effective.

As to the electric treater 81, any electric treater capable of bringing the coexisting droplets together can be used, such action being herein termed coalescence. Alternating current fields are preferred, either constantly occurring or intermittently applied, though such coalescence can take place in a uni-directional field of constant or pulsating potential. Fields resulting from the application of short electric surges to the electrodes, or application of peaked potentials to the electrodes, can also be used with success. Relatively high potentials are preferred. the potentials and type of current being commensurate with those used in the art of electrically dehydrating emulsions. In addition, various electrode structures can be used with varying degrees of heavier oils, or with mixtures having no distinct sludging tendency, it is sometimes possible to introduce the emulsion into the tank H5 at a point spaced from the main field, allowing the emulsion to subsequently gravtate or otherwise move thereinto. With such oils, introduction into the auxiliary treating space I 1| can sometimes be used. While satisfactory results can sometimes be obtained by maintaining substantially atmospheric pressure in the treater 81, better results have been obtained by maintaining therein a pressure of from 5 to 25 lbs./sq. in.

As to the treated oil moving from the upper end of the electric treater 81, the water content thereof may be slightly above or slightly below the water content of the incoming oil. Usually, the process will produce a treated oil containing about the same amount of water as was present in the incoming oil. The composition of this water in the treated oil will depend largely upon the composition of the added water. In view of the fact that the process acts in eiect to replace droplets of the original water with droplets of the added Water, it Will be clear that the salt content of the outowing oil is largely within the control of the operator. If it should be desired to even increase the total salt content, by replacing deleterious salts with other salts having no detrimental action on the subsequent equipment. this can be readily accomplished. On the other hand, it is possible to remove a large portion of the salts in the original water droplets, and subsequently re-run the treated oil through the system, adding salt water, and produce a salty oil, thus indicating that the replacement action mentioned above is reversible.

Temporary storage of the treated oil in tank 202 `is not essential, though it will be found that some additional separation of water will take place therein, and this expedient is often desirable in refinery practice.

Coming now to the general problemk of removing impurities associated with the oil, as distinct from being associated with any Water droplets which may be present, such impurities may be dissolved in, or dispersed in, the oil. Various acids dissolved in the oil and various impurities colloidally'dispersed in the oil, for instance mud and sand, are typical examples. Assuming that the incoming oil contains not. more than a few per cent of water, and that this water carries various`impurities which will be removed as above set forth, it will be clear that acids thus dissolved other impurities, such as salts, etc. Assuming that this incoming oil also contains acid dissolved in the oil and mud colloidally dispersed therein, it has been found that the process will remove substantial amounts of these impurities by'following the procedure outlined above. Just why this is the case is not distinctly understood. It has been .definitely ascertained that neither oil-dissolved acid nor the colloidally-dispersed mud will combine with the added water to any major degree during the mixing action herein contemplated, for, if the water is .separated from the resulting mixture before subjection to the electric eld, it will be found that most of these impurities remain in the oil and have not been transferred to the water. However, when the resulting mixture is subjected to the action of an electric eld, the dissolved acid and colloidallydispersed mud are transferred in large measure from the oil to the water,E and appear in the water separated in the electric treater.

So also the invention is applicable to removal of impurities dissolved in, or dispersed in, the oil, regardless of whether or not water droplets are present. For instance, it has been found possible to remove oil-dissolved acid and colloidallydispersed impurities from an oil which is substantially dry. In this instance, water is added in about the same proportions as mentioned above. One or more mixing steps, as above-defined, can be utilized, though in general it can be stated that a somewhat more violent mixing action can be utilized in this connection, so long as the resulting mixture is readily treatable by an electric eld to coalesce the droplets of the added water present therein. Here again it has been found that the oil-dissolved acid and the colloidally-dispersed impurities become associated with the added water by some action in the electric field, and not in the mixing step itself. Acids, or other impurities dissolved in, or dispersed in, an oil can thus be removed by the process..

The invention is not limited to treatment' of an oil preparatory to additional refining by fractional methods. Various other uses of the invention will be apparent to those skilled in the art. If used with a refinery system, the connections disclosed will be found of particular utility in saving heat, utilizing the water from the condenser means, and being desirable in other connections. However, the invention is applicable to various types of refining units, and need not be connected thereto in heat-transferring relationship if this is not desired.

While the process has been particularly defined with reference to a dehydrated oil, it is applicable to removing impurities from various oils under the principles outlined above, regardless of whether they have been previously treated in one way or another, and regardless of whether they are to be additionally treated by fractionation. Nor is it always essential that the oil be of lower gravity than the addedwater. If the converse is true, the principles herein-disclosed can be applied by withdrawing water from the upper end of the treater tank, and the hydrocarbon from the lower end, suitable changes in position of the insulators being made to prevent short-circuiting of the electrodes. Such conditions may be met in treating certain tars to remove impurities therefrom.

The term relatively fresh water, as used in the claims has reference, if the oil carries dispersed impurity-containing water, to a water which if it contains any of the impurities to be removed has a materially less concentration thereof than does the dispersed water, or, if the oil carries no dispersed impurity-containing water the term has reference to a water which has no more than a small concentration of the impurities to be removed.

In general, the present process comprises the treatment of a .mineral oil containing no more than a few per cent of water by mixing a relatively fresh water therewith preparatory to electric treatment. The character of mixing is important and, as previously pointed out, must be limited to a value at which the desired action will be obtained. This mixing should be of such character as to disperse the relatively fresh water eiectively throughout the oil and to form an emulsion which is in a condition to be continuously and substantially completely resolvable with the aid of an electric field into oil and water, without the accumulation of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric eld. Any such increasing accumulation of sludge would seriously interfere with the continuity of the process, which, being often connected to renery equipment, must remain on-stream for long periods of time. In addition, electric treatment well suited to the artificial emulsion or mixture should be used, and should be capable of continuously treating same so that substantially complete resolution can be obtained by subjection to an electric field and separation of the coalesced water masses.

Various other changes and modifications can be made without departing from the spirit of the present invention as defined in the appended claims.

This application is a continuation in part of my application Serial No. 66,404, filed February 29, 1936, entitled Improved process and apparatus for treating oil.

I claim as'my invention:

1. A process for treating a mineral oil contain'- ing no more than a few percent of water to remove impurities dissolved or dispersed in the oil phase or the water phase, which process includes the steps of mixing said mineral oil and a relatively fresh water, said mixing being of such a character as to form a mixture of the relatively fresh water and oil but insuiiicient to cause a'predominant portion of the impurities to become associated with said relatively fresh water; suhjecting the mixture to the action of an electric eld to coalesce the water and cause impurities to become associated therewith; and separatingthe coalesced water containing impurities from .the oil.

2. A process for treating .a mineral oil contain- 4 ing no more than a few percent of water to remove impurities dissolved or dispersed in the oil phase or in the water phase, which process includes the steps of: mixing said mineral oil and a relatively fresh water to disperse the relatively fresh water effectively throughout the oil, said mixing being of such character as to form an emulsion which is in a condition to be continuously and substantially completely resolvable with the aid of an electric eld into oil and water without the accumulation --of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric field; and substantially completely resolving said emulsion by subjecting a continuous stream of said emulsion to the action of an electric field to coalesce the dispersed water and separating the coalesced water masses from the oil, whereby said process may be maintained in continuous operation for extended periods of time.

3. A process for purifying a mineral oil refinery charging stock containing no more than a few percent of water to remove impurities dissolved or dispersed in the oil phase or in the water phase and which upon heating in the refinery equipment vwill detrimentally affect this equipment or the mixing being of such character as to form an emulsion .which is in a condition to be continuously and substantially completely resolvable with the aid of an electric field into oil and water without the accumula-tion of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric field; and substantially completely resolving said emulsion by subjecting a continuous stream of said `emulsion to the action of an electric field to coalesce the dispersed water and separating the coalesced water masses from the oil to such extent as to leave no more than a few percent of water remaining in the oil comprising the purifled refinery charging stock, whereby said process may be maintained in continuous operation for extended periods of time.

4. A process for purifying a mineral oil refinery charging stock containing no more than a few percent of water to remove impurities dissolved or dispersed in the oil phase or in the water phase and which upon heating in the refinery equipment will detrimentally affect this equipment or the -products produced, said impurities comprising saline material, which process includes the steps of mixing with a stream of said refinery charging stock a relatively fresh water to disperse the relatively fresh water effectively throughout the oil, said mixing being of such character as to form an emulsion which is in a condition to be continuously and substantially completely resolvable with the aid of an electric field into oil and Water without the accumulation of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric field and which emulsion contains droplets of said relatively fresh water coexisting with said saline material; and substantially completely resolvingsaid emulsion by subjecting a continuous stream of said emulsion vto the action of an electric field to coalesce the dispersed water and separating the coalesced Water masses from the oil to such extent as to leave no more than a few percent of Water remaining in the oil comprising the purified refinery charging stock, whereby said process may be maintained in continuous operation for extended periods of time.

5. A process for treating a mineral oil containing no more than a few percent of water to remove saline material dispersed in said mineral oil, which process includes the steps of: mixing said mineral oil and a relatively fresh water, said mixing being of such a character as to form a ymixture of the relatively fresh water and oil but insufcient tocause a predominant portion of the saline material to become associated with said relatively fresh Water; subjecting the mixture to the action of an electric field to bring the saline material and the water together and to coalesce water; and separating the coalesced water from the oil.

6. A process for treating a mineral oil containing no more than a few percent of water to remove saline material dispersed in said mineral oil, which process includes the steps of: mixing said mineral oil and a relatively fresh water to disperse the relatively fresh water effectively throughout the oil, said mixing being of such character as to form an emulsion which is in a condition to be continuously and substantially completely resolvable with the aid of an electric field into oil and water without the accumulation of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric field; and. substantially completely resolving said emulsion by sub- 'continuous operation for extended periods of time.

7. A process as defined in claim 3 including the step of heating the oil from which said coalesced masses have been separated to a temperature sufficient to remove vapors therefrom.

8. A process as defined in claim 5 including the step of producing said mineral oil containing no more than a few percent of water by treating a crude oil emulsion to coalesce and separate therefrom dispersed brine to produce an oil containing dispersed saline material, but containing no more than a few percent of water.y

9. A process as defined in claim 1 in which said coalesced Water is separated to such an extent as to leave no more than a few percent of water in the oil.

10. A process as defined in claim 2 in which said mixing is effected at least in part by bringing together at superatmospheric pressure streams respectively comprising said mineral oil and said relatively fresh Water, said superatmospheric pressure being sufficient to move the resulting stream into said electric field.

ll. A process as defined in claim l in which said coalesced water is separated from the oil in a separating zone from which the water and oil are separately withdrawn, and including the step of bringing together at superatmospheric pressure streams respectively comprising said mineral oil and said relatively fresh water, said superatmospheric pressure being sufficient to move the resulting stream into said electric field and maintain a superatmospheric pressure in said separating zone.

12. A process as defined in claim 2 in which said mixing is performed at least in part by bringing together and blending streams respectively comprising said oil and an oil containing droplets of said relatively fresh water dispersed therein to disperse the droplets of relatively fresh water throughout the resulting stream.

13. A process as dened in claim 2 in which said mixing comprises preliminarily mixing the mineral oil and the relatively fresh water, dividing the preliminarily mixed constituents into two portions, additionally mixing each portion while mixing one portion in such manner as to disperse the relatively fresh water into droplets of an average size smaller than those resulting from the additional mixing of the other portion, and blending the two portions together to form a dispersion containing interspersed droplets of the relatively fresh water derived from both portions.

14. A process as defined in claim 2 in which the mixing of the mineral oil and the relatively fresh water is performed in successive mixing steps.

15. A process as defined in claim 2 in which at least a part of the mixing is performed adjacent the point of discharge into said electric field. l 2

16. A process as defined in claim 2 in which said electric field is established in an oil environment of sufficient resistivity to permit maintenance of the field at coalescing potential when treating said emulsion, this emulsion being continuously introduced into this oil environment for treatment by said electric iield.

17. A process as defined in claim 2 in which said electric eld is established in an oil environment of a separating zone containing electrically-treated constituents undergoing gravitational separation, the lower end of said zone containing a body of water, and in which an auxiliary electric field is established at a position between said first-named field and saidv body of Water to treat electrically the water masses moving downward to said body of water.

18. A process as dened in claim 1 in which said impurities comprise salts dissolved in water droplets dispersed in the oil in amount not more than a few percent whereby said oil con-v tains dispersed brine, and in which said relatively fresh water contains some of the same salts as are present in said brine but in a concentration substantially lower than the concentration thereof in said brine.

19. A process for treating a mineral oil to remove therefrom impurities carried by small water droplets dispersed in the oil, said oil containing no more than a few percent of water, which process includes the steps of: mixing said mineral oil and a relatively fresh water, said mixing being of such character as to form a mixture of the relatively fresh water and oil but insufficient to cause a predominant portion of the impurities carried by the water droplets of the oil to become associated with said relatively fresh water and said mixing being of such character as to disperse the relatively fresh water into the oil in droplets of heterogeneous particle size and of an average size larger than the water droplets in the mineral oil to be treated; subjecting the mixture to the action of an electric field to coalesce the droplets of relatively fresh water with the droplets carrying said impurities thus causing the impurities to become associated with the coalesced water; and separating the coalesced water containing impurities from the oil.

20. A process for treating a mineral oil to remove therefrom impurities carried by small water droplets dispersed in the oil, said oil containing no more than a few percent of water, which process includes the steps of: mixing said mineral oil and a relatively fresh water to disperse the relatively fresh water effectively throughout the oil, said mixing being of such character as to form an emulsion which is in a condition to be continuously and substantially completely resolvable with the aid of an electric eld into oil and water without the accumulation of such amount of sludge comprising unresolved emulsion as would interfere with the maintenance of the electric eld; and substantially completely resolving said emulsion by subjecting a continuous stream of said emulsion to the actionv of an electric eld to coalesce the dispersed water and separating the coalesced water masses from the oil, whereby said process may be maintained in continuous operation for extended periods of time, said mixing and separatingcsteps being of such character that some of the droplets of relativelyfresh waterin said emulsion are of such size as to remain in small amount in the oil following separation of said coalesced masses therefrom.

HAROLD C. EDDY.

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