US2386941A - Apparatus for desalting oil - Google Patents

Description

Oct. 116, 1945. H. c. EDDY 2,385,941

i APPARATUS FOR DESALTING OIL loriginal Filed Jan. 26, 1957 2 sheets-sheet '2 /NL/Nrol? /35 HAROLD C. EDDY HA 9ms, K/fcH, Fos me 2 HARK/s A Trae/v5 Ks.

Patented Oct. 16, 1945 APPARATUS FOR DESALTING OIL Harold C. Eddy, Los Angeles, Calif., assignor tov Petrolite Corporation, Ltd., Wilmington, Del., a l corporation of Delaware Original application January 2.6, 1937, Serial No.

Divided and this application December 1, 1939, Serial No. 307,189

6 Claims.

My invention relates to av novel method and apparatus for treating oils to remove foreign matter therefrom. Various oils can be thus puried by the process, for example petroleum oils, topped oils, fractions obtained by distillation per cent.

ing of other oils.

to form hydrochloric acid. Such acids arevery corrosive. Refneries faced with this problem have found it necessary to neutralize the eiect of the acids by addition of anunonia, a procedure involving considerable expense. In addition, salts in the incoming oil are themselves deposited on Relative to this last centrifugal processes, and, in general, any oil of relatively tube walls, thus clogging the passages, for ex- Y high resistivity capable of withstanding the ample, rendering ineffective the desired heat potentials contemplated for production of the transfer in the heat exchangers. Also, such salts electric field. Such oils may be substantially appear to act as catalyzing agents tending to fuse dry, or may contain a small proportion of water 10v coke to the heated tubes of the subsequent redispersed therein, the percentage of water being neiy equipmeilt- USG of the Present invention very small and never exceeding more than a few has made possible removal 0f a majOi portion v of such impurities, thus increasing the life of By way of example, the invention is well the refinery equipment, very materially increasadapted to treatment of petroleum oils or other ing the length of time that the equipment Cari be hydrocarbons preparatory to refining .or crackoperated without cleaning, and resulting in the ing in subsequent refining steps. It is in this production of superior products, often with concapacity of treating petroleum oils that the in- Sideiably increased yields. venon will be particularly described, though factor, a 6% increase in yield has sometimes been the same principles can lbe applied to the treatmede in using the nVentOn- In addition. if

the invention is used in conjunction with a re- In modern renery practice, it has been found lining system producing asphalt. the asphalt Will that the oil reaching the refinery as a refinery be of extremely high Solubility, meeting Very eX- charging stock contains various impurities. The acting requirements often impossible to meet if water content thereof is usually low, seldom exthe refining equipment is used on oil not subceeding more than a, few per cent, This water, jected to treatment in accordance with the presif present, will be in the form of minute droplets ent inventiondispersed in the oil and various impurities may Crude Oil produced by most Wells iS in the be dissolved therein, for instance acids or various form of an emulsion, COIltanng rOm 10% t0 salts, or both. Such salts may be calcium chlo- 80% water, usually in the form of brine.v Varride, magnesium chloride, sodium chloride, etc. iouS methods have been PrOPoSed for reducing In addition, this oil may contain various other this water content preparatory to distillation. impurities dissolved in, or dispersed in, the oil Dehydration methods involving gravitational itself, as distinct from the water. For instance, separation, chemical treatment, this oil may contain acids or other impurities treatment, application of heat, filtration, or use present in the oil itself. Such acids or other imof an electric field have been proposed. If all purities may simultaneously exist in the oil and of the water could thus be removed, the waterin the dispersed water droplets, if present. dissolved salts would likewise be taken out. How- It is an object of the present invention to reever, no dehydration method has been found move impurities from oils preparatory to passage which will commercially accomplish such comthrough subsequent refining equipment. these plete removal. Even with the best commercial impurities being of such character that they will dehydration methods available, the resulting oil deleteriously affect the refining equipment, as may often contain several hundred grams of salt by corroding the metal portions thereof or causper barrel, even if the water content has been ing depositions thereon, and may deleteriously reduced to below .5%. For instance, subjection affect the finished product or products. of many such crude oils to an electricfleld will For example. the deleterious reactions resultcause c'oalescence of the water masses and prong from the presence of acids in the oil are well duce an oil having a water content which is often knOWn- In addition. it has now been ascertained below 1%. Even then, however, the salt content that certain saltsy present in the incoming oil will of this water may be so high as to seriously afreact under high temperature t0 fOrm acids. F01' feet subsequent rening equipment, 'Even if SuciDSanCe. Salts, such as calcium chloride or magcessive dehydrating actions are utilized on the neslum chloride. will react with water when at same oil, it will be found impossible to remove al1 a temperature of approximately 250 F. or above 55 of the water. Many of the oils presenting the greatest problems are those containing only a small fraction of 1% of water-oils which have been treated by the best lmown methods in an attempt to remove substantially all of the water.

The present purification process can be advantageously used on such previously-dehydrated 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 associatedwith 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 dehydrating processes end, and may receive a de..

dissolved impurities which are to be removed.. However, if the mixture with its coexisting droplets is subjected to the action of an electric field, 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 cent of water, and such oil may be Ian oil which has been previously dehydrated by any 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, whetheror not they are of a dehydrating character. 'I'he 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 2%, though this water content may often be materially below 1/2 of 1%. The invention is also appli- .cable to theremoval of oil-associated impurities vwill 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 eillcient 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 duringthemixing 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 character that a major portion of the added water will gravitationally separate,

partly asemulsion and partly as free water, if thev newly-formed emulsion is allowed to stand quiescent for two or three days, at the existing elevated temperature. In some instances, the mixing can be of such 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 waterfound 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 1 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 1 mu. The net effect of the process is thus to replace in large measure the droplets of original water in the oil with droplets of 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, vthe 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 of the 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, maybe 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, howeverthe chemical composition of the added water is dierent from that of the original water droplets, and the concentration ofthe chemicals therein, if any, is considerably lower than the concentration of the original brine droplets.

In many instances, it has been found desir- 76 able to successively emulsify ineen and the added water so that no single emulsifying action need be excessively large. It has often been found desirable to performthe last emulsifying step immediately prior to introduction into an electric field, for instance by using an emulsifying means for discharging directly into the eld, 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 otherwise removed before subjection to an electric field, 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 therein, 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 is 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, dissolved therein. 1n 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 to provide 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 sub- `iection 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. l.

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

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

l Fig. 6 is a sectional view of the washing device of the invention.

In Fig. 1, I have very diagrammatically shown one type of refining system I8 comprising a. fractionating means for removing various fractions from the oil to be refined. Four refining units I2, f3, and |4 are shown.

The refining unit is shown as including a still 2|, a tower 22, a heat exchanger 23, and a condenser 24. No attempt has been made to show reflux systems or speciiic details of these structures, such features being well known in the art. Suffice 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, these passages being in heat-transferring 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, owing 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 a condenserl 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.

The refining unit |3 is similarly constructed with a still 4|, a tower 42, a heat exchanger 43, and a condenser 44 to which the vapors are respectively delivered by pipes 45, 46, and 4l. The water enters the condenser 44 through a pipe 48 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 5|, 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 a pipe 58 and is discharged through-a pipe 59, the condensate being discharged through a pipe 68.

These refining 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 refining units shown, as well as in other systems, the heat exchanger and the condenser form a heatexchange 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 to a suitable dehydrator 66 which separates a major part of the water content, the water being discharged through a pipe |51.` 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. This dehydrated oil is pumped from the dehydrator 68 through a pipe 88 by a pump 69 and is stored in a tank 10. Usually, this tank is near the retlnery, and a considerable length of 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 various impurities are dissolved, and that the oil itself contains acid dissolved therein.

This oil is pumped from the tank by a pump 1| andmoves through a pipe 12 to one ofthe 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 flowing stream of dehydrated oil in the pipe 15 through a pipe 16, the flow being controlled by a valve `'|1. A

preliminary mixture is formed when these liquids are brought into contact, and this mixing action may be the first of se feral used to form the resulting, relatively loose emulsion or mixture. This preliminary mixture ilows through a pipe vI8 where further mixing may take place due to turbulent iiow.

While various sources of water may be utilized, as above-mentioned, the system shown in Fig. 1 utilizes the cooling water ofthecondenser 34 in this capacity. This water is heated during passage through this condenser and is delivered by the pipe 39 to an auxiliary heater 19 where additional heat may be supplied thereto for 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 into the water, if desired.

The heated water moves from the auxiliary heater 'I9 through a pipe 82 to a pump 83 which develops suillcient pressure to force this hot water through the pipe 16 and into` the fiowing 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-J8. An emulsifier is indicated by the numeral 85 as receiving this preliminary mixture and discharging samein emulsified condition into a pipe 86 leading to the electric treater 81. Such an emulsifler may comprise any properly designed emulsifying device which forms an emulsion of the desired character by mechanical mixing, friction, centrifugal force, etc. One Itype of emulsifier which I have found to be very simple and effective 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 differential on opposite sides of the valve and controls the size ofia passage 92 between a seat 93 and a valve member 94. It thus controls the emulsifying tendency. Y.

As an auxiliary emulsiiier, I have disclosed a pump 85 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 thedesired 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 waterA 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 emulsifier 85. In this instance, further mixing will take place in the emulsifier 85. However, if this further mixing is not desired, the pump` 95 may discharge into the pipe 86 through a, pipe |00, the flow being controlled by a valve |0I. In some instances, the pump 95 can be utilized for emulsifying purposes exclusive of the emulsiiier 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 can be used to Ithe exclusion of the pump by opening the valve |02 and closing the valves 91, 99, and |0i. In other instances, these emulsifying means may be used in conjunction with each other by closing a valve |03 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 flowing through the pipe 18 is divided into two streams, one ilowing through the emulsiiier 85 and the other flowing through the 'pipes 98 and |00 to by-pass the emulsier, joining with the stream delivered from this emulsier at a point therebeyond. For instance, the valves 99 and |0| may be adjusted to control the amount of mixture which bypasses the emulsifler. That portion of the stream which moves through the emulsiiier 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 by-passed stream may be of an average size larger than those in the stream moving through the emulsier 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 emulsier 85 and the pump 95 may serve to successively emulsify, as can also the pipes 18 and 86 if they are ofv 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 iield. 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 primary member |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 ||0 at its lower end. A compression spring I|| is disposed be tween the spider |09 and the spacer I0 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 ow 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.

The details of one type of treater 81 which I have found particularly advantageous in the process are best shown in Fig. 3. Referring to this figure, this treater 81 provides a. tank ||0 including a top member ||6 and a bottom member ||1, this tank being grounded as indicated by the numeral ||8.

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

Suspendedv 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 an intermediate electrode structure |25 of two electrodes |28 and |29 connected by a support |30. Y

The electrodes |20, |2|, |28, 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 in'- cluding inner and outer rings |32 and |33 between which extend rods or pipesl |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.

'Ihe electrode |28 is similarly formedvwith 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 upward-extending rings so that a eld is establishedlin 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 29 of smaller diameter than the electrodes |20 and |28.

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 interstital nature of these electrodes permits free 'treating space |21.

ing directly into the treating space |21 to move the emulsion outward therein and successively through the edge-to-edge fields.l By proper design of the electrical system, the potential between the intermediate electrode structure |25 and the electrodes |20 or |2| can be made much higher lthan the potential between any of the live elec-A .trodes and ground. -In Fig. 3, such a system is shown as including two transformers |60 and |6| connected in additive relation. `In this connection, one terminal of each secondary winding is grounded as indicated by the knumeral |62, the high tension terminal ofthe transformer I6| being connected by a conductor |63 to the intermediate electrode structure |25,v 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 However, the potential between the emulsifying distributor means |05 and the electrode |29, or the electrode I2 will be only 12.000 volts. 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 high 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 eo-existing original and added water particles of the newly-formed mixture into masses of sumcient size to gravitate from the oil. Thus, after the treater has been in operation for a period, the upper end of the tank I5 will contain the treated oil and the lower end of the tank will contain a communication between the electric ilelds and fying distributor uneans |05, the latter dischargi 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 definitely control this level to prevent grounding of the electrode |2|. In this connection, it will be apparent that an electric field A will be established in an auxiliary treating space |1| between the lower live electrode |2| and the body of water lin the bottom of the tank ||5. If the level |10 is carried too high, this auxiliary field 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 reversephase emulsion, as will be hereinafter described.

To control the water level in the tank ||5, I have shown an automatic system including a pipe |15 communicating w'ith the upper part of the tank ||5 anda pipe |16 communicating with a water draw-off pipe |11 which opens on the lower end of the tank ||5. The pipes |15 and |16 communicate with a float chamber |18 in which the oil and water are in surface contact at a level corresponding 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 |18. This iioat'may 'be pivoted on a pin |88 connected to an arm Ill which is connectedto a valve |82 in the pipe |11 by any suitable; means. such as a link |83 connected to an arm |84 ofthe valve |82 pivoted at |85 and operatively connected to the stem |88 of this valve. I! the water level rises, the valve |82 will thus be opened a further distance to drain additional quantities of water from the tank H 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 oi the present invention.,

I have found that, in some instances, there is to carry downward therewith particles of oil. 'I'his is not conducive to a clean separation, and, if allowed to continue, will result in contaminated water bleeds. the oil being-carried downward into a tendency for the settling coalesced water masses 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 which 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-of! pipe |11, I illustrate a multiorice discharge head |98. This head maybe 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 of these orifices may be vertically disposed,though best results are obtained if other orifices are angularly disposed relative to the horizontal. A plate |85 closes the cap |82 and receives a pipe |98 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 I5 to form water masses which slowly rise toward the surface |18 due to the inclined nature of the orices or to thermal action, or to a difference in density if the incoming water is fresh, or to various combinations of these factors. A desirable thermal effect is obtained by`delivering to the pipe* |81 water which is slightly hotter than the water in the bottom of the tank H5. This may be accomplished by connecting the pipe |91 to the pipe 16, and thus to the discharge of the pump 83, the i'iow being controlled by a valve |99.

The action of these rising water masses is to sweep i'rom the body of water in the bottom of the tank H5 any oil or reverse-phase emulsion.

v The upward movement of the newly-added water particles moves such a reverse-phase emulsion toward the surface |18 and thence into the auxiliary electric eld |1| in which such an emulsion is separated. This expedient of introducing water massesk into the body of water in an electric treater is particularlyl "aluable 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 oi oil in such a mass of water by adding to the water ilowing through the pipe |81 a. small quantity of a chemical de-emulsifying agent. Various types of such agents are known. Particularly desirable results have been obtained by the use of a chemical deemulsifying agent which is both oil-soluble and water-soluble, though other chemical de-emulsltying agents can be used.-

aaneen The treated oil moves from the upper end or the tank ||8 through; a pipe 288, the now being controlled by a valve 28| which. in turn, assists in controlling the pressure in the tank H5. This treated oil maybe moved directly into the renning system, though I ilnd it preferable to discharge same into a treated-oil storage tank 282 where some additional separation o! the water will take place. v

A pumpy 283v is shown for withdrawing the treated oil from the tank 282 and moving 'same through a pipe 284 to the heat exchanger I3. Additional heat is supplied at this point and the treated oil moves through a pipe 285 to the heat exchanger 53. Being thus additionally heated, the treated oil moves through the pipe 8| to the still 2|. Here, certain lighter fractions are removed, as previously described, the topped oil moving'through a pipe 281 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 5i through a pipe 288 to a cracker 2|8. Various of such crackers are known in the art and need not bel 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 I8 causes cracking and vaporization, the vapors moving through a pipe 2I| and being condensed in a condenser 2|2, the residue being discharged from the cracker-'M8 through a pipe 2|5.

By way of example, and without limiting my- 85 self 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 40 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' examplel the incoming oil moved through the heat exchangers 23 and 33 and was raised to a temperature from to 150 F. The 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 18 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 lakes, rivers, domestic water supplies, etc. Percentages of water between 10% and 50% could be used with success, though approximately 20% of water gave best results in forming the resulting mixture. Operation was slightly improved by :letting additional water upward in the body of water in the tank H5, the water thus introduced being at a temperatureslightly higher than that of the water relatively stable, and substantially 90% of theI water would gravitationally separate from the oil as free or emulsified water il 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 I 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 was approximately 12 lbs/sq. in., and the pressure drop across the emulsifying valve, such as shown in Fig. 2y was approximately lbs/sq. in. Additional drops in pressure due to pipe friction brought the pressure in the pipe 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 upperend of the treater 81 showed the presence of minute water droplets of a size in the neighborhood of 1 mu, approximately the size of the original droplets present in the incomingoil. 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 proof `essing the oil as herein-disclosed before fractional distillation thereof, it was found possible to eiect 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 if 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 the 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 diiculties were minimized and better products produced. As illustrative of the latterfactor, this refinery was unable to produce asphalt of the'desired solubility prior to use of the present invention. Thereafter, the solubility of thel asphalt was raised to 99.9%.

In general, it'will be found that the process 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 vary with 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 con-` taining 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 hereinbeforedefined. 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 notl to be readily treatable by the electric field. In some instances, 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 F. to 210 F. but higher temperatures can be used, up to the 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 particuiarly eiective 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 F.

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 ofthe 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 often desirable to have the added water droplets of a heterogeneous size, though this is not always essential,

In forming this type of mixture, various expedients can be used. Injection of one liquid at right angles into a flowing stream of the other, together with now through the necessary conduit communicating with the treater. can sometimes be used without additional mixing action. In other instances, such a system can be used with the emulsifying distributor means ,hereinbeforedescribed. A `properly-designed pump, operated under controlled conditions can be used in some instances on certain oils withoutv additional emulsifying means, or such a pump. can be used in conjunction with the mixing a tion resulting from injection, or from the use o an emulsifying distributor means. or from bo l In other instances, an emulsifying valve, prop--` erly designed and properly icontrolled, can be used, or this can be used in conjunction with any of the additional emulsifying means above mentioned. In some instances, particularly desirable results have been obtained by dividing the stream of the preliminary mixture, moving a portion through a suitable emulsiiler and another portion in by-passing relation with this emulsiier. The two streams join beyond the emulsiiler and, in so joining, an additional gentle mixing action is obtained which rather uniformly distributes the droplets of the: by-passed stream throughout the mixture which moves from the emulsifier.

As a general rule, the desirable type of resulting mixture or emulsion requires a'deiinitely 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 certainselected 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 ibs/sq. in to 60 lbs/sq. in. has been used with success, though these limits can often be departed from. From 5 1bs./sq. in to 15 lbs./sq. in. is usually best in this regard.

In some instances, the mixture may deslrably be heated with' or without heating the incoming oil or the water. Best temperatures of the resulting mixture, when subjected to the field, are from 100 F. to 199 F., though atmospheric temperatures are sometimes effective.

As to the electric treater 81, any electric treater capable of bringing the coexistng droplets together can be used, such action being hereintermed 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 success, the embodiment illustrated being found particularly effective.

Introduction of th'e resulting mixture or emulsion directly into the electric neld has been found to be desirable in many instances, as sludglng tendencies are almost completely eliminated by such a direct introduction. However, with heavier oils, or ,with mixtures having no distinct sludging tendency, it is sometimes possible to intraduce the emulsion into the tank l Il at a point spaced from the main iield, allowing the emulsion to subsequently. gravitate or otherwise move thereinto. With such oils, introduction into th'e auxiliary treatingspace lll can sometimes be.

used. While satisfactory results can sometimes be obtained by-maintaining substantially atmospheric `pressure in the treatr 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 t end of the electric treater 81, the water content contentof the outiiowing oil is largely within the vand sand, are typical examples.

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. 0n 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 thesystem, 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 problem 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 Ain the oil and various impurities colloidally dispersed in the oil. for instance mud Assuming that the incoming oil contains not more than a vfew percent of water. and that this water carries various impurities which will be removed as above see forth, it will be clear that acids thus dissolved in the water droplets will be removed along with 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 impuritiesby following the procedure outlined above. Just why this is the case is not distinctly understood. It

` from the ou to the water, and

" sulting mixture is readily water present therein.

2,886,941 y with the als or medecine. nem into ou separated inthe electric treater.

v So, also, the invention vis applicable to removal cf impurities-dissolved in, or dispersed in, the oil, regardless of whether or not water dropletsl are present. For instance,it has been Ioundfpossible to remove oil-dissolved acid and colloidally-dispersed 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 retreatable by an elecdroplets of the added Here again, it has been found that th'e oil-dissolved acid and the colloidally-dispersed impurities become associated with the added water by some action in the electric eld, and not in lthe 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 rening by fractional methods. Various other uses of the invention will be apparent to those skilled in the art. If used with a reiinery system, the connections disclosed will be found of particular utility in savlng 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 tric eld to coalesce the 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 added water. 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 endI 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, ii.' 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 vcomprises .the treatment of a mineral oil containing no more than a few-per `cent of waterl by mixing a relatively freshwater 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 desiredaction will be obtained. Thismixing shouldv be of such character as to disperse the relatively fresh water eiIectively throughout. the oil and-to form an emulsion which is in a condition'to be continuously and substantially Y completely resolvable appearin the water at the junction of which said streams of oil and l and water, without the accumulation of such amount of sludge comprising" unresolvedemulslon as would interferefwithfthe maintenance ol.' the electric field. Any such-increasing accumulation of sludge would seriously interfere with thek continuity of the process, iwhich, being often connectedto refinery equipment,` must remain on-stream for long periods of time. In addition, electric treatment well `suited to` the articial emulsion `or mixtureashould be. used, and should tained by subjection to an electric field and separation of the coalesced water masses.

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

This application is a division ot myco-pending application, Serial No. 122,470,- led January 26, 1937 (now Patent No. 2,182,145), which is a continuation-impart of my abandoned application, Serial No. 66,404, illed February 29, 1936.

I claim as my invention:

1. Apparatus for purifying salty mineral oils of low water content, including in combination: a tank closed from the atmosphere; electrode means in said tank for establishing a coalescing electric field therein; means for continuously forming an electrically-treatable oil-continuous dispersion, said means including a pipe means providing a stream-contacting zone, means for continuously delivering to said'stream-contacting zone lof said pipe means under superatmospheric pressure proportioned streams of the salty oil of low water content to be purined and relatively fresh water to preliminarily mix said salty oil and-said relatively fresh water in said zone said streams, and a distributor means at the end tributor means stant of discharge from said pipe means into said tank to produce said oil-continuous dispersion, said distributor discharging saiddispersion into said tank in a position to be treated by said coalescing electric eld to coalescer the dispersed water into masses containing saltsremoved from the oil and said preliminary mixture -beingadditionally mixed beyond said stream-contacting zone solely by passage of said distributor meansat the point of discharge into .said tank except for incidental mixing caused by ow of said lpreliminary mixture along said pipe means to said distributor means, said superatmospheric pressure `under water are brought together in said zone being sufdcient to advance said preliminary mixture along said pipe means and through saidl distributormeans 1 and 'being sufcient to maintain a superatmospheric pressure in said Vtank to avoid any necessity of pumping said preliminary mixture Vafter formation thereof which pumping of such preliminary mixture would make the oil-continuous dispersion less susceptible to electric treatmentsa id tank be capable of continuously treating same so that substantially complete resolution cana' be obpassage through lsaid restrictedv at which said streams of water and oil are brought together. I

2. A combination as defined in claim l. in

which said distributor means includes two members forming said restrictedA e, means for wtrol the 4intensity of said additional mixing action of said distributor means on said prelimmary mixture at the instant of discharge from saidpipemeansintosaidtank. A

3. Apparatus for purifyingA mineral oil of low water content, which comprises: separating means for coalescing and separating the aqueous phase of a water-in-oil type emulsion, said separating means including a tank closed from the atmosphere and containing electrodes for establishing a coalescing electric neld in said tank; a pump for an aqueous medium; a pump for said oil, each of said pumps having an outlet: pipe means connected to the outlets of'said pumps, said pipe means having a -juncture for commingling streams of said oil and aqueous medium from said pumps to form a combined stream and providing `a conduit for said combined stream; a mixingmeans having a ,restricted passageway therein and connected to said conduit for mixing said combined stream; discharge -means for discharging the mixed stream into the interior of said tank for treatment in said eld; a conduit connecting said mixing means to said discharge means, said restricted passageway of said mixing means being substantially smaller in cross-sectional area than the interior of either of said conduits, said pumps forcing said com- -bined stream to iiow through said mixingmeans, said conduits, and to said discharge means with progressive pressure reduction during such now, the mixing of thel oil and aqueous medium of said combined stream forming said emulsion and being eiiected exclusively lby agitation induced by such ilow and lthis flow being effected exclusively by' said pumps; and means for separately withdrawing aqueous medium containing impurities from said'oil and purified oil from said separating means.

4. Apparatus forvpurifying mineral oil of low water content, which comprises: separating means for coalescing and separating the aqueous phase of a water-in-oil type emulsion, said separating means including a tank closed from the atmosphere and containing electrodes for establishing a coalescing electric field in said tank; pipe means for an aqueous medium; pressure means for forcing said aqueous medium through said pipe means; pipe means for said oil; pressure means for forcing said oil through said lastnamed pipe means, said pipe means forsaid aqueous medium and said oil having a juncture for commingling streams of said oil and aqueous medium from said pressure means to form a combined streamY and providing a conduit for said combined stream; a mixing means having a restricted -passageway therein and connected to said conduit for mixing said combined stream: discharge means for discharging the -mixed stream into the interior of said tank for treatment in said field; a 'conduit connecting said mixing means to said discharge means, said restricted passageway of said mixing means being waterl content, which comprises:

substantially smaller in cross-sectional area than the interior of veither of said conduits, said pressure means forcing said combined stream to iiow through said mixing means, said conduits. and to said discharge means with progressive pressure reduction during such now, the mixing of the oil and aqueous medium of said combined stream forming said emulsion and being eifected exclusively by agitation induced by such i'lowvand this flow being effected exclusively by said pressure means; and means for separately withdrawing aqueous medium containing impurities from said oil and purified oil from said separating means.

5. Apparatus for purifying mineral oil of low separating means for coalescing and separating the aqueous phase of a water-in-oil type emulsion, said separating means including a tank closed from the atmosphere and containing electrodes for establishing a. coalescing electric field in said tank; pipe means for an aqueous medium; pressure means for forcing said aqueous medium through said pipe means; pipe means for said oil; pressure means for forcing said oil through said lastnamed pipe means. said pipe means for said aqueous medium and said oil havinga juncture for commingling streams of said oil and aqueous medium from said pressure means to form a combined stream and providing a conduit for said combined stream; a first mixing means having a restricted passageway therein and connected to said conduit for mixing said combined stream: discharge means for discharging the mixed stream into the interior of said tank for treatment in said eld and comprising a second mixing means having a restricted passageway; a conduit connecting said rst mixing means to said discharge means, said restricted passageways of said rst mixing means and said discharge means being substantially smaller in cross-sectional area than the interior of either of said conduits, said pressure means forcing said combined stream to iiow through said rst mixing means. said conduits, and said discharge means with progressive stream forming said emulsion and being effected exclusively by agitation induced by such ow andthia iiow being effected exclusively by said pressure means; and lmeans for separately withdrawing aqueous medium containingimpurities from said oil and puried oil from said separating means.

6. Apparatus for purifying mineral oil of low water content, which comprises: means for coalescing and separating the aqueous Y phase of a water-in-oil type emulsion. said separating means including a tank closed from the atmosphere and containing electrodes for establishing a coalescing electric iield in said tank; pipe means for an aqueous medium; pressure means for forcing said aqueous medium through said pipe means; pipe means for said oil; pressure means for forcing said oil through said lastnamed pipemeans, said pipe means for said aqueous medium and said oil having a juncture for commingling streams of said oil and aqueous meseparating conduit means having at least one restricted passageway positioned therein and forming a mixing means for mixing said combined stream to form said mixed stream, said restricted passageway being substantially smaller in cross-sectional area than the remainder of said conduit means, said= pressure means forcing said combined stream to ow through said conduit means including said mixing means with progressive pressure reduction

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