US3011970A

US3011970A - Liquid phase contacting of hydrocarbons

Info

Publication number: US3011970A
Application number: US805289A
Authority: US
Inventors: Eugene P Goodmann; Gordon Moses; George E Thompson
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1959-04-09
Filing date: 1959-04-09
Publication date: 1961-12-05
Anticipated expiration: 1978-12-05

Description

Dec. 5, 1961 E. P. GOODMANN ETAL 3,011,970

LIQUID PHASE CONTACTING OF HYDROCARBONS' 3 Sheets-Sheet 1 Filed April 9, 1959 INVENTORS Eugene F. Goodman/1 Moses Gordon George E Thompson y WQM/ AT TORA/E kw 55% Q 531% Dec. 5, .1961 E. P. GOODMANN ETAL 3,011,970

LIQUID PHASE CONTACTING OF HYDROCARBONS Filed April e, 1959 5 Sheets-Sheet 2 Fig. 2

EFFLUE/VT ZONE To Praa'uc/ SCREEN TRAPS BA FFL 22% 5 L REACTOR- GLAR/FIEI? g7 Feed INVENTORS Eugene R Good/norm Moses Gordon George E. Thompson E) W ATTOR/VE Dec. 5, 1961 E- P. GOODMANN ETAL LIQUID PHASE CONTACTING OF HYDROCARBONS Filed April 9, 1959 Vent 3 Sheets-Sheet 3 Fig. 4

.99 j Product F res/2 0r Regenero/ed /0/ Solution DOUG/Mg; BAFFL E Feed INVENTORS Eugene H Goodman/I Moses Gordon George E/mmoson ATTORNEY United States Patent 3,011,970 LIQUID PHASE CONTACTING F HYDROCARBONS Eugene P. Goodmann, HighlamLInd and Moses Gordon and George E. Thompson, Chicago, 111., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Filed Apr. 9, 1959, Ser. No. 805,239 Claims. (Cl. 208-488) This invention relates to the contacting of liquid hydrocarbons and aqueous media to produce liquid hydrocarbons essentially free of aqueous medium.

The petroleum industry and the chemical industry uti lize large and small scale operations requiring the contacting of liquid hydrocarbons with an aqueous medium. Such contacting results in liquid hydrocarbon cntaining droplets of aqueous medium dispersed therein. In the petroleum industry such a hydrocarbon is commonly spoken of as being hazy. Various procedures are known for removing this dispersed aqueous medium from the liquid hydrocarbonnone of these are either simple or cheap.

Thus far all efforts to develop a process for contacting a liquid hydrocarbon with an aqueous medium to produce a haze-free liquid hydrocarbon have been fruitless. An object of the invention is a method of contacting an aqueous medium and a liquid hydrocarbon to produce an essentially haze-free liquid hydrocarbon, said method not requiring a separate debazing operation. Another object is a continuous method for contacting a liquid hydrocarbon and an aqueous medium in a single step to produce a haze-free liquid hydrocarbon product. A further object is a process for removal of haze from a liquid hydrocarbon by a contacting operation with an aqueous medium. Yet, another object is a method of contacting a mercaptancontaining liquid hydrocarbon with an aqueous caustic medium to reduce the mercaptan content of the hydrocarbon without introducing a haze to the liquid hydrocarbon product. Still a further object is a process for treating a H S containing liquid hydrocarbon with an aqueous caustic medium to remove said H 3 without introducing a haze to the liquid hydrocarbon product. Other objects will be apparent from the detailed description of the invention.

The method of the invention utilizes a dispersed liquid system characterized by (a) an aqueous medium as the continuous phase, (b) liquid hydrocarbon droplets forming the dispersed phase and at least a substantial part of the total dispersed system, (c) a grease-like appearance, and from which system is readily separable clear essentially aqueous-medium-free liquid hydrocarbon. This dispersed liquid system is obtained by contacting the liquid hydrocarbon with the aqueous medium in various ways which will be described in particular hereinafter. A clear essentially aqueous-medium-free liquid hydrocarbon, i.e., haze-free liquid hydrocarbon, is readily separated from the dispersed liquid system. The method may be batch wherein the liquid hydrocarbon and aqueous medium are contacted to form the dispersed liquid system and the dispersed liquid system is then permitted to separate into aqueous medium and haze-free hydrocarbon product. Or the process may be a continuous one wherein the dispersed liquid system is maintained and a supernatant layer of haze-free hydrocarbon formed above the dispersed system; said liquid hydrocarbon is then added continuously into a lower portion of the dispersed system and clear hazefree liquid hydrocarbon is continuously withdrawn from the supernatant layer. In some cases, a third layer may be formed providing a three layer system; in this system fresh aqueous medium and hydrocarbon feed are continously added to the dispersed system while hydrocarbon "ice product is continuously withdrawn from the supernatant layer and exhausted aqueous medium is continuously withdrawn from the bottom layersaid three layers being present in the vessel. The outstanding characteristic of the dispersed liquid system, as it is seen by the human eye, is the shiny surface and smooth undulating ripplesresembling a light grease being agitated by a propeller mixer. The surface sheen and the undulating-flow appearance of the surface of the dispersed liquid system has caused this system to be generally described as appearing grease-like. The appearance of the surface of the dispersed liquid system does not markedly change with change in the degree of agitation :being applied to the systemexcept when a very large change in agitation takes place and the dispersed liquid system may indeed be destroyed. In general the dispersed liquid system resembles milk in coloring and opacity. The dispersed liquid system is a good conductor of electricity which shows that it is an oil-in-water dispersion.

The dispersed liquid system can be for-med by contacting a small amount of liquid hydrocarbon with an aqueous medium or a small amount of aqueous medium with liquid hydrocarbon. At very low hydrocarbon content it is d-ifficult to maintain the desired characteristics of the dispersed liquid system; the optimum proportion of hydrocarbon and aqueous medium for a particular use is determined by the type of hydrocarbon, the type of aqueous medium and the temperature of contacting. For lower petroleum hydrocarbons the dispersed liquid system contains as little as 10 volume percent to as much as 85 percent of the hydrocarbon with the remainder aqueous medium. For lower petroleum hydrocarbons a more stable dispersed liquid system is obtained with a system wherein the hydrocarbon dispersed phase is the predominant part of the dispersed system-hydrocarbon contents between 50 and about volume percent give excellent results. In a procedure wherein the liquid hydrocarbon contains a sufiicient amount of finely-divided aqueous droplets to impart haze thereto, it is preferred to operate with a dispersed liquid system containing between about 70 and 80 volume percent of hydrocarbon.

The outstanding result obtainable with the dispersed liquid system of contacting is the clarity of'the liquid hydrocarbon product. In spite of the self-evident intimate contacting between the liquid hydrocarbon and the aqueous medium in the dispersed liquid system, the liquid bydrocarbon product contains essentially no dispersed aqueous medium and may be described as essentially hazefree. Or in another term the liquid hydrocarbon product has a bright appearance.

The liquid hydrocarbon feed to the instant method may be any hydrocarbon which is liquid at ordinary temperatures and pressures or readily liquifiable by operation at somewhat elevated pressures. The liquid hydrocarbon may be a single compound or mixture of close boiling compounds or may be a mixture boiling over a narrow or broad range. To illustrate, materials such as propane, butane; mixtures of: butanes,he'xanes, o'ctanes; benzene, toluene, xylenes, etc. may be charged. Examples of petroleum fractions suitable for use in the method are: light naphtha, boiling over the range of about 80225 F.; heavy naphtha, boiling over the range of about 2.004l5 F.; kerosene, boiling over the range of about 325-525 F.; gas oil, boiling over the rangeof 450-700 F.; etc. The method is applicable to liquid hydrocarbons whether they be aliphatic or aromatic in nature; whether they be saturated or unsaturated; whether they be straight chain or cyclic. Furthermore, the petroleum hydrocarbon fractions may be derived from any of the known refining operations such as distillation of crude, thermal cracking, catalytic cracking, coking, thermal rei rming, catalytic reforming, catalytic desulfuriza'tion or hydrogenation. It is to be understood that the above illustrative examples of the liquid hydrocarbons charged to the method and process from which they may be derived are not limiting with respect to the scope of the hydrocarbon feed for the method.

The aqueous medium utilized in the formation of the dispersed liquid system may be water itself, an aqueous caustic solution or an aqueous caustic solution containing dissolved phenolic compounds. The aqueous caustic solution may contain any of the alkali metal hydroxides, particularly sodium hydroxide or potassium hydroxide. In general the solution may contain from one weight percent up to substantially the saturation amount of caustic at the particular temperature of operation. The aqueous caustic solution concentration will be dependent upon the particular usage, for example, in the removal of hydrogen sulfide, low concentrations on the order of 110 weight percent will generally be used. In the extraction of mercaptans from mercaptan-containing hydrocarbons, i.e., sour hydrocarbons, the solution will generally contain on the order of -25 percent caustic. In some instances of operation with aqueous caustic solution, a substantial saturation amount of caustic will be desirable, such as, in dehazing a viscous gas oil when operating at higher temperatures of contacting.

The presence of caustic in the aqueous medium tends to improve the stability of the dispersed liquid system. It is preferred to utilize such a caustic containing medium as the contacting agent; however, there are situations in which further improvement and stability may be obtained by the presence of phenolic compounds, such as cresols and xylenols. The mixture of cresols derivable by aqueous caustic extraction of thermal cracked naphthas is a particularly suitable phenolic material. In the contacting of a gas oil with aqueous caustic solution it is preferred to have the solution contain between about 1-20 volume percent, based on solution, of phenolic compoundsthese exist in the solution in the form of alkali metal phenolates, or in the case of petroleum cresols in the form of alkali metal cresylates.

In the removal of materials such as mercaptans from liquid hydrocarbons by contacting with aqueous caustic solution, the presence of phenolic compounds improves the eifectiveness of the mercaptan removal. In the case of mercaptan extraction it is desirable to use higher amounts of phenolic compounds and particularly petroleum cresols on the order of 35 volume percent present in the form of alkali metal cresylates. The method of the invention is particularly suitable for use with aqueous caustic solutions which are substantially saturated with cresols; the solutions are hard to use in ordinary contacting operations because of their very high viscosity. The method of the invention may be used at any temperature wherein the aqueous medium and the hydrocarbon are liquid. It is to be understood that super-atmospheric pressure may be necessary in order to maintain the hydrocarbon liquid. Broadly, the temperature of contacting may be between about 30 and 300 F. A more common range of temperatures is the region of 50 to 150 F. It is preferred to operate at the lowesttemperatures consistent with the formation and maintenance of a stable dispersed liquid system. For example, when. operating with the lower viscosity hydrocarbons such as naphtha or kerosene it is preferred to operate at a range between about 6090 F. In the case of gas oils and such high viscosity fractions, in general, the operation will be on the order of 100-140 F. a

The temperature at which the contacting is carried out has a significant effect on the stability of the dispersed liquid system and therefore the process should be operated at the lowest temperatures possible as determined by the aqueous medium and the hydrocarbon feed. However, it is to be understood that other benefits such as increased thruput and better contacting may determine operation at higher temperatures, even though it may thereby make it more diin'cult to maintain the desired oil-in-water dispersion, that is, avoiding inversion of the system to the water-in-oil type, which type is completely inefiective for the method of the invention.

The dispersed liquid system contacting zone of the invention can be formed by many intermingling procedures. Some procedures permit the formation of the dispersed liquid system much more easily than do others. It is entirely possible to form a dispersed liquid system by introducing into a centrifugal pump at proper conditions the liquid hydrocarbon and aqueous medium; the two liquids emerge from the pump in the form of a dispersed liquid system, which is then passed to a settling vessel wherein the bright hydrocarbon is separated from the aqueous medium. In another procedure the dispersed liquid system is formed by the use of a propeller mixer or turbine mixer in a vessel wherein the liquid hydrocarbon and the aqueous medium may be introduced continuously and the dispersed liquid systemwithdrawn continuously to a separate vessel, then separated from the aqueous medium and the bright liquid hydrocarbon product. The dispersed liquid system may be formed by the use of any impeller such as a propeller mixer or turbine mixer. When utilizing an impeller it is customary to have the impeller shaft on the vertical axis of the vessel containing the dispersed liquid system; the impeller may be in this instance of the top-entry or bottom-entry type. The dispersedliquid system may be prepared by the use of side-entry impellers when the configuration of the vessel makes this the preferred manner of introducing the agitation means. When using an impeller positioned on the vertical axis of the vessel, it is preferred to improve the degree of agitation by installing vertical mixing baflles at the periphery of the vessel. These vertical baffies need project into the interior of the vessel only a relatively short distance in order to provide the additional turbulence needed to form and improve maintenance of the dispersed liquid system. It is to be understood that the particular type of agitating means and the presence of or absence of bafiies is a matter which may be determined by ordinary skill for a particular installation, after one has had the benefit of this disclosure and in particular, the illustrative examples, which form a part of this specification and disclosure.

The preferred mode of use of the method of the invention involves the use of a single vessel which functions not only as the contacting zone but also as the separation zone. By this it is to be understood that there are present in the vessel a dispersed liquid system layer (zone) and at least a supernatant bright liquid hydrocarbon product layer. Because this single vessel provides not only the desired contacting between the liquid hydrocarbon feed and the aqueous medium, but also produces a clear bright liquid hydrocarbon product, the term reactor-clarifier has been applied to the vessel affording this unitary contacting-clarification result.

When operating a unitary reactor-clarifier it is pre ferred to utilize an impeller selected from the class consisting of propeller mixers and turbine mixers, and more particularly, a top-entry mixer, which mixer is positioned on the vertical axis of the reactor-clarifier. The dispersed liquid system zone may be formed either by adding the aqueous medium and a sufiicient amount of liquid hydrocarbon feed separately to the reactor-clarifier, or introducing the two amounts substantially simultaneously while the impeller is in motion. Assuming the aqueous medium and the desired amount of liquid hydrocarbon feed have been introduced into the reactor-clarifier individually forming a lower aqueous medium phase and an upper liquid hydrocarbon feed phase, the blades of the impeller should be positioned in at least a proximate relationship to the aqueous medium. It is to be understood that the blades of the impeller may be entirely immersed in the aqueous medium, or substantially immersed therein, or may be entirely immersed in the hydrocarbon phase, a short distance above the top of the aqueous medium phase. Apparently sufiicient intermingling of the two phases is obtained to form the dispersed liquid system when the impeller is entirely within the aqueous medium phase, but it is very diiiicult to form the dispersed liqui system when the impeller is in the hydrocarbon phase unless the impeller is capable of drawing substantial amounts of aqueous medium up into the hydrocarbon phase. The position of a turbine mixer near the interface between the two phases is more critical than that of the propeller. It is preferred to use a propeller which forces the liquid upwards; in this instance-forces aqueous medium upwards into the hydrocarbon phase. When using such a upflow propeller good results are obtainable even when the propeller blades are positioned a substantial distance above the interface of the aqueous medium and liquid hydrocarbon phases.

The impeller is turned on at a speed which will form the dispersed liquid system; this speed is dependent on the type of impeller, the type of hydrocarbon feed, the type of aqueous medium and the temperature of contacting. At the proper conditions very quickly the separate phases of aqueous medium and liquid hydrocarbon disappear and there is present in the reactor-clarifier what appears to the human eye as viscous creamy liquid. The surface of this liquid presents a smooth undulating appearance like a pool of water into which a small stone has been dropped. In a vessel with transparent sides the dispersed liquid system gives to the eye an impression of violent turbulent motion. A dispersed liquid system, which is on the border line of stability may be, to the eye, a mixture of oily droplets and aqueous medium. A stable system does not, to the naked eye, show the presence of dispersed droplets.

The most important identifying characteristic of the dispersed liquid system utilized in this invention is the appearance of hydrocarbon product emerging from the dispersed liquid system. It has been found, to the eye, that the single phase system can produce a supernatant layer of liquid hydrocarbon which supernatant liquid hydrocarbon is essentially free of droplets of aqueous medium and is transparentinsofar as the natural color of the hydrocarbon permits; in practice the emergence of the supernatant hydrocarbon layer is determined by decreasing the degree of agitation given the dispersed liquid system for its initialformation. After the reduction in degree of agitation a finite period of time elapses before a significant amount of hydrocarbon emerges from the dispersed liquid system. The reason for this initial time lapse is not understood, but may be due to the initial time needed to coalesce a number of dispersed droplets to exceed the capacity of the dispersed liquid system for holding same or it may be due to the mere passage of time needed to accumulate enough supernatant hydrocarbon to become perceptible to the naked eye. In any event after the emergence of a visible supernatant layer, the supernatant layer rapidly increases in depth and finally attains a fixed depth dependent somewhat upon the degree of agitation being imparted to the dispersed liquid system. The rate of emergence of bright hydrocarbon product appears to be most closely related to the composition of the dispersed liquid system, i.e., the relative amounts of oil and aqueous medium present. In general, when the dispersed liquid system contains more than about 50 volume percent oil, the settling rate of the system or the rate of emergence of oil has a straight line relationship with the oil content of the system. (The effect of said composition on oil rate is set out in more detail in Example 6 herein.) The liquid hydrocarbon product is withdrawn from the supernatant layer positioned above the dispersed liquid system layer in the reactor-clan'fier.

It has been observed in continuous operation wherein two or three layers exist in a reactor-clarifier the volume occupied by the dispersed liquid system layer increases with the time of contacting. This increase in volume has been designated bed expansion and apparently eventually takes place, regardless of the aqueous medium and with all types of hydrocarbon feed. Interestingly enough it has been found that a reduction in the amount of dispersed liquid system, on a weight basis, by physical removal of a portion thereof does not interfere with the production of a bright clear liquid hydrocarbon product. This indicates that in the experiments carried out the thickness of the dispersed liquid system layer has always been greater than the minimum amount needed to obtain the needed degree of contacting with simultaneous production of a bright clear product.

It has been observed that in situations wherein considerable amounts of material are removed from the hydrocarbon feed such as dispersed water or mercaptans that the dispersed liquid system produces in addition to the supernatant hydrocarbon layer a third layerbelow the dispersed liquid layer. This third layercommonly spoken of as the bottom layer-consists of aqueous medium of a diiferent composition than that aqueous medium used to form the system. The precipitation of the third layer is most readily obtained with fresh aqueous medium being continuously introduced into the dispersed liquid system layer, as is necessary in continuous operation for mercaptan extraction. The third layer is preferably continuously withdrawn from the reactor-clarifier and discarded or worked to recover reusable aqueous medium. Thus, in mercaptan extraction the bottom layer consists of aqueous caustic solution, alkali metal cresylates and is rich in mercaptans in the form of alkali metal mercaptides-this solution is commonly spoken of as a mercaptan-rich solution. The mercaptan-rich solution may be regenerated by any of the techniques well known to the petroleum industry and the chemical industry to remove all or substantially all of the mercaptans and produce an aqueous caustic solution which is lean in mercaptans and which is commonly spoken of as lean solution; this lean solution may be recycled to the dispersed liquid system layer for extraction of additional amounts of mercaptans.

The method of this invention is illustrated hereinafter by a great number of illustrative examples carried out on both laboratory bench-scale and pilot plant-scale equipment. The equipment utilized in carrying out the illustrative examples is set out in accurate detail in order to enable those who Wish to easily duplicate the same. The hydrocarbons, which may also be described as mineral oils, and the aqueous media utilized have been characterized in detail, in order that those wishing to: do so may by use of the equipment, hydrocarbon feed and aqueous medium easily duplicate these examples in order to gain experience, as well as vertification, in the use of the method of the invention. It is to be understood that the illustrative examples set out hereinafter have been purposely set up in great detail and these illustrative examples are to be considered as part of the specification and disclosure concerning the invention hereinafter claimed.

ILLUSTRATIVE EXAMPLES The invention is described with particular reference to a pilot plant operation wherein a virgin gas oil containing finely divided aqueous droplets, in an amount sufiicient to impart a hazy appearance, was treated to remove the haze; a diesel fuel was treated to remove hydrogen sulfide; and a heavy naphtha was treated to extract mercaptans. Also, on a bench scale unit, .mercaptans were extracted from liquid petroleum fractions.

The pilot plant scale examples were carried out in equipment shown in the figures.

FIGURE 1 shows the layout of the pilot plant schematically.

FIGURE 2 shows the type of reactor-clarifier used in the treatment of hydrocarbons when only two layers are present during the treating operation, for example, dehazing of a gas oil.

7 FIGURE 3 shows a cross sectional view at 33 of the reactor-clarifier of FIGURE 2.

FIGURE 4 shows a reactor-clarifier adapted for treating of a hydrocarbon wherein three layers are present. FIGURE 5 shows a cross sectional view at 5-5 of the reactor-clanifie'r of FIGURE 4.

Example 1 In FIGURE 1, the hydrocarbon feed to the process was obtained from source 11. In this instance, source 11 was a 40 bbl. tank. (Throughout this specification, it is to be understood that bbl. means a 42 gallon barrel.) Nitrogen was used to provide an inert atmosphere. Feed from source 11 was passed by way of line 12 to pump 13. Pump 13 forced the feed by way of line 14 into surge drum 16. Surge drum 16 had a capacity of 0.5 bbl. Surge drum 16 was provided with a vent system 17. Nitrogen from cylinder 18 may be passed by way of line 19 and a portion of the vent line into surge drum 16 to provide an inert atmosphere.

From surge drum 16, feed was proportioned by way of line 21, pump 22, line 23, heatexchanger 24, and line 26 into reactor-clarifier 27. Line 23 was provided with a flow meter for checking the charge rate of the feed to reactor-clarifier 27. In this operation, a Rotameter was used to determine the flow rate. Heat exchanger 24 permitted operation at temperatures above ambient.

Reactor-clarifier 27 was provided with a vent system 28. An inert atmosphere of nitrogen could be maintained within reactor-clarifier 27 by means of nitrogen from cylinder 29 introduced by way of line 31 and a portion of vent system 28.

Product hydrocarbon was withdrawn by way of line 33, heat exchanger 34, line 36, and passed by means of pump 37 and line 38 to drums used for storing the product. An inert nitrogen atmosphere was maintained in the drums.

Reactor-clarifier 27 was a cylindrical vessel 51 provided with a stainless steel top closure 52. (See FIGURES 2 and 3.) Vessel 51 was made out of Lucite in order to permit visual observation of the goings-on within the reactor-clarifier. The internal diameter of vessel 51 was 12" and the overall internal height was 24". The reactorclarifier 27 was provided with four vertical bafiles positioned against the vertical wall of vessel 51 and equidistant at the periphery thereof. These

bafiles

53, 54, 56, and 57 were stainless steel strips 22" long, 1%," wide, and 1 thick. While the dispersed liquid system can be obtained within the reactor-clarifier without using vertical bafiles, the dispersed liquid system is more easily attained and maintained by the presence of vertical baffies such as s, 54, 56, and 57.

Screens 61. and 62 are positioned in the upper portion of vessel 51; Screen 61 was positioned approximately 18" above the bottom of vessel 51 and

screen

62, 3" above screen 61. Each of the screen traps was made up of four individual screens, namely, two plastic screens of mesh opening sandwiched between two stainless steel screens of 5 mesh opening.

Reactor-clarifier 27 was provided with a mixing means 64. In this Example 1, mixing means 64 consisted of a /a HR motor, not shown, connected by shaft 66 to turbine 67 provided with 6 fiat blades 68a, etc.

Feed line 26 entered vessel 51 about 2" above the bottom; line 26 was bent at right angles upward at the radial center of vessel 51 so as to introduce the feed below turbine 67; in this instance, about 3" below turbine 67. The introduction point 71 need not be '3 below turbine 67; it may be farther away or essentially immediately below turbine 67. i

The .6 fiat bladed, 4" OD, turbine used in Example 1 was operated at a speed between about 325-350 r.p.m. A speed control on the motor permitted operation at higher or lower speeds if desired.

FIGURE 2 shows the layout of reactor-clarifier used in Example 1 approximately to scale; in addition, dimensions are provided to assist those who desire to duplicate the experimental work set out in this illustrative example. It is to be understood, however, that this detail does not mean that this particular combination of proportions is critical to the attainment of the dispersed liquid system; dispersed liquid systems have been obtained in vessels of difierent proportions, with difierent mixing means, etc.

The feed stock to Example 1 was a virgin gas oil which had been sweetened by the doctor process and water washed to remove doctor solution. The sweet virgin gas oil contained a great deal of finely divided aqueous droplets which imparted a haze dense enough that the oil in a quart bottle appeared semi-opaque. Karl-Fischer analysis of the hazy virgin gas oil showed a total water content of 479 parts .per million. The feed also contained 0.8 ppm. of sodium hydroxide. The physical inspections of this feed were:

The aqueous medium utilized in the treating of Example 1 contained 21% by weight of total sodium hydroxide, i.e., free and combined. Also, the aqueous medium contained 6% by volume of petroleum cresols in the form of sodium cresylates.

The dispersed liquid system was prepared by introducing 4.5 gals. of the aqueous caustic cresylate solution into reactor-clarifier 27. The hazy virgin gas oil was charged in an amount of 4.5 gals. to reactor-clarifier 27. The layers were present after the introduction of the feed and the aqueous medium. The lower layer of aqueous medium extended upward to a point just beyond the upper surface of blades 68 of turbine 67. The turbine was rotated at 350 r.p.m., and in a very short time the'two layers merged into one (to the eye) body of liquid, i.e., the dispersed liquid system.

The dispersed liquid system in the vessel was opaque with a milky coloring. The surface of the dispersed liquid system had a grease-like appearance. From the appearance of the surface of the dispersed liquid system it would be thought that the system was very viscous in character; the top of the system showing shallow undulations, resembling ripples in a pool of water, more or less concentric about the shaft of the turbine. Increasing the turbine speed changed the appearance of the top of the system causing greater turbulence; under these conditions of more turbulence, the upper surface tended to resemble a white cake batter in the bowl of an electric mixer. In another analogy, the dispersed liquid system within the Lucite vessel resembled a clear glass jar of cold cream, even to the shallow wavy appearance usually present on a freshly opened jar of cold cream. In the particular dispersed liquid system, the surface of the system was shiny, resembling a light grease in light reflectivity; this surface shine coupled with the flow characteristics of the surface can be described as a grease-like appearance.

Electrical conductivity tests showed that the dispersed liquid system is a good conductor of electricity, thereby proving the presence of an oil-in-water dispersion. The dispersed liquid system is characterized by the aqueous medium as the continuous phase and liquid hydrocarbon droplets as the dispersed phase.

When a sample of the dispersed liquid system-was introduced into a funnel provided with a stopcock in the stem, the system flowed like a highly viscous fluid through the stopcock and the stemresembling in this respect a semifluid grease.

The appearance of the contents of the vessel could be radically changed by operating at very high flow rates,

particularly with the turbine ata very high speed. The contents of the vessel would abruptly change from the milky color to a dark gray color. The appearance of the surface of the contents would change and become very turbulent. Most important, the contents of the vessel ceased to conduct electricity. Under these conditions, the oil-in-water dispersion had inverted to a water-in-oil dispersion.

At a turbine speed of about 350 rpm, the contents of the vessel (50:50 hydrocarbon-aqueous caustic cresylate) showed only the mihry colored dispersed liquid system. When the turbine speed was reduced to 200-250 r.p.m., for 2-3 minutes, the contents of the vessel retained the appearance possessed at the 350 rpm. speed; then there appeared on the surface of the dispersed liquid system a layer of clear, brigh hydrocarbon; this hydrocarbon layer very rapidly increased in depthsimultaneously the dispersed liquid system decreased in depth. At constant speed and flow rate, the two layers maintained substantially constant depth. A further reduction in turbine speed permitted more hydrocarbon to enter the hydrocarbon layer. The remarkable feature of the upper hydrocarbon layer is its clarity. The hydrocarbon which separates from the dispersed liquid system under these conditions is completely free of haze; apparently, the finely divided aqueous droplets present in the feed virgin gas oil had been removed during the residence time of the hydrocarbons in the dispersed liquid system. The clarity of the hydrocarbon separated from the dispersed liquid system is vividly illustrated by holding a printed page in back of a quart sample bottle full of the product hydrocarbon-the printing could be easily read through the sample bottle, i.e., about a 3" thickness of hydrocarbon. The remarkable nature of this achievement is apparent from the fact that the presence of the printed page cannot be detected through a similar sample of the hazy virgin gas oil charged to the operation.

in this particular example, the dispersed liquid system was formed and a supernatant hydrocarbon layer appeared when the feed was charged into the Reactor- Clarifier; the hydrocarbon layer was 45 inches deep. The Reactor-Clarifier was maintained at 75 80 F., i.e., the ambient temperature in the room housing the pilot plant. Over a period of 8 hours, continuous operation was carried out with the flow rate of speed at 9 gallons per hour, the turbine was maintained at about 350 r.p.m. Virgin gas oil feed was introduced through line 26 and product hydrocarbon was withdrawn by way of line 33. During these 8 hours, the height of the dispersed liquid system remained essentially constant at 18 inches and the product hydrocarbon layer of about 4 inches was hazefree and of bright clarity. Samples of the feed gas oil and the product hydrocarbon were taken regularly over the 8 hour period and analyzed for water content and sodium hydroxide content. (As indicated earlier, the water contents were determined by the Karl-Fischer method.) The water content of the feed virgin gas'oil varied from 470 to 520 parts per million and averaged 479 ppm. The sodium hydroxide content of the feed virgin gas oil averaged 0.8 ppm. The water content of the product hydrocarbon varied from 100 to 140 ppm. and averaged 120 ppm. The sodium hydroxide content of the product hydrocarbon averaged 1.0 p.p.m.

The data show that essentially no sodium hydroxide was picked up by the hydrocarbon even though it had been contacted in this most intimate manner with aqueous caustic solution containing 21 weight percent of total sodium hydroxide.

The Karl-Fischer analysis does not set out in the most start ing manner the efiectiveness of the contacting operation in removing aqueous droplets from the hazy gas oil feed. The solubility of water in the gas oil at 80 F. is about l20 parts per million. In other words, all of the water physically present in the form of droplets in the hazy gas oil feed was removed during the passage through ample l.

the dispersed liquid system phase in the Reactor-Clarifier; the hazy virgin gas oil was at about contacting temperature when removed from the storage tank and, therefore, was saturated with respect to water.

The efiect of temperature was studied somewhat. Increase in temperature of the bed to about F. did not permit any increase in thruput. Even at the 9 g.p.h. rate at the higher temperature, the clarity of the product oil was not as good as that obtained at ambient temperature; this is caused by precipitation of dissolved water as the product hydrocarbon cooled to ambient temperature.

After 8 hours of operation, the unit was shut down and the contents of the vessel permitted to settle into a clear hydrocarbon layer and a lower aqueous caustic cresylate layer which was essentially free of hydrocarbon. Over the course of the 8-hour run, the aqueous medium has changed somewhat, namely, sodium hydroxide content had decreased from 21.3 weight percent to 20.3 weight percent and the cresol content had decreased from 61 percent to 5.8 percent.

Example 2 In this example, a diesel fuel containing hydrogen sultide and dispersed aqueous droplets was contacted with aqueous sodium hydroxide solution in the pilot plant described in FIGURES 1-3. The turbine was positioned 8" above the bottom of the vessel. All of the runs which are described in this example were carried out at a temperature of 70-80 F., i.e., ambient temperatures. The example represents several days operation of the pilot plant with 6-8 hours of continuous thruput in each day.

The charge hydrocarbon to Example 2 was a diesel fuel containing hydrogen sulfide, mercaptans, and haze. The content of hydrogen sulfide, mercaptan, and water represent an average for the several days operation; there were no wide variations in the presence of these materials during the course of the several days of operation considered herein as Example 2. The physical inspections of this diesel fuel are given below.

Preliminary tests on the formation of the dispersed liquid system using the defined diesel fuel feed and aqueous sodium hydroxide indicated that satisfactory stability of the dispersed liquid system could be obtained over the entire range of sodium hydroxide concentrations obtainable with water. Forcontinuousoperation over a period of hours, it was found that the best results were obtained with respect to system stability and clarification with this feed using concentrated aqueous sodium hydroxide solution. For this reason, the runs actually considered as part of this example, were carried out using aqueous sodium hydroxide solution containing 40-42 weight percent of sodium hydroxide. No cresols were present in the aqueous caustic solution as charged to the reactor-clarifier.

In starting up the reactor-clarifier, about 9" of the aqueous sodium hydroxide solution and about 6 of the diesel fuel feed were charged to the vessel. The turbine was operated at 375 rpm. and speedily produced within the vessel a dispersed liquid system appearing, in allrespects, like the dispersed liquid system described in .Ex-

The dispersed liquid system occupied about 15 inches of the reactor-clarifier. When the system had the system (spoken of as expansion).

been formed within the vessel, the diesel fuel was charged into the vessel at a point immediately below the turbine. An upper hydrocarbon liquid layer was quickly formed above the dispersed liquid system. This upper hydrocarbon layer was clear and bright to the eye, i.e., contained no perceptible haze. The standard test for clarity of legibility of a sample tag through a quart bottle of product diesel fuel was applied and the product diesel fuel passed this test. The upper hydrocarbon layer was completely free of hydrogen sulfide, both as determined by analysis and as determined by a copper strip corrosion test. In this copper strip corrosion test, the hydrocarbon and a standard copper strip were maintained at 212 F. for 3 hours; the hydrocarbon produced from the reactorclarifier showed no corrosivity toward the copper during this test. The mercaptan number of the hydrocarbon product was reduced to 3.8 as an average of 5 days operation. The Saybolt color of the hydrocarbon phase averaged 16.

The water content of the feed and of the product hydrocarbons was determined by the Karl-Fischer methd. The product hydrocarbon phase averaged 65 ppm. of water, which is approximately the saturation limit at about 70 F. The water content of the feed was about 600 ppm.

The product hydrocarbon phase averaged 21 p.p.m. of sodium hydroxide, which indicates that some appreciable amount of sodium hydroxide was picked up from the treating solution during the contacting.

After approximately 40 hours of operation, the aqueous solution in the reactor-clarifier showed a decrease in sodium hydroxide content from about 42% to about 40%; this decrease represents consumption of the sodium hydroxide in reaction with hydrogen sulfide, mercaptans, and by dilution with water removed from the diesel fuel feed.

Over the course of the days, the effect of large variations in feed charge rate on the characteristics of the dispersed liquid system was observed. After preliminary investigation, the first 8 hour continuous run was carried out at a feed rate of 10.4, average, gallons per hour. On subsequent days, the feed rate was increased up to 24 g.p.h. Over this range of thruput, the dispersed liquid system maintained its stability and its ability to produce a. H S-free and haze-free product hydrocarbon.

As the feed rate was increased, it was observed that i the dispersed liquid system expanded in volume, i.e., the

system occupied a greater depth of the vessel. At the highest flow rates, it was necessary to withdraw about one gallon of the dispersed liquid system from the vessel in order to keep the top of the system below the product withdrawal line.

Even at the 24 g.p.h. charge rate, the dispersed liquid system performed its H S removal and haze removal function smoothly with no observable disruption of the characteristics of the system. The only noticeable efiect of the high flow rate was in the increase in volume of Even though the amount of aqueous caustic solution present in the reactor-clarifier was decreased by withdrawal of some of the dispersed lisuid system, there was no detectable difference in quality of the product hydrocarbon as compared with hydrocarbon produced at the lower charge rates.

The dispersed liquid system, which had been withdrawn from the vessel, rapidly settled into an upper hydrocarbon layer and a lower aqueous layer. The hydrocarbon layer was H 8 free and bright. The dispersed liquid system consisted of essentially equal volumes of hydrocarbon and aqueous solution. It is pointed out that the dispersed liquid system, as originally formed within the reactor-clarifier, consisted of 60 volume percent of aqueous caustic solution and 40 volume percent of hydrocarbon.

12 Example 3 In this example, a thermally cracked heavy naphtha was contacted with aqueous caustic cresylate solution to extract mercaptans. For this operation, the pilot plant of FIGURE 1 was modified by the use of a diiierent type reactor-clarifier 81, which is shown in FIGURES 4 and 5. Reactor-clarifier 81 consisted of a Lucite vessel 82 provided with a sloped bottom 83 and a'stainless steel top covering 84. Four vertical bafile strips 86a, 85b, 86c, and 86d were positioned equidistant around the periphery of vessel 82. 4" above the high point of bottom 83 a doughnut bailie plate 88 was positioned across vessel 82. The central aperture 89 of the doughnut baflie plate 88 was 2.5" LD. Reactor-clarifier 81 was provided with a turbine 91 having 6 flat blades 92a, etc.; the overall diameter of the turbine 91 was 2". Turbine 1 was driven through shaft 94 by a H.P. motor, not shown.

Reactor-clarifier 81 was provided with a vent 96 located in top 84. Feed naphtha was passed by way of line 98 into the axial center of vessel 82. The feed naphtha entered about 6" below turbine 91, in this example. The product naphtha phase was removed by way of line 99.

For continuous operation of a mercaptan extraction unit, it is necessary to provide for the withdrawal of mercaptan-rich aqueous caustic solution and for the introduction of mercaptan-lean aqueous caustic solution. The lean aqueous caustic solution, which may be either a freshly prepared solution or a regenerated solution, is introduced into the dispersed liquid system of reactorclarifier 81 by way of line 101. The mercaptan-rich aqueous caustic solution (commonly known as rich solution) is withdrawn from vessel 82 by way of line 162.

Doughnut bafile plate 88 helps to create a compartment for the mercaptan-rich solution which separates from the dispersed liquid system phase. It is to be understood that, in a mercaptan extraction operation with continuous flow, three layers will be present within the reactorclarifier, namely, a top product hydrocarbon layer, a middle dispersed liquid system layer, and a bottom mercaptan-rich aqueous caustic solution layer. A more or less distinct boundary exists between the bottom and middle layers. Bafile plate 88 helps to make for a sharper separation of the two lower layers. In this example, the feed to the reactor-clarifier was a heavy naphtha derived from a thermal cracking operation. The gravity, ASTM distillation, and mercaptan number of the feed naphtha are set out below.

Vessel 82 was charged with 12" of the aqueous solution and about 10" of the feed naphtha. In this example, the aqueous solution contained a total of 20% by weight of sodium hydroxide and 20% by volume of cresols. The contents of reactor-clarifier were brought to about F. At a turbine speed of 350 r.p.-m., the dispersed liquid system formed. In all respects the dispersed liquid system resembled that described in Example 1. After the dispersed liquid system phase had been formed, feed naphtha was charged by way of line 98 at a rate of 10 gallons per hour. A clear, bright hydrocarbon layer formed on top of the dispersed liquid system and this product hydrocarbon was withdrawn by way of line 99. A separate layer appeared in the bottom of vessel 82 consisting of aqueous caustic cresylate mercaptide solution. Fresh aqueous caustic cresylate solution was continuously introduced by way of line 101 at a rate of 1 gallon per hour; rich solution was withdrawn at this same rate.

The product hydrocarbon was clear, bright, haze-free, and had a mercaptan number of 4.4-an average over a six-hour run length. (This degree of mercaptan remov- 81 corresponds very closely to that obtained in a commercial unit on this same feed stock employing about the same aqueous caustic cresylate solution, in a countercurrent tower contacting zone.)

Example 4 In this example, mercaptans were extracted from a thermally cracked naphtha using bench scale equipment. The reactor-clarifier consisted of a cylindrical jar provided with a bottom draw-off. The jar was 6 inches 0.1). and 8 inches outside height. Four stainless steel vertical bafiles /s inch wide and 7% inches tall were positioned inch from the wall of the jar and spaced 90 about the inside of the jar. The agitation was provided by a half-moon paddle, 2 inches in diameter, aflixed to the end of Mt inch stainless steel shaft driven by a H.P. variable speed electric motor. The shaft was 12 inches long. The paddle was positioned in the jar at a point just below the top of the aqueous medium present in the jar, i.e., below the aqueous medium-hydrocarbon interface when no agitation was =being provided.

A 5,000 ml. separatory flask was used as a naphtha feed vessel; a 500 ml. flask was used to withdraw product naphtha by suction. The product naphtha was withrawn from the suction flask.

The feed naphtha had been obtained from the product of thermal cracking of gas oil. This naphtha had an ASTM distillation range from 130 F. to 412 F. with a 50% point of 270 F. The mercaptan contentmercaptan number-was 33.3.

Two runs were made wtih this feed naphtha using different aqueous mediums. In run A, the aqueous medium consisted of 11 weight percent of free NaOl-I, 20 volume percent of cresols present as sodium cresylate, and the remainder water. In run B, the aqueous medium consisted of 14.6 weight percent of free NaOI-I, 32 volume percent of cresols present as sodium cresylate, and the remainder Water.

In both runs, the temperature in the reactor-clarifier was maintained at 110 F. and about 5,200 ml. of naphtha was extracted at a rate of 65 ml. per minute.

Each run was begun by introducing the aqueous medium into the jar to a level of about 3 inches. About an equal amount of feed naphtha was introduced on top of the aqueous medium. The agitation was begun at about 1000 rpm. and the dispersed liquid system was formed. The agitator speed was reduced to about 600 rpm. and a bright, clear layer1" highof naphtha pernnttedto separate. From this layer, the product was removed from the jar. Agitation was continued for 20 minutes before continuous introduction of the feed naphtha was begun; feed was introduced near the bottom of the jar.

The entire product of each run was collected in one vessel. The mercaptan number of this total product was, in run A, 7.6, and in run B, 5.0. This represents the extraction of 78% and 85%, respectively, of the mercaptans charged.

'Example Diiferent methods of forming the dispersed liquid systern were studied using the bench scale equipment of Example 4. Instead of the half-moon paddle, a marine type propeller 2 inches in diameter and three 45 pitched blades, was used as the agitator. The direction of rotation of the blades caused the aqueous medium to be drawn up into the naphtha. The bottom of the propeller was positioned /2 inch above the bottom of the jar.

(a) A series of runs was made where 2 /2 inches of aqueous medium was placed in the jar and 3 /2 inches of naphtha placed on top of the aqueous medium, i.e., a 4060 volume ratio. Three types of aqueous medium were used, namely, straight water; NaOH solution and 25% NaOH solution. A stable dispersed liquid sys- 14 tem was obtained at all propeller speeds over the range from 600 to 1700 rpm.

(1)) Using the three mediums described in (a) above, a series of runs was made wherein 3 inches of aqueous medium were positioned in the jar and agitated by the propeller. Feed naphtha was added rapidly to the agitated aqueous medium through the feed inlet. The stable dispersed liquid system was obtained in each run.

(0) The procedure of (b) was reversed in that 3 inches of naphtha was agitated in the jar and the aqueous medium introduced through the feed inlet. The stable dispersed liquid system was obtained in each run.

(d) Another procedure was tried wherein the propeller was set in rotation in the empty jar and equal volumes of naphtha and aqueous medium were introduced simultaneously at a constant rate into the jar. With all three aqueous media, a stable dispersed liquid system was obtained in each run.

(e) A series of runs was made along the lines of ad above using a kerosene in one series and a virgin gas oil in another series. The results of the kerosene series virtually duplicated the results of the naphtha series.

The dispersed liquid systems formed with the gas oil were somewhat difficult to maintain. This diificulty was overcome completely by adding cresols to the aqueous caustic solutions; with an aqueous caustic cresyiate medium, stable systems were obtained by each of the various procedures described in series a-e.

Example 6 The effects of propeller speed, of the time of agitation, and of the oil-aqueous medium proportions on the most easily measured physical property of the dispersed liquid system were studied, using the bench scale equipment described in Example 4, and the propeller described in Example 5. This most easily measured physical property has been named the settling rate; the settling rate may be described as the rate at which the depth of a supernatant oil layer grows at the expense of the disersed liquid system after the agitator is turned off. It has been observed that, in the absence of a separate supernatant oil layer, the dispersed liquid system does not produce a separate oil layer immediately after the agitator is shut off. (The separation of a supernatant oil layer is also described as settling of the system because the system shrinks in depth.) After an initial period of slow settling, the oil emerges at a uniform rate until the depth of the remaining dispersed liquid system approaches the depth occupied originally by the aqueous medium at which time the rate slows down markedly. For these reasons, the settling rate was timed for a fall-distance which excluded the time for the first /2 inch of oil emergence and the last /2 inch of oil emergence. Usually the settling rate was timed over a fall of 2 inches, i.e., increased depth of oil layer of 2 inches.

The oil component was a thermally cracked naphtha; the aqueous medium was a caustic-cresylate solution containing about 12 weight percent of free NaOH, about 15 volume percent of cresols as sodium cresylate, and the remainder water. The efiect of speed of agitation and of time of agitation was studied with a dispersed liquid system containing one volume of oil and two volumes of aqueous caustic-cresylate solution. All runs were made at about F.

(a) The time of agitation of the dispersed liquid system, at a constant propeller speed of 700 r.p.m., did not appreciably change the settling rate of the system; the settling rate was closed to 0.21 inch per minute over the range of times of agitation from 3 to 20 minutes.

([2) Variation in speed of agitation, over the range of 500 to 1500 rpm, had a negligible eifect on the settling rate. At speeds in excess of 2000 r.p.rn., there was some indication that the setling rate increased significantly, i.e., a change in rate from about 0.22 in./min. to about 0.28 in./min.

(0) At constant agitator speed and time of agitation, the eifect of composition of the dispersed liquid system on the settling rate was great. The results of runs covering a range of oil content from 16.7 to 82.0 volume percent are set out below.

Up to about volume percent oil, there is a very fast rise in settlinge rate. Thereafter, the rate slows down and approaches an approximate straight line relationship, at about oil content. At oil contents above a uniform straight-line increase in settling rate is present.

As the examples show, the exact operation of the contacting method of the invention is afiected by the aqueous medium, the oil, the agitator, the dispersed liquid system composition, etc.

it is to be understood that the above working examples are merely illustrative of the invention and do not limit the scope thereof.

Thus having described the invention, what is claimed is:

l. A continuous method of contacting a feed liquid hydrocarbon with an aqueous caustic medium, which method comprises (a) intermingling liquid hydrocarbon and aqueous caustic medium to form a zone containing a dispersed liquid system characterized by: aqueous medium as the continuous phase, liquid hydrocarbon droplets as the dispersed phasesaid droplets providing at least a substantial part of said dispersed system-and a grease-like appearance and from which a clear, essentially aqueous-medium-free liquid hydrocarbon is readily separable, (b) controlling the intermingling to permit separation of a supernatant layer of liquid hydrocarbon above dispersed system in said zone, (0) passing feed liquid hydrocarbon into a lower portion of said dispersed systern in said zone and (d) withdrawing a clear, essentially aqueous-medium-free liquid hydrocarbon product from said supernatant layer.

2. The method of claim 1 where said hydrocarbon droplets provide the predominate part of the dispersed liquid system. V

3. The method of claim 1 where said hydrocarbon dispersed phase forms between about 50 and 80 percent by volume of said dispersed liquid system.

4. The method of claim 1 where said hazy liquid hydrocarbon is a heavy naphtha.

5. The method of claim 1 where said hazy liquid bydrocarbon is a kerosene.

6. The method of claim 1 where said caustic solution contains between about 10% by Weight and the substantial saturation amount of caustic.

7. The method of claim 1 where said solution contains phenolic compounds.

8. The method of claim 1 where said contacting is carried out at a temperature between about 50 and 150 F.

9. The method of claim -1 wherein said intermingling is accomplished by a means of the type of propeller mixers and turbine mixers and the mixer is positioned within said medium.

10. The method of claim 1 wherein said liquid hydrocarbon feed contains a sufiicient amount of finelydivided aqueous droplets to impart a haze to the liquid hydrocarbon feed and said hydrocarbon product is hazefree.

11. The method of claim 10 where said hydrocarbon droplets provide between about and percent by volume of the liquid dispersed system.

12. A continuous method of contacting a mercaptancontaining feed liquid hydrocarbon with an aqueous caustic solution, which method comprises (a) intermingling liquid hydrocarbon and aqueous caustic solution to form a zone containing a dispersed liquid system characterized by: aqueous solution as the continuous phase, liquid hydrocarbon droplets as the dispersed phasesaid droplets providing at least a substantial part of said dispersed system-and a grease-like appearance and from which a clear, essentially aqueous-medium-free liquid hydrocarbon of reduced mercaptan content is readily separable, (b) controlling the intermingling to permit separation in said zone of a supernatant layer of liquid hydrocarbon above a middle layer of dispersed system and a bottom layer of mercaptan-rich aqueous caustic, (c) continuously passing said teed liquid hydrocarbon and mercaptan-lean aqueous caustic into said layer of dispersed system in said zone and (d) withdrawing a clear, essentially aqueous-medium-free liquid hydrocarbon prodnot of reduced mercaptan content from said supernatant layer and mercaptan-rich aqueous caustic from said bottom layer.

13. The method of claim 12 wherein said feed hydrocarbon is a naphtha.

14. The method of claim 12 wherein said caustic solution contains phenolic compounds.

15. The method of claim 14 wherein said caustic so lution contains between about 10 and 25 weight percent of free NaOH, between about 15 and 35 volume percent of cresols as sodium cresylate and the remainder water.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A CONTINUOUS METHOD OF CONTACTING A FEED LIQUID HYDROCARBON WITH AN AQUEOUS CAUSTIC MEDIUM, WHICH METHOD COMPRISES (A) INTERMINGLING LIQUID HYDROCARBON AND AQUEOUS CAUSTIC MEDIUM TO FORM A ZONE CONTAINING A DISPERSED LIQUID SYSTEM CHARACTERIZED BY: AQUEOUS MEDIUM AS THE CONTINUOUS PHASE, LIQUID HYDROCARBON DROPLETS AS THE DISPERSED PHASE-SAID DROPLETS PROVIDING AT LEAST A SUBSTANTIAL PART OF SAID DISPERSED SYSTEM-AND A GREASE-LIKE APPEARANCE AND FROM WHICH A CLEAR, ESSENTIALLY AQUEOUS-MEDIUM-FREE LIQUID HYDROCARBON IS READILY SEPARABLE, (B) CONTROLLING THE INTERMINGLING TO PERMIT SEPARATION OF A SUPERNATANT LAYER OF LIQUID HYDROCARBON ABOVE DISPERSED SYSTEM IN SAID ZONE, (C) PASSING FEED LIQUID HYDROCARBON INTO A LOWER PORTION OF SAID DISPERSED SYSTEM IN SAID ZONE AND (D) WITHDRAWING A CLEAR, ESSENTIALLY AQUEOUS-MEDIUM-FREE LIQUID HYDROCARBON PRODUCT FROM SAID SUPERNATANT LAYER.