US2447530A - Process for purifying oils - Google Patents

Description

Aug. 24, 1948.

Filed Jan. 5, 1940 R. B. PERKlNs, JR 2,447,530

PROCESS FOR PURIFYING OILS 2 Sheets-Sheet l A fro/Wvg Ys.

Aug. 24, 1948. R. B. PERKINS, .JR 2,447,530

PROCESS FOR PURIFYING OILS Filed Jan. 3, 1940 2 Sheets-Sheet 2 Rooie/CK Pa/mv: d/a,

HARK/5, /f/ECH, F0575@ i HAR/ws A Trae/vins.

the unconsumed reagent viroin `the The present invention is designed to overcome Patented Aug. 24, 1948 .2,447,530 PRCESS FR PURI-FYING `OILS Roderick B. Perkins, Jr.,

to Petrolite Corporation,

Houston, Tex., assig-nor Ltd., Wilmington, Del.,

a corporation of .Delaware Application alfa-nuary 3,

1940, Serial No. 312,222

4 Claims. (Cl. 2011-199) My invention relates to an electrical process and apparatus for removing impurities from voils and is particularly adapted vto .the purication of hydrocarbon oils before or .after distillation.

Oils, such as petroleum or its distillatesVcontain various impurities which Yare more or Y,less susceptible to the action oi chemical :refining agents. In many instances, however, it isdifticult to obtain satisiactoryfcontact between the reiining agent and the impurities, or to obtaina sufficient degree of reaction to effect substantial purication. Again, in many instances, it `is `diiiicult to separatethereacted-impurities and/ or treated '.oil.

these difculties and remove various ,impurities from oils.

In the present specification, the following .deflnitions of general terms willbe used: By hydrocarbon oils, I have reference to `oils Awhich `are composed predominantly of hydrocarbons, such as crude petroleum, coal tar, shale oil, and the like, or fractions thereof which are fluid at ithe temperature of treatment. .By refining agent, I have reference to react with or modify the impurities in the. oil. :By reacted impurities, I have reference to'materials `which separate from the oil, or which .are caused to separate in my process, by virtue'of'the action oi the refining agent on the impurities originally present in the oil. By theiterm gathering agent, I have reference to a liquid present, as a dispersed phase in the oil, at the time .of electric treatment.

General objects of the invention are as follows:

It is an object of my invention -to provide Ya-process and apparatus for the chemical refining of oils whereby impurities therein are subjected to the Vaction of rening agents under controlled conditions leading to the desired degree of -contact and reaction.

Another object ci my invention is to provide a process and apparatus for electrically refining oils in which oils are subjected to the 4action vor an electric field subsequent to their mixturewith a chemical refining agent, whereby aseparation loi the treated oil from the refining agent Rand/ or the reacted impurities is induced, and vwhereby some further refining action may take place.

Another object of myinvention is a process and apparatus for electrically refining cils in which a gathering agent is dispersed into the oil prior to electric treatment and, if desired, at the same time that the refining agent isadded to they oil, whereby reactedimpurities aregathered `a chemical agent adapted to s.;

to provide f specification, I have ,from oils, .either or associated with the dispersed phase in such manner Yas to be eliminated therewith when the Amixture or emulsion is subjected `.to electrical treatment to resolve Athe dispersion.

It is, vfurthermore, Van object of the invention to `provide such a-process in which the oil is maintained in contact with the vdispersed reagent and/or gathering agent during a `conditioning .period prior to electrical treatment, whereby a conditioning eifect is obtained Vwhich may be beneficial both in facilitating the. subsequent electric ytreatment and in increasing the percentage removal of impurities.

Still another important object of the invention ,is `to remove corrosive materials from an oil `by electric treatment, for example hydrogen sulphideormaterials which are potential sources of hydrogen sulphide or other corrosive substances when subjected to heat. For the .purpose of :this grouped, under the term sulphur-containing 4substances, both hydrogen sulphide and thosepotential sources of hydrogen 4sulphide which, upon heating, will liberate this objectionable compound.

Another object of the invention is to treatan oil to remove Asulphur-containing substances. Generally stated, it is an object of my invention 4tolgdecrease the Usulphur content of o ils and/or distillates.

Another object of the present invention is to ,provide a process for refining oil or fractions ythereof withacicls, typically sulphricacid, or with :polymerizing reagentsin general, and more particularly Yto'-,providan improved method for the lremovalfof acidsludges, unused reagent, and the like.

More specic objects oi the invention will be .apparent `from the following general statement of the invention and the subsequent detailed .il-

`lustrations Vand examples set forth.

Ingeneral, the invention resides in treating an impure oil withachemical refining agent adapted to react'with the impurities in the oil, maintainingysuch conditions of.contact as give the desired ,degree of reaction,and then subjecting the `reaction Amixture tothe action of an electric field, preferably of an alternating high potential type, the reaction mixture as subjected to the eld being in .the form of an oil-continuous .emulsion containing a dispersed phase comprising or adapt- -ed to collect reacted impurities and/ or the spent or `remaining `refining agent.

The present process and apparatus are adaptedto the removal of various types of impurities before or after distillation, and

the character of the refining agent is chosen to correspond with the impurity which it is desired to remove. For example, in removing acidic or saponiable impurities, I preferably use an alkaline reagent, such as caustic alkali, alkaline earth oxides or hydroxides, alkali carbonate, alkali phosphate, solutions (usually aqueous and/or alcoholic) of caustic alkali and the like, etc. Impurities of an unsaturated or resinous character can be removed, according to my process, by the use of reagents having a polymerizing or precipitions of HOCl, halogen acids, phosphoric acid, nitric acid, and the like. Such acids may be employed in suiiicient amounts to react with the bulk of the oil. In general, I propose to use refining agents known in the art to react With and remove or modify impurities which are objectionable and, for the most part, my invention is not concerned solely with the character of the reagent but rather with the mode of its use.

My process is of particular value in treating crude oils prior to distillation, and I find that pre-refining, as practiced according to my invention, is advantageous in many respects, among which are the suppression of corrosion of metallic equipment in contact with the crude oil, for instance, the crude pipe lines and, in particular, the stills in which the crude petroleum is distilled into fractions.

The present process present or potential hydrogen sulphide by treatment of the crude stocks before distillation. In other instances, the process can be advantageously used to remove hydrogen sulphide or materials engendering hydrogen sulphide from a hydrocarbon which has previously been subjected to fractionation, for example, one or more of the various fractions obtained from a distillation process.

My process is also adapted to decrease the sulphur content of oils generally, without particular reference to the specific type of sulphurbearing material which is removed. Desulphurizing agents, in general, comprise alkalies, acids, and the like.

In addition, some crude petroleum stocks and some distillates produced therefrom contain various acidic materials which are detrimental to the quality of the distillates, and which may also give rise to corrosion difficulties during distillation. Examples of such materials are naphthenic acids, phenols, and saponifiable complexes yielding such acids on distillation or saponification. Such acidic or acid-engendering materials may be reacted and removed by my process, preferably by the use of an alkaline reagent. Here again, the process is applicable either to a. crude oil or its distillates, and I am able to obtain from crude oils which have been so treated distillates which contain materially smaller quantities of acidic material than would other- Wise be the case.

In some instances, I prefer to perform the process by use of the following steps: first, contacting the impure oil with a reagent adapted to react upon or transform the impurities present in the oil, e. g., dissolved therein; second, dispersing in the oil a phase adapted to collect the reacted impurities and/or the spent or unused reagent, e. g., a gathering agent; third, providing can be used to remove ,hol and are thus not subjected to the a suflicient conditioning period during which the character of the dispersion may be modified and during which further reaction with impurities may take place; fourth, subjection of the treated oil containing the dispersed gathering phase to the action of an electric field, preferably a high potential alternating field; fifth, separating the purified oil from the gathering phase and the impurities associated therewith.

Various of these steps may be combined into one step, or their order may be changed, or one 0r more steps may be omitted entirely, as hereinafter set forth. In many instances, I nd it advantageous to combine the first two steps. For example, in treating an oil to remove acidic and acid-engendering compounds, I may use a caustic alkali as my reagent and Water as my collecting agent, and add them simultaneously to the oil in the form of an aqueous solution of caustic alkali. This aqueous solution is dispersed in the oil, preferably under conditions which are favorable to the formation of an oilcontinuous emu-lsion, for example, at temperatures not substantially above atmospheric temperature. Some or all of the desired reactions may take place in this step. This dispersion may then be conditioned by maintaining it, usually at an elevated temperature, either in a quiescent state or With agitation for a period sufficient to condition it for electric treatment, usually for a period of an hour or more. During this conditioning period, additional desired reactions may take place, namely, reactions of the reagent upon the impurities and the conditioning of the emulsion for subsequent steps.

As an alternative to the process just described, I may add the reagent directly to the oil. For example, in the case just illustrated, I might have added a very concentrated solution of caustic alkali to the oil, preferably With suicient mixing to insure good contact, and might have thereafter dispersed a gathering agent, such as water, in the oil thus commingled with the concentrated caustic alkali. Again, I may add an oil-soluble, or partially oil-soluble, reagent to the oil, for eX- ample, an alcoholic solution of caustic alkali, and thereafter disperse water in the oil thus treated. Various other methods can be used for adding the rening agent and the gathering agent to the oil.

In some instances, it may be advantageous to reverse the sequence of the first steps mentioned above. Thus, the Water may be added to the oil and dispersed therein, an emulsifying agent beif desired. The emulsion thus formed may then receive the rening agent.

In some instances, I may partially separate the impurities before proceeding to the final separating stage. Thus, I may add alcoholic KOH containing sufcient alcohol of an appropriate strength to form a dispersed alcoholic phase. All or a portion of this phase may be then separated from the oil as by an electrical process, or by other means, and the oil thus treated then commingled with water to form a water-dispersed emulsion which is then subjected to the further steps of separation. This mode of operation is of particular advantage when it is desired to avoid any return of impurities to the oil by the diluting effect of the Water. Thus, high molecular weight alkali reacted mercaptans, in the example illustrated, are removed with the alcohol due to their solubility in the concentrated alcoprecipitating and/or hydrolyzing action of the water.

ing added or present,

The substantial separation of reacted impurities prior to contact with water is of special advantage in rening with acids or polymerizing agents in general. The dilution of acid sludge with water tends to throw out an unstable oily material which is highly detrimental to the quality of the treated oil if it is allowed to mix therewith. I nd that such acid-sludges are coalesced by 4electric action with great rapidity and completeness, thereby rapidly terminating contact between the oil and sludge particles. The electrically desludged oil may then be treated with water or other gathering agent and subjected to further coalescing electric fields, whereby additional impurities are removed to produce an acid-renned oil of superior quality.

The gathering or -collecting agent is a material which is either immiscible with the oil or, atleast, suiiciently immiscible to form a separate second phase in the presence of the oil. It is, furthermore, a material which is adapted either to .dissolve the reacted impurities or to associate with the reacted impurities in such a manner, for example, by adsorption of these impurities at the interface, as to remove the reacted impurities from the treated oil in the final step of separation. It is not necessary, however, that all of the impurities be removed in this fashion, for some of the impurities may have been merely modied by the reaction into inoiensive oil-soluble compounds which still remain in the oil. As stated aboveby reacted impurities I mean those impurities which have been so changed that they dissolve in, or become associated with, the gathering or gathering agent. rlhe collecting agent may furthermore aid in the separation of the spent reagent from the treated oil. Water and alcohol have .been illustrated as suitable gathering or collecting agents, but I do not wish to be limited to these materials.

In many instances, the gathering or collecting agent will form a suitable oil-continuous emulsion with the oil. In other instances, I iind it advantageous to add a modifying agent to insure the formation and suitable stability of the desired oil-continuous emulsion. Such modifying agent may be any of the well known class ot emulsifying agents which promote the formation of oilcontinuous emulsions, for example, alkaline earth soap and the like. In still other instances, I may keep the disperse phase suspended by continuous agitation or turbulence until the dispersion is subjected to the action of the electrical rleld or other separatory means, and thereby make use of dispersions which are so unstable as to rapidly separate on standing.

In operating on crude oils, I usually find it unnecessary to add any emulsifying agent of the type described. On distillates, however, and in particular the lighter distillates, it is sometimes impossible to obtain a satisfactory emulsion without the aid of an emulsifying agent of the type described. In the case of heavy lubricating oil distillates or of long residuums, there are frequently present sufficient amounts of naturally occurring asphaltic bodies to aid in the formation of the desired emulsion. I may, if desired, however, add a small amount of an emulsifying material to a distillate or lubricating oil distillate in order to bring this effect into greater prominence.

The conditioning step, wherein the dispersion of the gathering agent in the oil is allowed to age, and wherein further reaction between the refining agent and the impurities may take place, is an advantageous and, in many instances, a

necessary step, although under certain circuiti# stances it may be omitted or shortened to merely a nominal period. During this period, a change in the character of the emulsion usually takes place, the mechanism of which is obscure and not understood, the rst effect of which is usually to increase somewhat the ease with which the emulsion may be treated or broken by the action of the electrical iield.

The second conditioning eiect which involves further reaction of the reagent with impurities may or may not be of importance, depending upon the character of the refining agent used and on the character of the impurities to be removed. When a rapidly reacting reagent has been used, the additional refining effects, as induced by the conditioning period, are small or even negligible. However, in certain other instances, the desired eiects are obtained only in conjunction with the conditioning period.

In separating the components of the conditioned emulsion so as to obtain the purified oil on the one hand and the reacted impurities and gathering agent on the other, I prefer to employ the action of a coalescing electric eld, preferably a high potential alternating eld. Among other things, this iield produces a separation or resolution of the components of the emulsion, or it at least so changes the character of the emulsion, as by partial coalescence of the droplets, that the components thereafter rapidly settle by gravity. In addition to these effects, however, I ind further unexpected effects arising from the action of an electrical eld which make f it particularly applicable to the separation of the emulsions as produced by my process. These effects, which are not well understood in their character or mechanism, are manifested by the greater degree of purication which is usually obtained when the electrical field is used than when other methods of separation are relied upon.

Various explanations may be advanced for the beneiicial eiiect of the electrical eld. There is some evidence tending to show that an electrical eld is more selective in its action on very small droplets highly charged with impurities than are other methods of separation. On the one hand, the smallest droplets are most highly charged with impurities because of their high surface-tovolume ratio which results in the small drops producing a greater amount of interfacial reaction with respect to their quota of reagent than is produced by the larger drops. On the other hand, the smallest droplets are those most difficult to separate when gravitational methods of separation are relied upon solely, as in the case of separating by settling or by centrifugi'ng.. In ordinary methods of separation, therefore, these small droplets, which are heavily charged with impurities, are separated with diiiiculty or not at all. In using an electric eld, however, I nd that these small impure droplets are very substantially removed from the oil.

Moreover, the eiect does not seem to be one which can be explained merely upon the basis of a greater degree of resolution, since, in many instances, I i'lnd that, when the emulsion is separated to the same extent, i. e., to produce a puried oil of the same Water content, by an electrical process on the one hand and a gravitational or centrifugal process on the other, the emulsion treated by the electrical field will be found to contain less impurities than the emulsion of the same water content separated by gravitational or centrifugal separation. This may arise from a selecf aumen tivek tendency of the very small impure droplets to coalesce with larger droplets under the action of the electric field so that whatever droplets of water are retained in the emulsion are substantially less concentrated in impurities than those selectively acted upon.

Referring to the drawing,

Fig. l illustrates a pipeline diagram of a system embodying my invention, with the electric treater shown in elevation.

Fig. 2 illustrates a diagram alternative to part of Fig. 1.

,Fig 1 is illustrative of a flow sheet adapted to the use of an aqueous reagent capable of serving as a gathering agent. Referring particularly to Fig. l, the numeral Ill indicates atank for storage of the hydrocarbon, and I indicates a tank containing the aqueous reagent. If desired, this reagent can be mixed in the tank I| by introducing proportioned quantities of water and chemical through pipes I2 and I3 and mixing these by any suitable means, such as an agitator |4.

Pumps I6 and respectively pump the hydrocarbon and reagent from .tanks I and |I and may develop sufficient pressure to force these constituents into or through the conditioning means to be hereinafter described.

Heaters I8 and I9 may be used to heat the liquids before mixing if such heating is desirable. Various types of heaters can be used, the ones shown being of the tube type provided with headers 2i) and 2| between which extend pipes 22 for carrying the liquid to be heated. Steam or other heating medium can be circulated through the space between the headers and around the tubes 22, being introduced, for instance, through a pipe 23 and withdrawn through a pipe 24.

The hydrocarbon through a pipe 21, be introduced into carbon through a is formed when together.

If desired, this preliminary mixture can be further heated by moving through a heater 30 similar -to the heaters I 8 and I9 previously described. Alternatively, it can by-pass this heater flowing ythrough a pipe 3| when a valve 32 thereof is opened and a valve 33 inthe pipe 21 is closed. During now through such a heater 30, some additional mixing may take place due to turbulent ilow conditions therein.

To further mix the hydrocarbon and aqueous reagent, the preliminary mixture may move from the heater 32 by means of a pipe 34 through an emulsifying means 35. Various types of emulsifying means can be used to form the desired type of emulsion, such as baiiie mixers or spring-loaded valves. An emulsifying means which has been found particularly advantageous is illustrated and comprises a weighted valve, such as shown in detail in the patent to Harold C. Eddy No. 2,182,145.

The resulting emulsion moves through a pipe i5-to a header 46 and thence to one or more of a plurality of conditioning means. Three of these conditioning means are indicated by the numerals 56, 5|, and 52, and the resulting emulsion can be moved into one or more of these by proper control of valves 53, 54,'and 55.

The simplest form of conditioning means includes a tank 5l into which the resulting emulsion is discharged and in which this emulsion is permitted to stand for the desired conditioning period. The conditioning means 5l), 5| and moves from the heater |8 and the aqueous reagent may a flowing stream of this hydropipe 28. A preliminary mixture these liquids are thus brought 52 may be supplied with suitable stirring means, not shown, which can be continuously operated or put into operation just before the conditioned emulsion is withdrawn. However, such a stirring means is not always essential to the process.

It is often desirable that the emulsion be conditioned at elevated temperature. To prevent excessive cooling of the emulsion during conditioning, or to add additional heat thereto, a jacket 58 may be provided around each tank 5l. A hot medium may be circulated therethrough by use of pipes 59 and '60. In other instances, the heat initially in the resulting mixture may be conserved by heat-insulating each of the tanks 57. In other instances, such heating or heat-insulating may be dispensed with, allowing the mixture to cool slightly during the conditioning step.

Various other conditioning means may be employed instead of the illustrated system of tanks. For example, the conditioning means may comprise an elongated tank with an intake connection at one end and a discharge connection at the other end, of such a capacity that the emulsion in its flow therethrough is properly conditioned; i. e., the time consumed in the travel through the tank corresponds to the desired conditioning period. If desired, such a tank may be provided with Stirrers or other agitating means, preferably used in connection with baiiles designed to prevent indiscriminate mixing of conditioned and unconditioned emulsion. Such a tank may be elongated either vertically or horizontally, and, ii desired, a plurality of such tanks may be used. either in series or in parallel,

A horizontally elongated tank serving as a conditioning means is shown in conditioner |23. This conditioner comprises a horizontally extended inner pipe |24 closed at the ends and surrounded by a steam jacket |25. The inner pipe |24 is provided with a plurality of baille means such as baille |28 intermediate which are a plurality of paddle means such as paddle |21 rotatable by a shaft |26. The shaft extends beyond one end of the conditioner, and the extended portion is keyed to a pulley |29 whereby it may be suitably driven.

The unconditioned emulsion is brought to the conditioner |23 from the header 46 by means of valve |2| yand line I 22, the latter opening into one end of the interior pipe |24. The conditioned emulsion is withdrawn from the other end of the conditioner through a pipe |30 provided with a valve |32, and conducted into the line |42. The conditioner |23 is shown broken in the middle; the unindicated horizontal extension should be such as to give the conditioner a total volume substantially equal to the rate of flow of the emulsion multiplied by the desired conditioning period.

The elongation of the passageway in which conditioning takes place may, if desired, be emphasized to such a degree that a turbulent now is occasioned bythe diminished cross section of the passageway. The cross section may be chosen in such relation tothe rate of flow of the emulsion that turbulent flow is induced to a degree which insures the maintenance of the emulsion or mixture in the desired state of uniformity.

The conditioned emulsion may be withdrawn from the plurality of conditioning means 50, 5|, and 52 shown in the drawing in succession, or it may be simultaneously withdrawn from two or more of these means. As shown, a pump 62 may be utilized for withdrawing the conditioned emulsion from any or all of the conditioning means,

as determined by the settings of the valves concerned. The pump 32 may be dispensed with in some instances, or by-passed by a valve |48, utilizing the pumps |6 and |1 for the purpose of forcing the emulsion through the conditioning means and thro-ugh a pipe 61 into an electric treater 1B. However, if used, the pump 62 may serve to further emulsify the constituents of the conditioned emulsion.

In some instances it is desirable to re-heat the conditioned emulsion before passing it to the electric treater, or to raise it to a higher temperature than the conditioning temperature for the purposes of electrical treatment. To do this I may close a valve |33 in the line |42 and open a valve |35 leading to a heat interchanger |35. rIhe conditioned emulsion is brought to the desired treating temperature therein and thence conducted by means of lines |31 and |38 to a point in the line |52 beyond the valve |33, at which point it is picked up by the action of the pump E2. If desired, the pump 62 may be bypassed by closing the valve |315 and opening the valve M3, the emulsion then passing through the line |33, valve |43, and line IM into the line 61 entering the treater.

Various types of electric treaters can be used, the type of electrical treater shown in the Eddy patent, supra, being particularly advantageous. As the details of this tre-ater are not. per se, a part of the present invention. no detailed description will be here given. Suffice it to say that this treater includes a closed tank 1| and performs the dual functions of coalescing the dispersed water droplets in the conditioned emulsion and separating the coalesced masses to leave a purified hydrocarbon. It will be clear, however, that these functions can be performed in separate means, if desired.

As disclosed in the patent to Eddy, supra, the treater inciudes suitable live electrodes for establish-ing a main neld. as well as one or more auxiliary fields, one of the auxiliary fields being bounded by the body of coalesced aqueous material. indicated by the numeral 91, which separates following electric treatment and which provides a rather definite surface, indicated by the numeral S8.

It is often desirable to use two or more emulsifying means successively. If desired, the means for discharging the emulsion into the main eld may be utilized as one of these, or as supplementary thereto, to eifect a final emulsiiication just before the emulsion is subjected to the action of an electric eld.

The action of the one or more electric fields is to treat the emulsion to effect separation, e. g., to coalesce the dispersed droplets into masses distributed in the oil and of size sufficient to cause them to settle from the oil to form the body 31. The treated hydrocarbon will occupy the space in the tank 1| above the body 91.

The action of the electric field or fields is several-fold. In the first place, it may cause additional portions of the sulphur-containing materials to become associated with the aqueous reagent. In the second place, it coalesces the dispersed aqueous droplets. In the third place, this coalescing action may be particularly eiective with regard to the small droplets highly charged with impurities, `especially under the alternating electrostatic stresses induced by the use of an A. C. type treater. The coalesced masses thus contain sulphurous materials or other reacted l0 impurities which were originally present in the hydrocarbon.

The coalesced aqueous material can be continuously or intermittently withdrawn from the lower end of the tank 1| through a pipe H0, as controlled by a valve Similarly, the purified hydrocarbon can be continuously or intermittently withdrawn through a pipe ||'2 as controlled by a valve ||3 and may move to suitable storage or directly to the stills if desired.

Fig. 2 illustrates a diagram which is alternative in part to Fig. 1, and is illustrative of the practice of my invention when using separate refining agents and collecting agents. The diagram of Fig. 2 is designed to replace or be alternative to that portion of the diagram in Fig. 1 which is ahead of valvesl 33 and 32.

Referring more particularly to Fig. 2, the tank i contains impure oil which is picked up by the pump l5 and passed through the heat interchanger I8 to bring it to the desired temperature. The tank is a tank wherein the refining agent is compounded or stored and is provided with a paddle I4 whereby such chemicals as are introduced through the pipes l2 and |3 may be properly mixed. The reagent is picked up by the pump and passed through the heat interchanger I3 wherein it is brought to the desired temperature. A tank |53 is designed to contain the icollecting or gathering agent, such as water or alcohol or mixtures thereof, or any of these in combination with a modifying agent. The constituent parts of the gathering agent may be added through pipes |5| and |52 and mixed by means of a paddle |53. The gathering agent is picked up by means of a pump |55 and passed through a heat interchanger |55 to bring it to the desired temperature.

When it is desired to subject the oil to the action of the reining agent prior to the introduction of the gathering agent, a valve |62 is opened and the refining agent is brought from the heat interchanger i9 through lines |60 and IBI into the stream of oil owing from the heat interchanger Iii through the line |65. With a valve 51| in the line |65 opened, the commingled stream of oil and reagent is brought into the conditioner |23, the structure of which may be identical with that previously described in connection with Fig. l.. The commingled streams may be passed therethrough either with or without the application of heat arid/or` agitation, depending upon the conditions desired for the refining action. If desired, the conditioner |23 may be made very small in dimensions, serving under such circumstances more as an agitating means than as a conditioning means. If desired, the conditioner |23 may be by-passed entirely by opening a valve |12 and closing the valve |1l.

The conditioned or by-passed dispersion of reagent in oil then enters a line |13 and, after passinig a valve |14, is commingled with gathering agent introduced through a line |53 and valve |51. If desired, partial or substantial separation of the dispersed refining agent and/or reacted impurities may be caused to take place prior to introduction of the gathering agent. Thus the valve |14 may be closed and a valve |15 opened, whereby the dispersion of rening agent in oil is brought by means of a line |16 into a decanter |30 comprising a down pipe |82 for the entering set- The oil rising to the top of the less freed from reagent the settling thereof,

emulsion and a closed shell |8| defining a tlirtg space. shell |8|, being more or and/or reacted impurities by is removed by means of a line |84 having a valve |85 into a line |86 communicating with the line |13 at a point beyond the valve |14. This partially settled emulsion is then scommingled with a gathering agent as before, if desired.

If desired, a dispersion of reagent in oil may be substantially freed from reagent and/or reacted impurities prior to contacting it with the gathering agent by means such as electrical precipitation. An electric treater |92 is illustrated very schematically in Fig. 2 and may be of a type similar to that shown in the patent to Eddy, supra. By closing the valves |14 and |15 and opening a valve |90 in the line I 16, the dispersion of reagent in oil is brought through a line I9I into the electric treater |92 wherein the reagent and/or reacted impurities are caused to settle out by the action of the electric field. The treated oil is removed through a line |94 having a valve |95 into the line |96, and thereafter treated With the gathering agent as described above.

The materials settling in the decanter |80 may be removed continuously or intermittently through a line |83, or the materials settling in the treater |92 may be removed continuously or intermittently through a line |93.

When it is desired to introduce the gathering agent into the oil prior to the introduction of the reagent, the valve |51 may be closed, and the gathering agent may be pumped through the line |58 into the stream of oil iiowing through the line |65, the valve |59 being open. The commingled stream may be agitated and/or conditioned in the conditioner |23, or it may be bypassed around this conditioner.

Reagent is introduced to the dispersion thus formed by opening the valve |63, the valve |62 being closed, and conducting the reagent through the line |64 into the stream of oil containing dispersed gathering agent flowing through the line |13.

In the case of any of the tives, or of others which will be apparent from a consideration of the diagram, a dispersion of gathering agent in oil is finally introduced into the line 21 controlled by the valve 33 and communicating with the line 3| controlled by the valve 32. From this point the handling of the mixture is such as was described and illustrated in connection with Fig. 1.

It has been found that the process in general parted from, of the various steps.

As previously stated. the process may be used with any suitable refiningr agent. and the modifications which may be desirable accordingr to the various characters of the refining agent will be obvious to those skilled in the art. For the purposes of exposition a more detailed discussion of the refining steps in my process will be limited to the use of an aqueous alkaline solution for the removal of hydrogen sulphide, both present and potential, here classed together as sulphur-containing materials, and various acidic and acid-engendering materials such as mercaptans, phenols, naphthenic acids. and saponifiable complexes of the latter. Furthermore, for the purposes of illustration, the discussion will be largely restricted to the use of an aqueous reabove fiow alternaagent in which the refining agent and the gathering agent are jointly present.

In removing such materials, it is desirable that the aqueous reagent be of such character as to have an affinity for the sulphurous or acidic Inaterials, or of such character as to tend to become associated therewith. Best results have been secured from use of an aqueous alkaline reagent. Sodium hydroxide and sodium sulphide have been found particularly advantageous, though materials such as sodium carbonate, potassium hydroxide, potassium carbonate, sodium phosphate, magnesium hydroxide, or other alkaline reagents can be used in this connection. In other instances, various mixtures of these materials can be used, for instance, a mixture of sodium hydroxide and sodium sulphide, or various other mixtures of such materials as mentioned above.v

Partially spent caustic as produced in various refinery operations, as in the caustic washing of gasoline, is quite suitable for this purpose, particularly when the spent caustic contains appreciable quantities of sodium sulphide. In general, the reagents may be either dissolved or dispersed in the water, depending on their solubility.

The concentration of the aqueous alkaline reagent Which I use to remove sulphurous and acidic materials is usually quite low, and 0.1 M solutions have been found very satisfactory. Usually, best results are obtained by solutions from 0.01 M to 0.8 M or 1.0 M. The optimum concentrations from the standpoint of the stability and electric treatability of the emulsions whichv are formed depends on the character of the stock. Thus, with a crude petroleum in which the impurities were predominantly sulphurous materials, a 0.1 M solution of NaOH, whereas with another crude in which the impurities were predominantly naphthenic acids, I obtained best results using 0.5 M NaOH. In the instance of still other crudes, I have found it advisable to use NaOH solutions less than 0.025 M to remove naphthenic acids.

Best results have been obtained by using such aqueous reagents in quantity about 20% by Volume of the hydrocarbon, and the pumps I6 and |1 may be controlled to introduce this quantity of the aqueous reagent into the iiowing stream of the hydrocarbon. However, in some instances, larger or smaller quantities of the aqueous reagent can be utilized, for instance, between 10% and 30% by volume.

It is not always essential to form the preliminary mixture by bringing together flowing streams of the two liquids, though this has been found very convenient. Other mixing means can be utilized in this capacity.

If the oil is very viscous, it may be preferable to have the preliminary mixture at an elevated temperature before it moves through the emulsifying means, though this is not always essential if heat is supplied to other portions of the system. It will be found that good results are obtained by heating the constituents of the preliminary mixture either before or after they are brought together. In general, it is advantageous to emulsify at as low a temperature as the viscosity of the oil permits, in order to avoid a tendency toward the formation of oil-in-water type emulsions which sometimes appears at the more elevated temperatures. In obtaining suitable temperatures, heat can be supplied to the ingredients in the heaters I8 and I9 before form- I obtained best results with.

13 ation of the preliminary mixture, or the preliminary mixture can be heated in the heater 30. In some instances, it has been found possible to apply all of the necessary heat to the individual constituents, by-passing the heater 30 by opening the valve 32 and closing the valve 33.

As to the degree of mixing, it can be said, in general, that this process contemplates a somewhat more intimate mixture than proposed in the Eddy patent, supra. The resulting emulsion must, in all instances, be of such character that the hydrocarbon forms the continuous phase, the aqueous reagent being dispersed therein in the form of droplets. If the incoming hydrocarbon contains a small percentage of water in the form of dispersed droplets, herein-termed original droplets, it is desirable that the mixing action should not be sufficiently violent to cause homogenization. The original water droplets should not be subdivided to any material extent in the mixing step. If such original water droplets are present, the mixing action should be of such character as to disperse in the hydrocarbon droplets of the aqueous reagent or water, or other gathering agent. to coexist with the original droplets, though some combination of the droplets may be allowed to take place in the mixing step. It will be clear, however, that the process is not limited to the treatment of hydrocarbons containing such original water droplets.

The particle si'fe of the droplets in the emulsion discharged from the emulsifying means 35 is not particularly critical, though a heterogeneous particle size has been found to give the best results. In general, however, due to a more intimate mixing action, the average size of the droplets of aqueous reagent will be somewhat smaller than those proposed in the Eddy patent, supra.

It is one of the concepts of the present invention to condition the resulting emulsion before subjecting it to the action of an electric field. This conditioning step, as stated previously, involves essentially an aging of the emulsion which serves several desirable purposes. For instance, it permits additional association of the refining agent and/or the collecting agent with the impurities and better prepares the emulsion for subsequent electric treatment. In general, when using an aqueous alkaline refining agent, this conditioning should extend for a period of one hour or more, and satisfactory results have been obtained by a conditioning period of from one to twelve hours, or somewhat more. With most hydrocarbons, it has been found that a conditioning period of from three to five hours is best. The optimum conditioning time will depend upon the particular hydrocarbon and upon the impurities present therein.

It is usually desirable that this conditioning take place while the gathering agent is dispersed in the hydrocarbon. In at least some instances, however, I prefer to condition the mixture of oil and refining agent prior to the addition of any gathering agent, and, in still other instances, I prefer to add part of my gathering agent prior to the conditioning and part subsequent to the conditioning. In any of the instances leading to further addition of material after the above-described conditioning step, I may use a further conditioning step subsequent to the final introduction of gathering agent.

In some instances, the degree of mixing may be sufiicient to form a sufficiently tight emulsion which will not settle to too great an extent if allowed to stand quiescent during the conditioningperiod. Viff some such settling does take place, the emulsion can be mildly mixed in the conditioning means before being Withdrawn therefrom. In other instances, the emulsion can be gently mixed throughout this conditioning period by use of paddles or agitators in the conditioning zones.

It has also been found desirable, in most instances, to condition the emulsion while at elevated temperature. This temperature may be between F. and 180 F., with an optimum range of from F. to 165 F. A conditioning temperature of F. has been found particularly advantageous on certain hydrocarbons. In maintaining this temperature, the conditioning zones can be suitably jacketed or heat-insulated. In most instances, lower temperatures can be used in the preliminary stages of the process and additional heat applied during this conditioning.

Any number of conditioning zones can be utilized. If the process is to be intermittently performed, it is possible to utilize a single zone. In some instances, a single zone can be used in a continuous process by continuously iiowing the emulsion thereinto and continuously withdrawing the conditioned emulsion from another` portion of the zone. However, the preferred mode of operation provides for the conditioning of the emulsion in a plurality of zones. The emulsion may be supplied thereto in sequence or may be supplied to several of the zones at the same time. The conditioned emulsion can be similarly withdrawn in sequence or from several of these zones.

With hydrocarbons requiring rather low temperatures in the conditioning step, heat can be added to the conditioned emulsion before it is introduced into the electric treater. Desirable temperatures of the emulsion, when introduced into the treater, will vary with different hydrocarbons, but, in general, this temperature will be betwen 120 F. and 180 F.

The conditioned emulsion is forced into the treater at superatmospheric pressure by the pump 62 or by the pumps I6 and Il. If the pump 62 is used, it may be of such character as to further mix the constituents of the emulsion, though, here again, it is not desirable to homogenize or form an emulsion which is characterized by an extremely small p-article size, for such emulsions are often very difficult to treat electrically. As disclosed in the patent to Eddy, supra, a further gentle mixing may take .place in the means through which the emulsion is discharged into the field, if desired, and the expedient of using this gentle mixing immediately preceding introduction into the electric field is often advantageous.

The electrically-treated hydrocarbon will rise to the upper end of the treater tank substantially free from reacted impurities. Usually, the electric treatment will not remove all of the dispersed droplets, and the treated hydrocarbon will usually contain some rather small droplets dispersed therein. The quantity will not be more than a few per cent and usually will be below one per cent and will not interfere with later distillation if it is desired to remove fractions from the treated hydrocarbon by the use of conventional stills or fractionating means. The treated hydrocarbon can be moved directly to such a fractionating means or it can be moved to storage and withdrawn as desired for subsequent treatment. If thus stored, some additional quantities of the refining agent and/or gathering agent may separate therefrom during storage.

Electric fields of the alternating current type are preferred in effecting this coalescence, though the process contemplates the use of any electric field which Will coalesce the dispersed droplets. Various wave forms can be used in establishing such an electric eld, but the simplest system involves the use of one or more transformers. In the electric treater of the patent to Eddy, supra, Very satisfactory results have been obtained by using transformers which will each develop a potential of 12,000 volts. This will establish a potential difference across the main treating space of 24,000 volts.

By way of illustration and without intent of limiting the invention thereto, the following examples will be given:

Example I A certain crude stock containing substantially no hydrogen sulphide was tested and found to evolve, upon distillation at 600 F., 23.6 grams of hydrogen sulphide per barrel. This crude stock was emulsified with of 0.1 M sodium hydroxide and allowed to stand at 140 F. for three hours to condition the emulsion. A centrifuge test on the resulting emulsion showed B. S. (bottom settlings). The temperature of the conditioned emulsion was raised to 150 F., and the emulsion was electrically treated at this temperature. A centrifuge test was made on the purified hydrocarbon and showed only 0.5% B. S. This purified hydrocarbon was distilled, and it was found that only 9.4 grams of hydrogen sulphide per barrel were evolved at 600 F., a reduction of 60.2% in the amount of hydrogen sulphide evolved during distillation.

Ensamble II Another crude stock was tested and found to contain 4.9 grams of dissolved hydrogen sulphide per barrel and to evolve 73.3 grams of hydrogen f sulphide per barrel when heated to a temperature of 660 F. After treatment by the process herein-disclosed, it was found that the treated hydrocarbon contained no dissolved hydrogen sulphide and that, up to a temperature of 660 F.,

the evolution of hydrogen sulphide was reduced by 53%. In this example, the aqueous reagent was a 0.1 M sodium hydroxide solution, and one volume thereof was dispersed in four volumes of the crude oil. This emulsion was conditioned by allowingr it to stand at 160 F. for three to five hours and was electrically treated at 140 F.

Example III A crude petroleum yielded lubricating oil fractions on distillation which had acid numbers from 1.1 to 1.3 mg. KOH per gram, arising from the naphthenic acid content of these distillates. When the crude oil was treated according to my process, using a. caustic soda solution about 0.5 molal in NaOH as the refining agent, and then distilled, the lubricating oil distillates thereby obtained showed acid numbers of 0.05 or less, corresponding to a reduction in naphthenic acid content of about 95%. The naphthenic acids could be recovered from the spent alkali solution by acidification.

Various combinations of the steps described above may be frequently practiced to advantage. Thus, for example, a petroleum fraction may be successively treated with sulphuric acid and aqueous caustic alkali, the treatment in each instance involving dispersal of the reagent into the oil and its subsequent removal together with reacted impurities, this removal being best accomplished by subjection of the dispersion to the action of an electric field. If desired, the electric removal of acid sludge may be immediately followed by dispersal and subsequent coalescence in the desludged oil of a gathering agent, typically water, and a similar treatment with water may -be employed as a final step subsequent to removal of the caustic alkali.

This application is a continuation-in-part of my copending application, Serial No. 200,098,A filed April 5, 1938, which contains claims to the process when employing alkaline reagents.

It will be clear that various changes and modifications can be made without departing from the spirit of this invention as dened in the appended claims.

I claim as my invention:

l. A process for removing from a hydrocarbon oil impurities capable of reacting with an acid to form reaction products, which process includes the steps of: mixing with an oil containing said acid reactable impurities a sufficient amount of said acid to react with said impurities, said mixing being of sufficient intensity to form an emulsion of the oil continuous type and to disperse the acid throughout the oil to provide droplets thereof for reaction with said impurities and to produce a dispersed phase of said emulsion comprising reaction products; substantially completely resolving said emulsion by subjecting same to the action of a high-voltage electric eld of suficient intensity to coalesce the dispersed phase thereof; separating the coalesced material from the oil while containing said reaction products, whereby said reaction products are recovered from the oil in association with the separated material; and emulsifying an alkaline solution into the oil from which said coalesced material has been separated and then electrically coalescing and removing said alkaline solution from the oil.

2. A process for removing from a hydrocarbon oil impurities capable of reacting with an acid to form reaction products, which process includes the steps of: mixing with an oilcontaining said acid reactable impurities a suflicient amount of said acid to react with said impurities, said mixing being of sufiicient intensity to form an emulsion of the oil continuous the acid throughout the oil to provide droplets thereof for reaction with said impurities and to produce a dispersed phase of said emulsion comprising reaction products; substantially completely resolving said emulsion by subjecting same to the action of a high-voltage coalescing electric field of sufficient intensity to coalesce the dispersed phase thereof; and separating the coalesced material from the oil while containing said reaction products, whereby said reaction products are recovered from the oil in association with the separated material, said acid being added in the form of an aqueous solution and the mixing being performed in the presence of an added emulsifying agent of the type tending to stabilize a water-in-oil emulsion.

3. A process for removing from a hydrocarbon oil impurities capable of reacting with an acid to form reaction products, which process includes the steps of: mixing with an oil containing said acid reactable impurities a sufficient amount of strong acid to react with said impurities, said mixing being of sufficient intensity to form an emulsion of the oil continuous type and to disperse the acid throughout the oil to provide droplets thereof for reaction with said impurities and type and to disperse land like hydrocarbon oils to remove impurities therefrom, comprising: elnulsifying sulphuric acid in the oil in amount sufficient to react with said impurities but insufficient to react with the bulk of the oil; maintaining the acid in a dispersed state for a predetermined period sucient to eiect reaction with said impurities; subjecting the emulsion at the end of this period to the action of a high-tension electric eld to effect substantial coalescence of the reaction products including sludge; separating these coalesced reaction products to produce a desludged oil; emulsifying an alkaline aqueous solution containing alcohol in the desludged oil to react with acidic impurities therein; and subjecting thc emulsion thus formed to the action of a hightension electric field to coalesce the aqueous phase and produce a rened oil.

RODERICK B. PERKINS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 987,115 Cottrell Mar. 21, 1911 1,540,929 Coblentz June 9, 1925 1,931,725 Girvin Oct. 24, 1933 2,119,899 Woelin Mar. 15, 1933 2,126,867 Brewer Aug. 16, 1938 2,133,457 Lemmon Oct. 18, 1938 2,182,145 Eddy Dec. 5, 1939 Certificate of Correction Patent N o. 2,447,530. August 24, 1948.

RODERICK B. PERKINS, JR.

It is hereby certied that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 65, for "Water-dispersed read water-disperse; column 5, line 35, for the Words gathering agent read collecting agent; same line for collecting agent read gather/ng agent;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 21st day ofDecember, A. D. 1948.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,447,530. August 24, 1948.

RODERICK B. PERKINS, JR.

It is hereby eerted that errors appear in the printed specification of the above numbered patent requiring correction as follows: ""r

Column 4, line 65, for Water-dispersed read water-disperse; column 5, line 35, for the Words gathering agent read collecting agent; same line for collecting agent read gathering agent;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 21st day ofLDecember, A. D. 1948.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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