US2373645A - Hydrocarbon sweetening - Google Patents

Description

April 17, E. H. BENDER 2,373,645

BYDROCARBON swnm'aume Filed 001;. 28, 1 941 SEPARATING GASOLINE CENTRIFUGAL mxme PUMP MOTOR I COPPER SOLUTION IINVENTOR ELMER H.' BENDER Patented Apr. 17, 1945 Elmer H. Bender, Phillips, Tex, assignor to Phillips Petroleum Company, a corporation of Delaware Appl cation center 28, 1941,seria1 No. 416.876

new

i 2 Claims.

This invention relates to the sweetening of gasolineiand other petroleum hydrocarbon oils and "comprisesan improved process ofearrying out the sweeteningoperation and apparatus for carrying out this" process. More particularlythe invention Qrelates to improvements in the' sweetening of gasoline by the cupric chloride solution method showninschulze'et al., U. s. 1,964,219,

and in Henr et al., U; s. 2,089,373. I In'the sweetening of gasoline or the like by the so-called liquid copper sweetening process,

the sour? gasoline is intimatelyand vigorously contacted with an aqueous solution-oi acu pric salt, usually copper sulfate, and a soluble chloride such as sodium chloride, to convert the mercaptan content of the gasoline to the, 165. objection'able, substantially odorless disulfides. .The

mixture'is then'allowed to settle and, separate,

whereupon the bottom layer of aqueous salts is removed from the upper gasoline layer. Usually the sweetened gasoline layer is next contacted with a stabilizing agent such as an alkaline sodium' sulfide solution which serves to remove anyv traces oi' cop'per compounds and prevents any color instability or other deterioration of the prrieil ct' The copper sweeteningagent is regenerated by blowing with a free oxy en-containing gas such "as air; and recirculated for furtheruse. a Certain gasolines or hydrocarbon oilsv are difficult to sweeten by the conventional copper sweetening method described above. This; is believed to be due largely to the concentration. and type of ner i aptan sulfur contained in these oils which prevents conversion thereofin the ordin p oc s l c a g SinceQthe sour oils and the aqueous, copper treatingflsolution are immiscible, it is necessary to Qobtain intimate contact therebetweeno while atthe same time preventing too fine asubdivinary commercial installation of the copper sweet I S gn of :the' oil and the sweetening solution. .A

centrifugal mixing pump is generally employed v,to effect the contact in the normal installation. Obviouslythe time of contact in such, a pump a is 'necess arily oi limited durationll, Y

the treatment of oils which are diificultto fi fi flhl hav o i o be m o s bl -to effect il eel f on a t for a su i enti peeftoi render these oils sweet to the standard doctor test, using the, conventional sta ps bm wm ap aratus, i inthe treatment of ordinary oils; very swe tening efictin 'the' period tr tanner time not it T is diflicult to attain the: desired conventional centrifugal mixing pump, or equivalent eontaotor, installed in the conventional manner; to effect the contact between the sour oil and the"; copper sweetening solution. I

object of the present invention is to improve the efiectiveness of knownliquid copper sweetening processes. v I

Anotherobject' is to increase variety of types of sour hydrocarbon oils susceptible to sweetening by liquidacopper sweetening processes.

' Still another object is to increasethe time of contact between the sour oil and the copper sweetening solution. 1;

Another object is to provide an: improved liquid coppersweetening process. Another object is tolprov'ide improved apparatllSFfOl. carrying out this improved liquid copper sweetening-process,j

Numerous other objects will be apparent-from aconsideration of1 the, fOlloWing detaileddescription of; apreierred embodiment oflthe present invention, taken inconnection with the accompanying drawing; in which the figure illustrates diagrammaticallywone form ofapparatus of the v sour gasoline into the circuit by one line, introducing copper solution into the circuit bya separate line, and withdrawing a predetermined portion of the mixture preferablyat a point inlthe circuit justjbefore the point where the fresh-sour gasoline is introduced, the whole process beingconducted continuously. In the endlessycircuit referred to, a portion of the mixture ,is ,re-circu- 5W; a i n i vdepending u n" e ,amountoi fby passing employed; Preferably, also, the pointrof withdravval ofthemixture to the separating tank from the endless circuit is located, at a point, well removed from the point 'ormtr'edu non of the copper solution, the latter point'being w'ellremoved from the pointoi intro ductionoi th'egasoline.v I l} I n a some' hat' more specific aspect, the lnvention involves the considerations "set rennin the preceding paragraph and, in additionlthe interposition' or aj relatively long, relatively large, low velocity mixing zone between the pointrwhere the by-passed mixturejoins the-jincoming sour gasolineand the point where the cop i'sblundn enters th'e'circuit. .1 j I Referring particularly to the accompanying drawing, a motor driven centrifugal mixing pump is indicated at I and a separating tank at 2, in which gravity separation of the treated oil and the copper solution takes place. Sour oil to be sweetened enters the system through line 3, controlled by valve 4, at a point on a level with or higher than {tank J2, and flowsv downwardly through an expanding connector 5' into a line 6 of considerably larger internal diameter than line 3, line 6 preferably having a diameter at least twice that of line 3 in order that the velocity in line 6 may be relatively low. 7

The copper treating solution is fed into line 6 via line 1 controlled by valve 8; Line 1 enters line 6 at a point 9 closely adjacent the bottom of the relatively large line '6 near the inlet, of

Dump I.

The outlet side I I of pump I, which is relatively large, discharges into relatively small vertical line ID, connected to the outlet of pump I by means of reducer I2. Line I!) discharges into the separating tank 2. Line If) is provided adjacent its lower end with valve I8 which with valves I, 8 and I4 is employed to proportion the relative amounts of gasoline entering via v3 and of copper treating solution entering via 1.

A by-pass line I3 connected to line ID at point I6 and controlled by valve I4 places line ID in communication with line 3 at a point I5 above the reducer 5. I

In operation, sour gasoline is charged to the system through line 3 and passes downwardly through reducer 5 into the top ofv line B, where its velocity is considerably reduced. At it passes by the point IE, it is mingled with by-passed mixture entering through line I3. The mixture entering line. 6 has its velocity materially reduced as it enters, and passes relatively slowly downwardly under the combined influence of gravity, the suction of pump I, the pressure on the material in line I3, andthe pressure on the entering sour gasoline. [As it thus passes downwardly in line 6,

the entering sour gasoline is intimately agitated and commingled with the by-passedmaterial and especially with the unspent cupric compound in the aqueous. phase thereof, causing an initial reduction of mercaptan content to disulfides.

.As the mixture travelling down in line 6 passes point 9, fresh copper treating solution is added thereto by way of I line I. The mixture thus formed continues 'on to'the pump I-, the while being further agitated and commin'gled, so that the fresh treating solution is intimately contacted with the recycled and new gasoline. -In the pump this action is still further brought about. Due to the size of'line 6 and of the inlet andoutlet of pump I, the material flows relatively slowly throughline -6 and through the pump I, which in"- sures a long and-intimate contact of the aqueous and oil phases with one another. I Due to the large inlet andoutlet ofpump I and to the construction and action of this pump, the. material is've'ry thoroughly and repeatedly mixed therein.

Asthe material leaves 'pump l' and enters line Ill, its pressure and velocity'are greatly increased, and it passes upwardly past point I6, where it divides, a portion-passing on into separating tank 2 wherein the treated oil separates by gravity from the spent treating solution. The proportion so entering tank 2 will depend on the setting of adjustable valve IA in line I3. I a I I A controlled and substantial portion'ofith'e mixture in line I0 is by-passed through line I3 controlled by valve I4 to be mixed with the sour gasoline entering through line 3.

Since line ID is at a higher pressure than line 3, the by-passing referred to is readily accomplished. As will be obvious, the amounts of entering sour gasoline, of fresh copper solution, and of mixture Icy-passed may be conveniently adjusted relatively to. one another by means of adjustable valves I4 and I8, so as togive the desired operation.

Preferably the vertical portion of line 6 is filled with suitable packing material I9 so as to increase the intimacy of contact between by-passedmixture and fresh gasoline, and, at its extreme lower portion, the intimacy of initial contact between the thus formed mixture and the fresh copper solution. For thi purpose Raschig rings or Berl saddles or any other type of packing material are suitable. The packing material may conveniently be held in place by a foraminous member (not shown) placed at point I! in line 6. Such packing material also helps to prevent layer separa tion in line 6. The amountof material by-passed through line 13 may vary within very wide limits, say from about 10% to about by volume'of the material in line III. Likewise the amounts of fresh sour gasoline introduced through line 3 and of fresh copper solution introduced through line 1 may vary widely relatively to one another, say from 10% of fresh gasoline and 90% of fresh copper solution up to 90% of fresh gasoline and 10% of fresh copper solution, these percentages being by volume.

By means of the present invention oils which are very difiicultly sweetened 'by the conventional method may be sweetened in a satisfactory and economical manner without employing expensive measures such as a number of mixing pumps in series or in parallel. By joy-passing a portion of the stream of partially sweetened hydrocarbon oil admixed with the copper treating solution to the sour oil charged to the system at a substantial distance above the intake of the pump and 'p'referably maintained a relatively long, slow moving body of material before entry into the pump, a longer contact time between the sour oil and the treating solution is obtained and a much greater reduction in the mercaptan concentration of the treated oil is effected than in the conventional process.

The present invention brings about a number of important resu-l'ts which aid the'sweetening operation, among which are the following. The dilution of the mercaptan content of the sour oil by admixture with a portion of the partially sweetened oil brings about a marked preliminary reduction in mercaptan content of the-fresh sour oil and provides lesswork for the fresh treating solution. The much greater contact time provided by the time of travel through the line 6 and by the time of travel through the endless circuit defined by pump line Ill, line 3, and line 6 in sures a much greater-effectiveness in reduction of mercaptan to disulfides thereby enabling copper sweetening to be performed upon types "of oils hitherto not feasible forc'op'per sweetening and to beperfor'med more effectively upon oils of the type heretofore sweetened by the liquid copper method. By the practice of myinventi'o'n a sour oil of relatively high mercaptan content or'co'ntaining meroa'ptans difiicult to convert to disulfides, or both, may be satisfactorily sweetened.

The other conventional steps in the process,

such as aeration of the treating solution, treat- The gasoline separating in tank 2 is very satisfactorily sweetened, although using the particular I used, wherever necessary, in constructing the apparatus shown in the drawing. It is also to be understood that instead of the centrifugal mixing pump l, equivalent contactors known to the art may be used, such as an injector, a submerged orifice, a mixing T, a, mixing tank with agitators therein, a conventional chemical contactor comprising a rotating shaft with blades and fixed baffles, if the contactor will of itself produce greater pressure at T It than exists at T I5, so that flow is maintained from T It to T- l 5. Otherwise, a pump is necessary to cause this flow from T It to T l5.

As will be obvious from the foregoing, the mixture which is by-passed through line l3 represents the unseparated material before opportunity for separation into aqueous and oil phases has occurred. Thus the recycled material is representafresh sour gasoline, it would be impossible to effect sweetening with operating conditions the same except with valve l4 closed entirely.

From the foregoing it will be seen present invention makes possible much wider application of the liquid copper sweetening method and presents a number of advantages over previously employed copper sweetening procedures.

It is to be understood that numerous changes and modifications may be made by those skilled in the art without departing from the spirit of my invention, which is to be taken as limited only by the terms of the appended claims.

I claim:

1. The process of sweetening a sour hydrocarbon oil which comprises introducing fresh oil to the top of a vertical elongated treating zone of relatively large cross-section, allowing the mate-, rial to pass relatively slowly downwardly through said zone, introducing fresh aqueous copper treattive, in composition, of the material passing up-,

wardly in line In and of the material passing into tank 2 for separation.

In some cases, especially where dealing with difiicultly sweetenable oil, atthe start of the oper-, ation before equilibrium has been established, the material passing'out into tank 2 may not pass the doctor test, but will be sour. However as soon as equilibrium has been established with the by-pass line l3 properly operating, the outflow into tank 2 will be sweet to the doctor test. If after the attainment of such satisfactory operating conditions for the particular oil being sweetened, valve 14 be closed so as to shut off by-pass line I3, the equilibrium of the system will within a short time be upset or disturbed and the outflowing gasoline will register sour to the doctor test. Actual operations have thus repeatedly and continuously demonstrated the value of the invention in enabling sweetening of certain oils which would be impossible to sweeten under identical conditions except with the by-pass discontinued.

Example ing solution adjacent the bottom of said zone into admixture with the material in said zone, rapidly and vigorously agitating the resulting mixture to obtain thorough and intimate contact of the components thereof, discharging the mixture towards a separating zone, withdrawing a portion of the discharged mixture, and introducing said with- Using the apparatus shown in the drawing, 120

barrels an hour of sour cracked gasoline are introduced into the system via line 3 and barrels an hour of copper sulfate-sodium chloride treating solution are simultaneously introduced via line 1, these proportions being predetermined by the adjustment of valve l1 and the pressures upon each of the gasoline and the treating solution. Valve I4 is adjusted so as to allow by-passing through line l3 of approximately barrels an hour of the mixture flowing up through line l0.

drawn portion into admixture with the incoming fresh oil adjacent the top of said treating zone, whereby said withdrawn portion and said incoming fresh oil intimately contact each other for a relatively long period of time during descent.

through said treating zone and prior to intermixture with said fresh treating solution.

2. Apparatus for use in sweetening sour hydrocarbon oils with an aqueous copper treating solution which comprises a vertical treating conduit of relatively large cross-section, packing material substantially filling said conduit for enhancing contact and preventing separation, a first conduit for introducing fresh sour oil adjacent the top of said vertical treating conduit, a second conduit for introducing fresh copper treating solution adjacent the bottom of said vertical treating conduit, a centrifugal mixing pump connected with the bottom of said vertical treating conduit beyond the second conduit, a further vertical conduit of relatively small cross-section connecting said pump with a separating zone, and a by-pass conduit connected between said last-named vertical conduit and the first conduit whereby a portion of the contacted and agitated mixture of the treating solution and oil is mixed with incoming sour oil.

ELMER H. BENDER.

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