US2048973A - Method for treating oil - Google Patents

Description

July 28, 1936.

A. J. SLAGTER ET AL I METHOD FOR TREATING OIL Filed Dec. 4, 1951 a /INVENTSEfi BYWATTOI JEY 7' Patented July 28, 1936 UNITED STATES PA' iE' -JT OFFICE METHOD FOR TREATING OIL Application December 4, 1931, Serial No. 578,964

2 Claims.

This invention relates to improvements in methods of and apparatus'for manufacturing petroleum products. The invention may be usefully applied not only in primary refining or processing operations, but also in the refining, reduction or processing of derivatives-or intermediates products emerging from the primary operations.

The method invention, in its broad aspects, may be practiced in .connection with a wide variety of oil heating or vaporizing devices or systems.

The invention may be employed for the production of superior grades of straight run and cracked gasoline and naphtha; to procure increased yield of :kerosene; to produce a more readily pressable wax distillate, more readily treatable .medium and heavy distillates, and superior grades of :gasoline by the refining of raw gasoline; to produce an effective solvent material from raw Jkerosene or other sources; for the -production of solvent materials and kerosenefrom gas oil or other sources; and for the production of lubricating stocks generally from lubricating-distillates or other sources. In general, an object of our invention has been :to improve the quality of petroleum products derived .trom known raw materials and :to increase the number and improve the equality of -petroleum products produc- .ible from crudes and/or intermediates.

In general the practice-of our method invention involves subjecting-crude petroleum or some derivative thereof to sufiicient heat in stages to produce selective vaporization under predetermined conditions of :pressure .or vacuum, separating the vapor from the liquid,-subjecting the entire :amount-of :the vapor separated under ,any

selected condition to a superheating treatment ultimate products or may-be returned'to various parts of the "processing apparatus for retreatment, this portion :of the method being iintended more particularly to produce a predetermined product by the retreatment of an intermediate (Cl. 196-"l3) product, for-example, in a continuous system and in a continuous .operation.

An exemplary form of apparatus for practicing the method invention and embodying the mechanical invention, is illustrated in the draw- ,5 ing accompanying the present specification, and in which,

Figure 1 is a general view in perspective; and Figure ,2, an .enlargeddetail in perspective illustrating schematically a typical arrangement of m discharge and connecting pipes or .conduitsassociated with the reaction and bubble towers.

Referring to the drawing, the apparatusshown in Figure 1 comprises .a plurality of stills I, ,2, and 3, or any other suitable-number thereof, 15 each, in the illustrated embodiment, being in. the form of a cylindrical tank .or shell, the under side of which provides in efiect the top wall of va furnace of any suitable-construction. Each furnace has vapor .superheating means, including, for ex- 20 ample, a plurality of pipes :9, communicating with headers lll theupper or inlet ends of whichopen into the interior of the respective stills above their respective levels of .unvaporized liquid to receive vapors generated therein and .convey the 5 :same ,to be superheated in said pipes ll.

' .The charge to :be ltreatedsuch for example, as crude petroleum, lubricating distillate or other intermediate .or appropriate petroleum compound, is ,-introduced into the illustrative system 3,0 by charging devices including a pump H .and a pipe l2, :of which a portion vforms a .coil 1,3 of I a heat exchanger including a tank 44, :to the interior of which is supplied .a v-hot ,product, such for example vas. residuum .from the. stills 2, 3, etc. 35 The ,charge is conducted through the pipe .12 1:0 coils l6 each vof which is enclosedin a tower 11 forming part of a combination vapor heat exchanger and reactionchamber in which said coils .are exposed to heated or superheated vapors orno other heated products or intermediates also-from said stills. From one or "more'of the coils 16in towers 'I'L'the charge is moved through pipe 18 and discharged by pipe -I-8'a into-still for example. An outlet pipe -=l 9 receives liquid flowing .45 out from the interior :of still I which outflow may be fed by means of :an iinterstage :pump 320 'into still 2.

I The inlet and outlet conduits or pipes aherein- 'abovedescribed connection with stills til and 2 5 and the pump 20 are duplicated if desired in connection with the remaining stills in the battery, it being noted, however, that the conduits for still 3 communicate with the interior of said still at a lower level than that at which the corresponding pipes or conduits communicate with their respective stills I and 2; and that, in relation to this arrangement of the inlet and outlet conduits, a liquid level gradient is provided ranging from a relatively high level in still I to a relatively low level of material treated in the still 3. A similar or other suitable gradient may be provided in .afurther succession of like stills.

With1the arrangement just described for introducing the charge into the stills, the oil to be treated reaches the first still at a relatively high temperature and is there subjected to the direct heat of the furnace. Under some conditions, the vaporization or other reaction may be accompanied by the introduction of steam or superheated steam or both into the still. .It may be introduced for some purposes into the upper portion of the still, namely the space above liquid level through a steam pipe 2|. It may also be introduced into the still preferably in the form of steam sprays liberated-within the body of the liquid and preferably in the vicinity of the bottomof the still by means of a pipe 22. Thus, in one case, namely where steam is introduced through pipe 2I, it reacts directly with the vaporized liquid; and in the other case, namely where it is introduced through pipe 22, the steam reacts with the material in liquid form.

In operation, the initial charge enters still I. A predetermined portion thereof or the more volatile components of the charge separate therefrom in said still in the form of'vapor and/or gas all of which is withdrawn downwardly through the openings in thetops of headers I0,

said vapors being then superheated in the pipes 9 and thence discharged through pipes 23 and into heat exchange and/or condensation apparatus hereinafter to be described. A predetermined level of liquid in still I is maintained by outflow of said liquid through discharge pipe I9, this operation being facilitated by the pump 20;

although, if desired and if conditions warrant, a similar control or movement may be effected by gravity or by causing or maintaining differential pressures in the different stills. Thus, by closing valves 24, 24, for example, the flow of liquid from outlet pipe I9 of still I to the inlet IBa' of still 2 by-passes pump 29 and is effected "through-pipe 25. However, by closingvalve 26 in pipe 25, and opening valves 24, '24, the discharge or outflow from still I will pass-through pump 20 and thence to still 2 or some other seflected still.

Control 'of the course of 28 in pipes I8a and I9 respectively and by valve fluid supplied to still I further effected by means of valves 21 and 29 interposed in a connection between said pipes I8a an'd l9. For example, to secure circulation of fluid inwardly through pipe I8a and outwardly -through pipe l9, valve 29 is closed-and valves 21 Land 28are opened. By closin'g valves 2!- and 28, and opening valve 29, the charge is by-passed ,asto anyselected still or stills, and maybe ad- 1 .ation taking place for example in a fractionating the. character'oriyield of the product desired.

throughzany predetermined'number of stills' and that the desired productshavebeenthereby re- Assuming that circulation has been established covered, the residuum is withdrawn from the last still of any selected series by means of a pipe 30, which discharges directly into the tank I4 so that some of the heat carried by said residuum is applied to the incoming charge of oil or other material as it circulates through the coil I3 previously referred to. The residuum is then discharged from tank I4 by means of a pipe 3| and thereby conducted to storage, or otherwise disposed of.

For convenient operation and effective control of the product, the connections between each still and its. corresponding heat exchange, or condensation or fractionation devices may be and preferably are the same as those of each other still; and the condensation devices are preferably interconnected in such a way that the discharge therefrom may be removed as a completed product and/or may be reintroduced into the treating operation at any desired portion thereof. Thus, each of the vapor outlet pipes 23 discharges into a bottom portion of a tower I'I,

' the interior of which is cooled in part by means of the coil I6 carrying the relatively cool charging liquid and in part by back trap condensate as hereinafter described. The condensation product in said tower I1 is withdrawn through a pipe 32 which is controlled by a-valve 33, shown more clearly in Figure 2, said pipe 32 having a portion in the form of a gooseneck or trap 34 "from which the product may 'be discharged through an outlet pipe 35 by opening a valve 36; or, by closing valve 36, the product may be returned to still I through pipe 31 controlled by valve 38.- Another pipe 39 which connects with pipe 31 includes a valve 40. -When valve 40 is open, the outflow through pipe 39 together with that through pipe 31 discharges into the still I.

- Thus, valves 46 and4'I control the input to pump 45 from pipes M and 42 respectively, and valves 48 and 49 control the output from pump 45 into the pipes 4| and 42. A valve 50 in pipe 4| may 'be opened to permit flow of condensate past' the pump 45 if desired and a valve 5| performs a sim- 'ilar function in respect to the flow of liquid throughpipe 42 pastjpump 45.

The connections and control valves just de- "scribed may be repeated inrespect to each still and its vapor heat exchanger if desired, to the end that the'back trap return from any exchanger may be withdrawn and/or reintroduced into any still 3 stillsin addition to the original charge or any portion thereof."

An additional cooling effect isattained in the tower I! by supplying thereto the back trap rei turn condensate or av portion thereof from a fu1 ther or more remote cooling or condensing opercolmnnor bubble tower 52. The product of any such column may be withdrawn directly as a completed product through a pipe. 53 communicating with an outlet pipe 54 at the bottom of column 52; or the whole or apart of saidproduct may be re-' turned to a selected still either directly through a pipe or indirectly through a branch pipe 56 to the tower I! and thence to a still, said pipes being provided with suitable valves for permitting the alternative modes of operation above stated. For example, the pipe 56 has a valve 58 which, when closed, prevents the circulation of fractionating column back trap return in the branch which includes the pipe 56. A valve 59 in pipe 55 may be utilized to control the flow of fractionating column back trap return to the still. For example, when valve 59 is closed and valve 58 is open, the condensate in pipe 55 operates as a vapor cooling medium in the tower I1 and is discharged therefrom through pipe 32.

Fixed gases and uncondensed vapors pass from the tower I? through a pipe 60 into a lower portion of the bubble tower or fractionating column 52. Any suitable reflux may be pumped or otherwise introduced into said column through the pipe 61. The uncondensed vapors and/or fixed gases in the fractionating column 52 are delivered through a pipe 62 to suitable condensers or receivers or both, not shown.

In some cases, it may be desirable to provide means whereby the bubble tower or fracticnating column may be by-passed or used for its ordinary intended purpose at will. In such case, the inlet pipe 69 and the outlet pipe 62 are connected by a pipe 63 containing a valve 64. A valve 65 is interposed between the pipe 60 and the fractionating column 52, and a valve 65 between the fractionating column and the outlet pipe 62. Thus, when valves 65 and 66 are closed and valve 64 is open, the vapor product discharged from the vapor heat exchanger passes out directly through Simultaneously and continuously with vaporizing, the entire vaporized portions of the charging stock are independently withdrawn and superheated and then treated in the reaction and/or fractionation towers connected with the several stills; and the condensates in these towers are selectively disposed of to suit a wide range of conditions. It will be apparent that, depending upon the conditions of temperature, pressure, vacuum and/or steam employed, the apparatus operates interchangeably and, if desired, simultaneously both as a straight distillation apparatus and/ or as a cracking apparatus.

Where we utilize a system employing a battery of eight stills, for example, operating at temperatures and pressures which produce cracking, at least 70% by weight of the treated liquid is reduced to vapor form, the remainder issuing from the last still as a heavy fuel residuum. This vaporization takes place by stages in the several stills, the entire amount of vapors produced in each still being separated from the liquid and conducted through a superheating zone to undergo such superheating treatment as conditions require.

The range of utility of our improved apparatus will be better understood by reference to a disclosure of typical operating conditions and the products recovered in connection therewith.

Primary distillation of pamfiinic crude In employing our system, comprising a battery of eight stills and corresponding reaction and bubble towers, for example, as a distillation apparatus more particularly for handling a crude having a parafiine base, typical operating conditions are indicated by reference to the following outlet pipe 82. tabulation:

Temp. bottom Vapor of combination Temp. top Temp. T t Still Still temp temp.1eavreaction chamof combinabottom of g t g Pressure in still No. ing supcrber heat extion tower bubble g u g #lgaugc sq. in.

heater (23) changarntower (l7) tower (52) ower Ap rozimalel 1 450 650 550 500 460 300 Atz r io. y 2 500 700 600 550 510 365 Atmo. 3 550 725 625 575 535 425 Atmo. 4 600 (steam) 750 635 585 545 450 Atrno. 5 650 (steam) 800 650 600 560 475 Atmo. 6 700 (steam) 850 700 650 .610 500 Atom. 7 750 (steam) 900 750 700 660 525 Atmo. 8 800 (steam) 950 800 750 710 550 Atmo.

As previously suggested, the back trap return from the fractionating column 52 may be utilized in a manner similar to that of the back trap re turn from the reaction heat exchanger towers l1 and by a similar arrangement of pipe connections and valve controls. Furthermore, the same type of interstage pumping devices and valve control apparatus may also be utilized in connection with the fractionating columns 52 as has been described in connection with the towers l7.

The apparatus above described provides an oil processing system in the operation of which a suitable charging stock is passed in a continuous stream through a sequence of any desired number of vaporizing stills. Where desired, the vaporizing temperature in each still may be 'diiferent from that 'of each other still; and likewise, the vapor superheating temperatures-may vary according to any desired or-predeterinined plain.

It will be noted in the foregoing tabulation that the introduction of steam is indicated in stills numbers 4 to 8 inclusive. Under the specified conditions of operation, steam is introduced in liberal quantities more particularly in those stills from which wax distillates and lubricating stock residiuum respectively are to be recovered. Naturally, these products appear toward the end of the sequence of the "stills, being derived from vapors of heavier consistency than other vaporizable products of the operation, such as light gasoline, heavy gasoline, naphtha, kerosene and gas oil. Where a liberal amount of steam is indicated, we have in mind about 200 pounds per barrel of charge.

In another use of 'our improved "apparatus, we contemplate the employment of 'a'vacuum mo're pa r ticularlyih various of the end stills of Typical operating conditions are vaporized out of the liquid .charge at alower temperature than would otherwise be required,

v 'liemp'bbottgm T t 'r apor 0 com ma 1011 ernp. op amp. Still Still tem temp. leavreaction chamofcombmabottom of Pressure in still No. mg superber heat extion tower bubble towel. (52) #/gauge sq. in.

heater (23) changer tower tower (52) Approximately 1 450 650 550 500 460 300 Atmo. 2 500 700 600 550 510 365 Atmo. 3 550 725 625 575 535 400 Atmo. 4 600 (steam) 750 625 575 540 420 Atmo. 5 (vac) 625 (steam) 765 625 575 540 440 28 inches Hg.

vacuum.

6 (vac) 650 (steam) 775 650 600 560 460 Do. 7 (vac) 675 (steam) 785 675 625 585 480 Do. 8 (vac) 700 (steam) 800 700 650 610 500 Do.

With the foregoing temperatures, pressures and other factors, the yields include gasoline, naphtha, kerosene, gas oil, wax distillate, one or more intermediates in the form of lubricating distillates derived from an overhead condensed vapor in each instance. The residuum is a tarry mass containing no lubricating material. In connection with the operation of still No. 5 under a vacuum which takes place preferably after part of the gas oil has been taken off, the vacuum is rendered effective by application to the condensing system of the still or stills, and may be produced by any suitable or well known means such as jet pumps, vacuum exhausters or the like, not specifically shown. The steam is utilized as in the operations represented in the previous tabulation.

Primary distillation of naphthenic crudes oil yield is reduced. In this operation, the amount.

of steam used may be reduced to around 25 pounds per barrel of charge treated and the vacthereby producing less risk of cracking, which is detrimental to the viscosity of the product.

Rerunnirig lubricating distillates before chemical treatment -mary distillation of whatsoever character and before any chemical treatment. For this purpose, we utilize the range of temperatures indicated in the foregoing tabulations and employ liberal amounts of steam in the stills with vacuum in the latter stages. By this operation we effect distillation of the charge without cracking beyond the degree permitted for producing a proper lubricating oil, and efiect a change in the character of the impurities in the charge, which permits them to be removed more readily and at less expense by subsequent treatment. While the exact nature of these changes is not fully understood, it is our view that the wax and petrolatum contents are made more crystalline by superheating in the vapor stage and the mercaptan and other heavier impurities are so affected by the superheating that their removal requires less acid and a shorter time of treatment.

Cracking gas oil to secure maximum gasoline yield By varying the operation conditions indicated in the foregoing tabulations relating to distillation procedure, our improved apparatus operates as a cracking apparatus. As an example, for cracking gas oil to obtain a maximum yield of gasoline, we provide conditions of temperatures, pressure, etc., somewhat as indicated in the following tabulation:

Temp. at bot- T t Vapor tom of combi- 9p Temp.bot-

oi combr- Temp. top Pressure in still Still No. Still temp. ggg g fig gffigg nation regg qg of bubble lbs/sq. in. above superheatexchanger gggg gfi tower (52) tower (52) er (23) tower (17) 1 650 F 850' 650 575 500 350 1701b Ol' 70. 2 675 875 675 585 510 360 160 01 3 700 900 700 595 520 370 150 or 50. 4 725 925 725 605 530 380 140 01 40. 5 750 950 750 615 540 390 130 0! 30. 6 775 975 775 625 550 400 120 O1 20. 7 800 1, 000 800 635 560 410 110 O1. 10. 8 825 V 1, 025 825 645 570 420 100 01 Z8l0.

uum is carried at 28 to 29 inches of mercury. In general, our purpose in using steam and/or vacuum in connection with distillation is to lower the vapor pressure of the desired cut so that it will be The pressure drop between stills in pounds to the square inch or in pounds above atmospheric Instead of using a liberal supply of steam as in distillation,

set forth above ismerely illustrative.

we use a limited supply, for example, about 25 pounds to the barrel of charge treated, the restricted amounts of steam being utilized both in the liquid and above-thesurface thereof.

In orderto produce a larger proportion of cracked kerosene from the gas oilandasmaller proportion of gasoline, the operating conditions above'tabulated are adjusted to change the character of the product more particularly as derived from stills 6 and 7. The changes are indicated in the following tabulation, the temperatures, pressures, etc., therein being substituted in respect to corresponding stills for the temperatures and pressures set forth in the next oline, upon being treated chemicallyor other- :wise. purified, is rated as finished gasoline.

When our apparatus or some portion thereof is operated for the purpose of treating a charge .destined to yield wax distillate, such charge is redistilled in one or more stills in which a higher temperature is employed than that utilized. in the still .from which the .charge, usually in the .formof a heavy wax distillate, wasoriginally produced' The vapor products of this reheat ing operation are superheated, thereby changing the character of the wax content so that when pressed it will be of a crystalline characteristic rather than amorphous. This operation may preceding tabulation: take place as a part of the continuous distilla- Vapor Temp. at bot- T t temp. tom of combig gh g Temp. bot- T emp. top Pressure in still Still No. Still temp. 5323 5 gg g figg nation a ga of bubble lbs/sq. in. above et t gsr g fg $35.18;) tower (52) tower (52) atmo.

6 760 800 760 600 540 390 100 or 20. 7 770 810 770 605 545 400 90 or 10. 8 780 820 780 610 550 410 80 or atmo.

In the operation of our apparatus as a cracking system with a gas oil or reduced crude charge and employing eight stills with corresponding towers, cracked kerosene is taken as an overhead vapor from the top of No. 4 bubble tower or fractionation unit operatively connected with still No. 4. At this particular stage of our method, we are able to recover a cracked kerosene having characteristics which permit it to qualify as commercial kerosene insofar as its carbon content compares With the carbon content of straight run kerosene produced by distillation from crude. In this respect our multiple still apparatus produces results superior to those at tained by known types of single still apparatus employing cracking temperatures and pressures, but without our multiplicity of stills combined with reaction and heat exchange towers and fractionation bubble towers with vaporization,

Where it is desired to operate our system as a combined distilling and cracking apparatus, crude petroleum, for example, is charged into still No. 1, under the conditions of operation previously tabulated in connection with distillation runs. This produces straight run gasoline from the tops of towers No. 1 and No. 2 and straight run kerosene from the top of tower No. 3. By increasing the temperature gradient in the remaining stills and suitably adjusting the steam and pressure conditions therein, we produce cracked gasoline from the tops of towers Nos. 4, 5, and 6, cracked kerosene from the top of No. 7 and a light furnace oil from the top of No. 8.

Processing unfinished cracked gasoline Some conditions of cracking, produce gasoline of too high a sulphur impurity content to permit sufficient purification by the usual purifying treatments. We are able to employ our processing apparatus as a treating system for rerunning any kind of an unfinished cracked gas oline from whatsoever source. In so doing We vaporize a portion of the liquid charge in a stream and superheat the vapors in stages sufficiently to change the character of the gum and sulphur impurities, so that thereaiter, the gas tion from wax bearing crude under conditions previously noted or it may take place in all or any part of the stills.of a battery operating for that purpose.

From the foregoing, it is clear that the advantages in operation associated with use of the apparatus hereinabove described, include its adaptability to the production of a wide range of ultimate products, either singly or simultaneously from a great variety of raw materials ranging from crudes of diiferent characteristics down through various grades of intermediates. This wide adaptability of the described apparatus, or apparatus equivalent thereto, is supplemented by the economies capable of being elfected in connection with its operation, as the conservation of heat, continuous use and simplified and flexible control.

In the employment, by this invention, of a plurality of still units assembled in a battery, with interconnecting and controlling devices, the pressure may be varied as to different stills in a progressively increasing or decreasing gradient; or it may be varied in any other way required to secure any particular product or to effectively treat any given character of raw material; It will be apparent that our improved method and apparatus also present a wide range of flexibility in the control of all critical operating factors not only in the stills but also in the condensation and cooling devices associated therewith. The importance-of this will be recognized in its relation to the making of products which can only be secured in a pure or relatively pure state by condensation from the vapor phase under particular conditions of temperature and pressure.

We claim as our invention:

1. The process of distilling hydrocarbon oil to produce several fractions including lubricating oils as overhead distillates which includes passing said oil into and through a plurality of enlarged zones arranged in series, heating the oil in the first zone of the series to about 450 F., obtaining vapors and unvaporized oil in each of said zones and passing the latter successively from zone to zone and heating said unvaporized oil to successively higher temperatures, the temperature of the oil in the last zone beln about 790 1",, operating at the beginmn under proximately atmospheric pressure, distilling the liquid with steam toward the last stages of the distillation, finally discharging unvaporized liquid from the last zone, separately superheating'vapors produced in each enlarged zone to successively higher temperatures, the vapors produced in the first enlarged zone being superheated to about 650 F. and the vapors produced in the final zone being superheated to about 800 F., separately fractionating the streams of superheated vapors and condensing overhead fractions as products of the process.

2. The process of claim lincluding the step of operation undervacuum toward the last stage of 5 the distillation.

ARTHUR J. SLAGTER. CHARLES W. MACKAY.

Images