US2246592A - Conversion of hydrocarbon oils - Google Patents

Description

June 24, 1941. 1.. c. HUFF CONVERSION OF HYDROOARBON GEES Original Filed July 5, 1935.

muZmUum INVENTOR LYMAN c. HUFF TORNEY Patented June 24, 1941 CONVERSION OFHYDROCARBON OILS BymamGUHuff', Ghicago, Ill., assignor to Universal QihProduots- Company; Ghicagm Ill., acorporationcofwn'elaware- ApplicationJuly 5; 1935; Serial No. 29;? 9'5 Renewed April -18; 1939- The present invention refers to an improved process forthe pyrol'ytic conversion of relatively heavy-- petroleum-oils; such as topped crudes and the 1 like; at elevated temperature and superat m'ospheric pressure for the produ'ctionmr high yields of"good" quality"motor fiiel and eithei mai to thekexc'essive frmation an in the heating coil.

spect' to: suspended carbonaceous material and:- the presence of excessivea-mounts -of carbona'ceous material in the cracked residue the" present process becomes particularly adaptableto the treatment of topped crudes or residual oils of ian iasphaltichatu-re for the production of can goodiqua'lity motor fuel -a'nd good quality asphalt although the invention-ismot limited to thetreatment' of: asplialtici charging toek's nor to the pro c'luct'ion of asphaltl' aathefihal residual"productof the-process;

In one embodiment? the" invention comprises subjectingresidual' petroleum-fractions of an as phalticr nature to conversion conditions of cracking: temperature andsubstantial supera-tmospheric" pressure in eommingled state with lowboiling 'normally gaseous hydrocarbons absorbed by contactingthe charging stock} 1 withtheprocess gases," introducing theresulting heated and partially converted materials into" an enlarged reaction chamberalso i maintaihed at superatmos ph'eric pressure-' wherein the desired conversion reaction are completed} withdrawing both Va porous" and liquid conversion" products" from the reaction chamber-and introducingthe saine into a reduced pressure vaporizing chamber" wherein separation of vapomus and residiial liquid conversionproduc'ts' is accomplished, withdrawingthewlatter from the" vaporizing chamberand subl jecting the sanieto furtherwdiis'ti'llation at sub atmospheric pressure for theproduction of asphalt, separately withdrawingvaporous conversion pro ducts 'from the vaporiairigphamber; subjecting the same to fractionation for the forma tion of'reflux"condensatecomprisingtheirinsufficiently" converted components and' the recovery of" fractionated vapors-within of motor fuel, which latter-alected; returningtl'ie' refiux condensate to" time pendently controlled conversion conditions" of higher cracking temperature and superat'mos pheric pressure in a-separate heating coil; introclucing the heated products from said separate heating coil into thevaporizin'g chamber, subjecting said motor fuel productresultingfrom condensation of the fractionated vapors-to stabilization for the removaltherefrom ofundesirablelow-boiling components; whereby to control its vapor pressure, and contacting the uncondensed gaseous products of the process-with said-chargingstock prior to its introduction into=the first mentioned heating coil.

While the elements of plants for accomplishing the above objects may-vary somewhat in their absolute and relative proportions depending-upon the character of oil to be-processed and thedesiredresults, the essential features ofoperation comprised in'the scope ofthe present invention are generallysimilar in all' plant's and the attached drawinghasheeh providedtb assist in describing a characteristicoperation: The-drawing shows-diagrammatically, by'the use ofconventional figures in side elevation, anarra-ngement of interconnected elements in which the steps of the processmaybe conducted. Aswill be'shown by a later example; the particularsystem illustrated isparticularly applicable to 'resi'duaI stocks of 1 high specific gravity;

Referring to the drawing; charging oil is introduced to the plant from any su'itab le" source of supply, not shown; through a" line I containing control valve 2 and isfed byfpurnp 3 through line t and valve 5 into a point near thEGOpOf an absorption column 6, from whichthe unabsorbed fiked gases are discharged throughline 'lcontaining control valve 8; Theabsorber may be of any conventional typecontaininga series of superirnposed bubble trays or other suitable contacting means to insure substantially complete absorption from the gases-supplied thereto ofall hydrocarbons of 4 carbon atoms (the butanes and butylenes) and a portion ofthe propane, while leaving unabsorbed such gases as hydrogen, methane; ethane, ethylene, etc; The' gas mixturesare admitted to the absorherfromv line 62 as willbe described at a later point The absorption of oilvapors'at thispoint having the generalcharacteristicsof'the low-boiling fractions of gasoline has a two-fold advantage in that this material isrecovered to augment the yield of the final light distillate product of the process and that the presence of appreciable quantities of'such fractions in'the heavychargiing oil has a tendencytolessen coked'eposit'ion in the primary heating coil, probably due to combination of the low-boiling materials with the heavy, coke-forming conversion products. The conditions employed for cracking the raw oil are hardly severe enough to effect substantial conversion of the light fractions, which, however, by virtue of their partial pressure in the heating tubes, serve to make possible the use of relatively higher temperatures and lower time factors in this zone.

Raw oil containing absorbed light hydrocarbons passes from the bottom of absorber 6 through line 9 and valve Ill to pump H from which it is fed through line [2 and valves l3 and I3 to a heating coil comprising tube banks l4 and [4' within furnace setting 20. Controlled quantities of the charging stock may be passed through a heat exchanger 29 by way of inlet line 21' and valve 28' and outlet line 29' containing valve 30, with valve l 3 totally or partially closed. This diversion of flow serves to efiect partial preheating of the enriched charging oil from absorber 6 and lower the temperature of the vapors from chamber 25, with which it passes in indirect heat exchange. Obviously, the amount of condensation caused by the cooling effect of the raw oil will to some extent control the quality and end-boiling point of the intermediate fractions recovered as reflux condensate in fractionator 34.

The element for heating and instigating cracking reactions in the charging stock consists, in the case illustrated, of two interconnected banks of horizontal tubes l4 and M, respectively, which receive principally radiant heat from combustion gases generated by the combustion of fuel supplied to combustion and heating zone A of the furnace by means of suitable burners indicated at is. The combustion gases from heating zone A pass downwardly over a separate bank of tubes I5, within the centrally located fluid heating zone C of the furnace, along with the gases from the other combustion and heating zone B, to be presently described.

Temperature and pressure conditions employed in the charging stock heating coil may be varied considerably depending on the quality of the charge but are generally within the limits of 850 to 950 F. and 100 and 500 lbs. per square inch.

Heated products are discharged from the charging stock heating coil through line 2| containing control valve 22 and pass into a reaction chamber 23, wherein substantial completion of the desired conversion reactions occurs and wherein a substantially superatmospheric pressure is maintained which may be substantially the same or somewhat lower than that in the last tubes of the heating element.

In the case here illustrated both vaporous and liquid products are discharged from the bottom of chamber 23 through line 24 containing pressure control valve 25 and enter a vaporizing chamber 26 maintained at substantially reduced pressure of the order of 100 lbs. per square inch to substantially atmospheric pressure, with a reduction in temperature in this zone due to the pressure reduction. In the vaporizing chamber separation of vaporous and liquid conversion products is accomplished, the former comprising substantially all of the gasoline boiling range fractions and other constituents having characteristics rendering them suitable for further conversion within the same system. The residual liquid, which is preferably of a fuel oil character at this point, is withdrawn through line 93 and a portion or all of it may, when desired, be cooled and stored for subsequent use after withdrawal through line containing control valve 96. When it is desired to further reduce this residuum to produce a good grade of marketable asphalt it is further subjected to vacuum distillation, which will be described after the completion of the description of the cracking process.

The vaporous products from chamber 26 follow vapor line 21 containing control valve 28 and pass through heat exchanger 29 in general counter-flow to regulated portions of the charging oil composite, as previously described. Line 30 containing control valve 3! indicates a drain line which may be employed for removing heavy material condensed in the heat exchanger. Due to the cooling of the vapors in heat exchanger 29 this zone serves to separate therefrom heavy carbonizable liquids which might cause tube troubles if returned to further conversion with the reflux condensate.

The major portion of the vapors supplied to heat exchanger 29, which remain uncondensed therein, pass from the heat exchanger through line 32 and valve 33 to fractionator 34 of the conventional bubble tray variety or any other suitable form. This fractionator serves to separate the vapors of motor fuel boiling range and fixed gases as an overhead fraction from the higher boiling components of the vapors which are condensed as reflux condensate. Reflux condensate is withdrawn from the bottom of the tower through a line 75 and valve 16 and pumped by pump Tl through line 13, valve 79, line 89 and valve 99 to an independently heated tubular cracking element comprising tube banks l5, l6 and H.

In the case here illustrated the heating coil to which the reflux condensate is supplied is also located within furnace 2i] and the combustion gases from both combustion and heating zones A and B pass over the tubes of bank l5 imparting fluid heat thereto. The roof and floor tubes l6 and I! are supplied with radiant heat from the materials undergoing combustion in heating zone B; fuel being supplied to this zone from a series of burners indicated at [9. The temperature and pressure conditions employed in the reflux heating coil are preferably somewhat more severe than those employed for the charging stock and may be of the order of from 900 to 1050 F. and 200 to 800 pounds, or more, per square inch. In the present operation the heated products from the reflux heating coil are directed to the vaporizing chamber 26 by way of line 9| containing control valve $2., which may join with line 24 previously mentioned.

The fractionated vapors and gases from fractionator 34 pass through line 35 and valve 36 to condenser 31, from which the resulting distillate and uncondensed gases flow through line 38 and control valve 39 to collection and separation in receiver 40. In order to effect stabilization of the distillate it is passed from receiver 46 through line ll and valve 42 to a pump 4-3 from which it is directed through heat exchanger 4, line 45 and valve 46, recovering heat in the heat exchanger for effecting partial vaporization of the distillate before it passes into stabilizing column 41.

Column 41 is commonly operated at a pressure of from '75 to 150 pounds, or thereabouts, per square inch, a top temperature of to F. and a bottom temperature of 250 to 325 F. The function of the stabilizing column Al! is to aeae sea remove all of the. normally gaseousconstituents; including hydrogen; methane; ethane; ethylene,-: propane and propyleneandaacertairrportiomof! the butanes and butylenes; fromlthel distillatei supplied: to this? zone sou thatfi the. vapor "pressure" of: the: resulting: finishedi gasoline-21s: oftitheleorderr on from 8: to i 12-. pounds: per: square: inch: bpthe; Reid-1 test;

When the temperature or the :entering; mates rials afterspassing throughlheat exchanger Maris notl'higlr enough to: maintainilthe:requireditenra perature: differentialirr the; stabilizingtcoiummair auxiliary heating arrangement. on any? suitable? formzrmay be: employed :f or" reboilings'the r distillate? from the bottom of. column I 41:; Inztheacaser herel illustratedxheat; for reboil'ing 1' is: obtaineda by "the:- diversion of a; portion of" the: reflux: condensate. fromxfractionator" 34; which; QETSSFthITQIIghs linerflm and valve: BII to a closed; coil in: reboi'lenr ;:andi' thence backtofractionator: 34's eithers directlythrough; line 82, valve: 83 and: linerI:I'4 orrbwwayr otcline 84, valve 845; cooler: 86; lineia'lr valtsejfli an'dHineLIM'. Theiunction'aof coolerillfi'isrtmco trol; th temperature of x the-s. oil returned: as: res fluxingl liquid: to. fractionator 34r and; thus: assist: in controlling l the 1 GhQJaCtEIClOfi the: fractionation. in this zone. Reboiling: ofr the matenia-lstinzlthe bottom1 of thel stabilizing column; is: effected. by; withdrawing thenon-vaporous distillate; from column 4a'I through: line: 66 andzvalvefl toereboilen 'Illmfromwhich evolved vapors are returned; torthexcolumncthrough line 68: andya-lve v69"; Stabilized? liquidi representing thestabilizedlmotors-fi1elprod:= not of the process is withdrawn fromlreboilerfilm at a: point remote: from inlet linerfifir through lin band valve IZ-and passes through heatilex't changer 44, the function or:whichmasrbeenl-pre viously described, after which-:itimay passto. fur therrcooling and storage onto; any desiredzlfuntheri treatment by way of line 13 containing control: valve-14L The overhead products-fromrstabilizing:vcolumni 41: pass" through I line 48? containing controlvalve? 49: and: through a condenser: 50:; which; may; 013,- I erate I at i subatmosphericwtemperature if desired; and: the resulting condensategyalong; withtfixedi gases, passes through line 51- containing control valve" 52 to separation in an? accumulation: The": liquid; condensate collected? atntliis-lpointlwillicom prises principally four-carhon atom"-hydrocarhons; with traces of I propane and some: pertanes; landwif desired a: portion thereof mayrbewithdnawn to r separate storage a through; line 55 and valve: "55'; The amount necessary for refluxlng'r at: the? top; of Y the I stabilizing column is ewithdrawnvthrouglr line: 5'!" and valve: 58- andTecirculatedibywpump. '59 through "line 60 and valveHI to'columnzk-I: Fixed-l gasescfrom receiver 40 may -passntor absorber: 6w by way of line: I54 and valve and: similarlwgases-i from receiver 54 may I be supplied? to thezsabsorber" through line 02'andvalve 6'3. I

In order to make asphalt froml-thenonsvaporous residual liquidxfromlchamberwzfirpump 91:- supplies all or any desired. portion: thereof" through line 08 and valve 99; to a a-vacuum-Ievapoe rator I00. Using a subatmospheric pressure at this point of the order of from 3 to 5 inches or more of mercury absolute pressure enables the efficient and rapid production of marketable asphalts in this zone. The asphalt may be withdrawn to storage through line IN and a valve I02. Vapors from the vacuum evaporator pass through line IOI and valve I02 to condenser I03 and thence the resulting condensate and gas passes through line I04 and valve I05 to a receiver I00, Thearequisitevacuum is maintainedLimcolumn I00, in the case here illustrated; by withdrawing ,thefixed lgaseslfroml receiver Il06lthrough line I01 containing control valve I08 toa barometric condenser [09, which maybe or any'con ventional' for-mand therefore neednot be described imd'etail The overhead distillate products from the asphalt evaporation pass through line- H0 and valve II I to a pump II2, which" discharges through line" H4. This product will" ordinarily comprise an oill isuitable for example as light domestic or industrial fuel andaregulated portion or all-ofithis material may be discharged through branch line H2 and valve 3' to storage orelse whereas desired and regulated quantities thereof may be used as a refluxing: medium in column I00 to control.thedistillation inthe vacuum evaporator by passingthe' same through valve I15 in line m: and thence through line In containing controLvalve H8. into the upper portion of the evaporator. On the other hand all or any desired portion of the condensate collected in receiver l'lli may be returned for further conver sibn to--the-1ight-oil heatingcoil of the system.

It may-be supplied direct to-this zone; by' well known means-not illustrated, or mayfirst be utilized'. asa cooling and refluxing mediumtin fractionator 34 by supplying: the same thereto through valve H6 in line II4.

ihg the iollowingproperties-t" ANALYSIS oF'ToPPED CRUDE Gravity; A. P? I 1116 Specific gravity" l l 019888 Flash ((Jlevel'and open cup) F; 225* Fire (Clevelandopencup), F 270 Flash (Pensly Martens), Fl .Q. 205 Viscosity; fiirol-(il 122 F., sec 1'74 Sulfur-pen cent 4215 I. Coldltest, F 13 BnS:-.&iW.-eper cent--- l 0.3

100*66. distillation I; 13, 12.19 F .-4- l ;..l l l l l 44.1.) 5 5 05 30. 646 4.0;- -7. 676- 610 693 eof; r 705" 716 8U.- a l.. 723

Per centzover; 37.5=

" Per-centcokebywt. 12.4 Pen cent"@ *572F 1515' The topped crude which represented 78.3% of the original crude oil was cracked in a plant corresponding in essential details with the one shown in the drawing to produce a maximum yield of 375 F. end-point gasoline while proc esslng the residuum from the flash chamber to produce asphalt of from to penetration. In the following table are summarized the overall results of a run which extended over aperiod of several days.

SUMMARY or CRACKING CONDITIONS Temperature at outlet from charging stock heater F' 920 Pressure at outlet from charging stock heater lbs. per sq. in 225 Temperature at outlet from reflux heater F 950 Pressure at outlet from reflux heater lbs. per sq. in 350 Average temperature in reactionchamber F 870 Pressure in reaction chamber lbs. per sq. in 225 Pressure in vaporizing chamber lbs. per sq. in 50 Absolute pressure in asphalt reducing still lbs. per sq. in 1.5

YIELDS, PER CENT BY WEIGHT or CHARGING STOCK Per cent Motor fuel of approx. 375 F. end-boiling point 5O Asphalt (80 penetration) 42 Fixed gases 8 PROPERTIES or LIGHT DISTILLATE PRODUCT (UNTREATED GASOLINE) Specific gravity 0.748

Ductility cm 100 Solubility in carbon bisulfide per cent 1 99.3 Solubility in carbon tetrachloride do 99.0 Solubility in 86 A. P. I. parafiin naphtha per oent 75 The practical features of the process will be evident to those conversant with oil refinery operations from the preceding data on conditions of operation, yields, and the qualities of the principal products. However, neither the descriptive material nor the numerical data are to be construed as imposing undue limitations upon the generally broad scope of the invention.

I claim as my invention:

1. In a process for the conversion of hydrocarbon oils wherein intermediate liquid conversion products of the process are subjected to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil and then introduced into a reduced pressure vaporizing chamber wherein vaporous and residual liquid conversion products are separated, the vaporous conversion products subjected to fractionation for the formation of reflux condensate comprising said intermediate liquid conversion products which are supplied to the heating coil for said conversion, fractionated vapors of the desired end-boiling point subjected to condensation, the resulting distillate and uncondensed gases collected and separated and the distillate subjected to stabilization whereby to liberate therefrom dissolved gases and undesirable low-boiling components for the purpose of reducing its vapor pressure, the improvement which comprises subjecting said uncondensed gases together with the gaseous products liberated from the distillate by said stabilization to absorption by contact with charging stock for the process comprising an oil of higher boiling characteristics than said reflux condensate, subjecting charging stock from the absorption stage, containing absorbed high-boiling components of the gases, to independently controlled conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber maintained under higher pressure than the vaporizing chamber, introducing the resulting conversion products from the reaction chamber into said reduced pressure vaporizing chamber, withdrawing residual liquid from said vaporizing chamber, subjecting the same to further distillation at subatmospheric pressure for the formation of asphaltic residue, recovering the latter, subjecting the vapors evolved by said further distillation of the residual liquid to condensation and returning resulting condensate to the fractionating stage of the cracking system.

'2. A conversion process which comprises subjecting a residual petroleum oil to cracking conditions in a cracking zone, simultaneously cracking a recycle stock, formed as hereinafter set forth, at higher temperatures than said residual oil in a second cracking zone, discharging the cracked products from both said zones into a reduced pressure vaporizer and therein separating the same into vapors and a liquid residue, fractionating the vapors to condense heavier fractions thereof, removing liquid residue from said vaporizer and reducing the same to an asphaltic material by further distillation thereof under subatmospheric pressure, introducing condensate resulting from said further distillation into contact with said vapors undergoing fractionation as a refluxing medium for the vapors, thereby combining said condensate with reflux condensate separated from the vapors by the fractionation, supplying the resultant condensate mixture to the second cracking zone as said recycle stock, finally condensing the fractionated vapors and separating the resultant distillate from normally incondensible gases produced in the process, scrubbing such separated gases with said residual petroleum oil prior to the introduction of the latter to the first-mentioned cracking zone, whereby to absorb heavier components of the gases in the residual oil, and supplying the absorbed gaseous components to the first-mentioned cracking zone together with said residual oil.

LYMAN C. HUFF.

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