US2009367A - Art of converting high boiling hydrocarbon oils into lower boiling hydrocarbon oils - Google Patents

Description

JuIy 23, 1935. R. E. WILSON 2,9,367

ART OF CONVERTING HIGH BOILING HYDROCARBON OILS INTO LOWER BOILING HYDROCARBON OILS Filed June 1, 1931 Patented July 23, 1935 UNITED STATES PATENT OFFICE.

I i 2,009,367 r Y ART OF CONVERTING-HIGH BOILING HY- DROCARBON OILS nvro LOWER BOILING HYDROCARBON OILS Robert E. Wilson, Chicago, Ill.,' assignor to Standard Oil Company, Whiting,'Ind., a corporation of Indiana Application June 1, 1931,"Seria1 No. 541,516

5 Claims (01. 19666) The present invention relates to the conversion of relatively high boiling hydrocarbon oils into relatively low-boiling hydrocarbon oils, for example oils suitableas fuel for internal combustion engines. The present invention is particu larly directed to improvements in such conversion operation conducted under superatmospheric pressure conditions.

In certain of such operations, the oil is raised to and maintained at cracking temperature and under a relatively'high superatmospheric pressure for a predetermined period of time. Theoil is then passed into a zone of substantially lower pressure wherein a substantial portion of the conversion products, with the exception of the heavy tan-like residues, is vaporized by the contained heat of the oil. The tarry residues are withdrawn from the system and the vapors are subjected to fractional condensation whereby the constituents heavier than those desired in the distillate product are condensed and separated from the desired low boiling products, such higher-boiling portions, if desired, being returned, along with fresh stock, to the original cracking operation.

In accordance with the present invention, the oil is brought to and maintained at cracking temperature and under a relatively high superatmospheric pressure for a predetermined period of time, as in the above type of operation, and is then subjected to successive pressure reducing stages under controlled conditions, whereby a number of advantages are secured, asmore fully pointed out hereinafter. v

Referring more in detail-t0" the drawing, th numeral 5 indicates a valved line leading from any suitable source of hydrocarbon oil which is to be converted into lower boiling hydrocarbon oils. The oil is supplied through line Sunder pressure by any suitable means, for example, a pump not shown), and is passed through a coil 6 in the upper portion of a fractionating column 1, wherein the oil is partially heated by hot vapors in the column. The oil passes from coil 8 into a line 8 provided with valvedbranch-pipes 9 and I0. Branch-pipe 9 leads to a coil I l mounted in the upper'portion of a flash chamber l2 and branch-pipe l0 leads to a coil [3 mounted within the upper portion of an evaporator chamber l4. Thus, all the oil being fed into the system may be passed to either of the coils II and I3, or closely controlled portions of it may be fed simultaneously to coils l l and 13. The oil from coil l3 passes through line |5 into a second coil l6 mounted below coil l3 in the upper portion of evaporator chamber I4. Trap-out plates H and !8 are provided in the evaporator chamber i below coils I 3 and I6, respectively. The oil after passing through coils I3 and 16, passes into a line l9 leading to a lagged stock supply or .mixing drum 20 and the oil from coil ll passes into a line 2! which is connected to the line l9. Oil fed to coil II in tower l2 and to coils I3 and IS in tower I4 is thus again collected,'after preheating, in line [9 and mixing drum 20.

In drum 2B the preheated fresh stock is admixed with hot oil products introduced therein through lines l9, 33 43 and 41, as will be hereinafter described. A preheated mixed or composite feed stock is thus-collected in the drum 2!).

A line 22 leads from the bottom of mixing drum 2!] to a hot-oilpump 23, by which the hot composite feed stock from drum 20 is forced through line ?2 to a heating coil ZA-suitably mountedin a combustion furnaceshown diagrammatically at 25. The heated oil is brought to the desired cracking temperature in coil 24 and then passes through line 26 to a reaction chamber or soaking drum 21, the line 26 being preferably con'nected to one end of the chamber 21. During" its pas-.

sage through coil 24,the oil is'heated to cracking or conversion temperature, under a high super atmospheric pressure, for example, above 450 lbs., and preferably750 to 900 lbs., and fiowsat a velocity sufficient toavoid substantial deposition of coke withinthe coil 24. The" highly heated products discharged from coil 24 into chamber 21 are maintained therein'at cracking temperature and under 'superatmospheric pressure, ap-

proximately that at the coil outlet, for example,

a temperature of 875 F. and a pressure of 750 lbs. may be maintained in the chamber 21. The highly heated productsare passed from the other end of the chamber'through a line 28 pressure lower than that'maintained in the reaction chamber 21, but in general exceeding lbs; gauge. For example'a pressure of from to 225 lbs; may be; maintained in chamber [4, a preferred range being from 'to 200 lbs.'- Under these conditions, a substantial vaporization of light products takes place, but at a higher temperature (above 735'F., preferably above 750 F. and at which cracking takes place at a s'ubstantial rate) and' with a lower proportion of volatilized products heavier .than .the desired low-boiling products than in operation as hitherto practiced, wherein the cracked products were separated at reduced pressurs'of, say 60 lbs. or lower At the same time, the unvaporized liquid or tar, being of lighter grade, may be maintained at the higher temperature prevailing, at which cracking occurs without excessive or disturbing carbonization.

The separated vapors ascend the tower M and come into intimate contact with downflowing reflux; whereby any heavy entrained constituents are removed. This reflux which contains heavier constituents of the vapors is condensed therefrom by the cooling action of the fresh stock flowing through coils l3 and i6, and collects on the trap-out plates I l and I8 from which any portion of the condensate may overflow into the lower portion of the evaporator tower. The amount of such condensate which overflows may be closely controlled by withdrawing predetermined portions of the condensate collected on the trap-out plates I l and I8 through valved lines 33 and 34, respectively. The condensate so withdrawn from plates H and I8 through lines 33 and 34 is passed through line 33* to the drum 20 where it is mixed with the other constituents of the feed stock supplied to the coil 24 in the manner already described. Ordinarily it is preferred to effect condensation of vaporous products above the plate I! which are lower boiling than those condensed above plate l8 and below plate ll, the resulting heavier condensate on plate I3 being permitted to overflow plate l8 and the resulting lighter condensate on plate [1 comprising substantially clean stock which is passed to the composite stock tank 20. The heavier condensate thus permitted to overflow plate 18 functions to remove entrainment from the vapors in the por tion of tower-I4 below plate l8.v The portion of the tower l4 below the trap-put plate l8 may be provided with a plurality of elements (not shown) for effecting intimate contact of the vapors and liquid therein and removing entrained matter from the vapors, such as baiile plates, screen plates, ring and disk plates, or the like. The latter plates have the advantage of less tendency to coke up. s f

The remaining, vapors are passed from the upper end of tower l4, through a valved line 32, to the lower portion of the fractionating'column 7 wherein they are fractionated, to separate the constituents heavier than those desired in the low-boiling product or gasoline.

The separated unvaporized liquid or tar is removed from the bottom of evaporator tower l4 through line 30 provided with a suitable pressure reducing valve 30, and passes through one of the valved branch lines 3| into thev low-pressure flash chamber, or tower, l2. A low superatmospheric or approximately atmospheric pressure is maintained within the tower l2, whereby substantially all but the heavy residual constituents of the liquid or tar, passed th'e'reinto from tower H is flashed into vapors by'the contained heat of such products, the flashed vapors constituting desirable chargingfstock for a cracking operation wherein, low-boiling oils, such as gasoline, are produced. For example, the tower l2 may be maintainedunder atmospheric pressure, or slightly thereabove, say from 1 to 30 lbs. gauge. The interior of the tower 12 may be provided with a plurality of baflle elements 35 for eifecting intimate contact between ascending vapors and de scending liquid therein, which maybe similar to those provided within the tower M. The heavy residue is withdrawn from the bottom of tower l2, and from the system, through a valved line 31. The flashed vapors ascend the tower lZiand come into intimate contact with cooler down- 7 charged through a valved line 42.

flowing liquid whereby any entrained tarry residues may be removed therefrom. This cooler liquid may comprise certain heavy fractions condensed from the vapors by the cooling action of the coil i i through which is passed the relatively cool fresh stock, as already described.

The vapors pass out of the upper end of tower 12, through a valved line 38 to a condenser 39, wherein they are condensed. The condensate, together with any uncondensed vapors or gases, passes from condenser 39 through a line 40 to a separator drum 4| wherein the liquid condensate and vapors or gases separate, the latter being dis- 7 The condensate is drawn from separator 4 I, through a valved line 33, by pump 43 and forced to the mixing drum 5% and/or through pipe line 43 into the upper portion of tower M at a point above plate 57. Thus, any portion of the condensate from separator 4i may be permitted to overflow the plate H to function as a reflux medium for the portion of column 44 therebelow. The fractionated vapors, supplied to column 7 from tower I4,

pass out of the top of column I through a valved line 19 to a condenser 50, wherein they are condensed. The condensate formed in condenser 50, together with any remaining vapors or gases, passes from condenser 50 through line 5! to a separator 52. The condensate, which is the desired pressure distillate product, is withdrawn from separator 52, and from the system, through a valved line 53 which may lead to a suitable stabilizing operation or to a gas release tower connected to an absorption plant, before going to storage. The gas which at this pressure is practically free of any constituents desired in the distillate product, is withdrawn from separator 52 through a line 54 connected to valved lines 55 and 56. The line 55 leads from the system and the branch-line leads to the lower portion of the second flash tower l2, whereby all or any portion of the gases may be introduced into the body of liquid residue products therein to aid in stripping therefrom thelower-boiling constituents.

The condensate formed in the column! is withdrawn from the, bottom of the column I through line 47 by pump 48 and forced to the mixing drum 20. Low-boiling hydrocarbons, desired in the gasoline distillate, are stripped from the condensate within column, '1 by means of steam admitted through 47 or by other means. The necessary cooling in the upper portion of column 1 may be effected in whole, or in part, by the passage of fresh feed stock through coil 6. If desired, additional cooling may be effected by passing a cooling mediumthrough coil 44.

I Any vapors given ofi within the mixing drum 20 may be withdrawn therefrom and passed through valved vent line 5! into tower 14, preferably the upper portion thereof.

Steam, or other inert gas, may be introduced into the liqiud in the lower portion of flash chamber 12 instead of the gases from separator 52; However, since these gases are under a relatively high pressure it has been found that they are capable of effecting the desired stripping of the heavy tar residues in the bottom of chamber 12 and hence it is preferred to so employ them.

In a specific operation, gas oil having a gravity of 29.4 Be. was charged into the system through linei;

' In the operation of the process, for example, with a gasoil cracking stock and-with a temperature in the reaction chamber 21 of approximately 875 F. and a pressure of about 750 lbs.,

the unvaporized liquid or tar in the evaporator l4 may be maintained at a temperature of 750 to 825 F. and under a pressure of 125 to 150 lbs., the liquid in tower l4 having a gravity of 10 tov 12 A. P. I. Under these conditions, of pressure and temperature, additional cracking is effected in the body of tar in tower M at a substantial rate, but without disadvantageous coke formation. With similar stock and heating-conditions, but

with lower pressures, below lbs. for example,

in the evaporator tower M, a much heavier tar forms therein under very considerably lowertemperatures, say 700 to 715 F., under which conditions no substantial cracking occurs, or'if the temperature of the tar body were raised, serious and disadvantageous coking Would occur.

.. Under the conditions above set forth for operation in accordance with the present invention, the

vapors are released in the evaporator tower M at substantially higher temperature, 750 .to 825 F., or higher, and are hence available to secure a higher temperature or" preheating in the feed stock passed through the coils I3 and I6, and also in the reflux condensates withdrawn through the lines 33 and 3 5, and, as a result, the composite feed stock in the feed tank 28 is maintained at substantially higher temperatures, say 35 to 50 F. higher than with lower pressure prevailing in the evaporator tower. M, as in prior practice. Furthermore, the additional cracking taking place in the tarry body in the evaporator l4 results in the formationof additional vaporizable constituents, which are released when the tar is discharged into the flash tower i 2, and these additional light constituents are made available for cracking or condensation in the condenser 39 and return to the composite feed tank 25. Although these advantages are secured, at the same time, the conditions prevailing in the evaporator tower l are suo that the reflux condensate condensed therein and returned to the composite feed tank 29 is likewise at a somewhat higher temperature than has been the case in prior-practice.

The operation of the evaporator 14 and the fractionating column I may be so controlled as to secure a condensation of constituents heavier than the desired products in the upper portion of the tower I t, and a condensation and stabilization of the desired products in the fractionating column I.

It will be apparent that the details of the apparatus and process as set forth hereinbefore may be materially modified within the scope of the invention, and are not intended to be regarded as limitations upon the scope of the invention, except as set forth in the accompanying claims.

I claim:

1. The method of converting higher boiling hydrocarbon oils into lower boiling hydrocarbon oils which comprises heating such oil to a tem perature of at least 850 F. while maintaining it under a superatmospheric pressure of at least 750 lbs. per square inch, passing the highly heated oil to a zone of substantially lower superatmospheric pressure of at least lbs. per square inch wherein the desired low-boiling products together with a portion of the products heavier than the desired products are vaporized by the contained heat of the oil and the unvaporized products are maintained at a temperature of at least 750 F., separately withdrawing the vaporous and unvaporized products, passing the unvaporized products from said low pressure zone to another zone of still lower pressure wherein substantially all of the remaining heavier constituents thereof desirable as cracking stock are vaporized by the contained heat of the said prodthe uncondensed constituents thereof through the unvaporized product in said second-named low pressure zone before the' latter is withdrawn therefrom.

.2. The method of converting higher boiling hydrocarbon oils into lower boilinghydrocarbon oils which comprises heating such oil to a temperature of at least 850 F. while maintaining it under a superatmospheric' pressure of at least 450 lbs. per square inch, passing the highly heated oil to a zone of substantially lower superatmospheric pressure of at least 100 lbs. per square inch wherein the desired low-boiling prbducts together with a portion of the products heavier than the desired products' are vaporized by the contained heat of the oil and the unvaporized products are maintained at a temperature of at least 750F., separately withdrawing the vaporous' and unvaporized products, passing the unvaporized heavier products from said low pressure zone to another zoneof still lower. pressure wherein substantiallyall of the remaining heavier constituents thereo'fdesirable as cracking stock are vaporized by'the contained heat' of the said products, separately withdrawing the vaporous and unvaporized portions, subjecting th vaporous products from said second-named low pressure zone to a condensing operation, passing the resulting condensate to the oil undergoing cracking, and passing a portion of the vapors from said first-named low pressure zone through the unvaporizedproduct in said secondnamed low pressure zone before the latter product is withdrawn therefrom.

3. The method of converting higher boiling hydrocarbon oils into lower boiling hydrocarbon oils which comprises heating such oil to a temperature of at least Z50" F. while maintaining it under a high superatmospheric pressure, passing the highly heated oil to a zone of substantially lower superatmospheric pressure of at least 100 lbs. per square inch wherein the desired lowboiling products together with a portion of the products heavier than the desired products are vaporized by the contained heat of the oil and the unvaporized products are maintained at a temperature of at least 750 F., separately withdrawing the vaporous and unvaporized products, passing the unvaporized products from said low pressure zone to another zone of still lower pressure wherein substantially all of the remaining heavier constituents thereof desirable as cracking stock are vaporized by the contained heat of the said products, separately Withdrawing the vaporous and unvaporized portions, subjecting the vaporous, products from said second-named low pressure zone to a condensing operation, passing the resulting condensate to the oil under going cracking,subjecting the vapors from said first-named low pressure zone to a condensing operation, and passing the uncondensed constituents thereof through the unvaporized product in said second-named low pressure zone before the latter product is withdrawn therefrom.

4. The method of converting higher boiling hydrocarbon oils into lower boiling hydrocarbon oils which comprises heating such oil to a temperature at least 850 F. while maintaining it under a superatmospheric pressure of at least 750 pounds per square inch, passing the highly heated oil to a zone of substantially lower superatmospheric pressure of at least lbs. per square inch wherein the desired low-boiling products together with a portion of the products heavier than the desired products are vaporized by the contained heat of the oil and the unvaporized products are maintained at a temperature of at least 750 F., separately withdrawing the vaporous and unvaporized products, passing the unvaporized products from said low pressure zone to another zone of still lower pressure wherein substantially all of the remaining heavier constituents thereof desirable as cracking stock are vaporized by the contained heat of the said products, separately withdrawing the vaporous-and unvaporized portions, subjecting the vaporous products from said second-named low pressure zone to a condensing operation, passing the resulting condensate to the oil undergoing cracking, subjecting the vapors from said first-named low pressure zone to a fractionating operation wherein the heavier constituents thereof are condensed as reiuX condensate, subjecting the fractionated vapors to a com densing operation, and passing the uncondensed constituents thereof through the unvaporized product in said second-named low pressure zone before the latter is withdrawn therefrom.

5. The method of converting higher boiling hydrocarbon oils into lower boiling hydrocarbon oils which comprises heating such oil to a temperature of about 900 F. while maintaining it under a superatmospheric pressure of about 750 lbs. per square inch, passing the highly heated oil to a zone of substantially lower superatmospheric pressure of at least 100 lbs. per square inch wherein the desired low-boiling products together with a portion of the products heavier than the desired products are vaporized by the contained heat of the oil and the unvaporized products are main tained at notless than 750 F., separately withdrawing the vaporous and unvaporized products, passing the unvaporized products from said low pressure zone to another zone of still lower pressure wherein substantially all of the remaining heavier constituents thereof desirable as cracking stock are vaporized by the contained heat of the said products, separately withdrawing the vaporous and unvaporized portions, subjecting the vaporous products from said second-named low pressure zone to a condensing operation, passing the resulting condensate to the oil undergoing cracking, subjecting the vapors from said firstnamed low pressure zone to a fractionating operation wherein the heavier constituents thereof are condensed as reflux condensate, passing said reflux condensate to the oil undergoing cracking, subjecting the fractionated vapors to a condensing operation, and passing the uncondensed constituents thereof through the unvaporized prod uct in said second-named low pressure zone before the latter is Withdrawn therefrom.

ROBERT E. WILSON.

Images