Patentecl Aug. 31, 1954 2,687,986

TATS A OFFlCE 2,687,986 CONVERSION J ames M. Jennings, Baton Rouge, La., and George F. Pappas, Metuchen, N. J., assìgnors to Stand ard @il Development Company, a corporation of Delaware Application May 1, 1951, Serial No. 223,938 5 Claims. (Cl. 196-49) l 2 The present invention relates to a process for severity of the thermal treatment, that the thermal conversion of hydrocarbonaceous is, by raising the temperature and/or extending materials. More particularly the invention per the cracking time. However, when so operating tains to an improved method of reducing the vis the quality of the product fuel cil, particularly cosity of heavy hydrocarbonaceous residues of its sedimentation characteristics are impaired to the type of topped or reduced crude or similar an extent which makes the fuel oil unacceptable materials by a thermal treatment suitable toy for most purposes. Therefore, a visbreaking op produce fuel oils of improved quality, gas oils eration permitting the production of increased and increased proportions of motor fuel range yields of and gas oil and simultaneously . Broadly, the invention provides of fuel oil in` smaller amounts but of satisfactory for subjecting heavy residues of the type speci sediment characteristics, has become a need fied to a viscosity-reducing or “visbreaking” strongly felt in the art of petroleumreñning. treatment at severe conditions suitable for the The present invention provides an operation of production of higher yields of gasoline and re this type. visbreaking the high-severity tar in It is, therefore, the principal object of this a second visbreaking stage at relatively mild invention to provide improved means for vis conditions conducive to the production of high breaking heavy residues of the type quality fuel Oil. specified, permitting the production of maximum In refining crude oil the first step is normally yields of motor and distillate fuels and relatively a simple or “topping” to produce 20 small yields of a high quality heavy fuel oil. distillate fractions and a heavy residue. In Other objects and advantages will appear from order to obtain maximum yields of high quality the subsequent description of the invention motor fuels, all fractions boiling above ‘the gaso wherein reference will be made to the accom line range and particularly those boiling above panying drawing, the single ligure of which is the range must be subjected to cata a schematical flow diagram of a system suitable lytic cracking. However, the heavy residum of to carry out an embodiment of the invention. conventional crude distillation boiling above It has now been found that the yields of low about 800° F. does not, as such represent a feed boiling distillates such as gas oils and gasoline stock suitable for catalytic cracking. Among the may be substantially increased over conven methods developed to produce satisfactory cata tional visbreak-ing at relatively mild conditions, lytic cracking feed stocks from these residues, without detrimentally affecting the quality of the viscosity reduction or “visbreaking” is one of fuel oil product, by subjecting the heavy vis the most widely used. breaking feed stock first to a visbreaking treat Visbreaking involves a treatment of reduced ment carried out at severe conditions conducive crude or the like at temperatures of about 780 to the formation of increased proportions of 35 950° F. and pressures of about 10G-1500 p. s. i. g. lower boiling _distillate oils and thereafter re- ` at feed rates of 1-'75 volumes per hour of oil at visbreaking the visbreaker tar from the severe 60° F. per cracking volume above '750° F. to pro visbreaking treatment in a second visbreaking duce by a mild type of thermal cracking about stage at conventional conditions, which are com 5~­15 vol. per cent of gas oil, about 5­15 vol. per paratively mild. The pitch feed to the second cent of gasoline and about 90-'70 Vol. per cent of 40 visbreaking stage is preferably asphaltic or vir heavy fuel oil. Speciiic conditions within the gin is preferably added to this pitch in ranges specified depend on the type of the vis amounts of 242%, in order further to improve breaker feed. The gas oil so formed represents the quality of the fuel oil produced. a feed stock suitable for the production of addi First stage severe visbreaking conditions in tional amounts of high quality gasoline by cata 45 clude temperatures of about 35o-975° F., pref lytic cracking or,l after suitable finishing, an ac erably about 920-960“ F., pressures of about 200 ceptable distillate fuel. Of the products formed 1100 p. s. i. g., preferably about 3004000 p. s. i. g. in visbreaking, the gasoline has the highest and and oil residence times at visbreaking condi the fuel oil the lowest value. In order to obtain 50 tions, corresponding to about 'l5 to 50 volumes the greatest product realization it is highly de per hour of oil at 60° F. per first stage visbreaker sirable, therefore, to reduce the fuel oil yields volume above 750° F. 'Specific conditions vary to a minimum while simultaneously increasing with the type of visbreaker feed. However, the the gasoline and gas oil yields to a maximum. conditions to be applied in this stage should be This may be accomplished by increasing the 55 more severe, Within the ranges specified, than 2,687,986v 3 4 the more conventional conditions employed in is reported in wt. per cent, sediments in excess the second stage. Particularly, the temperature of 0.25 wt. per cent being considered unsatisfac should be about 50-100° F. higher than the con tory. In previous operations the sediment of tar ventional temperatures of the second stage. Sim produced in unit A alone had been found to be ilar results may be accomplished by increasing satisfactory and never exceeded 0.25 wt. per cent. residence time, by, say, about 50-200%. By way In the combined operation described it was of example, conventional visbreaking conditions found impossible to blend appreciable propor to be maintained in the second stage may in tions of the high severity tar from unit B with clude temperatures of about 'TO0-900° F., pref the satisfactory low severity tar from unit A erably about r{8O-900" F., pressures of about 10 without producing blends exceeding the maxi 20G-1000 p. s. i. g., preferably about 500 to 1000 mum permissible sedimentation limit. This is p. s.> i. g., and residence times when using coil illustrated by the tar inspection data summar and upflow or downflow soakers corresponding ized in Table I below: to about 2.5 to 30 volumes per hour of oil at 60° Table I F. per second stage visbreaker volume above 15 '750° F. (v./v./hr.) or 10-30 v./v./hr. when using only a visbreaker coil. Run No ______- I II III All types of conventional visbreaking systems Tar Production Rate, 13, OOO-14, 000 13, 000-14, O00 13, OOO-14, 000 such as coil only, tube-and-tank type arrange Unit A, Bbl/day. 20 TarProduction Rate, 100 ______. 100+ ______50 ments, suspensoid, fluid or moving bed type of Unit B, BbL/day. . operations may be readily adapted to the present Sediment of Com- Too High____ Too High._._ 0. 13 bined Tars, Wt. invention. In accordance with a preferred ern Percent. bodiment of the invention, a tar-containing por tion or all of the liquid product from the severe visbreaking stage is retreated in a visbreaking The data of Table I show that even blends zone wherein fresh visbreaker feed is simultane containing as little as 100 bbl. of high severity ously visbroken at conventional mild conditions. tar per 13,000-l4,000 bbl. of satisfactory tar, i. e., The beneficial effects of the process of the in less than 1%, exceed permissible sediment limits. vention are demonstrated by the data reported Following the operation reported above the liq below which were obtained in commercial vis 30 uid product from the separator of high severity breaking operations. Two visbreaking units A unit B was fed t0 the furnace coil of unit A to and B were operated in parallel. Unit A was a gether with the regular feed of unit A. Sum conventional tube-and-tank type system in marized results of this operation are given in which a 13-15° API mixture of vacuum reduced Table II below: asphaltic and parañinic reduced crude, gas-oil Table II fluxed asphalt from a propane deasphalting op eration and bottoms from a slop rerunning op Run No ______. I II eration was heated in furnace coils to about 840° to 850° F., at a feed rate of about 16,000 bbl/day Conditions-Feed Rates to Unit: Regular Feed, BbL/day ______13,000 13,000. and at a pressure of about 300 to 1,000 p. s. i. g. 40 Liquid Product from Unit B, 1, 500 2,500. Bbl/day. at about 15 v./v./hr. above '750° F. The feed so Total Feed Rate, Bbl./day____ 14, 500 15,500. heated was discharged into a downñow soaking Coil Outlet Temperature, ° F__-_ 820-850 820-850. drum maintaining no appreciable liquid level, or Pressure, p. s. i. g ______. 400 400. Flash Drum Tar, Bbl/day (Es- 13,000-14,000 13,000-14,000. an incremental residence time therein, substan timat . tially at the conditions of the visbreaker coil. Flash Drum Tar Inspection: 0.11 Met Specifica­ The visbroken product was passed from the soak Sediment, Wt. Percent. tion. ing drum to a separator maintained at about '720 to 760° F. and about 25 to- 35 p. s. i. g. pres The data of Table II demonstrate that when sure. Separator overhead was fractionated in operating in accordance with the present inven a product fractionator While separator bottoms tion a visbreaker tar having satisfactory sedi were flashed into a ilash drum to atmospheric mentation characteristics may be produced from pressure and at temperatures of about 500 to 600° a feed about 15-25% of which is visbroken at F. The flash drum overhead was recovered t0 high severity conditions conducive to increased gether with the separator overhead While the yields of lower boiling distillates. Comparison flash drum bottoms were recovered as fuel oil of these results with those reported in Table I stock, all in a substantially conventional manner. proves the significant advantages of the process Unit B was a coil only system in which the of the invention with respect to the sediment feed consisting of 10-12" API mixture of vacuum characteristics of the fuel oil which may be pro reduced South Louisiana and Louisiana-Missis duced in high severity visbreaking operations. sippi crudes was heated in a furnace coil of semi 60 The considerable increase in the severity toler commercial scale to about 940 to 955° F. at a ance of the visbreaking process thus aiforded also pressure of 700 to '750 p. s. i. g. and a throughput permits a corresponding increase in total vis of about 24-29 v./v./hr. to obtain high severity breaker conversion and distillate yields without visbreaking. The visbroken product was directly detriment with respect to fuel oil quality. While passed to a separator maintained at about 350 to the coil outlet temperature in the second stage of 450° F. and about 100 to 125 p. s. i. g. pressure. runs I and II was at times lower that that speci The liquid product from the separator was iluXed ned above for conventional operation, subsequent with 30% light catalytic gas oil and flashed in operations indicate that no such temperature re the flash drum of unit A, so that the fuel oil duction is required in the second stage. stock recovered from this joint flash drum rep 70 Having set forth its objects and general na resented a mixture of tars produced at conven ture, the invention will be further explained by tional mild and high severity conditions. This the following description of the system shown in stock was blended with light catalytic gas oil the drawing which illustrates a preferred mode and tested for its sediment characteristics by a of practicing the invention. standard filtration procedure in which sediment 75 Referring now in detail to the drawing, the 2,6873986 5 6 system illustrated therein essentially comprises drawn through line 61 and supplied by pump 6,9 a conventional type low-severity visbreaking to .line 9 to be combined in line 5 with the virgin unit A and a high-severity type visbreaking feed to coil 'l as described above. unit B the functions and cooperation of which When operating substantially as described will be forthwith explained. above, the gasoline and gas oil yields obtained In operation, a virgin crude distillation residu from the total oil feed to Sections A and B are um such as a residue boiling substantially higher than those obtained by proc above about 800° F. may be supplied from line i essing of the same amount of feed in a system of by feed pump via line 5 to visbreaking coil '1. the type of section A alone. The increase in This feed stock is preferably an asphaltic pitch 10 gasoline yield amounts to about 20 to ri0% and or contains virgin asphalt. The oil supplied the increase in gas oil yield to about 10 to 60% from line i may have the temperature at which based on conventional yields. The amount of it is recovered from the crude still, say, about fuel oil produced in the case of two stage proc 50o-750° F. In line 5, the virgin oil feed is essing is about 3 to 8% less on the same basis mixed with about 15 to 20% of liquid high-severity 15 than that obtainable in single stage processing in visbreaker product obtained as` will appear here section A; however, fuel oil quality is equally inafter and supplied from line 9 at a temperature satisfactory in both cases. When the total feed 0f about 300 to 400° F. The mixed feed enters of sections A and B is processed in a system of low severity visbreaking coil 'l at a pressure of the type of section B alone, the amounts of gaso about '700 to 750 p. s. i. g. and is heated therein line and gas oil produced are higher, and the to about 820 ‘to 860° F. within a residence time amount of fuel oil produced lower than in the of about 2 to 5 minutes. The eñiuent from coil case of processing as described with reference l is passed through line il to downflow or up to the drawing. However, the fuel oil produced flow soaker i3 wherein it may be maintained by all-high-severity processing is not a saleable substantially at the temperature and pressure of 25 product. coil 'i for an additional say 1-15 minutes depend The operation described with reference to the ing on the soaker type, to complete the visbreak drawing permits of various modifications without ing reaction. The visbroken product is with a significant change in the contemplated results. drawn from soaker i3 through line i5 provided For example, soaker li may be used in high sever` with pressure release valve Il and passed to a 30 ity cracking section B providing for a larger oil vapordiduid separator I9 maintained at a pres residence time substantially at the temperature sure of about 30 to 35 p. s. i. g. and a temperature and pressure of coil 5i. In this case, the resi of about 720 to '760° F. Vapors separated in dence time in coil 5i may be substantially reduced separator l0 leaving via line 2l, are fed to a and its eñiuent passed through line 55 to soaker l’ l. conventional product fractionator 25. Distillate 35 The soaked product is withdrawn through line fractions may be recovered from fractionator 25 'i3 and may be passed directly to line 9 and from in any desired manner as exemplified by lines there 'to line 5 and coil 7. All or any desired por-, 2i, 2Q and 3l. Bottoms are withdrawn Via line tion of the effluent of soaker 7l may be passed 33 and and can be recovered wholly or in part via line 'i5 provided with release valve ‘il’ to sepa through line 35 for reprocessing in other opera~ 40 rator 5i and treated therein substantially as de« tions or may be returned to low severity coil 'l scribed above with reference to separator 9|. via line 35 with the fresh feed. Rather than passing the total effluent of coil 5 i» to Returning now to separator I9, the separated soaker ‘il it may be fed from line 53 via line liquid product is withdrawn through line 31 pro i9 to lines 9 and 5 and coil l. If desired, soaker vided with pressure release valve 39 and ñashed i3 of section A may be by-passed by the effluent at atmospheric pressure into flash drum 4|. of coil 'l via line 8l, in which case the residence Flash drum ¿Si may be maintained at a tempera time in coil 'l will be correspondingly increased ture of about 500° to 600° F. Stripping steam may to make up for the residence time of the by-passed be injected through lines 42. A distillate vapor soaker. In all modiñcations, except in the case fraction boiling below about 800° to 850° F. may in which soaker i3 is by-passed by line 8i, the 50 be removed via line dit to be further treated in high-severity visbreaker product ñowing through any conventional manner. The bottoms of flash line 9 may be added via lines 83 and Il directly drum ¿li are recovered through line 45 as product to soaker i3 to be subjected therein to the mild tar complying with fuel oil specifications. conditions of visbreaking section A. In place A second residual feed stock which may be of, or in addition to, the virgin oil feed supplied 55 the same as, or different from, that supplied through line I, an asphalt material such as via line l is fed from line 41, preferably at its asphalt-containing pitch or extraneous virgin production temperature, by feed pump 49 to high asphalt in proportions of about 2 to 12 wt. percent severity visbreaking coil 5l which it may enter based on the material in line 9, may be supplied at a pressure of about "700 to 800 p. s. i. g. Coil 60 through line 85 to be mixed with high severity 5i may be maintained at an outlet temperature visbreaker product in line 9. The addition of of about 900° to 975° F. and provide for an oil such materials through line 85 is particularly de residence time of about 1 to 4 minutes to complete sirable in cases in which a feed stock of relatively the visbreaking reaction. The visbroken product low asphalt content is supplied via line l. Either is withdrawn via line 53 and may be passed 65 one or both of the visbreaker coils 7 and 5I may through lines 55 and 5i provided with pressure re have the form of double coils operated in parallel, lease valve 59 to vapor-liquid separator 8l which in a manner known as such. Other modifica may be maintained at a pressure of about 0 to 150 tions within the spirit of the invention may ap p. s. i. g. and a temperature of about 350° to 450“ pear to those skilled in the art. Overhead vapors from separator El are with The above description and exemplary opera drawn through line 53 provided with release valve tions have served to illustrate specific embodi 65 and may be passed to product fractionator 25 ments of the invention but are not intended to ’ce treated therein together with the overhead to be limiting in scope. from separator i9 as described above. The liquid What is claimed is: products separated in separator 6I are with 75 1. In the process of producing distillate oils 2,687,986 7 8 and high quality residual fuel oils of low-sedi 5. In the process of producing distillate oils ment content by visbreaking heavy virgin crude and high quality residual fuel oil by visbreaking distillation residues, the improvement which com crude distillation residues, the improvement prises passing a feed stream consisting essen which comprises passing a feed stream consist tially of a virgin distillation residue boiling essen ing essentially of a virgin crude distillation resi tially above 800° F. through a visbreaking zone due boiling essentially above 800° F. through a under relatively severe conditions including a re visbreaking zone under relatively severe condi action temperature of 850 to 975° F., separating tions including a reaction temperature of 920 to the resulting hydrocarbon product into a vapor 960° F., a pressure of about 700 to 800 p. s. i. g. fraction and a first-stage residual tar fraction, 10 and an oil residence time of about 1 to 4 min mixing at least a portion of the separated tar utes, separating the resulting hydrocarbon prod fraction with another feed stream of a distilla uct into a vapor fraction and a ñrst-stage resid tion residue of an asphalt-containing virgin crude ual tar fraction, mixing the separated tar fraction stock boiling essentially above 800° F. to give a with another feed stream of a distillation residue mixture containing about 15 to 20 parts of the tar 15 of an asphaltic virgin crude boiling essentially fraction per 100 parts of the virgin stock, pass above 800° F. to give a mixture containing about ing the mixture through a second visbreaking 15 to 20 parts of the tar fraction per 100 parts zone under relatively mild conditions including of the virgin stock, passing the mixture through a reaction temperature of about 750 to 900° F. a Second visbreaking zone under relatively mild and a residence time corresponding to about 2.5 20 conditions including a reaction temperature of to 30 v./v./hr. above 750° F., the reaction tem about 820 to 900° F., a pressure of about 300 to perature in said second visbreaking Zone being 1000 p. s. i. g. and an oil residence time corre about 50 to 100° F. lower than the temperature in sponding to about 2.5 to 30 v./v./hr. above 750° said ñrst visbreakíng zone, separating the result F., the reaction temperature in said second vis ing hydrocarbon mixture into a vapor fraction 25 breaking zone being about 50 to 100° F. lower and a low-sediment residual tar fraction, and re than the temperature in said ñrst visbreaking covering the low-sediment tar. Zone, separating the resulting hydrocarbon mix 2. A process according to claim 1 wherein the ture into a vapor fraction and a second-stage mixture fed to the mild second visbreaking zone residual tar fraction, and recovering the said contains about 2 to 12% of virgin asphalt based 30 second-stage tar. on the tar fraction present in the mixture. References Cited in the ñle of this patent 3. A process according to claim 1 wherein the residence time in the severe first visbreaking UNITED STATES PATENTS zone is 50 to 200% longer than the residence Number Name Date 35 time in the mild second visbreaking zone. 1,981,842 Keith, Jr. ______Nov. 20, 1934 4. A process according to claim 1 wherein the 2,132,137 Watson ______Oct, 4, 1938 virgin residue fed to both visbreaking zones is 2,161,676 Houdry ______June 6, 1939 a vacuum reduced crude, about 15 to 25% of 2,166,177 Peterkin ______July 18, 1939 this reduced crude being introduced directly to 40 2,244,632 Phinney ______June 3, 1941 the severe first visbreaking zone While the bal 2,366,218 Ruthruff ______Jan. 2, 1945 ance of the reduced crude is introduced directly 2,388,055 Hemminger ______Oct. 30, 1945 to the mild second visbreaking zone. 2,507,523 Houdry ______May 16, 1950