US2402893A - Conversion of hydrocarbon oils - Google Patents

Description

June 25, 1946.l s. H, HULSE CONVERSION QF HYDROCARBON OILS Filed July 11, 1942 III" .WU (NORM.

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WU (E sul Patented Junel25, 1946 UNITED STATES PATENT OFFICE coNvEasIoN or mRocAaaoN ons Stewart H. Hulse, Westfield, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application July 11, 1942, serial No. 450,545

Thi.y invention relates to the conversion of TA*.vdrccarbon oils and pertains more particularly .e process for the vconversion of high sulfur crude oils or fractions thereof into gasoline and intermediate distlllates, such as kerosene, heating oil and Diesel fuel.

It has heretofore been proposed to crack hydrocarbon oils in the presence of an active catalyst to form gasoline. In addition to the production of gasoline, other low boiling distillate derived from high sulfur crude oil, the trade gas loil fraction of the catalytic operation usually contains excessive amounts of vsuliurwhich cannot be readilyremoved without extensive desulfurizing treatment.

For example, a relatively light fraction from a high sulfur-bearing crude comprising 35% to '10% of the original crude, having a mid-boiling 30 point of about 600 F. and containing about 1.2% sulfur` will. when subjected to catalytic cracking treatment, produce a trade gas oil having a sulfur content of about 0.9%, which will normally meet trade specifications forl this type of oil. However, if a heavier fraction from the same source of high sulfur crude, having a mid-boiling point of '750 F. and comprising 50% to 80% of the original crude and having a sulfur contentv of 1.6%, is catalytically cracked under the` sameconditions, the sulfur content of the trade gas oil produced will be of the order of about If a still higher boiling fraction of the original One of the primary objects of the present invention is to provide a process for the conversion of hydrocarbon oils having a, high sulfur content which'will retainthe advantages realized by catalytic cracking and which will at the same time produce a trade gas oilhaving, a relatively low' sulfur content vcapable of meeting sulfur cracking operation is applied to heavier fractions specifications for this type of oil without further `desuliurizing treatment.` l0

It has been found. that by subjecting aihighboiling crude oil fraction'containing a relatively high percentage of sulfurnrst to mildthermal crackingl treatment' and then subjecting the vaporus products from 'thethermal cracking treatment to catalytic cracking. the gasoline fraction formed from the catalytic cracking operation will be of the saine Vhigh quality as that .obtained by direct catalytic cracking. of the original high sulfur oil ',withoutpreliminary thermal ,cracking andI in additionl the trade gas oil distillate will be materially lower in sulfur. Expressed in another way, the' preliminary mild thermal cracking treatment prior to thev catalytic cracking operation reduces' the percentage of sulfur contained in the gasoline and trade gas oil fraction resulting from the catalytic cracking opera- 'tion subsequently carried out.

Having set forth the general nature and objects the invention will be better understood from the more detailed description hereinafter, 'in which reference will be made to the accompanying drawingwhich is a diagrammatic illustration of an apparatus suitable for carrying the invention into eiect.

Other objects and advantages of the invention crude, having a mid-boiling point above 950 45 F., for example, comprising '10% to 85% ofthe crude and having la sulfur rcontent of 1.9%, is catalytically cracked, ythe trade gas oil obtained from the cataytic cracking operation will contain about 1.6% oi' sulfur. The trade gas oils produced from the last two cracking operations will contain excessive sulfur which will`require further desulfmizing treatment in order to meet the maximum sulfur specifications for this type of oil.

will also be apparent from the more detailed description hereinafter. A*

Referring to the drawing, the reference character l 0 designates a charge line vthrough which a crude oil containing a relatively highper'centage of sulfur is introduced into the system. The crude pil is charged through line l0 to a crude still furnace Il in whichthe oil is heated to a temperaturesuiiicient to vaporize the'lowerboiling fractions, such as the gasoline andftrade gas oil constituents. The oilv during its passage through the heating furnace Il may be heated, forexample, tol a temperature of from 600 F, to ov F.

The oil after passing through the crude still I I may discharge into a separating and fractionating tower l2 in which the vapors formed during the heating are liberated from unvaporized residue. The unvaporized residue, together with any initial condensate formed in the bottom sec- 3 tion of the fractionating tower i2, is removed there-from through line i3 and treated as hereinaiter described. l

The crude fractionating tower l2 may be provided with a trap-out tray II having a central vapor passage through which vapors liberated in the bottom section of thetower may pass into the upper portion thereof. .The temperature of the tower above .the trap-out tray Ilmay be controlled by suitable reflux medium. cooling 'elements and the like to condense the constituents boiling in the trade gas oil range. such as constituents boiling between 00 F. and 700 F.

The condensate formed in the upper section of the tower i2 coliects in the trap-,out tray i5 and is withdrawn therefrom through line i6 and a portion of the raw gasoline removed from the bottom oi the receiver 2l may be passed through line 23 and pump 2l into the upper end of thel tower I2 as a reflux medium therefor. Gases separated from the distillate in the receiver 2| may be removed therefrom through line 25.

Residual oil removed from the bottom section of the crude fractionating tower I2 through line i3 is charged to a pump 2t in which it is placed under a pressure ranging. for example, between 100 and 500 pounds per square inch, after which it is charged to a viscosity-breaking furnace 21 in which the o il may be heated to a temperature of from 700 F. to 900 I". and maintained at said temperature for a period sumcient to reduce the viscosity of. the oil. I'he oil during its passage through the viscosity-breaking furnace. 21 is subjected to mild 'cracking treatment to fonn from 5% to 15% cfgasoiine. It will be imderstood thatthe object. of this thermal treatment is not to produce gasoline but to pretreat the oil to fox-ni a final :trade gas oil having a low sulfur Vapor-ous products liberated in the separator 28 are removed overhead to a fractionating tower 42 in which the vapors are subjected to fractionation. The fractionating tower 42 may be provided with a trap-out tray Il for segregating condensate formed in the tower l2 into fractions of different boiling range. The higher boiling condensate formed in the bottom section of the fractionating tower 42 is removed from the bottom thereof through line M and subjected to catalytic cracking, as later described.

The temperature. of the top section of the iractionating tower d2 may be controlled tocondense the trade gas oil fraction of the desired boiling range formed during the viscosity-breaking treatment. The viscosity-broken trade gas oil condensed in the upper section of the tower d2 is collected in the trap-out tray il@ and is withdrawn through line 5E to the trade gas oil storage teni: il.

vapors remaining uncondensed in the tcp section of the fractlonating tower d2 are removed overhead through line 46 to condenser l inwhich gasoline formed during-the viscosity-breaking operation is condensed. Products from the condenser l1 Vmay pass to a receiver 48 in which the gasoline distillate separates from normally gaseous constituents. The normally gaseous ccnstituents are removed from the receiver I8 through line I9 having a release valve Si for maintaining the desired pressure on the viscositybreaking and fractionating equipment. The raw active cracking catalyst, such as, for example,

content. Thedegreeof cracking carried out in the viscosity-breaking furnace 21 is controlled .to obtain this `objective rather than for the production of gasoline. The viscosity-broken products from the furnace 21 pass into a separator 2l in which vapors separate from unvaporized residue.

The unvaporlzed residue may be withdrawn from the separator 28 through line 2! and passed through a reducing valve 3| into a tar flashing chamber 32 in -which further'vaporization is obtained. vapors liberated in the tar flasher 32 pass overhead throughline 33 to a condenser 3l and thence into a receiver 35.

condensate from the tar flashing chamber 32 collecting in thereceiver 25 may be withdrawn through line 3B from the process or it may be passed through line 31 and further processed. as hereinafter described. Uncondensed vapors and gases from the product receiver' 38 maybe vented to a fuel gas line through line 38. Viscositybroken tar of desired gravity is withdrawn from the tar separator 32 through line 39 as a product ofthe process. If desired. steam or other stripping gas may-be introduced into the tar flasher- 22 to aid in vaporizing the .cil therein.

gasoline distillate separated inthe receiver 48 may be withdrawn from receiver 48 through line 52 and may be removed from the system through line I3 or passed tothe catalytic cracking unit,

as later described.

The condensate formed in the bottom section of the fracticnating tower 42 and withdrawn therefrom through line M is intermixed with a iinely divided active cracking catalyst discharging through line 54. This catalyst may be any activated clays and synthetic gels comprising silica-alumina, silica-zirconia, bona-alumina, silica-magnesia, or mixtures thereof. I'he catalytic material discharging through conduit 54 into the oil stream passing through line 44 is preferably at a'temperature suicient to raise the oil to active cracking temperature. The temperature of the catalytic material introduced into the oil stream may range' from 1000 F. to l200 F. 'Ihe amount of catalytic material so introduced may be controlled to bring the oil to the desired cracking temperature, which in turn may be of the order of from 800 F. to 1000 F. The mixture of oil vapors and finely divided catalyst resulting from the intermixing of the hot catalytic ma,

teria] withvthe oil passing through line 44 continues through line 55 to a distributing nozzle 56 located in the bottom section ci' the catalytic converter 51. The upper end of the distributing nozzle 56 .is preferably in the yform of a perforated grid which uniformly distributes the mixture through the catalytic converter.y The veferred to employ catalytic material having a particle size such that from 60%' to 80% is capable of passing through a 40G-mesh screen. The depth ofy the relatively dense mass of catalytic ma maintained in the converter I1 is vcontrolled to` maintain the desired contact time to obtain the required conversion. f

The cracked vapors containing some entrained nely divided catalytic material, after passing through the dense turbulent bed of catalytic material in the. converter 81 may pass into a. cyclone separator 88 located in the topvsection of the converter 81. Catalytic material removed from the cracked vapors in the cyclone separator 88 may be returned to the main body of catalytic material through line I8. 'I'he cracked vapors after passing through the cyclone separator 88 may continue through line 8| to a fractionating tower 82 in which the products are subjected to fractionation to separate the higher boiling constituents therefrom. The fractionating tower 82 is line 85 or it may be recycled through line 8 8 and pump 81 to the oil line M and intermixed with oil passing to the converter 51. The temperature of the top section of the fractionating tower 82 is controlled to condense a trade gas oil fraction which collects in the trap-out tray 88 and is removed through line 88. This trade gas oil frac.-4 tion is passed from line 88 into trade oil storage tank l1 wherein it is blended with virgin trade gas oil kand gas oil from the viscosity-breaking operation. Due to the initial viscosity-breaking treatment, the trade gas oil collected in the trapout tray 83 will have a relatively low sulfur content so that the resulting blend of trade gas oil formed from the process will meet sulfur specifications without further treatment.

Vapors remaining uncondensedin the fractionating tower 82 and comprising catalytically cracked gasoline constituents together with normally gaseous hydrocarbons are removed overhead from the tower 62'through line 88 to a condenser 1| in which th'e catalytically crackedgasoline is condensed. Products from the condenser 1I may pass to a product receiver 12 in which the catalytically cracked gasoline segregates from normally gaseous constituents. The gaseous consttuents formed in the catalytic cracking operation are removed from the receiver 12 through line 13 and the gasoline is removed from the receiver 12 through line 14. If desired, a portion of the gasoline may be returned through line 15 and pump 18 to the upper end of the fractionat-f ing tower 82 as a reiiux medium therefor.

Returning/to the catalytic converter 81, catalytic material contained therein is continuously -removed from the bottom thereof through con- `duit 11. If desired, a stripping gas may be introincreases the temperature oi the catalytic matef rial. The bottom of the regenerating chamber 83 may be in the form of an inverted cone. above which maybe positioned a perforated grid plate '84 through which the mixture oi catalytic material and air discharges into the main body of the regenerating chamber. l

'I'he velocity of the regenerating gas passing upwardly through the regenerating chamber 88 is also preferably controlled `to maintain a dense turbulent body of catalytic material undergoing regeneration within the regenerating chamber 88. To this end, the velocity of the air or oxidizing gas may be of the order or from 0.5 to 5 feet per second. Ihe catalytic material is retained within the regenerating chamber 8,3 for a period suiiicient to burn the desired amount of carbonaceous deposits therefrom and to heat the catalytic material to the desired temperature for supplying the required heat for the cracking operation, as previously described. In cases where f the amount of 'carbonaceous deposits burned from the catalyst is insulcient to supply the required heat for the cracking operation, additional fuel may be supplied to the regenerator to heat further the catalytic material.

v'lhe regenerated catalytic material is continu. ously withdrawn from the regenerator 88 through a conduit 88 projecting upwardly from the `bottom of the chamber into the space above the perforatedgrid plate 84. The conduit `85 discharges in to the conduit 54 from v whichv the catalytic material is passed through control .valve 88 into the oil stream 4I, as previously described.

tends to burn any carbonaceous deposits formed The spent regenerating gas after passing through the catalytic material in the regenerator 83 continues to a cyclone separator 81 located in the top section of the regenerating chamber for removal of entrained catalytic material carried in the combustion gases. The spent combustion gases are removed from the cyclone separator 81 through line 88 and may be vented to the atmosphere Vor passed to a Cottrell precipitator or other types of solid-gas separating devices for further purification of the gases.

The conduit 11 employed for removing the spent catalytic material from converter 51 and the conduit 8l for removing the regenerated catalytic material from the 'regenerator 83 may be in the form of a standpipe in which sufficient pressure is built up 0n the catalytic material to cause it to circulate through the catalytic converter and regenerating chamber. In order to develop a hydrostatic pressure in the conduits 11 and M, it is important to maintain the iinely divided material in a freely flowing fiuidized state during its passage through these conduits. To this end an aerating gas may be introduced at one or more spaced points along the conduits 54 and 11.

While I have described a conventional type of fluid catalyst cracking equipment for carrying out the catalytic cracking operation in which the catalytic material is continuously circulated through the cracking and regenerating zones by hydrostatic pressure developed by means of standpipes, it will be understood that other types of catalytic cracking equipmentmay be employed for carrying out the present invention.

Referring again to the receiver ll, wlmh collects the overhead products from the tar flasher 32, the liquid condensate coli-acted in this receiver may bepassed through lines 31 and II. pump B1 l and line M yto the catalytic converter l1 and subkjected to catalyticzconversion,,as'previously deiscribed Also, the gasoline obtained from the .viscosity-breaking treatment and collected in re- N. ceiver t8 may also be passed through line Stand @inter/'mixed with oil from line M passing to the catalytic converter 51. y Having described the preferred embodiment of fthe invention, it will beunderstoodthat it embraces` such other variations and modifications as come within the spirit and scope thereof.

What is desired to be protected by Letters Patent is: l. A Iprocess for producing trade gas oil of low sulfur content from high sulfur-bearing oil which comprises subjecting all of said high sulfur-bearing o'l to mild therma1 cracking treatment, fractionating the cracked products to segregate a trade gas oil fraction and a heavier fraction, removing the trade gas oil fraction to storage, subjecting said heavier fraction to further cracking treatment in the presence of an active cracking catalyst, fractionating the cracked products'from the last-named cracking treatment to obtain at least a trade gas oil fraction and a heavier fractionand recovering said trade gas oil fraction as a trade gas oil of low sulfur content and removing the same to storage.

2. In the process defined by claim 1, the further improvement which comprises mixing the Vtrade gas oil fraction segregated from the cracked products from the thermal cracking treatment with the trade gas oil fraction segregated from the cracked products from the catalytic cracking treatment to recover a total trade gas oil of low sulfur content.

3. A processfcr producing tradegas oils having a low sulfur content from high sulfur-bearing crude oils which comprises initially subjecting said crude oil to distillation and fractionation to segregate a. trade gas oi1iraction andaeheavier residual fraction, removing the trade gas oil fraction to storage, subjecting all ofA said residual fraction to mild thermal cracking treatment. fractionating the cracked products from said thermal cracking treatment to segregate a trade gas oil fraction anda heavier-fraction, removing the trade gas oil fraction to storage, subjecting said heavier fraction to further cracking in the presence of an active cracking catalyst, ,fractionating the cracked products from the last-named cracking treatment to obtain at least a trade gas oil and a heavier fraction-and recovering said trade gas oil fraction as a trade gas oil of low sulfur content and removing the same to storage.

4. In the process dened by claim 3, the turther improvement which commises combining the initial trade gas oil resulting from the distillation and fractionation of the crude with the trade gas oil from the thermal cracking treatment and the trade gas oil from the catalytic cracking treatment' to Vrecover a total trade gas oil of low sulfur content.

5. In theprocess dened by claim 3, the further improvement which comprises combining the gas oil fraction resulting from the thermal cracking treatment with the trade gas oil fraction from the catalytic cracking treatment to recover a total trade gas oil of low sulfur content.

STEWART H. Huren.

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