US2252729A - Treatment of composite hydro carbons - Google Patents

Description

Patented Aug. 19, 1941 UNITED STATES PATENT, OFFICE' TREATMENT OF COMPOSITE HYDRO CARBONS Thomas B. Prickett, Woodbnry, N. 1., and George S. Dnnham, Ardmore, Pa., assignors, by direct and mesne assignments, to Houdry Process Corporation, Wilmington, Dei., a corporation of Delaware Application January 25, 1938, Serial No. 186,804 3 Claims. (01. 196-48) other origin, may also be treated according to this invention. The product or products desired may comprise low boiling hydrocarbons, such as gasoline and/or fractions higher boiling or lower boiling than gasoline, derived as products from a cracking of the starting material.

One object of this invention is advantageously to prepare a desired boiling range charge for a conversion operation, especially a catalytic cracking or transforming reaction, from a starting material of the type above indicated. Another object is to employ a fraction or fractions derived from the reaction or reactions of this invention to aid in controlling the boiling range of such charge which is to be cracked or converted. Another object is to control the process of this invention so that the size of apparatus employed may be minimized; or, conversely, so that its capacity may be increased. Another object is to obtain a high yield of desired product, such as gasoline, from a heavy high boiling starting material. A further object is to effect the heating of the starting material or charge so as to avoid the production of large amounts of deposits, such as coke, and to provide good operation of the still or other heating means. These and other objects and advantages, as well as a quick understanding of illustrative embodiments of the invention, will be readily apparent by reference to the accompanying drawings in which:

' Fig. 1 schematically shows exemplary apparatus for carrying out steps of process of this invention;

Fig. 2 is a modification oi the left-hand portion of the apparatus shown in Fig. 1; and

Fig. 3 is a modification of the right-hand portion of the apparatus ofFig. 1.

The modifications shown in Figs. 2 and 3 illustrate variations in certain aspects or features of the invention. It will be. understood that the apparatus illustrated in Fig. 2 may be combined with that appearing in the right-hand portion of Fig. 1 or with that shown in Fig. 3. Likewise, it is contemplated that the apparatus shown in shown in the left-hand portion ofFlg. l or that of Fig. 2.

or sent to storage.

' Fig. 3 may be employed in combination with that Referring more in detail to the drawings, in the several figures of which like reference characters denote similar parts, I is a heater, 2 indicates separating means such as a tar separator, 3 indicates reaction or cracking chambers containing contact material or catalyst 4,.and I is a fractionating column.

Referring especially to Fig. 1, the crude starting material or feed, e. g. a topped crude or other composite hydrocarbon material of high J boiling range and containing substantial amounts of diflicultly vapcrizable or unvaporizable components, may be forced at a high or substantial superatmospheric pressure through line 6 by pump I into the coils 8 within heater or furnace I. Heated fluid leaving coils 8 (having some liquid or possibly a substantial proportion of liquid present with vapors) may pass through line 0 and be expanded or reduced in pressure by passing through pressure release valve l0 whereupon a large amount of components previously in the liquid phase are converted into vapors. The resulting mixture of vapors and liquid pass through line H into tar separator 2, the latter having plates or members 2a of any suitable construction, for example perforated plates,

bubble plates or other fractionating devices, in-

cluding suitable packing. Vapors having the boiling rangerdesired for use as charge to the catalytic reaction cases are withdrawn as overheadfrom the tar separator through line I2 and are further heated, where further heating is desired, for example, by passing through coil l3 of heate'r I, and then are passed through line It into any one or more of the several converters 3. Hydrocarbon products of reaction may be withdrawn from the converters as indicated and passed through line It into rectifying column or fractionating tower 5, the latter having any sultable types of plates, trays or packing so as to effect the desired fractionation and to permit withdrawal of side streams at various levels along the height of the tower. A suitable fraction, such as gasoline and gases may be withdrawn as overhead from the fractionating column through line It, passed through cooler or condenser l1 and otherwise processed, stabilized, Any required part of any desired side stream fraction or fractions may be withdrawn from column 5 and passed through line l8 to be introduced as reflux into the tar separator 2, as illustrated.

A bottomsfraction may be withdrawn from v fractionatorS through line l9 and sent to steam stripper 20, overhead from the steam stripper being returned to the lower end of the fractionator throughline 2| and bottoms from the stripper being withdrawn through line 22 and either rejected from the-system, further treated as desired; or partially or wholly sent as reflux by lines 22a and I8 to the tar-separator 2.

Bottoms, from the tar separator 2 may be withdrawn through line 23 to be further processed in any desired manner, passed through cooler 24 to storage, or often preferably a desired proportion thereof, after being cooled somewhat, may be forced through line 24a back into the bottom of separator 2 in order to cool the mass of tar in the bottom of the latter sufliciently to avoid any substantial coking thereof.

The pressure under which the starting material is heated in coil 8 may be any substantial superatmospheric pressure, for example 200,

pounds/sq. in. gauge or less at the'outlet of coil 8, butusually at least 20 or more and ordinarily at least 40 to 60 lbs./sq. in. gauge at the outlet of said heating coil. Enough heat is added to the starting material'or feed in the coil 8 so that.

after suitable reduction in pressure of the feed upon passing through pressure release valve l0, a desired temperature such, for example, as 700 overhead withdrawn thrbugh line l2 from'the tar separator, but often it has a somewhat lower boiling range and may, for example, advantageously be a naphtha. The temperature at which the reflux is introduced into the tar separator 2 is usually (though not necessarily) at least several degrees below that of the overhead from the tar separator. i

to 800 F., more or less, e. g. 750 to 770 F., may 1 be maintained in the lower portion of the tar separator 2. The pressure in the tar separator will'in general be less than that existing within the coils 8 and may for example be in the range of approximately 20 to 50 lbs. per sq. in. gauge, the pressure in the tar separator being ordinarily about 25 to '75 or 100 lbs/sq. in., more or less,

below that at the outlet of the coils 8, one reason for this being to avoid vaporizing in the heating coils components of the starting material which it is desired to withdraw as liquid from the tar separator, thus'minimizing the size of apparatus for heating. It is important to maintain coil 8 under sufficient pressure so as to provide good operating conditions. The particular temperature and pressure conditions in coil 8 or equivalent will depend upon the starting material and typeof reaction. However, with many hydrocarbon starting materials, e. g. topped crudes, if

there is too high a percentage of vaporization,

too'much coke will be formed. This condition is also remedied or avoided by maintaining a suitably high pressure in coil 8.

The materials charged to the catalytic converters 8 through line l4. may be at a temperature of the order of 825 F. to 880 F., for. example, depending upon the-particular desired temperature of the contact material or catalyst 4, which may be 825 to 900 F., or, illustratively, may be about 850 F. or 880 F. where the catalytic material comprises an adsorptive silicious mass such as blends of silica and alumina of natural or arti- .ficial origin, or blends of silica with other suit- Water or steam may be introduced through line 25 into the coil 28 within the heater l and superheated steam withdrawn therefrom through line 21. Often some steam will be introduced into the starting material before or during its passage through coil 8, as for example through the valved line 28, so as to control mild cracking or viscosity breaking of higher boiling hydrocarbons which may, where desired, take place to some extent in the coil 8 during the heating step. Further amounts of steam may be introduced with hydrocarbons leaving coil 8, either into line 8 (preceding the pressure release valve III) or into line H (following the pressure release valve I 8) or partially before and partially after. Further amounts of steam, or other vaporizing medium or process fluid, may be introduced into the va-.

pors passing through line l2 into coil l3 so as to provide the desired amount thereof as process fluid and/or to provide the desired degree of superheat in the charge to the catalytic cases 8.

The modification illustrated in Fig. 2 will, in a general way, be understood from the description given hereinabove in connection with Fig. 1.

In the apparatus shown in Fig. 2, a starting material or feed, which may consist of material such as topped crude petroleum oil having sub stantial amounts of tarry, asphaltic, or difficultly vaporizable components, may be passed through line 6 and through coil 8 of the heater I, substantially as defined in connection with Fig. 1. However, in the apparatus shown in Fig. 2, a portion or all of the bottoms withdrawn from separator 2 through line 23 may be forced through line 29 into a second separator or tar fiashing' chamber 38. The pressure within chamber may be reduced by action of an ejector 3| in which a suction effect is provided-on the line 32 by a jet of. steam or the like introduced through line 33. Steam may be introduced into the separator 30 in any desired quantity through line 38 and unvaporized material may be withdrawn through line 35. The vapors leaving ejector 3| may pass through the line shown into a second ejector 38 wherein a jet of heated hydrocarbons from coil 8 provides a suction or jet action there'- on. Alternatively, vapors from ejector 3| may pass through line 31, either directly into the separator 2 or through the valved branch shown into line H, therein to be admixed with heated material from coil 8. In the event that this alternative procedure is followed, heated material from coil 8 may be passed through line 38, having pressure release valve l0 therein, rather than to pass through the ejector 36 where the suction effect created thereby is not needed or'desired. Steam supplied through line 21 may be introduced with the hydrocarbons either during their passage through coil 8, or following coil 8 either before or after pressure reduction The operation of the modification shown in Fig. 3 will be in part understood from the description given in connection with Fig. 1. However, Fig. 3 illustrates process and apparatus different in important particulars'from that illustrated in Fig. 1. Heated and partially vaporized materials may be supplied to the separator 2 through line H from any source, as, for example, in the manner described in connection with either Fig. 1 or 2. Overhead vapors may be withdrawn through line l2, further heated at Ila or not, asmay be desired, and then passed through line l4 to any one or more of the converters 3, also in the manner shown and described in connection with Fig. 1. Outgoing products from the converters 3 pass through the line i5 into rectifying tower 5 at some intermediate level along the height thereof and low boiling material such as gasoline and gases may be withdrawn as overhead through line l6, cooled or condensed in i1 and passed to storage or further treating apparatus as desired.

Any desired fraction may be passed through line 39, being withdrawn from fractionator 5 through any of branched lines 39a, 391) or 390, as desired, and forced by the pump shown through the converter 40, which is preferably of the pyrolytic type, and from which the products pass into element 4|, the latter optionally being operated as a reaction chamber to allow the cracking or viscosity breaking to proceed further, as a flash evaporator, or as a coking vessel. When it is operated, for-example, as a flash evaporator or a reaction chamber, any heavy materials which remain as liquid may be withdrawn from chamber 4| through line 42 and vapors may pass from the chamber through line 43 and either be sent through branch 44 into partial condenser '45 (which latter may be used to transfer heat from the vapors to incoming starting material to the system as passing to coil 8 of the furnace I (Figs. 1 and .2), or for any other suitable purpose) or a portion or all of the vapors may be sent through valved branch line 46 and be introduced into rectifying tower 5 at any suitable level, passing through lines 46a, 46!; or 460 as desired. However, at least a part of the vapors from chamber 4| usually pass into partial condenser 45 wherein heavier portions of such vapors are condensed and passed downwardly through line 41 into steam stripper 48. Overhead from steam stripper 4! may pass through line 49 and be combined with vapors leaving the partial condenser 45 and passed together through line 50 to tower 5. When the material passing through line 50 is to be used as refiuxin tower 5. any desired cooling may be effected in heat exchanger 5lz also separation of any wild gases (which may be present) from liquids may be effected, if desired, in any suitable liquid-gas separator located in circuit between exchanger or cooler 5| and the point of introduction of reflux into the top of fractionator 5. However, where desired, material passing through line 50 may be introduced into. tower 5 at some lower level without affecting any cooling in heat exchanger 5|.

Unvaporized or liquid material passing from steam stripper 48 through line 52 may either go through line 53 and be sprayed or otherwise introduced into separator 2 separately or in admixture with materials introduced through line H,

or may be partially returned through line 54.to be recycled through the still or pyrolytic converter 40 or part or all of such liquid may pass through the valved branch 55 into line II to be sent, either alone or in admixture with other liquid withdrawn from the tower 5, as reflux at or near the upper end of the separator 2. Also, any desired portion of the liquid withdrawn from stripper 8 may leave the system through valved line 45.

Where vapors leaving chamber 4| pass through so that fluid passing through line 50 is composed substantially completely of components such as gasoline and/or naphtha together with some hydrocarbons in the gas oil boiling range, thereby providing a blend of pyrolytically and catalytically produced lower boiling components of gasoline in tower 5. The-amount of material fed from tower 5 through the still or pyrolytic converter 40 may be controlled in relation to the amount of material fed through line l4 into catalytic converters 3 so as to maintain the characteristics and anti-knock rating of low boiling hydrocarbons withdrawn from tower 5 through line H; within desired limits.

Though not shown in the drawings, it is within the scope of my invention to send a fraction composed of insufliciently converted hydrocarbons, e. g. a gas oil fraction, from fractionator 5 into line 6 (Figs. 1 and 2) to be forced by pump 1 through coil 8. However, the ratio of such returned fraction to original'starting' material will overhead fromseparator 30 (Fig. 2) and introducing some or all of the same into line 6.

While the invention contemplates the treatment of a broad class or materials as above indicated, the treatment of a previously unconverted or virgin stock is especially contemplated. That is, this invention has particular application where the material charged through line 5 to coil 8 of the heater I consists wholly or predominantly of a material which has not previously been subjected to cracking or decomposition. While the catalytic conversion step performs to best advantage on a previously untreated or virgin'stock, the from the products of a previous catalytic o pyrolytic conversion which may be introduced into separator 2 as reflu'x is small in proportion to the whole charge passing to the converters 3. That is, the ratio of the reflux to separator 2 to the charge for the converters withdrawn through line I2 is ordinarily less than 1 to 10, i. e. less than 10%, and irequently is only of the order of 5% by weight of the vapors passing from the separator through line 12. Where the present process is being used in the production of a volatile gasoline, such as aviation gasoline having a 300 F. end point, and apparatus such as shown in Fig. l, modified or not as indicated by Fig. 3, is employed, one advantageous procedure is-to recycle a heavy naphtha having an initial boiling point above 300" F. from column 5 as reflux to separator 2.

It is-to be understood that the apparatus shown in the left-hand portion of Fig. 1 and in Fig. 2 of the drawings may be used in preparing charge for other types of conversion apparatus than those shown in Fig. 1 and Fig. 3. Also. the conversion apparatus illustrated in the right-hand portion of Fig. 1 and in Fig. 3 may receive charge prepared by apparatus other than the types illustrated in Figs. 1 and 2 01' the appended drawings. However, the apparatus ii lustrated is preferred.

Illustrations and examples given hereinabove are for the purpose of facilitating a quick unscope of the appended claims are contemplated. v

amount of material derived What we claim is:

1. In the production of desired low boiling hydrocarbons from a composite hydrocarbon starting material of wide boiling range containing a substantial proportion of heavy or unvaporizable components, the steps of process which comprise heating said starting material under conditions so as to retard active cracking while effecting vaporization of a large proportion of said starting material, passing the heated and partially vaporized material into a separating zone maintained at a pressure below that under which said heating is effected and therein separating liquids from vapors, withdrawing unvaporized material from said separating zone, withdrawing vapors from said zone. and effecting ing of higher boiling to lower boiling hydroca bons, passing fluid hydrocarbon products from said conversion zone to a fractionating zone wherein desired low boiling-products are sepa rated from higher boiling hydrocarbons, withdrawing a fraction ofhigher boiling hydrocarbons from said fractionating zone and subjecting it to a step of pyrolytic conversion so as to produce lower boiling hydrocarbons therefrom, separating the products from said pyrolytic conversion step into lower andhigher boiling fraca superheating ofthe same and controlling the temperature thereof, continuously passing the resulting superheated vapors to a conversion zone containing a solid adsorptive incombustible catalytic material and maintained under conditions so as to efiect a cracking of higher boiling to lower boiling hydrocarbons, passing hydrocarbon products f'rom said conversion zone to a fractionating zone wherein desired low boiling products are withdrawn as vapors, withdrawing a higher boiling liquid fraction from said fractionating zone, subjecting it to a pyrolytic conversion, passing those portions of the products of the pyrolytic conversion which boil below approximately 500 F. into the aforesaid fractionating zone, and withdrawing therefrom a small portion of liquid having an initial boiling point higher than the end point of said desired low;

boiling products and sending it to the top of the separator in order to control the boiling range of vapors passing to the catalytic conversion 2. In the production of desired low boiling hydrocarbons from a composite hydrocarbon starting material of wide boiling range containing a substantial proportion of heavy or unvaporizable components, the steps of process which comprise heating said starting material under conditions so as-to retard active cracking while efl'ecting vaporization of a large proportion of said starting material, passing the heated and partially vaporized material into a separating zone maintained at a pressure below that under which said heating is eifected and therein separating liquids from vapors, withdrawing unvaporized material from said separating zone,

withdrawing vapors from said zone and eflecting a superheating of the same, passing a stream of the resulting superheated vapors into and through a conversion zone containing an active, adsorptive siiicious catalytic material and maintained under-conditions so as to eflect a cracking it as reflux at a point adlacent the tions, sending the lower boiling fraction into the said fractionating zone, and passing a portion of the higher boiling fraction having an initial boiling point higher than the end point of said desired low boiling products 'to the top of the separator in order to control the boiling range of vapors passing therefrom to thecatalytic conversion zone. Y

3. In the production of desired low boiling hydrocarbons from a composite hydrocarbon starting material of wide boiling range containing a substantial proportion of heavy or unvaporized components, the steps of process which comprise passing said starting material through a heating zone under a substantial superatmospheric pressure but under such conditions as to prevent the production of large amounts of gasoline, thereby to partially vaporize said material,

substantially reducing the pressure 'of material leaving said heating zone and introducing it into a separating zone, withdrawing a stream of liquid from said separating zone, passing said stream of liquid from said separating zone to a flashing chamber, introducing a vaporizing medium into said flashing chamber, withdrawing separate streams of liquids and vapors from said flashing chamber, then passing the resulting vapor stream into the separating zone and into admixture with heated and partially vaporized,

drocarbon products from the cracking zone to a gasoline fractionating zone, withdrawing said from the fractionating zone as vapors and withdrawing irom ,the fractionating zone a liquid fraction having an initial boiling point greater than the end point of the gasoline and introductop of boiling vapors passing therefrom to the crack- THOMAS B. PRICKETT. GEORGE s, DUNHAM.

the separator in order to control the range of ing zone.

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