US2587703A - Cracking heavy oils in presence of oxygen - Google Patents

Description

March 4, 1952 R. M. DEANESLY CRACKING HEAVY ons 1N PRESENCE 0E OXYGEN Filed Feb. 18, 1948 yer v IN VEN TOR. C/zardAiZea/zesly Patented Mar. 4, 1952 UNIT-ED STATES PATENT OFFICE .asoma :eRAoKmGHEAvY oILsfINfPREsENcE -oF `QXYGEN Richard 1M- Deanasly, Hinsdale. 1.1.13, assigner to niversal'iOikProducts Cornpan, acorporationaofeelawalje AnrlieaiianzI-*ehrnary 18, 194A;Serial-Noires;

This invention relates to an imprOVed method and means for effecting the autothermic cracking of relatively heavy oils, gas oils or heavier, Vin

order to produce lower molecular weight hydrocarbons such as olens, diolens, aromatics `and Athe like.

The high temperature vapor phase cracking of heavy hydrocarbonoils has been arather dinicultpprocedure because of the lfact that a tariog is formed which contains more or less solid particles of carbon. Thus, when the fog settlesand adheres to equipment beyond the zone of formation, that portion of the crackingapparatus and the separating equipment V generally becomes plugged with a coke formation. When thecracking is effected by mixing air or oxygenwith thev preheated oil stream to obtain the desired cracking temperatures by internal oxidation, the process has been given the general name of r,autothermic cracking.

It is the principal object of the present invention to provide an operation which eiects anefcient conversion of heavy oilsto desirable lower boiling and lower molecular weight products `comprising particularly olens, Adierles and arovaemmis. (ciales-65) V,oil Vstream and dispersing it in admixture with air. `or a .stream containing free oxygen, into a relativelysmall confined reaction zone, eiecting theautothermic cracking of the oil stream under substantially adiabatic and short residence time conditions, passing the resulting 4products of ,lower molecular Weight Yhydrocarbon gases and vapors, coke, and tarfog from the reaction zone to theloyvery portion of a fludized bedof cokelike particlesmaintained in direct andopen com- `munication*..With the outlet of the reaction zone, passing,the product stream upwardly thrQilgh the iiudzed bed of particles and effecting simultaneously the completion of the thermalconvyer- 1sion andthe trapping of the tarv fog, continuously y discharging a ,substantially clear productystream froni theilnner portion of ih e parile/bedand continuously withdrawing excess coke-like particles from thefluidized bed, lthe excess being :provided by the progressive cracking of the tar "fog lprodufcd in the cracking operation.

Ina more specific embodiment of the operation, Athe operating pressure within the reaction zone uis maintained relatively low, preferably b e- 25 low v3patrnospheres, while the cracking temperlaturepmayvary from 1200 to 1700 FQdepending :upon theprinciparl products sought and/or `economically iavorable from the standpoint of the ,Qhlgng Stock employed. Preferably, the k air .streamas .well ,as the oil stream, is preheated and .mixed therewithin controlled proportions to efgiecttheoxidationof a part of the hydrocarbon v Ystream in an exothermic reaction and to provide cent to and in communication ,with the cracking zone. `The particle bed provides a zoneefor completing the autothermic reactionywhile the tar fQg, resulting from Vthe cracking operation, his trapped on the particles an-dis crackednprogres- Vsively to increase'the volume ofgcoke present, the

surplus of which may be drawn 01T f romAv the uidized bed. Thus, the resulting vaporousfproduct stream vmay be discharged vfrom thezupperpcrtion of the'uidizedparticle `zonefin'a substantially clear form and pass to conventional Vfractionation and recovery apparatus, with little Lor --no trouble arising-from coking in therecovery equipment.

Broadly, the improved method of autothermic conversion of a heavyoilrstream as provided 'by 'this invention, comprises, preheating theghavy;

the ,desired temperature necessary to Veffect an eicientendothermic cracking reaction ofthe remainder of the hydrocarbon stream that accomvpanics, inthe conversion Zone, thehot oxidation products of theeXOthermicreaCtiOn. As may be deemed desirable, steam or other diluent gas may ,be mixed with vthe reactant streams to minimize c Ithe carbon formation Within the conversion Zone.

Y1n an alternate, and very vdesirable specific 0peratOIL the uidized particle ybed may be A.em-

ployedasa quenching zone toeiect a rapid cooll'ing of the. cracked product stream and thus pre- ,vent polymerization and sidereactionsfromtaking, place whilesimultaneously trapping thetar Jog which is produced. In this embodiment the liuidized;particles are circulated througha `coolingkzone'which may be built integral with or separate from the main vessel as, convenient.

The fluidized particle bed may comprise coke- Vlikeparticles built up from the coke and vtar fog,

.as fnoted, hereinabove.. howeverI a iinely divided refractory type of particlemay be used to collect chamber 2.

fluidized bed, to aid in the production of the lower molecular weight products and serve as a material to absorb and collect the carbonaceous material.

The high temperature cracking in the reaction zone is carried out in a manner to have only a short residence time under substantially adiabatic conditions, thus, a small, elongated, and

refractory lined temperature resistant reaction Provision is also made at the lower end of the apparatus for admitting steam through line I4, having valve l5, so that when desired, a small quantity of steam may be mixed with the reactant stream to provide a diluent and to provide further control over the primary conversion. Still another line I6, having valve Il is provided to connect with line 5, and as indicated may be used to charge a fuel gas to the unit, to provide heat for starting up the unit, or alternatively, to provide. additional heating fuel for oxidation Within the conversion zone where alternative reaction conditions are deemed desirable.

In'aI preferred `operation of the unit, the reactant stream isfcharged continuously to the lower end of the chamber I and reaction products areA continuously discharged after relatively short chamber is preferably provided for the -cracking portion of the unit. Suitable external insulation around the reaction chamber is provided to prevent loss of heat therefrom and to insure an operation which is as closely .adiabatic as possible.

It is a particular feature of the improved design of the apparatus of this invention to have the particle bed chamber or quenching chamber connect directly with the outlet end of the reaction chamber so that the reaction products may be discharged rapidly into the fluidized bed.

The accompanying drawing serves to illustrate,Y

varying forms of the improved conversion apparatus for the autothermic cracking of heavy oils, and the following description thereof will serve also to explain more fully the conversion and contacting operation of this invention.

Figure l of the drawing is an elevational view, shown diagrammatically, of one form of apparatus for carrying out the improved autothermic cracking operation of heavy oils.

Figure 2 of the drawing, shows an alternatev construction of the lower end of the conversion apparatus, at the zone where the reaction chamber connects with the uidized bed chamber.

Referring now to Figure 1 of the drawing, there is shown a small vertically positioned reac. tion chamber I which is below and connects with a larger verticallyl positioned fluidized particle The interior of; the chamber I is provided with a heat resistant refractory 3comprising an insulating cement, or a ceramic type of material, suitable for withstanding temperatures of the order of 2000 F., or higher, depending upon the particular cracking range which may be desired. The lower end of the chamber ,'I has an inlet nozzle 4, adapted to receive a mixed reactant stream passing by way of line 5 to the `dispersion or atomizing nozzle 6. In this vembodiment, the nozzle is placed in the end of the cracking zone just inside of the inlet opening 4.

The'heavy oil feed stream to the unit is' charged through line 'l to a heat exchanger 8, and from the latter it is passed through line 9 and control valve I0, to the line 5. The charge stream is thus preheated, and preferably vaporized, by heat exchange with the product stream which is discharged from the upper end of the unit through' line II to the heat exchanger 8. Air, or oxygen, preheated or not as may be desired, is charged through line I2 and control valve I3 to line 5 and is mixed with the preheated oil stream, in ja controlled proper proportion with the latter, to

provide a mixed reactant stream which may be discharged through the nozzle 6 into the reaction chamber I to eiect the autothermic cracking of the heavy oil to produce the desired lower boiling hydrocarbon products( periods of contact and reaction time within the chamber, to the lower end of the upper chamber 2 which maintains therein afluidized bed of cokelike particles I8 as a contacting and tar fog collecting medium for the reaction chamber products. A relatively low superatmospheric pressure isV preferably maintained in the reaction zone, however, suflicient pressure is utilized to insure the passage of the reaction products upwardly through the bed I8 and to adequately fluidize it as the stream ows upwardly therethrough.

The reaction products comprising lower boiling hydrocarbon gases and vapors, coke and tar fog, pass continuously from the chamber I to the lower end of chamber 2; thus, in this improved operation, the coke and tar fog will be trapped and absorbed within the fluidized bed I8, while the gaseous products are permitted to undergo further adiabatic conversion to substantial completion, or alternately, may be quenched progressively as they pass upwardly through the bed to be discharged in a substantially clear and stable form at the top of chamber 2, and at a reduced temperature of the order of 600 to 800 F., so that further cracking and polymerization reactions are stopped. The tar fog which is produced and passedy from the reaction chamber I is cracked progressively to provide additional coke in the fluidized bed I8 so that a surplus may becontinuously withdrawn from the unit and discarded. In this drawing, the upper extremity of the uidized coke bed is indicated by the broken line I9, and an outlet line 20, lhaving a control valve 2l, provides means for withdrawing the excess coke from an intermediate point in the wall of the quenching chamber 2.

Figure 2 of the drawing, shows an alternate arrangement and method for connecting the reaction chamber with the quenching chamber. The reaction chamber 23 is placed angularly with respect to a vertically positioned quenching chamber 24, which in turn has a long tapering cone-like lower head 25. The lower portion of chamber 23 connects with the lower head 25,

, so that the reaction products from the chamber 23 thus flow downwardly into the head 25 and turn upwardly into the fluidized' quenching bed 26. The latter may comprise a fluidized bed of I "cracking conditions.

Atv the upper and inlet end of the reaction `chamber 23, the mixed reactant stream -is charged through line v28 and dispersion nozzle 129, withthe proper proportion 'of pre-heatedv oil to oxygen being controlled to effect the desired conversion reaction. Oil is charged to the' line 2,8, through line 30, having control valve 3 I, while the pre-heated air, or'other oxygen containing stream, is charged through linee32 and control valve 33. The third line 34, `having control valve 35, provides means for charging steam or other hot diluent gas to the unit in admixture with the air and oil stream, when such may be desired in carrying out the autothermic reaction.

A heating coil 42, placed within the chamber 24 and connecting with line 32 provides means for transmitting heat from the bed 2B to the air stream, While another coil 43, connecting with line 34, similarly transmits superheat to the steam stream which may be charged to the reactor 23.

An inlet 36, at the lower' end of the tapering head 25, provides means for charging a fuel gas and air to the unit to minimize combustion of the reactant stream, or alternately, to provide means for warming up and starting the unit. Fuel gas is conducted to the inlet 36 through line 31, valve 38 and line 39, while the additional air stream may be conducted through line 40 and valve 4| to the line 39 and inlet 36.

The autothermic cracking of heavy oils to provide lower mol weight olens and aromatics may be carried out in the apparatus embodiment of Figure 2 in substantially the same manner as that described in connection with Figure 1, the reaction products of the lighter hydrocarbon vapors and gases, coke and tar fog are passed t the lower portion of the uidzed bed chamber to fluidize the coke-like particles 26 maintained in the chamber, whereby the bed serves simultaneously to quench the product stream and substantially eliminate the tar fog therefrom.

This latter embodiment provides, however, for a slightly diierent and optional operating procedure, in that fuel gas and air may be charged independently to the lower end of the unit and provide combustion products into which the oil stream may be atomized. Thus, a lesser amount of the charge may be used for autothermic cracking within the reaction chamber 23, the necessary endothermic heat required being supplied from the extraneous fuel charged via line 31.

It is not intended to limit the process and apparatus of this invention to the exact construction and arrangements which have been shown in the drawing, for obviously, variations may be made in the positioning and arrangement of the different sections of the unit, and fall within the scope of this improved means for carrying out autothermic cracking of heavy oils. Particles separating means, such as the usual, well-known, centrifugal or electrical precipitator types of apparatus, may be used if desired in the upper part of the quenching chamber to effect the removal of solid particles from the gaseous product stream, prior to discharging it through line ll.

Also. it is not intended to limit the pre-heating of the air and the heavy oil charge streams to that which may be obtained in heat exchangers such as shown, for additional heaters or heat exchange means may be employed to bring the streams to a desirable charging temperature.

I claim as my invention:

1. In a process for the autothermic cracking yof a relatively heavy hydrocarbon oil stream to "produce lower boiling and lower molecular weight hydrocarbons, the improved method ci? operation which comprises, pre-heating said heavy oil stream and dispersing it continuously in admixture with a free-oxygen containing stream into a relativelysmall -conned reaction Zone, controlling the proportions or' oil and oxygen-containing 'streams in the mixture and effecting a substantially adiabatic autothermic cracking Yof said oil within said reaction zone at a temperature of i-rorn 1200 to 1700 F; while maintaining a relatively low superatmospheric pressure therein of less than 3 atmospheres, said adiabatic autothermic cracking being of a sufcient magnitude to form a product stream containing a substantial amount of tar fog and lower molecular weight hydrocarbon vapors, passing the products of oxidation and cracking in a continuous stream to a fluidized bed composed predominantly of coke-like particles being maintained contiguous with the outlet of said reaction zone, passing the product stream upwardly through said bed and therein trapping tar fog resulting from said cracking, while controlling the now of the vaporous products to provide iluidization of said coke-like particles Within said bed, continuously discharging a substantially clear stream of lower molecular weight hydrocarbon products from said uidized bed, effecting the continuous addition of coke-like particles to said bed by the continuous heating and progressive cracking of said tar fog trapped therein, and withdrawing a continuous stream of surplus particles whereby to maintain a substantially constant depth fluidized bed of particles.

2. In a process for the autothermc cracking of a relatively heavy hydrocarbon oil stream to produce lower boiling and lower molecular weight hydrocarbons, the improved method of operation which comprises, pre-heating said heavy oil stream and dispersing it continuously in admixture with a free-oxygen containing stream into a relatively small conned reaction zone, controlling the proportions of oil and oxygen-containing streams in the mixture and effecting a short contact time and substantially adiabatic autothermic cracking of said oil within said reaction zone at a temperature of from 1200 to 1700" F. while maintaining a relatively low superatmospheric pressure therein of less than 3 atmospheres, said adiabatic autothermic cracking being of a sufficient magnitude to form a product stream containing a substantial amount of tar fog and lower molecular weight hydrocarbon vapors, passing the products of oxidation and cracking in a continuous stream to a quenching zone, said quenching zone being maintained contiguous with the outlet of said reaction zone and having therein a fluidized bed composed predominantly of coke-like particles, passing the product stream upwardly through said bed and simultaneously quenching the vaporous products and trapping tar fog resulting from said cracking, while controlling the flow of said vaporous products to provide iiuidization of said coke-like particles within said quenching zone, continuously discharging a substantially clear stream of lower molecular weight hydrocarbon products from said quenching zone from above said fluidized bed at a temperature precluding further cracking, effecting the continuous addition of coke-like particles to said bed by the continuous heating and progressive cracking of said tar fog trapped therein, and withdrawing a continuous stream of surplus particles whereby to maintain 8 a substantially constant depth uidized bed of Number 'Y Name Date particles within said.` quenching zone. 2,303,047 Hemminger Nov. 24, 1942 RICHARD M. DEANESLY. 2,388,055 Hemminger Oct. 30, 1945 2,398,739 Greensfelder et a1. Apr,j 16, 1946 REFERENCES CITED 5 2,402,875 Cornell June 25, 1946 The following references are of record in the 420:542 y Jahmg M9151 13 1947 fue of this patent: 2,428,690 Tyson et 9.1 Oct. '7, 1947 2,436,486 Scheineman Feb. 24, 1948 UNITED STATES' PATENTS 2,443,210 Upham June 15, 194s Number Name Date 10 2,488,029 Scheneman Nov. v15, 1949 2,187,741 Houdry Jan. 23, 1940

Claims (1)

1. IN A PROCESS FOR THE AUTOTHERMIC CRACKING OF A RELATIVELY HEAVY HYDROCARBON OIL STREAM TO PRODUCE LOWER BOILING AND LOWER MOLECULAR WEIGHT HYDROCARBONS, THE IMPROVED MWTHOD OF OPERATION WHICH COMPRISES, PRE-HEATING SAID HEAVY OIL STREAM AND DISPERSING IT CONTINUOUSLY IN ADMIXTURE WITH A FREE-OXYGEN CONTAINING STREAM INTO A RELATIVELY SMALL CONFINED REACTION ZONE, CONTROLLING THE PROPORTIONS OF OIL AND OXYGEN-CONTAINING STREAMS IN THE MIXTURE AND EFFECTING A SUBSTANTIALLY ADIABATIC AUTOTHERMIC CRACKING OF SAID OIL WITHIN SAID REACTION ZONE AT A TEMPERATURE OF FROM 1200 TO 1700* F. WHILE MAINTAINING A RELATIVELY LOW SUPERATMOSPHERIC PRESSURE THEREIN OF LESS THAN 3 ATMOSPHERES, SAID ADIABATIC AUTOTHERMIC CRACKING BEING OF A SUFFICIENT MAGNITUDE TO FORM A PRODUCT STREAM CONTAINING A SUBSTANTIAL AMOUNT OF TAR FOG AND LOWER MOLECULAR WEIGHT HYDROCARBON VAPORS, PASSING THE PRODUCTS OF OXIDATION AND CRACKING IN A CONTINUOUS STREAM TO A FLUIDIZED BED COMPOSED PREDOMINANTLY OF COKE-LIKE PARTICLES BEING MAINTAINED CONTIGUOUS WITH THE OUTLET OF SAID REACTION ZONE, PASSING THE PRODUCT STREAM UPWARDLY THROUGH SAID BED AND THEREIN TRAPPING TAR FOG RESULTING FROM SAID CRACKING, WHILE CONTROLLING THE FLOW OF THE CAPOROUS PRODUCTS TO PROVIDE FLUIDIZATION OF SAID COKE-LIKE PARTICLES WITHIN SAID BED, CONTINUOUSLY DISCHARGING A SUBSTANTIALLY CLEAR STREAM OF LOWER MOLECULAR WEIGHT HYDROCARBON PRODUCTS FROM SAID FLUIDIZED BED, EFFECTING THE CONTINUOUS ADDITION OF COKE-LIKE PARTICLES TO SAID BED BY THE CONTINUOUS HEATING AND PROGRESSIVE CRACKING OF SAID TAR FOG TRAPPED THEREIN, AND WITHDRAWING A CONTINUOUS STREAM OF SURPLUS PARTICLE SWHEREBY TO MAINTAIN A SUBSTANTIALLY CONSTANT DEPTH FLUIDIZED BED OF PARTICLES.

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