US2880160A - Process for conversion of heavy hydrocarbon oils - Google Patents

Description

March 31, 1959 w. F. AREYJR., ETAL 2,880,160

PROCESS FOR CONVERSION 0F HEAVY HYDROCARBON OILS Filed Aug. 17, 1953 HorSauusIzv ATTRNEY March 3l, 1959 w F AREY, JR, Erm. 2,880,160

PRocEss Foa CONVERSION oF HEAVY HYDRbcARBoN 0111s Fxiled Aug. 17, 1953 2 sheets-sheet 2 l Products l Hot 3021223 Brom Burner Fluidii@ Gas NVENTRS QUZ'ZZz'a'm @@1251 y?? aud @Obert it BY ATTORNEY United See-s Parent Of 2,880,160 Patented Mar.. 31, 1959 PROCESS FOR CONVERSION OF HEAVY HYDROCARBON OILS William F. Arey, Jr., and Robert J. Fritz, Baton Rouge,

La., assignors to Esso Research'and EngineeringCompany, a corporation of Delaware Application August 17, 1953, Serial No. 374,598

s claims. (Cl. s-s4) The present invention relates'to an improved process 15 More par-J for conversion of heavy hydrocarbon oils. ticularly, the invention relates to a process for obtaining from heavy residual oils products, particularly gas oil, of high quality and low contaminant content by a thermal non-catalytic conversion process. In another aspect, the 20 invention relates to a multiple phase iuidized solids coking system which is thermal and non-catalytic for producing high quality catalytic cracking feed stock from motor fuel boiling range are produced but these are of relatively low octane number. The most desirable product, and the one usually most sought in coking or other thermal processes applied to heavy residua, is a middle distillate such as a gas oil which can be largely converted by modern eltcient catalytic cracking processes to motor 40 fuels of high quality.

Unfortunately, many heavy residua contain relativelyV large proportions of undesirable materials which tend normally tobe carried over into the heavy ends of the gas oil fraction. These materials include certain nickel and vanadium compounds, apparently of organic nature, which are potent poisons to the usual cracking catalysts. They include also certain materials which promote high Conradson carbon in the gas oil products, which is undesirable. Various attempts have been made inthe past to keep these objectionable materials in the residue, to deposit them upon solid carriers such as coke produced in the conversion process, to catch them in guard beds of solids, to destroy them by burning, etc., without great success. At least some of the catalyst contaminants,

for example, appearv to volatilize with the gas oil, and

to remain in this fraction upon subsequent fractionation. Even when present in the gas oil in only small concentrations, they are highly objectionable. Besides injuring or inactivating the catalyst in subsequent cracking, they tend to promote a high production of gas, especially hydrogen, in all conversion operations where they are present. Frequently they are potent dehydrogenation catalysts, therebyprom'oting both high gas production and high degradation of the feed to coke and coke precursors in catalytic conversions. They tend to accumulate in the heavier ends of conventional gas oils.

In the production of a 430 to 1050 F. gas oil from reduced crudes by thermal non-catalytic conversion or coking it is found to be extremely difcult to obtain a sharp cut-oit or end point in the boiling range. It is 7o quite impossible in commercial scale fractionation to avoid inclusion of some small amounts of materials which, per se, have a boiling range upto 1100 F. or higher. These higher boiling components appear to 1nclude a `relatively high proportion of the objectionable contaminant materials mentioned above. If the fractionation temperature range is lowered so as to avoid completely the carrying over of` minor quantities of constituents of boiling range above 1050 F., including the objectionable contaminants, it must be brought down toaround 900 F. or so. This results in greatly reduced production of gas oil. The use of steam or other distillation or stripping aids greatly aggravates the carry over of the objectionable metallic (or metallo-organic) components and the asphaltenes or coke precursors which l,

The con- 30 Table I Eqnlval- Wt. per Contaminants,

ent Cut cent on PTB l Type of Dlstlllatlon Point ol 430 F Gas Oll,

F. N10 V105 1,010 43 Trace 0.06 1, 050 47 0.1 0. 6 1, 075 53 0. 1 l. 0 l, 71 0. l, 2. 4

1 Pounds per 1,000 barrels.

It will be noted that the metallic content increases very rapidly in the heavier ends. Obviously, it is desirable yto exclude, as far,v as practicable, the metallic constituents in the gas oil which goes to the catalytic cracker. It is desirable to do this without substantially reducing the volume of gas oil obtained from the residuum. The present invention affords a practical process and system for accomplishing this. This is achieved, in the present case, by coking the residual feed in a plurality of iluidized bed treatments at carefully selected and con# trolled conditions.

In conventional thermalcoking, using the iluid solids technique, a mass of particulate solids, such as coke particles of -the range of about 40 to 400 microns average diameter, is preheated to a temperature usually between about 1l00 and 1400 F., or more, and then brought to a reaction or coking zone. Here the hot coke particles are contacted by the feed.which is usually preheated though usually not substantially precracked or converted.

The reaction or coking temperature range in conventional systems is commonly about 950 to 1100 or 1l50 F. The residual oil feed is vaporized and cracked by the sensible heat of the particles. The cracked and vaporized products then pass on to a fractionationstage where various products such as gas, gasoline, gas oil and a iinal residue are obtained. Apparently, as noted above, the objectionable metallic contaminants and the ventional coking conditions of temperature, feed rate,

etc., so that the obiectionable constituents mentioned may be intentionally volatilized and carried over. The heavy residual oil feed is introduced into a uidized bed of hot particulate solids at the rate of about l pound per to SOpoundsof solids per unit of time. The coking products are then passed directly from the rstbed into and through a second iluidized solids bed stage which is operated, for coking or conversion ata controlled oil production. The overall quality of the gas oil as re-y gards contaminants is very definitely improved. The lighter gas oil components pass through the bed quickly and are not substantially aiected by it while the heavier components are partly condensed.

In effect, the less desirable heavy components of the gas oil stay in a, coking reaction zone longer, though at lower temperature for the latter vpart of their stay,'t han in prior processes. As a result they are converted to a substantial degree to more volatile components, including lighter gas oil, and are separated quite effectively from their metallic constituents. 'Organic radicals associated with the metallic constituents appear to be cracked or otherwise converted, so that`the metallic constituents tend to revert to inorganic ash and to remain with the solids of the bed. .The coke promoters such as asphall tenes and` other constituents responsible for high Conradson carbon in the usual gas oil products from coking likewise appear to be reduced in quantity.

Whatever the actual mechanism may be, itappears that the tempering and prolonging of reaction in the cooler bed is highly beneficial. Moreover, it appears that the prompt quenching of the products from the first bed, either before or while they pass through the subi sequent cooler bed or beds, is highly beneficial. A series of three or more beds may be used, if desired, but ordinarily two are suliicient with the latteroperating at a temperature of 50 to 300 F. or more, preferably 100 to 200 F., below that of the first bed.

It is recognized that the prior art has suggested the use of plural iuidized solids beds in sequential arrangement for various purposes. For example, in Jahnig patent, No. 2,420,542, flue gases from a regenerator are passed through a cooling bed of uidized solids. The present invention, however, is applied to the much different problem of coking heavy or residual oils and it -helps to solve the serious problem of carrying over cracking catalyst contaminants in the gas oil.

A preferred temperature range for the second bed is between about 750 and 950 F., particularly between '800 and 900 F. as compared with about 950`to l100 F. for the first bed. The products from the first bed are preferably cooled in the second bed itself, although some cooling which may take place as they travel from the first bed to the second is also contemplated in the invention. Two separate modifications are shown in the `drawings which are attached.A It will be understood that these are exemplary only.

Referring now to the drawing, Fig. 1 shows in diagrammatical elevation one form of a' system or process for convening heavy oils, such as crude residua wherein products from the first fluidized solids bed are passed through a second and cooler bed. Here they are cooled and further processed. The second bed itself is cooled by extraneous means, such as a cooling coil inserted therein. Fig. 2 shows a modification wherein the solids from a first bed are cooled by heat exchange before arrangement where solids from the second bed are circulated through a heat exchanger.

Referring now in detail to the drawings, in Fig. l a reactor vessel 11 of suitable type and construction is shown in which a lower or first bed 13 of iiuidized solids may be supported and maintained. A stream of preheated solids such as coke particles from a burner (not shown) is brought into the first bed at a temperature in the general range of about 1100 to 1400 F. The incoming stream of solid particles is fed into the bed 13 through a line 15. Suitable fluidizing gas such as steam may be supplied through one or more lines 17 and the oil feed, preferably preheated, may be fed in through one or more noules 19 and sprayed into the beds. The vaporized oil cooperates with the steam to uidize the bed 13.

A substantial part of the solids in bed 13 pass upwardly by elutriation into the bed 16 above a partition or grid 31before they return and enter a stripping zone 21 defined. by a partition 23 as described below. A stripping gas may be supplied to this zone 21 through one or more lines 25, as is well known in the art. From bed 13, the spent solids may be drawn off through a standpipe 27 under control of a valve 29 or equivalent. From here they are returned' to a heater or burner, not shown, for reheating, though some of them may be withdrawn as product coke.

The upowing velocity of the steam and/or other uidizing gas within bed'13 is sufficiently high that at least some of the solid particles are constantly entrained upwardly Iout of bed.13 and through a perforate partition or vgrid 31 which extends transversely across the vessel 11. The gasiform stream, comprising the original uidizing medium plus products of the coking operation in the lower bed carries the particles entrained from the lower bed up through the perforations and forms a second uidized solids bed 33 upon the partition 31.

Bed 33 is cooled to a temperature of the lower range described above, i.e. 750 to 950 F., preferably 800 to 900 F. This is accomplished in Fig. l by inserting a cooling .coil 35 in the bed and circulating a coolant n through/the coil. Heat exchange between a yfluidized passing into the second bed. Fig. 3 shows still another 79 solids bed and a coil immersed therein is very eflcient. An overflow conduit 37 controls the depth of the bed 33 and extends belowthe transverse perforate partition ,31 and below the surface of bed 13, so as to seal against countercurrent gas ow from the lower bed. Fluidized solids in bed 33 flow down through conduit 37 and the lower bed overflows a partition 20 which defines the stripping zone 21 as previously mentioned.

Through the upper bed, the gaseous and vaporous products which boil below its temperature pass rapidly upward and out through a gas-solids separator such as cyclone 41 which is of conventional type with a dipleg 43 which returns solid particles, separated from entrainment in the products, to bed 33. The heavier vapors are condensed and remain for a relatively long time in bed 33.

\ Eventually they are largely converted and the hydrocarbon products, now relatively free from contaminants, pass through cyclone 41 and out through line 45 to suit able recovery equipment, not shown.

Fig. 2 shows a somewhat different arrangement wherein a vessel 51 is adapted to support a lwer lluidized bed 53 and an upper uidized bed 55. The particular means for uidizing the lower bed are not part of the invention and may be of any known type. Hot solid particles are brought into the bed from a suitable preheater or burner, not shown, through a line 57. The oil feed, suitably preheated by means not shown, is brought in through any suitable means, preferably comprising a plurality of noz zles 59, being distributed so as not to cause bogging or serious agglomeration in the bed.

Coking and thermal cracking as well as vaporization takes pla?? in bed 53, the cracked and volatilized products passing upwardly through a perforate partition 61. In this case, however, as distinguished from Fig. 1, although some small quantity of solid particles will be carriedv up through the perforations in 61, the major proportion of solids is first taken downwardly from a stripping zone 63, defined by a partition 65, the upper edge of which forms an overfiow wier. pass down through the stripping zone 63, counter-current to a suitable upfiowing stripping gas, supplied from any suitable source. From here they, or a suitable portion of them, pass through a standpipe 65, control valve 67, and U-bend 69, into a heat excehanger 71. Here they are cooled to the desired temperature, and then passed on up into the second bed 55 through a line 73. Suitable aerating and fiuidizing gases may be introduced at suitable points to cause the solids to flow as described. The heat exchanger may be utilized to help preheat spent solids from the upper bed, to produce steam, etc.

The solids in the upper bed 55 iiow over the upper inlet end of a conduit 75 which extends down through the partition or grid 61 into the lower bed 53. A branch line 76 is provided to take the cooled solids out of the second bed 55 and return them to the burner. This line also branches into a third line 77 through which the solids from the second bed can be returned directly to heat exchanger 71. This latter arrangement reduces the load on heat exchanger 71 somewhat and results in higher thermal efiiciency. Appropriate valves 78, 79 and 80 are provided for control. The spent solids which are returned to bed 53 down through stripper 63 and into line 69 or to line 81 and valve 82 back to a heater or burner, or part of the product coke may be withdrawn as such and only part burned and reheated.

The products from the second and cooler coking bed pass overhead through cyclone 83 which returns the separatorv solids to the bed through a dipleg 84. The solids-free gases and vapors then pass on through a line 85 to fractionation and other recovery equipment.

In Fig. 3 still another arrangement is shown wherein cooling of the solids in the second bed is accomplished by circulating them from the second bed through a heat exchanger and back to the same bed. A reactor vessel 101 contains a lower tiuidized bed 103 to which hot solids, preferably coke particles, are fed from a heater .or burner through a line 105. Fuidizing gas, usually steam, thoughl gaseous hydrocarbons or hydrogen or nitrogen may be used, is introduced through one or more inlets 107. Three are shown. Bed 103 reaches a level where it overows a partition 109, which defines a stripping zone 111. A stripping gas such as steam is introduced through a line 113 to strip occluded gases from the descending solids which pass out through line 115 to a burner or to a product coke receiver.

Fluidizing is sufficiently active that some coke particles are carried up with the product vapors through a perforate partition or grid 117 on which a second uidized bed 119 is formed. This bed reaches a level` predetermined in part by a partition 121 over which part of the coke may flow to return to the lower bed. Partition 121 extends into the lower bed so as to prevent products from the lower bed from by-passing the upper bed.

In addition to the partition 121, a conduit 123 leads out of vessel 101 at approximately the same level, or slightly lower, so that a substantial stream of the uidized solids may ow through a heat exchanger 125. This exchanger is cooled by any suitable means, c g. it may be used to generate steam for the coking and associated operations. The cooled solids, after passing through heat exchanger 125, are returned to bed 119 through a line 127, with the assistance of a ylifting or aerating gas introduced through one or more lines 129.

The overflowing solids By the means just described, the temperature of the second bed may be accurately controlled so as to control 'the separation of contaminants from the products. The

` hined in respect to the use of both a heat exchanger outside and a cooling coil inside the upper bed. Since the quantities of heat involved are quite large, such a combination may be needed for proper control in large units. Other changes and modifications such as will suggest themselves to those skilled in the art may also be made.

What is claimed is:

1. The process of converting residual hydrocarbon oil of relatively high metallic cracking catalyst contaminant content to gas oils of relatively low content of said contaminants which comprises feeding a stream of solid coke particles within the 40 to 400 micron average diameter range, preheated to la temperature of at least 1100 F., into a conversion zone at a controlled rate. passing a gasiform stream upwardly through said solids at a rate sutiicient to cause said solids to form a uidized solids bed overhead, feeding said oil into said bed at a rate of ,1,5 to Lug the rate, on a weight basis per unit of, time, of said controlled rate of feeding solids, contacting said oil with said solids in said bed at a temperature of about 950 to 1150". F. for a sufficient time to convert a substantial proportion of the oil to gas oil vapors, removing coke particles from said first bed and forming a substantially cooler second fluidized bed of said solids superposed above said first-mentioned iiuidized solids bed in said conversion zone and supported on a perforated partition, and contacting said vapors with said second bed at a temperature of about 750 to 950 F. for a sufficient time to condense and to substantially further convert a portion thereof to give additional desirable oil vapors, thereby removing some of said metallic con` stituents.

2. Process according to claim 1 wherein the second bed is cooled 50 to 300 F. below the temperature of the first bed.

3. Process according to claim 1 wherein the second bed is cooled by means of a cooling coil inserted therein.

4. Process according to claim 1 wherein coke particles are recirculated from the second bed through a heat exchanger to cool said second bed.

5. Process as in claim l wherein coke solids from the first bed are withdrawn from the first bed, cooled by heat excange, and reintroduced to form said second bed.

References Cited in the file of this patent UNITED STATES PATENTS 2,436,160 Blanding Feb. 17, 1948 2,474,583 Lewis J'une 28` 1949 2,557,680 Odell June 19, 1951 2,692,888 Throckmorton et al Oct. 26, 1954 2,702,267 Keith Feb. l5, 1955 2,731,395 Iahnig et al. Jan. 17, 1956 2,737,475 Voorhies Mar. 6, 1956 OTHER REFERENCES Wrightson: Analytical Chem., vol. 21, No. 12, December 1949, pages 1543 to 1545.

Woodle:4 Ind. and Eng. Chem., vol. 44, No. '11, November 1952, pages 2591 to 2596.

Claims (1)

1. THE PROCESS OF CONVERTING RESIDUAL HYDROCARBON OIL OF RELATIVELY HIGH METALLIC CRACKING CATALYST CONTAMINANT CONTENT TO GAS OILS OF RELATIVELY LOW CONTENT OF SAID CONTAMINANTS WHICH COMPRISES FEEDING A STREAM OF SOLID COKE PARTICLES WITHIN THE 40 TO 400 MICRON AVERAGE DIAMETER RANGE, PREHEATED TO A TEMPERATURE OF AT LEAST 1100*F., INTO A CONVERSION ZONE AT A CONTROLLED RATE, PASSING A GASIFORM STREAM UPWARDLY THROUGH SAID SOLIDS AT A RATE SUFFICIENT TO CAUSE SAID SOLIDS TO FORM A FLUIDIZED SOLIDS BED OVERHEAD, FEEDING SAID OIL INTO SAID BED AT A RATE OF 1/5 TO 1/50 THE RATE, ON A WEIGHT BASIS PER UNIT OF TIME, OF SAID CONTROLLED RATE OF FEEDING SOLIDS, CONTACTING SAID OIL WITH SAID SOLIDS IN SAID BED AT A TEMPERATURE OF ABOUT 950* TO 1150* F. FOR A SUFFICIENT TIME TO CONVERT A SUBSTANTIAL PROPORTION OF THE OIL TO GAS OIL VAPORS, REMOVING COKE PARTICLES FROM SAID FIRST BED AND FORMING A SUBSTANTIALLY COOLER SECOND FLUIDIZED BED OF SAID SOLIDS SUPERPOSED ABOVE SAID FIRST-MENTIONED FLUIDIZED SOLIDS BED IN SAID CONVERSION ZONE AND SUPPORTED ON A PERFORATED PARTITION, AND CONTACTING SAID VAPORS WITH SAID SECOND BED AT A TEMPERATURE OF ABOUT 750* TO 950*F. FOR A SUFFICIENT TIME TO CONDENSE AND TO SUBSTANTIALLY FURTHER CONVERT A PORTION THEREOF TO GIVE ADDITIONAL DESIRABLE OIL VAPORS, THEREBY REMOVING SOME OF SAID METALLIC CONSTITUENTS.

Images