CA1246481A - Coking residuum in the presence of hydrogen donor - Google Patents

Abstract

COKING RESIDUUM IN THE PRESENCE OF HYDROGEN DONOR

Abstract A process is disclosed wherein hydrogen-donating hydrocarbons are introduced into a non-catalysed delayed coking reaction together with coking feedstock, resulting in a decrease in coke production and an increase in the yield of liquid hydrocarbon products.

Description

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The present invention relates to a process for obtaining increased yields of liquid hydrocarbons from coking -feedstocks by introducing hydrogen-donating hydrocarbon material together with the feedstock. In known delayed coking processes a gas oil and/or residuum is heated rapidly to coking 5 temperature, initiating thermal breakdown, and passed into a coking drum, where the hot material continues thermal breakdown and conversion to lighter hydrocarbons and coke. Coke yields in such processes can be as large as 30%
or more, and the production of large amounts of this low-valued material is uneconomic.
Processes known in the art include the manufacture of premium coke, that is, coke having a low coefficient of thermal expansion (CTE), which is higher-valued than conventional coke.
For example, in U.S. Patent 4 176 046, McConaghy described a process in which vacuum residuum was hydrogen donor diluent cracked, the 15 cracking effluent was hydrodesulphurised and partially hydrogenated, and the bottoms were delay-coked. The coker gas oil, boiling from 316C to 480C, was recycled to be used as donor diluent. The predominantly aromatic nature of the bottoms fed to the coker accounted for the low CTE of the product coke.
An alternative approach was described by Kegler et al in U.S.
Patent 3 960 704, in which residuum was oxidised at a temperature from 260C to 316C and the resulting blown residuum was coked at 454C to 510C with or without a viscosity-reducing diluent, for example premium coker gas oil. The function oF the gas oil was strictly to reduce the viscosity . .
25 of the feedstock, which was said to render the coke product easier to handle than coke made without diluent blended with the feedstock.
The patent of Sooter, U.S. Patent 4 385 980, described the coking of pulvèrised coal with a hydrogen donor, fractionating the overhead products 46~1 of the coking reaction and partially hydrogenating a "heavy recycle gas oiL" fraction of use as donor in the coker. The operating temperature of the coker was said to be in the range 450C to 550C. No disclosure of the usa o~ donor diluent with other than pulverised coal was given.

In U.S. Patent 4 213 846, Sooter et al showed the reduction of the CTE of delayed coke by feeding recycled severely hydrotreated gas oil and highly aromatic premium coker feedstock comprising up to 50 per cent residuum in a delayed coker. The gas oil stream was obtained from the coker liquids, and the coker was operated at a transfer line temperature of 505C to 525C
instead of a normal (i.e. non-donor) temperature of 470C to 505C. It was stated at column 2, lines 48-50 that there would have been no reason to carry out recycle hydrotreating if regular, as opposed to premium, coke was being reduced. The hydrotreating conditions were sufficiently severe that the recycle stream was fu~l~, rather than partialLy hydrogenated. No comrnent was made concerning coke yield.

Wilson et al, in U.S. Patent 3 617 5L3, disclosed a process for converting coal into liquid hydrocarbon products. Coal ~as slurried with a hydrogen donor solvent boiling in the range from 177C to 4~2C, li~uefied and the bottoms, containing liquid liquefaction products, non-liquefied solid coal particles and unconsumed hydrogen-donor solvent was passed to a fluid coking zone. No temperature range of operation of the fluid coking zone was disclosed, but the examples of the process were each operated at 538 C. Delayed coking was suggested as an alternative to fLuid coking, but no operating conditions were disclosed.

In U.S. Patent 2 953 513, Langer disclosed the upgrading of petroleum residua by contact with hydrogen-donating hydrocarbons boiling in a temperature range from 371 C to the initial boiling point of the residua to be upgraded, the reaction being carried on in the li~uid phase at temperatures frorn 427 C to 504 C and pressures from 1.4 MPa to 6.9 MPa.

Despite these disclosures, there remained a need for a process for upgrading residua at low pressures with a reduced production of coke. The `~ ~

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present invention provides a method for treating heavy hydrocarbonaceous oil feedstocl<, comprising:
(a) mixing said heavy hydrocarbonaceous oil Feedstock and a hydrogen-donating hydrocarbon diluent boiling in a range from 180C to 400 C at atmospheric pressure, in a ratio compared to said feedstock of 0.02:1 to 1.0:1 by weight in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420C to 500C in a heating zone to form a reaction mass;
10 (c) maintaining said reaction mass in a coking zone at a temperature from 400C to 490C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes; and (d) recovering liquid hydrocarbon products and coke from said coking zone.
The invention also resides in a method for reducing the amount of coke production in the coking of heavy hydrocarbonaceous oil feedstock, comprising the steps as listed above.
In this disclosure and claims, all references to percentages and proportions are references to percentages and proportions by weight, and 20 boiling temperatures refer to atmospheric pressure, unless otherwise indicated.
The process of the invention utilises a hydrogen-donating hydrocarbon diluent to provide sufficient hydrogen to add to at least a portion of the radicals that are created from the residuum feedstock when it is 25 exposed to temperatures in the coking range, i.e. from 420C to 500C. The hydrogen-donating diluent has a boiling range from 180C to 400C, preferably from 200C to 350C, at atmospheric pressure. Advantageously, the donor diluent can be a highly aromatic light cycle oil generated in a catalytic lZ~

cracking process; the oil is partially hydrogenated by known methods to produce a hydrogen donor diluent containing, for example, tetralin and substituted tetralins. Preferably, hydrogen-donating compounds and hydrog~n donor precursors together comprise at least 40 percent of the hydrogen donor 5 diluent. Hydrocarbons boiling in the upper portion of the aforementioned broad boiling range, that is, boiling -from about 350C to 400C, generally participate to a minor degree, if at all, as hydrogen-donating materials during donor hydrocracking. Some of those hydrocarbons, called herein hydrogen donor precursors, are converted during donor hydrocracking into compounds 10 that can be partially hydrogenated to hydrogen-donating compounds boiling in the aforementioned broad boiling range. Thus where a donor recycle is used as will be described below, the hydrogen-donating diluent can advantageously include materials boiling up to 400C. Compounds included in the hydrogen-donating diluent that do not actually supply hydrogen nevertheless have some 15 usefulness in the process in that they act as diluents to reduce the viscosity of the reaction mass and thereby assist in checking deposition of coke on the furnace tube walls. The proportion of hydrogen-donating hydrocarbon diluent in relation to the residuum feedstock can be from about 0.02:1 to 1.0:1, preferably from 0.15:1 to 0.5:1. Optionally, a portion of the hydrogen donor 20 requirement can be supplied by recycled hydrogen donor material obtained by fractionating the coker liquids product and partially hydrogenating at least a portion of a 180C to 400C donor precursor fraction, or preferably a 200C
to 350C fraction, to produce a recycle hydrogen donor material. The ratio of recycle hydrogen donor material to fresh hydrogen donor material can be from 25 0.1:1 to 2:1.
The temperature of the reaction mass entering the coker from a transfer tube can be in the range from 420C to 500C, preferably from 450C
to 500C. The relationship of time in the heating zone and temperature of ` `:

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that ~one is governed by the nature of the heavy hydrocarbonaceous oil being treated. Oils that tend to crack easily are kept for a shorter residence time or at a lower temperature, or both, than oils that are more refractory. The heavy hydrocarbonaceous oil feedstock can comprise a residuum from 5 atmospheric or vacuum distillation of conventional crude oil, or an atmospharic or vacuum residuum of heavy oil or bitumen. Where the content of naphthas and distillates is low, as in oil sands bitumens, whole bitumen can be used as the feedstock oil. Mixtures of the above-mentioned oils can also be fed to the process. In general, in treating a given heavy feedstock, a high 10 temperature requires a short residence time in the heating zone, as is known to those skilled in the art. The temperature maintained In a coke drum is generally lower than the material in the transfer tube, and can be from 400C
to 490C, preferably from 425DC to 480C. Operating pressure can be from atmospheric, i.e. 101 kPa, to about 600 kPa, preferably from 200 kPa to 400 kPa.
The liquid product material obtained from an overhead stream off the coke drum can be fractionated. At least a portion of a material boiling in the heavy gas oil range, i.e. above 400C, can be recycled to be mixed with fresh residuum feedstock. The bottoms recycle-to-fresh residuum feed ratio 20 can be up to about 0.4:1. In refinery operation, a bottoms recycle-to-fresh feed ratio of 0.1:1 to 0.3:1 is generally sufficient to remove the entire heavy gas oil product. Optionally, both hydrogen donor material and heavy gas oil can be recycled.
The hold time of reaction mass in the coke drum can be from 5 25 minutes to 60 minutes. In a typical refinery, delayed coking according to the invention is performed using two coke drums alternately. When one of the drums is filled with coke, it is disconnected from the preheating furnace and the coke product is discharged while the other drum is being f illed with 1- .

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reaction mass fr~m a preheating furnace via a transfer tube. The initial reaction mass entering either coke drum after startup of that drum is subjected to a longer period of exposure to coking cor.ditions than the last reaction mass prior to shutdown of that drum. The method of the invention 5 can be performed in such refinery conditions.
Figure 1. represents a preferred ~orm of apparatus for carrying out the process of the invention.
Referring to Figure 1, .in a preferred embodiment of the process of the invention, vacuum residuurn feedstock is fed by lines 11 and 13 1û to surge drum 2~ Partially hydrogenated light cycle oil is fed by line 12, and blended with residuum to be fed into drum 2 by line 13, and optionally recycled gas oil is added by line 17. The resulting blend is taken through line 14 to coker preheating furnace 6 where it is heated to coking temperature, typically 420C to 500C, thence by line 15 to coke drum 7 or coke drum 7a. The drum 15 not being filled at the time is cut off from the system by valves 3 and 4 or 3a and 4a. After a suitable holding period in the coke drum, at a temperature preferably from 400C to 480C, and a pressure substantially lower than the pressure in the preheating furnace 6, during which period coker overheads are removed by line 16 to fractionator 8 from which products from gases to heavy 20 gas oil are withdrawn by lines 21 to 24, the drum is taken out of service and its coke content removed via Iine 18 or 18a. Optionally at least a portion of heavy gas oil boiling above 400C can be recycled via line 17; for further treatment in the coker, and if desired, all of the heavy gas oil can be thus converted to lighter petroleum products or to coke. Where such strearn is not 25 recycled, it can advantageously be fed to a f luid catalytic cracking zone.
Optionally a portion of the hydrogen donor requirement ca~ be satisfied by passing through line 19 at least a portion of the gas oil fraction in line 23 boiling between 18ûC and 400C, preferably between 200C and 35ûC~

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partially hydrogenating the gas oil in hydrogenation zone 9 and recycling the resulting recycle hydrogen donor material through line 20 to blend with fresh donor fed by line 12.
Example 1 Four parts by volume of a vacuum residuum of conventional crude oil boiling above 510C was blended with one part of a mildly hydrotreated light cycle oil boiling from 180C to 390C and one part o-F coker recycle gas oil boiling above 400C. The gas oil served as a diluent providing a lower viscosity to the reaction mixture, and also entered into the donor coking 10 reaction to some extent. Hydrogen-donating species, ie. tetralin and substituted tetralins, comprised about 35% by weight of the cycle oil. The blend was heated to 493C in a commercial-scale coker furnace at 1.48 MPa (absolute) and passed through a pressure reducing valve into a coke drum where the reaction mass was held at 471C and 240 kPa as the coke drum 15 filled with coke. Coker overheads were taken off the fractionator with yields(net of the added cycle oil) shown as Run 1 in Table 1. The coke product contained 12 percent Volatile Combustible Matter (VCM). A similar run was done with no added cycle oil, and product yields are shown as Run 2.

Conditions Run 1 Run 2 Coke Drum Temp., C 471 471 Hydrotreated Cycle Oil addition, % of total feed 16.7 none Product Yield, % on residuum feed Vapours (to C4) 10.7 10.8 Gasoline (C5-190 C) 3.3 4.2 Distillate (190-320C) 29.9 35.1 Gas Oil (320-480C) 37.5 25.4 Coke (12% VCM) 19.6 24.5 3û

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During the operation in Run 1 according to the invention, about 12.5 m3/m3 (70 SCFB) of hydrogen was transferred to the residuum products.
The Bromine Number of the gasoline boiling range product was decreased from 52 in the prior art operation of Run 2, to 43 in the process of the invention, 5 illustrating a significant improvement in the saturation of the gasoline.
Examples 2-3 In a laboratory apparatus, a series of simulated delayed coking runs was performed. The apparatus consisted of a single reactor vessel, provided with means for temperature and pressure control. Each reactor charge was 10held at 427nC and 1.1 MPa for five minutes, then the pressure was reduced to 233 kPa and the treatment was continued at the above temperature for another 20 minutes. The coke yield was normalized to 12% volatile combustible matter (VCM) content for the coke product of each run. The results are summarized in Table 2.

Run 3 Run 4 Run 5 ConditionsC_mparisonExample 2Example 3 Hydrotreated cycle oil addition to recycle gas oil to residuum feed, ratios by weight 0:1:4 1:1:4 2:0:4 Coke yield, % by weight on residuum feed26.5 20.9 16.1 Coke yield reduction, compared to Run 3, U/o _ 21 39 The process of the invention is thus shown to be ef Fective in lowering the production o F coke on both laboratory-scale and commercial-scale apparatus. Additional advantages are that the process produces a more saturated gasoline product than conventional processes, and reduces fouling of 30 furnace tubes in the heating zone.

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S UPP:LEMENTARY D IS CLOS URE
The present invention provides a me ~od for treating a heavy petroleum Eeedstock, comprising:
(a) mixing said feedstock and a hyd~ogen-donating hydrocarbon diluent boiling in a range from 180C to 400 C at atmospheric pressure, in a ratio compared to said feedstock of 0.02:1 to 1.0:1 by weight in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420 C to 500 C for a time from about 1 to 10 minutes in the liquid state in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400C to 4~0C and pressure from 101 kPa to 600 kPa for a residence time of from 5 -to 60 minutes; and (d) recovering liquid hydrocarbon products and coke from said coking zone.

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The invention also resides in a method for reducing the amount of coke production ln the coking of heavy petroleum feedstoek, eomprising the steps as listed abova.

The invention further provides a method for inereasing the produetion of naphtha fraetion from a heavy petroleum feedstock in a eombined coking and fluid catalytic eraeking operation, comprising:
(a) mixing said feedstock and a hydrogen-donating hydrocarbon diluent boiling in a range from 180C to 400C in a ration compared to said feedstock of 0.02:1 to 1.0:1 in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420C to 500C -for a time from about 1 to 10 minutes in the liquid state in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400C to 480C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes;
(d) recovering liquid hydroearbon products and ~5 eoke from said eoking zone;
(e) fraetionating said reeovered liquid hydroearbon produets to separate from them a heavy gas oil fraetion boiling above 400C;
(f) eontaeting said heavy gas oil fraction with a eraeking eatalyst at fluid catalytic eracking conditions in a fluid eatalytie eraeking zone to produee a eatalytically cracked material;
and B~

(g) fractionating said catalytically cracked material into a naphtha fraction and at least one other fraction.

In this disclosure and claims, all referances to percentages and proportions are references to percentages and proportions by weight, and boiling temperatures refer to atmospheric pressure, unless otherwise indicated.

The process of the invention utilizes a hydrogen-donating hydrocarbon diluent to provide sufficient hydrogen to add to at least a portion of the radicals that are created from the residuum feedstock when it is exposed to temperatures in the coking range, i.e. from 420C to 500C. The hydrogen-donating diluent has a boiling range from 1~0C to 400C, pre~erably from 200C to 350C, at atmospheric pressure~
Advantageously, the donor diluent can be highly aromatic light cycle oil generate ~n a catalytic cracking ~0 proce~s; the oil is partial~y hydrogenated by know methods to produce a hydrogen donor diluent containing, for example tetralin and substituted tetralins.
Preferably, hydrogen-donating compounds and hydrogen donor precursors together comprise at least 40 percent of the hydrogen donor dilusnt. Hydrocarbons boiling in the upper portion of the aforementioned broad boiling range, that is, boiling from about 350C to 400C, generally participate to a minor degree, if at all, as hydrogen-donating materials during donor hydrocracking.
Some of those hydrocarbons, called herein hydrogen donor precursors, are converted during donor hydrocracking into compound that can be partially hydrogenated to hydrogen-donating compounds boiling in the aforementioned broad boiling range. Thus where a donor recycle is used as will be described below, the ~246~

hydrogen-donating diluent can advantageously include materials boiling up to 400C. Compounds included in -the hydrogen-donating diluent that do not actually supply hydrogen nevertheless have some usefulness in the process in that they act as diluents to reduce the viscosity of the reaction mass and thereby assist in checking deposition of coke on the - lla -furnace tube walls. The proportion of hydrogen-donating hydrocarbon diluent in relation to the residuum feedstock can be from about 0.02:1 to 1.0:1, preferably from 0.15:1 to 0.5:1. Optionally, a portion of the hydrogan donor requirement can be supplied by recycled hydrogen donor material obtained by fractionating the coker li~uids product and partially hydrogenating at least a portion of a 1~0C to 400C donor precursor raction, or preferably 200C to 350C fraction, to produce a recycle hydrogen donor material. The ratio of recycle hydrogen donor material to fresh hydrogen donor material can be from 0.1:1 to 2:1.

The temperature of the reaction mass entering the coker from a transfer tube can be in the range from 420C to 500C, preferably from 450C to 500C. The relationship of time in the heating zone and temperature of that zona is governed by the nature of the heavy hydrocarbonaceous oil being treated. Oils that tend to crack easily are kept for a shorter residence time or a-t a lower temperature, or both, than oils that are more refractory. The heavy petroleum feedstocks for the method of the invention include residua from the atmospheric or vacuum distillation of conventional crude oil, of heavy oil, for example Lloydminster, or of oil sands bitumen, for example Athabasca; or undistillad heavy oil or oil sands bi-tumens having API gravity of 20 or lower, i.e. specific gravity of at least U.9340; or mixtures thereof. In ganeral, in treating a given heavy feedstock, a high temperature requires a short residence time in the heating zone, as is known -to those skilled in the art. The temperature maintained in a coke drum is generally lower than the material in the transfer tube, and can be from 400C to 480C, preferably 425C
to 480C. Operating pressure can be from atmospheric, ie 101 kPa, to about 600 kPa, preferably 200 kPa to ~246~

400 kPa. The invention depends for its efficacy in improving liquid yield upon the presence of the hydrogen-donating materials with the feeds-tock at elevated temperature in the liquid state for a residence time sufficient to p~rmit hydrogen transfer, and is thus particularly applicable to delayed coking. Hydrogen donors generally must be in the liquid state to transfer hydrogen to high-boiling hydrocarbons.

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The liquid product ma-terial obtained from an overhead stream off the coke drum can ba fractionated.
At least a portion of a material boiling in the heavy gas oil range, i.e. above 400C, can be recycled to be mixed with fresh residuum feedstock. The bottoms recycle-to-fresh residuum feed ratio can be up to ahout 0.4:1. In refinery operation, a bottoms recycle-to-fresh reed ration of 0.1:1 to 0.3:1 is generally sufficient to remove the entire heavy gas oil product.
Optionally, both hydrogen donor material and heavy gas oil can be recycled.

In a refinery operation, the gas oil fraction of the liquid product material from delayed coking is generally catalytically cracked to increase the yisld of gasoline products. Thus, the invention includes a combined donor coking-catalytic cracking operation in which the yield of the naphtha fraction is increased by the increased production of catalytic cracking feedstock, generally coker gas oil, in a donor coking step. A catalytic cracking unit in the method of the invention is preferably a fluidized-bed unit well know in the art. Conventional conditions are employed int he fluid catalytic cracking step, including for example, a catalyst circula-tion-to-cracking feedstock ratio in the range from 0.01 to 0.2 tonnes of catalyst per tonne per day of feedstock throughput, a riser zone temperature from 475C to 750C and a riser zone pressure from 100 kPa to 350 kPa. Optionally the coker gas oil can be hydrogenated before being ~ed to the catalytic cracking zone. The catalytic crscker effluent is generally fractionated to separate naphtha and distillate products therefrom. Optionally the catalytic cracker effluent gas oil and bottoms can be recycled to the coking zone.

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The hold time of reaction mass in the coke drum can be from 5 minutes to 60 minutes. In a typical refinery, delayed coking according to the invention is performed using two coke drums alternately. When one of the - 13a -~;24~

drums is filled with coke, i-t is disconnected from the preheating furnace and the coke product is discharged while the other drum is being filled with reaction mass from a preheating furnace via a transfer tube. The initial reaction mass entering either coke drum after startup of that drum is subjected to a longer period of exposure to coking conditions than the last reaction mass prior to shutdown of that drum. The method of the invention can be performed in such refinery conditions.

The invention will now be described further, with reference to the attache drawing in which:
Figure 2 illustrates a prefarred apparatus for coking and aatalytic cracking according to the invention.
In the preferred embodiment illustrated by Figure 2, vacuum residuum feedstock is fed by lines 111 and 113 to surge drum 102. Hydrogen-donor diluent is fed by line 112, and blended with the residuum to fed into drum 102 by line 113; recycled gas-oil is optionally added by line 117. The resulting blend is taken through line 114 to coker pre-heating furnace 106 where it is heated to coking temperature and fed through a pressure reducing value (not shown) and line 115 to coke drum 107 or 107a as described with reference to Figure l; the coke drums are filled alternately, by use of valves 103/103a and 104/104a. While each respective coke drum is being filled, overheads are removed by line 116 to first fractionation zone 108, from which products are withdrawn by lines 121 and 125. When drum 107 or 107a is suitably filled, it is shut off from the ~est of the system and its coke content removed by lina 118 or 118a. In a preferred operation, at least a portion of the gas-oil fraction in line 124, optionally together with a portion of bottoms from line 125, is taken by ~46~
lines 128, 129, and 140 to catalytie eracking zone 130, whieh is preferably a fluid eatalytie craeking unit.
After suitable eontaet with eracking eatalyst at eonditions well known in the art, non-solid eracked ~ - 14a -~%~6~

prodl~cts are taken by line 141 to second fractionation zone 131 for separation of products which are r~moved by lines 142 to 145. These products can be combined with products from the donor coking zone 108, in lines 121 to 125, where desired. Catalytic cracking bottoms in line 145 can be removed by line 146 and optionally at least a portion of the bottoms can be recycled by line 147 and 117 to the surge drum 102. Optionally, as described above with reference to Figure 1, a portion of the distillate fraction in lin~ 123 or from line 144, boiling between 180C and 400C, preferably between 200C and 350C can be recycled o surge drum 102 and heating zone 106 by line 119 or lines 150 and 152 respectively, partially hydrogenated by hydrogen from line 127 in hydrogenation zone 109 and taken by line 120 to be reused in the coking step. In a fluid catalytic cracking operation, a portion of distillate in line 150 is generally recycled a shown by line 151 in Figure 2;
this recycled stream is termed cycle oil. In the combined coking/catalytic cracking process, the ~0 production of valuable naphtha fraction (line 143 in Figure 2) is significantly increase over the prior art process when hydrogen-donor diluent is fed with the residuum feedstock to the coking step.

Example 4 Four parts by volume of a vacuum residuum of conventional crude oil boiling above 510C was blended with one part of a mildly hydrotreated light cycle oil boiling from 180C to 390C and one part of coker recycle gas oil boiling above 400C. The gas oil served as a diluent providing a lower viscosity to the reaction mixture, and also entered into the donor coking reaction to some extent. Hydrogen-donating speciss, ie. tetralin and ~ 15 -64~

substitutad tetralins, comprised about 35~ by weight of the cycle oil. The blend was heated to 493C in a commercial-scale coker furnace at 1.48 MPa (absolute) and passed through a pressure reducing valve into a coke drum where the reaction mass was held at 471C and 240 kPa as the coke drum ~illed with coke. Run 6 included a charge of 2% steam, essentially inert under the reaction conditions as Run 1 of Example 1. The presence of the va~orous steam decrease the residence time in the heating zone to about 0.8 minutes, and as sean in Table 3, prevented the hydrogen donor from improving the liquid product yield from the coking zone.

Conditions Run 6 Coke Drum Temp., C 471 Hydrotreated Cycle Oil addition, % of total feed 16.7 Steam Addition, ~ of total feed 2.0 Residence time in liquid state 0.8 minutes ~0 Product Yield, % on residuum feed Vapours (to C4) Gasoline (C5-190C) Distillate (190-480C) 75.5 Gas Oil (350-430C) Coke (12% VCM) 24.5 Example 5 In an example of a combined hydrogen donor coking/fluid catalytic cracking process, four parts by volume of a vacuum residuum of conventional crude oil boiling above 510C are blended with one part of mildly hydrotreated light cycle oil boiling from 180C to 390C
and one part of coker product bottoms boiling above 400C. Hydrogen-donating species comprise ~Z~6~
about 35% by weight of the cycle oil. The blend is heated to 490C at 1.48 MPa (absolute) and passed through a pressure-reducing valve into a coke drum where the reaction mass is held at 470C and 240 kPa as tha coke drum fills with coke. Coker overheads are taken off and fractionated, and the gas-o~l fraction boiling above about 320C is fed to the riser zone of a fluid catalytic cracking unit operated at conventional cracking conditions including a maximum riser zone temperature of 600C. After separating the cracked hydrocarbon fluids from the catalyst and other solids, the fluid are fractionated. The gasoline and distillate yields of the combined fractionation of coker overheads and the overheads from the catalytically cracked coker gas oil are shown in Table 4 as Run 7. Run 8 show the yields slate from a similar coking/catalytic cracking process without the addition of any hydrogen donor to the coking step.

~0 Conditions Run 7 Run 8 Coke Drum Temp., C 470 470 Hydrotreated Cycle Oil addition, % of total feed 16.7 none ~5 Steam Addition none none Residence time in liquid state 3 min 3 min Product Yield, ~ on residuum feed Gasoline (C5-220C)19.2 15.3 Distillate (220-344C) 36.6 39.6 The process of the invention is effective in lowering the production of coke on both laboratory-scale and commercial-scale delayed coking apparatus. It is also effective in increasing the production and the ~2~6~

quality of catalytic cracking gasoline in a combined process including both coking and catalytic cracking steps. A further advantage is that the process reduces or eliminates coke build-up on the furnace tubes on the heating zone.

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Claims (28)

What is claimed is:

1. A method for treating heavy hydrocarbonaceous oil feedstock, comprising:
(a) mixing said heavy hydrocarbonaceous oil feedstock and a hydrogen-donating hydrocarbon diluent boiling in a range from 180°C to 400°C at atmospheric pressure, in a ratio to said feedstock of 0.02:1 to 1.0:1 by weight in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420°C to 500°C in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400°C to 490°C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes; and (d) recovering liquid hydrocarbon products and coke from said coking zone.

2. A method as claimed in Claim 1, wherein said heating zone conditions include a temperature in the range from 450°C to 500°C.

3. A method as claimed in Claim 1, wherein said hydrogen-donating diluent comprises a partially hydrogenated light cycle oil, wherein hydrogen-donating hydrocarbons and hydrogen donor precursors together comprise at least 40 percent of said light cycle oil.

4. A method as claimed in Claim 1, further comprising the steps of:
(e) fractionating said recovered liquid hydrocarbon products to separate therefrom hydrocarbon streams boiling below 400°C, to produce a heavy gas oil Fraction boiling in a range above 400°C;
and (f) recycling at least a portion of said heavy gas oil fraction to said mixing zone.

5. A method as claimed in Claim 4, wherein the ratio of said recycled heavy gas oil fraction to said residuum is from 0.1:1 to 0.3:1.

6. A method as claimed in Claim 4, wherein the entire amount of said heavy gas oil fraction is recycled to said mixing zone.

7. A method as claimed in Claim 1, wherein said hydrogen-donating diluent boils in a range from 200°C to 350°C at atmospheric pressure.

8. A method as claimed in Claim 1, further comprising the steps of:
(e) fractionating said recovered liquid hydrocarbon products to separate therefrom a donor precursor fraction boiling in a range from about 180°C to 400°C;
(f) partially hydrogenating at least a portion of said donor precursor fraction to produce a recycle hydrogen-donating material; and (g) recycling said recycle hydrogen-donating material to form at least a portion of said hydrogen-donating diluent.

9. A method as claimed in Claim 6 wherein said recycle hydrogen-donating material is used in a ratio to fresh hydrogen-donating diluent from 0.1:1 to 2:1.

10. A method as claimed in Claim 1, wherein said hydrogen-donating hydrocarbon diluent is mixed with said feedstock in a ratio to said feedstock of 0.15:1 to 0.5:1.

11. A method as claimed in Claim 1, wherein said pressure is from 200 kPa to 400 kPa.

12. A method for reducing the amount of coke production In the coking of heavy hydrocarbonaceous oil feedstock, comprising:
(a) mixing said heavy hydrocarbonaceous oil feedstock and a hydrogen-donating hydrocarbon diluent boiling in a range from 180°C to 400°C at atmospheric pressure, in a ratio to said feedstock of 0.05:1 to 1.0:1 by weight in a mixing zone;
(b) rapidly heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420°C to 500°C in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400°C to 490°C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes; and (d) recovering liquid hydrocarbon products and coke from said coking zone.

13. A method as claimed in Claim 1 or Claim 12, wherein the ratio of said hydrogen-donating material to said petroleum residuum is from 0.2:1 to 0.5:1.

14. A method as claimed in Claim 1, further comprising the steps of:
(e) fractionating said recovered liquid hydrocarbon products to separate therefrom a donor precursor fraction boiling in a range from about 180°C to 400°C and a heavy gas oil fraction boiling above 400°C;
(f) partially hydrogenating at least a portion of said donor precursor fraction to produce a recycle hydrogen-donating material;
(g) recycling said recycle hydrogen-donating material to form at least a portion of said hydrogen-donating diluent; and (h) recycling at least a portion of said heavy gas oil fraction to said mixing zone.

CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

15. (a) mixing said feedstock and a hydrogen-donating hydrocarbon diluent to a temperature from 420°C to 500°C
at atmospheric pressure, in a ratio to said feedstock of 0.02:1 to 1.0:1 by weight in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420°C to 500°C for a time from about 1 to 10 minutes in the liquid state in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400°C to 480°C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes; and (d) recovering liquid hydrocarbon products and coke from said coking zone.

16. A method as claimed in Claim 15 wherein said feedstock is petroleum residuum.

17. A method as claimed in Claim 16 wherein said feedstock is heavy oil or oil sands bitumen having a specific gravity of at least 0.9340.

18. A method as claimed in Claim 15 wherein said heating zone conditions include a temperature in the range from 450°C to 500°C.

19. A method as claimed in Claim 15 wherein said hydrogen-donating diluent comprises a partially hydrogenated light cycle oil, wherein hydrogen-donating hydrocarbons and hydrogen donor precursors together comprise at least 25 percent of said light cycle oil.

20. A method in Claim 15 further comprising the steps of:
(e) fractionating said recovered liquid hydrocarbon products to separated therefrom hydrocarbon streams boiling below 400°C, to produce a heavy gas oil fraction boiling in a range above 400°C; and (f) recycling at least a portion of said heavy gas oil fraction to said mixing zone.

21. A method as claimed in Claim 20 wherein the ratio of said recycled heavy gas oil fraction to said residuum is from 0.1:1 to 0.3:1.

22. A method as claimed in Claim 20 wherein the entire amount of said heavy gas oil fraction is recycled to said mixing zone.

23. A method as claimed in Claim 15 wherein said hydrogen-donating diluent boils in a range from 200°C to 350°C at atmospheric pressure.

24. A method as claimed in Claim 15 further comprising the steps of:
(e) fractionating said recovered liquid hydrocarbon products to separate therefrom a donor precursor fraction boiling in a range from about 180°C
to 400°C;
(f) partially hydrogenating at least a portion of said donor precursor fraction to produce a recycle hydrogen-donating material; and (g) recycling said recycle hydrogen-donating material to from at least a portion of said hydrogen-donating diluent.

25. A method for increasing the production of naphtha fraction from a heavy petroleum feedstock in a combined coking and fluid catalytic cracking operation, comprising:
(a) mixing said feedstock and a hydrogen-donating hydrocarbon diluent boiling in a range from 180°C to 400°C in a ratio compared to said feedstock of 0.02:1 to 1.0:1 in a mixing zone;
(b) heating said mixture of feedstock and hydrogen-donating hydrocarbon diluent to a temperature from 420°C to 500°C for a time from about 1 to 10 minutes in the liquid state in a heating zone to form a reaction mass;
(c) maintaining said reaction mass in a coking zone at a temperature from 400°C to 480°C and pressure from 101 kPa to 600 kPa for a residence time of from 5 to 60 minutes;
(d) recovering liquid hydrocarbon products and coke from said coking zone;
(e) fractionating said recovered liquid hydrocarbon products to separate from them a heavy bottoms fraction boiling above about 320°C;
(f) contacting said heavy gas oil fraction with a cracking catalyst at fluid catalytic cracking conditions in a fluid catalytic cracking zone to produce a catalytically cracked material; and (g) fractionating said catalytically cracked material into a naphtha fraction and at least one other fraction.

26. A method as claimed in Claim 25 wherein said heavy bottoms fraction boils above about 400°C.

27. A method as claimed in Claim 25 wherein said catalytically cracked material is fractionated into at least a naphtha fraction and a cycle oil fraction, at least a portion of said cycle oil fraction is recycled to said fluid catalytic cracking zone.

28. A method as claimed in Claim 27 wherein a portion of said cycled oil fraction is partially hydrogenated and recycled to said coking zone.