GB1602097A - Process for thermal cracking and coking of heavy carbonaceous oils - Google Patents

Description

(54) PROCESS FOR THERMAL CRACKING AND COKING OF HEAW CARBONACEOUS OILS (71) We, UOP INC, a corporation organized under the laws of the State of Delaware United States of America, of Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines, Illinois, 60016, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement:- The present invention relates to the conversion of heavy carbonaceous oil in particular, those oils broadly categorized in the art as "black oils". More specifically, the invention relates to the thermal cracking of heavy carbonaceous oils for the production of gasoline and speciality coke.

Atmospheric tower bottoms products, vacuum tower bottoms products, crude oil residuum, coal oil extracts, topped crude oils and tar sand oil extracts are illustrative, but not limiting, of those black oils which can be processed in accordance with the present invention.

Black oils contain exceedingly large amounts of high molecular weight sulfurous and nitrogenous compounds. In addition, these heavy hydrocarbonaceous mixtures contain significant quantities of hydrocarbon-insoluble asphaltics and organo-metallic compounds principally comprising iron, nickel and vanadium, Currently, an abundant supply of such material exists, most of which has a specific gravity less than about 0.8762 and a boiling range which indicates that 10 percent by volume, or more, boils above a temperature of 5660C. The abundant supply virtually demands conversion to satisfy the steadily increasing need for lower-boiling hydrocarbon products and especially coke.

Illustrative of those charge stocks above described, is a residuum having a specific gravity of 0.8927 and containing 0.17 weight percent sulfur and about 13 ppm. of total metals.

The principal difficulty accompanying the conversion of black oils stems from the presence of asphaltic material and the organo-metallic complexes. Fixed bed catalytic processes, although advantageously used in a myriad of hydrocarbon conversion processes, are unsuitable for use in black oil processing owing to the rapid deposition of coke onto the catalytic composite and to the extremely short period of successful on-stream operation before the catalyst "picks up" excessive metal contaminants, sometimes in amounts equal to its own weight.

Other charge stocks which may be processed according to this invention include reduced crude oil, atmospheric and vacuum gas oils, coker gas oils, fluid catalytic cracker slurry oil, furfural extract, pyrolysis residue and any other charge stocks used for the production of speciality cokes, which includes intermediate cokes (derived from asphaltenes and heavy distillable hydrocarbons) and "needle" coke (derived from highly concentrated aromatic tars or distillable hydrocarbon, and having less than 15% asphalt-derived coke).

According to the invention there is provided a process for the thermal cracking and coking of a heavy carbonaceous oil containing high molecular weight sulfurous and nitrogenous compounds and hydrocarbon-insoluble asphaltic and organo-metallic compounds, which process comprises: (a) introducing said carbonaceous oil at an intermediate point in the height of a fractionator and withdrawing from the fractionator an overhead product gasoline stream, an intermediate heavy distillate stream and a bottoms stream; (b) passing said intermediate heavy distillate through a first thermal cracking coil at an increased pressure within the range from 18 to 35 atms. absolute while heating the same to a temperature of from 482" to 5660C.

(c) passing the resulting heated stream from the first thermal cracking coil through a cracking reaction chamber; (d) passing said bottoms stream through a second thermal cracking coil at a pressure within the range from 2 to 7.8 atms. absolute while heating the same to a temperature of from 468" to 5100C.

(e) passing the resulting heated stream from the second thermal cracking coil through a coke chamber and therein accumulating a coke product, (f) withdrawing remaining effluent vapors from the coke chamber, commingling the same with effluent from the reaction chamber, and introducing the resultant mixture into the fractionator at a point below the point of introduction of the black oil thereto, and (g) recovering resultant gasoline and coke products.

In order to compete with newer hydroprocessing techniques, combination thermal cracker-cokers must utilize more advanced methods while retaining the basic and proven advantages of the cracker-coker art. As sources of energy become more scarce and therefore more expensive, it becomes imperative that all energy sources be utilized and up-graded to the maximum.

Since black oil and other heavy distillates are less desirable portions of petroleum crude oil the up-grading and utilization of these materials becomes increasingly important. Thermal crackers and cokers have always been used to convert black oils but in recent times the production of maximum quantities of gasoline together with quality, specialized coke has become even more desirable.

We have discovered an improved process for total conversion of black oils to gas, gasoline and speciality coke without overloading the coke chambers with vapors. Our improved process involves by-passing the light oil heater-reaction chamber effluent around the coke chamber and passing said effluent directly to the fractionator. The thermal tar present in the reaction chamber effluent is recycled through the fractionator to the second thermal cracking coil ("A" coil) with the fresh feed and then to the coke chamber to contribute to the total coke produced. The light gas oil in the reaction chamber effluent plus the light gas oil generated in the "A" coil after fractionation is recycled to the first thermal cracking coil ("B" coil) and the gas and gasoline are removed overhead from the fractionator.This type of operation permits the high combined feed ratios necessary for total conversion at reasonable coke chamber vapor velocities. Operation with our invention permits the use of smaller diameter coke chambers and/or lower pressure coke chambers.

The operating conditions for the first thermal cracking (B) coil include a temperature of from 482" to 566"C. and a pressure of from 18 to 35 atmospheres absolute. The operating conditions for the second thermal cracking (A) coil include a temperature of from 468" to 5100C. and a pressure of from 2 to 7.8 atmospheres absolute. The foregoing coil pressures refer to the pressures at the outlets of the coils.

In further describing the present invention reference will be made to the drawing accompanying the provisional specification, which is presented for the sole purpose of illustration. Thus, miscellaneous appertenances, including valves, controls, instruments, pumps, heat exchangers, startup lines and heat recovery circuits have been eliminated. The use of this type of conventional hardware is well within the purview of those skilled in the techniques of petroleum refining and processing.

The drawing is a simplified schematic flow diagram of a representation embodiment of the invention.

With reference now to the drawing, a black oil charge stock, following heat exchange with hot effluent, which technique is not illustrated, is introduced through line 1 into fractionator 2. Fractionator 2 is maintained at a temperature and pressure to yield a gasoline stream via line 3, a heavy distillate stream via line 4 and a black oil stream via line 5. The heavy distillate stream is introduced into "B" coil 6 via line 4 which coil is maintained at a maximum temperature of about 527"C and outlet pressure of about 23 atms. absolute. The effluent from "B" coil 6 is transferred to reaction chamber 8 via line 7. Reaction chamber 8 is maintained at a pressure of about 23 atms. absolute. The effluent from reaction chamber 8 is introduced into fractionator 2 via line 9. The black oil stream is introduced into "A" coil 10 via line 5 which coil is maintained at a maximum temperature of about 510"C and outlet pressure of about 5.1 atms. absolute.

The effluent from "A" coil 10 is transferred to coke chamber 12 via line 11. Coke chamber 12 is maintained at a pressure of about 5.1 atms. absolute. The effluent from coke chamber 12 is introduced into fractionator 2 via line 13 and thence via line 9.

The following example is presented in illustration of the instant invention.

Example A conventional prior art thermal crackercoker is used to process 2,225 cubic meters per day of a reduced crude having a specific gravity of 0.8927 and containing 0.17 wt. % sulfur and 13 ppm. total metals. The products are recovered and the distribution of the coke chamber effluent is presented in Column A, Table I. A processing scheme as exemplified in the drawing is also utilized to process the same volume per day of reduced crude as described hereinabove, and operating with a combined feed ratio of 2 in the A coil and with an overall combined feed ratio of 4.8. The products are recovered and the distribution of the coke chamber effluent is presented in Column B, Table I.

From Table I, it is apparent that the effluent from the coke chamber is significantly less when using the process of the present invention, which produces resulting economics of operation.

TABLE I Coke Chamber Effluent Distribution A B Vapor Vapor, Product Total wt.%* Mols/Hr. Total wt. %* Mols/Hr.

Hydrogen Sulfide 0.1 5 0.1 5 C4-minus 26.7 1286 10.7 514 C5-2040C. 55.7 846 22.2 338 Coke 17.5 - 17.5 - "A" coil recycle 100 486 100 468 "B" coil recycle 280 2454 480 5059 150.5 1325 *Percentages based upon fresh feed.

Generally speaking, the charge stock will usually have an end boiling point above 566"C and preferably at least 10% by volume of the charge stock will boil above this temperature.

WHAT WE CLAIM IS: 1. A process for the thermal cracking and coking of a heavy carbonaceous oil containing high molecular weight sulfurous and nitrogenous compounds and hydrocarbon-insoluble asphaltic and organo-metallic compounds, which process comprises: (a) introducing said carbonaceous oil at an intermediate point in the height of a fractionator and withdrawing from the fractionator on overhead product gasoline stream, an intermediate heavy distillate stream and a bottoms stream; (b) passing said intermediate heavy distillate through a first thermal cracking coil at an increased pressure within the range from 18 to 35 atms. absolute while heating the same to a temperature of from 482" to 5660C.

(c) passing the resulting heated stream from the first thermal cracking oil through a cracking reaction chamber; (d) passing said bottoms stream through a second thermal cracking coil at a pressure within the range from 2 to 7.8 atms. absolute while heating the same to a temperature of from 468" to 5100C.

(e) passing the resulting heated stream from the second thermal cracking coil through a coke chamber and therein accumulating a coke product, (f) withdrawing remaining effluent vapors from the coke chamber, commingling the same with effluent from the reaction chamber, and introducing the resultant mixture into the fractionator at a point below the point of introduction of the black oil thereto, and (g) recovering resultant gasoline and coke products.

2. A process according to Claim 1, wherein the charge stock has an end boiling point above 566"C.

3. A process according to Claim 2, wherein at least 10% by volume of the charge stock boils above a temperature of 566"C.

4. A process for the thermal cracking and coking of a heavy carbonaceous oil carried out substantially as hereinbefore described with reference to the drawing accompanying the provisional specification.

5. Coke when obtained by a process according to any of Claim 1 to 4.

6. Gasoline when obtained by a process according to any of claims 1 to 4.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   of the coke chamber effluent is presented in Column A, Table I. A processing scheme as exemplified in the drawing is also utilized to process the same volume per day of reduced crude as described hereinabove, and operating with a combined feed ratio of 2 in the A coil and with an overall combined feed ratio of 4.8. The products are recovered and the distribution of the coke chamber effluent is presented in Column B, Table I.

   From Table I, it is apparent that the effluent from the coke chamber is significantly less when using the process of the present invention, which produces resulting economics of operation.

   TABLE I Coke Chamber Effluent Distribution A B Vapor Vapor, Product Total wt.%* Mols/Hr. Total wt. %* Mols/Hr.

   Hydrogen Sulfide 0.1 5 0.1 5 C4-minus 26.7 1286 10.7 514 C5-2040C. 55.7 846 22.2 338 Coke 17.5 - 17.5 - "A" coil recycle 100 486 100 468 "B" coil recycle 280 2454

   480 5059 150.5 1325 *Percentages based upon fresh feed.

   Generally speaking, the charge stock will usually have an end boiling point above 566"C and preferably at least 10% by volume of the charge stock will boil above this temperature.

   WHAT WE CLAIM IS: 1. A process for the thermal cracking and coking of a heavy carbonaceous oil containing high molecular weight sulfurous and nitrogenous compounds and hydrocarbon-insoluble asphaltic and organo-metallic compounds, which process comprises: (a) introducing said carbonaceous oil at an intermediate point in the height of a fractionator and withdrawing from the fractionator on overhead product gasoline stream, an intermediate heavy distillate stream and a bottoms stream; (b) passing said intermediate heavy distillate through a first thermal cracking coil at an increased pressure within the range from 18 to 35 atms. absolute while heating the same to a temperature of from 482" to 5660C.

   (c) passing the resulting heated stream from the first thermal cracking oil through a cracking reaction chamber; (d) passing said bottoms stream through a second thermal cracking coil at a pressure within the range from 2 to 7.8 atms. absolute while heating the same to a temperature of from 468" to 5100C.

   (e) passing the resulting heated stream from the second thermal cracking coil through a coke chamber and therein accumulating a coke product, (f) withdrawing remaining effluent vapors from the coke chamber, commingling the same with effluent from the reaction chamber, and introducing the resultant mixture into the fractionator at a point below the point of introduction of the black oil thereto, and (g) recovering resultant gasoline and coke products.
2. 2. A process according to Claim 1, wherein the charge stock has an end boiling point above 566"C.
3. 3. A process according to Claim 2, wherein at least 10% by volume of the charge stock boils above a temperature of 566"C.
4. 4. A process for the thermal cracking and coking of a heavy carbonaceous oil carried out substantially as hereinbefore described with reference to the drawing accompanying the provisional specification.
5. 5. Coke when obtained by a process according to any of Claim 1 to 4.
6. 6. Gasoline when obtained by a process according to any of claims 1 to 4.