METHOD FOR PRODUCING ANODE GRADE COKE FROM CRUDE OILS

Abstract

The present invention provides a method for production of anode grade coke by processing crude oil feed stock in a DCU. The method comprising separation of low boiling light molecular weight components from heavier molecules and processing the same in Delayed Coker Unit after mixing with aromatic rich stream to overcome the operational issue envisaged due to processing of paraffin containing crude feed. The coke so obtained was calcined to produce an improved quality coke having lesser impurities (Sulfur <3 wt %) and better crystallinity.

Claims

1. A method for production of anode grade coke in a delayed coker unit (DCU), the method comprising: i. charging the hydrocarbon feedstock to a desalter unit to obtain a desalted crude oil stream; ii. routing the desalted stream to a pre-separator vessel to obtain a lighter stream having a boiling point <300° C. and heavier stream fraction having a boiling point >300° C.; iii. routing the heavier stream fraction to the furnace; iv. feeding the heated effluent stream from the furnace to a coke drums for cracking into lighter hydrocarbons and coke; v. routing coke drum effluent to a main fractionator to obtain light coker gas oil, heavy coker gas oil, fuel oil; vi. mixing gaseous product stream from main fractionator with the lighter stream having boiling point <300° C.; vii. routing coke obtained from coke drum to feed silo and obtaining raw coke; and viii. calcining the coke in a-kiln and routing the calcined coke to cooler to obtain anode grade coke.

2. The method as claimed as claim 1, wherein the hydrocarbon feedstock is selected from the group consisting of different crude oils, sour crude oil, sweet crude oils, opportunity crudes and heavier streams generated thereof.

3. The method as claimed in claim 1, wherein the desalted stream along with aromatic rich stream is added to pre-separator vessel in step (ii) to enable recovery of valuable lighter boiling fraction boiling below 300° C. and to enhance the coke quality.

4. The method as claimed in claim 1, wherein the coke drums are operated at an overhead temperature of 430-460° C., and a pressure of 1-5 Kg/cm.sup.2 (g).

5. The method as claimed in claim 1, wherein the temperature of heated effluent stream from furnace is in the range of 480-510° C.

6. The method as claimed as claim 3, wherein the aromatic rich stream is selected from the group consisting of pyrolysis tar, aromatic tar, clarified light oil.

7. The method as claimed as claim 1, wherein the heavier stream fraction having a boiling point >300° C. obtained from step (ii) is mixed with a recycle stream, before routing to the furnace.

8. The method as claimed as claim 7, wherein the Coke drum effluent in the main fractionator is mixed with an aromatic rich stream, to condense heavier molecules from coke drum effluent and to produce recycle stream.

9. The method as claimed as claim 8, wherein the aromatic rich stream is selected from the group consisting of pyrolysis tar, aromatic tar, clarified light oil

10. The method as claimed in claim 1, wherein the sulfur and nitrogen content of coke produced are ≤3 wt and 0.1. %, respectively and is of anode grade specification.

11. The method for production of anode grade coke in a delayed coker unit (DCU) as claimed in claim 1, the method comprising: i. charging the hydrocarbon feedstocks to a desalter unit to obtain a desalted stream; ii. routing the desalted stream to a pre-separator vessel to obtain a lighter stream having boiling point <300° C. and a heavier stream fraction having a boiling point >300° C.; iii. routing aromatic rich Clarified Light Oil (CLO) stream to the bottom of pre-separator vessel to enable recovery of valuable lighter boiling fraction boiling below 300° C. and to enhance the coke quality and mixing with heavier stream fraction; iv. routing the mixed feed stream fraction consisting heavier stream fraction from Crude oil and heavier boiling fraction (300° C.+) of CLO stream to the furnace for heating to cracking temperature; v. feeding the heated effluent stream from the furnace to coke drums for cracking into lighter hydrocarbons and coke; vi. routing coke drum effluent to a main fractionator to obtain light coker gas oil, heavy coker gas oil, fuel oil; vii. mixing gaseous stream from main fractionator with the lighter stream having boiling point <300° C.; viii. routing coke obtained from coke drum to feed silo, and obtaining raw coke; and ix. calcining the raw coke in a kiln and routing the calcined coke to a cooler to obtain anode grade quality coke.

12. The method for production of anode grade quality coke in a delayed coker unit (DCU) as claimed in claim 1, the method comprising: i. charging the hydrocarbon feedstocks to a desalter unit to obtain a desalted stream; ii. routing the desalted stream to a pre-separator vessel to obtain lighter stream having boiling point <300° C. and a heavier stream fraction having a boiling point >300° C.; iii. adding recycled stream to the heavy stream fraction and routing to the furnace for heating to cracking temperature; iv. feeding the heated effluent stream from the furnace to coke drums for cracking into lighter hydrocarbons and coke; v. routing coke drum effluent which is washed by an aromatic rich stream in a main fractionator to obtain light coker gas oil, heavy coker gas oil, fuel oil and condense heavier molecules to produce recycle stream; vi. mixing gaseous stream from main fractionator with the lighter stream having boiling point <300° C.; and vii. routing raw petroleum coke obtained from coke drum to feed silo, and obtaining a feed stream; viii. calcining the raw petroleum coke in a-kiln and routing the calcined coke to a cooler to obtain anode grade coke.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1: illustrates embodiment 1 of the present invention.

[0061] FIG. 2: illustrates embodiment 2 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0062] For promoting an understanding of the principles of the present disclosure, reference will now be made to the specific embodiments of the present invention further illustrated in the drawings and specific language will be used to describe the same. The foregoing general description and the following detailed description are explanatory of the present disclosure and are not intended to be restrictive thereof. It will nevertheless be understood that no limitation of the scope of the present disclosure is thereby intended, such alterations and further modifications in the illustrated method, and such further applications of the principles of the present disclosure as illustrated herein being contemplated as would normally occur to one skilled in the art to which the present disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinarily skilled in the art to which this present disclosure belongs. The methods, and examples provided herein are illustrative only and not intended to be limiting.

[0063] Anode grade coke is a type of coke product obtained from a Delayed Coker Unit having a sponge like structure with relatively low levels of sulfur and impurities such as metals, Nitrogen etc.

[0064] Feed Stock:

[0065] Feed stocks in the present invention are selected from sour/sweet crude oils, opportunity crudes. Aromatic oils are selected from oils such as clarified light oils, aromatic tars, pyrolysis tars.

[0066] The main embodiment of the present invention provides a method for production of anode grade coke by processing crude oil in a Delayed Coker Unit (DCU), the method comprising: [0067] i. charging the hydrocarbon feedstocks to a desalter unit to obtain a desalted crude oil; [0068] ii. routing the desalted stream oil to a pre-separator vessel to obtain lighter stream having boiling point <300° C. and heavier stream fraction having a boiling point >300° C.; [0069] iii. aromatic rich stream is routed to the bottom of pre-separator vessel and mixes with heavier stream fraction and lighter fraction of aromatic rich stream is recovered in the pre-separator along with <300° C. boiling stream of crude oil; [0070] iv. routing the mixed feed stream fraction to the furnace for heating to cracking temperature; [0071] v. feeding the heated stream from furnace to coke drum(s) for cracking into lighter hydrocarbons and coke; [0072] vi. routing coke drum effluent to main fractionator to obtain lighter coker gas oil, heavy coker gas oil, fuel oil; [0073] vii. mixing gaseous product stream from main fractionator with lighter stream having boiling point <300° C.; and [0074] viii. routing raw petroleum coke obtained from coke drum to feed silo, raw coke from feed silo outlet is calcined in a-kiln and routed to cooler to obtain anode grade coke.

[0075] In another embodiment of the present invention, the crude oil feed stream is separated in a ‘Pre-separator vessel’ to obtain lighter components (300° C.−) from the heavier molecules of crude oil containing 300° C.+ fraction.

[0076] In another preferred embodiment of the present invention provides a method to overcome the operational constraints of a DCU operation due to processing of crude oil. The heavy streams (300° C.+) are mixed with an aromatic rich stream such as pyrolysis tar, aromatic tar, Clarified Light Oil (CLO) etc. and routed to the Coker furnace and Coke drums subsequently.

[0077] In another embodiment of the present invention, hydrocarbon feed stock used in the process are different crude oils; sour and sweet, opportunity crudes and heavier streams generated thereof etc.

[0078] Process Conditions:

[0079] The process described herein have been carried out by maintaining the Furnace Coil Outlet Temperature in the range of 480-510° C. and the coke drum overhead temperature in the range of 430-460° C. The operating pressure maintained in the process is in the range of 1-5 Kg/cm.sup.2 (g).

Embodiment I

[0080] A schematic process flow diagram of one of the aspect of the present invention is depicted in FIG. 1, wherein part or whole of the Crude oil feedstock (1) is desalted in a desalter unit (2) to obtain desalted stream (3). The desalted stream (3) is thereafter routed to a Pre-Separator Vessel (4) to separate out stream (5) having boiling range less than 300° C. from the feed stream (3). An aromatic rich Clarified Light Oil (CLO) stream (6) is routed to the bottom of the Pre-separator vessel (4). The lighter boiling valuable fraction (300° C.−) of this CLO gets separated in pre fractionator and the fraction boiling above 300° C. mixes with 300° C.+ boiling range material of (3) and mixed feed stream (7) is obtained. The mixed feed stream (7) is fed to the furnace (8) of Delayed Coking Unit. Heated effluent stream (9) from furnace (8) is routed to either of Coke Drums (12) or (13) whichever is in filling cycle through (10) or (11). The mixed feed cracks to lighter hydrocarbons and coke inside the Coke drums. Coke drum effluent (16) is thereafter routed to the Main fractionator (17). Product streams from (17) such as gases (18) after mixing with (5) are sent for further processing. Distillate fractions light coker gas oil (20), heavy coker gas oil (21) and fuel oil (22) are sent for downstream processing. The coke (25) obtained from coke drums is sent to a feed silo (26). Thereafter, raw coke (27) from silo outlet is calcined in a kiln (28) of a calciner unit. Calcined coke (29) from kiln (28) is sent to a cooler (30) and calcined coke product (31) meeting anode grade coke specification is obtained.

Embodiment II

[0081] Another schematic process flow diagram of the present invention as depicted FIG. 2, part or whole of the Crude oil feedstock (32) is desalted in a desalter unit (33) to obtain desalted stream (34). The desalted stream (34) is thereafter routed to a Pre-Separator Vessel (35) to separate stream (36) having boiling range less than 300° C. from the feed stream (34). The 300+ boiling range stream (37) is mixed with recycle stream (38) and routed to the furnace (39) of Delayed Coking Unit. Heated effluent stream (40) from furnace (39) is routed to either of Coke Drums (43) or (44) whichever is in filling cycle through line (41) or (42). The mixed feed cracks to lighter hydrocarbons and coke inside the Coke drums. Coke drum effluent (47) is thereafter routed to the Main fractionator (49). Aromatic oil such as Clarified Light Oil stream (48) is routed to the bottom of Main fractionator (49) where it condenses heavier molecules from coke drum effluent (47) to produce recycle stream (38). Product streams from (49) such as gases (50) after mixing with (36) are sent for further processing. Distillate fractions light coker gas oil (52), heavy coker gas oil (53) and fuel oil (54) are sent for downstream processing. The coke (57) obtained from coke drums is sent to a feed silo (58). Thereafter, raw coke (59) from feed silo outlet is calcined in a kiln (60) of a calciner unit. Calcined coke from (61) is sent to a cooler (62) and calcined coke product (63) meeting anode grade coke specification is obtained.

[0082] Processing of 300+ fraction of crude oil and mixing of aromatic rich stream enhances the coke quality in comparison to that obtained from Vacuum residue feed stock.

Examples

[0083] Example 1: Crude Blend A with property provided in Table-1 was subjected to thermal cracking as per process conditions provided in Table-2 in a lab scale thermal cracker unit to obtain Raw Petroleum Coke A (RPC A). RPC obtained from the experiment was subjected to calcination in a batch calcination unit at conditions provided in Table-3 to obtain Calcined Petroleum Coke A (CPC A). CPC properties are provided in Table-4.

TABLE-US-00001 TABLE 1 Crude A property S. N Property of Crude A Value 1. Density, g/cc 0.8908 2. CCR, wt % 8.21 3. SimDist 165/210/285/358/458/582/786 5/10/30/50/70/90/95 4. Sulfur, wt % 3 5. Nitrogen, wt % 0.13 6. Metals, ppmw <1/2/<1/8/16/26 Ca/Fe/Mg/Na/Ni/V

TABLE-US-00002 TABLE 2 Operating Condition and Coke yield S. N Parameter Value 1. Operating temperature, ° C. 486 2. Pressure, Kg/cm.sup.2 (g) 1.8 3. Coke yield (Crude A), wt % 12.6

TABLE-US-00003 TABLE 3 Calcination condition S. No. Parameter Value 1. Temperature, ° C. 1250 2. Residence time, hrs 4

TABLE-US-00004 TABLE 4 Property of Crude A derived coke Anode grade S N Parameter RPC A CPC A coke spec 1. Sulfur, wt % 5 2.5 2.5-3 (max.) 2. Nitrogen, wt % 0.4 <0.1 — 3. Moisture, wt % <1 0.22 0.3 (max.) 4. Ash, wt % 0.1 0.32 0.35 (max.) 5. VMC, wt % 8.9 0.46 0.5 (max.) 6. Fixed Carbon, wt % 90.7 99.04 99 7. Real Density, g/cc — 2.06 2.05-2.085 Metal content, ppm 8. Ni 127 152 200 (max.) 9. V 207 247 250 (max.) 10. Ni + V 334 399 350-450 (max.) 11. Na 64 159 100-300 (max.) 12. Ca 8 16 100-200 (max.) 13. Na + Ca 72 175 200 (max.) 14. Fe 16 18 200-600 (max.)

[0084] Coke as described in Table 4 was subjected to XRD analysis for measurement of Crystallite Size (Lc). Lc value was observed to be 37 Å, indicating a good quality crystalline structure. It can be observed that all properties of crude derived CPC A fall in the range of anode grade coke.

[0085] Example 2: Crude A described in Table-1 was subjected to Atmospheric Distillation followed by Vacuum Distillation to generate Vacuum Residue (VR) which is a typical Coker feed stock (Table-5). VR was subjected to thermal cracking in a thermal cracker unit as per process conditions described in Table-6 to obtain Raw Petroleum Coke B (RPC B). RPC B thus obtained was subjected to calcination in a batch scale calcination unit as per conditions in Table-7 to generate Calcined Petroleum Coke B (CPC B). Property of coke thus obtained is provided in Table-8

TABLE-US-00005 TABLE 5 Property of Vacuum Residue feed stock from crude A S. N Property Value 1. Density, g/cc 1.0551 2. CCR, wt % 28 3. SimDist 564/581/624/670/729/823/973 5/10/30/50/70/90/95 4. Sulfur, wt % 6 5. Nitrogen, wt % 0.4 6. Metals, ppmw 1/10/<1/49/57/170 Ca/Fe/Mg/Na/Ni/V

TABLE-US-00006 TABLE 6 Operating Condition and Coke yield S. N Parameter Value 1. Operating temperature, ° C. 486 2. Pressure, Kg/cm.sup.2 (g) 1.8 3. Coke yield (VR), wt % 30

TABLE-US-00007 TABLE 7 Calcination condition S. No. Parameter Value 1. Temperature, ° C. 1250 2. Residence time, hrs 4

TABLE-US-00008 TABLE 8 Coke generated from VR of Crude A Anode grade S N Parameter RPC B CPC B coke spec 1. Sulfur, wt % 8 3.4 2.5-3 (max.) 2. Nitrogen, wt % 1.4 0.9 — 3. Moisture, wt % <1 0.22 0.3 (max.) 4. Ash, wt % 0.12 0.4 0.35 (max.) 5. VMC, wt % 9.38 3.95 0.5 (max.) 6. Fixed Carbon, wt % 90.19 95.47 99 7. Real Density, g/cc — 2.05 2.06-2.08 Metal content, ppm 8. Ni 190 254 200 (max.) 9. V 567 769 250 (max.) 10. Ni + V 757 1023 350-450 (max.) 11. Na 163 320 100-300 (max.) 12. Ca 4 7 100-200 (max.) 13. Na + Ca 167 327 200 (max.) 14. Fe 33 38 200-600 (max.)
CPC B as described in Example-2 was subjected to XRD analysis for measurement of Crystallite size (Lc). Lc was observed to be 34.7 Å which is lower than that of CPC A, indicating a lesser evolved crystalline structure. Also, metals such as Vanadium, Nickel and Sodium were concentrated in coke leading to poor quality of coke. Impurities such as sulphur and Nitrogen content were also found to be high in RPC & CPC B generated from VR.

[0086] Example 3: In another experiment, aromatic stream of Clarified Light Oil (CLO) having property as provided in Table-9 was mixed with crude oil feed stock in a ratio of 10:90 and processed in a laboratory scale thermal cracking unit as per process conditions mentioned in Table-10 to obtain Raw Petroleum Coke C (RPC C). RPC C generated thereof was subjected to calcination as per conditions provided in Table-11 to obtain Calcined Petroleum Coke C (CPC C). Calcined coke obtained had property provided in Table-12.

TABLE-US-00009 TABLE 9 Property of CLO S. N Property Value 1. Density, g/cc 1.1 2. CCR, wt % 15.9 3. SimDist 219/320/360/386/422/478/524 5/10/30/50/70/90/95 4. Sulfur, wt % 0.4 5. Nitrogen, wt % 0.04 6. Metals, ppmw <1/<1/<1/<1/<1/<1 Ca/Fe/Mg/Na/Ni/V

TABLE-US-00010 TABLE 10 Operating condition S. N Parameter Value 1. Operating temperature, ° C. 486 2. Pressure, Kg/cm.sup.2 (g) 1.8 3. Coke yield, wt % 20

TABLE-US-00011 TABLE 11 Calcination condition S. No. Parameter Value 1. Temperature, ° C. 1250 2. Residence time, hrs 4

TABLE-US-00012 TABLE 12 Coke generated from Crude A and CLO Anode grade S N Parameter RPC C CPC C coke spec 1. Sulfur, wt % 4.7 2.3 2.5-3 (max.) 2. Nitrogen, wt % 0.39 <1 — 2. Moisture, wt % 0.51 0.08 0.3 (max.) 3. Ash, wt % 0.12 0.38 0.35 (max.) 4. VMC, wt % 3.74 0.48 0.5 (max.) 5. Fixed Carbon, wt % 95.63 99.06 99 6. Real Density, g/cc — 2.07 2.06-2.08 Metal content, ppm 8. Ni 116 138 200 (max.) 9. V 187 223 250 (max.) 10. Ni + V 303 361 350-450 (max.) 11. Na 65 163 100-300 (max.) 12. Ca 18 36 100-200 (max.) 13. Na + Ca 83 199 200 (max.) 14. Fe 42 48 200-600 (max.)

[0087] Calcined coke as described in Example-3 was subjected to XRD analysis for measurement of Crystallite size (Lc). Lc was observed to be ˜38 Å indicating an improvement in coke quality.

Advantages of the Present Invention

[0088] 1. No hydrogen requirement as it does not involve hydrotreatment of residues. [0089] 2. Solvent deasphalting of residues is not required and therefore more economical as there is no additional cost with respect to solvents involved. [0090] 3. Current invention is easy to implement with existing as well as grass root units. [0091] 4. Separation of lighter fraction (300° C.−) of CLO in the pre-separator thereby recovering valuable lighter boiling fractions while producing Anode grade coke [0092] 5. Production of superior quality coke meeting anode grade specification