Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
  • C10B57/045—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition containing mineral oils, bitumen, tar or the like or mixtures thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B39/00—Cooling or quenching coke
  • C10B39/04—Wet quenching
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material
  • C10B55/02—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material with solid materials
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/005—After-treatment of coke, e.g. calcination desulfurization
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/14—Features of low-temperature carbonising processes

Definitions

• the present disclosure relates to a process for the production of needle coke.
• Hydrotreating refers to a number of different processes that involve treatment of crude oil fractions with hydrogen. These processes can be grouped in two sub-classifications, viz- “hydropurification” and “hydroconversion”.
• the “hydropurification” includes the treatment processes such as hydrodesulfurization, hydrodenitrogenation, hydrodeoxygenation, hydrodemetallization and the like.
• the “hydroconversion”, involves the processes such as hydrogenation, hydrodearomatization, isomerization, hydrocracking and the like.
• Needle coke refers to a specialty grade of petroleum coke valued for its crystalline structure that makes it a suitable material for making graphite electrodes.
• CTE Coefficient of thermal expansion
• CCR Conradson carbon residue
• Superheated steam refers to a steam at a temperature higher than its vaporization point at the absolute pressure where the temperature is measured.
• Delayed coker furnace refers to a type of coker whose process consists of heating a residual oil feed to its thermal cracking temperature in a furnace.
• Coker or coker unit refers to an oil refinery processing unit that converts the residual oil from the vacuum distillation column into low molecular weight hydrocarbon gases, naphtha, light and heavy gas oils, and petroleum coke.
• Needle coke is the highest value petroleum coke used for manufacturing graphite electrode for arc furnaces. As most of the steel manufacturers are switching to electric arc furnace (EAF) for production of steel, demand of premium needle coke making graphite electrodes for EAF is also increasing. Needle coke is also used to make synthetic spherical graphite for lithium ion battery anodes.
• EAF electric arc furnace
• Graphite electrodes are used under harsh conditions, such as in high-temperature atmospheres, and therefore, it is desired that they have low thermal expansion coefficients (CTE).
• CTE thermal expansion coefficients
• a lower thermal expansion coefficient reduces electrode wear during electric steelmaking, and can reduce costs in the steelmaking process. Therefore, fine control of the thermal expansion coefficient (CTE) of the needle coke is desirable.
• the delayed coker unit used for production of needle coke, operates on a partially batch and partially continuous process.
• a furnace and fractionator are operated in a continuous mode whereas the coke drums are operated in a batch mode. Every time a coke drum is filled with coke, it is taken offline for coke removal while a second coke drum is taken online for the coking cycle in the delayed coker unit.
• feed having all the desirable properties it is difficult to produce premium needle coke in the coke drum and only a fraction of the coke produced in the coke drum meets the quality of premium needle coke.
• the feed required to produce good quality needle coke is required to have very less amount of sulfur, nitrogen, asphaltenes and inorganic impurities.
• the sulfur, the nitrogen and the polyaromatics can be reduced in the feed charged into the coking drum through conventional processes such as hydrotreating.
• the hydrotreating processes include hydrodesulfurization, hydrodenitrification and hydrodearomatization.
• Conventional processes involve maximizing the recycle of the heavy hydrocarbon fraction produced during the delayed coking operation of the needle coke to maximize yield of the needle coke. Wide range of recycle of the heavy fraction coker distillate and mixing this recycled distillate with the fresh feed are known.
• inorganic additives such as fine chromium oxide, iron oxide, calcium fluoride powder and the like can be added in the coke feed to reduce the coefficient of thermal expansion (CTE) of the needle coke produced.
• CTE coefficient of thermal expansion
• addition of these inorganic additives increase the ash content of needle coke, which has maximum limit of 0.3 wt.% ash.
• the conventional processes for the manufacturing of the needle coke require hydrotreating/hydrogenation of either the fresh feed or the recyclable distillate.
• This increases the CAPEX/OPEX of the process and requires the commercial units capable of operating at high pressure and high temperature.
• the hydrotreating of the heavy petroleum fraction is a challenging process.
• Another disadvantage of hydrotreating is that there is always a significant loss of feed material because of the formation of lighter components during hydrotreatment.
• the catalyst used in the hydrotreatment is required to be frequently changed or regenerated as the heavy components of the hydrotreated stream cause exhaustion and poisoning of the catalyst.
• It is an object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
• An object of the present disclosure is to provide a process for the production of needle coke. Another object of the present disclosure is to provide a process for the production of needle coke without hydrotreatment.
• Still another object of the present disclosure is to provide a process for the production of needle coke having low sulfur content and low CTE.
• Yet another object of the present disclosure is to provide a simple, efficient and cost effective process for the production of needle coke.
• the present disclosure relates to a process for the production of needle coke.
• the process comprises mixing a predetermined amount of a first feed and a second feed in a fractionator and simultaneously heating the fractionator to obtain a blend having a first predetermined temperature.
• the blend is passed to a delayed coker furnace and the furnace is heated to a second predetermined temperature to obtain a heated coker feed.
• the heated coker feed is passed to a coke drum at a third predetermined temperature and at a predetermined pressure, and maintained it at the third predetermined temperature and the predetermined pressure for a first predetermined time period to obtain coke and a distillate.
• the coke is separated by allowing the distillate to exit from a top of the coke drum to the fractionator to obtain a separated coke in the coke drum.
• the separated coke in the coke drum is treated with a superheated steam for a second predetermined time period to obtain a treated coke.
• the treated coke is quenched with water to obtain the needle coke.
• Figure 1 illustrates a flow diagram of the process for the production of needle coke in accordance with an embodiment of the present disclosure
• Figure 2 illustrates a graph representing the effect of an unhydrotreated second feed on the sulfur content of the needle coke, wherein the needle coke is produced by using a first clarified slurry oil (CSO-1) in accordance with the present disclosure
• CSO-1 first clarified slurry oil
• Figure 3 illustrates a graph representing the effect of unhydrotreated second feed on the coefficient of thermal expansion (CTE) of the needle coke, wherein the needle coke is produced by using a first clarified slurry oil (CSO-1) in accordance with the present disclosure
• Figure 4 illustrates a graph representing the effect of unhydrotreated second feed on the percentage of coke bed with CTE ⁇ 1.2 x 10’ 6 /°C of the needle coke, wherein the needle coke is produced by using a first clarified slurry oil (CSO-1) in accordance with the present disclosure.
• CSO-1 first clarified slurry oil
• Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
• first, second, third, etc. should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
• Needle coke is the highest value petroleum coke used for manufacturing graphite electrode for arc furnaces. As most of the steel manufacturers are switching to electric arc furnace (EAF) for production of steel, demand of premium needle coke making graphite electrodes for EAF is also increasing. Needle coke is also used to make synthetic spherical graphite for lithium ion battery anodes.
• EAF electric arc furnace
• Graphite electrodes are used under harsh conditions, such as in high-temperature atmospheres, and therefore, it is desired that they have low thermal expansion coefficients (CTE).
• CTE thermal expansion coefficients
• a lower thermal expansion coefficient reduces electrode wear during electric steelmaking, and can reduce costs in the steelmaking process. Therefore, fine control of the thermal expansion coefficient (CTE) of the needle coke is desirable.
• the delayed coker unit used for production of needle coke, operates on a partially batch and partially continuous process.
• a furnace and fractionator are operated in a continuous mode whereas the coke drums are operated in a batch mode. Every time a coke drum is filled with coke, it is taken offline for coke removal while a second coke drum is taken online for the coking cycle in the delayed coker unit.
• feed having all the desirable properties it is difficult to produce premium needle coke in the coke drum and only a fraction of the coke produced in the coke drum meets the quality of premium needle coke.
• the feed required to produce good quality needle coke is required to have very less amount of sulfur and low amounts of nitrogen, asphaltenes and inorganic impurities.
• the sulfur, the nitrogen and the polyaromatics can be reduced in the feed charged into the coking drum through conventional processes such as hydrotreating.
• the hydrotreating processes include hydrodesulfurization, hydrodenitrification and hydrodearomatization.
• inorganic additives such as fine chromium oxide, iron oxide, calcium fluoride powder and the like can be added in the coke feed to reduce the coefficient of thermal expansion (CTE) of the needle coke produced.
• CTE coefficient of thermal expansion
• addition of these inorganic additives increase the ash content of needle coke, which has a limit of 0.3 wt% ash.
• the conventional processes for the manufacturing of the needle coke require hydrotreating/hydrogenation of either the fresh feed or the recyclable distillate.
• This increases the CAPEX/OPEX of the process and requires the commercial units capable of operating at high pressure and high temperature.
• the hydrotreating of the heavy petroleum fraction is a challenging process.
• Another disadvantage of hydrotreating is that there is always a significant loss of feed material because of the formation of lighter components during hydrotreatment.
• the catalyst used in the hydrotreatment is required to be frequently changed or regenerated as the heavy components of the hydrotreated stream cause exhaustion and poisoning of the catalyst.
• the present disclosure provides a process for the production of needle coke.
• the process comprising the following steps:
• a predetermined amount of a first feed and a second feed are mixed in a fractionator and simultaneously heating the fractionator to obtain a blend having a first predetermined temperature.
• the first feed is at least one selected from the group consisting of first clarified slurry oil (CSO-1), second clarified slurry oil (CSO-2), and vacuum gas oil (VGO).
• the first feed is a first clarified slurry oil (CSO-1).
• the first feed is a second clarified slurry oil (CSO-2).
• the first feed is a mixture of second clarified slurry oil (CSO-2) and vacuum gas oil (VGO).
• a mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) is in the range of 4:1 to 10:1. In an exemplary embodiment, the mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) is 9:1. In another exemplary embodiment, the mass ratio of second clarified slurry oil (CSO-2) to vacuum gas oil (VGO) is 5.3:1.
• the first clarified slurry oil (CSO-1) is characterized by having a sulfur content in the range of 0.8 mass% to 1.5 mass% with respect to the total mass of the blend; a Conradson Carbon Residue (CCR) in the range of 3 mass% to 8 mass% with respect to the total mass of the blend; an ash content in the range of 0.01 mass % to 0.15 mass% with respect to the total mass of the blend; a density is in the range of 0.5 g/cc to 1.5 g/cc; an asphaltene content ⁇ 5 mass% with respect to the total mass of the blend; and a boiling temperature is in the range of 190 °C to 700 °C.
• CCR Conradson Carbon Residue
• the first clarified slurry oil (CSO-1) is characterized by having the sulfur content 1.26 mass% with respect to the total mass of the blend; the CCR of 6.6 mass% with respect to the total mass of the blend; the ash content of 0.08% with respect to the total mass of the blend; the density of 1.063 g/cc; the asphaltene content is ⁇ 5 mass% with respect to the total mass of the blend; and the boiling temperature is in the range of 197 °C to 700 °C.
• the second clarified slurry oil is characterized by having a sulfur content in the range of 0.2 mass% to 0.8 mass% with respect to the total mass of the blend; a Conradson Carbon Residue (CCR) in the range of 8 mass% to 15 mass% with respect to the total mass of the blend; an ash content in the range of 0.01 % to 0.1 mass% with respect to the total mass of the blend; a density is in the range of 0.5 g/cc to 1.5 g/cc; an asphaltene content ⁇ 5 mass% with respect to the total mass of the blend; and a boiling temperature is in the range of 245 °C to 690 °C.
• CCR Conradson Carbon Residue
• the second clarified slurry oil is characterized by having the sulfur content 0.57 mass% with respect to the total mass of the blend; the CCR of 10.3 mass% with respect to the total mass of the blend; the ash content of 0.05% with respect to the total mass of the blend; the density of 1.084 g/cc; the asphaltene content is ⁇ 5 mass% with respect to the total mass of the blend; and the boiling temperature is in the range of 250 °C to 683 °C.
• the clarified slurry oil is obtained from the bottom of fluid catalytic cracking (FCC).
• the vacuum gas oil is characterized by having a sulfur content in the range of 0.08 mass% to 0.15 mass% with respect to the total mass of the blend; a Conradson Carbon Residue (CCR) in the range of 0.05 mass% to 0.5 mass% with respect to the total mass of the blend; an ash content in the range of 0 to 0.15 mass% with respect to the total mass of the blend; a density is in the range of 0.5 g/cc to 1.5 g/cc; an asphaltene content ⁇ 5 mass% with respect to the total mass of the blend; and a boiling temperature is in the range of 280 °C to 600 °C.
• CCR Conradson Carbon Residue
• the vacuum gas oil is characterized by having the sulfur content 0.12 mass% with respect to the total mass of the blend; the CCR of 0.1 mass% with respect to the total mass of the blend; the ash content of 0 % with respect to the total mass of the blend; the density of 0.906 g/cc; the asphaltene content is ⁇ 5 mass% with respect to the total mass of the blend; and the boiling temperature is in the range of 284 °C to 594 °C.
• the vacuum gas oil (VGO) is obtained from VGO hydrotreating process (VGOHT).
• the first feed is hydrotreated or partially hydrotreated or unhydrotreated.
• the second feed is a heavy recycle stream selected from heavy coker oil gas (HCGO), heavy coker distillate and heavy hydrocarbon stream.
• the second feed is heavy coker oil gas (HCGO).
• the second feed in heavy coker distillate.
• the second feed has a boiling temperature in the range of 300 °C to 600 °C.
• the first feed and the second feed are not hydrogenated.
• the first feed i.e., clarified slurry oil (CSO-1), clarified slurry oil (CSO-2), and second feed i.e., heavy coker gas oil (HCGO) are not hydrogenated.
• the predetermined amount of the second feed is in the range of 25 mass% to 40 mass% with respect to the total mass of the first feed. In an exemplary embodiment, the predetermined amount of the second feed is 30 mass% with respect to the total mass of the first feed. In another exemplary embodiment, the predetermined amount of the second feed is 25 mass% with respect to the total mass of the first feed. In still another exemplary embodiment, the predetermined amount of the second feed is 50 mass% with respect to the total mass of the first feed. In yet another exemplary embodiment, the predetermined amount of the second feed is 43 mass% with respect to the total mass of the first feed. In accordance with the present disclosure, the first feed and the second feed are pre-heated to a temperature in the range of 150 °C to 250 °C prior to mixing in the fractionator in the step -
• the first predetermined temperature is in the range of 300 °C to 400 °C. In an embodiment, the first predetermined temperature is in the range of 325 °C to 350 °C. In the exemplary embodiments, the first predetermined temperature is 330 °C.
• the amount of the second feed is inversely proportional to the sulfur content of the first feed i.e., the lower is the sulfur content in the first feed, greater will be the amount of the recyclable stream (second feed) that can be combined with the first feed.
• the amount of the second feed is inversely proportional to the density of the first feed i.e., the lower is the density of the first feed, the greater will be the amount of the recyclable stream (second feed) that can be combined with the first feed.
• the blend is passed to a delayed coker furnace and the furnace is heated to a second predetermined temperature to obtain a heated coker feed.
• the second predetermined temperature is in the range of 400 °C to 600 °C. In an embodiment, the second predetermined temperature is in the range of 480 °C to 515 °C. In the exemplary embodiments, the second predetermined temperature is 498 °C.
• the heated coker feed is passed to a coke drum at a third predetermined temperature and at a predetermined pressure, and maintained it at the third predetermined temperature and the predetermined pressure for a first predetermined time period to obtain coke and a distillate.
• the third predetermined temperature is in the range of 400 °C to 600 °C. In an embodiment, the third predetermined temperature is in the range of 425 °C to 500 °C. In an exemplary embodiment, the third predetermined temperature is 440 °C. In another exemplary embodiment, the third predetermined temperature is 485 °C.
• the third predetermined temperature can be 10 °C to 20 °C lower than the second predetermined temperature due to heat loss in transfer from furnace to coke drum.
• the predetermined pressure is in the range of 2 kg/cm 2 (g) to 10 kg/cm 2 (g). In an embodiment, the predetermined pressure is in the range of 2.5 kg/cm (g) to 6 kg/cm (g). In an exemplary embodiment, the predetermined pressure is 3 kg/cm (g). In another exemplary embodiment, the predetermined pressure is 3.5 kg/cm (g).
• the first predetermined time period is in the range of 15 hours to 50 hours. In an embodiment, the first predetermined time period is in the range of 18 hours to 36 hours. In an exemplary embodiment, the first predetermined time period is 24 hours. In another exemplary embodiment, the first predetermined time period is 20.5 hours. In still another exemplary embodiment, the first predetermined time period is 30 hours.
• the coke is separated by allowing the distillate to exit from a top of the coke drum to the fractionator to obtain a separated coke in the coke drum.
• the coke drum is filled up to 70% with the separated coke.
• the separated coke in the coke drum is treated with superheated steam for a second predetermined time period to obtain a treated coke.
• the superheated steam has a temperature in the range of 300 °C to 500 °C. In the exemplary embodiments, the superheated steam has the temperature of 485 °C.
• the superheated steam has a pressure in the range of 2.5 kg/cm (g) to 10 kg/cm (g). In an exemplary embodiment, the superheated steam has the pressure of 3 kg/cm (g). In another exemplary embodiment, the superheated steam has the pressure of 3.5 kg/cm (g).
• the second predetermined time period is in the range of 1 hour to 30 hours. In an exemplary embodiment, the second predetermined time period is 4 hours. In another exemplary embodiment, the second predetermined time period is 24 hours.
• the treated coke is quenched with water obtain the needle coke.
• the treated coke is quenched with water in the coke drum.
• the coke is then cut with coke cutting tool using high pressure water jet.
• the needle coke is segregated based on coke quality.
• the needle coke is then stored in designated silos.
• the yield of needle coke depends on the CCR of the blend that is charged to the coking chamber/drum i.e. the greater is the CCR of the blend, the higher is the yield of the needle coke. It has been identified that hydrotreating the distillate reduces the CCR not only of the distillate but also of the blend that is charged. Therefore, if the distillate is hydrotreated, although good quality needle coke may be produced, but at lower yields.
• the process of the present disclosure produces the needle coke having low sulfur content and low CTE without the need of hydrotreatment of the heavy coker distillate. Therefore, the process of the present disclosure eliminates the hydrotreatment of the heavy coker distillate and hence, reduces the CAPEX/OPEX.
• the process of the present disclosure is efficient and cost effective.
• the needle coke of the present disclosure has a low sulfur content and a low CTE.
• the needle coke of the present disclosure is a high quality petroleum coke having sulfur ⁇ 0.5 mass%, ash content ⁇ 0.2 mass%, Coefficient of thermal expansion (CTE) ⁇ 1.2 x 10’ 6 /°C, and real density > 2.13g/cc.
• a first feed is prepared by mixing desired amount of unhydrotreated CSO and hydrotreated-VGO to meet feed specification of sulfur, ash and aromatic content.
• the heat from hot coker products of the fractionator is exchanged with the first feed and passed to a fractionator bottom.
• a predetermined amount of a second feed (hot heavy coker gas oil (HCGO)) is mixed with the first feed in the fractionator bottom and heated to obtain a blend having temperature in the range of 325 °C to 350 °C.
• the blend is passed to a delayed coker furnace and heated to a temperature of 480 °C to 515 °C) before routing to coke drum bottom operated at 3 to 6 kg/cm 2 (g) coke drum top pressure.
• a sufficient time (20 to 36 hours) is allowed in a coke drum to convert coker feed to needle coke and distillates.
• the coke distillates from coke drum top is routed to the fractionator.
• the feed is switched over to 2 nd coke drum once the 1 st coke drum is filled with coke.
• the filled coke drum is steamed with superheated steam.
• the coke drum is quenched with water.
• the coke is cut with coke cutting tool using high pressure water jet.
• the needle coke is segregated based on coke quality.
• the needle coke is stored in designated silos.
• Coker pilot plant of 1 barrel/day capacity was used for the experimental study.
• the coker pilot plant was equipped with feed vessels, feed pump, recycle pump, electric furnace, coke drum, fractionator and product vessels.
• the feed properties and experimental conditions used for the experiments are tabulated in tables 1 and 2, respectively.
• ⁇ CSO-1 First Clarified Slurry Oil
• CSO-2 Second Clarified Slurry Oil
• VGO Vacuum Gas Oil (VGO)
• Example -1 there was no recycle of unhydrotreated heavy coker fraction (second feed)
• Example -2 there was 30.2% recycle of unhydrotreated heavy coker fraction (second feed)
• Example -3 there was 51.2% recycle of unhydrotreated heavy coker fraction (second feed) on first feed basis.
• Table 5 illustrates zone- wise needle coke quality at different throughput ratios with CSO-1.
• Table 5 Zone-wise needle coke quality at different throughput ratios with CSO-1
• Example 4 there was only first feed (CSO-2) without recycle
• Example 5 there was first feed (CSO-2) recycled with 43.1% second feed (heavy coker distillate) on fresh feed basis
• Example 6 there was a mixed first feed (i.e. 84.2% CSO-2 and 15.8% VGO) without recycle
• Example-7 there was a mixed first feed (z.e. 90% CSO-2 and 10% VGO) recycled with 24.6% second feed (heavy coker distillate) on first feed basis.
• Table 6 illustrates the quality of needle coke of the entire coke drum with CSO-2 and VGO.
• Example 5 In comparison to the processing of only CSO-2 without recycle (example -4), 43% unhydrotreated recycle (Example-5) has given needle coke with higher CTE as well higher sulfur.
• Example-6 In case of a mixture of CSO-2 and VGO (Example-6), although the sulphur content has reduced significantly in comparison to Example-4, very small improvement in overall CTE of entire coke bed was observed. Whereas, with 24% unhydrotreated recycle (Example-7) along with CSO-2 and VGO as first feed, a significant improvement in CTE was observed and the sulfur was also slightly lower than example-4. Therefore, optimum amount of unhydrotreated recycle stream (second feed) was required to get good quality needle in higher yield.
• Table 7 illustrates zone-wise needle coke quality at different throughput ratios of CSO-2 and VGO.
• Table 7 Zone-wise needle coke quality at different throughput ratios of CSO-2 and VGO
• the needle coke so obtained was further calcined to produce calcined needle coke which can be used as raw material for graphite electrodes.

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