Needle coke production process
A novel needle coke production process using non-hydrotreated oils and optimized processing conditions addresses the challenges of conventional methods, achieving low sulfur and thermal expansion in high-quality coke production without hydrotreating, thus reducing costs and improving efficiency.
Patent Information
- Application Number
- JP2024537514
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-01-03
- Filing Date
- 2022-12-29
- Publication Date
- 2024-12-16
AI Technical Summary
Conventional needle coke production processes face challenges in producing high-grade coke due to the need for hydrotreating, which increases capital and operational expenses, and the addition of inorganic additives raises ash content, while recycling untreated distillates affects quality and requires costly hydroprocessing.
A process involving mixing non-hydrotreated clarified slurry oils and vacuum gas oil, heating, and processing in a delayed coker furnace, followed by steam treatment and cooling to produce needle coke without hydrotreating, optimizing raw material ratios and processing conditions to achieve low sulfur and thermal expansion coefficients.
The process efficiently produces high-quality needle coke with low sulfur and thermal expansion, reducing capital and operational costs by eliminating hydrotreating and maximizing yield, while maintaining coke quality.
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Abstract
Description
[Technical field]
[0001] FIELD OF THEINVENTION The present invention relates to a process for producing needle coke.
[0002] Definition of Terms As used herein, the following terms are generally intended to have the following definitions, unless the context indicates otherwise. Hydroprocessing refers to a number of different processes that treat crude oil fractions with hydrogen. These processes are grouped into two subcategories: "hydrofinishing" and "hydroconversion". "Hydrotrefining" includes hydrodesulfurization, hydronitriding, hydrodeoxygenation, hydrodemetallization, and similar processes. "Hydrotrefining" refers to hydrogenation, hydrodearomatization, isomerization, hydrocracking, and similar processes. Needle coke refers to a special grade of petroleum coke valued for its crystalline structure that makes it a suitable material for making graphite electrodes. The coefficient of thermal expansion (CTE) is a measure of the expansion or contraction of a material with a change in temperature. Conradson Carbon Residue (CCR), commonly known as "ConCarbon" or "CCR", is a laboratory test that measures the tendency of petroleum to form coke. Quantitatively, the test measures the amount of carbonaceous residue left after the evaporation and pyrolysis of petroleum. Superheated steam refers to steam that has reached a temperature above its vaporization point at the absolute pressure at which the temperature measurement is made. A delayed coker furnace is a coker whose process involves heating residual oil feedstock to a temperature where it pyrolyzes in the furnace. A coker or coker unit refers to a refinery processing unit that converts residual oil from the vacuum distillation column into lower molecular weight hydrocarbon gases, naphtha, heavy gas oil, and petroleum coke. [Background technology]
[0003] Background of the invention technology The following background information is relevant to the present invention but is not necessarily prior art. Needle coke, named for its needle-like crystalline structure, is the highest value petroleum coke used to manufacture graphite electrodes for electric arc furnaces. As almost all steel manufacturers are switching to electric arc furnaces (EAFs) for steel production, the demand for high-grade needle coke to manufacture graphite electrodes for EAFs is also increasing. Needle coke is also used to manufacture synthetic spheroidal graphite for lithium-ion battery anodes. Graphite electrodes are used under harsh conditions such as high temperature atmospheres. For this reason, a low coefficient of thermal expansion (CTE) is desirable. A low coefficient of thermal expansion allows electrodes to reduce electrode wear during steel production in electric furnaces, which can reduce steel production costs. Therefore, fine-tuning the coefficient of thermal expansion (CTE) of needle coke is desirable.
[0004] The production of needle coke is both an art and a science. The delayed coker units used in the production of needle coke are operated partly in batch mode and partly in continuous processes. In the needle coke production process, the furnaces and fractionators are operated in continuous mode, while the coke drum is operated in batch mode. Each time coke is charged into a coke drum, the drum is taken off-line to unload the coke, and a second coke drum is brought on-line for a coking cycle in the delayed coker unit. Even with raw materials with desirable physical properties, it is difficult to produce high-grade needle coke in the coke drum, and only a fraction of the coke produced in the coke drum meets the quality of high-grade needle coke. The feedstock required for the production of high quality needle coke is very low in sulfur, nitrogen, asphaltene and inorganic impurities. Traditional methods such as hydrotreating can reduce the sulfur, nitrogen and polyaromatics in the feedstock entering the coking drum. Hydrotreating processes include hydrodesulfurization, hydronitriding and hydrodearomatization. Conventional processes involve maximizing the recycle of the heavy hydrocarbon fraction produced during the delayed coking process of needle coke to maximize needle coke yield. Extensive recycle of the heavy coker distillate and blending of this recycle distillate with fresh feed is known. However, this recycle requires catalytic hydrotreating of the distillate fraction at temperatures between 315°C and 400°C, pressures between 350 psi and 2000 psi, and liquid hourly space velocities (LHSV) between 0.2 and 3. Untreated distillate affects needle coke quality. It is known that as the heavy recycle fraction increases, the quality of the needle coke is affected.
[0005] Additionally, inorganic additives such as finely powdered chromium oxide, iron oxide, calcium fluoride, and similar compounds can be added to the coke feedstock to reduce the coefficient of thermal expansion (CTE) of the resulting needle coke, but the addition of these inorganic additives increases the ash content of the needle coke, which has a maximum limit of 0.3 wt.% ash. Therefore, the conventional process for producing needle coke requires hydrotreating / hydrogenation of virgin feedstock or recyclable distillates. This increases the CAPEX / OPEX of the process and requires commercial units capable of operating under high pressure and high temperature. Hydrotreating of heavy petroleum fractions is a costly process. Another disadvantage of hydrotreating is that the hydrotreating process inevitably incurs a large amount of feedstock loss due to the production of light components. Furthermore, the catalysts used in hydrotreating require frequent replacement or regeneration as the heavy components in the hydrotreating stream fatigue and foul the catalyst. Thus, there is a recognized need for the development of a needle coke production process that should avoid the above-mentioned disadvantages or at least provide a useful alternative.
[0006] Object of the invention Some of the objects of the present invention, of which at least one embodiment is sufficient to be mentioned herein, are as follows. It is an object of the present invention to ameliorate one or more of the problems in the prior art, or at least to provide a useful alternative. An object of the present invention is to provide a process for producing needle coke. Another object of the present invention is to provide a process for producing needle coke without hydrotreating. It is a further object of the present invention to provide a process for producing needle coke having both low sulfur content and low CTE. It is a further object of the present invention to provide a simple, efficient and cost-effective process for producing needle coke. Other objects and advantages of the present invention will become more apparent from the following disclosure, which is not intended to limit the scope of the invention thereto. Summary of the Invention [Problem to be solved by the invention]
[0007] Summary of the Invention The present invention relates to a process for producing needle coke. The process comprises mixing a first feedstock and a second feedstock in a fractionator and heating the fractionator on the same day to a first predetermined temperature to obtain a mixture. The mixture is fed into a delayed coker furnace, which is heated to a second predetermined temperature to obtain a heated coker feedstock. The heated coker feedstock is fed into a coke drum at a predetermined pressure and a third predetermined temperature and maintained at the third predetermined temperature and pressure for a first predetermined time period to obtain coke and a distillate. The coke is separated with the distillate exiting the top of the coke drum into a fractionator to obtain a separate coke in the coke drum. The separated coke in the coke drum is treated with superheated steam for a second predetermined time period to obtain a treated coke. The treated coke is cooled with water to obtain needle coke. [Brief description of the drawings]
[0008] The invention will now be explained with the aid of the accompanying drawings, in which: [Figure 1] FIG. 1 illustrates a flow chart of a needle coke production process according to the present invention. [Diagram 2] FIG. 2 is a graphical illustration showing the effect of non-hydrotreated second feedstock on sulfur content in needle coke, where the needle coke is produced using a first clarified slurry oil (CSO-1) according to the present invention. [Diagram 3] FIG. 3 illustrates a graph showing the effect of non-hydrotreated second feedstock on needle coke coefficient of thermal expansion (CTE), where needle coke is produced using a first clarified slurry oil (CSO-1) according to the present invention. [Figure 4] FIG. 4 illustrates a graph showing the effect of non-hydrotreated second feedstock on needle coke CTE <1.2×10 / ° C., where the needle coke is produced using a first clarified slurry oil (CSO-1) according to the present invention.
[0009] Detailed Description of the Invention An embodiment of the present invention will now be described with reference to the accompanying drawings. The embodiments described herein can allow a person skilled in the art to fully and completely grasp the scope of the present invention. A number of details related to individual components can be described to fully grasp the embodiments of the present invention. It is obvious to a person skilled in the art that the details described in the embodiments cannot be interpreted as limiting the scope of the present invention. In some embodiments, well-known processes, well-known device structures, and well-known techniques are not described in detail.
[0010] In the present invention, the terms described are used only to describe specific embodiments and should not be construed as limiting the scope of the present invention. Nouns used in the present invention include plurals unless the context dictates that they should be treated as singular. Terms such as "comprises," "includes," "comprises," and "consists of" are inclusive transitional terms and thus define the presence of features, integers, steps, operations, elements, modules, units, or components described herein, but do not exclude the presence or addition of other features, integers, steps, operations, elements, components, or groups of components. The particular sequence of steps disclosed in the methods and processes of the present invention should not be construed as necessarily indicating that the performance described or illustrated is essential. It should also be understood that additional or alternative steps may be used.
[0011] As used herein, the term "or" includes any combination of one or more of the associated listed members. The terms first, second, third, etc. may be used only to distinguish one element or component, region, layer or section from another component, region, layer or section, and therefore should not be construed as limiting the scope of the present invention. The terms first, second, third, etc. do not imply a particular order or sequence, unless expressly indicated in the present invention. Needle coke, named for its needle-like crystalline structure, is the highest value petroleum coke used to manufacture graphite electrodes for electric arc furnaces. As almost all steel manufacturers are switching to electric arc furnaces (EAFs) for steel production, the demand for high-grade needle coke to manufacture graphite electrodes for EAFs is also increasing. Needle coke is also used to manufacture synthetic spheroidal graphite for lithium-ion battery anodes.
[0012] Graphite electrodes are used under harsh conditions such as high temperature atmospheres. For this reason, a low coefficient of thermal expansion (CTE) is desirable. A low coefficient of thermal expansion allows electrodes to reduce electrode wear during steel production in electric furnaces, which can reduce steel production costs. Therefore, fine-tuning the coefficient of thermal expansion (CTE) of needle coke is desirable. The production of needle coke is both an art and a science. The delayed coker units used in the production of needle coke are operated partly in batch mode and partly in continuous processes. In the needle coke production process, the furnaces and fractionators are operated in continuous mode, while the coke drum is operated in batch mode. Each time coke is charged into a coke drum, the drum is taken off-line to unload the coke, and a second coke drum is brought on-line for a coking cycle in the delayed coker unit. Even with raw materials with desirable physical properties, it is difficult to produce high-grade needle coke in the coke drum, and only a fraction of the coke produced in the coke drum meets the quality of high-grade needle coke.
[0013] The feedstock required for the production of high quality needle coke must contain only trace amounts of sulfur, nitrogen, asphaltenes, and inorganic impurities. Traditional methods such as hydrotreating can reduce the sulfur, nitrogen, and polyaromatics in the feedstock entering the coking drum. Hydrotreating processes include hydrodesulfurization, hydronitriding, and hydrodearomatization. Conventional processes involve maximizing the recycle of the heavy hydrocarbon fraction produced during the delayed coking process of needle coke to maximize needle coke yield. Extensive recycle of the heavy coker distillate and blending of this recycle distillate with fresh feed is known. However, this recycle requires catalytic hydrotreating of the distillate fraction at temperatures between 315°C and 400°C, pressures between 350 psi and 2000 psi, and liquid hourly space velocities (LHSV) between 0.2 and 3. Untreated distillate affects needle coke quality. It is known that as the heavy recycle fraction increases, the quality of the needle coke is affected.
[0014] In addition, inorganic additives such as fine powders of chromium oxide, iron oxide, calcium fluoride, and similar compounds can be added to the coke raw materials to reduce the coefficient of thermal expansion (CTE) of the resulting needle coke, but the addition of inorganic additives increases the ash content of the needle coke, up to a limit of 0.3 wt% ash content. Therefore, the conventional process for producing needle coke requires hydrotreating / hydrogenation of virgin feedstock or recyclable distillates. This increases the CAPEX / OPEX of the process and requires commercial units capable of operating under high pressure and high temperature. Hydrotreating of heavy petroleum fractions is a costly process. Another disadvantage of hydrotreating is that the hydrotreating process inevitably incurs a large amount of feedstock loss due to the production of light components. Furthermore, the catalysts used in hydrotreating require frequent replacement or regeneration as the heavy components in the hydrotreating stream fatigue and foul the catalyst.
[0015] In one aspect, the present invention provides a process for producing needle coke, the process comprising the steps of: (i) mixing predetermined amounts of a first feedstock and a second feedstock in a fractionator while heating the fractionator to obtain a mixture that is at a first predetermined temperature; (ii) charging the mixture into a delayed coker furnace and heating the furnace to a second predetermined temperature to obtain a heated coker material. (iii) charging the heated coker feedstock into a coke drum at a predetermined pressure and a third predetermined temperature and maintaining the same at the predetermined pressure and the third predetermined temperature for a first predetermined period of time to obtain coke and a distillate. (iv) The coke is separated so that the distillate leaves the top of the coke drum and enters the fractionator, resulting in separated coke in the coke drum. (v) treating the separated coke in the coke drum with superheated steam for a second predetermined period of time to obtain treated coke. (vi) After treatment the coke is quenched with water to obtain needle coke.
[0016] The details of this process are as follows: A predetermined amount of a first feedstock and a second feedstock are mixed within the fractionator while the fractionator is heated to obtain a mixture that is at a first predetermined temperature. In accordance with the present invention, the first feedstock is at least one selected from the group consisting of a first clarified slurry oil (CSO-1), a second clarified slurry oil (CSO-2), and a vacuum gas oil (VGO). In one embodiment, the first feedstock is a first clarified slurry oil (CSO-1). In another embodiment, the first feedstock is a second clarified slurry oil (CSO-2). In yet another embodiment, the first feedstock is a mixture of the second clarified slurry oil (CSO-2) and a vacuum gas oil (VGO). In accordance with the present invention, the mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) ranges from 4:1 to 10:1. In one embodiment, the mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) is 9:1. In another embodiment, the mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) is 5.3:1. According to the present invention, the first clarified slurry oil (CSO-1) is characterized by having a sulfur content in the range of 0.8% by mass to 1.5% by mass of the total mixture, a Conradson carbon residue (CCR) in the range of 3% by mass to 8% by mass of the total mixture, an ash content in the range of 0.01% by mass to 0.15% by mass of the total mixture, a density range of 0.5 g / cc to 1.5 g / cc, an asphaltene content of less than 5% by mass of the total mixture, and a boiling point range of 190°C to 700°C.
[0017] In one embodiment, the first clarified slurry oil (CSO-1) is characterized by a sulfur content of 1.26 wt.% of the total mass of the mixture, a CCR of 6.6 wt.% of the total mass of the mixture, an ash content of 0.08% of the total mass of the mixture, a density of 1.063 g / cc, an asphaltene content of less than 5 wt.% of the total mass of the mixture, and a boiling point in the range of 197°C to 700°C. In accordance with the present invention, the second clarified slurry oil (CSO-2) is characterized by a sulfur content in the range of 0.2% to 0.8% by mass of the total mixture, a Conradson carbon residue (CCR) in the range of 8% to 15% by mass of the total mixture, an ash content in the range of 0.01% to 0.1% by mass of the total mixture, a density in the range of 0.5 g / cc to 1.5 g / cc, an asphaltene content of less than 5% by mass of the total mixture, and a boiling point range of 245°C to 690°C. In one embodiment, the first clarified slurry oil (CSO-2) is characterized by a sulfur content of 0.57 wt.% of the total weight of the mixture, a CCR of 10.3 wt.% of the total weight of the mixture, an ash content of 0.05% of the total weight of the mixture, a density of 1.084 g / cc, an asphaltene content of less than 5 wt.% of the total weight of the mixture, and a boiling point in the range of 250° C. to 683° C.
[0018] According to the present invention, clarified slurry oil (CSO) is obtained from the bottom of a fluid catalytic cracking (FCC) reactor. According to the present invention, the vacuum gas oil (VGO) is characterized by a sulfur content in the range of 0.08% to 0.15% by mass of the total mixture, a Conradson Carbon Residue (CCR) in the range of 0.05% to 0.5% by mass of the total mixture, an ash content in the range of 0% to 0.15% by mass of the total mixture, a density in the range of 0.5 g / cc to 1.5 g / cc, an asphaltene content of less than 5% by mass of the total mixture and a boiling point range of 280°C to 600°C. In one embodiment, the vacuum gas oil (VGO) is characterized by a sulfur content of 0.12 wt.% by weight of the total mixture, a CCR of 0.1 wt.% by weight of the total mixture, ash content of 0% by weight of the total mixture, a density of 0.906 g / cc, an asphaltene content of less than 5 wt.% by weight of the total mixture, and a boiling point in the range of 284°C to 594°C. According to the present invention, vacuum gas oil (VGO) is obtained from a VGO hydrotreating process (VGOHT). In accordance with the present invention, the first feedstock may be hydrotreated or may have a hydrotreated portion and a non-hydrotreated portion.
[0019] In accordance with the present invention, the second feedstock is a heavy recycle stream selected from heavy coker oil gas (HCGO), heavy coker distillate, and heavy hydrocarbon streams. In this exemplary embodiment, the second feedstock is heavy coker oil gas (HCGO). In this exemplary embodiment, the second feedstock is in heavy coker distillate. According to the present invention, the second feedstock has a boiling point range of 300°C to 600°C. According to the present invention, the first feedstock and the second feedstock are not hydrotreated. According to the above embodiment of the present invention, the first feedstock, i.e., the clarified slurry oil (CSO-1), the clarified slurry oil (CSO-2), and the second feedstock, i.e., the heavy coker gas oil (HCGO), are not hydrotreated. In accordance with the present invention, the amount of the second ingredient ranges from 25% to 40% by weight of the total weight of the first ingredient. In some embodiments, the amount of the second ingredient is 30% by weight of the total weight of the first ingredient. In some embodiments, the amount of the second ingredient is 25% by weight of the total weight of the first ingredient. In some embodiments, the amount of the second ingredient is 50% by weight of the total weight of the first ingredient. In some embodiments, the amount of the second ingredient is 43% by weight of the total weight of the first ingredient.
[0020] According to the present invention, the first feedstock and the second feedstock are heated to a temperature in the range of 150° C. to 250° C. and then mixed in a fractionation apparatus in step (i). In accordance with the present invention, the first predetermined temperature ranges from 300° C. to 400° C. In one embodiment, the first predetermined temperature ranges from 325° C. to 350° C. In this exemplary embodiment, the first predetermined temperature is 330° C. In accordance with the present invention, the amount of the second feedstock is inversely proportional to the sulfur content of the first feedstock, i.e., the lower the sulfur content in the first feedstock, the greater the amount of recyclable stream (second feedstock) that can be mixed with the first feedstock. Similarly, the amount of the second feedstock is inversely proportional to the density of the first feedstock; ie, the lower the density of the first feedstock, the greater the amount of recyclable stream (second feedstock) that can be mixed with the first feedstock.
[0021] The mixture is charged to a delayed coker furnace, which is heated to a second predetermined temperature to obtain a heated coker feedstock. In accordance with the present invention, the second predetermined temperature ranges from 400° C. to 600° C. In one embodiment, the second predetermined temperature ranges from 480° C. to 515° C. In this exemplary embodiment, the second predetermined temperature is 498° C. The heated coker feedstock is charged to a coke drum at a predetermined pressure and a third predetermined temperature and maintained at the third predetermined temperature and pressure for a first predetermined period of time to produce coke and distillate. In accordance with the present invention, the third predetermined temperature ranges from 400° C. to 600° C. In one embodiment, the third predetermined temperature ranges from 425° C. to 500° C. In one example, the third predetermined temperature is 440° C. In another example, the third predetermined temperature is 485° C.
[0022] Due to losses during transfer from the furnace to the coke drum, the third predetermined temperature may be 10° C. to 20° C. lower than the second predetermined temperature. According to the present invention, the predetermined pressure is 2 kg / cm 2 (g) to 10 kg / cm 2 (g) range. In one embodiment, the predetermined pressure range is 2.5 kg / cm 2 (g) to 6 kg / cm 2 (g). In one embodiment, the predetermined pressure is 3 kg / cm 2 (g). In another embodiment, the predetermined pressure is 3.5 kg / cm 2 (g). In accordance with the present invention, the first predetermined period of time ranges from 15 hours to 50 hours. In one embodiment, the first predetermined period of time ranges from 18 hours to 36 hours. In one embodiment, the first predetermined period of time is 24 hours. In another embodiment, the first predetermined period of time is 20.5 hours. In yet another embodiment, the first predetermined period of time is 30 hours. The distillate exits the top of the coke drum into a fractionator to separate the coke and obtain a separate coke in the coke drum.
[0023] In accordance with the present invention, a coke drum is filled to 70% with separated coke vinegar. The coke separated in the coke drum is treated with superheated steam for a second predetermined period of time to obtain a treated coke. In accordance with the present invention, the temperature range of the superheated steam is from 300° C. to 500° C. In this embodiment, the superheated steam has a temperature of 485° C. According to the present invention, the pressure range of the superheated steam is 2.5 kg / cm 2 (g) to 10 kg / cm 2 (g). In one embodiment, the pressure of the superheated steam is 3 kg / cm 2 (g). In another embodiment, the pressure of the superheated steam is 3.5 kg / cm 2 (g). In accordance with the present invention, the first predetermined period of time ranges from 1 hour to 30 hours. In one embodiment, the second predetermined period of time is 4 hours. In another embodiment, the second predetermined period of time is 24 hours. The treated coke is quenched with water to obtain needle coke.
[0024] In one embodiment, the treated coke is cooled with water in a coke drum. The coke is then cut with a coke cutting tool using a high pressure water jet. The needle coke is then fractionated based on coke quality. The needle coke is then stored in separate designated silos. The yield of needle coke depends on the CCR of the mixture fed into the coking chamber / drum, i.e. the higher the CCR of the mixture, the higher the yield of needle coke. Hydrotreating the distillate reduces the CCR of the distillate as well as the fed mixture. Hence, hydrotreating the distillate reduces the yield even though it can produce good quality needle coke. The process of the present invention produces needle coke with low sulfur and CTE without the need for hydrotreating of heavy coker distillate. Thus, the process of the present invention eliminates hydrotreating of heavy coker distillate, thereby reducing CAPEX / OPEX. The process of the present invention is efficient and cost effective. The needle coke of the present invention has low sulfur content and low CTE.
[0025] As the amount of recycled non-hydrotreated heavy coker distillate (second feedstock) increases beyond a certain percentage of the first feedstock, the amount of good quality needle coke in the coke drum decreases, and therefore there exists an optimal recycled ratio of non-hydrotreated first feedstock and non-hydrotreated second feedstock, whereby the maximum mass of good quality needle coke can be obtained in the coke drum. The needle coke according to the invention has a sulfur content of < 0.5% by weight, an ash content of < 0.2% by weight, and a coefficient of thermal expansion (CTE) of < 1.2 x 10 -6 / o C, high quality petroleum coke with actual density exceeding 2.13 g / cc.
[0026] In accordance with the present invention, a first feed is prepared by blending target amounts of non-hydrotreated CSO and hydrotreated VGO to meet the input feed specifications for sulfur, ash and aromatics. The hot coker product of the fractionator is allowed to flow to the bottom of the fractionator in exchange for the first feed. A predetermined amount of the second feed (hot heavy coker gas oil (HCGO)) is mixed with the first feed at the bottom of the fractionator and heated to obtain a mixture with a temperature range of 325°C to 350°C. This mixture is fed to a delayed coker furnace and heated to a range of 480°C to 515°C before being fed to a delayed coker furnace at a temperature range of 3-6 kg / cm. 2The raw material is pumped to the bottom of the operating coke drum at (g) coke drum head pressure. Sufficient residence time (20 to 36 hours) in the coke drum is allowed to convert the coker feedstock into needle coke and distillate. The coke distillate from the top of the coke drum is pumped to the fractionator. Once the first coke drum is filled with coke, the feedstock is switched to the second coke drum. Superheated steam is passed through the filled coke drum. The coke drum is cooled with water. The coke is cut by coke cutting tools using high pressure water jets. The needle coke is fractionated based on coke quality. The needle coke is stored in designated silos.
[0027] The above description of the embodiments is for illustrative purposes only and is not intended to limit the scope of the present invention to the scope of the description alone. Individual components of a particular embodiment are generally not limited to that particular embodiment and may be interchanged. Such variants cannot be considered as distinct from the present invention, and all such variants are considered to be within the scope of the present invention. The present invention is further illustrated by the following non-limiting embodiments, which are provided for illustrative purposes only and should not be construed as limiting the scope of the present invention. The following experiments can be scaled up and tested to industrial / commercial scale, and the results obtained can be extrapolated to industrial scale.
[0028] Test Details: Process for producing needle coke according to the present invention in a delayed coker plant example: Experimental studies were carried out using a coker pilot plant with a production capacity of 1 barrel per day. The coker pilot plant consists of a raw material vessel, raw material pump, recirculation pump, electric furnace, coke drum, fractionator, and product vessel. The physical properties of the raw materials used in the experiments and the experimental conditions are shown in Tables 1 and 2, respectively.
[0029] [Table 1]
[0030] [Table 2]
[0031] Comparison of needle coke produced from first feedstock (non-hydrotreated virgin feedstock (CSO-1) : The following facts can be seen from Table 2: (i) in Example 1, no non-hydrotreated heavy coker fraction (second feed) was recycled, (ii) in Example 2, 30.2% of the non-hydrotreated heavy coker fraction (second feed) was recycled, and (iii) in Example 3, 51.2% of the non-hydrotreated heavy coker fraction (second feed) was recycled from the first feed. The quality of needle coke produced from raw materials / mixtures and virgin raw material not hydrotreated (CSO-1) is compared and shown in Tables 3 and 4, respectively.
[0032] [Table 3]
[0033] It can be seen from Table 3 that the quality of the non-hydrotreated recycle stream produced at different capacity ratios ((new feed + recycle) / new feed) varies considerably. With an increase in the recycle (secondary feed) in the non-hydrotreated heavy coker distillate stream, the density and sulfur content of the heavy coker distillate product increases, thus increasing the sulfur content and density of the mixed stream, and deteriorating both in quantity and quality of needle coke. The same can be observed in Table 4.
[0034] [Table 4]
[0035] It can be seen from Table 4 that increasing the amount of recycle (secondary feedstock) from 0% (example 1) to 30% (example 2) decreased the CTE of needle coke and increased the sulfur content (see Figures 2 and 3). Increasing the recycle from 30% to 50% increased both the CTE and sulfur content. Thus, the coke quality deteriorated with increasing the recycle rate from 30% to 50%.
[0036] Table 5 illustrates the quality of needle coke by zone at different capacity ratios in CSO-1.
[0037] [Table 5]
[0038] As can be seen from Table 5, for a 30% recycle of the non-hydrotreated recycle stream (secondary feed in Example 2), 100% (total) of the coke bed would have a CTE of <1.2 x 10 at the same operating conditions. -6 / °C (see Figure 4). However, further increases in the recycle fraction of non-hydrotreated recycle stream beyond 30% resulted in a CTE of <1.2 x 10 -6 The amount of coke bed exhibiting 0.1 / °C was reduced to 60%.
[0039] Comparison of needle coke produced from primary raw materials: CSO-2 blended with VGO : From Table 2, it can be seen that: (i) in Example 4, only the first feedstock (CSO-2) was used without any recycle; (ii) in Example 5, the first feedstock (CSO-2) was a second feedstock (heavy coker distillate) with 43.1% recycled from the virgin feedstock base; (iii) in Example 6, the first feedstock was a blended first feedstock (i.e., 84.2% CSO-2 and 15.8% VGO); and (iv) in Example 7, the blended first feedstock (i.e., 90% CSO-2 and 10% VGO) was a second feedstock (heavy coker distillate) with 24.6% recycled from the first feedstock.
[0040] Table 6 illustrates the quality of needle coke throughout the coke drum, including CSO-2 and VGO.
[0041] [Table 6]
[0042] Compared to the case where only CSO-2 was treated without recycle (Example 4), needle coke with both higher CTE and sulfur content was obtained when 43% was not hydrotreated (Example 5). For the blend of CSO-2 and VGO (Example 6), only a small fraction of the total CTE of the entire coke bed was observed to be improved, even though the sulfur content was significantly reduced compared to Example 4. When 24% non-hydrotreated recycle (Example 7) was used with CSO-2 and VGO as the first feed, a significant improvement in CTE was observed, and the sulfur content was also slightly lower than in Example 4. Thus, an optimal amount of non-hydrotreated recycle stream (secondary feed) was required to obtain good quality needles at high yields.
[0043] Table 7 illustrates the needle coke quality by zone at different CSO-2 and VGO throughput ratios.
[0044] [Table 7]
[0045] Table 7 shows that using the non-hydrotreated recycled stream (second feed) of CSO-2 (first feed) reduces the CTE by 1.2 x 10 -6 The coke exhibiting a temperature of 0.1 to 1.5 °C was not produced. The quality of the coke produced after recycling to CSO-2 was reduced. When CSO-2 was blended with VGO in a ratio of 5.3:1 without recycle (Example 6), the quality of the fine needle coke produced was improved when compared to virgin CSO-2 without recycle (Example 4). Furthermore, when CSO-2 was blended with VGO in a ratio of 9:1 and mixed with 25% of the heavy coker distillate (second feed) (Example 7), the 100% coke bed had a CTE of 1.2 x 10 at the same operating conditions. -6 / o The score was less than C. The needle coke obtained as described above can be further calcined to produce calcined needle coke, which can be used as a material for graphite electrodes.
[0046] Technological advances The present invention as described above has several technical advantages including but not limited to a needle coke production process that achieves the following: The production of high-quality coke eliminates the need for hydrotreating new raw materials and recycled material streams. Delayed Coker Maximizes production of low CTE, low sulfur needle coke in the coke drum. Obtaining an inherent recycle of non-hydrotreated heavy coker distillate fraction, which impacts needle coke quality and quantity. Maximize the amount of good quality needle coke without expensive hydroprocessing of recyclable heavy hydrocarbon fractions produced from the main feedstock and coker processing or without adding inorganic additives to the coker feedstock; · Simple, efficient and cost-effective.
[0047] The details of the embodiments of the present invention and various features and advantages are described below by referring to non-limiting examples. Descriptions of well-established existing components and processing techniques are omitted so as not to unnecessarily complicate the understanding of the embodiments of the present invention. The examples used in the present invention are intended only to facilitate the understanding of how the embodiments of the present invention can be put into practice and to enable those skilled in the art to practice the embodiments of the present invention. Therefore, the examples should not be construed as limiting the scope of the embodiments of the present invention. The above description of the specific embodiments sufficiently reveals the general nature of the embodiments of the present invention, so that by applying current knowledge, the specific embodiments can be modified or adapted for different applications without departing from the general concept, and therefore, the adaptation / modification should and is intended to be understood in the sense and scope of equivalents to the embodiments of the present invention. The usage of phrases and terms used in this specification are for illustrative purposes and not for limiting purposes. Therefore, the embodiments described in this specification are described based on preferred embodiments, and at the same time, it is recognized that those skilled in the art can practice the embodiments described in this specification even if they are modified within the spirit and scope of the embodiments described in this specification.
[0048] Throughout this specification, the terms "comprise", "constitute", and their variants "comprise" or "comprising" are intended to imply the inclusion of a stated element, integer or step or group of elements, integers or steps, but not the exclusion of other elements, integers or steps or other groups of elements, integers or steps. The use of the phrase "at least" or "at least one" suggests the use of one or more elements or components or quantities, according to which one or more may be used in embodiments of the invention to achieve one or more desired substances or results. Any discussion of documents, acts, materials, devices, articles or the like contained in this specification is included solely for the purpose of providing a context for the present disclosure and should not be construed as an admission that any or all of the foregoing constitutes part of the known inventive technology base or is common general knowledge in the field relevant to the present invention that existed anywhere prior to the priority date of this application.
[0049] The numerical values expressing different physical parameters, variables, dimensions and quantities are approximations and any higher or lower numerical values substituted for the parameters, variables, dimensions and quantities are intended to be within the scope of the invention unless otherwise stated in the specification. Although considerable emphasis has been placed on the different components and component parts of the preferred embodiment, many embodiments are possible, and many changes can be made to the preferred embodiment without departing from the principles of the invention. It is apparent to those skilled in the art that the present invention or the characteristics of the preferred embodiment as well as other embodiments can be modified, and it should be clearly understood that the above description is merely for the purpose of illustrating the present invention and should not be construed as limiting.
Claims
1. A process for producing needle coke, said process comprising the steps of: (i) mixing predetermined amounts of a first feedstock and a second feedstock in said fractionator while heating the fractionator to obtain a mixture at a first predetermined temperature; (ii) transferring the mixture to a delayed coker furnace and heating the furnace to a second predetermined temperature to obtain a heated coker feed; (iii) transferring said heated coker feed to a coke drum at a third predetermined temperature and pressure and maintaining said third predetermined temperature and said predetermined pressure for a first predetermined time period to obtain coke and a distillate; (iv) directing said distillate through an upper portion of said coke drum to said fractionator to separate said coke and obtain separated coke in said coke drum; (v) treating the separated coke with superheated steam in the coke drum for a second predetermined period of time to obtain a treated coke; (vi) quenching the treated coke with water to obtain the needle coke.
2. The process as claimed in claim 1, wherein said first feedstock is at least one selected from the group consisting of a first clarified slurry oil (CSO-1), a second clarified slurry oil (CSO-2), and a vacuum gas oil (VGO).
3. The process as claimed in claim 2, wherein the mass ratio of said second clarified slurry oil (CSO-2) to said vacuum gas oil (VGO) ranges from 4:1 to 10:
1.
4. 3. The process as claimed in claim 2, wherein the mass ratio of said second clarified slurry oil (CSO-2) to said vacuum gas oil (VGO) is 5.3:
1.
5. 2. The process as claimed in claim 1, wherein the mass ratio of the second clarified slurry oil (CSO-2) to the vacuum gas oil (VGO) is 9:
1.
6. A process as claimed in claim 1, wherein said first clarified slurry oil (CSO-1) is characterized in that it has the following features: Sulfur content in the range of 0.8% to 1.5% by mass of the total mixture - Conradson carbon residue (CCR) is between 3% and 8% by mass of the total mixture. - the ash content is between 0.01% and 0.15% by mass of the total mass of the mixture; · Density range 0.5 g / cc to 1.5 g / cc; the asphaltene component is less than 5% by mass of the total mass of the mixture; ・ Boiling point range: 190℃ to 700℃
7. A process as claimed in claim 1, wherein the second clarified slurry oil (CSO-2) is characterized in that it has the following features: Sulfur content in the range of 0.2% to 0.8% by mass of the total mixture - Conradson carbon residue (CCR) is between 8% and 15% by mass of the total mixture. The ash content of the mixture is in the range of 0.01% to 0.1% by mass. · Density range 0.5 g / cc to 1.5 g / cc; the asphaltene component is less than 5% by mass of the total mass of the mixture; ・ Boiling point range: 245℃ to 690℃
8. A process as claimed in claim 1, wherein said vacuum gas oil (VGO) is characterized by the following features: Sulfur content ranges from 0.08% to 0.15% by mass in the total mass of the mixture Conradson Carbon Residue (CCR) ranges from 0.05% to 0.5% by mass of the total mixture The ash content of the mixture is in the range of 0 to 0.15% by mass. · Density range 0.5 g / cc to 1.5 g / cc; the asphaltene component is less than 5% by mass of the total mass of the mixture; ・ Boiling point range: 280℃ to 600℃
9. A process as claimed in claim 1, wherein said first feedstock is hydrotreated, partially hydrotreated, or unhydrotreated.
10. 2. The process as claimed in claim 1, wherein said first feedstock and said second feedstock are not hydrotreated.
11. 10. The process as claimed in claim 1, wherein said second feedstock is a heavy recycle stream selected from heavy coker oil gas (HCGO), heavy coker distillate, and a heavy hydrocarbon stream.
12. The process as claimed in claim 1, wherein said second feedstock has a boiling point in the range of 300°C to 600°C.
13. 2. The process as claimed in claim 1, wherein said predetermined amount of said second raw material comprises 25% to 40% by weight of a total weight of said first raw material.
14. 2. The process as claimed in claim 1, wherein said predetermined amount of said second ingredient is 30% by weight of a total weight of said first ingredient.
15. 2. The process as claimed in claim 1, wherein said predetermined amount of said second ingredient is 25% by weight of a total weight of said first ingredient.
16. 2. The process as claimed in claim 1, wherein said first feedstock and said second feedstock are heated to a temperature range of 150° C. to 250° C. before being mixed in said fractionator in step (i).
17. 2. The process as claimed in claim 1, wherein said first predetermined temperature range is from 300°C to 400°C.
18. 2. The process as claimed in claim 1, wherein said first predetermined temperature range is from 325°C to 350°C.
19. 2. The process as claimed in claim 1, wherein said second predetermined temperature range is from 400°C to 600°C.
20. 2. The process as claimed in claim 1, wherein said second predetermined temperature range is from 480°C to 515°C.
21. 2. The process as claimed in claim 1, wherein said third predetermined temperature is in the range of 400°C to 600°C and said predetermined pressure is 2 kg / cm 2 (g) to 10 kg / cm 2 (g) wherein the first predetermined period of time is in the range of 15 hours to 50 hours.
22. 2. The process as claimed in claim 1, wherein said third predetermined temperature is in the range of 425°C to 500°C and said predetermined pressure is 2.5 kg / cm 2 (g) to 6 kg / cm 2 (g), wherein said first predetermined period of time is in the range of 18 hours to 36 hours.
23. 2. The process as claimed in claim 1, wherein the superheated steam has a temperature in the range of 300° C. to 500° C. and a pressure in the range of 2.5 kg / cm 2 (g) to 10 kg / cm 2 (g), the second predetermined period of time is in the range of 1 hour to 30 hours.
24. 2. The process as claimed in claim 1, wherein the needle coke has a coefficient of thermal expansion (CTE) of less than 1.2 x 10 -6 / ℃.