Article Cite This: Energy Fuels 2019, 33, 6373−6379
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Influence of Parameters of Delayed Coking Process and Subsequent Calculation on the Properties and Morphology of Petroleum Needle Coke from Decant Oil Mixture of West Siberian Oil Natalia K. Kondrasheva, Viacheslav A. Rudko,* Maxim Yu. Nazarenko, Vladimir G. Povarov, Ivan O. Derkunskii, Rostislav R. Konoplin, and Renat R. Gabdulkhakov
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Saint-Petersburg Mining University, St. Petersburg 199106, Russia ABSTRACT: This paper includes the results of studies of the temperature effect in the range of 480−510 °C at an excess pressure of 0.35 MPa, as well as the effect of excess pressure from 0.15 to 0.55 MPa at a temperature of 500−510 °C, during the delayed coking of a decant oil obtained from a mixture of West Siberian oils and subsequent calcination in an inert atmosphere of nitrogen at 1100 °C on the microstructure and properties of the needle coke. Properties such as absolute density, volatilematter yield, ash, sulfur, and trace element contents were analyzed to evaluate the quality of the “green” and calcined coke. The microstructure of the obtained coke was analyzed by means of X-ray diffraction, for which the evaluation criteria were the interplanar spaces d002 and d100, as well as the crystallite sizes Lc and La. The scanning electron microscopy method was used to confirm the results of the formed structure of petroleum coke analysis obtained earlier. The calcined samples were assigned to needle cokes with stringy-circular flow domain anisotropy.
1. INTRODUCTION In the near future, Russia will continue to gain capacity on the processing of heavy oil feedstock in refineries, most commerce capable of which is the thermal delayed coking process, which makes it possible to deepen the refinery process up to 98%.1,2 The total load of delayed coking units for raw materials will be about 13.6 million tons in Russia by 2020.3 With this process, it is possible to not only increase the yield of light (gasoline, kerosene, and diesel fuel) and dark (ship and boiler fuels) oil products but also to expand the range of commercial products with carbon materials such as petroleum coke, coking additive, and petroleum pitch. Petroleum coke is a high-carbon product of compaction and thermal polycondensation reactions of residual oil or high aromatic hydrocarbon distillate, which, at the molecular level, is characterized by the presence of protocrystalline and amorphous components of various modifications of carbon compounds with a complex architecture of polydisperse pores.4 The most popular in production is needle coke, which is a carbon material with the most developed anisotropy of fibers.5,6 It is used to produce ultra-high-power graphite electrodes. Needle coke is obtained from high aromatic hydrocarbon distillates with low sulfur and metal contents, which consists of a large amount of polycyclic aromatic hydrocarbons (3, 4, and 5 aromatic rings) and has a low asphaltene content.7 Such a raw material in the carbonization process through the formation of metaphase or mesophase spheres is converted into an anisotropic carbon material with a microcrystalline needle-like structure. The needle coke microcrystalline structure is important since all of the physical properties of the carbon material depend on it. The characteristic features of such a structure should be a high level of anisotropy, regular micropores between carbon layers, a large size of crystallites in the direction of one axis, especially after calcination, and a large area of flow domains.7 © 2019 American Chemical Society
The influence of various input parameters in the coking process on the structure and properties of petroleum coke is described in the articles of many researchers. Halim et al. assess the effect of temperature and pressure on the quality characteristics of needle coke in their review.8 When coking a low sulfur vacuum residue in the temperature range of 440−500 °C, the optimum carbonization temperature is preferred, since the high-temperature process prematurely terminates the carbonization and the growth of the mesophase. At a lower temperature, a longer time of holding the raw materials in the reaction zone is required, which contributes to the growth and enlargement of the mesophase. When the temperature is too low, the intensity of the gaseous product release decreases, which leads to the disruption of the mesophase structure. It was noted that the change in pressure affects the quality of needle coke. At low pressure, the coefficient of thermal expansion tends to increase, and the anisotropy of the fibers decreases. In this paper,9 Ibrahim determines the effect of calcination temperature on the actual density of Syrian raw coke obtained in the process of delayed coking. Studies were conducted in the temperature range of 1300−1700 K in an inert atmosphere of nitrogen. The actual density varies from 1.39 to 2.04 g/cm3. The main factor affecting the increase in density is the removal of volatile substances, occurring up to about 800 K, and then the removal of sulfur. Legin-Kolar and Ugarković investigated coking processes, the effect of various types of raw materials of atmospheric and gasoline pyrolysis residue and fluid catalytic cracking (FCC) decant oil on the structure of petroleum coke calcined at 1300 or 2400 °C is shown in ref 10. The effect of temperature and Received: May 6, 2019 Revised: June 24, 2019 Published: June 26, 2019 6373
DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
Article
Energy & Fuels Table 1. Operating Parameters of the Decant Oil Carbonization Process parameters of coking
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
Ex. 7
overpressure, MPa coking temperature (final temperature), °C heating time to final temperature, min average heating rate of the coking layer, °C/min isothermal time at final temperature, min mass of raw materials, kg
0.35 480−488 285 1.68 60 0.280
0.35 490−500 250 1.92 90 0.246
0.35 500−510 325 1.54 60 0.225
0.15 500−503 360 1.39 65 0.257
0.25 500−510 295 1.69 65 0.246
0.45 500−506 250 1.88 90 0.270
0.55 503−512 255 1.97 45 0.260
Table 2. Sample Mass Change in the Calcination Process of Petroleum Coke parameter of samples
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
Ex. 7
weight before calcination, g weight after calcination, g weight loss after calcination, % wt.
24.6525 19.8717 19.39
19.4723 14.5760 25.14
21.5441 17.8530 17.13
17.4111 13.3326 23.42
28.0399 23.1630 17.39
21.1554 16.9670 19.80
29.0085 24.4303 15.78
480−488 to 500−510 °C at a constant overpressure of 0.35 MPa in each experiment, and the second one with a variation in coking pressure from 0.15 to 0.55 MPa at a constant temperature of 500− 510 °C in each experiment. The feed load was 0.225−0.280 kg and the heating rate to the final temperature was 1.39−1.97 °C/min. However, the heating rate to the final temperature in the commercial delayed coking process is 200−300 °C/min for comparison. After reaching the carbonization temperature, the isothermal mode was kept until the formation of the gas−liquid product mixture stopped, as indicated by the pressure decrease in the reactor. The constant temperature was maintained from 45 to 90 min. The operating parameters of the coking process during each experiment are shown in Table 1. 2.2. Method of Calcination. The calcination of petroleum coke was carried out in a Nabertherm muffle furnace at a temperature of 1100 °C in an inert atmosphere of nitrogen supplied in an amount of 2 L/h. Petroleum coke was placed in alundum crucibles in an amount of 17.4−29.0 g. The heating rate of the calcination temperature was 10.48 °C/min, and the time of the isothermal mode at the calcination temperature was 60 min. The mass loss after calcination was 15.78− 25.14% wt. The parameters of the calcination process of the obtained petroleum coke samples are shown in Table 2. 2.3. Methods for Analyzing the Physicochemical Properties. Representative samples of raw and calcined petroleum coke produced during experiments 1−7 were analyzed to determine the physicochemical properties. Among the quality indicators defined were humidity, volatile content, actual and apparent density, and total porosity. The determination of the moisture content of the produced petroleum coke was carried out in a drying cabinet according to GOST 27589-91 “Coke. Method for determination of moisture content in an analytical sample” (ISO 687-74) and GOST 335032015 “Solid mineral fuels. Methods for the determination of moisture in an analytical sample” (ISO 11722:2013, ISO 5068-2:2007). Accelerated methods for the determination of the moisture content. A sample weighing 2 g taken from coke with a particle size of less than 125 μm was dried at a temperature of 105 ± 5 °C. The mass fraction of moisture was calculated by weight loss. The ash content was determined according to GOST 22692 “Carbon materials. Method for the determination of ash content.” A sample of material weighing 2 g was burned in a muffle furnace at a temperature of 815 ± 10 °C and held at a given temperature to constant weight. The ash content was calculated by weight loss. The yield of volatile substances was determined by heating a sample with a sample mass of 1 g in a porcelain crucible with a ground-in lid without air access in a muffle furnace at a temperature of 815 ± 10 °C for 7 min according to GOST 22898 “Low-sulfur petroleum coke. Specifications” and GOST R 55660 “Solid mineral fuels”. The percentage of the volatile-matter content was determined after correction for weight loss caused by moisture release. The actual density was determined by weighing the coke sample in air and the pycnometric liquid according to GOST 22898 “Low-sulfur
heating rate on the surface morphology, the height of Lc crystallites, and the interplanar distance d002 of petroleum coke has been determined. With an increase in the calcination temperature, the height Lc increases and the interplanar distance d002 decreases. Heintz studied the effect of the calcination rate on the properties of petroleum coke and gave methods for assessing its quality in refs 11, 12. A slower heating rate during calcination is preferable to obtain the most optimal properties in anisotropic coke. It is also noted that the height of the crystallites Lc and their diameter La have a minimum value if the thermal treatment is performed in the range of 600−900 °C. Mochida et al. studied the process of decant oil carbonization and the influence of technological parameters on the formation of the petroleum coke needle structure in ref 13. An excellent needle-like coke structure was achieved at a pressure of about 1.57 MPa and a temperature of 500 °C, through the formation of the mesophase, its coarsening and the formation of gaseous products parallel to the axis of the apparatus under the action of the hydrodynamics. In this paper, the authors propose to apply a set of analytical methods to assess the effect of overpressure and temperature of the delayed coking process on the quality and morphology of petroleum coke produced from a decant oil of a mixture of West Siberian oils.
2. EXPERIMENTAL SECTION 2.1. Material and Method of Coking. To carry out experiments on coking and obtaining representative samples of petroleum coke for the study, decant oil is used as a feedstock. This is a product of an industrial catalytic cracking unit (FCC) from a mixture of West Siberian oils. To obtain petroleum coke from decant oil, a laboratory delayed coking unit of St. Petersburg Mining University consisting of a reaction unit and a distillate collection unit was used. The reaction unit consisted of a steel coking reactor and an electric furnace with three independent heating zones to maintain a uniform temperature throughout the height of the coking layer. The reactor is equipped with a pressure gauge to monitor pressure. The removal of the gas− liquid product mixture was carried out through a tube located in the reactor lid through a needle valve, from where it entered the heat exchanger of the “pipe-in-pipe” type and the receiving flask for distillates, and the hydrocarbon gas was withdrawn to the exhaust system. The detailed design of the unit and the process of coking is described in ref 14. Two series of experiments on the coking of decant oil were conducted: the first one with a variation of coking temperature from 6374
DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
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Energy & Fuels Table 3. Raw Coke Properties parameter
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
Ex. 7
moisture content, % yield of volatiles, % ash content, % actual density, g/cm3 microstructure score
0.13 13.41 0.48 1.62 1.9
0.39 8.30 0.47 1.19 3.3
0.30 5.90 0.45 1.60 2.2
0.23 7.05 0.49 1.25 3.0
0.32 3.92 0.44 1.43 3.3
0.28 4.43 0.50 1.46 3.3
039 4.69 0.49 1.22 3.3
Table 4. Calcined Coke Properties parameter
Ex. 1c
Ex. 2c
Ex. 3c
Ex. 4c
Ex. 5c
Ex. 6c
Ex. 7c
moisture content, % yield of volatiles, % actual density, g/cm3 microstructure score
0.24 2.48 2.14 4.5
0.38 3.57 2.11 5.3
0.28 1.87 2.15 5.4
0.14 2.75 2.05 5.3
0.32 2.81 1.94 5.6
0.33 1.07 1.80 5.4
0.29 1.06 2.12 5.5
Table 5. Quantitative Composition of Sulfur and Trace Elements in Crude Petroleum Cokes element, ppm
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
Ex. 7
S Si Al Ni V
313.0 63.8 26.9 25.5 9.1
372.0 63.7 25.3 40.6 7.1
394.0 69.5 41.1 44.8 12.9
367.0 67.6 24.5 64.7 8.1
383.0 80.1 31.8 34.3 6.1
557.0 89.8 40.6 50.9 7.5
679.0 83.3 33.2 28.0 9.2
Figure 1. Comparison of diffractograms of raw petroleum coke and calcined coke at 1100 °C. (a) Experiment 1; (b) experiment 4; (c) experiment 5; and (d) experiment 7. petroleum coke. Specifications” and GOST 10220-82 “Coal coke. Methods for determination of the density and porosity”. A similar assessment of the physicochemical properties of petroleum coke produced by coking from tar (vacuum residue) and asphalt of a mixture of West Siberian oils was carried out by the authors and is described in ref 15. 2.4. Method of X-ray Fluorescence Spectrometry. The determination of sulfur and trace elements in the obtained samples of crude petroleum coke was carried out using X-ray fluorescence spectrometry without prior ashing of the samples using the additive method on a sequential XRF-1800 Shimadzu wave dispersion X-ray
fluorescence spectrometer. The device is equipped with an X-ray tube with a 2.7 kW rh anode. A detailed description of the methodology for determining sulfur and microelements is given in ref 16. 2.5. Morphology Evaluation Method. The morphology of the samples of raw and calcined petroleum coke was examined using electronic scanning microscopy on Tescan Vega 3 LMH. To study the microstructure, the samples of the petroleum coke produced were ground to a particle size of less than 100 μm. An electron microscopy image of petroleum coke particles was obtained in secondary electrons (SE) in the scanning mode resolution. The accelerating voltage was 20 kV and the emission current was 120 μA. The scanning rate with 6375
DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
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Energy & Fuels Table 6. Results of the Diffractometric Analysis of Raw Cokes estimate from reflex (002) no. of Exp. Ex. Ex. Ex. Ex. Ex. Ex. Ex.
1 2 3 4 5 6 7
estimate from reflex (100)
2θ, deg
FWHM, deg
d002, Å
Lc, Å
2θ, deg
FWHM, deg
d100, Å
La, Å
25.780 25.760 25.740 25.720 25.800 25.800 25.760
2.5800 3.0000 2.5800 2.9400 3.0000 3.0800 3.0200
3.4530 3.4557 3.4583 3.4609 3.4504 3.4504 3.4557
30.6271 26.3175 30.6246 26.8549 26.3196 25.6331 26.1425
42.520 42.640 42.640 42.440 42.600 42.580 42.240
6.5400 6.5800 5.9000 7.0600 6.0300 6.3800 6.4400
2.1244 2.1187 2.1187 2.1282 2.1206 2.1215 2.1378
12.6057 12.5341 13.9803 11.6733 13.6767 12.9248 12.7895
Table 7. Results of the Diffractometric Analysis of Calcined Cokes estimate from reflex (002) no. of Exp. Ex. Ex. Ex. Ex. Ex. Ex. Ex.
1c 2c 3c 4c 5c 6c 7c
estimate from reflex (100)
2θ, deg
FWHM, deg
d002, Å
Lc, Å
2θ, deg
FWHM, deg
d100, Å
La, Å
25.360 25.240 25.280 25.220 25.208 25.280 25.440
4.8800 4.7800 4.9600 4.7600 4.6600 4.4600 4.9800
3.5092 3.5257 3.5202 3.5284 3.5301 3.5202 3.4984
16.1436 16.4780 15.8803 16.5467 16.9021 17.6640 15.8214
43.040 43.220 43.320 43.100 43.260 43.280 43.300
3.1600 3.4800 3.6800 3.7200 3.4400 3.3600 3.4200
2.0999 2.0916 2.0870 2.0971 2.0897 2.0888 2.0879
26.1757 23.7751 22.4868 22.2274 24.0558 24.6323 24.2003
the accumulation of scanning electron microscopy (SEM) images was 100 μs/pxl. The assessment of the microstructure by comparison with the control scale of the microstructure was also carried out according to GOST 26132-84 “Petroleum and pitch cokes. Method of microstructure assessment” on a microvisor μVizo-MET-221 in reflected plane-polarized light with an increase of 90−100×. A similar assessment of the microstructure of the petroleum coke from tar and asphalt is described by the authors in ref 15. 2.6. Method of X-ray Phase Analysis. X-ray diffraction analysis was performed using an XRD-7000 Shimadzu X-ray diffractometer (Cu Kα radiation, 2.7 kW) at room temperature using the polycrystal method. The X-ray images were taken at long accumulation times (2 s) and at a scanning step of 0.02°. Asymmetric reflexes of petroleum cokes were decomposed into peaks, the profile of which is described by Gaussian with a maximum at angles of 2θ, which characterize certain structural components of petroleum coke samples.
experiments 1−7, the increase of the actual density from 1.19− 1.62 to 1.80−2.15 g/cm3 occurs due to the ordering of the material structure and the release of volatile substances. It can be noted that there is a trend of reduction in the yield of volatile substances with an increase of pressure by 0.15−0.55 MPa, as in samples of both crude petroleum coke and those calcined ones at 1100 °C. After calcination, the yield of volatile substances decreases 1.4−5.4 times for each of the seven obtained petroleum coke samples. However, if the initial statistical processing is carried out, then two points fall out, experiments 1 and 5. In the first case, the content of volatile substances in the raw coke is too high and in the second case, in the calcined one, is too low compared with other samples. In this case, the decrease in the yield of volatile substances after calcination at 1100 °C occurs in a narrower range, in 2.3−4.4 times. The increase in the temperature of coking from 480− 488 to 500−510 °C at 0.35 MPa also leads to a decrease in the yield of volatile substances. The microstructure score estimated by comparison with the control microstructure scale according to GOST 26132-84 with an increase of 90−100× is a characteristic relating the structure of coke by a 10-point scale from isotropic (diameter < 3 μm) to large needle (diameter > 3 μm; length > 600) to one of the species. The results of parallel tests in one laboratory do not differ by more than 0.2−0.3 points. The structure of the obtained raw coke samples is about 3.3 points by this method and allows you to refer it to a small fibrous structure. After calcination at 1100 °C, the microstructure of coke is already 5.5 points, and the characteristic of structural components is a small needle with the presence of groups of oriented fibers. The X-ray fluorescence analysis (Table 5) showed an increase in the sulfur content in the petroleum coke with an increase in the excess coking pressure from 0.0367 to 0.0679% wt. The content of vanadium in the resulting images is in the range of 6.1−12.9 ppm, and nickel in the range of 25.5−64.7 ppm. For a detailed assessment of the fine structure of petroleum coke by the X-ray structural method, we used the interplanar
3. RESULT AND DISCUSSION The properties of crude petroleum coke and calcination petroleum coke at 1100 °C are given in Tables 3 and 4. In the course of the calcination process of petroleum coke samples in Table 8. Dependence of the Average Height of Crystallites Lc (Å) for Various Types of Cokes on the Heat Treatment Temperature4,23 calcination temperature, °C
regular coke
needle coke
isotropic coke
500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600
23 20 15 15 16 18 21 25 34 40 51 56
24 26 16 15 17 19 22 29 36 40 63 78
25 20 17 16 16 16 20 22 29 37 50 63 6376
DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
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Energy & Fuels
Figure 2. SEM images of samples of the crude petroleum coke and coke calcined at 1100 °C of experiment 7. (a) Petroleum coke of experiment 7 in a field of view of 68.1 μm; (b) raw coke of experiment 7 at 16.8 μm; (c) calcined coke of experiment 7 in a field of view of 67.2 μm; (d) calcined coke of experiment 7 in a field of view of 16.6 μm.
where λ = 1.5406 is the X-ray wavelength for Cu Kα, Å, and θ is the Bragg diffraction angle, rad. The average linear size of crystallites Lc and La was determined in Å by the Scherer equation19
distance of the diffraction maxima (002) and (100), as well as the dimensions of the coherent scattering region in the directions of the “c” axes (average height Lc of crystalline) and (average diameter La of hexagonal layers). To determine the interplanar distance (d002 and d100) in Å obtained from raw and calcined samples of petroleum coke, the calculation was performed according to the Wulff−Bragg equation17,18
Lc = 0.89λ /β002 cos θ
002
and La = 0.89λ /β100 cos θ
100
where 0.89 is the Scherer constant, which is conventionally set for cokes, the same for uniformity in the published results;20 β
d = λ /2 sin θ 6377
DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
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Energy & Fuels
calcining temperature of 500−1600 °C with a step of 100 °C for three different types of petroleum cokes: ordinary, needlelike, and isotropic one. For all three types of cokes, the average height Lc of crystallites has an extreme character depending on the calcination temperature with a minimum at a temperature of 800−900 °C (Table 8). The needle structure of the petroleum coke is confirmed by the results of scanning electron microscopy obtained using Tescan Vega 3 LMH. Figure 2, for example, shows SEM images of the crude petroleum coke obtained in experiment 7 (Figure 2a,b) and calcined coke (Figure 2c,d). The domains of these cokes have a pronounced anisotropy, a lamellar microstructure formed by thin, long domain-packed lamellae oriented along pore spaces.22 According to the nomenclature given in the ref 5, the microstructure of the petroleum coke of experiment 7 obtained after calcination at 1100 °C can be attributed to the anisotropy of string-circular flow domain anisotropy. This type of anisotropy is characterized by a fibrous structure, disturbed folding of layers, and quite porous structure.
is the width of the diffraction line at half the maximum height (in rad) minus the hardware width of the peak b = 0.2°. The angular position of the reflections (2θ002 and 2θ100) on the radiograph is determined by the corresponding interplanar distance (d002 and d100). Figure 1, by the example of diffractograms of raw and calcined coke of experiments 1, 4, 5, and 7, shows a gradual transition from the disordered structure of petroleum coke obtained at 480−512 °C to crystalline graphite after calcination at 1100 °C. The calcined cokes have the peak (002) with an asymmetric shape, which is caused by the superposition of two peaks on each other.20 The left side of the peak is formed by the coke with a less ordered structure, which corresponds to smaller diffraction angles of 2θ. The right side of the peak is formed by the petroleum coke with a higher degree of graphitization (large angle 2θ). The results of diffractometric analysis and the calculated values for the (002) and (100) reflexes for petroleum cokes produced in experiments 1−7 are given for raw (green) cokes in Table 6 and for calcined in Table 7. With an increase in coking overpressure from 0.15 to 0.55 MPa at a final process temperature of about 500−510 °C, the change in the interplanar distance d002 is ambiguous for raw cokes, but the general trend is its decrease from 3.4609 to 3.4557 Å. In samples of petroleum coke calcined at 1100 °C, the dependence of the decrease in the interplanar distance d002 from 3.5202 to 3.4984 Å with an increase in the excess coking pressure is more distinct. With an increase in coking temperature from 480−488 to 500−510 °C with an overpressure of 0.35 MPa, the interplanar distance d002 increases for both raw and calcined petroleum cokes from 3.4553 to 3.4583 Å and from 3.5092 to 3.5257 Å, respectively. In contrast, the interplanar distance d100 in both cases decreases under the specified conditions from 2.1244 to 2.1187 Å for raw samples and from 2.0999 to 2.0870 Å for calcined samples of petroleum coke. The increase in the interplanar distance d002 during calcining at up to 1100 °C of all seven obtained samples of petroleum cokes is caused by restructuring and thermal expansion. The interplanar distance d002 of petroleum coke4 during heat treatment at 500 to more than 1600 °C has an extreme character with a minimum at a temperature of about 800−900 °C caused by the compression of the crystal lattice during the removal of volatile substances under inert conditions. However, when calcining cokes at a temperature of 1100 °C, the interplanar distance d002 is still lower than at the temperature at the end of the coking process −480 to 512 °C. According to the results of the X-ray phase analysis, one can make a conclusion about the character of the microstructure of petroleum cokes based on the ratio of the average height Lc and the average diameter La of crystallites.21,22 Therefore, the farther the value of this ratio from the unit, the more elongated structure the fibers have and the closer the structure is to the needle coke. For 1−7 raw coke samples obtained during the experiments, the ratio Lc to La varies from about 2 to 2.4. However, for all seven petroleum coke samples calcined at 1100 °C, the very ratio of Lc to La decreases due to a decrease in the average height of the Lc crystallites in the calcined cokes by 36−47% compared to the raw ones. The decrease in the average height Lc of crystallites during calcination is caused by shrinkage phenomena and intensive removal of volatile substances, which is confirmed by their decrease for each of the seven samples of petroleum coke (see Tables 3 and 4). The authors of ref 23 carried out research on the variation of Lc at a
4. CONCLUSIONS The results of the studies described in this work showed that a change in pressure in the range of 0.15−0.55 MPa and temperatures 488−510 °C of the delayed coking process, using the example of decant oil, affects the formation of the microstructure (Lc, La crystallite sizes and interplanar distances, in which case the d002 value decreases and the d100 value increases) and changes in the physicochemical properties of the oil needle coke (the actual density is in the range from 1.19 to 1.62 g/cm3, the volatile-matter value inclines from 7.05 to 4.69%, the ash content value is in the range from 0.44 to 0.50%, and the sulfur content increases from 0.0367 to 0.0679%). After calcination at 1100 °C, the actual density inclines up to 1.94−2.15 g/cm3, volatile-matter inclines to 1.06−2.81%, and the microstructure of the resulting petroleum cokes is described by the stringy-circular flow domain anisotropy.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Viacheslav A. Rudko: 0000-0002-8527-6705 Vladimir G. Povarov: 0000-0001-6710-0514 Ivan O. Derkunskii: 0000-0001-8776-2152 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was complete as a part of the state assignments “Rational use and deep processing of raw hydrocarbon to produce marine fuels and carbon materials”.
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REFERENCES
(1) Zaporin, V. P.; Valyavin, G. G.; Rizvanov, I. V.; Akhmetov, A. F. Decant-Oil Coking Gasoils for Production of Industrial Carbon. Chem. Technol. Fuels Oils 2007, 43, 326−329. (2) Ancheta, J. HYDRO-MPC Technology for Heavy Oil Refining. J. Min. Inst. 2017, 224, 229−234.
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DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
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DOI: 10.1021/acs.energyfuels.9b01439 Energy Fuels 2019, 33, 6373−6379
