Article pubs.acs.org/EF
Characterization of Cokes from Delayed Co-Coking of Decant Oil, Coal, Resid, and Cracking Catalyst Ö mer Gül,*,† Gareth Mitchell,† Roger Etter,‡ Jim Miller,‡ and Caroline E. Burgess Clifford† †
The EMS Energy Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States OptiFuel Technology Group, 901 U.S. Highway, 68 Woodland Center, Maysville, Kentucky 41056, United States
‡
ABSTRACT: The following focuses on the quality of coke produced from delayed coking blends of decant oil, coal, and resid, and it also examines the effect of adding a cracking catalyst to each blend. We also examine the role of coal, resid, and catalyst addition on the formation of green coke, calcined coke, and graphitized cokes. The overall goal was to see if use of lower quality feedstocks could produce marketable coke. The coal sample was cleaned using the best available technology to as low a level of ash yield (as determined by proximate analysis) as possible. Conversion and yield results from the delayed coking of DO, DO/ coal, and DO/resid/coal as well as each reaction using catalyst are discussed. Gas products obtained from the delayed coking experiments were characterized, and results are discussed. Green cokes obtained from different delayed coking processes were evaluated using optical microscopy; the cokes were calcined and graphitized. X-ray diffraction, temperature-programmed oxidation, and proximate/ultimate analyses were used to characterize green coke, calcined coke, and graphitized coke. In general, the green coke generated from the various reaction conditions (DO and DO plus coal) produced a coke that is adequate as an anode grade coke and is suitable as a graphite filler, but because of either the sulfur and/or ash content is not suitable for nuclear graphite production or metallurgical coke. In general, adding catalyst increased the liquid yields, while decreasing the coke/gas yield, and improved the carbon quality, but added to the ash composition. For reactions of DO/coal/resid, the carbon is not suitable for anode grade coke, graphite, nuclear graphite, or metallurgical coke, and addition of catalyst actually decreased the quality of the coke.
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INTRODUCTION We have been working on delayed coking of decant oil and cocoking of decant oil-coal blends, in order to produce liquids that contain cyclic compounds and carbon for other uses (i.e., green coke for use in graphite, anodes, activated carbons, etc.).1−10 The addition of coal to the co-coking feed increased the cycloparaffin, alkyl benzene, and PAH content, which are desired as precursors for thermally stable jet fuels.1−3 Initial evaluations of cokes from co-coking demonstrated that coal mineral matter (i.e., high concentration of silica and iron) found in the coke was one of the main causes for the coke to be unsuitable for use in the aluminum smelting industry even though co-coking cokes met or exceeded the quality of petroleum coke.3,7,9 Interestingly, silica and iron retained in the coke could be useful in making high-quality graphite, as these minerals (silica and iron) are known to catalyze graphite formation via a metal carbide formation, which results in primarily the removal of defects and other local repairs of the structure rather than substantial reorganization of the carbon matrix.11,12 As such, the green coke that is not suitable for anode production may be more suitable for graphite production.11 In research to produce synthetic graphite from anthracite coal, it was shown that inherent mineral matter in the coals may catalyze graphitization.13−17 In addition, the co-coke produced may be suitable for other applications, such as producing metallurgical coke and nuclear graphite. In addition to co-coking of decant oil (DO) and coal to change the chemical character of liquids from delayed coking, OptiFuel has been developing in situ catalytic cracking technology designed to increase delayed coker liquids production and increase coking of the heavy aromatic compounds that are often © 2014 American Chemical Society
responsible for shot coke production. Their technology employed a proprietary catalyst sprayed into the top of the coking drum during filling, and on an industrial scale it has been shown to be responsible for increased yield of naphtha and light cycle gas oil, lower coke yield or effectively increased throughput capacity, while decreasing episodes of shot coke and improved sponge coke production. Our approach in this project was to produce green cokes from our unique laboratory-scale delayed coker from blends of decant oil, resid, coal and catalyst to examine their effects on the coke/ carbons produced relative to those made from DO alone. Typically, DO is used to make high-quality coke (needle coke), which is a raw material in the production of graphite products. The goal is to examine the effect on the coke when adding coal and resid to the decant oil, as addition of these materials has potential to lower the costs of graphite production (i.e., coal and resid are less expensive than “processed decant oil”) using lower quality more readily available feed materials. The proposed addition of catalyst using OptiFuel catalyst technology was expected to improve the quality of the coke produced, particularly when using the lower quality feed materials. The cokes were prepared in a similar fashion to graphite production, to ensure that the green cokes were graphitized and that inherent minerals in the feedstocks and added metals as catalyst were examined as they catalyzed graphite formation. Received: August 7, 2014 Revised: November 15, 2014 Published: December 18, 2014 21
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The following discusses methods for producing quality carbon from blends of decant oil, coal, resid, and catalyst, and it examines the role of these additives on the formation of green coke, calcined coke, and graphitized cokes. The overall goal was to see if a marketable coke could be produced from the use of lower quality feedstocks in the blend with decant oil. Accordingly, our work has focused on evaluating different processing conditions, such as variations in the blend of decant oil, resid, coal, and catalyst.
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Table 1. Properties of the Clean Plant Product (DECS-36) Compared with Beginning (head) and Cleaned Jameson Cell Effluent (JCE-PARC)a Analytical Procedure
DECS-36
Proximate Analysis: (dry) Fixed Carbon, % 58.3 Volatile Matter, % 34.5 Ash, % 7.2 Ultimate Analysis: (dry) Carbon, % 80.8 Hydrogen, % 5.1 Nitrogen, % 1.5 Sulfur, % 1.0 4.4 Oxygen, % (diff.) H/C 0.757 Gieseler Plastometer: Softening Temp, °C 384 Fluid Temp Diff, °C 108 Max. Fluidity (ddpm) 30,000 Temp at Max., °C 448 Ash Mineral Composition: Silicon Dioxide, % 57.38 Aluminum Oxide, % 25.60 Ferric Oxide, % 11.36 Titanium Oxide, % 1.45 Phosphorus 0.23 Pentoxide, % Calcium Oxide, % 1.21 Magnesium Oxide, % 0.93 Sodium Oxide, % 0.72 Potassium Oxide, % 1.87 Sulfur Trioxide, % 0.47 Organic Petrography: (volume %) Total Vitrinite 73.8 Total Liptinite 5.3 Total Inertinite 20.9 Vitrinite Reflectance, % 1.03 Particle Size Distribution (microns) 10% of Particles less nd than 50% of Particles less nd than 90% of Particles less nd than
EXPERIMENTAL SECTION
Materials. The approach to selecting coals for co-coking with petroleum residual streams by the delayed-coking method has involved identifying a source of fine coal composed mostly of vitrinite of a high volatile A bituminous metallurgical coal. The reasons for these restrictions include the fact that vitrinite is the main thermoplastic component of coal that leads to a solid, graphitizable carbon and the plastic temperature range of high volatile A bituminous coals are typically in the range of delayed coker operations. Coals produced for the metallurgical market usually have fine-particle cleaning circuits that typically concentrate vitrinite, but also attracts a significant amount of clay-size aluminosilicate minerals. So even though there may be a readily available source of high-vitrinite-containing fines, they need to be recleaned to become valuable for co-coking.3 A source of high-quality metallurgical coking coal of high volatile bituminous rank being produced in a cleaning plant located in Raleigh County, WV was collected for use in this study. A run-of-cleaning-plant sample (DECS-36) was collected in 2006 from this plant for inclusion into the Penn State Coal Sample Bank and Database as well as a large sample of Jameson cell fines that were deep cleaned and processed to ≤0.9% ash yield (as determined by proximate analysis) by laboratory float-sink methods. However, the new sample of fines collected for this investigation (December 17, 2007) was to be processed more closely to actual cleaning plant practices using best available technology. On the day of collection, the new coal-fines product (JCE-PARC) was being generated from a mixed feed of three coal seams from four different mines that included an 80% blend of Powellton (45%) and Eagle (55%) and a 20% blend of Eagle (64%) with Cedar Grove (36%) seams. The cleaning plant product sample (DECS-36) was stage-crushed, homogenized and packaged for inclusion in to the Penn State Coal Sample Bank. Analyses were completed at Penn State and by Standard Laboratories and are provided in Table 1 for comparison. Processing of the larger Jameson cell sample (JCE-PARC, head sample) employed a Derrick Model K Vibrating Screen Machine that combines vibration and wet sieving to effect separation of fine-size particles. The Jameson cell sample was processed through a 147 cm × 44 cm (58″l × 17.5″w) screen with openings of 53 μm that was adjusted to 15° from horizontal and vibrated at 3600 cycles per minute. A high-pressure spray of water was maintained across the entire width of the screens and the >53 μm fraction was collected as the clean coal product, i.e., the material that would simulate best available technology currently being used by industry. The higher ash yield 538 1.05 260
SimDist GC analysis, and SimDis Expert 6.3 software was used to calculate the percentage of fractions. Tables 4 and 5 show SimDist-GC cut point distribution and boiling point distribution results for decant oil feedstock (EI-107), respectively. Nuclear Magnetic Resonance. 1H and 13C NMR analyses, using a Bruker AMX 360 NMR spectrometer operating at 9.4 T, were performed on the EI-107 DO sample. The samples was dissolved 1/1 volume ratio in deuterated chloroform (CDCl3) containing 1 vol % of tetramethylsilane (TMS) as standard. The pulse width was 5 μs, pulse delay of 5 s for 1H with a 90° tip angle and 5 μs pulse width and a pulse 22
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introduction to the coker ∼4−5 h. At the conclusion of each experiment, the coke drum was maintained at temperature for an additional 2 h with steam stripping to ensure carbonization of nonvolatile components and to remove the trapped volatile components from the coke. The conditions and product distributions for coking and co-coking experiments are detailed in Table 6. The normalized gas composition data (normalized without nitrogen/oxygen) are reported in Table 7. The feed in these experiments was continuous and measured gravimetrically with time. The feed was initially charged to a heated feedstock vessel that was continuously mixed throughout the co-coking experiment to achieve and maintain homogeneity. The feedstock vessel was placed on a balance for monitoring the feeding rate. The temperature of this vessel was kept at 66 °C; when resid was used, the temperature was increased to 120 °C. Feed was heated in the lines prior to the preheater to ∼120 °C, and then to ∼460 °C in the preheater. Heated feedstock from the preheater was fed to the coker drum. Note that the coke drum inlet temperature (Table 6) was higher than the thermoplastic resolidification temperature of the coal employed in this investigation (Table 1). Light hydrocarbons that exit from the top of coker drum pass through a series of condensers where liquid products were separated from gas. Gas flowed through an additional chilled condenser, a burnished filter having two micron openings to a vent outfitted with a bag sampling port. Two to three bag samples were taken during each run using a valve after mass flow meter (Figure 1). Gas was analyzed using Shimadzu GC-17A that combined FID for hydrocarbon analysis and TCD for carbon oxide determination in separate columns for the suite of gases listed in Table 7. Because nitrogen gas was used as a propellant for the catalyst slurry, gas samples from the catalytic runs had much higher nitrogen and oxygen contents, making comparison with noncatalytic runs more difficult. In order to compare the effect of catalyst on the gas compositions, the nitrogen and oxygen contents were subtracted and the gas composition was normalized, so the average values for each run are reported in Table 7. For the catalytic delayed coking or co-coking experiments, a slurry of catalyst and decant oil was prepared of a consistency that could be sprayed into the coking chamber through an orifice at the top of reactor using equipment obtained from Spray Systems, Inc. The slurry was injected at 5 s intervals, using nitrogen to push the catalyst slurry out of the needle and to clean the needle to prevent coke formation that may plug the injection system. The silica-based catalyst provided by Albemarle, Inc., was a proprietary formulation designed to retrieve more liquids from the delayed coking process and was expected to influence the quality of the graphitized coke. Because of the method of delivery it was not possible to determine precisely the amount of catalyst that was added. However, from the increase in coke ash yield it may have varied between 3−12g or 0.05−0.26 wt % of the feed. Coke Characterization. Optical Microscopy of Green Coke. An evaluation of the distribution of coke textural elements was performed under reflected polarized white-light microscopy using oil immersion at 625× magnification. Because no standard technique exists, the procedures used in this evaluation involved point-counting specific size textural elements from a polished surface of a representative coke sample. The procedure used was dictated by and developed for the cokes generated during this investigation. Cokes were extracted from the PSU coker as competent cylinders 7.5 cm in diameter (and of variable length), which were crushed and homogenized to meet other analytical requirements defined by project objectives. Each coke was stage crushed to pass a 20-mesh sieve (0.85 mm) and split so as to obtain three aliquots of about 25 g each. One of the aliquots was prepared for optical microscopy at 20-mesh (0.85 mm), another was crushed to pass a 60-mesh (0.25 mm) sieve to be used for proximate, ultimate and sulfur analyses, and the remaining split was provided for calcinations and graphitization. The remainder of each coke was stored under an inert atmosphere in foil laminate bags. Specimens for optical microscopy were split to about 20 g of −20 mesh coke, placed in a 2.5 cm diameter plastic tube, impregnated with a cold setting epoxy resin by stirring and placing them under vacuum and then placed in a centrifuge to establish a density/particle-size gradient. Vacuum impregnation effectively forces epoxy to replace the connected air-filled voids in the coke, whereas those voids not connected to the
Table 3. Ultimate and Proximate Analyses Results for EI-107 EI-107 C, wt % (daf) H, wt % (daf) N, wt % (daf) S, wt % (daf) O, wt % (by difference)
88.55 6.86 0.03 2.99 1.57
Atomic ratio (H/C)
0.921
Ash % Volatile Matter % Fixed Carbon %
0.027 95.94 4.03
API Gravity (60 F)
−4.4
1 H NMR Total Aromatics Total Aliphatics
43.1 56.9
13
C NMR Total Aromatics Total Aliphatics
74.5 25.5
Table 4. Simulated Distillation GC Cut Point Distribution Results Feed
IBP-180° IBP-356 °F Gasoline
180−270 °C 356−518 °F Jet fuel
270−332 °C 518−630 °F Diesel
332-FBP °C 630-FBP °F Fuel oil
EI-107
0.02
0.83
6.60
91.59
Table 5. Simulated Distillation Boiling Point Distributions of Decant Oils %Distillation
EI-107
IBP 10 20 30 40 50 60 70 80 90 FBP
173.6 336.8 350.9 364.0 376.5 391.3 426.4 426.4 452.4 497.6 569.3
delay of 45 s for 13C with a 70° tip angle were used to ensure quantitative results. Delayed Coking Apparatus. The large laboratory-scale delayed coker (LSDC) consisted of a 7.5 cm ID × 102.5 cm cylindrical reactor unit having an internal volume of approximately 4.5 L. The preheater was a 2.5 cm OD × 51 cm stainless steel tube fitted directly to the bottom of the reactor. This was fed by a 0.95 cm (3/8″) OD feed line that was outside the furnace and was heated to ∼120 °C using heating tape. The temperature gradient through this 51 cm preheater is was on the order of 200 °C, with an outlet temperature of 432−441 °C. This was connected to a 0.64 cm (1/4″) OD line that carried feedstocks from the feed pump. Further details of the design and construction of this unit, and initial results, can be found elsewhere.1−3 The delayed coker schematic used for coking is shown in Figure 1. Delayed Coking Reaction Procedures. The following operating conditions were used: coke drum inlet temperature ranged from 479 to 485 °C, coke drum pressure 25 psig, slurry feed rate 16.7 g/min, and feed 23
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Figure 1. Schematic of large, laboratory-scale coker.
Table 6. Data for Conditions and Product Distributions of Coking Experimentsa
a
Run #
130
129
131
133
134
135
Decant oil (%) Coal (%) Resid (%) Cracking catalyst Conditions Feedstock, hours Reactor Pressure (psig) Hold at 500 °C, h Feed rate, g/min Preheater inlet, °C Preheater outlet, °C Coke drum inlet, °C Coke drum lower/middle, °C Coke drum top, °C Material Fed to Reactor (g) Product Coke + liquid product (g) Liquid/coke Coke, wt % Liquid, wt % Gas, wt % by diff Cylinder of Coke Length (cm)
EI-107 (100%) no
EI-107 (80%) JCE-PARC (20%) no
EI-107 (60%) JCE-PARC (20%) Flying J (20%) no
EI-107 (100%) yes
EI-107 (80%) JCE-PARC (20%) yes
EI-107 (60%) JCE-PARC (20%) Flying J (20%) yes
5h 25 2 w/ss* 16.7 120 456 485 471 439 5319
4 h 33 min. 25 2 w/ss 16.7 120 474 484 469 443 4405
4 h 50 min. 25 2 w/ss 16.7 125 460 484 468 435 4810
5h 25 2 w/ss 16.7 122 429 480 466 429 5191
4 h 25 min 25 2 w/ss 17.0 136 413 483 473 434 4540
2 h 15 min 25 2 w/ss 18.0 129 404 479 468 423 2447
4930 3.57 20.3 72.4 7.3 26.7
4010 2.03 30.0 61.0 9.0 34.0
4513 2.09 30.4 63.4 6.2 broken
4880 5.68 14.1 79.2 6.0 broken
4310 2.94 24.1 70.8 4.9 26.7
2360 2.93 24.5 71.9 3.6 17.8
w/ss*= with steam stripping.
exterior surface remain unfilled. After the epoxy hardened, the samples were cut longitudinally to expose the particle gradient, remounted in epoxy and ground and polished using a series of silicon carbide grit papers (400 and 600 grit) and alumina polishing slurries (0.3 and 0.05 μm). All cokes were inspected using a Zeiss Universal research microscope with a 40× (625× total magnification) Antiflex oil immersion objective using crossed-polarized white-light illumination. The Antiflex system
can be used to impose retardation that results in primary and secondary coloration which helps define optical texture. Photomicrographs were taken using an AxioCam 2 megapixel digital camera of representative areas to describe the textural nature of each coke (Figures 2−7). Eleven different components were identified in the cocarbonization residues as described below. 24
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Table 7. Average Gas Composition of Delayed Coking of All the Reactions, Normalized To Remove Excess Nitrogen and Oxygen Compound
130
129
131
133
134
135
Methane, % Ethane, % Propane, % Butane, % Pentane, % Hexane, % Hydrogen, % Carbon Monoxide, % Carbon Dioxide, %
76.41 11.52 2.00 0.46 0.16 0.15 9.17 0.10
70.34 11.95 2.09 0.44 0.09 0.17 13.72 0.65
64.53 14.35 4.49 1.40 0.60 0.78 12.30 0.91
72.69 10.63 1.96 0.47 0.18 0.26 13.63 0.10
69.00 11.12 2.27 0.48 0.21 0.30 15.05 0.86
61.33 15.04 5.08 1.71 0.69 1.15 13.38 0.92
0.04
0.54
0.65
0.08
0.72
0.69
Figure 3. Optical microscopy of green coke from #133. Plate II. Optical textures characteristics of delayed coke made from EI-107 decant oil with added catalyst, run #133: (A) The dark reflecting, nearly spherical catalyst particle (∼72 μm diameter) is observed as trapped in small domain and domain carbon textures; (B) An irregularly shaped catalyst particle of ∼56 μm diameter observed trapped in small domain and mosaic texture carbon; (C) Although most of the catalyst particles observed in this coke were isolated, there were occasional aggregations of many particles, such as that shown in this photograph. (D) Flow domains bending around or incorporating a catalyst particle.
Figure 2. Optical microscopy of green coke from Run #130. Plate I. Optical textures characteristics of delayed coke made from EI-107 decant oil, run #130. (A) Small domain (10−60 μm) and mosaic (60 μm) carbon texture; (D) Flow domain texture characterized by being >60 μm long and less than 10 μm wide.
Petroleum Fraction-Derived Textures. Isotropic: A relatively low reflecting, purple carbon material derived from decant oil or resid that displays little or no optical activity when rotated under polarized light. Mosaic: A higher reflecting carbon textural element identified from decant oil and resid materials that displays optical anisotropy and is characterized by isochromatic units of DO/Coal/Resid. TPO of Green Cokes, Calcined Cokes, and Graphitized Cokes. The TPO of green coke, calcined coke, and graphitized coke for each delayed coking run without and with catalyst are compared in Figures 8−13, with temperatures of the main peaks shown on the spectrum. It can clearly be seen that green cokes were composed primarily of amorphous carbon (peaks ranging between 510 and 525 °C), while calcined coke had filamentous/ encapsulated carbon and some crystalline graphite platelets (peaks ranging 710−825 °C), while graphitized coke was mostly comprised of crystalline graphite platelets (ranging between 810 and 900 °C). Catalyst addition into the coking system changed the coke formation and affected the TPO profiles of calcined and graphitized coke samples. For example, the TPO profiles of green, calcined, and graphitized cokes obtained from the delayed coking of DO alone without catalyst are different than the cokes obtained in the presence of catalyst (compare Figures 8 and 9). Coke generated from DO in the presence of catalyst appeared to have developed crystalline graphite platelets at calcination reaction temperature (Figure 9). Addition of 20% coal to DO in the presence of catalyst produced a better quality graphitized coke than the coke obtained without catalyst (compare the graphitized coke TPO profiles in Figures 10 and 11). The further addition of resid and coal to DO seemingly produced a better quality graphitic carbon, but a lower quality calcined carbon in terms of TPO (compare Figures 12 and 13). XRD Results of Green Cokes, Calcined Cokes, and Graphitized Cokes. The XRD spectra of the green, calcined, and graphitized cokes for run #129 are compared in Figure 14, and they provide some general information (each XRD spectrum for each reaction is similar in shape), while detailed analyses of all of the spectra are summarized in Tables 10−12. From Figure 14, the spectrum for the green coke and, in particular, the [002] peak at 2θ = 26° is broad and ill-defined and indicates a relatively amorphous material. When the sample was calcined, the [002] peak becomes slightly more defined, and the diffraction peaks at ∼45, 53, and 80° begin to emerge, suggesting the cokes are beginning to graphitize. When the sample was calcined and graphitized, XRD revealed better definition of the peaks at ∼45, 53, 78, 83, and 88°, and a better three-dimensional carbon lattice. More detail is revealed when evaluating the d-spacing of the [002] peak and the Lc of all the samples, and the d-spacing of the [002] peak, Lc, La, and the degree of graphitization (g) (Tables 10−12) of the graphitized carbons.24,25 Table 10 compares the d002 of all the samples. As with the TPO, the d002 of the green
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CONCLUSION This paper has focused on the quality of coke produced when delayed coking blends of decant oil, coal, resid; it also examined the effect of adding a cracking catalyst to each blend. We also examined the role of coal, resid, and catalyst addition on the formation of green coke, calcined coke, and graphitized cokes. The overall goal was to see if use of lower quality feedstocks could produce marketable coke. The foundation of coking blends used in this study was the EI107 decant oil (DO) obtained from United Refining. Ultimate and proximate analyses and 1H and 13C NMR analyses showed the DO to be fairly aromatic, which upon carbonization 33
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(4) Aksoy, P. G. Removal of SO2 and NOX over coal-petroleum based activated carbons. Final Report, For Award No.: DE-FC26-03NT41874, 3152-TPSU-DOE-1874, November 1, 2007. (5) Gafarova-Aksoy, P.; Mitchell, G. D.; Burgess-Clifford, C.; Rudnick, L. R.; Schobert, H. H. ACS Division of Petroleum Chemistry Preprints 2006, 51 (2), 318−321. (6) Gül, Ö .; Burgess Clifford, C. E.; Rudnick, L. R.; Schobert, H. H. ACS Division of Petroleum Chemistry Preprints 2006, 51 (2), 342−347. (7) Clifford, C. E. B.; Griffith, J.; Gül, Ö .; Aksoy, P. G.; Mitchell, G. Production of coal-based fuels and value-added products: coal to liquids using petroleum refining solvents; 32nd International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, FL, June, 2007. (8) Gül, Ö .; Clifford, C. E. B.; Rudnick, L. R.; Schobert, H. H. Salt Lake City, UT, 237th National Meeting & Exposition, ACS Division of Fuel Chemistry Preprints, 2009, 54 (1), 332−335. (9) Clifford, C. E. B.; Gül, Ö .; Griffith, J.; Aksoy, P. G.;Mitchell, G.; Escallón, M. M.; Suriapraphadilok, U.; Nyathi, M. S.; Zhang, J.; Schobert, H. H. Coal-to-liquids processes for production of transportation fuels, carbons, and coal-based pitch; 34th International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, FL, June, 2009. (10) Gül, Ö .; Rudnick, L. R.; Scalise, A.; Clifford, C. E. B.; Schobert, H. H. 23rd Annual International Pittsburgh Coal Conference, Pittsburgh. September 25−28, 2006, 45 (1), 1−11. (11) Oya, A.; Marsh, H. J. Mater. Sci. 1982, 17, 309−322. (12) Nyathi, M. S.; Burgess, C. B.; Schobert, H. H. Fuel 2013, 114, 244−250. (13) Pappano, P. J.; Mathews, J. P.; Schobert, H. H. Preprints, Am. Chem. Soc. Div. Fuel Chem. 1999, 44, 567. (14) Andrésen, J. M.; Burgess, C. E.; Pappano, P. J.; Schobert, H. H. Fuel Proc. Technol. 2004, 85 (12), 1373. (15) Conrad, B. Anthracite Feedstocks for Specialty Graphite Production. Final Report for CPCPC, DOE Prime Award No.: DEFC26-98FT40350, July 1, 2000. (16) González, D.; Montes-Morán, M. A.; Garcia, A. B. Energy Fuels 2005, 19, 263. (17) Pappano, P. J. Ph.D. Thesis, The Pennsylvania State University, University Park, PA, 2003. (18) McCarty, J. G.; Hou, P. Y.; Sheridan, D.; Wise, H.; Albright, L. F.; Baker, R. T. K. ACS Symposium Series 202; American Chemical Society: Washington, DC, 1982; Chapter 13, p 253. (19) Altin, O.; Eser, S. Ind. Eng. Chem. Res. 2000, 39, 642−645. (20) Altin, O.; Eser, S. Ind. Eng. Chem. Res. 2001, 40, 589−595. (21) Altin, O.; Eser, S. Ind. Eng. Chem. Res. 2001, 40, 596−603. (22) Gul, O.; Rudnick, L. R.; Schobert, H. H. Energy Fuels 2006, 20 (6), 2478−2485. (23) Burgess Clifford, C. E.; Gul, O., Principle Investigators. Production of graphite from coke obtained from delayed coking of decant-oil blends. CPCPC Final Report, Grant No. DE-FC2603NT41874, Internal Agreement No. 3550-TPSU-DOE-1874, March 1 − October 31, 2009, December 31, 2009. (24) Maire, J., Mering, J. Chemistry and Physics of Carbon.; Marcel Dekker: New York, 1970; Vol. 6, p 125. (25) Atria, J. V.; Rusinko, F.; Schobert, H. H. Energy Fuels 2002, 16, 1343−1347.
generated large and elongated textures that generally would be observed in needle coke. To this base was added a coal fraction that was prepared using the best available technology at the time of preparation (ca. 2006) to generate a clean coal of 2.3% ash yield and that contained a high concentration of vitrinite. It was important to have a high concentration of vitrinite from a highquality coking coal that possessed significant thermoplastic properties for there to be a chance of coal being incorporated into coke generated from the DO. In addition, vacuum petroleum residuum procured from Flying J was used as a second additive that would be encountered during most delayed coking processes. To this has been added a silicon-based cracking catalyst that was developed to increase liquids output from the delayed coker while influencing the type of coke being generated. For the reactions of DO alone, carbonization produced a coke that is adequate as an anode grade coke or a graphite filler, but because of either the sulfur and/or ash content, it would not be suitable for nuclear graphite production or metallurgical coke. Adding catalyst increased the liquid yield while reducing the coke and gas yield, improved the carbon quality slightly, and added a little more to the ash composition. For reactions of DO/coal, carbonization produced a coke that is marginally good enough for anode grade coke and graphite filler, although the ash and sulfur content are too high for these applications; without some removal of minerals, this coke would not be suitable for nuclear graphite production or metallurgical coke. Adding catalyst increased the liquid yield, improved the carbon quality, and added to the ash composition. For reactions of DO/coal/resid, the carbon is not suitable for any of these applications, and addition of catalyst, while increasing the liquid yield, decreased coke quality. However, these cokes are of suitable carbon quality (and better than some petroleum cokes) that they could be blended with petroleum cokes or demineralized to mitigate the ash and sulfur content.
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AUTHOR INFORMATION
Corresponding Author
*Present Address: GrafTech International, 12900 Snow Rd., Parma, OH 44130. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors would like to thank Consortium for Premium Carbon Products from Coal for financial support for this project (Grant No. DE-FC26-03NT41874). We would also like to thank Bradley Maben for his assistance with the delayed coker operations and Ron Wasco for conducting proximate and ultimate analyses.
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REFERENCES
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dx.doi.org/10.1021/ef501767w | Energy Fuels 2015, 29, 21−34
