Coking Tests Research Articles

Modification mechanism of caking property of polystyrene waste using low-temperature pyrolysis and its use in coal-blending coking

Polystyrene (PS) waste was depolymerized using a low-temperature pyrolysis treatment (LTPT) to increase its caking index. The mechanism of caking index modification was revealed by using Fourier transform infrared spectroscopy, thermogravimetric (TG) analysis, pyrolysis-gas chromatography with mass spectrometric detection, and solid-state 13C nuclear magnetic resonance spectroscopy. The crucible coal-blending coking tests were carried out using an industrial coal mixture and the treated-PS with the highest caking index (PS300) or raw PS. Some properties of the resultant cokes were also analyzed. It was demonstrated that the caking index of PS dramatically increased by LTPT; however, exceeding 300 °C did not yield any benefit. The caking index increased due to the formation of the caking components, whose molecules are medium in size, caused by LTPT. Additionally, the coke reactivity index of the coke obtained from the mixture containing PS300 decreased by 5.1% relative to that of the coke made from the mixture with PS and the coke strength after reaction index of the former increased by 7.3% compared with that of the latter, suggesting that the ratio of depolymerized PS used for coal-blending coking could increase relative to that of PS.

Ignition of Aged Lubricants in a Shock Tube

Abstract Lubricants experience harsh conditions which result in degradation of the oil. To imitate similar conditions, Mobil DTE 732, a common gas turbine lubricating oil, was subjected to high temperatures for an extended period of time, until thermal degradation occurred, indicated through the creation of coke. Samples were taken throughout this process, with the sample that was tested having been exposed for 78 hours. Utilizing an endwall injector system, the samples were ignited behind reflected shock waves in the High-Pressure Shock Tube at Texas A&M University. The injector system utilizes the incident wave to increase the temperature of the lubricant past its vaporization temperature, thereby vaporizing the fuel prior to the arrival of the reflected shock. Using this system, the base Mobil DTE 732 and the 78-hour sample produced from the coking test were tested at 1.06 to 1.58 atm and between 1171 and 1373 K. The ignition delay times of the samples were recorded utilizing pressure rise and hydroxyl chemiluminescence located in the sidewall of the shock tube. Upon the analysis of the results, there were negligible changes in the ignition behavior of the fuel, based on ignition delay time. However, changes in the combustion behavior were experienced, such as an absence of two-stage ignition and lower viscosity for the post-coke sample.

Method for assessing the anti-carbon properties of unmanned aerial vehicle engines

At present, the process of design and production of unmanned aerial vehicles has been making progress in Russia, which is caused by the relatively low cost, small size, absence of life hazard to a pilot, stealth, self-sustainability, mobility compared to manned aircraft. At the same time, two-stroke gasoline engines, possessing a higher power-to-volume ratio, unsophisticated design, and lower production costs in comparison with four-stroke gasoline engines, have become widely used in these aircraft. These engines lack a conventional lubrication system, so the oil is supplied to lubricate the cylinder-piston group in the form of a fuel-oil mixture, which burns during the operating procedure together with the fuel. In this case, high-temperature deposits such as carbon and lacquer are accumulated on the parts of the cylinder-piston group. The formation of carbon reduces the engine power, its service life and efficiency, causes an increase in operating costs. One of the solutions to this problem is the use of motor oils with a high level of anti-carbon properties. However, currently a method for assessing the anti-carbon oil properties for unmanned aerial vehicle engines is not available. In accordance with the described chemmotological process, the method was developed, the test equipment (Panel Coking Test Apparatus) was selected and the test modes were established (plate temperature – 290°C, oil temperature in the crankcase – 100°C, spray speed – 800 rev/min, test time – 4 h), allowing you to evaluate and rank motor oils for unmanned aircraft engines based on the anti-carbon properties in the laboratory. As tested, Motul Kart Grand Prix 2T oil has the least tendency for carbonization among tested motor oil samples. Laboratory and bench tests of Novoyl-DD and Motul Kart Grand Prix 2T oils show a high degree of convergence.

Coking Test Using Jet A-1 and Desulfurized Kerosene in a Regenerative Cooling Channel Environment

Coking Test Using Jet A-1 and Desulfurized Kerosene in a Regenerative Cooling Channel Environment

Anti-coking and anti-carburizing behavior of amorphous AlPO4 coating

The aim of the present study was to examine the anti-coking and anti-carburizing behavior of amorphous AlPO4 coating. So, aluminum phosphate composition was synthesized by sol-gel process and applied on the AISI 304 stainless steel by dip coating technique. Anti-coking performance was examined in a tube furnace at 1000 °C for 30 min under Ethane (C2H6) atmosphere. Carburizing test was performed in a sealed charcoal medium at 1100 °C for a total of 30 h exposure time. Phase composition of the samples was analyzed by X-Ray Diffraction (XRD) after coking and carburizing tests. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) were employed to study the morphology and elemental analysis of the samples after coke and carbon formation experiments. Microhardness indenter was applied on the cross section of the carbon-exposed specimens to plot the hardness profile through the carburizing zone. The results of the coking experiment revealed catalytic coke formed on the uncoated surface, while irregular spherical coke with no trace of catalytic coke was formed on the coated surface, indicating the great anti-coking performance of the amorphous AlPO4 coating. The results of pack-carburizing test demonstrated that the thickness of the carbide layer formed on the bare surface was ∼10 times greater than that of the coated sample. Hardness measurement for the amorphous AlPO4 coated sample detected lower values compared to those for the uncoated one at all distances from the surface, indicating less carbon diffusion occurred beneath the coated surface. In overall, the results declared that the amorphous AlPO4 coating could be a good candidate for surface protection of stainless steel against catalytic coke formation and carbon diffusion.

Speciation and thermal transformation of sulfur forms in high-sulfur coal and its utilization in coal-blending coking process: A review

The utilization of high-sulfur coal is becoming more urgent due to the excessive utilization of low-sulfur, high-quality coal resources, and sulfur removal from high-sulfur coal is the most important issue. This paper reviews the speciation, forms and distribution of sulfur in coal, the sulfur removal from raw coal, the thermal transformation of sulfur during coal pyrolysis, and the sulfur regulation during coal-blending coking of high organic-sulfur coals. It was suggested that the proper characterization of sulfur in coal cannot be obtained only by either chemical method or instrumental characterization, which raises the need of a combination of current or newly adopted characterization methods. Different from the removal of inorganic sulfur from coal, the organic sulfur can only be partly removed by chemical technologies; and the coal structure and property, particularly high-sulfur coking coals which have caking ability, may be altered and affected by the pretreatment processes. Based on the interactions among the sulfur radicals, sulfur-containing and hydrogen-containing fragments during coal pyrolysis and the reactions with minerals or nascent char, regulating the sulfur transformation behavior in the process of thermal conversion is the most effective way to utilize high organic-sulfur coals in the coke-making industry. An in-situ regulation approach of sulfur transformation during coal-blending coking has been suggested. That is, the high volatile coals with an appropriate releasing temperature range of CH4 overlapping well with that of H2S from high organic-sulfur coals is blended with high organic-sulfur coals, and the C–S/C–C bonds in some sulfur forms are catalytically broken and immediately hydrogenated by the hydrogen-containing radicals generated from high volatile coals. Wherein, the effect of mass transfer on sulfur regulation during the coking process should be considered for the larger-scale coking tests through optimizing the ratios of different coals in the coal blend.

Experimental Analysis of Injector Nozzle Coking on Multi-Cylinder Diesel Engine Considering Worst-Case Operating Conditions Including Engine Exhaust Brake

<div class="section abstract"><div class="htmlview paragraph">Injector nozzle coking can severely limit engine performance by limiting the amount of fuel delivered to the combustion chamber and altering the spray pattern. Injector nozzle coking is also one of the most sensitive measures of diesel fuel quality. Formation of deposits within the holes of the injector nozzle or on the outside of the injector nozzle may have an adverse effect on overall system performance.</div><div class="htmlview paragraph">There is no single factor that results in nozzle coking but can be classified in four major areas e.g. spray hole geometry, application duty cycle, nozzle localized temperature and the fuel quality.</div><div class="htmlview paragraph">This paper provides a critical review of the current understanding of the main factors affecting the deposit formation. Engine was tested by motoring dynamometer using test cycle generated by Cummins Inc, as an attempt to try to simulate field conditions. This cycle involves test conditions like running engine at maximum power, maximum engine braking condition, cycling between high & low loads and engine shut down and restart for definite time to achieve a soak period, different load and braking conditions.</div><div class="htmlview paragraph">For injector nozzle coking test the fuel shall be blended with a specified oil to achieve a required concentration of Zn ppm to accelerate coking.</div><div class="htmlview paragraph">The intention of doing this experimental analysis was to check the robustness of nozzle configuration to prevent nozzle coking under worst conditions. After the complete injector coking experimental analysis, test cell results indicate 1.26% average injector nozzle coking with injector open loop vs. 0.64% average with injector close loop which was well within 5% of cup flow loss, which is acceptable.</div></div>

An investigation on anti-coking behavior of gas phase aluminide coatings applied on a high performance micro alloyed (HP-MA) steel

In this study, aluminide coatings were applied on a high performance micro alloyed (HP-MA) steel through a gas phase aluminizing process in order to investigate anti-coking performance of the coated steels. In this regard, powder mixtures with compositions of 10% Al-5% NH4Cl-85% Al2O3 and 30% Al-15% NH4Cl- 55% Al2O3 were used for the coating process, hereafter named Al-10 and Al-30 coatings, respectively. The anti-coking performance of the specimens was evaluated using a simulated cracking setup. In this setup, specimens were placed in a tube furnace, exposed to Ethane (C2H6) and Argon gases as the primary feedstocks, using optimized parameters. Results of the coking test showed that the bare steel was largely covered with catalytic coke; while enhanced performance was observed for the gas phase aluminide coated steels. Formation of catalytic coke on the bare steel was due to the reaction between feedstocks and active substrate elements such as Fe and Ni. In fact, the released carbon during the cracking process diffuses into the bare steel, and removes metal crystals from the surface by its outward growing, which eventually led to the formation of catalytic coke. Besides, it was observed that the Al-30 coating had superior performance than the Al-10 coating. In fact, for the Al-10 coating, the amount of catalytic coke was reduced as compared to the bare steel, while the Al-30 coating was mainly covered with spherical carbon deposits, released from chemical reactions in the gas phase. In this regard, the anti-coking ratios of the coatings were 63 and 80%, for Al-10 and Al-30 coatings, respectively. This was mainly due to the higher content of Al and Cr, in the Al-30 coating.

Mass and Elements Balance of Polish and Czech Hard Coal Pyrolysis Process

Laboratory coking test is very often used for prediction of produced coke quality. The second route for results utilisation is differentiation of products and determination of its yield. There were not carried out many tests to check if mass balance sums to one. In addition to this there were not performed test to control elements balance if there were made further ultimate analysis of products. In order to control mass and elements balance there were carried out laboratory coking tests of several coals with ultimate analysis of coals, coke and by-products. There were found good correlations between some products and volatile matter in origin coal. It confirms that for them there is rational for its prediction from quality parameters of coal.

Comparison of Growth Characteristics and Properties of CVD TiN and TiO2 Anti-Coking Coatings

Coating metals with anti-coking materials inhibit their catalytic coking and are especially beneficial in the pyrolysis of hydrocarbon fuels. It is believed that growth characteristics and properties may play a pivotal role in the anti-coking performance of chemical vapor deposition (CVD) coatings. In this study, TiN and TiO2 coatings were obtained by CVD using TiCl4–N2–H2 and TiCl4–H2–CO2 systems, respectively. The effects of deposition time, residence time, and partial pressure were examined, and the coating microstructure was characterized by scanning electron microscopy (SEM). The results reveal that the effect of deposition parameters on the growth characteristics of TiN and TiO2 coatings is very different. The growth of the TiN coating shows characteristics of the island growth model, while the TiO2 coating follows the layer model. In general, the growth rate of the star-shaped TiN crystals is higher than that of crystals of other shapes. For the TiO2 coating, the layer mode growth characteristics indicate that the morphology of the TiO2 coating does not change significantly with the experimental conditions. Coking tests showed that the morphology of non-catalytic cokes is not only affected by the temperature, pressure, and coking precursor, but is also closely related to the surface state of the coatings. Both TiN and TiO2 coatings can effectively prevent catalytic coking and eliminate filamentous cokes. In some cases, however, the N or O atoms in the TiN and TiO2 coatings may affect common carbon deposits formed by non-catalytic coking, such as formation of needle-like and flaky carbon deposits.

Produce Low Aromatic Contents with Enhanced Cold Properties of Hydrotreated Renewable Diesel Using Pt/Alumina-Beta-Zeolite: Reaction Path Studied via Monoaromatic Model Compound

In this present work, Hydro-dearomatisation of toluene and hydro-isomerisation of n-hexadecane (n-C16) in ultralow sulphur diesel (ULSD) using Pt-Cl/H-Beta and Pt/H-Beta catalyst was investigated in a continuous down-flow trickle-bed reactor (DFTBR), and the physicochemical properties of products were studied. The catalytic effect on 40:60 wt% of H-beta-zeolite (H-β) and binder–aluminahydrochlorite extruded was characterized in scanning electron microscopy, nitrogen adsorption and coke testing. The study showed that 80 to 95 wt% of middle distillates recovered in ULSD on elevated temperature between 230 and 270 °C at 5 MPa. With a higher residence time of feed, the middle distillate recovered with 2.2 v/v% of aromatics and −32 °C of cloud point. In the model compound investigation of toluene and n-C16, it was observed that absorption of aromatic ring inhibits the rate of isomerisation; particularly it reduces the yield of branching and rearrangement of n-C16. Also, Cl-incorporated H-β extrudate enhanced the ring saturation and suppressed the reaction path in oligomerisation and cyclisation of paraffin. This methodology achieved asingle-stage upgrading technique involved in the delivery of commercial diesel in the market with low cloud point and aromatic content.

Effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour during light naphtha thermal cracking

AbstractThe investigation was aimed at evaluating the effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour at the surface of HP40 alloy during thermal cracking of light naphtha. The surface morphology and composition of the selectively oxidized alloy were characterized by SEM, EDX, and XRD. Coking tests show that the coking rate of blank alloy decreased with sulphur/phosphorus‐containing compounds, while the effect of sulphur/phosphorus‐containing compounds on coking rate for selectively oxidized alloy is complex, and a mass concentration of µg/g results in the lowest coking rate. The morphology and microstructure of cokes were investigated by SEM and Raman spectra. SEM and Raman spectra analyses indicated that either selective oxidation or sulphur/phosphorus‐containing compounds resulted in more disordered graphite structures and amorphous carbon.

Coking Study of Nickel Catalysts Using Model Compounds

The tendency of coke formation was investigated using nickel catalysts supported on calcium and barium hexaaluminates, compared with a commercial catalyst of natural gas steam reforming. It was developed a methodology in a microactivity unit using cyclohexane as model compound and hydrogen as gas carrier, at low temperature (300–500 °C). After the coking tests, the catalysts were characterized by elemental analysis (CHN) and thermogravimetric analysis using air and steam. 6NiO-BaAl presented the lowest coke removal rate with air. After that, the methodology was modified for ethanol and acetic acid, important model compounds used in studies of biofuels, steam reforming and bio-oil pyrolysis. All model compounds lead to carbon formation with the same chemical nature, as indicated by the temperature of the oxidation peak. So, the methodology can be used as a tool for selection of catalysts. Additionally, cyclohexane and acetic acid are ideal model compounds, because of the lowest and highest coke removal rates with air.

Characterization of Metallurgical Coke Produced with Coal Mixtures and Waste Tires

The use of scrap tires in the coal blends is an alternative to reduction of coke production costs as well as mitigates the impact caused by tire accumulation in the environment. Tests were carried out on a pilot scale, with coal blends and waste tire in 4 levels and 3 particle sizes, in order to assess the impact on the produced coke quality, especially on the Strength after Reaction with CO2 - CSR and Drum Index (DI150-15). In addition, it evaluated the mechanical resistance to compression, punctual chemical composition by Energy Dispersive Spectroscopy (EDS) analysis beyond the carbonaceous matrix-tire interface by SEM microscopy. The results from the coking tests showed that addition of up to 3% of the average ground tire (20-30mm) with steel mesh, raised either as CSR DI150-15, making feasible added also from a technical point of view.

Properties of oxide films grown on 25Cr20Ni alloy in air-H2O and H2-H2O atmospheres

The oxidation kinetics, surface morphology and phase structure of oxide films grown on 25Cr20Ni alloy in air-H2O and H2-H2O atmospheres at 900 °C for 20 h were investigated. The anti-coking performance and resistance to carburization of the two oxide films were compared using 25Cr20Ni alloy tubes with an inner diameter of 10 mm and a length of 850 mm in a bench scale naphtha steam pyrolysis unit. The oxidation kinetics followed a parabolic law in an air-H2O atmosphere and a logarithm law in a H2-H20 atmosphere in the steady-state stage. The oxide film grown in the air-H2O atmosphere had cracks where the elements Fe and Ni were enriched and the un-cracked area was covered with octahedral-shaped MnCr2O4 spinels and Cr1,3Fe0.7O3 oxide clusters, while the oxide film grown in the H2-H2O atmosphere was intact and completely covered with dense standing blade MnCr2O4 spinels. In the pyrolysis tests, the anti-coking performance and resistance to carburization of the oxide film grown in the H2-H2O atmosphere were far better than that in the air-H20 atmosphere. The mass of coke formed in the oxide film grown in the H2-H2O atmosphere was less than 10% of that in the air-H2O atmosphere. The Cr1.3Fe0.7O3 oxide clusters converted into Cr23C6 carbides and the cracks were filled with carbon in the oxide film grown in the air-H2O atmosphere after repeated coking and decoking tests, while the dense standing blade MnCr2O4 spinels remained unchanged in the oxide film grown in the H2-H2O atmosphere. The ethylene, propylene and butadiene yields in the pyrolysis tests were almost the same for the two oxide films.

Investigation on alternative disposal methods for froth treatment tailings—part 2, Recovery of asphaltenes

AbstractIn collaboration with Total E&P Canada (TEPCA), CanmetENERGY conducted an extensive research program to investigate possible alternatives for TSRU tailings disposal. We have reported on alternative methods for TSRU tailings disposal without recovery of asphaltenes in an earlier publication.[1] Because the asphaltenes are high‐molecular‐weight hydrocarbons and may have potential for use as fuel or paving material, in this work, we investigate possible approaches for recovery of the asphaltenes from TSRU tailings. Two methods were tested, solvent extraction and aggregation. In the first method aromatic solvent is mixed with TSRU tailings to dissolve the asphaltenes followed by centrifugation to remove mineral solids and water. The experimental results demonstrated that more than 90% of the asphaltenes in the tailings can be recovered from the tailings. The recovered asphaltenes contained only a small fraction of mineral solids and may be useable as coker feed. In the second method, TSRU tailings are agitated at elevated temperature (80°C) at which the asphaltene particles form large aggregates and separate from the tailings, giving an asphaltene‐rich phase and almost asphaltene‐free tailings. The recovered asphaltene aggregates still contain significant amounts of mineral solids and water, and would require further treatment. Several coking tests were conducted using the recovered asphaltenes and the asphaltene aggregates. The results demonstrated that about 40 wt% of the recovered asphaltenes can be converted to lighter oil fractions under the coking conditions used in this work.

The effect of perchloroethylene on coking properties

A two-stage study was undertaken to establish what effect, if any, perchloroethylene has on coal coking properties. Stage 1 was a kinetic study in which the Gieseler fluidity of samples of a high fluidity coal was measured over a 64-week period. Two of the samples were left untreated, with one stored in air and one immersed in water. The third sample was also stored in air, but was soaked in perchloroethylene for 2h and then air dried immediately prior to fluidity testing. In Stage 2, seven different coking coals were studied, covering three different Australian coal measures and a wide range of coking rank. For each coal, a 40kg clean coal composite was formed using laboratory water-based methods, a Reflux Classier for the 0.038–0.25mm and 0.25–2.0mm size fractions and a Mintek jig for the 2.0–16 and 16–50mm size fractions. This 40kg composite was then subdivided into four sub-samples. Samples A and B were coked immediately, whereas Samples C and D were stored in open trays at ambient conditions for a month before coking. Samples B and D were soaked in perchloroethylene for 2h and then air dried prior to coke testing, whereas Samples A and C were left untreated. Coal properties were measured prior to coking, and after coking the NSC Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) were measured.In Stage 1 it was found that storage under water was able to maintain the sample fluidity better than refrigerated storage. The combined Stage 1 and 2 results showed that perchloroethylene had a detrimental effect on the coking properties of many coals. Hence coking tests on clean coal composites formed using heavy organic liquids may often under predict a coal’s true coking properties. This could lead to many coal deposits being undervalued. Perchloroethylene had the largest detrimental effect on the fluidity, CRI and CSR of coals that started with relatively poor properties. Perchloroethylene had a negligible effect on coals with relatively good initial coking properties. There was no clear correlation with vitrinite reflectance. The three most seriously affected coals all had relatively high inertinite content. It is speculated that the higher porosity of inertinite might allow greater access and retention of perchloroethylene in the coal particles.The laboratory water-based methods were able to produce clean coal composites that matched the proximate, petrographic and coal swelling number properties of the coal preparation plant product. The dilatometer and fluidity results were lower than those of the coal preparation plant, but this can be explained by the up to three month delay between mining of the original sample and the coking of the composite. These delays were an unavoidable part of the research nature of this project and had nothing to do with the water based methods deployed. If these water-based methods of preparing clean-coal composites were to become standardized, then there is no reason why a well equipped coal testing facility could not receive a refrigerated bore core and produce a clean coal composite within the period of a week.

Assessing the metallurgical coke produced at OAO NLMK

Up-to-date methods of assessing coal and coke quality have been introduced at OAO NLMK. Industrial coking tests using high-quality Russian and imported coal have been conducted to boost coke quality. Algorithms are proposed for predicting the postreactive strength (CSR) and reactivity (CRI) of coke as a function of the batch characteristics.

LNGロケットエンジンにおけるサルファアタック及びコーキングに関する基礎研究

Liquified Natural Gas (LNG) is one of the most promising propellant for near future space transportation rocket engine because of its low cost and fewer handling concerns. However, for LNG propellant, erosion of engine material by sulfur (sulfur attack) and coking by LNG pyrolysis are significant problems in a regenerative cooling passage. In this study, the effects of sulfur attack and coking are experimentally evaluated for material candidates such as Inconel600, SUS316, Hastelloy-X, and some copper alloys. In the sulfur attack tests, EPMA and Raman analysis indicate that metallic sulfide can be observed only on the surface and XRD analysis indicates that sulfur attack are hardly recognized for all of material in the test conditions. In coking tests, it is clear that coking of methane with 5% propane can proceed more than those of pure methane. The thermal decomposition temperature is significantly decreased by catalytic effects of Ni in engine material. The results of coking tests will be included in the design criteria of combustion chamber, nozzle of the LNG rocket engines.

Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading

Abstract Bimetallic PdRh (with Pd/Rh mole ratio = 2/1) catalysts supported on a mesoporous aluminosilicate have been prepared and three methods of metal incorporation in the support have been compared: direct incorporation into the synthesis gel, impregnation and ion-exchange. Physico-chemical characterisations (nitrogen adsorption–desorption, hydrogen chemisorption, transmission electron microscopy, X-ray photoelectron and extended X-ray absorption fine structure spectroscopies), as well as simulated coking and regeneration tests are described. The dispersion, metal particle size and the formation of bimetallic particles within the material depend on the method of metal incorporation. Direct incorporation and ion-exchange methods lead to co-existence of PdRh intermetallic aggregates and segregated Pd; on the other hand, the impregnation method leads to the formation of very small and well dispersed PdRh alloy particles, with Pd preferentially located on the alloy particle surface.