Characteristics Of Coke Research Articles

Influence of Conversion Conditions on Heavy-Oil Coking During in Situ Combustion Process

Coking of heavy oil plays a key role in in situ combustion, which is affected by conversion conditions. In this study, a fixed-bed reactor and a pressurized reactor were used to thermally transform a heavy oil sample from China into coke under different atmospheric conditions, heating rates, and pressures. Elemental composition and surface functional groups were studied by an elemental analyzer and diffuse reflectance Fourier transform infrared spectrometer, whereas oxidative activity and coke yield were characterized by a thermal gravimetric analyzer. Results showed that yields, characteristics, and oxidative activities differed between the cokes produced in inert and oxidizing atmospheres. Compared with an inert atmosphere, an oxidizing atmosphere presented lower coke formation temperature and higher yield. In comparison with inert atmosphere, the coke produced in oxidizing atmosphere contained more oxygen, thus increasing the amount of surface functional group, but its oxidative activity was poorer. In oxidizing atmosphere, conversion conditions influenced yield and characteristics of coke but exerted minimal influence on oxidative activity. Oxygen content increased, whereas coke yield decreased with increasing O2 concentration. Oxygen content decreased, and yield increased initially and then decreased with increasing heating rate. Temperature of coke formation and oxidation decreased, while oxygen content and yield increased with increasing pressure. Through analysis of elements and functional groups of residues produced at different holding temperatures, our study confirmed that the following processes occurred during low-temperature oxidation: evaporation, oxygen-adding reaction, dehydrogenation and dealkylation, polymerization, decarbonylation, and mild oxidation of coke. Conversion conditions, including heating rate, oxygen concentration, and pressure, affected conversion rate of these processes, thus influencing coke characteristics.

Investigation of the coking behavior of serial petroleum residues derived from deep-vacuum distillation of Venezuela extra-heavy oil in laboratory-scale coking

The coking behavior of serial petroleum residues derived from deep-vacuum distillation of Venezuela extra-heavy oil has been systematically investigated in laboratory-scale coking appliances from the perspectives of distribution and properties of coking products. The usage of residue with deeper distilling cut would favor the decreasing of low-value products, i.e., coke and coking gas. The hydrogen circumstance of coking feedstock indicated by 1H NMR analysis, implies residue with ultra-deep distilling cut as a valid hydrogen evolution potential. By comparison with the de-metallization rate in the hydrodemetallization process (Ni, 61.2%; V, 80.8%) (Zhang et al., 2006), the performance in the study seems more promising. Evidently, the stripping of VGO would notably change the morphological characteristics of resultant coke. However, no secondary assembled or clustered shot coke was observed in the coker, which made the decoking quite easy. A valid linear agreement between the area of green region quantitatively assessing the process flexibility and the metal content has been established. The extrapolation (dot line) of the trend suggests that shot coke formation cannot be avoided in any circumstance of the study if the metal content of coking feedstock is over 1516 μg g−1.

Evaluation of wall slip effects on the flow characteristics of petroleum coke–water slurry flow along pipelines

AbstractFlow characteristics of petroleum coke–water slurry (PCWS) were investigated in a slurry transportation facility. True rheological properties, drag reduction, and flow resistances of PCWS under the influence of wall slip were studied using the Tikhonov regularization method. Results show that the shear viscosity is insensitive to changes in the shear rate when the solid loading of PCWS is 59.8 wt%. However, the PCWS of 61.1 wt% exhibits typical dilatant fluid properties. As the shear rate increases, the PCWS of 63.4 wt% initially exhibits shear thinning, and then, the viscosity increases sharply when the shear rate exceeds 250 s−1. In addition, the slurry also displays shear thinning at the shear rates exceeding 600 s−1. Modified friction factor‐generalized Reynolds number correlation is established to describe the resistance properties of a laminar flow of PCWS. When increasing the velocity, the drag reduction produced by the wall slip behavior reduces for the 59.8 wt% PCWS but increases for the 61.1 wt% PCWS. The drag reduction decreases at the outset followed by an increase for the 63.4 wt% PCWS. A decrease in the inner diameter of pipeline could enhance the effect of drag reduction of PCWS flowing in a pipeline. © 2017 Curtin University and John Wiley & Sons, Ltd.

Binders and the Bonding Mechanism of Fly Ash and Coke Pelletization

ABSTRACTFly ash is an industrial by-product generated during the combustion of coal in power plants and it could represent a very important source of minerals particularly alumina. Extracting alumina by pelletization and carbo-chlorination of fly ash is an effective utilization process. However, the strength of fly ash and coke pellets is very low, therefore the application of binders to the pellets should be investigated. In this study, physical and chemical characteristics of fly ash and coke were investigated followed by experiments with different binders to make pellets with a focus on pellet strength. The results of studies indicated that of all the binders evaluated, the organic binders generally produced pellets with greater strength than the inorganic binders, with carboxymethyl cellulose (CMC) being the most effective. Based on the results, it was concluded that a blend of CMC with pre-gelatinized starch was the best compromise for strength of the pellets and the cost point of view. The bonding mechanisms of the best binder have been discussed.

Effect of Glycerol on Coke Characteristics in the Aromatization of Aqueous Glycerol Solution

The characteristics of coke formed in the aromatization of aqueous glycerol solution over H-ZSM-5 has been investigated by various characterization techniques such as TGA for coke amount, BET and TEM–EDS for coke location, NH3-TPD and chemisorbed FT-IR for acid sites of coked samples, and TPO, XPS and UV-Raman for coke species. Coke formed in methanol aromatization was characterized for comparison. All results indicate that glycerol contributes to the formation of heavy and oxygenated coke, unlike methanol, that was grown from internal Bronsted acid sites of H-ZSM-5 and rapidly spread all over the particles. This is due to the three OH groups of glycerol that can be condensed via intramolecular and intermolecular dehydration reactions in various manners, which explains the fact that glycerol is transformed into multi-ring aromatics like naphthalenes via oxygen-containing intermediates including alcohol, aldehyde, ester and ketone molecules. This is the effect of glycerol on coke formed in glycerol aromatization.

Comparative study on calcination of weight loss for coking and calcined coke properties used for aluminum anode –grade

The aim of the present paper consists in the evaluation of the physical-chemical characteristics of some petroleum coke, before and after thermal treatment, which was used to observe the alterations which took place over the coke’s quality. The impact of heat treatment (temperature, heat-soak time and heating rate) on petroleum coke properties were examined. Investigated coke produced from feedstock with different compositions. the sulphur content, volatile matter, density value and ash content before and after heat treatment to 1100 °C were analysed. These properties along with low metals and ash contents make calcined petroleum coke the best material currently available for making carbon anodes.

石油焦在宝钢的炼焦配煤应用研究

通过全面分析和比较石油焦的性质，认识了石油焦的特点。利用石油焦的比较优势，通过部分工业配煤试验,掌握了其在配煤中的应用特性，为炼焦配煤技术进步，及开发炼焦原料新资源做出了有益探索。 Through series of experiments, the characteristics of petroleum coke are analyzed. And the char-acteristic of petroleum coke are obtained. By taking the advantage of the characteristic of petro-leum coke, the applied characteristic of petroleum coke in the coal blending is well obtained through industrial experiments.

Indoor/Outdoor Air Quality Assessment at School near the Steel Plant in Taranto (Italy)

This study aims to investigate the air quality in primary school placed in district of Taranto (south of Italy), an area of high environmental risk because of closeness between large industrial complex and urban settlement. The chemical characterization of PM2.5 was performed to identify origin of pollutants detected inside school and the comparison between indoor and outdoor levels of PAHs and metals allowed evaluating intrusion of outdoor pollutants or the existence of specific indoor sources. The results showed that the indoor and outdoor levels of PM2.5, BaP, Cd, Ni, As, and Pb never exceeded the target values issued by World Health Organization (WHO). Nevertheless, high metals and PAHs concentrations were detected especially when school were downwind to the steel plant. TheI/Oratio showed the impact of outdoor pollutants, especially of industrial markers as Fe, Mn, Zn, and Pb, on indoor air quality. This result was confirmed by values of diagnostic ratio as B(a)P/B(g)P, IP/(IP + BgP), BaP/Chry, and BaP/(BaP + Chry), which showed range characteristics of coke and coal combustion. However, Ni and As showedI/Oratio of 2.5 and 1.4, respectively, suggesting the presence of indoor sources.

Geochemical characteristics of oil sands fluid petroleum coke

The geochemical characteristics of fluid petroleum coke from the Athabasca Oil Sands Region (AOSR) of northern Alberta, Canada were investigated. Continuous core samples were collected to 8 m below surface at several locations (n = 12) from three coke deposits at an active oil sands mine. Bulk elemental analyses revealed the coke composition was dominated by C (84.2 ± 2.3 wt%) and S (6.99 ± 0.26 wt%). Silicon (9210 ± 3000 mg kg−1), Al (5980 ± 1200 mg kg−1), Fe (4760 ± 1200 mg kg−1), and Ti (1380 ± 430 mg kg−1) were present in lesser amounts. Vanadium (1280 ± 120 mg kg−1) and Ni (230 ± 80 mg kg−1) exhibited the highest concentrations among potentially-hazardous minor and trace elements. Sequential extractions revealed potential for release of these metals under field-relevant conditions. Synchrotron powder X-ray diffraction revealed the presence of Si and Ti oxides, organically-complexed V and hydrated Ni sulfate, and provided information about the asphaltenic carbon matrix. X-ray absorption near edge structure (XANES) spectroscopy at the V and Ni K-edges revealed that these metals were largely hosted in porphyrins and similar organic complexes throughout coke grains. Minor differences among measured V and Ni K-edge spectra were largely attributed to slight variations in local coordination of V(IV) and Ni(II) within these organic compounds. However, linear combination fits were improved by including reference spectra for inorganic phases with octahedrally-coordinated V(III) and Ni(II). Sulfur and Fe K-edge XANES confirmed that thiophenic coordination and pyritic-ilmenitic coordination are predominant, respectively. These results provide new information on the geochemical and mineralogical composition of oil sands fluid petroleum coke and improve understanding of potential controls on associated water chemistry.

Study on rapid pyrolysis and in-situ char gasification characteristics of coal and petroleum coke

Rapid pyrolysis characteristics of three different rank coals and two petroleum cokes were investigated using a drop tube furnace. Moreover, gasification characteristics of char samples were studied in an in-situ heating stage. The results showed that H2 and CO were the main gaseous pyrolysis products of coal samples. The relative content of H2 and CO increased with increasing pyrolysis temperature. The volume fraction of H2 in syngas increased with increasing coal rank, whereas that of CO showed the contrary trend. Anthracite and petroleum cokes (Petcoke 1 and Petcoke 2) exhibited a great similarity in gas release characteristics. There was a maximum value for the specific surface area and graphitization degree of char samples with increasing pyrolysis temperature. The results of in-situ heating stage experiments indicated that the most of char particles reacted with CO2 in the shrinking particle mode at the initial stage. Char samples of petcokes and anthracite were similar in slow consumption of particle skeleton during gasification. Interestingly, petcokes demonstrated particle migration, residual agglomeration, and rapid consumption at the later reaction stage. The variation trend of the area shrinkage ratio of char samples was well verified by the TGA results.

Assessing coke strength

Available methods of assessing the characteristics of coke—in particular, its strength—are reviewed. Their relative advantages and disadvantages are considered. A method of direct determination of coke strength is proposed, including a method of assessing the crack resistance in which the porosity and also the shape and size of the sample are taken into account.

Quality assessment of metallurgical coke: Fast determination of reactivity and postreactive strength

The quality of metallurgical coke may be assessed on the basis of technical analysis, the granulometric composition, mechanical strength, reactivity, structural strength, density and porosity, postreactive strength, and other characteristics. Analysis shows that the strength characteristics of coke in the cold, heated, and subsequently cooled states are closely correlated. Methodological and technological deficiencies of the determination of CRI and CSR are outlined. An express method of determining coke quality is developed. The postreactive strength determined by the method proposed at the central laboratory for coke production at OAO EVRAZ NTMK is shown to be closely correlated with the reactivity (CRI) and postreactive strength (CSR) determined in accordance with the ASTM standard. Accordingly, by the proposed method, the reactivity of the coke and its strength after reaction with carbon dioxide may be predicted with high probability.

Comparison of steam-gasification characteristics of coal char and petroleum coke char in drop tube furnace

The steam-gasification reaction characteristics of coal and petroleum coke (PC) were studied in the drop tube furnace (DTF). The effects of various factors such as types of carbonaceous material, gasification temperature (1100–1400°C) and mass ratio of steam to char (0.4:1, 0.6:1 and 1:1 separately) on gasification gas or solid products were investigated. The results showed that for all carbonaceous materials studied, H2 content exhibited the largest part of gasification gaseous products and CH4 had the smallest part. For the two petroleum cokes, CO2 content was higher than CO, which was similar to Zun-yi char. When the steam/char ratio was constant, the carbon conversion of both Shen-fu and PC chars increased with increasing temperature. When the gasification temperature was constant, the carbon conversions of all char samples increased with increasing steam/char ratio. For all the steam/char ratios, compared to water gas shift reaction, char-H2O and char-CO2 reaction were further from the thermodynamic equilibrium due to a much lower char gasification rate than that of water gas shift reaction rate. Therefore, kinetic effects may play a more important role in a char gasification step than thermodynamic effects when the gasification reaction of char was held in DTF. The calculating method for the equilibrium shift in this study will be a worth reference for analysis of the gaseous components in industrial gasifier. The reactivity of residual cokes decreased and the crystal layer (L002/d002) numbers of residual cokes increased with increasing gasification temperature. Therefore, L002/d002, the carbon crystallite structure parameter, can be used to evaluate the reactivity of residual cokes.

Selecting the properties of metallurgical coke for cupola furnaces

Analysis of the chemical composition of solid fuel permits the identification of the optimal proportions of its components for effective heat generation. Kinetic analysis of the oxidation of the carbon in the coke, by means of the complete curve obtained in differential scanning calorimetry with continuous heating, reveals six basic periods: drying and heating; oxidation of the carbon in the coke; endothermal gasification; surface oxidation of the gaseous products; flame combustion of the gaseous products, and oxidation of interior layers of the fuel. By assessing the behavior of the coke in shaft furnaces, the requirements on its granulometric composition, density, and mechanical strength in transportation and heat treatment may be determined. Recommendations are made regarding the characteristics of coke for use in the basic forms of cupola furnaces.

Characterization, gasification, activation, and potential uses for the millions of tonnes of petroleum coke produced in Canada each year

Petroleum coke is a by‐product of oil sands upgrading and consists of mainly carbon with hydrogen, nitrogen, sulfur, oxygen, and several trace elements. Canada has abundant petroleum coke resources—as much as 77 million tonnes of this material was stockpiled in Alberta by the end of 2012, and this amount continues to increase at the rate of approximately four million tonnes per year. Thus, this material represents a huge, inexpensive resource that can potentially be used for a variety of applications. This article describes the characteristics of petroleum coke, some of the work our group has done with gasification and activation to create both adsorbents and catalysts, and the challenges encountered with both characterization and testing of this material.

Steam Cogasification of Petroleum Coke and Different Rank Coals for Enhanced Coke Reactivity and Hydrogen-Rich Gas Production

Steam cogasification characteristics of petroleum coke with three coals of different ranks were investigated on a laboratory fixed-bed reactor to examine the effects of coal ratios and coal ranks on the gasification reactivity, gas yields, and compositions. Results show that the rise of the coal ratio leads to an increase in H2 yield and content but a decrease in CO yield and content in the producer gas, independently of coal rank. The cogasification reactivity of petroleum coke (PC) with XLT coal and PC with SF coal at the optimum coal contents of 40% and 80% are about 4.5- and 3.5-fold higher than that of PC gasification alone (XLT = Xiaolongtan lignite from Yunnan province, SF = Shenfu bituminous coal from Shaanxi province); meanwhile, H2 contents in the producer gas increased by 10.55% and 12.24%. The ordering for the cogasification reactivity of PC with different rank coals is as follows: PC/XLT > PC/SF > PC/GP, which is in accord with the chemical forms of catalytic elements present in the three coa...

Combustion Characteristics of Coal and Coke Under High Oxygen Concentration Oxy-Fuel CFBC Conditions

Oxy-fuel circulating fluidized bed combustion (CFBC) is one of the emerging technologies for reducing green house gas emissions from fossil fuel power generation. To improve the overall efficiency of an oxy-fuel CFBC plant and reduce the cost of CO2 capture, high oxygen concentration combustion is desired, as it means a lower flue gas recycle ratio and a smaller combustion chamber. To support the study of high oxygen concentration oxy-fuel research, combustion characteristics of different fuels were determined in a thermogravimetric analyzer (TGA). The fuels tested include lignite, bituminous coal, anthracite, and petroleum coke. Results showed that under the conditions tested, oxygen concentrations had only weak effect on the ignition of all the fuels. However, higher oxygen levels, as expected, reduced the burnout time. It was noticed that at typical CFBC combustion temperatures (˜900 °C), direct reaction between CO2 and carbon is negligible, even though the CO2 concentrations in the gas mixtures were high.

Catalytic Conversion of a Mesitylene and n-Decane Mixture in the Presence of Hydrogen Over ZSM-5 Based Catalysts

Conversion reactions of mesitylene and n-decane mixture over different catalysts prepared on the base of ZSM-5 zeolite were investigated. The influence of reaction temperature on the activity and selectivity of HZSM-5, DZSM-5, and Ni-Mo/ZSM-5 catalysts obtained from NH4ZSM-5 zeolite was researched for this purpose. According to received results it can be concluded that mesitylene mostly exposed to isomerization and disproportionation, n-decane exposed to hydrocracking reactions up to C1–C4 hydrocarbon gases. The catalysts were characterized by textural properties and crystallinity. Thermal oxidation characteristics of coke deposited on the catalysts surface were also researched.

Comparison of pressure drops through different bends in dense-phase pneumatic conveying system at high pressure

In order to investigate the effect material property, bend geometry and location on pressure drop through the bend, experiments of dense-phase pneumatic conveying are carried out at conveying facility with the pressure up to 4.0MPa. Petroleum coke and anthracite powders with different particle sizes are applied to examine flow characteristics. The empirical correlations of pressure drop through the bend are obtained using Barth’s additional pressure theory and multi-variable linear regression. Results show that pressure drop through vertical downward bend is the least, followed by pressure drop through horizontal bend, pressure drop through vertical upward bend is the largest. Powders with larger size need consume more energy than that with smaller size at the same solid loading ratio and conveying velocity as gas–solid mixture flows across the same radius bend. Flow characteristics of petroleum coke and anthracite are analyzed and compared. Pressure drop through the bend with the long radius is greater than that with the short radius. While to unit length, pressure drop of long radius bend is less than that of short radius bend. The empirical correlations of pressure drop through the bend are derived and predicted results agree well with the experimental results. The flow characteristics of the bend offer the theoretical support for design, control and operation of dense-phase pneumatic conveying at high pressure.

Study on CO2 gasification reactivity and physical characteristics of biomass, petroleum coke and coal chars

Gasification reactivities of six different carbonaceous material chars with CO2 were determined by a Thermogravimetric Analyzer (TGA). Gasification reactivities of biomass chars are higher than those of coke and coal chars. In addition, physical structures and chemical components of these chars were systematically tested. It is found that the crystalline structure is an important factor to evaluate gasification reactivities of different chars and the crystalline structures of biomass chars are less order than those of coke and coal chars. Moreover, initial gasification rates of these chars were measured at high temperatures and with relatively large particle sizes. The method of calculating the effectiveness factor η was used to quantify the effect of pore diffusion on gasification. The results show that differences in pore diffusion effects among gasification with various chars are prominent and can be attributed to different intrinsic gasification reactivities and physical characteristics of different chars.