Coke Materials Research Articles

Improved electrochemical properties of lithium-ion batteries prepared using oxygen plasma-treated needle coke-based anode materials

High-rate capacities and specific capacities are important indicators for evaluating lithium-ion battery (LIB) anodes. To improve the electrochemical properties of needle coke-based anode materials, oxygen plasma treatment was used. Various analyses were performed to assess the impact of the oxygen plasma treatments on the chemical, structural, and morphological properties of the needle coke samples. The oxygen plasma treatment effectively introduced oxygen functional groups (hydroxyl, ether, carbonyl, and carboxyl groups) without significant structural changes to the needle coke samples, and the O/C ratio increased to 0.23 after the plasma treatment. The synergistic effect of the increased oxygen content and the defects formed on the surface by plasma treatment improved the electrochemical properties of the needle coke-based anodes. The discharge capacity of the oxygen plasma-treated needle coke-based LIBs increased to a maximum of 20.48 %, and the retention rate was 74.51 % at 5 C with respect to 0.1 C. The oxygen plasma-treated needle coke material prepared via a simple method could have an important role in improving the rate capacities and specific capacities of LIBs.

Insights into the thermal and electric field distribution and the structural optimization in the graphitization furnace

The Acheson graphitization furnace (AGF), as a most energy-consuming equipment for graphite production, results in substantial thermoelectric losses during heating process. To improve the thermal efficiency, a method is proposed to optimize the structure of furnace core based on the thermoelectric field distribution. In this study, a numerical simulation using FLUENT software was adopted to explore the characteristics and coupling rules in relation to thermoelectric field distribution. Further optimize furnace core structure to achieve more suitable performance indicators, which include electrical heating efficiency and thermal efficiency. The results suggested that the changes of electric (power density) and thermal (temperature) fields with the layout of coke materials exhibited a consistence: the lower power density and temperature were observed at the position of graphitized coke, while the higher values were for calcined coke. The heat producer during the graphitization process was twofold: the electric heat and the transferred heat, and their proportion was confirmed as a range of 7:3–9:1. Under a fixed square side section, which is an optimal scenario, both thermal efficiency and electric heating efficiency with the furnace core length presented a parabolic variation. These findings may provide some guidelines and insights for a better design and operation of AGFs.

Characterization of Potential Dependent Fouling of Cu Electrodes during Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acid

Furfural (FF) is a platform molecule derived from biomass, that can be electrochemically reduced to produce furfuryl alcohol (FA), a furanic polymer intermediate, and 2-methylfuran (MF), a fuel candidate. On Cu in acidic media, it has been shown that FA and MF are produced via parallel reactions as opposed to a series reaction. Our previous work investigated the reactions for FA and MF production electrochemically with FF concentrations between 10 and 120 mM, showing positive order with respect to FF at low concentrations and zero order rates with respect to FF at higher concentrations. This finding suggesting non-competitive Langmuir-Hinshelwood mechanisms at concentrations of FF between 10 and 120 mM in pH 0 and 1 acidic solutions. At 200 mM concentrations of FF, we have identified fouling on the Cu surface. At moderate potentials, the fouling takes the form of a polymer material, whereas at more negative reduction potentials the fouling takes the form of graphitic coking. Understanding how fouling occurs on Cu electrodes is important in achieving progress towards mitigating or reducing the impact of fouling through reactor setup and catalysts design.In this work, conditions that promote fouling were selected so that the fouling of Cu electrodes could be studied. The conditions were chronoamperometry at -560 or -700 mV RHE, 200 mM FF, 0.5M H2SO4, 20:80 vol% acetonitrile:water, for three hours durations. The Cu electrodes were reused for 3 experiments to further promote fouling and study the impact on the electrochemical performance. We showed that after reuse at -560 mV RHE, a polymeric material formed on the Cu electrode, while when reused at -700 mV RHE the electrode was instead covered in a coke like material. FTIR spectroscopy showed that the polymer formed at -560 mV resembled poly(furfuryl alcohol) while the coking substance showed broad absorbance, expected of coke like materials. To better understand the coke material formed at -700 mV, Raman spectroscopy was used. The material resembled graphitic disorganized carbon, with a D/G band intensity ratio of 0.652.

Assessment of the Suitability of Coke Material for Proppants in the Hydraulic Fracturing of Coals.

To enhance the extraction of methane gas from coal beds, hydraulic fracturing technology is used. However, stimulation operations in soft rocks, such as coal beds, are associated with technical problems related mainly to the embedment phenomenon. Therefore, the concept of a novel coke-based proppant was introduced. The purpose of the study was to identify the source coke material for further processing to obtain a proppant. Twenty coke materials differing in type, grain size, and production method from five coking plants were tested. The values of the following parameters were determined for the initial coke: micum index 40; micum index 10; coke reactivity index; coke strength after reaction; and ash content. The coke was modified by crushing and mechanical classification, and the 3-1 mm class was obtained. This was enriched in heavy liquid with a density of 1.35 g/cm3. The crush resistance index and Roga index, which were selected as key strength parameters, and the ash content were determined for the lighter fraction. The most promising modified coke materials with the best strength properties were obtained from the coarse-grained (fraction 25-80 mm and greater) blast furnace and foundry coke. They had crush resistance index and Roga index values of at least 44% and at least 96%, respectively, and contained less than 9% ash. After assessing the suitability of coke material for proppants in the hydraulic fracturing of coal, further research will be needed to develop a technology to produce proppants with parameters compliant with the PN-EN ISO 13503-2:2010 standard.

Increasing biodegradability of a real amine-contaminated spent caustic problematic stream through WAO and CWAO oxidation using a high specific surface catalyst from petcoke

Different operating conditions of wet air oxidation and catalytic wet air oxidation have been studied for the treatment of highly concentrated methyldiethanolamine wastewater streams from amine units of acid gas recovery in petrol refineries. These units occasionally generate streams of high methyldiethanolamine content that require special actions to avoid undesirable impacts on the downstream biological process of the petrochemical wastewater treatment plant due to its inhibition effect. The wet air oxidation treatment achieved remarkable removals of methyldiethanolamine, sulfides, chemical oxygen demand and total organic carbon (99%, 95%, 65% and 38%, respectively). Likewise, activated petroleum coke materials from the own refinery plant were tested as catalysts in the process. These materials were prepared under different conditions (chemical activating agent and thermal carbonization process). The catalytic wet air oxidation treatment using an activated petroleum coke was able to remove the methyldiethanolamine at milder operation conditions keeping a similar performance in terms of wastewater treatment removals as compared to the non-catalytic experiments. This technology significantly increased the biodegradability of the treated effluents ranging from 25 to 70 % due to the formation of more biodegradable substrates (acetic acid and ammonium) for further biological treatment.

Types and Composition of Biomass in Biocoke Synthesis with the Coal Blending Method

The steelmaking industry requires coke as a reducing agent, as an energy source, and for its ability to hold slag in a blast furnace. Coking coal as raw coke material is very limited. Studying the use of biomass as a mixture of coking coal in the synthesis of biocoke is necessary to reduce greenhouse gas coal emissions. This research focuses on biomass and heating temperature through the coal blending method to produce biocoke with optimal mechanical properties for the blast-furnace standard. The heating temperature of biomass to biochar was evaluated at 400, 500, and 600 °C. The blending of coking coal with biochar was in the compositions of 95:5, 85:15, and 75:25 wt.%. A compacting force of 20 MPa was employed to produce biocoke that was 50 mm in diameter and 27 mm thick using a hot cylinder dye. The green sample was heated at 1100 °C for 4 h, followed by quenching with a water medium, resulting in dense samples. Increasing heating temperature is generally directly proportional to an increase in fixed carbon and calorific value. Biocoke that meets several blast-furnace criteria is a coal mixture with coconut-shell charcoal of 85:15 wt.%. Carbonization at 500 °C, yielding fixed carbon, calorific value, and compressive strength, was achieved at 89.02 ± 0.11%; 29.681 ± 0.46 MJ/kg, and 6.53 ± 0.4 MPa, respectively. This product meets several criteria for blast-furnace applications, with CRI 29.8 and CSR 55.1.

A MULTILEVEL RESOURCE-SAVING BLAST FURNACE PROCESS CONTROL

A multilevel resource-saving blast furnace process control is considered. The resource-saving control is provided for operating, adaptation, technical and economic control in the automated systems of blast-furnace processes. It is proposed to form optimal operation modes of blast furnace heating, metal charge structures, natural gas and oxygen consumption. Decisions are made using Kohonen neural networks taking into account current and planned parameters of coke quality, iron ore, raw materials and blast. At the level of operating control, the work suggests a model predictive control to improve the resource conservation indicators. The method is based on decomposition of the general problem of the process dynamics identification on particular problems: dynamic synchronization and identification of process transfer functions. At the level of adaptive control, optimal operating modes of blast furnaces are expedient to be developed with respect to blast furnace heating, structure of metal charge, natural gas and oxygen rate considering the current and planned parameters of coke, blasting. The blast furnace operating modes are suggested to be determined based on Kohonen neural networks. In evaluating the efficiency of introducing the model predictive control, the existing actual statistics of scatter of BF mode parameters should be based upon. The fact is that the introduction of model predictive control assumes no radical change of the BF melt technology. Like in all the control systems, the BF process is considered as the set control object with all its characteristics. Changing process settings, raw material content does not introduce any cardinal variation in the scatter of process characteristics. However, in this case a transient process occurs which is necessary for the control system to identify the changing conditions. The transient process is inherent to all the control systems and the blast furnace process is not an exclusion. As a result of transient process, the control system is set to the optimal mode.

Suspension assisted analysis of sulfur in petroleum coke by total-reflection X-ray fluorescence

The influence of the particle size distribution of a petroleum coke sample compared to its sulfur content was investigated. For this matrix, an optimization procedure of the Suspension Assisted Analysis (SAA) by Total-reflection X-Ray Fluorescence (TXRF) quantitative method was developed. SAA-TXRF sulfur recoveries were evaluated for three particle size distributions of the same coke sample. The sulfur recovery increased when the particle size distribution was smaller. The observed behaviour was correlated and validated with CHNS elemental analysis and microwave-assisted digestion TXRF measurements. The results indicate that the sulfur signal is strongly influenced by the particle size distribution and the deposition morphology of the petroleum coke material. This effect could be explained by the presence of a strong absorption effect for the sulfur signal in combination with the distortion of the X-ray Standing Waves (XSW) field observed between the analyte, S, and the elements Ti and Co, which were used as an internal standard. The variation in sulfur observed was up to 45.5% lower than the higher recovery obtained by CHNS. This investigation suggests that for an adequate application of the SAA-TXRF method in petroleum coke or similar matrices, careful optimization of the final particle dispersion of the ground coke is crucial and necessary. In this case, the use of a high- power ultrasound probe was the key.

Removal of Sulfur Compounds from Industrial Emission Using Activated Carbon Derived from Petroleum Coke

Activated carbon (AC) materials are porous structures generated by activation of either pyrolyzed plant or coke materials through physical or chemical means. While being widely used in industry for...

Use of an epiphytic lichen and a novel geostatistical approach to evaluate spatial and temporal changes in atmospheric deposition in the Athabasca Oil Sands Region, Alberta, Canada

Temporal and spatial atmospheric deposition trends of elements to the boreal forest surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a long-term lichen bioindicator study. The study focused on eight elements (sulfur, nitrogen, aluminum, calcium, iron, nickel, strontium, vanadium) that were previously identified as tracers for the major oil sand production sources. Samples of the in situ epiphytic lichen Hypogymnia physodes were collected in 2002, 2004, 2008, 2011, 2014, and 2017 within a ~150 km radius from the center of surface oil sand production operations in the AOSR. Site-specific time series analysis conducted at eight jack pine upland sites that were repeatedly sampled generally showed significant trends of increasing lichen concentrations for fugitive dust linked elements, particularly at near-field (<25 km from a major oil sands production operation) sample locations. Multiple regional scale geostatistical models were developed and evaluated to characterize broad-scale changes in atmospheric deposition based on changes in H. physodes elemental concentrations between 2008 and 2014. Empirical Bayesian kriging and cokriging lichen element concentrations with oil sands mining, bitumen upgrading, coke materials handling, and limestone quarry/crushing influence variables produced spatial interpolation estimates with the lowest validation errors. Gridded zonal mean lichen element concentrations were calculated for the two comprehensive sampling years (2008, 2014) and evaluated for spatial and temporal change. Lichen sulfur concentrations significantly increased in every grid cell within the domain with the largest increases (44-88%) in the central valley in close proximity to the major surface oil sand production operations, while a minor nitrogen concentration decrease (-20%) in a single grid cell was observed. The areal extent of fugitive dust element deposition generally increased with significantly higher deposition to lichens restricted to the outer grids of the enhanced deposition field, reflecting new and expanding surface mining activity.

The use of thermogravimetry as a means of predicting the performance of coke in delayed coking of a residue of Venezuelan origin

A study, which shows the similarities in the results obtained through this technique and those corresponding to a process of delayed coking at laboratory scale, is presented. Fifteen mixtures with a controlled composition of SARA (saturate, aromatic, resin and asphaltene) fractions which make up the crude were processed both in a delayed coking laboratory unit (DCLU) and in a thermogravimetric analyzer (TG). The comparison of the behavior of the yield of the coke and volatile material obtained through both mediums, DCLU and TG, showed similarities in the mixtures with high aromatic and asphaltene content, but differences in the mixtures with high resin content which would be associated with the formulation of the same, thus indicating the synergy of the fractions within the chemical reaction process taking place, which lead to different reaction pathways depending on the composition of the mixture fed. The similarities in the results obtained through TG and those from DCLU, while not reproducing the exact magnitude of the results, may lead to this technique being a valid reference for the study of changes in the diets used in the process with low resource consumption at both laboratory and industrial scale.

Low-temperature oxidation and thermal kinetics analysis of light and medium crude oils

ABSTRACTIn this research, low-temperature oxidation (LTO) and thermal kinetics analysis of light and medium crude oils were analyzed by static isothermal experiments and thermogravimetry (TG). The results elucidated that, during LTO process, medium oil possessed stronger oxygen consumption capability than light oil and oxygen addition was the dominating reaction path for both light and medium oils; more heavy components contained in medium oil were oxidized to form higher molecular-weight material with lower H/C. In TG experiments, three main reaction zones were identified known as LTO, fuel deposition (FD) and high-temperature oxidation (HTO). Compared with light oil, LTO range and corresponding mass loss were lowered for medium oil with more oxygenated compounds left behind to be converted into coke materials. The activation energy for medium oil were higher than that for light oil in LTO stage while less in HTO stage owing to the difference of oil components.

The effective silylation of external surface on H-ZSM5 with cyclic siloxane for the catalytic cracking of naphtha

Acid sites existing on the external surface of zeolites are the main cause of the formation of coke materials, resulting in decreasing the catalytic activity. For the durability of the reaction, silylation of external acid sites was adopted. Among various silylation reagents, cyclic siloxanes were effective silylation compounds for the deactivation of the acid sites on external surface on zeolite without prohibiting the objective reaction, cracking of naphtha. The effect of silylation was confirmed not only by the reaction but also by infra-red analysis.

The New Method of XRD Measurement of the Degree of Disorder for Anode Coke Material

Quantitative analysis by X-ray powder diffraction of two cokes (pitch coke and petroleum coke) shows that their crystal structure changed with increasing temperature. The crystal data processing of the crystallization degree of disorder is used with further improvement of the proposed microcrystalline-stacking fault calculation method. With this improvement it is now possible to obtain the degree of stacking disorder of two cokes applied as anode materials at different graphitization temperatures. Raman spectroscopy verified the accuracy of this method, which is more reliable than the crystal structure refinement using the d002 method. This paper provides the theoretical analysis and interpretation of the relationship between the microstructure model of the material and quantitative data, discharge capacity, and the first charge-discharge efficiency.

Substrate effect of coke particles on the structure and reactivity of coke/pitch mixtures in carbon anodes

Carbon anodes, used in the Hall-Héroult electrolysis process, are subject to an overconsumption caused by CO2 attack. Several attempts have been made to understand the mechanism of CO2 gasification based on the study of the reactivity of anode cores or anode constituents (coke, pitch and binder matrix). In this study, the specific surface area and the pore volume of carbon anode and of three coke/pitch mixtures were measured to understand properly the CO2 reactivity. Anode sample and three recipes of coke/pitch mixtures (100/0; 95/5 and 85/15, w/w) with a particle size of −1.4+1.0mm were prepared. Argon adsorption and mercury infiltration were used to characterize the pore size distribution of the four samples. The specific surface area of anode and partially covered coke materials (95/5) were superior to that of the uncovered and totally covered particles (12m2/g vs. 0.5m2/g). Although the pore volume of the uncovered coke was high (0.45cm3/g), the pore volume of totally covered coke was low (0.35cm3/g). The pore volume of anode and partially covered coke were similar (0.4cm3/g). A TG instrument was used to determine the apparent reaction rates of the four samples at 960°C under CO2 atmosphere. It was remarked that the apparent reaction rate of coke/pitch mixtures was reduced with increasing the pitch content. The anode had an apparent reaction rate above that of totally covered particles but below the partially covered particles. Based on the apparent reaction rate and the pore analysis, the structure of an anode can be considered as a mixture of coke particles with different levels of pitch penetration. The pitch distribution in an anode paste could prevent the preferential gasification of some particles, thus possibly reducing dusting phenomenon.

Fractographic approach to metallurgical coke failure analysis. Part 2: Cokes from binary coal blends

Metallurgical coke used in blast furnaces is the result of blending coals to achieve the optimum coke strength properties. Prediction of coke strength from coal properties relies primarily on statistical methods. Improvement of these models is desirable. We believe a better understanding of the fundamental factors controlling coke strength is required to achieve this.In this second of a series of three papers, we apply our recently developed fractographic approach to examine and quantify the breakage behaviour and microstructural weaknesses in pilot oven metallurgical cokes from two series of single coals and binary blends of the coals. We have successfully applied fractography to perform an effective failure analysis of the complex, heterogeneous coke material. Summaries of the factors contributing to the failure of each coke studied have been presented as radar graphs. These graphs demonstrate that the failure profile of the cokes from blends is not simply a weighted average of the fracture behaviour of the cokes from the constituent single coals. Instead, non-additive effects are observed, and this may have implications for the mathematical models widely used to predict coke behaviour and strength in the blast furnace.Trends between the various fractographic parameters have been identified, and preliminary relation of these to both the maximum compressive strength of each coke and basic properties of the original coals, has been completed. Enhanced understanding of how the fracture behaviour of each coke relates to the properties of the coal blend used will help facilitate better prediction of coke strength from coal properties and ultimately optimisation of the coal blending process.

Desarrollo de un prototipo recuperador de calor residual de lecho empacado de caliza y coque

— En el presente trabajo se diseñó un prototipo de recuperador de calor residual de lecho empacado de caliza y coque, el cual simula la captura de los gases de combustión proveniente de la chimenea de un horno vertical para calcinación de la caliza y obtener cal. El aprovechamiento de estos gases tiene por objeto precalentar un nuevo material de caliza y coque. Dichos gases son expulsados usualmente al medio ambiente con temperaturas superiores a 545 °C. El recuperador consiste en dos tubos de acero inoxidable, uno móvil y uno fijo, el tubo móvil es el recuperador como tal, el tubo fijo cumple la función de soporte, El recuperador (tubo móvil) tiene un diámetro interno de 0.096 m y una altura de 0.25 m, el gas utilizado es aire representado por las RPM del ventilador. El lecho empacado es caliza y coque en tamaños de 1 y 1.5 cm, la temperatura es la variable de interés, se registró por medio de 4 termocuplas ubicadas a 4 alturas diferentes al interior del recuperador (1, 7, 13 y 19 cm), los datos se ingresaron en las matrices de Excel avanzado 2010 en la función de regresión lineal múltiple. Excel permitió identificar 2 ecuaciones que predicen el comportamiento de la temperatura de la caliza y el coque. Se encontró que la recuperación de calor en la caliza es del 43% y para el coque es del 53% en un tiempo de una hora.

Adsorption of cyanide ions in aqueous solution using raw and oxidized coke

The objective of this study was the use of raw and modified coke material for the adsorption of cyanide ions (CN−) in water. The surface functions of this material (carboxyl, lactones, phenol, and carbonyl) were modified by oxidation with sulfuric acid, nitric acid, and KMnO4 solution at varying concentrations. This chemical surface treatment improved the adsorption capacity. The experimental results of adsorbent/adsorbate equilibrium show that the adsorption isotherms follow the Freundlich model and the kinetic adsorption follows the pseudo-second-order model. Overall, coke material oxidized by KMnO4 has shown the best adsorption of CN− ions with an adsorption capacity qe = 1.28 mg g−1 at T = 20°C and pH 11.

A Development of High Power Activated Carbon Using the KOH Activation of Soft Carbon Series Cokes

The process parameter in optimized KOH alkali activation of soft carbon series coke material in high purity was set with DOE experiments design. The activated carbon was produced by performing the activation process based on the set process parameters. The specific surface area was measured and pore size was analyzed by <TEX>$N_2$</TEX> absorption method for the produced activated carbon. The surface functional group was analyzed by Boehm method and metal impurities were analyzed by XRF method. The specific surface area was increased over 2,000 <TEX>$m^2/g$</TEX> as the mixing ratio of activation agent increased. The micro pores in <TEX>$5{\sim}15{\AA}$</TEX> and surface functional group under 0.4 meq/g were obtained. The contents of the metal impurity in activated carbon which is the factor for reducing the electrochemical characteristics was reduced less than 100 ppm through the cleansing process optimization. The electrochemical characteristics of activated carbon in 38.5 F/g and 26.6 F/cc were checked through the impedance measuring with cyclic voltammetry scan rate in 50~300 mV/s and frequency in 10 mHz ~100 kHz. The activated carbon was made in the optimized activation process conditions of activation time in 40 minutes, mixing ratio of activation agent in 4.5 : 1.0 and heat treatment temperature over <TEX>$650^{\circ}C$</TEX>.

Factors affecting the microwave coking of coals and the implications on microwave cavity design

The work carried out in this paper assessed how processing conditions and feedstock affect the quality of the coke produced during microwave coke making. The aim was to gather information that would support the development of an optimised microwave coke making oven. Experiments were carried out in a non-optimised 2450MHz cylindrical cavity. The effect of treatment time (15–120min), power input (750W–4.5kW) and overall power input (1700–27,200kWh/t) on a range of coals (semi-bituminous–anthracite) was investigated. Intrinsic reactivity, random reflectance, strength index and dielectric properties of the produced cokes were compared with those of two commercial cokes to assess the degree of coking produced in the microwave system.Overall energy input and coal rank were found to be the major factors determining the degree of coking following microwave treatment. The dependency on coal rank was attributed to the larger amount of volatiles that had to be removed from the lower ranked coals, and the increasing dielectric loss of the organic component of the coal with rank due to increased structural ordering. Longer treatment times at lower powers or shorter treatment times at higher powers are expected to produce the same degree of coking.It was concluded that microwave coke making represents a potential step-change in the coking industry by reducing treatment times by an order of magnitude, introducing flexibility and potentially decreasing the sensitivity to quality requirement in the feedstock. The main challenges to development are the energy requirements (which will need to be significantly reduced in an optimised process) and penetration depth (which will require an innovative reactor design to maximise the advantage of using microwaves). Understanding and quantifying the rapidly changing dielectric properties of the coal and coke materials is vital in addressing both of these challenges.