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  • Co-combustion behaviours of a low calorific Uruguayan Oil Shale with biomass wastes
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Martín Torres; Patrice Portugau; Jorge Castiglioni; Andrés Cuña; Luis Yermán

    In the present work thermal transport properties, thermochemical characteristics and gaseous pollutants released during co-combustion of different biomasses with oil shales (OS) were assessed using three different mass ratios (25%, 50% and 75% OS-biomass). The biomasses selected for carrying out the analysis were grape pomace (GP), rice husk (RH) and eucalyptus grandis (EG). In this sense, we demonstrated that the addition of biomass to the OS turns out having a positive effect, it improves the combustion index and diminishes the amount of pollutant emissions per energy unit released. Cone calorimeter tests were carried out in order to determine the effective heat of combustion (EHC) and subsequently the energetic combustion efficiency (EHC/HHV) taking as reference the higher heating value (HHV). The higher thermal diffusivity value was obtained for EG (0.161 mm2/s) and the lowest value was obtained for GP (0.105 mm2/s). The EHC/HHV ratio was obtained for a blending proportion of 50% for OS-EG (0.88–0.98). According to combustion index results, blends containing c.a 50% OS-EG reached a good burning performance of the combustion process, providing a potential OS-biomass ratio for being used as fuel. Moreover, the co-combustion emissions per energy unit released were analysed by means of TG-FTIR. CO2, CO and SO2 patterns showed that the emissions diminished with the addition of biomass to the OS. This paper aims to perform an assessment of the potential utilization of OS-biomass blends based on the biomass and OS composition, their thermal properties, gas emissions per energy unit released and EHC/HHV ratio.

    更新日期:2020-01-27
  • Transient pressure behavior for unconventional gas wells with finite-conductivity fractures
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Kien H. Nguyen; Miao Zhang; Luis F. Ayala

    Horizontal wells and hydraulic fracturing technologies are the only way that makes commercial production from the low and ultra-low permeability unconventional plays possible. The development of analytical and semi-analytical tools to analyze transient behavior of multi-fractured horizontal gas wells have been largely biased towards solving the simplified problem of one-dimensional (1D) Cartesian gas flow in matrix domain, which are only applicable to the production from infinite-conductivity fractures. This study presents a novel semi-analytical method for transient behavior analysis of horizontal gas wells producing from finite-conductivity fractures. Unlike the available transient analysis tools for finite-conductivity fractures which are developed based on empirical and approximate solution, the proposed solution is rigorously derived by solving the governing gas diffusivity equations written for gas flow in two contiguous regions of matrix and fracture simultaneously. Nonlinear, pressure-dependent gas properties remaining in pseudopressure-based diffusivity equations—namely viscosity and compressibility—are rigorously and straightforwardly captured in both fracture and matrix systems. The validity of proposed solution is verified against commercial numerical simulator (COMSOL Multiphysics®) for a series of synthetic cases considering constant and variable -rate production constraints. The case studies presented in this paper also showcase the applicability of proposed solution to the analysis of transient behavior of multi-fractured horizontal gas wells in shale plays under the following two state-of-the-art interpretations: 1) production from finite-conductivity hydraulic fractures in a single-porosity matrix; and 2) production from infinite-conductivity hydraulic fractures in a naturally-fractured matrix.

    更新日期:2020-01-27
  • Experimental studies on cyclic variations in a single cylinder diesel engine fuelled with raw biogas by dual mode of operation
    Fuel (IF 5.128) Pub Date : 2020-01-27
    C. Jagadish; Veershetty Gumtapure

    In this research work, cycle-by-cycle variations of a single cylinder, diesel engine operated with raw biogas is investigated. The biogas used to run the engine is obtained from food waste and as the composition of 88.10%-CH4 + 11.895%-CO2. To study the combustion characteristics, the naturally aspirated diesel engine is converted into dual mode by inducting the biogas into the intake manifold for different proportions from BG20 to BG60 with a step of 10% is mixed with air (i.e. BG60-60% of biogas by mass) respectively. Combustion parameters are measured and recorded by the means of the data acquisition system (DAQ) for 100 combustion cycle. By determining the parameters such as standard deviation, coefficient of variation and return map, the cycle variability is analyzed. From the experimental result, it is observed that as the engine is operated at higher loads and as the biogas is increased from BG20 to BG60 the cyclic variations for maximum cylinder pressure (Pmax) and indicated mean effective pressure (IMEP) increases. Coefficient of variation of Pmax for BG20 and BG40 is lower by 2.3% and 11.98% as compared to diesel. From time return map, BG40 showed good combustion stability and lesser NOx emission compared to diesel.

    更新日期:2020-01-27
  • Alkaline pretreatment of yerba mate (Ilex paraguariensis) waste for unlocking low-cost cellulosic biofuel
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Antônio Djalma Nunes Ferraz Júnior; Maria Ines Etchelet; Adriana Ferreira Maluf Braga; Leonardo Clavijo; Inés Loaces; Francisco Noya; Claudia Etchebehere

    Yerba mate (Ilex paraguariensis) is one of the most popular hot drinks in the world and might represent an opportunity for energetic valorization after its consumption. Alkaline pretreatment appears to be a potential strategy for unlocking cellulosic biofuels. Thereby, in this study, four alkaline agents were evaluated for improving yerba mate anaerobic digestion (AD): (1) sodium hydroxide (NaOH); (2) potassium hydroxide (KOH); (3) lime; and (4) sodium bicarbonate. Complete factorial design with center point repetition was chosen to evaluate all combinations of concentration of alkali (50, 125, and 200 galkaline agent kg−1dry yerba mate), reaction time (12.2, 30.1, and 48 h) and temperature (30, 65, and 100 °C) in carbohydrate solubilization (variable response). Pre-treatment harshness was quantified by the modified severity factor (MSF). The methane production potential was determined for the best pretreatment condition achieved for each alkali tested. Energy balance for assessing the effectiveness of the proposed treatments on net energy gain was performed. NaOH and KOH had the same effect on organic matter solubilization and produced the same optimum value for the MSF. Thermal-alkaline pretreatment of yerba mate can increase the methane yield up to seven-fold as compared to control (maximum cumulated methane yield of 700 N-LCH4.Kg-VS−1added). All of the alkalis evaluated in the yerba mate pretreatment improved the kinetics of the AD process (kh; from 1e−5 to 1e−1 d−1). NaOH pretreatment at its highest levels of alkali concentration and temperature and lowest level of reaction time was found to be the best scenario in terms of net energy gain.

    更新日期:2020-01-27
  • Dilute sulfonic acid post functionalized metal organic framework as a heterogeneous acid catalyst for esterification to produce biodiesel
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Fengsheng Liu; Xiaoling Ma; Hui Li; Yangyang Wang; Ping Cui; Min Guo; Helian Yaxin; Wanpeng Lu; Shoujun Zhou; Mingzhi Yu

    In order to synthesize the efficient heterogeneous acid catalyst for biodiesel production, concentrated sulfuric acid (>18.4 mol/L) is commonly used as sulfonated reagent to anchor sulfonic acid group (SO3H) on a support. However, large amount of wastewater is generated while the concentrated sulfuric acid removed by washing. In this study, a green and highly stable sulfonated catalyst is prepared by using MIL-100(Fe), which is functionalized by the dilute sulfonic acid. The obtained catalyst is adopted to catalyze the esterification of methanol and oleic acid. Meanwhile, it is characterized by thermogravimetry analysis (TG), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), pyridine FTIR spectroscopy (Py-FTIR), scanning electron microscope (SEM), Hammett indicator titration and nitrogen adsorption-desorption. The maximum esterification conversion of 95.86% is achieved at molar ratio of methanol to oleic acid of 10, catalyst amount of 8 wt% (referred to oleic acid mass) at 70 °C within 2 h. More importantly, the catalyst could be repeatedly used for six cycles without significant activity loss.

    更新日期:2020-01-27
  • Hydrogen effect on lean flammability limits and burning characteristics of an isooctane–air mixture
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Fushui Liu; M. Zuhaib Akram; Han Wu

    The flammability limit is a hurdle to realizing ultra-lean combustion and achieving high thermal efficiency in spark ignition engines. Hydrogen, known for its wide explosion limits, has been utilized in gasoline to improve the lean limit. The influence of hydrogen on lean flammability limits of isooctane was studied at initial temperatures of 393–513 K and an ignition energy (IE) of 3000 mJ, while the burning characteristics were studied at an initial temperature of 393 K and IE = 37 mJ. It is found that a spherical flame appeared when the isooctane–air–H2 mixture was ignited from λ = 0.8 to λ = 1.2 at IE = 37 mJ, whereas a leaner mixture was burnt at IE = 3000 mJ with unstable flame growth during the early stage. Flame instability eventually evanesced and buoyancy was observed near the lean limits. The lean limits of isooctane–air increased to 2.1λ with 0–90% hydrogen. Raising the initial temperature from 393 to 513 K increased the lean limits of isooctane–air–H2 to 0.2λ. Hydrogen obtained from CH2O (C, H, and O species) makes a considerable contribution to improving the burning near the lean limits. The mole fraction of the short-lived radicals H, OH, and O decreased when the excess air coefficient moved toward the lean limits and increased by introducing hydrogen, which improved the lean flammability limits and burning velocity.

    更新日期:2020-01-27
  • Analysis of deposits from combustion chamber of boiler for dendromass
    Fuel (IF 5.128) Pub Date : 2020-01-27
    Beatrice Plešingerová; Bora Derin; Pavol Vadász; Dávid Medveď

    This article records the degradation of the refractory alumina-silicate lining in a boiler furnace combusting dendromass after ten years of use. The deterioration of refractory alumina material was evaluated from phase and chemical analyses of accretions. The fusion temperatures of accretion were measured with a high-temperature microscope and the results were compared with the solidus (point of first liquid formation) temperature predicted by FactSage 7.3 thermodynamic simulation software. Content of SiO2 (50–65%) in accretions confirms that fine silicate particles of ash adhere to the lining. These silicates react with subliming alkalis from the dendromass and form aggressive eutectic melts on surface of lining at operating temperatures. Increase in operating temperature, inhomogeneity (porosity) and alkali content in accretions are the main factors influencing accretion viscosity, melt convection and lining corrosion. For this reason accretions on the vertical walls lower down are much thicker than on the walls in the upper part and the arch. The Al2O3 concentration is higher in the arch accretions; there the refractory material corrodes intensively. The fusion temperatures of the glassy accretions (measured at the furnace atmosphere: accretion boundary) are around 1150 °C. However, the calculated temperatures of slag formation stated by FactSage are about 150 °C lower, and these correspond to the operating temperature in the upper section of the combusting chamber. The fusion temperatures increase with the Al2O3 content in accretions closer to the lining. The obtained results will be applied to define the requirements for the development of boiler furnace refractories.

    更新日期:2020-01-27
  • Modelling of flammable fuels in small and large scale turbulent environments
    Fuel (IF 5.128) Pub Date : 2020-01-27
    M.A. Yehia; M.A. Abdel-Raheem

    This paper presents a mathematical modelling analysis of two propagating flames inside small and large enclosures of different geometrical configurations via computational fluid dynamics. Fuels considered are hydrogen and methane respectively. As the reactivity of the two fuels vary, time histories of over-pressure and flame position vary accordingly. The level of turbulence produced due to impinging the propagating flame with obstructions drives the location of flow amongst the combustion regime diagram and thus controls the validity of combustion models used. In the present study, the large eddy simulation (LES) technique as fitted in ANSYS Fluent is employed. The turbulent flame speed closure (TFC) is selected with revisiting the validity of its standard formulation. As the interaction of the propagating flame with obstructing walls is considered to be a key feature on determining the turbulence levels attained, it was sought to compare two models, namely the Dynamic Smagorinsky-Lilly and WALE models. Despite the fact that small scale experimental facilities are more adequate for producing detailed diagnostics of the deflagration scenario experimentally as well as allowing LES analysis with a reasonable mesh size within computational economy, it was recognized that the terminal objective is to evaluate the level of performance when dealing with large scale cases. The agreement between the predictions and set of experimental measurements used suggests a reasonable level of qualitative agreement for all different cases, providing a better understanding of models used to simulate the phenomena involved with discrepancies spotting light on areas of potential future improvements.

    更新日期:2020-01-27
  • Maximization of biodiesel production from sunflower and soybean oils and prediction of diesel engine performance and emission characteristics through response surface methodology
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Medhat Elkelawy; Hagar Alm-Eldin Bastawissi; Khaled Khodary Esmaeil; Ahmed Mohamed Radwan; Hitesh Panchal; Kishor Kumar Sadasivuni; Muthusamy Suresh; Mohammad Israr

    Production of methyl ester from sunflower and soybean oil mixture is performed throughout a catalyzed transesterification procedure. The significance of the four reaction parameters such as methanol to oil ratio, catalyst concentration, mixing speed, and reaction time and their combined effect on biodiesel yield is investigated through twenty-nine of the pre-designed and performed experiments. Box-Behnken design (BBD) based on response surface methodology (RSM) was applied for process optimization. A quadratic regression model was established for biodiesel yield prediction with a coefficient of determination R2 of 0.9861. An maximum biodiesel yield of 93.38% is accomplished at 203.5:1 ml:l methanol to oil ratio, 0.57 wt% catalyst concentration, 52 min reaction time and 530 rpm mixing. Obtained results show that there is a superior compatibility among the calculated yield of 93.38% and the experimental data of 93.2%. The estimated biodiesel fuel properties met with the American society for testing and materials (ASTM) D6751 standards. Engine operating parameters optimization have been executed using central composite design method (CCD) to achieve an optimum break thermal efficiency of a lone cylinder DI-engine fueled by biodiesel/diesel mixtures. Engine input parameters were considered as engine load and blends percentage for the optimization of engine response represented in break thermal efficiency (BTE), unburned hydrocarbon (UHC), and Nitrogen oxide (NOx) emissions. Examination of inconsistency (analysis of variance) ANOVA indicated that the quadratic representation were statistically important. RSM optimizer results indicated that the best possible values of BTE, UHC, and NOx were 13.656%, 120.7748 ppm, and 234.8926 ppm, respectively, at the maximum value of biodiesel mixture of 70% and break power of 2.05 kW. A validation test was performed and the error percentage is found to be within the range of 5%. The error percentage for BTE, UHC, and NOx was found to be 3.34%, 1.35%, and 2.31%, respectively.

    更新日期:2020-01-26
  • Adsorption kinetics in removal of basic nitrogen-containing compounds from practical heavy oils by amorphous silica-alumina
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Satoshi Suganuma; Kohsuke Arita; Fumiya Nakano; Etsushi Tsuji; Naonobu Katada
    更新日期:2020-01-26
  • Microscopic investigation of layer growth during olivine bed material aging during indirect gasification of biomass
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Robin Faust; Mohammad Sattari; Jelena Maric; Martin Seemann; Pavleta Knutsson

    Olivine bed material used in an aging experiment for indirect gasification in the Chalmers 2–4-MWth DFB gasifier was investigated with the aim to determine the mechanism of layer formation around the particles upon exposure to gasification conditions. The collected samples were exposed for 1, 2 and 4 days. The development of ash layer around the bed material particles was studied with different analysis methods. Formation of Ca3Mg(SiO4)2 and MgO was confirmed by X-ray diffraction (XRD). Cross-sections of the bed material samples were prepared using Broad Ion Beam (BIB) milling and were further analyzed with Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM-EDS). The analysis of the produced cross-sections revealed the formation of a Mg-rich surface layer on top of the Ca-rich ash layer. Minor amounts of K were also found near the sample surface. Based on the results from the characterization techniques, a reaction mechanism involving the transition of Mg2SiO4 with CaO to MgO and Ca3Mg(SiO4)2 was suggested which was confirmed by equilibrium calculations. This mechanism was supported by Transmission Electron Microscopy (TEM) analysis where diffraction patterns corresponding to MgO were found. TEM-EDS line-scan revealed the presence of ash components in the ash layer such as P and Ti at locations coinciding with high levels of Ca which indicates the formation of Ca3(PO4)2 and CaTiO3. The results presented provide detailed information on the composition of the ash layer which can be used to fully understand the mechanism responsible for the formation of catalytically active ash layers.

    更新日期:2020-01-26
  • Moisture adsorption and spontaneous combustion characteristics of biomass wastes after degradative solvent extraction
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Xianqing Zhu; Weixiang Qian; Xian Li; Shan Tong; Zhenzhong Hu; Yun Huang; Ao Xia; Hong Yao

    The inherent disadvantages such as high oxygen content, low energy density, high moisture adsorption propensity and high spontaneous combustion tendency, have limited the widespread utilization of lignocellulosic biomass. A novel degradative solvent extraction (DSE) method has been recently developed to deoxygenate and upgrade biomass into two high-quality extracts (Soluble and Deposit) with various high-value applications. However, the moisture adsorption and spontaneous combustion characteristics of Soluble and Deposit still remain unclear, which are important for the safe storage, transportation and subsequent application of Soluble and Deposit. Therefore, in this study, the moisture adsorption and spontaneous combustion characteristics of Soluble, Deposit as well as raw biomass were investigated and compared. The moisture adsorption ratios of Soluble and Deposit were lower than 1.5% and 2.5% respectively, which were significantly lower than that of raw biomass, indicating that degradative solvent extraction greatly inhibited the moisture adsorption propensity of biomass. The ignition temperatures of Soluble and Deposit were at least 110 °C higher than that of raw biomass, and the activation energy of low temperature oxidation of Soluble and Deposit were 1.2–2.0 times higher than that of raw biomass. Soluble and Deposit had much higher weight loss temperature, heat release temperature, ignition temperature and higher activation energy of low temperature oxidation, revealing that the spontaneous combustion tendency of Soluble or Deposit was also significantly suppressed in comparison with raw biomass. The physicochemical properties of raw biomass, Soluble and Deposit were detailedly characterized, and it can be concluded that the low content of oxygen-containing functional groups, poor pore structure and dense surface structure jointly suppressed the moisture adsorption propensity and spontaneous combustion tendency of biomass after degradative solvent extraction. This research proves that degradative solvent extraction could not only achieve the upgrading of biomass but also inhibit the moisture adsorption propensity and spontaneous combustion tendency of biomass.

    更新日期:2020-01-26
  • Techno-economic assessment of process integration models for boosting hydrogen production potential from coal and natural gas feedstocks
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Usman Hamid; Ali Rauf; Usama Ahmed; Md. Selim Arif Sher Shah; Nabeel Ahmad
    更新日期:2020-01-26
  • The optimal carbon and hydrogen balance for methanol production from coke oven gas and Linz-Donawitz gas: Process development and techno-economic analysis
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Sunghoon Kim; Jiyong Kim

    This study addresses the simulation and techno-economic analysis of novel methanol production processes by the combined feeding of hydrogen-rich coke oven gas (COG) and carbon-rich Linz-Donawitz gas (LDG). The optimal operating scheme and conditions to ensure the most favorable carbon and hydrogen balance of the proposed processes, maximized methanol production and polygeneration of methanol, power, and heat, were determined through a rigorous process simulation with a sequential quadratic programming optimization. A techno-economic analysis revealed that two combined-feeding processes show an improved technical and economic performance compared to the conventional methanol production process involving separated feeding of COG and LDG. The primary energy efficiency and minimum methanol selling price of the proposed processes were 51% and 60%, and 265 and 370 USD/ton, respectively, which were greatly improved compared to the base process. In addition, the CO2 emissions of the two processes (0.41 and 1.03 kg of CO2 per kW) imply that adjusting the optimal carbon and hydrogen balance is an important strategy to produce economically viable and environmentally clean methanol from residue gases of the steel industry.

    更新日期:2020-01-26
  • Effects of bubbles in the liquid jet on the air-blast atomization
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Zhao-Wei Wu; Zhe-Hang Shi; Hui Zhao; Feng Yao; Hai-Feng Liu; Wei-Feng Li; Jian-Liang Xu

    The air-blast atomization with bubbles in the liquid jet was investigated using the high-speed camera and Malvern laser particle size analyzer. The gas was aerated into the liquid jet to form the gas-liquid mixture, which would be atomized by the co-flowing air stream. Results show that droplet size D32 decreases at the beginning and then increases with the volumetric flow rate of the aerating gas. A formula was derived to delineate the nonmonotonic trend of the droplet size. The relative deviations between the predicted results and experimental results are less than ±5%. A contour map describing the dependence of the droplet size on the aerating gas, liquid jet, and co-flowing air stream was obtained, which could provide some guidance for the further investigations and industrial applications.

    更新日期:2020-01-26
  • Autoignition and detonation characteristics of n-heptane/air mixture with water droplets
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Yijie Zhuang; Qiang Li; Peng Dai; Huangwei Zhang

    The present study addresses the autoignition and detonation characteristics of n-heptane/air mixture with water droplets in a confined one-dimensional reactor. A Eulerian-Eulerian formulation for gas and liquid phases is employed to simulate multi-component, fully compressible and reactive multi-phase flows. The parametric investigations covering a range of droplet diameters and number densities are conducted to understand the reaction front development in gas phase and droplet evaporation characteristics under different gaseous combustion conditions. Four modes of autoignition behaviours in the reactor are identified and they are found to greatly depend on both droplet diameter and number density. At a relatively small droplet diameter and/or number density, detonation is initiated by hot spot but no autoignition occurs at the right boundary. When both or either of them increase, autoignition occurs at the right boundary and the reaction front may further evolve into detonative or deflagrative waves. This is because the temperature inhomogeneity in that region is considerably enhanced. Furthermore, droplet diameter and number density are used to quantify the different modes of autoignition and detonation development. For the droplet evaporation dynamics during the reactive front development process, various mechanisms are observed, related to the different effects dominated by the velocity difference between two phases (characterized by the droplet Reynolds number), high local gas pressure and also the droplet temperature. This results in non-monotonic spatial distributions of droplet evaporation rate in the reactor, e.g. M-shaped in the detonated or shocked regions.

    更新日期:2020-01-26
  • Studies of the storage and transport of water and oil in organic-rich shale using vacuum imbibition method
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Shaojie Zhang; Yinghui Li; Hui Pu

    The inorganic pores, organic pores, and kerogen matrix are important media to store water and oil in shale rocks. We present a vacuum imbibition method to identify the volume of water and oil in these media. Before the experiments, comprehensive rock characterizations were carried out on shale samples from Shahejie Formation combining various methods including N2 adsorption, scanning electron microscope (SEM), X-ray diffraction, and RockEval pyrolysis. Total organic carbon (TOC) accounts for 1.59–5.97% of total rock weight. Kerogen thermal maturity (Ro) of the studied samples is 0.62–1.05%. Then, vacuum imbibition experiments were conducted on shale samples using water and n-dodecane. The accurate volumes of water in organic pores, oil in inorganic pores and organic pores, and the volume of dissolved oil were determined from vacuum imbibition experiments. The effects of Ro on shale storage were analyzed. Furthermore, novel mathematical models of oil and water vacuum imbibition in shale were proposed. The water imbibition in inorganic pores is a capillary flow. The oil imbibition in shale includes capillary flow in pore structures and diffusion in kerogen. The pore-kerogen double diffuse layer (PKDDL) physical model was proposed for the mechanisms of the hydrocarbon mass transfer between pore structures and kerogen. The capillary pressure and the dissolution rate constants were obtained by matching mathematical models with experimental results. This study provides new methods to evaluate the water and oil storage and transfer in organic-rich shale and advances the crucial mechanisms for the evaluation and development of shale reservoirs.

    更新日期:2020-01-26
  • Pyrolytic conversion of biowaste-derived hydrochar: Decomposition mechanism of specific components
    Fuel (IF 5.128) Pub Date : 2020-01-24
    Xiuzheng Zhuang; Yanpei Song; Hao Zhan; Xiaotao T. Bi; Xiuli Yin; Chuangzhi Wu

    Hydrothermal carbonization (HTC) coupled with subsequent downstream conversion is a new concept for the utilization of industrial biowastes for energy production. In this work, three representative biowastes (i.e., lignocellulosic, non-lignocellulosic and ash-rich samples) were selected for HTC pretreatment, and the subsequent pyrolysis of the derived hydrochars was evaluated using multiple kinetic models and combined instrumental analyses. Results showed that the thermal weight loss peak for each biowaste was progressively shifted to a higher temperature after HTC pretreatment, while the maximum value of weight loss was reduced compared to that of the original feedstock. This change was shown to be caused by the shift in biowaste compositions to a more stable one in the hydrothermal stage, but the dissimilarity of evolution pathways among specific components affected the rate and degree of pyrolysis of the hydrochars to different extent. In addition, fewer volatile compounds were released during the pyrolysis of the hydrochars, and the composition of pyrolytic volatiles was found to be mainly dependent on the types of biowaste and HTC conditions. These findings not only provide essential information on the pyrolytic capability of HTC-derived hydrochars, but can also help in designing, optimizing and scaling up the thermochemical conversion of industrial biowastes.

    更新日期:2020-01-26
  • A model for droplet heating and evaporation of water-in-oil emulsified fuel
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Shiquan Shen; Zhizhao Che; Tianyou Wang; Zongyu Yue; Kai Sun; Sibendu Som

    Water-in-oil (W/O) emulsified fuel is a promising alternative fuel by inducing flash boiling of water at high temperature that can improve the atomization of fuel spray. The heating and evaporation process of emulsified fuel droplet is affected by the diffusion and coalescence of small dispersed water droplets in oil during the heating. In this study, a model is developed for the droplet heating and evaporation of W/O emulsified fuel with these key physics considered. The diffusivity of dispersed water droplets in oil is calculated using the Stokes-Einstein equation. The deactivation temperature of surfactant is selected as a criterion for the water coalescence since the water coalescence is due to the deactivation of surfactant. The process of water coalescence is simplified that the dispersed water droplets coalesce into one single water sub-droplet at the center of the oil droplet instantly as the droplet temperature reaches the deactivation temperature of surfactant. The model is validated against experimental data of single droplet under different heating temperatures, surfactant concentrations, and sizes of dispersed water droplets. Based on the proposed model, the effects of fuel properties and heating conditions on the droplet heating and evaporation are analyzed.

    更新日期:2020-01-26
  • Synthesis of improved hydrochar by microwave hydrothermal carbonization of green waste
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Yuchao Shao; Hao Tan; Dongsheng Shen; Ying Zhou; Zhiyuan Jin; Dan Zhou; Wenjing Lu; Yuyang Long
    更新日期:2020-01-26
  • Mechanistic insight into the optimal recovery efficiency of CBM in sub-bituminous coal through molecular simulation
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Xiao-Qiang Liu; Meijun Li; Chenghua Zhang; Ronghui Fang; Ningning Zhong; Ying Xue; Yang Zhou; Weidong Jiang; Xu-Yang Chen
    更新日期:2020-01-26
  • New mechanism insights into methane steam reforming on Pt/Ni from DFT and experimental kinetic study
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Juntian Niu; Yalan Wang; Yanying Qi; Anh H. Dam; Hongmin Wang; Yi-An Zhu; Anders Holmen; Jingyu Ran; De Chen

    In this contribution, we combine density functional theory (DFT) calculations, experimental kinetic study and DFT-assisted analysis to elucidate the impact of the interface of monolayer Pt on the Ni surface on catalytic performance of steam methane reforming including carbon formation on core-shell ([email protected]) catalysts and compare it with Ni and Pt catalysts. We demonstrate that core-shell structured [email protected] significantly lowers the carbon formation without sacrificing much the activity. The DFT results demonstrate that the metal identity, core shell structure and support have significant impacts on the reaction mechanisms. The direct methane activation is energetically favorable reaction pathway on Ni, while the OH* assisted methane activation is the favorable pathway on Pt and [email protected] catalysts, where methane activation is the rate-determining step on all catalysts. We unambiguously reveal that the core-shell [email protected] catalyst modified the surface Pt electron density and shifted d-band center away from Fermi level compared to Ni(1 1 1) and Pt(1 1 1). It results in a strong basic surface OH* which actively reacts with CHx and thus enhances carbon formation resistance. Above all, Ni-core/Pt-shell particle could decouple the activity and carbon resistance to keep the activity and reduce carbon formation simultaneously in methane steam reforming. In addition, by taking into account the activation of steam on the support, the effective activation energy estimated from DFT-assisted analysis is well consistent with the experimental value on the both Ni and [email protected] catalysts, which could shed some light on building a bridge between experimental work and DFT-assisted kinetic study.

    更新日期:2020-01-26
  • Thermochemical, kinetic and ash characteristics behaviour of Thar Lignite, agricultural residues and synthetic polymer waste (EVA)
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Abdul Wahab; Hamed Sattar; Asma Ashraf; Syed Nadir Hussain; Mahmood Saleem; Shahid Munir

    The study aimed to exploit the energy potential of naturally occurring fuels like Thar Lignite (TL), Sugarcane Bagasse (SB), Cotton Stalks (CS) and synthetic copolymer shoe manufacturing waste Ethylene Vinyl Acetate (EVA). Proximate, ultimate, chemical analysis along with Fourier transform infrared (FTIR) were carried out to analyze the compositional and structural differences between the studied fuel samples. Thermochemical decomposition of fuel samples was also evaluated using thermogravimetric analysis (TGA) under dry air conditions. Derivative thermogravimetry (DTG) obtained from TG curves were used to determine the ignition, peak, burnout temperatures along with combustion performance indices. The order of both average and peak rate of conversion (% s−1) was found to be; EVA > SB > CS > TL. Kinetic analysis of the samples was performed using Coats Redfern model. The apparent activation energy ‘Ea’ (kJ mole−1) was in the order of SB = 45.7 > EVA = 36.2 > CS = 36.1 > TL = 23.1. X-ray fluorescence (XRF) and ash fusion temperature (AFT) profile analysis of the ash samples was also performed to investigate the possible deposit formation propensity of post combustion residue products, alkali and slagging indices. SB showed the highest propensity towards slagging deposit formations with the order SB > CS > TL > EVA.

    更新日期:2020-01-26
  • Product property and environmental risk assessment of heavy metals during pyrolysis of oily sludge with fly ash additive
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Ningbo Gao; Jiaqi Li; Cui Quan; Houzhang Tan

    Oily sludge is mainly engendered during crude oil exploitation, transportation and refining process. The effect of fly ash additive on the product distribution and property of oily sludge pyrolysis was studied by employing a fixed-bed reactor at 600 °C in this paper. The fly ash additives could enhance the yields of oil and gas from oily sludge pyrolysis. The highest pyrolysis oil and gas yields were achieved at 30.43 wt% and 11.56 wt% when the fly ash content is 50.0 wt%. The characteristic of the pyrolysis oil was determined by GC/MS and FTIR analysis. Hydrocarbon-type analysis showed that addition of fly ash to the oily sludge decreased the content of aromatic hydrocarbons and non-hydrocarbons (resins and heterocycles). The molecular weight of straight chain alkanes reduced with the increase of fly ash content (16.7–50.0 wt%). The lower heating value (LHV) of pyrolysis gas is in the range of 16.62–19.88 MJ/Nm3. The XRF results illustrated that pyrolysis char contains high concentrations of Fe, Ba, Si and Ca. The distribution of heavy metals (Pb, Zn, Cr, Cu, Ni, Cd, As and Hg) and the ecological risk related to the oily sludge and pyrolysis char were investigated by ICP. The results of this study showed that the potential ecological risk index values of oily sludge, fly ash and pyrolysis char without or with 50.0 wt% fly ash were 220.40, 246.99, 234.33 and 265.85, respectively. The heavy metals of oily sludge, fly ash and pyrolysis chars would be categorized as moderate risk.

    更新日期:2020-01-26
  • Simulative prediction of ultrafine particulate matter formation by means of different pyrolysis models
    Fuel (IF 5.128) Pub Date : 2020-01-25
    Christian Axt; Stefan Pielsticker; Thobias Kreitzberg; Oliver Hatzfeld; Qi Gao; Shuiqing Li; Reinhold Kneer

    In this study, the sensitivity of two different pyrolysis models on the simulative prediction of inorganic ultrafine Particulate Matter (PM) formation is investigated. For consideration of PM formation, the volume-conserved discrete-sectional Population Balance Model (PBM) is used. The volatile release is an input parameter of the PBM and thus influences the calculated PM formation. As a representative of an empirical pyrolysis model, the Fu-Zhang model (FZM) is used. In comparison, the Chemical Percolation Devolatilization model (CPD) is taken as a representative for sophisticated pyrolysis network models. The latter takes influences of fuel composition, heating rate and particle temperature into account. The evaluation of the pyrolysis model impact is determined for a pulverized (dp=65–74μm) Chinese lignite (Zhundong) since this fuel has a relatively high volatile content and thus favors the formation of particulate matter. To investigate the influence of particle heating rate in the models, two different gas temperatures (1200 K and 1500 K, respectively 5.28·104 K s−1 and 7.51 × 104 K s−1 calculated with the energy balance) are considered. Furthermore, these conditions are selected because experimental data of the PM particle size distribution (PSD) from previous studies are available. The modeling of PSD is performed and validated with the existing experimental PSD data. These experimental data were achieved in investigations with a Hencken burner. The results of the two models (FZM and CPD) show recognizable differences in predicting the PSD. This study indicates that the CPD model improves significantly the prediction of ultrafine PM formation.

    更新日期:2020-01-26
  • Biodegradability of quinoa stalks: The potential of quinoa stalks as a forage source or as biomass for energy production
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Gökhan Filik

    This study was carried out to determine the potential of quinoa stalks, left as waste in the fields after harvest, to be converted into roughage for animal feed or as biomass for energy production. The quinoa stalks were harvested from cultivated fields in Şanlıurfa, Turkey, and the biochemical and thermochemical potential conversion of the quinoa stalks to forage feed or biomass was then determined. A chemical and basic element analysis of the quinoa stalks was carried out. In terms of animal feeding potential that involved the in vitro digestibility and metabolizable energy value. In terms of biomass potential, the syngas values and other gases: estimated methane (CH4), biodegradability, total biogas production value and higher heating value, were also all determined. According to ADL DM% analysis value (46.49 ± 0.97) and calculated relative feed value (RFV, 71.09) results showed that quinoa stalks have a very poor potential as forage and cannot be regarded as roughage. However, with an energy value of 18.27 MJ/kg was determined that quinoa stalks could be used as an energy producing plant.

    更新日期:2020-01-24
  • Optimized conversion of waste cooking oil to biodiesel using modified calcium oxide as catalyst via a microwave heating system
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Ming-Chien Hsiao; Jui-Yang Kuo; Shu-An Hsieh; Pei-Hsuan Hsieh; Shuhn-Shyurng Hou

    Homogeneous catalysts have been commonly utilized during the production of biodiesel in industrial applications. However, a homogeneous catalysis system has several disadvantages, including difficulties related to the separation of the reactant and products and the pollution of wastewater after the chemical washing process. However, transesterification through heterogenous catalysis avoids the aforementioned drawbacks in the homogeneous catalysis process. In this study, a novel modified calcium oxide (CaO) is proposed as an alkaline solid catalyst. The surface of commercial CaO is chemically modified using bromooctane through a microwave approach to improve its catalytic ability. The physiochemical characteristics of the modified CaO are analyzed using a Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results show that microwave heating significantly reduces the synthesis time for the modified CaO, which was found to be one twelfth that of traditional water-bath heating. In addition, calcium hydroxide (Ca(OH)2) was rarely generated during the modification procedure, and microwave-modified CaO was found to have better thermos-stability. The optimal reaction conditions are as follows: a 4 wt% catalyst, a methanol-to-oil molar ratio of 8:1, a reaction temperature of 65 °C, and a reaction time of 75 min. Under these conditions, the biodiesel conversion reaches 98.2%, while the reaction time (75 min) is only 53.6% of the traditional water bath heating transesterification reaction (140 min).

    更新日期:2020-01-24
  • Autoignition study of methyl decanoate using a rapid compression machine
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Wenyu Wang; Liang Yu; Yuan Feng; Yong Qian; Dehao Ju; Xingcai Lu

    Methyl decanoate (MD), a widely used surrogate of biodiesels, was investigated for its autoignition characteristics using a heated rapid compression machine (RCM). In this study, the ignition delay times (IDTs) of MD were measured at the compressed pressures of 5–20 bar, equivalence ratios varying from 0.53 to 1.60 and compressed temperatures of 633–855 K. An obvious two-stage ignition behavior was observed at low temperatures and typical negative temperature coefficient (NTC) phenomenon of total IDT was experimentally captured. The influences of compressed pressure, fuel and oxygen content, and nitrogen concentration on ignition delay times were systematically studied. The simulation results of Herbinet’s mechanism and Grana’s mechanism under variable volume simulation were compared with the experimental data. It is found that the two mechanisms qualitatively predict the autoignition features of MD but still need further optimization. In addition, reaction pathway analysis and sensitivity analysis were conducted to offer further insight into the low-to-intermediate temperature autoignition chemistry of MD.

    更新日期:2020-01-24
  • Hydrocarbon saturation in shale oil reservoirs by inversion of dielectric dispersion logs
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Peiqiang Zhao; Jinhua Fu; Yujiang Shi; Gaoren Li; Mehdi Ostadhassan; Miao Luo; Zhiqiang Mao

    Hydrocarbon saturation is an important petrophysical parameter in reservoir evaluation and reserve calculation. Dielectric dispersion logs have been widely used to estimate the hydrocarbon saturation, especially in high salinity shale formations. However, there is still room to improve the accuracy of interpretation of dielectric dispersion logs. In this paper, we used two interpretation models combined four dielectric permittivity and four conductivity logs measured by Array Dielectric Tool (ADT) at four frequencies to predict the hydrocarbon saturation in shale oil reservoirs, Triassic Yanchang Formation, Ordos Basin, China. The logs measured at the highest frequency are interpreted by the Complex Refractive Index (CRIM) model. And the other three frequencies measured logs are processed by the shaly sandstone (SHSD) model. Based on the two models, simulated annealing algorithm is selected to calculate water saturation and rock textual parameter, the dispersive phase fraction, and water salinity. Besides, accurate porosity, dielectric permittivity of rock matrix, and temperature are input information to the proposed method. The proposed method is applied to shale oil reservoirs of Triassic Yanchang Formation in two wells. The effectiveness and reliability of proposed model is verified by synthetic log responses. The mean relative error between synthetic and field logs is small. The predicted hydrocarbon saturation is consistent with core data, and its variation is consistent with characteristics of NMR T2 distributions, verifying the accuracy and reliability of proposed method and inversion results. Our estimated hydrocarbon saturation of the two wells is about 30%, showing a good oil generation potential of the studied shale oil reservoirs.

    更新日期:2020-01-24
  • Experimental study on modification of physicochemical characteristics of acidified coal by surfactants and ionic liquids
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Weibo Han; Gang Zhou; Qingtao Zhang; Hongwei Pan; Dong Liu
    更新日期:2020-01-24
  • 更新日期:2020-01-24
  • Regenerable CoxMn3−xO4 spinel sorbents for elemental mercury removal from syngas: Experimental and DFT studies
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Zhen Wang; Jing Liu; Yingju Yang; Yingni Yu; Xuchen Yan; Zhen Zhang
    更新日期:2020-01-23
  • Visible-light-driven selective oxidation of methane to methanol on amorphous FeOOH coupled m-WO3
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Juan Yang; Jingyi Hao; Jianping Wei; Jun Dai; Yao Li
    更新日期:2020-01-23
  • Effect of water occurrences on methane adsorption capacity of coal: A comparison between bituminous coal and anthracite coal
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Feng Wang; Yanbin Yao; Zhiang Wen; Qinping Sun; Xuehao Yuan

    In this study, an NMR fluid typing method was applied to two typical anthracite and high volatile bituminous coals to identify different occurrence states of water (adsorbed and non-adsorbed water), and multiphase methane (adsorbed, porous medium confined, and bulk methane) and investigate the effect of the water occurrence states on methane adsorption capacity. First, results of isothermal adsorption analysis conducted using the NMR method was compared to those from conventional volumetric method to verify the precision of the NMR method. Then the influence of adsorbed water and non-adsorbed water on methane adsorption was examined based on two parallel treatments. For bituminous coal, the adsorbed water remarkably reduced the Langmuir adsorption volume, whereas adding non-adsorbed water had no effect on gas adsorption. In contrast, for anthracite coal, the methane adsorption capacity revealed a downward trend with increase in both adsorbed water and non-adsorbed water. The explanation is that adsorption competition between water molecules and methane gas molecules can constrain further adsorption of methane on the coal matrix. Thus, adsorbed water negatively impacts gas adsorption for both anthracite and bituminous coal. In terms of non-adsorbed water, due to the superior pore conductivity and hydrophilia of bituminous coal, methane gas can easily pass through the pores in the presence of non-adsorbed water, compared to anthracite, where water blocking and the Jamin effect tend to occur. Even water droplets formed because of anthracite’s hydrophobicity can utterly block the pore throats, resulting in a continuous decrease in methane adsorption capacity. The implications of this study are important for better understanding the influence of various occurrence states of water on the adsorption/desorption processes in unconventional reservoirs.

    更新日期:2020-01-23
  • Optical study on autoignition and knocking characteristics of dual-fuel engine under CI vs SI combustion modes
    Fuel (IF 5.128) Pub Date : 2020-01-23
    Lin Chen; Ren Zhang; Jiaying Pan; Haiqiao Wei

    Uncontrollable autoignition with engine knock has been the main obstacle for high thermal efficiency and low CO2 emissions in downsized engines. Therefore, it is necessary to study the autoignition and knocking characteristics and reveal the similarities/differences between different combustion modes. In this study, synchronization measurement was performed through simultaneous pressure acquisition and high-speed natural flame acquisition, and knocking experiments were comparatively conducted under spark-ignition (SI) and compression-ignition (CI) conditions in a high-strength optical engine. The CI experimental results show that early ignited fuel injection leads to advanced combustion phase thus concentrated heat release. The advanced combustion phase can mitigate cyclic variation at low energy density while induce knocking combustion at high energy density. The stochastic analysis shows that CI knocking intensity mainly depends on the combustion rate whereas SI knock intensity is more random because of the stochastic end-gas autoignition. Visualized combustion images show that compared to SI combustion, the burning rate of CI combustion is much higher due to the multipoint autoignition. At low energy density, there is no pressure oscillation of CI and SI and the main reason is the low value of peak heat release rate (HRR) regardless of the autoignition. Whereas at high energy density, there are obvious two-stage HRRs for the CI knocking combustion and the high second peak HRR results in the engine knock. Further flame comparison shows that the AI flame speeds in CI and SI modes are similar but much higher than traditional SI flame speed.

    更新日期:2020-01-23
  • Theoretical study on the injected gas override in condensate gas reservoirs
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Weiyao Zhu; Kun Huang; Yan Sun; Jing Xia; Ming Yue

    The override of injected gas in condensate gas reservoirs leads to poor displacement efficiency, and rare research are found to describe this overburden phenomenon occurred in condensate gas reservoirs. This paper presents a mathematical model to describe the override of injected gas, and numerical investigations on a two-dimensional (2D) cross section is used to generate the results. This study examined the effects of different injected gases on the degree of gas override. In addition, this research analyzed the effects of key factors related to reservoir properties and exploitation methods on the gas override. The results demonstrate that the gravity plays a vital role in the formation of overburden phenomenon. The quadrature analysis carried out on a case study exhibits that density difference and perforation position are other two dominant factors in the development of gas overburden.

    更新日期:2020-01-23
  • Effect of different acid-leached USY zeolites on in-situ catalytic upgrading of lignite tar
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Baoyong Wei; Lijun Jin; Dechao Wang; Yankun Xiong; Haoquan Hu; Zongqing Bai
    更新日期:2020-01-23
  • Highly selective Co3O4/silica-alumina catalytic system for deoxygenation of triglyceride-based feedstock
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Vineet Kumar Soni; Suman Dhara; R. Krishnapriya; Ganpat Choudhary; Pragati R. Sharma; Rakesh K. Sharma
    更新日期:2020-01-23
  • Thermal properties of Pennsylvania anthracite
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Matthew C. Weisenberger; Jordan Burgess; Harold H. Schobert; James C. Hower

    Thermal conductivity and thermal diffusivity for a suite of Pennsylvania semi-anthracites through meta-anthracites range from 0.20–0.51 W/m·K to 0.15–0.38 mm2/s, respectively. For both parameters, there is little change in the value between the semi-anthracite and the lowest-rank anthracites (Rmax < 5.30%). The thermal conductivity and diffusivity increase sharply with rank increase in the higher-rank anthracites, with the best correlations being with carbon and hydrogen (both on the dry, ash-free basis). While there was an indication that the maceral composition of the studied anthracites influenced the thermal properties, the number of samples was not sufficient to resolve the role of the maceral composition.

    更新日期:2020-01-23
  • PC-SAFT/UNIQUAC model assesses formation condition of methane hydrate in the presence of imidazolium-based ionic liquid systems
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Marziyeh Zare; Javad Kondori; Sohrab Zendehboudi; Faisal Khan

    One of the major problems in flow assurance, especially in the case of deep subsea pipelines, is the accumulation of gas hydrates that leads to significant issues such as pipe plugging and cracking. Utilization of thermodynamic inhibitors is an effective method to prevent hydrate formation in pipelines. Recently, ionic liquids (ILs) have been recognized as new hydrate inhibitors due to their strong electrostatic charges, which form hydrogen bonds with water molecules. In this work, the capability of the PC-SAFT/UNIQUAC model combined with the van der Waals-Platteeuw theory is assessed for estimation of the methane hydrate dissociation temperatures in the presence of various IL solutions. Five pure-component parameters of PC-SAFT EOS for ILs are fitted by using experimental data of liquid density. Furthermore, vapour-liquid and hydrate equilibria experimental data are employed to adjust the binary interaction parameters of the PC-SAFT EOS (kij) and the UNIQUAC model (uij), respectively. Methane hydrate dissociation temperatures are successfully forecasted by using the proposed model for ten (10) IL systems with different concentrations in which the overall average absolute deviation for temperature (AADT %) of the model is lower than 1.5%. The results clearly demonstrate that the developed thermodynamic model is capable of precisely obtaining the methane hydrate dissociation temperatures in the presence of IL solutions, though, for [EMIM][Cl] solutions with a concentration of more than 30 wt%, the model overestimates the methane hydrate conditions. The proposed thermodynamic modeling strategy can assist to screen suitable IL solutions with an optimal composition for hydrate formation inhibition in terms of technical, economic, and environmental prospectives.

    更新日期:2020-01-23
  • Prediction of nano/micro aluminum particles ignition in oxygen atmosphere
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Xiangrui Zou; Ningfei Wang; Lijuan Liao; Qingzhao Chu; Baolu Shi

    Ignition prediction of aluminum particle is of great significance for a variety of propulsion and power systems to achieve optimal energy release within a limited residence time. In this study a heat transfer model employing temperature dependent coefficients was developed and validated to describe the heat exchange between quiescent/flow gas and aluminum particles from nano- to micro-size, covering the free-molecular to continuum regimes. By coupling heat transfer and aluminum oxidation, a theoretical model has been proposed to accurately capture ignition properties of both aluminum nanoparticle and microparticle (ANP and AMP) burning in hot oxygen atmosphere. Two formulas were obtained to predict the ignition temperature and ignition delay time for nano/micro particles, which show good agreements with experimental results, providing a convenient and accurate method for practical application. A parametric study illustrates that AMP ignition is affected by bulk flow velocity, radiation and oxygen concentration, particularly for AMP over 100 μm in diameter; in contrast, ANP is more sensitive to alumina thickness which generally raises both ignition temperature and ignition delay time. The present study not only deepens the fundamental understanding of aluminum combustion but also provides a guideline for prompting ignition.

    更新日期:2020-01-22
  • Study on the seepage characteristics of coal based on the Kozeny-Carman equation and nuclear magnetic resonance experiment
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Zhen Liu; Wenyu Wang; Weimin Cheng; He Yang; Dawei Zhao

    It is of great significance to quantitatively describe the change in the permeability of the water-injected coal to improve the effect of the coal seam water injection technology. However, the current permeability model often assumes the pores of the porous medium are smooth, which is a large difference from the coarse coal matrix-pore interface. Therefore, a rough capillary bundle is used as the physical model to characterize the coal structure in this paper. Combined with fractal theory, a permeability model including the tortuosity fractal dimension and the specific surface area of the pores is established based on the traditional Kozeny-Carman equation, and the degree of influence of each factor on the permeability was obtained. Then, liquid permeability and structural parameters of the coal samples from the Daliuta Coal Mine and the Qincheng Coal Mine in China were obtained by nuclear magnetic resonance experiments, which verified the accuracy of the model. The research show that the tortuosity fractal dimension has the greatest influence on the theoretical permeability, and the theoretical permeability decreases rapidly when the tortuosity fractal dimension is between 1.05 and 1.20. Increasing the specific surface area of the pores will lead to an increase in the tortuosity fractal dimension and a decrease in the theoretical permeability. Under the different nuclear magnetic resonance experimental conditions, the theoretical permeability of the coal samples is consistent with the change in the liquid permeability and is closer to the measured value compared with the permeability models of Xu and Liu.

    更新日期:2020-01-22
  • Five-stage sequential extraction of Hefeng coal and direct liquefaction performance of the extraction residue
    Fuel (IF 5.128) Pub Date : 2020-01-22
    Ya-ya Ma; Feng-yun Ma; Wen-long Mo; Qiang Wang
    更新日期:2020-01-22
  • Potentials of EGR and lean mixture for improving fuel consumption and reducing the emissions of high-proportion butanol-gasoline engines at light load
    Fuel (IF 5.128) Pub Date : 2020-01-21
    Lifeng Zhao; Wanqiang Qi; Xueyuan Wang; Xiangyang Su

    Biobutanol is a promising alternative fuel, but it is accompanied by a fuel consumption penalty. To mitigate the fuel penalty, air dilution was investigated in a turbocharged gasoline direct injection engine fueled with isobutanol-gasoline (B73). To overcome issues of NOx emissions during air dilution operation, exhaust gas recirculation (EGR) and the combination of EGR and air dilution (EGR-Air) were investigated to reduce NOx emissions and enhance engine performance. The effects of these applications on particulate emissions (PM) were also assessed. Compared to EGR, there was more pronounced improvement in brake thermal efficiency (BTE) for butanol-gasoline engine under EGR-Air. The combustion stability under EGR-Air was acceptable but slightly decreased relative to that under EGR. Lower exhaust gas temperature was observed under EGR-Air with respective to EGR. EGR-Air exhibited similar effective inhibition of NOx emissions, as with EGR, which was more pronounced in reducing NOx emissions at high EGR rate, while EGR-Air reduced NOx by up to 90%. CO emissions were clearly reduced under EGR-Air conditions, which realized a better balance between BTE and NOx emissions with very low NOx concentrations. For a butanol-gasoline engine, the PM emissions under EGR-Air were further lowered compared to EGR, which showed a bimodal size distribution, and the particle sizes corresponding to the particle number peak was in the range of 10–30 nm. The observed particle diameters under EGR-Air were smaller than that with and without EGR.

    更新日期:2020-01-22
  • Improving coal permeability using microwave heating technology—A review
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Jinxin Huang; Guang Xu; Yunpei Liang; Guozhong Hu; Ping Chang

    Microwave heating is a promising non-aqueous technology in coal seam enhancement. Recently, it has been considered as an alternative technology to hydraulic fracturing and Enhanced Coal Bed Methane recovery, which may be inapplicable due to environmental and geological restrictions. In this paper, a critical review of microwave heating (MH) applications in coal permeability enhancement is presented. The mechanisms of both microwave heating and microwave-induced permeability enhancement are explained. Most of the experimental studies and numerical simulations in the related area are reviewed. The influencing factors for microwave heating/fracturing effect are then discussed in detail. After discussing the challenges in applying microwave on-site, potential field applications were suggested. As no field application is reported till now, further studies, especially experiments in the field-scale are in badly demand to test its technical and economic feasibility.

    更新日期:2020-01-21
  • Impact of alkylbenzenes in formulated surrogate fuel on characteristics of compression ignition engine
    Fuel (IF 5.128) Pub Date : 2020-01-20
    Bandar Awadh Almohammadi; Paramvir Singh; Saurabh Sharma; Sudarshan Kumar; Bhupendra Khandelwal

    Aromatic contents in the fuel significantly affect the exhaust pollutant emissions and performance of compression ignition engines. Alkylbenzenes are dominating aromatics in diesel fuel and have attractive properties as the component of diesel fuel. Therefore, different alkylbenzenes were experimentally investigated using single-cylinder direct-injection compression ignition engine at two different loads and constant speed. Different Alkylbenzenes were blended with low aromatic diesel fuel in three percentages i.e. 5, 10 and 15% by mass. The results showed a slight improvement in brake specific fuel consumption and brake thermal efficiency with high calorific value alkylbenzenes. Moreover, carbon monoxide, nitrogen oxides, particulate matter and smoke emissions were significantly influenced with the aromatic content and their types. The effect on performance and emissions differed from one alkylbenzene to another due to the variation in physicochemical properties of aromatics such as density, hydrogen-to-carbon ratio, etc. Ethylbenzene shows better results in terms of performance and lower pollutant emissions.

    更新日期:2020-01-21
  • Carbon dioxide sealing-based inhibition of coal spontaneous combustion: A temperature-sensitive micro-encapsulated fire-retardant foamed gel
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Di Xue; Xiangming Hu; Weimin Cheng; Mingyue Wu; Zhiang Shao; Yongsheng Li; Yanyun Zhao; Kun Zhang
    更新日期:2020-01-21
  • Investigation of injection strategy for a diesel engine with directly injected methanol and pilot diesel at medium load
    Fuel (IF 5.128) Pub Date : 2020-01-17
    Zhiyong Li; Yang Wang; Heming Geng; Xudong Zhen; Minjiang Liu; Shuai Xu; Changming Li

    A 3D simulation model is conducted to investigate the injection strategy for a diesel engine with directly injected methanol and pilot diesel at medium load. Three injection strategies are proposed: D/M and M/D modes are where methanol injection occurs after and before diesel injection respectively, and M/D/M mode is where methanol is injected once before and once after diesel injection. Optimal settings for each strategy are obtained and compared, yielding the following results: in D/M mode, earlier fuel injection contributes to lower equivalent indicated specific fuel consumption (EISFC) but higher ringing intensity (RI). Moreover, too small dwell leads to misfire or knocking, and too large dwell is detrimental to fuel economy. Secondly, in M/D mode, methanol injection should not be too delayed to avoid knocking and dwell should not be too small to prevent misfire. Thirdly, in M/D/M mode, a larger methanol ratio in the first injection achieves lower EISFC, soot, total unburned hydrocarbon (THC) and carbon monoxide (CO) emissions, but higher nitrogen oxides (NOx) emission. Lastly, M/D mode is found to produce the best results, followed by M/D/M mode and then D/M mode.

    更新日期:2020-01-21
  • Investigation of flame and burner plate interaction during the heat flux method used for laminar burning velocity measurement
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Zhihua Wang; Xinlu Han; Yong He; Shixing Wang; Ran Ji; Yanqun Zhu; Kefa Cen

    The heat flux method has been used widely for measuring the laminar burning velocity SL. However, compared with ideal SL definition of freely-propagating, stretch-less and adiabatic, the data obtained by the heat flux method is usually not perfectly freely-propagating due to the interaction between the flame and burner plate, which can affect the accuracy of the measurement. Though this issue has caught attention by some researchers, it hasn’t been evaluated extensively by experiments so far. To fill this gap, this study specially investigated four experimentally obtained factors: the measured burning velocity, the measurement sensitivity, the stand-off distance and the flame thickness. The experiments were carried out with methane + air flames at 1 atm and 298 K, equivalence ratio 0.7–1.5. By changing the burner plate temperature, the extent of flame and burner plate interaction can be well controlled. After series of assumption, deduction, and comparison with experiment results, a half-quantitative equation was proposed, and the burning velocity of stretch-less adiabatic freely-propagating flame was extrapolated from the non-freely propagating experiment results, which shows good agreement with literature data and simulation results. Besides, the uncertainty caused by not considering the flame and burner plate interaction was also evaluated.

    更新日期:2020-01-21
  • Influence of asphaltene on wax deposition: Deposition inhibition and sloughing
    Fuel (IF 5.128) Pub Date : 2020-01-21
    Huiyuan Li; Jinjun Zhang; Qinggong Xu; Chengyu Hou; Yadong Sun; Yu Zhuang; Shanpeng Han; Changchun Wu

    Asphaltenes are the heaviest and most polar constituents of crude oils. The influences of asphaltene on wax deposition were investigated with model oils utilizing a Taylor-Couette device. The composition and rheological properties of the deposits and the chemical properties of the asphaltenes entrained in the deposits were analyzed. Three main observations were obtained: (a) Wax deposition rate decreases in the presence of asphaltenes while the wax content of the deposit increases. The carbon number distribution of the deposit and the critical carbon number of the deposition process were also observed to vary due to the presence of asphaltenes. (b) The asphaltene content of the deposit constantly increases as time elapses and eventually reaches several times higher than that of the original oil. The asphaltenes entrained in the deposits are of higher polarity and molecular weight than the asphaltenes originally present in the oil. (c) When the asphaltene content of the oil is above 0.2 wt%, deposits slough off frequently as asphaltenes alter the microstructure of the deposit and lower its yield strength.

    更新日期:2020-01-21
  • Numerical optimization of a diesel combustion system to reduce soot mass and particle number density
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Pavan Prakash Duvvuri; Rajesh Kumar Shrivastava; Sheshadri Sreedhara

    In view of the recent emission legislations imposing a limit on the soot particle number density, a numerical optimization has been presented for a constant speed heavy-duty diesel engine to reduce soot particle number density while ensuring no penalty on NOx emissions. Closed cycle combustion simulations have been performed at three loads with the sectional soot model coupled to gas phase kinetics. The combustion model has been tuned at each load to ensure a good agreement for in-cylinder pressure, heat release rate and exhaust emissions. The validated combustion model has been used to study the effect of various parameters like intake swirl, start of injection, number of nozzle holes, spray angle and piston bowl shapes. Combustion simulations have been performed for every case of a full factorial design of experiments with 486 cases. Change in plume dynamics due to each parameter has been discussed in detail with the help of in-cylinder soot contours. A reentrant bowl with a higher swirl, lower number of nozzle holes and a deeper spray angle has been found to be the most promising option as it reduces the exhaust soot mass, number density with no penalty on NOx and specific fuel consumption.

    更新日期:2020-01-21
  • Combustion behaviours and emission characteristics of a retrofitted NG/gasoline duel-fuel SI engine with various proportions of NG-gasoline blends
    Fuel (IF 5.128) Pub Date : 2020-01-17
    Yuanli Xu; Yuxin Zhang; Jian Gong; Shijian Su; Zengna Wei

    A baseline gasoline engine was retrofitted into a natural gas (NG)/gasoline duel-fuel engine through increasing a NG injection system at its intake manifold. The combustion behaviours and emission characteristics of the engine with different proportions of NG-gasoline blends were investigated. Numerical simulation and experiments verification were performed on a 4-cylinder SI engine. The results show that the combustion behaviours and emission characteristics of natural gas/gasoline dual fuel engine are between gasoline and natural gas. The maximum in-cylinder pressure (MCP), the maximum heat release rate (MHRR) and maximum pressure rise rate (MPRR) decrease with the increase of NG ratio and combustion phases (CA10 and CA50) are retarded, this implies that the adding natural gas to the gasoline can effectively improve the knocking resistance of the engine, which allows to improve the thermal efficiency by increasing compression ratio. The maximum combustion temperature (MCT) and the total overall equivalence ratio increases with the increase of NG ratio, leading to an increase in NO and soot emissions but their increasing proportion of NO and soot emissions at 50% of NG ratio (by energy) is respectively less than 8.7% and 17.3 with respect to the pure gasoline mode, but at the same time, there is an increase in indicated thermal efficiency (ITE) and a decrease in CO, CO2 and HC, this implies that trading off thermal efficiency and NOX emissions by operating the engine with 50% of NG and 50% of gasoline (by energy) without causing further cost and complexity.

    更新日期:2020-01-21
  • Removal of elemental mercury from flue gas by recyclable CuCl2 modified magnetospheres from fly ash: Part 5. Industrial scale studies at a 50 MWth coal-fired power plant
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Yuming Zhou; Jianping Yang; Liangchen Dong; Tian Gao; Zenghua Li; Yushan Ji; Yongchun Zhao; Siwei Pan; Junying Zhang; Chuguang Zheng

    The mercury removal performance of a low-cost recyclable CuCl2 modified magnetospheres (Cu-MF) was investigated at a 50 MWth coal-fired power plant. An increase in the Cu-MF injection rate facilitated the mercury removal and recovery process. With the combination of the existing pollutant control devices and the Cu-MF injection, an overall mercury removal efficiency of 99.3% could be achieved. Under optimal conditions, the mercury emitted from the stack was reduced to 0.10 μg/m3. Most of the mercury in the flue gas migrated to the fly ash with the spent Cu-MF. Subsequently, through magnetic separation, 67.4% of the input mercury could be recovered. The comparison of experimental results showed that Cu-MF was more effective than fly ash in removing and recovering mercury from the flue gas. With the injection of Cu-MF, HgCl2 was formed on the magnetospheres and was identified by the mercury-temperature-programmed decomposition (Hg-TPD) experiments. The magnetospheres with the lowest particle size showed the highest mercury removal capacity. This work is expected to provide valuable guidance for optimising the mercury removal technology in large scale commercial applications in future.

    更新日期:2020-01-21
  • Novel amphiphilic gemini ionic liquids based on consumed polyethylene terephthalate as demulsifiers for Arabian heavy crude oil
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Mahmood M.S. Abdullah; Hamad A. Al-Lohedan

    This work aims to use consumed polyethylene terephthalate (PET) to prepare new amphiphilic gemini ionic liquids (GILs). PET was converted into bis(2-hydroxyethylene) terephthalate (BHET). The produced BHET was reacted with thionyl chloride to produce the corresponding dialkyl halide, bis(2-chloroethyl) terephthalate (BCET). N,N-bis-hexaoxyethlene octadecylamine (HEOD) and N,N-bis-hexaoxyethlene dodecylamine (DOAD) were quaternized with BCET to produce the corresponding GILs: HEOD-IL and DOAD-IL, respectively. The chemical structures were confirmed by Fourier-transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance spectroscopy (1H NMR), and 13C nuclear magnetic resonance spectroscopy (13C NMR). The surface tension, interfacial tension, and solubility were also investigated. In addition, the ability of the prepared amphiphilic GILs to demulsify Arabian heavy crude oil was evaluated. The results showed that their efficiency increased when the water content in the water-in-oil emulsion increased.

    更新日期:2020-01-21
  • Reactivation mode investigation of spent CaO-based sorbent subjected to CO2 looping cycles or sulfation
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Jian Sun; Wenyu Wang; Yuandong Yang; Shan Cheng; Yafei Guo; Chuanwen Zhao; Wenqiang Liu; Ping Lu
    更新日期:2020-01-21
  • Effects of physical structure of high heating-rate chars on combustion characteristics
    Fuel (IF 5.128) Pub Date : 2020-01-20
    Siqi Liu; Yanqing Niu; Liping Wen; Yaqian Kang; Denghui Wang; Shi'en Hui

    The combustion performance of high heating-rate chars is observably affected by the evolution of its physical structure during devolatilization. An effort has been devoted to building understandable relationships between the heating rates of different rank coals, char structure and subsequently detailed combustion characteristics. In this work, the physical structure parameters (internal surface area, porosity, and swelling ratio) of bituminous coals and lignites are qualitatively summarized as a function of heating rates (>104 K/s). Meanwhile, the physical structure effects on char combustion characteristics are investigated separately by using the self-developed kinetics model, where the transient char properties, ash distribution (ash film, ash dilution, and ash vaporization) and char combustion performances are taken into account. The relative importance of the three structure parameters on char burnout is also performed. The internal surface area of high heating-rate chars exerts positive effects on combustion with higher burning temperature and shorter burnout time, whereas the swelling ratio and porosity exert complex effects. The combustion rate initially increases then goes down with char conversion, owing to the integrated effects of formation and destruction of internal surface area. The importance of physical structure parameters on char combustion follows the order: internal surface area > swelling ratio > porosity. These results provide in-depth insight into the effects of physical structure during char combustion and suggest higher heating rates are favorable in industrial boiler applications.

    更新日期:2020-01-21
  • Effect of molybdenum promoter on performance of high silica MoO3/B-ZSM-5 nanocatalyst in biodiesel production
    Fuel (IF 5.128) Pub Date : 2020-01-20
    Saeed Mohebbi; Mohammad Rostamizadeh; Davood Kahforoushan

    Biodiesel is a clean and renewable energy. In this study, biodiesel was produced through the esterification of free fatty acid (FFA) with methanol over the high silica B-ZSM-5 nanocatalyst. The parent nanocatalyst was synthesized by hydrothermal technique and the promoter was introduced by a multi-step wet impregnation method. XRD, FT-IR, BET, FE-SEM, EDX, TEM, and NH3-TPD analyzes characterized the textural and acidity properties of the nanocatalysts. The promoter was dispersed uniformly without significant framework destruction. The impregnation of molybdenum decreased the strength of the acid sites and increased the concentration of the acid sites. The morphology of the nanocatalyst was spherical including the high crystallinity, high surface area, and mesoporous structure. The 25% MoO3/B-ZSM-5 nanocatalyst showed the best performance in the esterification of FFA. The optimum operating conditions were 6 h reaction time, temperature of 160 °C, 3%wt catalyst concentration, and methanol/FFA molar ratio of 20:1, which resulted in the highest conversion of FFA (98%). The impregnated nanocatalyst had high stability and reusability through the sequence runs including only 5% conversion drop after six runs. The results confirmed the high potential of the developed nanocatalyst for industrial applications.

    更新日期:2020-01-21
  • Lean blowout detection for bluff-body stabilized flame
    Fuel (IF 5.128) Pub Date : 2020-01-20
    Liuyong Chang; Zhang Cao; Bo Fu; Yuzhen Lin; Lijun Xu

    The present work proposed an index to extend the previous lean blowout detection method to bluff-body stabilized flame at the condition of low Reynolds number. Dynamic characteristics near lean blowout of low Reynolds number bluff-body flame are not exactly same with that of high Reynolds number bluff-body flame. Thus lean blowout detection index requires modification for low Reynolds number bluff-body flame. The flame images show that, for a fixed fuel flow, increase of air flow to a certain value can cause flame liftoff-reattachment events, and further increase of air flow can lead to complete liftoff and even lean blowout. Temporal and spectral analyses of the ion current and CH* signals exhibit that both standard deviation and low frequency energy within 0.2–10 Hz of each signal first increase due to flame liftoff-reattachment and then decrease due to complete flame liftoff with the increase of air flow. This leads to that the lean blowout detection indexes including the normalized root mean square (NRMS), normalized cumulative duration (θ) and fraction of the fast Fourier transform (FFT) power at low-frequencies (FFT%[0-f1Hz]) first increase and then decrease with the increase of air flow. As a result, the flame at the liftoff state may be wrongly classified as stable state. To avoid this, the histogram distributions of two signals were investigated. The number of small value sample points of each signal increases with increase of air flow, indicating that the percentage of small value sample points can be used to detect lean blowout. The mean value of each signal at the liftoff-reattachment state is used as the threshold value to classify small value sample points. For either the ion current signal or CH* signal, percentage of sample points below the corresponding threshold value (P

    更新日期:2020-01-21
  • Characterization of physico-chemical properties of biodiesel components using smart data mining approaches
    Fuel (IF 5.128) Pub Date : 2020-01-17
    Danial Abooali; Reza Soleimani; Saeed Gholamreza-Ravi

    Biodiesels are the most probable future alternatives for petroleum fuels due to their easy accessibility and extraction, comfortable transportation and storage and lower environmental pollutions. Biodiesels have wide range of molecular structures including various long chain fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs) with different thermos-physical properties. Therefore, reliable methods estimating the ester properties seems necessary to choose the appropriate one for a special diesel engine. In the present study, the effort was developing a set of novel and robust methods for estimation of four important properties of common long chain fatty acid methyl and ethyl esters including density, speed of sound, isentropic and isothermal compressibility, directly from a number of basic effective variables (i.e. temperature, pressure, molecular weight and normal melting point). Stochastic gradient boosting (SGB) and genetic programming (GP) as innovative and powerful mathematical approaches in this area were applied and implemented on large datasets including 2117, 1048, 483 and 310 samples for density, speed of sound, isentropic and isothermal compressibility, respectively. Statistical assessments revealed high applicability and accuracy of the new developed models (R2 > 0.99 and AARD < 1.7%) and the SGB models yield more accurate and confident predictions.

    更新日期:2020-01-21
  • Systematic exploration of the interactions between Fe-doped kaolinite and coal based on DFT calculations
    Fuel (IF 5.128) Pub Date : 2020-01-18
    Jun Chen; Fanfei Min; Lingyun Liu; Chuanchuan Cai
    更新日期:2020-01-21
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