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Table of Content
28 February 2020, Volume 28 Issue 2
    Fluid Dynamics and Transport Phenomena
    Hydrodynamic and heat transfer properties of magnetic fluid in porous medium considering nanoparticle shapes and magnetic field-dependent viscosity
    Mohsen Izadi, Masoud Javanahram, Seyed Mohsen Hashem Zadeh, Dengwei Jing
    2020, 28(2):  329-339.  doi:10.1016/j.cjche.2019.04.024
    Abstract ( )   PDF (3075KB) ( )  
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    The purpose of this paper is to study the characteristics of the combined convection heat transfer and a micropolar nanofluid flow passing through an impermeable stretching sheet in a porous medium. The nanofluid flow field is affected by a magnetic field perpendicular to the sheet. The dynamic viscosity of the micropolar nanofluid changes under the influence of the magnetic field. The continuity, linear momentum, angular momentum, and energy equations are first simplified using the order of magnitude technique that, along with the applied boundary conditions and the definition of the appropriate parameters, are transferred to the similarity space using the similarity analysis. Then the resulting equations are solved using the Runge-Kutta method. The distinction of the macroscale and microscale flow fields and temperature fields resulting from different nanoparticle shapes was clarified. Increasing the Hartmann number, the vortex viscosity parameter, the magnetic parameter, the nanoparticle volume fraction, and the permeability parameter of the porous media increased the surface friction on the sheet. Increasing the vortex viscosity parameter, the magnetic parameter, and the volume fraction of the nanoparticles increases the Nusselt number.
    Erosion corrosion control of 6061 aluminum alloy in multi-phase jet impingement conditions with eco-friendly green inhibitor
    M. Lavanya, V. Ramachandra Murthy, Padmalatha Rao
    2020, 28(2):  340-347.  doi:10.1016/j.cjche.2019.07.016
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    Erosion corrosion performance of 6061 aluminum alloy in simulated sea water slurry was investigated under multi-phase jet impingement conditions. The main objective of the work is to study erosion-corrosion of a material with engineering application and mitigate it using eco- friendly green inhibitor. Experiments were performed with the sand concentration of 0.3% and 0.3 μm size. The effect of temperature and flow rate on the performance of inhibitor was explored. Electrochemical methods were adopted for erosion-corrosion measurements. Experiments revealed that starch could mitigate erosion-corrosion with a maximum reduction efficiency of 58% at temperature of 303 K and flow rate of 4 L·min-1. Inhibition efficiency decreased with increase in flowrate and temperature. EIS spectrum demonstrated that the corrosion process in the presence on inhibitor was both charge transfer and mass transfer controlled. A key role of hydrodynamics in the performance of corrosion inhibitor was confirmed by the present study.
    CFD modeling of immiscible liquids turbulent dispersion in Kenics static mixers: Focusing on droplet behavior
    M. M. Haddadi, S. H. Hosseini, D. Rashtchian, G. Ahmadi
    2020, 28(2):  348-361.  doi:10.1016/j.cjche.2019.07.020
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    The present study is concerned with the computational fluid dynamics (CFD) simulation of turbulent dispersion of immiscible liquids, namely, water-silicone oil and water-benzene through Kenics static mixers using the Eulerian-Eulerian and Eulerian-Lagrangian approaches of the ANSYS Fluent 16.0 software. To study the droplet size distribution (DSD), the Eulerian formulation incorporating a population balance model (PBM) was employed. For the Eulerian-Lagrangian approach, a discrete phase model (DPM) in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution (RTD) of droplets. In both approaches, a shear stress transport (SST) k-ω turbulence model was used. For validation purposes, the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor, Sauter mean diameter and the mean residence time. The reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean diameter. In addition, the influence of important geometrical and operational parameters, including the number of mixing elements and Weber number, was studied. It was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.
    Effects of different nozzle materials on atomization results via CFD simulation
    Xiangyu Li, Jianjun Du, Licheng Wang, Jiangli Fan, Xiaojun Peng
    2020, 28(2):  362-368.  doi:10.1016/j.cjche.2019.09.008
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    Spray drying, as a crucial operation in industrial production, converts solution to fine particle. The spray moiety directly affects the final particle morphology, size and distribution. Compared with the experimental method, computational fluid dynamics (CFD) modeling is a powerful and convenient tool for simulating the spray process. Based on the verified CFD model, different materials of atomizer were simulated to investigate the effect on droplet size and distribution in this work. The modeling result proved that the droplet size and distribution were influenced by the resistance coefficient of materials, wherein the Reynolds number could change the effect of roughness along with the change of mass flow rate on spray process. The results in this work have implication for controlling droplet size through developing new spray nozzle with different materials or surface coating.
    Hydrate formation in oil-water systems: Investigations of the influences of water cut and anti-agglomerant
    Guangchun Song, Yuxing Li, Wuchang Wang, Kai Jiang, Zhengzhuo Shi, Shupeng Yao
    2020, 28(2):  369-377.  doi:10.1016/j.cjche.2019.07.024
    Abstract ( )   PDF (3056KB) ( )  
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    To investigate the characteristics of hydrate formation in oil-water systems, a high-pressure cell equipped with visual windows was used where a series of hydrate formation experiments were performed from natural gas + diesel oil + water systems at different water cuts and anti-agglomerant concentrations. According to the temperature and pressure profiles in test experiments, the processes of hydrate formation under two kinds of experimental procedures were analyzed first. Then, based on the experimental phenomena observed through the visual windows, the influences of water cut and anti-agglomerant on the places of hydrate formation and distribution, hydrate morphologies and hydrate morphological evolvements were investigated. Hydrate agglomeration, hydrate deposition and hydrate film growth on the wall were observed in experiments. Furthermore, three different mechanisms for hydrate film growth on the wall were identified. In addition, the influences of water cut and anti-agglomerant on the induction time of hydrate formation were also studied.
    Concept of a swirling diffuser in batch blending tanks
    Wojciech Artichowicz, Jerzy M. Sawicki
    2020, 28(2):  378-382.  doi:10.1016/j.cjche.2019.09.009
    Abstract ( )   PDF (1135KB) ( )  
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    The mixing of two or more components belongs to the category of the most common unit operations, both in technology and in nature. One particular version is homogenization (blending), the effectivity of which is strongly related to the blending time. Among many differentiated individual solutions of mixing systems used in blenders, one should distinguish the class of agitators with diffusers. An analysis of the character of the velocity field during a blending chamber operation leads to the conclusion that it would be of avail to outfit a straight diffuser with different setups of elbows. In consequence, the vertical direction of the inflowing fluid stream would be changed into the horizontal direction of the outflowing stream, which should intensify the blending process. The concept has been verified experimentally, making use of the tracer methodology. The obtained results confirmed the theoretical conclusion that the blending time for the swirling-diffuser was shorter than for the classical straight one.
    A comprehensive study of two-phase flow and heat transfer of water/Ag nanofluid in an elliptical curved minichannel
    Sajad Mir, Omid Ali Akbari, Davood Toghraie, Ghanbarali Sheikhzadeh, Ali Marzban, Saeid Mir, Pouyan Talebizadehsardari
    2020, 28(2):  383-402.  doi:10.1016/j.cjche.2019.07.007
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    In this research, laminar flow and heat transfer of two-phase water/Ag nanofluid with 0-6% volume fraction of nanoparticles at Re=150-700 in a curved geometry are simulated using finite volume method. Studied geometry is an elliptical curved minichannel with curvature angle of 180°. Forced and natural flow of two-phase nanofluid is simulated at Gr=15000, 35000 and 75000. For estimation of nanofluid flow behavior, two-phase mixture method is used. The second-order discretization and SIMPLEC algorithm are used for solving governing equations. The results indicate that the increase of volume fraction of nanoparticles leads to the enhancement of the temperature of central line of flow. The increase of Grashof number (Gr~75000) has a great effect on reduction of dimensionless temperature in central line of flow. Creation of thermal boundary layer at Re=500 and after the angle of 30° becomes significant. In low Grashof numbers (Gr~15000), due to the great effects of temperature gradients close to wall, these regions have significant entropy generation.
    A novel combined baffle-cavity micro-combustor configuration for Micro-Thermo-Photo-Voltaic applications
    E. Amani, A. Daneshgar, A. Hemmatzade
    2020, 28(2):  403-413.  doi:10.1016/j.cjche.2019.05.002
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    The major issues of Micro-Thermo-Photo-Voltaic (MTPV) micro-combustors are flame instabilities, which narrow the operational range, and non-uniform wall temperature, which lowers the overall efficiency. The purpose of the present research is to propose a novel micro-combustor with combined baffle and cavity configuration to address these issues. For this aim, a numerical modeling approach is validated and used. The performance of the improved combustor is compared with another recent baffle-bluff configuration. It is shown that the novel design improves the average wall temperature by 36.4 K and mitigates its standard deviation by 13.4 K. Moreover, using the optimal baffle thickness, these enhancements can be augmented by 4% raise of average wall temperature, 62% increase of temperature uniformity, and 20% reduction in overall emission. The baffle length of 0.6 times the combustor length and thickness of 0.0625 times the baffle spacing result in the optimal operation due to the flame lift-off in the upstream direction. According to the sensitivity analysis, the most effective geometrical parameters are the baffle length and thickness. It is expected that using this novel micro-combustor with optimized design parameters improves the overall efficiency of MTPV systems.
    Separation Science and Engineering
    Effective adsorptive denitrogenation from model fuels over yttrium ionexchanged Y zeolite
    Fuping Tian, Xin Sun, Xinyi Liu, Hongluan Zhang, Jiaxu Liu, Hongchen Guo, Yifu Zhang, Changgong Meng
    2020, 28(2):  414-419.  doi:10.1016/j.cjche.2019.05.014
    Abstract ( )   PDF (791KB) ( )  
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    The adsorption removal of indole and quinoline in octane with and without toluene over zeolites NaY and Yttrium Ion-exchanged Y (YY) using batch adsorption experiments was studied at 25 ℃ and 0.1 MPa. YY was prepared by treating NaY with Y(NO3)3 solution twice via liquid ion-exchange method. NaY and YY were both characterized by XRD, SEM, N2 adsorption, XRF, NH3-TPD, and pyridine-FTIR techniques. Adsorption isotherms of indole, quinoline and toluene in octane were conducted at 25.0 ℃ to explain the influence of toluene on nitrogen removal over NaY and YY. The partial destruct of the crystalline structure of NaY was observed after the introduction of yttrium ion, which led to an evident decline in BET surface area and pore volume of YY. Strong Brönsted acidity and medium Lewis acidity were introduced by yttrium ion-exchange. Though the specific surface area and pore volume of YY were much lower than those of NaY, YY exhibited equivalent adsorption capacities for indole and quinoline as NaY in model fuels without toluene. In the presence of 20 vol% toluene, however, YY exhibited much higher adsorption capacities for indole and quinoline than NaY, especially in the case of quinoline. The improved toluene-tolerant of YY was ascribed to the strong acid-base interaction between YY and quinoline and the decreased adsorption strength between YY and toluene.
    Potential use of nanofiltration like-forward osmosis membranes for copper ion removal
    Wan Nur Ain Shuhada Abdullah, Sirinan Tiandee, Woeijye Lau, Farhana Aziz, Ahmad Fauzi Ismail
    2020, 28(2):  420-428.  doi:10.1016/j.cjche.2019.05.016
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    The discharge of industrial effluent containing heavy metal ions would cause water pollution if such effluent is not properly treated. In this work, the performance of emerging nanofiltration (NF) like-forward osmosis (FO) membrane was evaluated for its efficiency to remove copper ion from water. Conventionally, copper ion is removed from aqueous solution via adsorption and/or ion-exchange method. The engineered osmosis method as proposed in this work considered four commercial NF membranes (i.e., NF90, DK, NDX and PFO) where their separation performances were accessed using synthetic water sample containing 100 mg·L-1 copper ion under FO and pressure retarded osmosis (PRO) orientation. The findings indicated that all membranes could achieve almost complete removal of copper regardless of membrane orientation without applying external driving force. The high removal rates were in good agreement with the outcomes of the membranes tested under pressuredriven mode at 1MPa. The use of appropriate salts as draw solutes enabled the NF membranes to be employed in engineered osmosis process, achieving a relatively low reverse solute flux. The findings showed that the best performing membrane is PFO membrane in which it achieved >99.4% copper rejection with very minimum reverse solute flux of < 1g·m-2·h-1.
    Insights into membrane fouling implicated by physical adsorption of soluble microbial products onto D3520 resin
    Ruyi Cao, Juanjuan Zhou, Weiwei Chen
    2020, 28(2):  429-439.  doi:10.1016/j.cjche.2019.06.005
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    Membrane fouling is a major problem in membrane bioreactors (MBRs). In this study, membrane fouling caused by membrane rejection and adsorption was study. Filtration tests indicated that membrane rejected SMP, causing membrane pore blockage and then forming a gel layer. Batch adsorption experiments showed that adsorption of SMP onto PVDF membrane was a spontaneous physical adsorption process.
    Meanwhile, the absolute value ΔG of adsorption of SMP onto D3520 was higher than that of adsorption of SMP onto PVDF membrane, so SMP preferentially adsorbed onto D3520 rather than PVDF membrane. Thus, the effect of ARs on reducing the SMP concentration was investigated. It was found that, 6 g of D3520 was suitable for adsorption of SMP. This physical adsorption involved external film diffusion, intra-particle diffusion, and surface adsorption. The Redlich-Peterson isotherm model performed best in terms of describing this equilibrium data. The mechanism of membrane fouling mitigation was verified by MBR simulation system. A case study of AR-MBR system was conducted. The results showed that addition of D3520 can effectively alleviate the development of membrane fouling.
    Lysozyme adsorption to cation exchanger derivatized by sequential modification of poly(ethylenimine)-Sepharose with succinic anhydride and ethanolamine: Effect of pH and ionic strength
    Yangyang Zhao, Xianxiu Li, Linling Yu, Xiaoyan Dong, Yan Sun
    2020, 28(2):  440-444.  doi:10.1016/j.cjche.2019.07.003
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    In our previous work, a series of polyethylenimine (PEI)-derived cation exchangers were synthesized using PEIgrafted resin FF-PEI-L740 (ionic capacity, 740 mmol·L-1) as the basic resin to study lysozyme adsorption and chromatographic behavior. It was found that the resin with an ionic capacity of 630 mmol·L-1 (FF-PEI-CR630) possessed high adsorption performance towards lysozyme at 0-100 mmol·L-1 NaCl. Therefore, in this work, FF-PEI-CR630 was selected to study the influences of pH and ionic strength (IS) on protein adsorption and chromatographic behavior towards lysozyme. The increase of lysozyme adsorption capacity in the pH range of 6 to 10 was observed. However, the uptake rate decreased in the pH range of 6 to 8 and then remained essentially unchanged from pH 8 to pH 10. Increasing IS led to decreased protein adsorption capacity and increased uptake rate in different pH ranges. Besides, FF-PEI-CR630 maintained dynamic binding capacity as high as over 150 mg·ml-1 at pH 8-10 without NaCl. The research has thus provided insight into the selection of proper pH and IS conditions for protein purification by using FF-PEI-CR630.
    Direct extraction of Mo(VI) from sulfate solution by synergistic extractants in the rotation column
    Benyamin Shakib, Meisam Torab-Mostaedi, Mohammad Outokesh, Mehdi Asadollahzadeh
    2020, 28(2):  445-455.  doi:10.1016/j.cjche.2019.11.011
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    Direct extraction of molybdenum from sulfate solution with synergistic extractants (mixture of D2EHPA and TBP) was studied in the rotation column. The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments. The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase. In the continuous experiments, the effect of different operating parameters such as speed of agitation, inlet solvent flow rate and inlet aqueous flow rate on the holdup, mean drop size, drop size distribution, slip and characteristic velocities and extraction percentage were examined. Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column. Furthermore, these correlations were compared with the experimental data. According to the results, the direct extraction of Mo (VI) from aqueous solution and sulfuric media with extraction efficiency of 90.4% was obtained at higher rotor speed (240 r·min-1 rpm) in this column.
    Process Systems Engineering and Process Safety
    Optimal synthesis of multi-plant heat exchanger networks considering both direct and indirect methods
    Chenglin Chang, Yufei Wang, Xiao Feng
    2020, 28(2):  456-465.  doi:10.1016/j.cjche.2019.03.014
    Abstract ( )   PDF (4001KB) ( )  
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    Heat exchanger networks (HENs) in separated plants can be simultaneously synthesized through process streams directly or intermediate fluids indirectly. However, the direct and indirect methods are studied separately in most existing researches. As the result, conventional designs are probably suboptimal, because optimal solutions may call for hybrid approach wherein direct and indirect integration methods are used synchronously. To circumvent this drawback aforementioned, we propose in this research a novel methodology to synthesize multi-plant HENs considering both direct and indirect approaches. The methodology employs a novel superstructure covering most potential topologies for both interplant and intra-plant heat integration. We also take into account multiple kinds of intermediate fluids for indirect integration and this has not been fully addressed in previous research. A mixed-integer nonlinear programming (MINLP) is formulated to optimize multi-plant HENs involving indirect and direct methods. One example from existing literature and one industrial problem are solved to demonstrate the methodology's capability.
    Direct image-based fractal characterization of micromorphology of calcium carbonate fouling crystals
    Xiaokai Xing, Zhonghua Zhao, Jianhang Wu
    2020, 28(2):  466-476.  doi:10.1016/j.cjche.2019.08.009
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    Researches on macroscopic fouling behavior and micromorphology are usually conducted separately. In this paper, the relationship between the macroscopic fouling behavior and micromorphology on different materials is established. A direct fractal-characterization approach based on the micrographs of calcium carbonate fouling crystals is presented. The box-counting method is used to characterize the fouling crystals. For fractal measurements, t-distribution tests of linear regression hypothesis are performed at the significance level of 0.01. If all listed absolute t-statistics with the minimum of 164 are higher than the corresponding t value, the fouling crystals are determined as fractal, with a confidence level of 99%. The fractal dimensions obtained from the micrographs of different visual fields of a specimen are demonstrated to be almost identical, with maximum and minimum relative values of 4.42% and 0.75%, respectively, and standard deviations ranging from 0.0062 to 0.0266. The irregularity of the crystal morphology indicates larger fractal dimensions. Comparison and analysis of the relationship between macroscopic fouling behavior and micromorphology show that the larger fractal dimension of crystal morphology suggests a small amount of surface fouling. Thus, the reasons for the differences in the macroscopic fouling behaviors of different materials are revealed geometrically.
    Chemical Engineering Thermodynamics
    Experimental and computational chemical studies on the cationic furanylnicotinamidines as novel corrosion inhibitors in aqueous solutions
    Abdelaziz S. Fouda, Mohamed A. Ismail, Rabab M. Abou-shahba, Walaa A. Husien, Esraa S. EL-Habab, Ashraf S. Abousalem
    2020, 28(2):  477-491.  doi:10.1016/j.cjche.2019.04.017
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    The corrosion inhibition action of three newly synthesized furanylnicotinamidine derivatives namely: 6-[5-{4 (dimethylamino)phenyl}furan-2-yl]nicotinamidine (MA-1256), 6-[5-(4-chlorophenyl)furan-2-yl] nicotinamidine (MA-1266), and 6-[5-{4-(dimethylamino)phenyl}furan-2-yl]nicotinonitrile (MA-1250) on carbon steel (C-steel) was investigated in 1.0 mol·L-1 HCl solution by weight loss (WL), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. Morphological analysis was performed on the uninhibited and inhibited C-steel using atomic force microscope (AFM) and Infrared Spectroscopy (ATR-IR) methods. The effect of temperature was studied and discussed. Inspection of experimental results revealed that the inhibition efficiency (IE) increases with the incremental addition of inhibitors and with elevating the temperature of the acid media. The adsorption of furanylnicotinamidine derivatives on C-steel follows Temkin's isotherm. PP studies indicated that the investigated compounds act as mixed-type inhibitors and showed that p-dimethylaminophenyl furanylnicotinamidine derivative (MA-1256) was the most efficient inhibitor among the other studied derivatives with IE reached (95%) at 21×10-6 mol·L-1. MA-1266 is highly soluble in aqueous solution and has non-toxicity profile with LC50 >37 mg·L-1. Thus, MA-1266 can be a promising green corrosion inhibitor candidate with IE >91% at 21×10-6 mol·L-1. The experiments were coupled with computational chemical theories such as quantum chemical and molecular dynamic methods. The experimental results were in good agreement with the computational outputs.
    Energy, Resources and Environmental Technology
    Decomposition of carbon dioxide hydrate in the samples of natural coal with different degrees of metamorphism
    Vyacheslav G. Smirnov, Valeriy V. Dyrdin, Andrey Yu. Manakov, Zinfer R. Ismagilov
    2020, 28(2):  492-501.  doi:10.1016/j.cjche.2019.06.002
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    Methane and carbon dioxide hydrates are one of the possible forms in which these gases exist in natural coal (for more detailed discussion see Refs [1,2]). In this work, the decomposition of carbon dioxide hydrate in five samples of natural coal differing from each other in metamorphism degree was investigated experimentally. Carbon dioxide hydrate dispersed in coals was synthesized from water adsorbed in these coals. During a linear temperature rise in an autoclave with the coal + hydrate sample the hydrate decomposition manifests itself as a step of increase in gas pressure, accompanied by a decrease/stabilization of the temperature of coal sample. The dependencies of the amount of hydrate formed on initial coal humidity and on gas pressure during hydrate formation were studied. It was demonstrated that each coal sample is characterized by its own humidity threshold below which hydrate formation in natural coal is impossible. With an increase in gas pressure, the amount of water transformed into hydrate increases. For the studied coal samples, the decomposition of carbon dioxide hydrates proceeds within a definite temperature and pressure range, and this range is close to the curve of phase equilibrium for bulk hydrate.
    Advances of macroalgae biomass for the third generation of bioethanol production
    Inn Shi Tan, Man Kee Lam, Henry Chee Yew Foo, Steven Lim, Keat Teong Lee
    2020, 28(2):  502-517.  doi:10.1016/j.cjche.2019.05.012
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    In recent years, utilization of renewable sources for biofuel production is gaining popularity due to growing greenhouse gas (GHG) emissions which causes global warming. There has been a great effort in exploring alternative feedstock for bioethanol production. In this context, the production of third-generation bioethanol from macroalgae has emerged as an alternative feedstock to food crop-based starch and lignocellulosic biomass. This is mainly due to the fast growth rate of macroalgae, no competition with agricultural land, high carbohydrate content and relatively simple processing steps compared to lignocellulosic biomass. This review paper provides an insight of recent innovative approaches for macroalgae bioethanol production, including conventional and advanced hydrolysis process to produce fermentable sugar, various fermentation technologies, economic analysis and life cycle assessment. With the current technology maturity, efficient utilization of macroalgae as sustainable source for bioethanol and other value-added chemicals production could be achieved in the near future.
    Parametric optimization of packed bed for activated coal fly ash waste heat recovery using CFD techniques
    Kai Liang, Saimeng Jin, Hengzhi Chen, Jingzheng Ren, Weifeng Shen, Shun'an Wei
    2020, 28(2):  518-525.  doi:10.1016/j.cjche.2019.06.004
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    Coal fly ash is an industrial solid waste generated from coal preparation during the processing and cleaning of coal for electric power generation. Comprehensive investigation on the reutilization of waste heat of activated coal fly ash is of great economic significance. The method of recovering the waste heat, proposed in this study, is the transfer of heat from activated coal fly ash to gas with the movement of air using the packed bed, providing valuable energy sources for preheating the raw coal fly ash to reduce the overall energy consumption. The investigation is carried on the heat transfer characteristics of gas-solid (activated coal fly ash) phases and air temperature fields of the packed bed under some key conditions via computational fluid dynamics. A two dimensional geometry is utilized to represent key parts of packed bed. The distribution mechanism of the temperature field for gas phase is analyzed based on the transient temperature contours at different times. The results show that the obtained rule of gas-solid heat transfer can effectively evaluate the influences of operating parameters on the air temperature in the packed bed. Simultaneously, it is found that no temperature differences exist in the hot air at the outlet of the packed bed. The investigation provides guidance for the design and optimization of other similar energy recovery apparatuses in industries.
    Remediation of diesel oil contaminated sand by micro-emulsion
    Yinglu Gu, Shuang Chen, Hui'e Liu, Jun Li, Yutong Liu, Long Wang
    2020, 28(2):  526-531.  doi:10.1016/j.cjche.2019.07.004
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    Micro-emulsion has unique advantages in repairing diesel oil contaminated sand due to its low interfacial tension and strong solubility. By Winsor phase diagram, it was found that with the increase of salinity, the phase of microemulsion transformed from Winsor I to Winsor III to Winsor II. Under cryogenic electron microscope, it was observed that Winsor I was O/W type, Winsor II was W/O type, and Winsor III type was bi-continuous type. The effect of inorganic salts, alcohol and temperature on the oil removal rate of diesel oil contaminated sand was investigated by static recovery of micro-emulsion precursor. The results showed that for the anionic microemulsion system, with the increase of salinity and alcohols, the oil yield of the upper phase increased first and then decreased, and the two components had a certain compensation effect. For non-ionic micro-emulsion system, with the increase of temperature, the oil yield in the upper phase rose first and then decreased. At the same time, the influence of leaching conditions on oil removal rate was investigated by one-dimensional sand column leaching experiment. It was found that for diesel oil contaminated sand with 15% oil content, when the formulation was 2.00 wt% SDBS, 4.05 wt% n-butanol and 0.40 wt% sodium chloride, the optimum leaching conditions were leaching rate of 4 ml·min-1 and leaching amount of 400 ml. Under such conditions, the oil removal rate was up to 82.84%, that is, the oil content of the sand was reduced to 2.57%. Moreover, the micro-emulsion has good cyclicity, and it can still achieve high oil yield after six cycles.
    A DFT and TD-DFT study on electronic structures and UV-spectra properties of octaethyl-porphyrin with different central metals (Ni, V, Cu, Co)
    Xiaoqin Wang, Shiyi Li, Liang Zhao, Chunming Xu, Jinsen Gao
    2020, 28(2):  532-540.  doi:10.1016/j.cjche.2019.07.008
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    In this work, the octaethyl-porphyrins with different central metals (M-OEP, M=Ni, VO, Cu, Co) were used to investigate the ground-state molecular structure, electron distribution and UV-spectra properties on molecular level by density functional theory (DFT). The results showed that the calculation structure parameters of metalloporphyrins agreed well with the experimental value. According to the Natural Bond Orbital (NBO) analysis, the charge distribution of different metalloporphyrins was found that the charge values of the central metal M decreased with the order of VO < Ni < Co < Cu, while the bonding strength between M and the coordinating atom N was VO > Ni > Co > Cu. At the same time, the frontier molecular orbital calculations showed that the SOMO energy of VO (OEP) molecules in the open-shell system was higher than that of Co (OEP) and Cu (OEP), which means that its UV absorption characteristic peak would be red-shifted. In addition, the IEFPCM model of Time-dependent Density functional theory (TD-DFT) was further utilized to simulate the four substance in toluene solution: Co (OEP), Ni (OEP), Cu (OEP) and VO (OEP), and the Soret band peaks were calculated respectively as: 382 nm, 383 nm, 391 nm and 401 nm. Furthermore, the quantitative simulation analysis of metalloporphyrins was combined with experimental data. It could be found that the location rules of the four kinds of metalloporphyrins calculated absorption characteristic peaks were consistent with the experimental ones, and the relative errors of each peak were within 3%. These methods used above provide a theoretical path for analyzing and identifying unknown porphyrin compounds in petroleum.
    Improving physicochemical characteristics and anaerobic digestion performance of rice straw via ammonia pretreatment at varying concentrations and moisture levels
    Hairong Yuan, Ruolin Guan, Akiber Chufo Wachemo, Yatian Zhang, Xiaoyu Zuo, Xiujin Li
    2020, 28(2):  541-547.  doi:10.1016/j.cjche.2019.07.009
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    Rice straw physicochemical characteristics and anaerobic digestion (AD) performance via ammonia pretreatment at varying ammonia concentrations (2%, 4%, and 6%) and moisture contents (30%, 50%, 70%, and 90%) under a mild condition were investigated. The results showed that the ammonia pretreatment effectively damaged the rice straw structure, increased the soluble organic concentration, and improved rice straw hydrolysis and AD performance. After pretreatment, the ester bond and ether bond were ruptured in lignocellulose and the volatile fatty acids (VFAs) were within the range of 1457.81-1823.67 mg·L-1. In addition, ammonia pretreatment had high selectivity on lignin removal, resulting in a maximum lignin removal rate of 50.80%. The highest methane yield of rice straw was 250.34 ml·(g VS)-1 at a 4% ammonia concentration coupled with a 70% moisture content, which was 28.55% higher than that of the control. The result showed that ammonia pretreatment of rice straw is technically suitable to enhance AD performance for further application.
    Mild oxidative degradation of spent auricularia auricular substrate and molecular composition of carboxylic acids in the resulting soluble portion
    Xiaoli Xue, Zhimin Zong, Guanghui Liu, Xianyong Wei
    2020, 28(2):  548-555.  doi:10.1016/j.cjche.2019.07.014
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    Spent auricularia auricular substrate (SAAS) was oxidatively degraded with aqueous hydrogen peroxide (AHPO)/ acetic anhydride (AAH) to produce carboxylic acids (CAs) under mild conditions. The results show that up to 53.6% of the organic matter in SAAS was converted to the soluble species (SSs). In total 122 CAs were detected in the SSs by the analysis with a gas chromatograph/mass spectrometer, which can be classified into 29 group components, mainly being aliphatic acids and along with small amount of aromatic acids. Among the aliphatic acids, normal alkanedioic acids are the most abundant. The detected aromatic acids include benzoic acids, phthalic acids, trimellitic acids, pyromellitic acids, and their derivatives. The synergistic oxidation and the released ·OH, CH3COO·, and HOO· induced by AHPO/AAH play crucial roles in oxidatively degrading SAAS.
    Robust online temperature estimation of a membrane-wall gasifier
    Jianliang Xu, Qinfeng Liang, Zhenghua Dai, Xiaolei Guo, Haifeng Liu, Xin Gong
    2020, 28(2):  556-565.  doi:10.1016/j.cjche.2019.08.002
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    The gasifier temperature is a key parameter in the operation of a slag-tapping entrained-flow gasifier. However, there is no effective method for measuring the operating temperature of a membrane-wall-lined gasifier. In this study, a novel robust method for estimation of the online temperature was developed for a membrane-wall gasifier and applied in an industrial SE gasifier. The industrial test results show that the method can estimate the gasifier temperature within 0.04 s, and its value can be reliably obtained. Based on the combination of bench-scale gasifier validation, commercial-scale gasifier operation experience, and the comparison of different simulation methods, the proposed method is accurate and reliable for measuring the operating temperature of a membrane-wall-lined gasifier.
    Influence of dispersants on coal-water slurry prepared from the solid residue of plasma pyrolysis of coal
    Chao Qian, Liang Zhao, Xin Ge, Xinzhi Chen
    2020, 28(2):  566-570.  doi:10.1016/j.cjche.2019.08.007
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    This work presents the influence of dispersants on coal-water slurry (CWS), which was prepared from the solid residue of plasma pyrolysis of coal. The effects of dispersant type, solid concentration, dispersant content, and temperature on the rheological properties of CWS are examined. A suitable empirical model regarding the relation between viscosity and temperature is proposed. Through the sedimentation experiment of CWS, dispersants are found to significantly promote the stability of CWS.
    Manganese leaching in high concentration flue gas desulfurization process with semi-oxidized manganese ore
    Dong Sun, Guangzhi Xin, Lu Yao, Lin Yang, Xia Jiang, Wenju Jiang
    2020, 28(2):  571-578.  doi:10.1016/j.cjche.2019.09.006
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    Manganese leaching during high concentration flue gas desulfurization process with semi-oxidized manganese ore was studied in this paper. It was found that there were different reaction pathways among which MnO2, Mn2O3 and MnCO3 in semi-oxidized manganese ore during flue gas desulphurization and manganese leaching. High SO2 concentration facilitated redox reaction between MnO2 and SO2, and high concentration of H2SO4 accelerated MnCO3/Mn2O3 leaching from semi-oxidized ore. Kinetics study showed that manganese leaching in flue gas desulfurization process with semi-oxidized ore was controlled by a mixed-control model, that is the surface chemical reaction and mass diffusion dominated both the oxidation of SO2 and manganese leaching process. The apparent activation energy was 13.05 kJ·mol-1 and the reaction orders with respect to SO2 and H2SO4 concentration were 1.38 and 0.10, respectively. Finally, a semi-empirical rate equation based on shrinking core model was derived to describe the process.
    Novel synthesis of SiOx/C composite as high-capacity lithium-ion battery anode from silica-carbon binary xerogel
    Xinxin Li, Hebang Shi, Liqiang Zhang, Jingbo Chen, Pengpeng Lü
    2020, 28(2):  579-583.  doi:10.1016/j.cjche.2019.11.003
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    Micro/nanostructured SiOx/C composite was firstly synthesized by carbothermal reduction of silica-carbon binary xerogel. The homogeneous dispersion feature of the two components in binary xerogel contributes to effectively carbothermally reduce the O/Si atomic ratio, enhancing the electrochemical activity of the SiOx component. The micron-sized SiO x/C spheres are composed of many near-spherical nanoparticles. The synthesized SiOx/C exhibits a stable and high reversible capacity of 830 mA·h·g-1 for 100 cycles, and excellent rate-capability. The homogeneous dispersion structure of phases, the micro/nanostructure and the high electrochemical activity of SiOx component combinedly contribute the excellent electrochemical performance.
    Materials and Product Engineering
    Fabrication, characterization and response surface method optimization for quantum efficiency of fluorescent nitrogen-doped carbon dots obtained from carboxymethylcellulose of oil palms empty fruit bunch
    Mohammed Abdullah Issa, Zurina Zainal Abidin, Shafreeza Sobri, Suraya Abdul-Rashid, Mohd Adzir Mahdi, Nor Azowa Ibrahim, Musa Y. Pudza
    2020, 28(2):  584-592.  doi:10.1016/j.cjche.2019.04.003
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    Bio based nitrogen doped carbon dots (N-CDs) were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine (EDA) through one-pot hydrothermal carbonization route. The optimum as-formed NCDs were thoroughly characterized via Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), UV-vis spectra (UV-Vis) and Fluorescence spectra (PL). Response surface methodology was statistically used to assess three independent variables that have major influence on the fluorescence quantum yield (QY), including temperature (230-270 ℃), time (2-6 h) and EDA mass (10%-23.3%). Based on analysis of variance (ANOVA) results, synthesis temperature was found to be the most influential factor on the QY, followed by time and EDA mass. Higher temperature, long synthesis time and high amount of EDA were satisfactorily enough for efficient carbonization conversion rate and obtaining highest QY of N-CDs. The obtained quadratic model (R2=0.9991) shows a good correlation between the experimental data and predicted values. The optimum synthetic parameters are of 270 ℃ temperature, 6 h reaction time and 23.3% of EDA mass. The optimized as-made N-CDs exhibited blue photoluminescence with both excitation dependent/independent phenomena and high nitrogen content. The maximum emission intensity was 426 nm at a maximum excitation wavelength of 320 nm, with a QY of up to 22.9%. XPS and FTIR data confirmed the existence of polar containing groups, such as carbonyl, carboxyl, hydroxyl and amino groups over the surface of N-CDs whereas nitrogen species in the form of (pyridinic and graphitic-N) were introduced in the aromatic carbon domains, which imparts the hydrophilic and photostability of N-CDs. Taking into account the low-cost and sustainable production of N-CDs, this method considered a feasible route for converting low quality waste into value-added nanomaterials and utilizing for different functionalization processes and analytical applications.
    Reversed ethane/ethylene adsorption in a metal-organic framework via introduction of oxygen
    Ling Yang, Wei Zhou, Hao Li, Ali Alsalme, Litao Jia, Jiangfeng Yang, Jinping Li, Libo Li, Banglin Chen
    2020, 28(2):  593-597.  doi:10.1016/j.cjche.2019.09.005
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    Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry. Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year. Adsorptive separation using C2H6-selective porous materials to directly produce high-purity C2H4 is more energy-efficient. We herein report the “reversed C2H6/C2H4 adsorption” in a metal-organic framework Cr-BTC via the introduction of oxygen on its open metal sites. The oxidized Cr-BTC(O2) can bind C2H6 over C2H4 through the active Cr-superoxo sites, which was elucidated by the gas sorption isotherms and density functional theory calculations. This material thus exhibits a good performance for the separation of 50/50 C2H6/C2H4 mixtures to produce 99.99% pure C2H4 in a single separation operation.
    Preparation and characterization of the n-HA/PVA/CS porous composite hydrogel
    Wei Liang, Zhongkuan Luo, Li Zhou
    2020, 28(2):  598-602.  doi:10.1016/j.cjche.2019.01.029
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    In this paper, a new method combines chemical/physical crosslinking, and emulsification-foaming porogenic was adopted to prepare n-hydroxyapatite (n-HA)/polyvinyl alcohol (PVA)/chitosan (CS) porous composite hydrogel using artificial cornea scaffold materials. The fabricate conditions, including the type and amount of emulsification-foaming porogen, mixing time and speed etc. were researched. The results showed the optimal condition that the alkylphenol polyoxyethylene ether (OP) acted as emulsification-foaming porogen, with the ratio of WPVA/WOP as 3.75, and mixing 15 min with a stirring speed of 800 r·min-1. Additionally, the fabricated composite hydrogel scaffold materials possessed interconnected internal holes, a moisture content of above 65%, and tensile strength of above 6 MPa. In vitro cytotoxicity and acute systemic toxicity assay confirmed that the scaffolds did not show any cytotoxicity. The as-prepared hydrogel could be a promising candidate for artificial cornea scaffold material.
    Mathematical model for iron corrosion that eliminates chemical potential parameters
    Hadi Seddiqi, Ali Sadatshojaie, Behzad Vaferi, Ehsan Yahyazadeh, Afshin Salehi, David A. Wood
    2020, 28(2):  603-612.  doi:10.1016/j.cjche.2019.09.007
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    Iron corrosion in acidic media is a natural phenomenon that converts elemental iron to a more chemically-stable form, i.e. its oxide and hydroxide. In this study, the iron corrosion process is modeled as a completely implicit problem, solved by a novel finite difference model to provide insight into the ionic aspects of corrosion behavior. This new mathematical model eliminates the chemical potential parameters from the corrosion process equations, thereby reducing the need for experimental determination of chemical potentials. The eliminatedchemical-potential-parameters model predicts and quantifies key parameters (concentrations of conjugate base ion, iron (II) ion, hydrogen ion, anodic and cathodic potentials, and the electrical current density) associated with the iron corrosion process in acidic solutions. The rigorous derivation and novel application of the eliminated-chemical-potential-parameters model and its results provide new insights into the iron corrosion process. The present model is also applicable in any industrial process which is associated with metal corrosion. The model helps to guide the design of future corrosion resistant systems, and various experimental studies pertaining to corrosion inhibition techniques.
    Synthesis of activated carbons from black sapote seeds, characterization and application in the elimination of heavy metals and textile dyes
    Alejandra Alicia Peláez-Cid, Vincent Romero-Hernández, Ana María Herrera-González, Alejandro Bautista-Hernández, Oscar Core?o-Alonso
    2020, 28(2):  613-623.  doi:10.1016/j.cjche.2019.04.021
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    Many different techniques may be used to remove industrial pollutants from wastewater. Adsorption using activated carbon has been reported to be an effective method. This work proposes the use of a vegetable residue (black sapote seeds) as a raw material for its synthesis. These carbons were chemically activated using phosphoric acid and carbonized at 673 and 873 K. Adsorption isotherms were constructed for the textile dyes on the carbons, and this data was treated using Langmuir's equation to quantitatively describe the adsorption process. The synthesized carbons were characterized using FTIR, EA, SEM, Nitrogen adsorption (specific surface areas of 879 and 652 m2·g-1), and their points of zero charge (2.1 and 2.3). It was possible to adsorb both heavy metals and textile dyes present in aqueous solutions and wastewaters using these activated carbons. Heavy metals were adsorbed almost completely by both carbons. Cationic dyes where adsorbed (58-59.8 mg·g-1) in greater amounts compared to anionic dyes (10-58.8 mg·g-1). The amount of anionic dyes adsorbed increased almost 30% by changing the pH of the solutions. One of the carbons was thermally regenerated on three occasions without losing its adsorption capacity and it was proved in a flow system.