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Table of Content
28 November 2020, Volume 28 Issue 11
    A review on single bubble gas–liquid mass transfer
    Yuyun Bao, Jinting Jia, Shuaifei Tong, Zhengming Gao, Ziqi Cai
    2020, 28(11):  2707-2722.  doi:10.1016/j.cjche.2020.07.037
    Abstract ( 365 )   PDF (1523KB) ( 307 )  
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    It is common to empirically correlate volumetric mass transfer coefficient kLa for predicting gas-liquid mass transfer in industrial applications, and the investigation of single bubble mass transfer is crucial for a detailed understanding of mass transfer mechanism. In this work, experiments, models and simulations based on the experimental results were highlighted to elucidate the mass transfer between single bubbles and ambient liquid. The experimental setups, measurement methods, the mass transfer of single bubbles in the Newtonian and the nonNewtonian liquid, models derived from the concept of eddy diffusion, the extension of Whitman's, Higbie's and Danckwerts' models, or dimensionless numbers, and simulation methods on turbulence, gas-liquid partition methods and mass transfer source term determination are introduced and commented on. Although people have a great knowledge on mass transfer between single bubbles and ambient liquid in single conditions, it is still insufficient when facing complex liquid conditions or some phenomena such as turbulence, contamination or non-Newtonian behavior. Additional studies on single bubbles are required for experiments and models in various liquid conditions in future.
    The application of molecular simulation in ash chemistry of coal
    Xin Dai, Jin Bai, Ping Yuan, Shiyu Du, Dongtao Li, Xiaodong Wen, Wen Li
    2020, 28(11):  2723-2732.  doi:10.1016/j.cjche.2020.06.024
    Abstract ( 443 )   PDF (2205KB) ( 263 )  
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    One of the crucial issues in modern ash chemistry is the realization of efficient and clean coal conversion. Industrially, large-scale coal gasification technology is well known as the foundation to improve the atom economy. In practice, the coal ash fusibility is a critical factor to determine steady operation standards of the gasifier, which is also the significant criterion to coal species selection for gasification. Since coal behaviors are resultant from various evolutions in different scales, the multi-scale understanding of the ash chemistry is of significance to guide the fusibility adjustment for coal gasification. Considering important roles of molecular simulation in exploring ash chemistry, this paper reviews the recent studies and developments on modeling of molecular systems for fusibility related ash chemistry for the first time. The discussions are emphasized on those performed by quantum mechanics and molecular mechanics, the two major simulation methods for microscopic systems, which may provide various insights into fusibility mechanism. This review article is expected to present comprehensive information for recent molecular simulations of coal chemistry so that new clues to find strategies controlling the ash fusion behavior can be obtained.
    Fluid Dynamics and Transport Phenomena
    CFD simulation of impeller shape effect on quality of mixing in two-phase gas–liquid agitated vessel
    Amir Heidari
    2020, 28(11):  2733-2745.  doi:10.1016/j.cjche.2020.06.036
    Abstract ( 258 )   PDF (4628KB) ( 200 )  
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    Mixing efficiency in two-phase gas-liquid agitated vessel is one of the important challenges in the industrial processes. Computational fluid dynamics technique (CFD) was used to investigate the effect of four different pitched blade impellers, including 15°, 30°, 45° and 60°, on the mixing quality of gas-liquid agitated vessel. The multiphase flow behavior was modeled by Eulerian-Eulerian multiphase approach, and RNG k-ε was used to model the turbulence. The CFD results showed that a strong global vortex plays the main role on the mixing quality of the gas phase in the vessel. Based on the standard deviation criterion, it was observed that the axial distribution of the gas phase in the 30° impeller is about 55% better than the others. In addition, the results showed that the 30° impeller has a uniform radial distribution over the other impellers and the maximum gas phase holdup in the vessel. Investigation of the power consumption of the impellers showed that the 30° impeller has the highest power consumption among the other pitched blade impellers. Also, examine the effect of same power condition for pitched blade impellers showed that the 30° impeller has the best mixing quality in this condition.
    A 2D numerical study on the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures on a vertical plate
    Lili Zhang, Guanmin Zhang, Yi Zhang, Maocheng Tian, Jingzhi Zhang
    2020, 28(11):  2746-2757.  doi:10.1016/j.cjche.2020.07.001
    Abstract ( 222 )   PDF (5758KB) ( 180 )  
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    To improve the transportation efficiency and reduce the supply cost, the liquefaction becomes an important technology to store and transport the natural gas. During the liquefaction, the various components (e.g. propane, ethane, methane etc.) undergo fractional condensation phenomenon due to their different boiling points. This means that when one component condenses, others play a role of non-condensable gas (NCG). In order to reveal the influence mechanism of NCG on this condensation process, a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures, namely the propane/methane (80%-95%), ethane/methane (65%-85%) and methane/nitrogen (2%-13%) mixtures, on a vertical plate. The model was proposed based on the diffusion layer model, and the finite volume method was used to solve the governing equations. A user defined function was developed by cell iterative method to obtain the source terms in the condensation process. The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of heat transfer coefficient. And for the above three mixtures, there is a negative correlation between the NCG concentration and the heat transfer coefficient. Meanwhile, the results show a good agreement with the experimental data, meaning that the proposed model is reliable. Three mixtures within same non-condensable mole fraction of 20% were also investigated, indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient. As a result, the presence of the lighter NCG contributes to a thicker boundary layer.
    Separation Science and Engineering
    Adsorption equilibrium and kinetics studies of divalent manganese from phosphoric acid solution by using cationic exchange resin
    Haibo Zhuang, Yanjun Zhong, Lin Yang
    2020, 28(11):  2758-2770.  doi:10.1016/j.cjche.2020.07.029
    Abstract ( 247 )   PDF (3703KB) ( 177 )  
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    There are numerous impurities in wet-process phosphoric acid, among which manganese is one of detrimental metallic impurities, and it causes striking negative effects on the industrial phosphoric acid production and downstream commodity. This article investigated the adsorption behavior of manganese from phosphoric acid employing Sinco-430 cationic ion-exchange resin. Resorting FT-IR and XPS characterizations, the adsorption mechanism was proved to be that manganese was combined with sulfonic acid group. Several crucial parameters such as temperature, phosphoric acid content and resin dose were studied to optimize adsorption efficiency. Through optimization, removal percentage and sorption capacity of manganese reached 53.12 wt%, 28.34 mg·g-1, respectively. Pseudo-2nd-order kinetic model simulated kinetics data best and the activation energy was evaluated as 6.34 kJ·mol-1 for the sorption reaction of manganese. In addition, the global adsorption rate was first controlled by film diffusion process and second determined by pore diffusion process. It was found that the resin could adsorb up to 50.24 mg·g-1 for manganese. Equilibrium studies showed that Toth adsorption isotherm model fitted best, followed by Temkin and Langmuir adsorption isotherm models. Thermodynamic analysis showed that manganese adsorption was an endothermic process with enhanced randomness and spontaneity.
    Catalysis, Kinetics and Reaction Engineering
    Insights into the intrinsic interaction between series of C1 molecules and surface of NiO oxygen carriers involved in chemical looping processes
    Jinpeng Zhang, Hongfeng Gao, Nini Yuan, Qiang Wang, Yuhua Wu, Yanli Sun, Hongcun Bai
    2020, 28(11):  2771-2777.  doi:10.1016/j.cjche.2020.07.023
    Abstract ( 194 )   PDF (2138KB) ( 196 )  
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    Understanding and modulating the interaction between various reactive molecules and oxygen carriers are the key issue to achieve process intensification of chemical looping technology. C1 chemical molecules play an important role in many reactions involved with chemical looping processes. However, up to now, there is still a lack of systematic and in-depth understanding of the adsorption mechanism of C1 molecules on the surface of oxygen carriers (OCs). In this work, the intrinsic interaction between a series of C1 molecules composed of CH4, CO, CO2, CH3OH, HCHO and HCOOH and surface of NiO OCs in the chemical looping process have been studied using density functional theory calculations. Various adsorption configurations of C1 molecules and also different adsorption sites of NiO have been considered. The structural features of stable configuration of C1 molecules on the surface of NiO OCs have been obtained. Further, the interacted sites, types and strengths of C1 molecules on the surface of NiO have been directly pictured by the independent gradient model methods. Also, the nature of the interaction between C1 molecule and NiO surface has been investigated with the aid of energy decomposition analysis from a quantitative view.
    A high propylene productivity over B2O3/SiO2@honeycomb cordierite catalyst for oxidative dehydrogenation of propane
    Yuxi Zhou, Yang Wang, Wenduo Lu, Bing Yan, Anhui Lu
    2020, 28(11):  2778-2784.  doi:10.1016/j.cjche.2020.07.040
    Abstract ( 209 )   PDF (3312KB) ( 182 )  
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    Boron-based metal-free catalysts for oxidative dehydrogenation of propane (ODHP) have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity. Herein, the SiO2 and B2O3 sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B2O3 loadings (0.1%-10%) and calcination temperatures (600, 700, 800 ℃). SiO2 obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant Si-OH groups. The welldeveloped straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity (GHSV) and the thin wash-coated B2O3 layer can effectively facilitate the pore diffusion on the catalyst. The prepared B2O3/SiO2@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity (86.0%), olefin selectivity (97.6%, propylene and ethylene) and negligible CO2 (0.1%) at 16.9% propane conversion under high GHSV of 345,600 ml·(g B2O3)-1·h-1, leading to a high propylene space time yield of 15.7 g C3H6·(g B2O3)-1·h-1 by suppressing the overoxidation. The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels.
    High dispersion of heteropolyacid nanoparticles on hydrothermally Cs-modified three-dimensionally ordered macroporous SiO2 with excellent selectivity in methacrolein oxidation
    Heng Zhang, Junqi Liu, Chenyuan Liu, Tingting Wang, Wancheng Zhu
    2020, 28(11):  2785-2791.  doi:10.1016/j.cjche.2020.07.017
    Abstract ( 217 )   PDF (3600KB) ( 110 )  
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    Heteropolyacid nanoparticles (NPs) were supported on Cs-modified three-dimensionally ordered macroporous (3DOM) SiO2 and used as the catalyst for the oxidation of methacrolein (MAL) to methacrylic acid (MAA). Hydrothermal treatment and incipient wetness impregnation were employed respectively for the Cs-modification. It was found that hydrothermal Cs-modification of 3DOM SiO2 promoted the dispersion of the supported heteropolyacid, which showed an average particle size of 5.2 nm, much smaller than that (17.6 nm) on the Csmodified 3DOM SiO2 prepared by incipient wetness impregnation. The effects of hydrothermal treatment on the structure and catalytic performance of the catalyst were investigated. Results showed that the ion exchange between Cs+ and the surface silanol groups on 3DOM SiO2 was promoted with the increase of the hydrothermal temperature. Meanwhile, Cs-modification helped the heteropolyacid to retain intact Keggin structure, inhibiting the formation of MoO3. Highly dispersed heteropolyacid NPs with enhanced structural stability exhibited excellent selectivity to MAA in the oxidation of MAL.
    Process Systems Engineering and Process Safety
    Design of structure and control system of semiconductor refrigeration box
    Meng Yu, Zhiyun Zou
    2020, 28(11):  2792-2798.  doi:10.1016/j.cjche.2020.07.035
    Abstract ( 198 )   PDF (1368KB) ( 186 )  
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    In order to create low temperature environment for the valve testing, a new type of semiconductor refrigeration box based on semiconductor refrigeration chip and programmable logic controller (PLC) control system is designed. The power of the semiconductor refrigeration chip is determined by calculating the heat dissipation characteristics of the semiconductor refrigeration box. Combining natural convection heat dissipation with forced air cooling, the heat sink of semiconductor refrigeration chip is designed. In the control strategy, switch control is combined with an intelligent control strategy. Adaptive single neuron optimization algorithm based on quadratic optimization is adopted to adjust and optimize the parameters of the proportional-integral-derivative (PID) controllers in real time. Taking into account the limited hardware capabilities of the PLC, the Jacobian information in parameter adjustment is redesigned into a simplified form of identification. The actual test results of refrigeration box show good control performance.
    Facilitation of cascade biocatalysis by artificial multi-enzyme complexes—A review
    Xinlei Wei, Pingping Han, Chun You
    2020, 28(11):  2799-2809.  doi:10.1016/j.cjche.2020.05.022
    Abstract ( 252 )   PDF (1289KB) ( 564 )  
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    Multi-enzyme complexes are the results of natural evolution to facilitate cascade biocatalysis. Through enzyme colocalization within a complex, the transfer efficiency of reaction intermediates between adjacent cascade enzymes can be promoted, resulting in enhanced overall reaction efficiency. Inspired by nature, a variety of approaches have been developed for the assembly of artificial multi-enzyme complexes with different spatial organizations, aiming at improving the catalytic efficiency of enzyme cascade. A recent trend of this research area is the creation of enzyme complexes with a controllable spatial organization which helps with the mechanistic studies and bears the potential to further increase metabolic productivity. In this review, we summarize versatile strategies for the assembly of artificial multi-enzyme complexes, followed by an inspection of the mechanistic studies of artificial multi-enzyme complexes for their enhancement of catalytic efficiency. Furthermore, we provide some highlighted in vivo, ex vivo, and in vitro examples that demonstrate the ability of artificial multi-enzyme complexes for enhancing the overall production efficiency of value-added compounds. Recent research progress has revealed the great biotechnological potential of artificial multi-enzyme complexes as a powerful tool for biomanufacturing.
    Cell-free synthetic biology in the new era of enzyme engineering
    Nan Jiang, Lianju Ma, Yuan Lu
    2020, 28(11):  2810-2816.  doi:10.1016/j.cjche.2020.05.037
    Abstract ( 334 )   PDF (1777KB) ( 270 )  
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    With the gradual rise of enzyme engineering, it has played an essential role in synthetic biology, medicine, and biomanufacturing. However, due to the limitation of the cell membrane, the complexity of cellular metabolism, the difficulty of controlling the reaction environment, and the toxicity of some metabolic products in traditional in vivo enzyme engineering, it is usually problematic to express functional enzymes and produce a high yield of synthesized compounds. Recently, cell-free synthetic biology methods for enzyme engineering have been proposed as alternative strategies. This cell-free method has no limitation of the cell membrane and no need to maintain cell viability, and each biosynthetic pathway is highly flexible. This property makes cell-free approaches suitable for the production of valuable products such as functional enzymes and chemicals that are difficult to synthesize. This article aims to discuss the latest advances in cell-free enzyme engineering, assess the trend of this developing topical filed, and analyze its prospects.
    Immobilization of carbonic anhydrase for facilitated CO2 capture and separation
    Zhenhua Wu, Yan Nan, Yang Zhao, Xueying Wang, Shouying Huang, Jiafu Shi
    2020, 28(11):  2817-2831.  doi:10.1016/j.cjche.2020.06.002
    Abstract ( 210 )   PDF (9691KB) ( 44 )  
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    Carbonic anhydrase (CA) as a typical metalloenzyme in biological system can accelerate the hydration/dehydration of carbon dioxide (CO2, the major components of greenhouse gases), which performer with high selectivity, environmental friendliness and superior efficiency. However, the free form of CA is quite expensive (~RMB 3000/100 mg), unstable, and non-reusable as the free form of CA is not easy for recovery from the reaction environment, which severely limits its large-scale industrial applications. The immobilization may solve these problems at the same time. In this context, many efforts have been devoted to improving the chemical and thermal stabilities of CA through immobilization strategy. Very recently, a wide range of available inorganic, organic and hybrid compounds have been explored as carrier materials for CA immobilization, which could not only improve the tolerance of CA in hazardous environments, but also improve the efficiency and recovery to reduce the cost of large-scale application of CA. Several excellent reviews about immobilization methods and application potential of CA have been published. By contrast, in our review, we stressed on the way to better retain the biocatalytic activity of immobilized CA system based on different carrier materials and to solve the problems facing in practical operations well. The concluding remarks are presented with a perspective on constructing efficient CO2 conversion systems through rational combining CA and advanced carrier materials.
    The production of enantiopure D-lysine from L-lysine by a two-strain coupled system
    Sheng Xu, Xiaolu Lu, Xin Wang, Zhen Gao, Kequan Chen, Pingkai Ouyang
    2020, 28(11):  2832-2836.  doi:10.1016/j.cjche.2020.06.020
    Abstract ( 273 )   PDF (1513KB) ( 66 )  
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    The microbial production of D-lysine to replace chemical approach has gained great interest with the rising concerns over the environment. Here, we employed recombinant E. coli strain BL21-LYR with lysine racemase and strain BL-22A-RB-YB with L-lysine monooxygenase and 5-aminovaleramide amidohydrolase to establish a two-strain coupling whole-cell bioconversion system for D-lysine production from L-lysine. To improve the optical purity of D-lysine, the optimal reaction condition for resolution of DL-lysine after the racemization was investigated. The specificity of BL-22A-RB-YB for L-lysine and the effects of reaction condition on bioconversion efficiency of whole-cell were accordingly determined. Under the optimal condition, a maximum 53.5 g·L-1 Dlysine and 48.2 g·L-1 5-AVA were obtained with yield of 47.4% and 42.3%, respectively, by the microbial racemization and asymmetric degradation process. The final D-lysine enantiomeric excess was over 99%. Meanwhile, a valuable compound 5-aminovaleric acid was synthesized with the production of D-lysine, indicating the economic feasibility of the two-strain coupling system.
    Design and regulation of the surface and interfacial behavior of protein molecules
    Qianqian Hou, Nanxing Li, Yuanyuan Chao, Shihao Li, Lin Zhang
    2020, 28(11):  2837-2847.  doi:10.1016/j.cjche.2020.05.035
    Abstract ( 149 )   PDF (5581KB) ( 131 )  
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    Surface and interfacial behavior of protein molecules are crucial for the protein function involved in many biochemical processes and biomedical products such as enzyme design, bio-separation, drug design and delivery. This article is devoted to an overview of design and regulation of the surface and interfacial behavior of protein molecules. The improvement of enzyme surface such as the directed evolution and the rational design of enzymes is introduced at first, followed by the rational design of protein interface for the protein assembly. Thereafter, the design of micro-environment and ligands are described as two examples for the design guided by protein surface. Then the design of protein surface and interface with the help of artificial intelligence will be discussed.
    Chemical Engineering Thermodynamics
    Investigation of CO2 solubility in monoethanolamine hydrochloride based deep eutectic solvents and physical properties measurements
    Khatereh Ali Pishro, Ghulam Murshid, Farouq Sabri Mjalli, Jamil Naser
    2020, 28(11):  2848-2856.  doi:10.1016/j.cjche.2020.07.004
    Abstract ( 289 )   PDF (1682KB) ( 256 )  
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    Deep eutectic solvents (DESs) have drawn a growing research interest for applications in a wide range of scientific and industrial arenas. However, a limited effort has been reported in the area of gas separation processes and particularly the carbon dioxide capture. This study introduces a novel set of DESs that were prepared by complexing ethylenediamine (EDA), monoethanolamine (MEA), tetraethylenepentamine (TEPA), triethylenetetramine (TETA) and diethylenetriamine (DETA) as hydrogen bond donors to monoethanolamide hydrochloride (EAHC) salt as a hydrogen bond acceptor. The absorption capacity of CO2 was evaluated by exploiting a method based on measuring the pressure drop during the absorption process. The solubility of different DESs was studied at a temperature of 313.15 K and initial pressure of 0.8 MPa. The DES systems 1EAHC:9DETA, 1EAHC:9TETA and 1EAHC:9TEPA achieved the highest CO2 solubility of 0.6611, 0.6572 and 0.7017 mol CO2·(mole DES)-1 respectively. The results showed that CO2 solubility in the DESs increased with increasing the molar ratio of hydrogen bond donor. In addition, the CO2 solubility increased as the number of amine groups in the solvent increases, therefore, increasing the alkyl chain length in the DESs, resulted in increasing the CO2 solubility. FTIR analysis confirms the DES synthesis since no new functional group was identified. The FTIR spectra also revealed the carbamate formation in DES-CO2 mixtures. In addition, the densities and viscosities of the synthesized DESs were also measured. The CO2 initial investigation of reported DESs shows that these can be potential alternative for conventional solvents in CO2 capture processes.
    Energy, Resources and Environmental Technology
    Melting heat transfer enhancement of a horizontal latent heat storage unit by fern-fractal fins
    Zilong Deng, Suchen Wu, Hao Xu, Yongping Chen
    2020, 28(11):  2857-2871.  doi:10.1016/j.cjche.2020.08.022
    Abstract ( 217 )   PDF (21721KB) ( 62 )  
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    The latent heat storage (LHS) technique is of crucial importance in chemical energy engineering. Inspired by multi-bifurcated fern leaves, a mimic fern-fractal fin is designed to improve the thermal energy charging efficiency. This paper develops a transient melting model of a rectangular LHS unit using fern-fractal fins, and their melting behaviors are compared with the conventional fins. Besides, a parametric optimization of fernfractal fins is conducted for maximizing the thermal efficiency based on the response surface method (RSM). The results indicate that the temperature uniformity is more superior and the melting duration is shorter for the fern-fractal LHS unit when compared with the conventional one. Interestingly, the fern-fractal LHS device presents a slower heat storage rate during the initial conduction-dominated and early convection-dominated melting stages, while a prominent melting enhancement is achieved during the later melting stage. The shortest melting time is obtained based on the RSM technique when a fern-fractal fin with length ratio α=0.94 and branch angle θ=54.7° is utilized. Compared with a conventional fin, the averaged heat storage rate increases by 88.3%, and the total melting time is declined by 40.3% for an optimized fern-fractal fin.
    A high-performance biochar produced from bamboo pyrolysis with in-situ nitrogen doping and activation for adsorption of phenol and methylene blue
    Zhenhao Li, Bo Xing, Yan Ding, Yunchao Li, Shurong Wang
    2020, 28(11):  2872-2880.  doi:10.1016/j.cjche.2020.03.031
    Abstract ( 250 )   PDF (2505KB) ( 267 )  
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    Nitrogen doping is a promising method for the preparation of functional carbon materials. In this study, a nitrogen-doped porous coral biochar was prepared by using bamboo as raw material, urea as nitrogen source, and KHCO3 as green activator through in-situ pyrolysis. The structure of the obtained biochar was characterized by various techniques including nitrogen adsorption and desorption, Raman spectroscopy, X-ray photoelectron spectrometer, and etc. The adsorption properties of nitrogen-doped biochar were evaluated with phenol and methylene blue probes. The results showed that the nitrogen source ratio had a significant effect on the evolution of pore structure of biochar. Low urea addition ratio was beneficial to the development of pore structures. The optimum specific surface area of nitrogen-doped biochar could be up to 1693 m2·g-1. Nitrogen doping can effectively improve the adsorption capacity of biochar to phenol and methylene blue. Biochar prepared at 973.15 K with low urea addition ratio exhibited the highest adsorption capacity for phenol and methylene blue, and the equilibrium adsorption capacity was 169.0 mg·g-1 and 499.3 mg·g-1, respectively. By comparing the adsorption capacity of various adsorbents in related fields, it is proved that the nitrogen-doped biochar prepared in this study has a good adsorption effect.
    Ultrafiltration recovery of alginate: Membrane fouling mitigation by multivalent metal ions and properties of recycled materials
    Daqi Cao, Jingyi Jin, Qunhui Wang, Xin Song, Xiaodi Hao, Eiji Iritani, Nobuyuki Katagiri
    2020, 28(11):  2881-2889.  doi:10.1016/j.cjche.2020.05.014
    Abstract ( 167 )   PDF (2773KB) ( 57 )  
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    Recovery of alginate extracted from aerobic granular sludge (AGS) has given rise to a novel research direction. However, these extracted alginate solutions have a water content of nearly 100%. Alternately, ultrafiltration (UF) is generally used for concentration of polymers. Furthermore, the introduction of multivalent metal ions into alginate may provide a promising method for the development of novel nanomaterials. In this study, membrane fouling mitigation by multivalent metal ions, both individually and in combination, and properties of recycled materials were investigated for UF recovery of sodium alginate (SA). The filtration resistance showed a significantly negative correlation with the concentration of metal ions, arranged in the order of Mg2+ < Ca2+ < Fe3+ < Al3+ (filtration resistance mitigation), and the moisture content of recycled filter cake showed a marked decrease. For Ca2+, Mg2+, Fe3+, and Ca2++Fe3+, the filtration resistances were almost the same when the total charge concentration was less than 5 mmol·L-1. However, when the total charge concentration was greater than 5 mmol·L-1, membrane fouling mitigation increased significantly in the presence of Ca2+ or Fe3+ and remained constant for Mg2+ with the increase of total charge concentration. The filtration resistance mitigation was arranged in the order of Fe3+ > Fe3+ + Ca2+ > Ca2+ > Mg2+. Three mechanisms were proposed in the presence of Fe3+, such as the decrease of SA concentration, change in pH, and production of hydroxide iron colloids from hydrolysis. The properties of recycled materials (filter cake) were investigated via optical microscope observation, dynamic light scattering, Fourier transform infrared, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The results provide further insight into UF recoveries of alginate extracted from AGS.
    Numerical simulation on optimization of structure and operating parameters of a novel lean coal decoupling burner
    Jing Wang, Ruiping Zhang, Fengling Yang, Fangqin Cheng
    2020, 28(11):  2890-2899.  doi:10.1016/j.cjche.2020.05.039
    Abstract ( 193 )   PDF (3648KB) ( 64 )  
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    Due to its low volatile characteristics of lean coal, it is difficult to catch fire and burn out. Therefore, high temperature is needed to maintain combustion efficiency, while, this leads to high nitrogen oxide emission. For power plant boilers burning lean coal, stable combustion with lower nitrogen oxide emission is a challenging task. This study applied the 3D numerical simulation on the analysis of a novel de-coupling burner for low-volatile coal and its structure and operation parameters optimization. Results indicate that although it was more difficult for lean coal decoupling burner to ignite lean coal than high volatile coal, the burner formed a stepwise ignition trend, which promoted the rapid ignition of lean coal. Comparison of three central partition plate structure shows that in terms of characteristics of the flow field distribution, rich and lean separation and combustion, the structure with an inclination of 0° showed good performance, with its rich-lean air ratio being 0.85 and concentration ratio being 22.94, and there was an apparent decoupling combustion characteristic. Finally, the structure of the selected burner was optimized for its operational conditions. The optimal operating parameters was determined as the primary air velocity of 24.9 m·s-1 and the mass flow rate of pulverized coal of 2.5 kg·s-1, in which the pyrolysis products were utilized as reductive agent more fully. Eventually, the nitrogen oxide was efficiently reduced to nitrogen, which emission concentration was 61.88% lower than that in the design condition.
    Temperature field simulation of polyolefin-absorber mixture by FDTD-FDM model during microwave heating
    Xiaodong Jing, Hao Wen, Zhihong Xu
    2020, 28(11):  2900-2917.  doi:10.1016/j.cjche.2020.06.004
    Abstract ( 221 )   PDF (9035KB) ( 38 )  
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    This work has performed a numerical simulation of the temperature field during microwave heating of polyolefin-absorber mixture by means of a combined electric and thermal model. A finite difference time domain was used to model the electric field distribution within the cavity, while the finite difference method was used to calculate the temperature field distribution in different reactors. This study has focused only on the process from room temperature to 500 K for reducing heating time and energy consumption. This temperature range is a process with high energy consumption, difficult to control and great influence on the follow-up reaction. Temperature dependence of dielectric properties and thermal properties of heated materials are fully considered and simulated through an iterative process. The simulation results show that input power, the size and location of the heated materials, the position of the waveguide, and the kinds of microwave absorbers are important factors affecting the heating process. As a result, the uniform temperature distribution (the temperature difference Td < 10 K) can be achieved by choosing the appropriate input power (500-2000 W), the appropriate proportion of microwave absorber (the volume ratio of SiC to HDPE is 30:70), and combining with the moving and rotating of the heated materials. The uniform temperature field obtained without mechanical stirring is very important for reducing energy consumption and subsequent reactions.
    Performance, optimization, and mechanism of nitric oxide removal by thiourea dioxide/FeIIEDTA reaction systems
    Feiqiang He, Xinyu Zhu, Xianchun Chen, Jianhua Ding
    2020, 28(11):  2918-2927.  doi:10.1016/j.cjche.2020.06.021
    Abstract ( 190 )   PDF (2962KB) ( 92 )  
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    In this work, a new innovative absorption system containing both thiourea dioxide (TD) and FeEDTA was used to NO removal. The independently influences of O2 volume concentration, TD concentration, original pH value and absorbent temperature on NO removal in bubbling device were examined preliminarily. The results revealed that the NO removal efficiency firstly increased and then decreased with the increasing of the three independent variables (O2 volume concentration, TD concentration and temperature). However, the NO removal efficiency monotonously increased to some extent with pH value increasing from 6.5 to 10.5. In addition, the respective effects of the four variables and the interactive function of them on NO removal were checked with the response surface methodology (RSM) by central composite design (CCD). The calculative model showed that pH value possessed a main positive independent impact on NO removal. Furthermore, the interactive effects between any two factors were expounded by the 3D surface and counter plots. Finally, the optimum absorption conditions for the maximum NO removal at 94.3% experimentally and 95.8% statistically were obtained in O2 volume content of 6.0%, TD concentration of 0.02 mol·L-1, original pH value of 10.5 and absorption temperature of 42 ℃.
    Effects of the porous medium and water-silver biological nanofluid on the performance of a newly designed heat sink by using first and second laws of thermodynamics
    Amin Shahsavar, Sajad Entezari, Davood Toghraie, Pouya Barnoon
    2020, 28(11):  2928-2937.  doi:10.1016/j.cjche.2020.07.025
    Abstract ( 144 )   PDF (3224KB) ( 196 )  
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    The aim of this numerical investigation is to evaluate the laminar forced convection of biologically synthesized water-silver nanofluid through a heat sink (HS) filled with porous foam (PHS) using first and second laws of thermodynamics. The impacts of inlet velocity (V=0.5-3 m·s-1) and volume fraction of nanofluid (φ=0-1%) on the performance metrics of HS are assessed and the outcomes are compared with those of the non-porous HS (NHS). The outcomes revealed that for both the PHS and NHS, the increase of V causes an intensification in convection coefficient, pumping power, and entropy generation due to fluid friction, while the maximum CPU temperature, thermal resistance, and entropy generation due to the heat transfer reduces by boosting V. Also, it was found that the augmentation of V results in intensification in convection coefficient, pumping power, overall hydrothermal performance, and frictional entropy generation, while the opposite is true for maximum CPU temperature, thermal resistance, and thermal entropy generation. Furthermore, it was reported that, except for φ=0.5%, the overall hydrothermal performance of NHS is better than that of PHS, while PHS has better second-law performance than NHS in all the studied cases. Also, it can be concluded that the best hydrothermal performance for PHS belongs to φ= 1% and V=0.5 m·s-1, while for NHS, these values are 1% and 2 m·s-1.
    Activating solution gas drive as an extra oil production mechanism after carbonated water injection
    Mahmood Shakiba, Shahab Ayatollahi, Masoud Riazi
    2020, 28(11):  2938-2945.  doi:10.1016/j.cjche.2020.07.026
    Abstract ( 220 )   PDF (2485KB) ( 67 )  
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    Enhanced oil recovery (EOR) methods are mostly based on different phenomena taking place at the interfaces between fluid-fluid and rock-fluid phases. Over the last decade, carbonated water injection (CWI) has been considered as one of the multi-objective EOR techniques to store CO2 in the hydrocarbon bearing formations as well as improving oil recovery efficiency. During CWI process, as the reservoir pressure declines, the dissolved CO2 in the oil phase evolves and gas nucleation phenomenon would occur. As a result, it can lead to oil saturation restoration and subsequently, oil displacement due to the hysteresis effect. At this condition, CO2 would act as insitu dissolved gas into the oil phase, and play the role of an artificial solution gas drive (SGD).
    In this study, the effect of SGD as an extra oil recovery mechanism after secondary and tertiary CWI (SCWI-TCWI) modes has been experimentally investigated in carbonate rocks using coreflood tests. The depressurization tests resulted in more than 25% and 18% of original oil in place (OOIP) because of the SGD after SCWI and TCWI tests, respectively. From the ultimate enhanced oil recovery point of view, the efficiency of SGD was observed to be more than one-third of that of CWI itself. Furthermore, the pressure drop data revealed that the system pressure depends more on the oil production pattern than water production.
    Materials and Product Engineering
    Experimental investigation on the spread of aqueous foam over ethanol surface
    Xiaoyang Yu, Fan Li, Xuyang Miao, Ning Jiang, Ruowen Zong, Shouxiang Lu, Changhai Li
    2020, 28(11):  2946-2954.  doi:10.1016/j.cjche.2020.07.028
    Abstract ( 184 )   PDF (4948KB) ( 191 )  
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    The presence of ethanol has an adverse effect on foam spreading, and ethanol fire is difficult to extinguish with aqueous fire-fighting foams. Thus, it is necessary to explore the foam formulation suitable for ethanol fuels and study the spreading behavior of foam over ethanol surface. In the current work, stable foams based on hydrocarbon surfactant (SDS), fluorocarbon surfactant (FC1157), and polymers (XG) were prepared by using the compressed-air foam system. The spreading behaviors of foam on polar ethanol and non-polar heptane surface were observed and compared. Furthermore, the effects of stabilizer concentrations, foam flow rates and expansion ratios on foam spreading performance were investigated, respectively. The results indicate that aqueous SDS foam can spread on the heptane layer continuously, but it is difficult to cover the ethanol surface. The addition of XG and FC1157 can synergistically improve the spreading performance of aqueous foam over ethanol. Depending on stabilizer concentrations, there are remarkable differences in foam spreading behaviors. Besides, different foam application parameters including expansion ratios and foam flow rates significantly affect the foam spreading rate, despite the same foam formulation. The research methods and results guide the optimal design of foam formulations as well as the practical application of aqueous foam for ethanol fire extinguishment.