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SCI和EI收录∣中国化工学会会刊
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Table of Content
28 December 2020, Volume 28 Issue 12
    Fluid Dynamics and Transport Phenomena
    Numerical simulations and comparative analysis of two- and three-dimensional circulating fluidized bed reactors for CO2 capture
    Yefeng Zhou, Yifan Han, Yujian Lu, Hongcun Bai, Xiayi Hu, Xincheng Zhang, Fanghua Xie, Xiao Luo, Jingdai Wang, Yongrong Yang
    2020, 28(12):  2955-2967.  doi:10.1016/j.cjche.2020.07.003
    Abstract ( )   PDF (4949KB) ( )  
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    Carbon dioxide (CO2), the main gas emitted from fossil burning, is the primary contributor to global warming. Circulating fluidized bed reactor (CFBR) is proved as an energy-efficient method for post-combustion CO2 capture. The numerical simulation by computational fluid dynamics (CFD) is believed as a promising tool to study CO2 adsorption process in CFBR. Although three-dimensional (3D) simulations were proved to have better predicting performance with the experimental results, two-dimensional (2D) simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently. However, the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study. Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions, it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions. In this work, the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors, in which the separation rate, species distribution and hydrodynamic characteristics were comparatively studied for both model frames. With both accuracy and computational costs considered, the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions, which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.
    Bubble size fractal dimension, gas holdup, and mass transfer in a bubble column with dual internals
    Xiao Xu, Junjie Wang, Qiang Yang, Lei Wang, Hao Lu, Honglai Liu, Hualin Wang
    2020, 28(12):  2968-2976.  doi:10.1016/j.cjche.2020.07.030
    Abstract ( )   PDF (1904KB) ( )  
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    As the scale of residual oil treatment increases and cleaner production improves in China, slurry bubble column reactors face many challenges and opportunities for residual oil hydrogenation technology. The internals development is critical to adapt the long-term stable operation. In this paper, the volumetric mass transfer coefficient, gas holdup and bubble size in a gas-liquid up-flow column are studied with two kinds of internals. The gas holdup and volumetric mass transfer coefficient increase by 120% and 42% when the fractal dimension of bubbles increases from 0.56 to 2.56, respectively. The enhanced mass transfer processing may improve the coke suppression ability in the slurry reactor for residual oil treatment. The results can be useful for the exploration of reacting conditions, scale-up strategies, and oil adaptability. This work is valuable for the design of reactor systems and technological processes.
    Numerical simulation of a falling droplet surrounding by air under electric field using VOF method: A CFD study
    Mirollah Hosseini, Hossein Arasteh, Hamid Hassanzadeh Afrouzi, Davood Toghraie
    2020, 28(12):  2977-2984.  doi:10.1016/j.cjche.2020.07.048
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    This is a numerical study of a falling droplet surrounding by air under the electric field modeled with finite volume method by means of CFD. The VOF method has been employed to model the two-phase flow of the present study. Various capillary numbers are investigated to analyze the effects of electric field intensity on the falling droplet deformation. Also, the effects of electric potential on the heat transfer coefficient have been examined. The obtained results showed that by applying the electric field at a capillary number of 0.2 the droplet tends to retain its primitive shape as time goes by, with a subtle deformation to an oblate form. Intensifying the electric field to a capillary number of 0.8 droplet deformation is almost insignificant with time progressing; however, further enhancement in capillary number to 2 causes the droplet to deform as a prolate shape and higher values of this number intensify the prolate form deformation of the droplet and result in pinch-off phenomenon. Ultimately, it is showed that as the electric potential augments the heat transfer coefficient increases in which for electric potential values higher than 2400 V the heat transfer coefficient enhances significantly.
    Effect of elevated temperature and silica sand particle size on minimum fluidization velocity in an atmospheric bubbling fluidized bed
    A. Al-Farraji, Haidar Taofeeq
    2020, 28(12):  2985-2992.  doi:10.1016/j.cjche.2020.07.054
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    The impact of temperature and particle size on minimum fluidizing velocity was studied and analyzed in a small pilot scale of bubbling fluidized bed reactor. This study was devoted to providing some data about fluidization to the literature under high temperature conditions. The experiments were carried out to evaluate the minimum fluidizing velocity over a vast range of temperature levels from 20℃ to 850℃ using silica sand with a particle size of 300-425 μm, 425-500 μm, 500-600 μm, and 600-710 μm. Furthermore, the variation in the minimum fluidized voidage was determined experimentally at the same conditions. The experimental data revealed that the Umf directly varied with particle size and inversely with temperature, while εmf increases slightly with temperature based on the measurements of height at incipient fluidization. However, for all particle sizes used in this test, temperatures above 700℃ has a marginal effect on Umf. The results were compared with many empirical equations, and it was found that the experimental result is still in an acceptable range of empirical equations used. In which, our findings are not well predicted by the widely accepted correlations reported in the literature. Therefore, a new predicted equation has been developed that also accounts for the affecting of mean particle size in addition to other parameters. A good mean relative deviation of 5.473% between the experimental data and the predicted values was estimated from the correlation of the effective dimensionless group. Furthermore, the experimental work revealed that the minimum fluidizing velocity was not affected by the height of the bed even at high temperature.
    Separation Science and Engineering
    Adsorption of urea, creatinine, and uric acid from three solution types using spherical activated carbon and its recyclability
    Tomohito Kameda, Kazuya Horikoshi, Shogo Kumagai, Yuko Saito, Toshiaki Yoshioka
    2020, 28(12):  2993-3001.  doi:10.1016/j.cjche.2020.03.018
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    In this paper, we propose that the urinary toxins from the wastewater be adsorbed on an adsorbent such as spherical activated carbon and the latter be regenerated by subjecting it to high temperatures to recycle activated carbon and also to recycle the water used in dialysis. We studied the adsorption of artificial waste dialysate, which is a mixed solution of urea, creatinine, and uric acid, and the separate solutions for each of these and found that their extents of adsorption onto the spherical activated carbon material were nearly identical. The amount of adsorption was approximately 1.4 mg·g-1 for urea, 18 mg·g-1 for creatinine, and 20 mg·g-1 for uric acid. The urea, creatinine, and uric acid adsorbed onto the spherical activated carbon decomposed on heat treatment at 500℃, and the adsorption capacity of the spherical activated carbon was regenerated. Our study successfully demonstrated that the spherical activated carbon can be recycled in the waste dialysate treatment process.
    Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution
    M. Ajdar, A. Azdarpour, A. Mansourizadeh, B. Honarvar
    2020, 28(12):  3002-3010.  doi:10.1016/j.cjche.2020.05.004
    Abstract ( )   PDF (1997KB) ( )  
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    Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N2 permeation, overall porosity, critical water entry pressure (CEPw), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N2 permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m-1. CEPw of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m-2·h-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.
    Experiments and insights of desalination by a freezing/thawing method at low subcooling
    Jun Chen, Jianjian Wu, Jiafeng Xu, Qing Yuan, Bin Deng, Changzhong Chen, Zhi Li
    2020, 28(12):  3011-3017.  doi:10.1016/j.cjche.2020.05.012
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    Desalination by freezing/thawing method was a very important method to obtain fresh water from sea water. In this work, desalination by freezing/thawing method was conducted with initial sodium chloride of 3.5 wt% in consideration of stirring speed, freezing time and subcooling. The subcooling ranged from 1.2 K to 4 K. The optimum conditions for desalination in this work were stirring speed of 200 r·min-1, freezing time of 120 min, and subcooling of 3 K. The results also showed that sodium chloride cannot be effectively removed by once freezing/thawing process. The maximum removal efficiency of sodium chloride was 64.3%. Two major reasons resulting in the impurity of obtained melted water by freezing/thawing method were proposed. The first reason was the inevitable adhesion of salt solution to the surface of ice, which could be removed easily by distilled water flushing. The second reason was that salt solution was heterogeneously wrapped in the accumulated ice, which was difficult to be removed by distilled water flushing. The liquid flushing method was proposed to verify the conjecture, and the results were in accordance with the two reasons mentioned above. Additional method, such as multiple flushing liquid method, was suggested to be used during the freezing/thawing process for effectively removing sodium chloride, and obtaining fresh water.
    Fouling behavior of poly(vinylidene fluoride) (PVDF) ultrafiltration membrane by polyvinyl alcohol (PVA) and chemical cleaning method
    Weijie Ding, Min Chen, Ming Zhou, Zhaoxiang Zhong, Zhaoliang Cui, Weihong Xing
    2020, 28(12):  3018-3026.  doi:10.1016/j.cjche.2020.05.032
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    Severe fouling to poly(vinylidene fluoride) (PVDF) membrane is usually caused as filtrating the papermaking wastewater in the ultrafiltration (UF) process. In the paper, fouling behavior and mechanism were investigated, and the low-concentration polyvinyl alcohol (PVA) contained in the sedimentation tank wastewater was found as the main foulant. Consequently, the corresponding cleaning approach was proposed. The experiment and modeling results elaborated that the fouling mode developed from pore blockage to cake layer along with filtration time. Chemical cleaning conditions including the composition and concentration of reagents, cleaning duration and trans-membrane pressure were investigated for their effect on cleaning efficiency. Pure water flux was recovered by over 95% after cleaning the PVDF membrane using the optimal conditions 0.5 wt% NaClO (as oxidant) and 0.1 wt% sodium dodecyl benzene sulfonate (SDBS, as surfactant) at 0.04 MPa for 100 min. In the chemical cleaning method, hypochlorite (ClO-) could first chain-scissor PVA macromolecules to small molecules and SDBS could wrap the fragments in micelles, so that the foulants were removed from the pores and surface of membrane. After eight cycling tests, pure water flux recovery maintained above 95% and the reused membrane was found intact without defects.
    Catalysis, Kinetics and Reaction Engineering
    Upgrading Siberian (Russia) crude oil by hydrodesulfurization in a slurry reactor: A kinetic study
    Kening Sun, Xixi Ma, Qiuchen Yang, Rui Qiu, Ruijun Hou
    2020, 28(12):  3027-3034.  doi:10.1016/j.cjche.2020.04.020
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    Hydrodesulfurization (HDS) of sour crude oil is an effective way to address the corrosion problems in refineries, and is an economic way to process sour crude oil in an existing refinery built for sweet oil. In the current study, the HDS of Siberian crude oil was carried out in a slurry reactor. The Co-Mo, Ni-Mo, and Ni-W catalysts supported on γ-Al2O3 were compared at the temperature of 340℃ and the pressure of 4.5 MPa. The HDS activity follows the order of Co-Mo > Ni-Mo > Ni-W at a high concentration of H2S, and the difference between Co-Mo and Ni-Mo becomes insignificant at a low concentration of H2S. The influence of reaction temperature 320-360℃ and reaction pressure 3-5.5 MPa was investigated, and both play a positive role in the HDS reaction. A kinetic model over Ni-Mo/Al2O3 in the slurry reactor was established. The activation energy is estimated as 60.34 kJ·mol-1; the orders of sulfur components and hydrogen partial pressure are 1.43 and 1.30, respectively. The kinetic parameters are compared with those in a trickle-bed reactor, implying that the mass transfer is greatly enhanced in the slurry reactor. The back mixing effect is present in the slurry reactor and can be reduced by a multi-stage design, which would lead to higher reactor efficiency in industrial application.
    The effect of the Ce content on the oxidative dehydrogenation of propane over CrOy-CeO2/γ-Al2O3 catalysts
    Cheng Zuo, Man Wu, Qingjie Guo
    2020, 28(12):  3035-3043.  doi:10.1016/j.cjche.2020.04.022
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    A series of CrOy (17.5 wt%)-CeO2 (X wt%)/γ-Al2O3 catalysts (X=0, 0.5, 2, 5, 8) with various Ce contents were prepared by a wetness impregnation method and were applied to the dehydrogenation of propane to propylene at 550℃ and 0.1 MPa. The prepared catalysts were characterized by BET, H2-TPR, O2-TPD, XPS, XRD, SEM-EDS and Raman spectroscopy. Among the prepared catalysts, the 17.5Cr-2Ce/Al catalyst with the largest amount of lattice oxygen exhibited the best catalytic performance for the dehydrogenation of propane to propylene with lattice oxygen. The decreased presence of oxygen defects and reducibility were the factors responsible for the improved dehydrogenation activity of the catalysts. The CeO2 layer could inhibit the evolution of lattice oxygen (O2-) to electrophilic oxygen species (O2-), and the oxygen defects on the catalyst surface were reduced. The inhibited lattice oxygen evolution prevented the deep oxidation of propane or propylene, the average COx selectivity decreased from 24.41% (17.5Cr/Al) to 5.71% (17.5Cr-2Ce/Al), and the average propylene selectivity increased from 60.15% (17.5Cr/Al) to 85.05% (17.5Cr-2Ce/Al).
    Aureobasidium subglaciale F134 is a bifunctional whole-cell biocatalyst for Baeyer-Villiger oxidation or selective carbonyl reduction controllable by temperature
    Liqun Shen, Ran Cang, Guang Yang, Anqi Zeng, He Huang, Zhigang Zhang
    2020, 28(12):  3044-3051.  doi:10.1016/j.cjche.2020.06.041
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    The microbial production of either ester/lactones or enantio-enriched alcohols through Baeyer-Villiger oxidation or stereoselective reduction of ketones, respectively, is possible by using whole cells of A. subglaciale F134 as a bifunctional biocatalyst. The chemoselective pattern of acetophenone biotransformation catalyzed by these cells can be regulated through reaction temperature, directing the reaction either towards oxidation or reduction products. The Baeyer-Villiger oxidation activity of A. subglaciale F134 whole cells is particularly dependent on reaction temperature. Acetophenone was transformed efficiently to phenol via the primary Baeyer-Villiger product phenyl acetate at 20℃ after 48 h with 100% conversion. In contrast, at 35℃, enantio-enriched (S)-1-phenylethanol was obtained as the sole product with 64% conversion and 89% ee. In addition, A. subglaciale F134 cells also catalyze the selective reduction of various structurally different aldehydes and ketones to alcohols with 40% to 100% yield, indicating broad substrate spectrum and good enantioselectivity in relevant cases. Our study provides a bifunctional biocatalyst system that can be used in Baeyer-Villiger oxidation as well as in asymmetric carbonyl reduction, setting the stage for future work concerning the identification and isolation of the respective enzymes.
    Enhancing hydrothermal stability of framework Al in ZSM-5: From the view on the transformation between P and Al species by solid-state NMR spectroscopy
    Lei Han, Ying Ouyang, Enhui Xing, Yibin Luo, Zhijian Da
    2020, 28(12):  3052-3060.  doi:10.1016/j.cjche.2020.07.039
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    HZSM-5, with good surface acidity and shape selectivity, was reported as hydrocarbon cracking catalyst for multiple decades, however the hydrothermal stability, especially dealumination of tetrahedrally coordinated framework aluminum (TFAl), has been proved extensively as one of the major challenges during reactionregeneration process. Phosphorus was proposed to stabilize TFAl and indeed it enhanced the hydrothermal stability. Unfortunately, most of the phosphorus species would remain outside of the zeolite pore, mainly as polyphosphate species, and block the micropore severely, with only a limited portion introduced into the channel being able to interact with TFAl. Enlarging the pore size by alkali treatment (desilication) is one of the most convinced methods, but the details about specific P species during alkali treatment and its transformation upon hydrothermal activation is not acquired, thus the mechanism has not been fully understood. Herein, the P-containing species and its transformation during direct P modification and acid/alkali treatment followed by P modification have been studied, and the mechanism on the interaction between P and Al species has been investigated, using several analytical methods, especially Solid-state nuclear magnetic resonance (SSNMR) spectroscopy. It was found that the combination of desilication and subsequent phosphorus modification can enhance the activity of the ZSM-5 for the cracking of ethylcyclohexane, due to the better hydrothermal stabilization of acid sites by the enhanced interaction between phosphorus and TFAl, resulting from the improved accessibility of TFAl because of the successful generation of mesoporosity. Whereas the acid treatment followed by phosphorus modification, with declined retention of crystallinity and P/Al ratio, monoclinic/orthorhombic transition during steam activation, and the failed generation of mesopores, would cause obvious aggregation of the phosphorus species and could not improve the hydrothermal stability of the ZSM-5effectively, and the direct phosphatation turned out much worse. Finally, a specific index that the intensity of the signal at 39 in 27Al MAS NMR spectra before steam activation was proposed as the indicator for determining the efficiency of phosphorus modification. And the proposed mechanism on the interaction between phosphorus and TFAl during the phosphorus modification could also be applicable in other zeolites.
    Process Systems Engineering and Process Safety
    A subspace ensemble regression model based slow feature for soft sensing application
    Qiong Jia, Jun Cai, Xinyi Jiang, Shaojun Li
    2020, 28(12):  3061-3069.  doi:10.1016/j.cjche.2020.07.047
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    A novel adaptive subspace ensemble slow feature regression model was developed for soft sensing application. Compared to traditional single models and random subspace models, the proposed method is improved in three aspects. Firstly, sub-datasets are constructed through slow feature directions and variables in each subdatasets are selected according to the output related importance index. Then, an adaptive slow feature regression is presented for sub-models. Finally, a Bayesian inference strategy based on a slow feature analysis process that monitors statistics is developed for probabilistic combination. Two industrial examples were used to evaluate the proposed method.
    Multimodal process monitoring based on transition-constrained Gaussian mixture model
    Shutian Chen, Qingchao Jiang, Xuefeng Yan
    2020, 28(12):  3070-3078.  doi:10.1016/j.cjche.2020.08.021
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    Reliable process monitoring is important for ensuring process safety and product quality. A production process is generally characterized by multiple operation modes, and monitoring these multimodal processes is challenging. Most multimodal monitoring methods rely on the assumption that the modes are independent of each other, which may not be appropriate for practical application. This study proposes a transition-constrained Gaussian mixture model method for efficient multimodal process monitoring. This technique can reduce falsely and frequently occurring mode transitions by considering the time series information in the mode identification of historical and online data. This process enables the identified modes to reflect the stability of actual working conditions, improve mode identification accuracy, and enhance monitoring reliability in cases of mode overlap. Case studies on a numerical simulation example and simulation of the penicillin fermentation process are provided to verify the effectiveness of the proposed approach in multimodal process monitoring with mode overlap.
    Chemical Engineering Thermodynamics
    The effect of temperature on phase equilibria of polyethylene glycol (PEG8000)-K2SO4-H2O at T=(288.15, 298.15, 308.15) K
    Shuai Chen, Niancu Chen, Hong Zheng, Xudong Yu, Ying Zeng
    2020, 28(12):  3079-3085.  doi:10.1016/j.cjche.2020.07.002
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    The phase behavior of potassium sulfate (K2SO4) in polyethylene glycol with molecular weight 8000 (PEG8000) and water (H2O) mixed solvent at 288.15, 298.15, and 308.15 K were determined. According to the results, when the temperature are 288.15 and 298.15 K, there is only a solid-liquid phase equilibrium relationship in the system, and the phase diagrams are both divided into three parts which respectively are the regions of unsaturated homogeneous liquid (L), one liquid and one solid K2SO4 (L + S) and one liquid and two solids K2SO4 and PEG8000 (L + 2S). The solubility of K2SO4 in PEG8000-H2O mixed solvent decreased with the addition of the PEG8000 in the solution. Comparing the diagrams of 288.15 and 298.15 K, the sizes of regions of (L) and (L + S) increased and that of (L + 2S) decreased with the increase of temperature. While at 308.15 K, solid-liquid and liquid-liquid equilibrium coexist, and there are six parts in the complete phase diagram at 308.15 K, adding the areas of one liquid and one solid K2SO4 (L + S), two liquids (2 L), two liquids and one solid K2SO4 (2 L + S). The equations developed by Merchuk, Hu, and Jayapal were used to fit the binodal curves data of the system at 308.15 K, meanwhile, the experimental tie-line data of the system at 308.15 K were correlated by Othmer-Tobias equation and Bancroft equation.
    Insight into solute-solute and solute-solvent interactions of semicarbazide hydrochloride in water and D-glucose/D-sucrose+water solutions at temperatures (293.15 to 318.15) K
    Ankita, Dinesh Chand, Anil Kumar Nain
    2020, 28(12):  3086-3095.  doi:10.1016/j.cjche.2020.07.007
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    The solute-solute and solute-solvent interactions of drug semicarbazide hydrochloride with carbohydrates (D-glucose/D-sucrose) are investigated by using volumetric, viscometric and acoustic properties. The measurements of the densities ρ, ultrasonic speeds u, and viscosities η. of semicarbazide hydrochloride in 5% and 10% D-glucose/D-sucrose+water (w/w) solutions were carried out at temperatures (293.15-318.15) K and at pressure, p=101 kPa. The apparent molar volumes, Vϕ, limiting apparent molar volumes,Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks,ϕ°, partial molar expansibilities, Eϕ°, transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr° have been calculated from the experimental data. The viscosity data were examined by using the Jones-Dole equation and the viscosity A and B coefficients were evaluated. The results are discussed in terms of solute-solute and solute-solvent interactions in these solutions. The structure making/breaking ability of semicarbazide hydrochloride is examined using the sign of temperature derivative of B-coefficient, dB/dT.
    Biotechnology and Bioengineering
    Ethanol shock enhances the recovery of anthocyanin from lowbush blueberry
    Nueraili Maimaiti, Niyazi Aili, M. Kamran Khan, Zhigang Tang, Guoqiang Jiang, Zheng Liu
    2020, 28(12):  3096-3102.  doi:10.1016/j.cjche.2020.03.036
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    Deactivation of polyphenol oxidase (PPO) in natural products is essential for downstream processing of functional molecules used as food or food additives, particularly those served as antioxidants. In the present work, we identified two proteins with PPO activity from lowbush blueberry using ammonium sulphate precipitation and chromatography procedures. Deactivation of these proteins was studied using aqueous solutions of ethanol of different concentrations. The PPO activity was recovered after ethanol removal for the protein samples previously soaked in a low concentration ethanol solution. A complete and unrecoverable deactivation of the proteins was achieved using ethanol with concentration over 70% (v/v), as manifested by the significant changes in circular dichroism (CD) and fluorescence spectroscopy measurements. Based on these findings, we propose a new extraction process for blueberry anthocyanin, in which an ethanol shock, i.e. soaking blueberry fruit in a 70% (v/v) ethanol solution for 1 h, is implemented before subsequent procedures. This new process increases the anthocyanin yield by 55% in comparison to that without the ethanol shock.
    Bioaugmentation of two-stage aerobic sequencing batch reactor with mixed strains for high nitrate nitrogen wastewater treatment
    Mengmeng Wang, Gang Cao, Naixian Feng, Yongzhang Pan
    2020, 28(12):  3103-3109.  doi:10.1016/j.cjche.2020.08.014
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    Mixed strains Delftia sp.YH01 and Acidovorax sp.YH02, with capability of heterotrophic nitrification-aerobic denitrification, were introduced into a two-stage aerobic sequencing batch reactor to enhance NO3--N removal. With optimal C/N of 8, efficient NO3--N removal was achieved at initial NO3--N concentration of 2000 mg·L-1. Meanwhile, the massive accumulation of NO2--N was avoided during the long operation. Compared to the one-stage aerobic sequencing batch reactor, the removal efficiency of NO3--N and TN in the two-stage aerobic sequencing batch reactor was increased by 36.5% and 42.7%, which respectively was 93.8% and 88.4%. Microbial community study showed that the mixed strains have the stronger viability and can synergistically denitrify with the indigenous microorganisms in system, such as Azoarcus, Uncultured Saprospiraceae, Thauera, Paracocccus, which could be major contributors for aerobic denitrification. The proposed technology was shown to achieve high-efficiency treatment of high NO3--N wastewater through aerobic denitrification.
    Energy, Resources and Environmental Technology
    Effect of Al2O3/CaO on the melting and mineral transformation of Ningdong coal ash
    Feng Wang, Min Yao, Haoyong Kan, Jianping Kuang, Ping Li, Jiashuo Zhang, Yixin Zhang
    2020, 28(12):  3110-3116.  doi:10.1016/j.cjche.2020.04.001
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    Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier. Mineral conversion of coal ash is very significant to be investigated, because the mineral can affect the melting temperature and viscosity under high temperature conditions. In this paper, the effects of different Al2O3/CaO on the mineral conversion, melting temperature and viscosity of Ningdong coal ash are studied by the combination of experiment and simulation. The trend of melting temperature decreases firstly and rises with increasing Al2O3/CaO. The ash melting point reached to the lowest when the ratio is 1.23. XRD and Factsage software are used to analyze crystallization behavior of samples. The results show that the content of anorthite, albite and corundum increases and subsequently decreases, while the content of mullite decreases firstly and then rises with increasing Al2O3/CaO. High content with CaO can contribute to form albite and anorthite of low-melting. Besides, high content with Al2O3 can tend to produce mullite of high-melting. The results of experimental and simulation are basically the same, which lays a foundation for the melting characteristics of Ningdong coal ash and can provide technical support for the smooth operation of the entrained-gasifier.
    High adsorption of Cd (II) by modification of synthetic zeolites Y, A and mordenite with thiourea
    Shaoqing Zhang, Tianming Lv, Yang Mu, Jiqi Zheng, Changgong Meng
    2020, 28(12):  3117-3125.  doi:10.1016/j.cjche.2020.07.046
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    Zeolites Y, A and mordenite (ZY, ZA and ZM) were obtained from diatomite in a template-free system, and the products were modified by thiourea (TU). Characterization studies results indicated that the TU molecules were loaded onto the exterior surfaces of the synthetic zeolites as well as the channels. Elemental analysis and energy-dispersive X-ray spectrometer proved that the TU molecules loaded on to ZA were more than ZY and ZM. Removal of Cd(II) was investigated, and it was found that the modified zeolites have higher removal capacity, modified ZA is especially noticeable. In the adsorption experiments, the effects of various parameters such as sorbent content, contact time, concentration of cadmium solution, pH, selectivity and regeneration were discussed. At the best removal efficiency by modified zeolites, the maximum adsorption capacity is 94.3 mg·g-1, 103.2 mg·g-1 and 89.7 mg·g-1 at 25℃, respectively. The sorbents show good efficiency for the removal of Cd(II) in the presence of different multivalent cations and have good regeneration effect. For the modified samples, removal experiments take place via ion exchange and complexation processes.
    Large-scale laboratory study on the evolution law of temperature fields in the context of underground coal gasification
    Zhe Wang, Yongchao Wei, Tengfei Hou, Yongchuan Jin, Cuilan Wang, Jie Liang
    2020, 28(12):  3126-3135.  doi:10.1016/j.cjche.2020.07.005
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    This article presents the evolution law of temperature fields in a large-scale laboratory Underground Coal Gasification reactions using Ulanqab lignite under actual conditions. The results show that in the cultivation stage of oxidation zone, the main direction of the temperature field expansion is consistent with the crack direction of the coal seam. In the gasification stabilization stage, the main direction of the temperature field expansion is along the channel. The temperature of the coal seam and the overlying rock mass at its interface with the furnace directly above the gasification channel is equivalent to that of the coal seam temperature, and this temperature is much greater than the temperatures observed near both side walls of the gasification channel at the interface. However, temperatures perpendicular to the axis of the gasification channel are similar at a vertical distance of 40 cm away from the interface. The temperature distributions indicate that the transmission of heat through the overlying rock mass is more rapid in the vertical direction than in the horizontal direction. Moreover, some degree of thermal dispersion is observed in the vertical direction near the outlet. The thermal dispersion coefficient is 0.72 and dispersion angle γ is 78.7°.
    Materials and Product Engineering
    Promoted hydrolysis performances and mechanism of Si-NaBH4-AlCl3 in deionized water
    Zhao Feng, Chaoling Wu, Shuang Zhong, Yungui Chen, Hui Chen, Yao Wang
    2020, 28(12):  3136-3144.  doi:10.1016/j.cjche.2020.08.019
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    Si-based hydrolysis material system can be used in mobile/portable hydrogen source applications connected to fuel cells but is limited by alkaline solutions. In the present research, we reported an acid/alkaline free hydrolysis system combining silicon with NaBH4. Samples with different ratios between Si and NaBH4 are prepared via high energy ball milling and hydrolyzed in deionized water at different temperatures. Synergetic effect between silicon and NaBH4 was found in the hydrolysis process. 2Si-NaBH4 sample displays the best hydrolysis performances with the hydrogen yield of 1594 ml·g-1 in deionized water at 70℃. Thereafter, AlCl3 is added into the 2Si-NaBH4 sample to further improve its comprehensive properties. The effect of AlCl3 content and promotion mechanism of the reaction are explored. 2Si-NaBH4-5 wt% AlCl3 sample shows a significant improvement with a high hydrogen yield of 1689 ml·g-1 in deionized water at 70℃ and a corresponding conversion rate of 95.8%, indicating that the Si-NaBH4-AlCl3 composite is promising to be a hydrogen source in applications of mobile/portable fuelcell-powered facilities.
    Effect of the high-power electromagnetic pulses on the reactivity of the coal-water slurry in hot environment
    M. V. Belonogov, R. I. Taburchinov, R. I. Egorov
    2020, 28(12):  3145-3151.  doi:10.1016/j.cjche.2020.07.060
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    An effect of the high-power electromagnetic pulses onto the droplet of coal-water slurry inside the furnace was investigated. In contrary to the previously investigated laser-induced fuel atomization that occurs at the room temperature, the pre-heated (to 400 K) slurry becomes dry enough to prevent the explosion-like steam formation. Thus, fuel does not atomize and the ignition does not accelerate. Furthermore, the absorption of several laser pulses leads to evident sintering of irradiated surface with following increase of the ignition delay time for up to 24%. Variation of the pulse energy in range 48-118 mJ (corresponding intensity up to 2.4 J·cm-2) leads to certain variation of the increase of ignition delay. The strong pulsed overheating of the coal water slurry which does not initiate the fine atomization of the fuel generally makes its ignition longer.
    High permeability poly(vinylidene fluoride) ultrafiltration membrane doped with polydopamine modified TiO2 nanoparticles
    Qi Zhang, Zhaoliang Cui, Weixing Li
    2020, 28(12):  3152-3158.  doi:10.1016/j.cjche.2020.08.026
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    In order to improve the water permeability of poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes with low molecular weight cut-off (MWCO), polydopamine (PDA) was employed in the membrane preparation process. Owing to its merits of material-independent adhesion, PDA was coated on inorganic particles or added in coagulation bath to tailor the final membrane structure and property. The introduction of PDA broke through the permeability/selectivity trade-off of the PVDF membrane. By adding the PDA coated titanium dioxide (PDA/TiO2) nanoparticles, water flux increased by 287% while MWCO kept similar with the pristine PVDF membrane. Thermodynamics and Kinetics of the PVDF/additives/non-solvent were analyzed and shown that nanoparticles reduced the thermodynamic stability and increased the phase separation speed, and the speed can be adjusted using different nanoparticles. Additionally, X-ray diffraction (XRD) test indicated that PVDF crystalline form changed from α phase to β phase after adding different nanoparticles. Permeability/selectivity trade-off was broken through by DA addition in coagulation bath. Compared with the original PVDF membrane, when the DA concentration of the coagulation bath was 2.0 g·L-1, water flux increased by 312%, and MWCO of the PVDF membrane ranged in 10,000 to 20,000 Da as well as contact angle decreased from 81.4° to 45°.
    Erratum
    Erratum to “Immobilized laccase on magnetic nanoparticles for enhanced lignin model compounds degradation” [Chin. J. Chem. Eng. 28 (8) (2020) 2152-2159]
    Xinyan Chen, Bin He, Mi Feng, Dingwei Zhao, Jian Sun
    2020, 28(12):  3159-3159.  doi:10.1016/j.cjche.2020.10.004
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