查看更多>>摘要：Experimental flow visualizations and velocity measurements are used jointly with numerical simulations to investigate the mixing and monitor the reaction progress in the periodic flow regimes occurring in a T-shaped microreactor. We considered the effects of different kinetic constants, with very different characteristic chemical time scales resulting in a wide range of Damkohler numbers. A remarkable agreement between experiments and simulations is found both in terms of flow pattern and reaction progress. Two different flow regimes are present for increasing Reynolds number. The first is the periodic asymmetric regime, characterized by the shedding of vorticity-blobs along the mixing channel leading to a further increase of the mixing performance compared to the steady engulfment regime. The second regime is the periodic asymmetric one, which is mainly a poorly mixed segregated regime with periodic oscillation at the interface between the two reactants. The mixing degree significantly increases in the unsteady asymmetric regime, whereas it predictably drops down in the unsteady symmetric regime. In the periodic asymmetric regime the reaction yield follows the same function of the Damkohler number, describing the residence to chemical time-scale ratio, and of a non-dimensional kinetic constant, taking into account also fluid properties, previously proposed for the steady vortex and engulfment regimes. In the periodic symmetric regime, the reaction yield is found to depend only on the Damkohler number, with the same dependence previously highlighted for the steady segregated regime. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Keller, A.Sterner, P. L.Hlawitschka, M. W.Bart, H. -J....
11页
查看更多>>摘要：The separation of manganese from cobalt sulfate solutions is crucial in the field of spent lithium-ion battery recycling. A membrane-based microreactor is used to reveal required mass transfer characteristics as is diffusion and chemical reaction. The dependence of di(2-ethylhexyl)phosphoric acid (D2EHPA) concentration, pH, and metal ion concentration on the extraction efficiency are investigated. A back-reaction term is introduced giving a significant influence on the effective extraction rate even at small metal complex concentrations as initial extraction rates proved to be inaccurate to describe the system. It is shown that the extraction of manganese at a pH of 3.0 is mainly diffusive while the cobalt extraction is strongly kinetically controlled. At a separating pH of 3.9 a good agreement between the model and experimental data is only given if the equilibrium back-extraction rate is considered (deviation less than 5%).(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).
查看更多>>摘要：In recent years, many efforts have been made to develop new membrane materials for natural gas sweetening (CO2/CH4) and post-combustion CO2 capture from flue gas (CO2/N-2), especially in coal-fired and natural gas-fired power plants. This study focused on the effect of polyurethane and nano-clay on structure and CO2 separating properties of polyethersulfone (PES) based three-component mixed matrix membranes (MMMs). The different weight fractions polyurethane (PU) (5-30 wt.%) together with clay nano-sheets (Cloisite (R) 15A) (0.5-10 wt.%) were blended to fabricate a novel PES-based ternary MMMs. The principal purpose was to investigate the effect of loading PU polymer and layered clay particles with 2D channels on the gas separation performance of the PES membranes. Pure gas permeability for N-2, CH4, and CO2, and ideal gas separation for CO2/N-2 and CO2/CH4 mixtures were examined through neat PES and modified PES membranes. By incorporating 20 wt.% of PU into PES, the permeability of CO2 and selectivities of CO2/N-2 and CO2/CH4 were improved by 4, 1.4, and 1.7 times higher than the neat PES membrane, while by loading 20 wt.% of PU and 2 wt.% of nano-clay, the CO2 permeability, and CO2/N-2, and CO2/CH4 selectivities were improved by 7.8, 1.8, and 2.2 times higher than the neat membrane, respectively. In general, PU and clay nano-sheets together as a filler into the PES matrix exhibited a meaningful improvement in the gas permeation and separation properties of PES and can be admitted as a worthy membrane for CO2 separation from the flue gas and natural gas. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：In this study, we propose a novel optimization method for designing and operating various types of biomass-based renewable hydrogen production systems. To this end, we considered the coupling of multiple biomass hybrid utilization processes for hydrogen production. First, we calculated and evaluated the biomass utilization potential of a given area. Second, we predicted the biomass gasification products using chemical reaction kinetics and thermodynamic models. Finally, we determined the optimal annual total cost of the hydrogen production supply chain by optimizing the microscopic operation of the biomass gasification plant. Through the proposed method, it is possible to effectively conduct a comprehensive assessment of regional biomass material hydrogen production; moreover, the optimal design of the biomass hydrogen production supply chain can also be determined based on the availability of biomass and hydrogen demand. More precisely, the logistics operations under fluctuating demand conditions were realized, enabling strategic decision-making for planning a biomass hydrogen production system. To validate the model, a case study analysis of biomass hydrogen production, to be launched in Sichuan Province, China, is presented.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Coimbra, Jamille C.Martins, Marcio A.Minim, Luis A.
10页
查看更多>>摘要：A B S T R A C T Cryogel-based chromatographic supports have a wide application in the bioseparation field due to the versatility of synthesis and functionalization. This study proposes a simplification of classical models applied to cryogel beds that analyze many geometrical and structural properties at the channel level (thickness, tortuosity, diameter distribution, monoliths number, etc.) resulting in an over-parameterized formulation. The proposed modeling allowed for simplified calculations and reduced parameterization by not establishing the microstructural morphology of the cryogel. Using homogeneous modeling in which the porous medium is continuous, we obtained fast-solving simulations with reduced computational requirements that can be used for real-time control system. Initially, a polyacrylamide cryogel was produced and characterized in terms of morphological structure, fluid dynamic behavior and mass transport. Next, breakthrough curves predicted by Computational Fluid Dynamics (CFD) simulations were compared with experimental data. The applicability of the modeling approach was extended to a new data set obtained from the literature under different operational conditions for complete model validation. The modeling approach represented the experimental data very well, presenting viable descriptions of protein bioseparation.(c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：Waste tires are well known to have appropriate disposal or reprocessing problems under environmental and economically sustainable conditions. The pyrolysis represents valid modern technology to process waste tires to recover fuels and carbon black. However, the detailed degradation mechanism and kinetics of waste tire pyrolysis have not been thoroughly studied. In this work, pyrolysis of tread, sidewall and, innerliner of a waste tire of a light motor vehicle is thermogravimetrically investigated. The degradation profiles of said sections of waste tire predicted using various kinetic models. Kinetic models constituting a single reaction to four parallel reactions are considered for the stated purpose. The results reveal that the degradation profiles of tire sections are different from that of the whole tire. Among the kinetic models considered, the four reactions model predicts degradation for tread and sidewall sections with a fit percentage of over 98% with experimental data. The average activation energy of tread and sidewall obtained at this fit are 80.82 kJ mol-1 and 79.99 kJ mol-1, respectively. In comparison, the degradation behavior of the innerliner section is very well predicted using a three reactions model with a fit percentage of over 99% to experimental data. The average activation energy (E) estimated for highest fit is 53.78 kJ mol-1 for innerliner section.(c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Alhajeri, Mohammed S.Luo, JunweiWu, ZheChristofides, Panagiotis D....
13页
查看更多>>摘要：Recurrent neural networks (RNN) have demonstrated their ability in providing a remarkably accurate modeling approximation to describe the dynamic evolution of complex, nonlinear chemical processes in several applications. Although conventional fully-connected RNN models have been successfully utilized in model predictive control (MPC) to regulate chemical processes with desired approximation accuracy, the development of RNN models in terms of model structure can be further improved by incorporating physical knowledge to achieve better accuracy and computational efficiency. This work investigates the performance of MPC based on two different RNN structures. Specifically, a fully-connected RNN model, and a partially-connected RNN model developed using a prior physical knowledge, are considered. This study uses an example of a large-scale complex chemical process simulated by Aspen Plus Dynamics to demonstrate improvements in the RNN model and an RNN-based MPC performance, when the prior knowledge of the process is taken into account.(c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Mana, Shareena Fairuz AbdulLuthfi, Abdullah Amru InderaJahim, Jamaliah MdHarun, Shuhaida...
17页
查看更多>>摘要：Acid hydrolysis pre-treatment on biomass produces furan derivatives, phenolics, and organic acids, which are harmful to the fermenting microorganisms. Removal of inhibitor compounds from the hydrolysate using coconut shell activated charcoal (CSAC) adsorption is essential to improve the quality of detoxified hydrolysate as a feedstock for xylitol production. This study investigated adsorption parameters of different pH (pH 1-7), temperature (17.5-92.5 ?), CSAC-to-hydrolysate loading (0.5-9.5% (w/v)) and contact time (30-142.5 min) using a central composite design (CCD) to evaluate the interactive effect of the adsorption process parameters on response variables. Under optimal adsorption process (pH 2.5, 55.6 ?, 5.3% (w/v) and 74 min), the results demonstrated loss of 10.4% sugar and 12.8 % of detoxified hydrolysate volume with 79.9% of furfural removal. Inhibition by acetic acid could be alleviated by pH control in bioreactor since the concentration of acetic acid was decreased by up to 73.7% at the end of OPF hydrolysate fermentation. The fermentability test using detoxified OPF hydrolysate by Kluyveromyces marxianus ATCC 36907 demonstrated 78% higher xylitol production compared to non-detoxified OPF hydrolysate. This finding corroborates that this sequential detoxification is a promising method to enhance the xylitol production using OPF hydrolysate.& nbsp;(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：Sulfur compounds in transportation fuels upon burning lead to serious environmental pollution and hence their immediate removal from fuel oils requires urgent attention. Herein, we report the catalytic oxidative desulfurization (ODS) of model and real petroleum distillates using sodium hypochlorite (NaClO) as oxidant over Cu and Ni (1 wt.% each) loaded activated carbon (AC) (derived from banana peels) via carbonization followed by thermal activation. The fresh and post-reaction catalysts were characterized by FTIR, SEM, EDX and BET surface area analyses. Catalytic ODS experiments revealed that at O/S molar ratio of 1:6 and 0.2 g catalyst dosage, a net DBT conversion of 93% within 10 min and 30 ?degrees C was achieved by Ni/AC-NaClO catalyst oxidant system. The overall ODS catalytic activity order for different catalysts was: Ni/AC > Cu/AC > AC, while in addition to outstanding performance, Ni/AC catalyst exhibited intriguing stability and recycling performance for five successive reuses. In addition, under the optimized experimental conditions, Ni/AC-NaClO system showed 83%, 90% and 87% total sulfur removal from gasoline, kerosene and diesel oils respectively, outclassing some state-of-the-art catalysts reported. This fascinating performance of Ni/AC-NaClO system was mainly attributed to the presence of super-strong oxidizing species of hypochlorite (OCl-) generated from the dissociation of NaClO over the catalyst surface. These findings credit the newly designed, highly cost-effective and efficient Ni/AC-NaClO catalyst-oxidant system as a promising contender for the desulfurization of petroleum distillates on industrial level.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Mahmoudi, SadraHemmatian, FarshidDahkaee, Kaveh PadashtHlawitschka, Mark W....
11页
查看更多>>摘要：A study of the effects of fluid type (shear-thinning, Newtonian, and shear-thickening) and periodic shape fluctuations of bubbles on the drag coefficient is presented for three bubble sizes (2 mm, 4 mm and 6 mm), three flow consistency indexes (mu(water), 10 mu(water), 100 mu(water)) and three flow behavior indexes (0.8, 1, 1.2). Computational Fluid Dynamics (CFD) simulations were performed in addition to previous measurements to obtain local data of the flow hydrodynamics. The results were used to evaluate 12 different drag coefficient estimation models, which are essential for the design of bubble columns. The Dijkhuizen et al. and Rodrigue correlations are suitable for the prediction of terminal velocity in both Newtonian and non-Newtonian liquids with high or intermediate viscosity. Finally, a modification of the correlations enables the prediction of small bubble terminal velocity also in low-viscosity liquids. (c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).
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