查看更多>>摘要：Scheduling over longer time horizons has limitations such as large problem size and com-putational complexity. Therefore, there is universal concern to establish novel modeling approaches to efficiently manage various complex characteristics. In this work, a rigorous Unit Specific Event Based model (USEB) is proposed for long-term scheduling of batch plants. The proposed approach addresses the complete scheduling of long-term operational hori-zon by considering start-up, cycle and finishing periods. The start-up period takes care of intermediate material states requirement at the beginning of first cycle and finishing period effectively utilizes the leftover intermediate states in final cycle. Using active task con-cept, the cyclic scheduling, direct and indirect heat integration possibilities are accurately modelled by considering design of heat storage vessels. This comprehensive computational approach highlights the importance of judicious use of direct and indirect heat integration in process industries and cyclic scheduling for complex and long term scheduling problems.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：The slow time-varying fouling accumulation is the biggest obstacle to the full-cycle operation of the multi-effect evaporation with thermal vapor compression (MEE-TVC) desalination system. In order to avoid the impact of increased fouling resistance in fresh water production, the heat transfer area is generally oversized during design, but the utilization of redundant heat transfer area is unreasonable. The analysis has found that the reduction of feed seawater flow rate in the MEE-TVC system will increase the required heat transfer area for normal production, but will also reduce the external motive steam consumption. Based on this, a margin slow released full-cycle optimization method is proposed. This method continuously adjusts the operating conditions to adapt to the state changes of the MEE-TVC system, which not only makes full use of the redundant heat transfer area, but also reduces the full-cycle energy consumption. Furthermore, it also avoids the rapid exhaustion of the motive steam margin, so that the operating performance of the system is always better than that under the design condition during the full cycle.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：Since PMDA-ODA polyimide is insoluble, its soluble precursor PMDA-ODA poly (amic acid) (PAA) is used to prepare hollow fiber membranes (HFMs). Due to the existence of -CO-NH- and -COOH groups, PAA is subject to form hydrogen bonds with water and consequently leads to a very slow phase inversion rate during the non-solvent induced phase inversion process. Therefore, the hollow fiber spinning has to be carried out with a low take-up speed that limits the productivity. In this paper, we increased the take-up speed of PAA hollow fiber to 60 m/min by simply adding LiCl into polymer dope. Moreover, an integrally skinned defectfree PMDA-ODA hollow fiber membrane was obtained at the high take-up speed where the gas permeances were 6.8 +/- 0.7, 2.2 +/- 0.2, 0.4 +/- 0.04 and 0.07 +/- 0.01 GPU for H-2, CO2, O-2 and N-2, respectively, with an ideal selectivity of 3.1 +/- 0.3, 31 +/- 3.0 and 5.7 +/- 0.6 for H-2/CO2, CO2/N-2 and O-2/N-2, respectively. These results indicated a dense PMDA-ODA layer of 1 mu m. To our best knowledge, this is the first time that a defect-free hollow fiber membrane for gas separation is prepared based on PMDA-ODA. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Taleghani, M. SalehiTabrizi, N. SalmanSangpour, P.
13页
查看更多>>摘要：Titanium dioxide is a widely used material as a photocatalyst. However, the wide bandgap and limitation of use at high concentrations of pollutants have impeded its widespread use. In this study, a novel aerogel of carbon-titanium dioxide hybrid strengthened by multi-walled carbon nanotubes was synthesized for photocatalytic degradation of organic pollutants from aqueous solutions under sunlight. TiO2 nanocrystals (about 9 nm in size) were synthesized by sol-gel method using TiCl4 as the precursor in sulfuric acid solution and the formed anatase phase was identified by XRD analysis. For characterization of the TiO2- CNT-C hybrid aerogels, various techniques like FESEM, EDS, XRD, BJH, BET, DRS and FTIR were utilized. The specific surface areas of the samples were between 410 and 480 m(2) g(-1). The DRS results showed a decrease in the band gap of the TiO2 hybrid aerogel (1.9 eV) relative to that of pure TiO2 (3.1 eV). To investigate the photocatalytic removal efficiency, methylene blue was used as a contaminant model. Photocatalytic experiments under Xenon lamp were performed with 20 mg photocatalyst in 100 ml of 50 ppm methylene blue solution. 6 samples (CAT-1, CAT-2, CXT, CA, TiO2, P25) were used to investigate the photocatalytic degradation activity. The highest removal efficiency was 95.50% and the kinetic studies revealed that the photocatalysts containing carbon aerogels followed the second-order kinetic model and the other samples followed the first-order kinetic model. The highest adsorption capacity was 238.756 mg g(-1) and the lowest was 133.754 mg g(-1). Adsorption-degradation mechanism was also speculated.& nbsp;(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：The aim of this work was to obtain decay kinetic parameters for bacteria sedimentation-resuspension in water. For that, synthetic water matrices prepared with four particle sizes at 2.5 and 5 g/l, were spiked with Escherichia coli and Enterococcus faecalis, selected as Gram-negative and-positive models, respectively. Matrices with bacteria without solids were used as controls. Turbidity was measured and culturable bacteria decay was evaluated using membrane filtration over time. Also, the persistence of culturable E. faecalis and its DNA (detected by real-time PCR) was compared. When no colonies were detected, water matrices were mixed to re-suspend sediments and surface samples were collected and analysed. Spearman test was applied to find correlation between bacteria and turbidity. A persistence coefficient (PC) was defined and several kinetic parameters (decay rate constants, R-2, T-90) were calculated from experimental data. While culturable E. coli disappeared from the surface of all water matrices with turbidity (p < 0.05), E. faecalis only showed strong and positive correlation in matrices with higher turbidity and smaller particles. E. coli decayed slower when interacting with smallest solids (< 44 mu m) than with the largest ones (> 149 mu m), being T90 3-4 times higher in the former. Also, it reappeared and persisted in the surface of all matrices after resuspension despite solid concentration (PC: 0.5-0.9). Instead, culturable E. faecalis, persisted less (lower PC values) in matrices with 2.5 g/l than with 5 g/l and no logic relation was observed for any rate constant with particle size. E. faecalis DNA remained in suspension for longer periods until the end of the experience as seen through their lower rate constants (k(DNA) < 0.05 h(-1)). Accurate decay kinetic parameters, like the ones obtained here, are crucial for modelling the fate and transport of bacteria in water and to perform a robust and realistic quantitative risk assessment. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：An original one dimensional population balance model (PBM)-based model of liquid-liquid extraction columns is reported. Compared to existing simulators, ColHySE implements a more realistic description of the flow patterns in the contactor, and predicts its effect on the local droplet-droplet interactions (i.e. breakage and coalescence rates). Proper turbulent properties, extracted from single-phase flow CFD simulations, are used in the source terms of the PBM to evaluate locally the inhomogeneous breakage and coalescence rates, using the averaged Coulaloglou and Tavlarides kernels (Castellano et al., 2018). The sensitivity of the predicted droplets mean diameter, d(32), and the holdup, phi, to the parameters of the used empirical and phenomenological models, on the one hand, and to the operating conditions of the column, on the other hand, was studied. Although some model parts must be refined, and an experimental validation remains necessary, the results confirm that the 1D-PBM methodology used in ColHySE is relevant for predicting the interfacial area in the pulsed column as a function of the operating conditions and geometry, hence highlighting its relevance to study the hydrodynamic stability and tendency to flooding. The sensitivity analysis has moreover highlighted the needs for an improved slip velocity model. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：In this research, we use two different approaches to distinguishing the interaction regimes of liquid droplets in a gas environment. The first one distinguishes the following regimes: coalescence (parent droplets merge), bounce (parent droplets approach each other and then move away from each other), separation (impact produces two new droplets of a similar size as the initial ones), and disruption (two initial droplets break up into more than two fragments). The second approach distinguishes the following regimes: coalescence (merging of initial fragments), bounce (merging and consecutive splitting into two fragments of similar size as the initial ones), stretching separation (fragmentation due to the stretching of the merged droplet), and reflexive separation (fragmentation due to the tendency of each fragment to take spherical shape). Experimental results for different slurries, emulsions, solutions, and single-component compositions allowed us to distinguish transition boundaries of collision regimes using the Weber and Ohnesorge number, as well as angular and linear interaction parameters. Mathematical expressions are obtained for the boundaries, describing the variation ranges of droplet interaction parameters as well as their properties required for the consistent transition from one collision regime to another. The expressions are second order polynomials with droplet size ratio, Weber number, Ohnesorge number, and interaction parameters as variables. A database of empirical coefficients is obtained for general mathematical expressions that can be used to predict the transition boundaries of droplet collision regimes. Any of the two approaches to distinguishing the regimes is equally viable for this matter.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：A B S T R A C T Three-dimensional porous sodium alginate/gellan gum aerogels (SAG aerogels) were pre -pared by the method of freeze-drying and ion cross-linking for the removal of methylene blue (MB) in wastewater. The physical morphology and chemical structure of the SAG aero-gels were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results revealed that the addition of gellan gum (GG) formed interpenetrating double network structures by ion cross-linking and hydrogen bonding interaction with sodium alginate (SA), which improved the chemical resistance of SAG aerogels and the adsorption capacity of aerogel for MB at a mass ratio of 3:1. The pseudo-second-order kinetic model and Langmuir isothermal model could be used to describe the adsorption process of MB, and the maximum adsorption capac-ity of the SAG aerogel for MB was 1456.45 mg/g, at 313 K. The adsorption thermodynamic analysis results showed that the adsorption process of MB was spontaneous and exothermic. After 5 adsorption-desorption cycles, the adsorption capacity of SAG aerogel only decreased 1.44% compared with their initial adsorption capacity. The obtained results indicated that the SAG aerogels could be successful and effective used to remove the MB in wastewater.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：The pulsed disc-doughnut column is used in various industrial applications. Knowing size distributions of the dispersed phase droplets through this column is necessary to management decisions for better extraction efficiency. To address this, we used various operational parameters, traditional sampling, characterizations, and maximum entropy modeling, and population balance equations to propose species distribution models for the size of droplets in the extraction zone. This paper is devoted studying the size distribution of the dispersed phase using three various liquid feeds in the absence of mass transfer at three operating variables, including the pulse intensity (Af) and flow rates of both liquid phases. The new correlations are proposed to describe Lagrange multipliers of the maximum entropy model regarding operating factors and the physical properties of phases. The population balance model was used to describe the distribution of droplets with main parameters in the breakage and coalescence functions. The comparison appears excellent agreement between these models and the experimental data. The maximum entropy principle has been a straightforward strategy that has successfully described droplet sizes.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
查看更多>>摘要：Improving the water permeance of polyamide nanofiltration (NF) membranes without the simultaneous loss of rejection is highly desired but remains a challenge. In this work, we prepared an ultrapermeable polyamide NF membrane containing an in-situ-formed cellulose nanofibre (CN) interconnected network film between a polyamide active layer and ultrafiltration (UF) membrane support through direct addition of the CN to a piperazine aqueous solution for interfacial polymerization. Such in-situ-formed CN interlayer with high porosity can provide a large number of channels for water transport. Compared with the polyamide active layer directly supported by the UF support, the polyamide active layer supported by the CN interlayer can contribute a more effective area for water permeation. Consequently, the polyamide NF membrane exhibited a pure water permeance up to 35.7 L m(-2) h(-1) bar(-1) while maintaining salt rejection to Na2SO4 of > 97%. This permeance is 2.5 times greater than that of the membrane without the CN interlayer. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
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