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101.
A good performance of the solid‐liquid unit operation is required for the economical exploitation of the Bayer process. A computational fluid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of flocculated red mud particles, the feed flow rate and the radius of the feed well are critical parameters for the operation of the thickener. 相似文献
102.
103.
Lukas C. Buelens Vladimir V. Galvita Hilde Poelman Christophe Detavernier Guy B. Marin 《化学,工程师,技术》2016,88(11):1684-1692
The kinetics of redox reactions of iron oxide in oxygen carrier 50Fe2O3/MgAl2O4 are examined using different time‐resolved techniques. Reduction kinetics are studied by H2 temperature‐programmed reduction (H2‐TPR) monitored by time‐resolved in situ XRD. In contrast to conventional TPR, in situ XRD distinguishes the three‐stage reduction of Fe2O3 → Fe3O4 → FeO → Fe. It also shows that the oxidation of Fe → Fe3O4 by CO2 has no intermediate crystalline phases, explaining why its kinetics can easily be investigated by conventional CO2 temperature‐programmed oxidation (CO2‐TPO). A shrinking core model which takes into account solid state diffusion allows describing the experimental data. 相似文献
104.
Sandra C.K. De Schepper Geraldine J. Heynderickx Guy B. Marin 《American Institute of Chemical Engineers》2009,55(11):2773-2787
A coupled simulation of the flue gas and process gas side of the convection section of a steam cracker is performed, making use of the CFD software package Fluent. A detailed overview of the operating mode of the different heat exchangers suspended in the convection section is obtained. The asymmetric inlet flow field of the flue gas in the convection section, and the radiation from the convection section walls leads to large differences in outlet temperatures of the tubes located in the same row. The flow fields and temperature fields in the tubes of a single heat exchanger differ significantly with e.g., outlet temperatures of the hydrocarbon‐steam mixture ranging from 820 K to 852 K. Moreover, the simulations reveal the presence of hot spots on the lowest tube row, possibly causing fouling. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
105.
François Zaviska Patrick Drogui Jean-François Blais Guy Mercier 《Journal of Applied Electrochemistry》2009,39(12):2397-2408
This study examined the possibility to remove colour causing-compounds from synthetic effluent by indirect electrochemical
oxidation using iridium oxide anode electrodes. Using a high concentration of chloride ions (17.1 mM) and various current
densities, it was possible to produce high concentration of active chlorine with a specific production rate of 2.8 mg min−1 A−1. The best performance for acid methyl violet 2B dye (MV2B) decomposition was obtained using Ti/IrO2 anodes operated at a current density of 15 mA cm−2 during 40 min of treatment in the presence of 3.42 mM of chloride ions. Under these conditions, more than 99% of MV2B was
removed (with a reaction rate apparent constant of 0.20 min−1), whereas COD and TOC removal were 51% and 75%, respectively. The electrolytic cell was then used for the degradation of
three other synthetic dye solutions: Eosin yellowish (EOY), Trypan Blue (TRB), Acridine Orange (ACO). TRB was the most difficult
dye to remove from solution with a value reaction rate constant of 0.12 min−1, compared to 0.19 min−1 and 0.24 min−1 recorded for ACO and EOY dyes, respectively. More than 99% of these dyes were removed by electrochemical oxidation. 相似文献
106.
Pulp fibre suspensions display non-Newtonian rheology, including a yield stress. In mixing operations, this creates regions of active motion around the impellers with the cavern size affecting the quality of mixing attained. Due to the opacity of the suspensions, two non-invasive techniques were evaluated for determining cavern dimensions: electrical resistance tomography (ERT) and ultrasonic Doppler velocimetry (UDV), with ERT chosen for most tests due to the speed of data acquisition. Cavern volume as a function of impeller speed is reported for a range of mixing conditions (hardwood and softwood pulp, suspension mass concentrations from one to five percent, two impeller offsets from the wall, and three suspension height-to-chest diameter ratios). A scaled version of a commercial axial flow impeller was used in a standard side-entering configuration. Measured cavern diameters were compared against model predictions available in the literature. The discrepancy between experimental data and model predictions were significant and were attributed to interaction between the developing cavern and the vessel walls. An alternative model was developed for predicting cavern volume taking this interaction into account. 相似文献
107.
A method to simultaneously measure the moisture diffusion coefficient, Dθ, of unsaturated concrete, and the saturated concrete hydraulic conductivity, Kl, was developed for cylindrical specimens placed on a container filled with water that could be maintained at a given hydraulic pressure. Ordinary Portland cement Concrete (OPC) with a moderate and High Performance Concrete (HPC) with a low water to cement ratio were tested. The time dependent distribution of water content in the specimens was measured using a non-intrusive method based on gamma-ray attenuation. The measurements were conducted with varying hydraulic head (positive or null). Boltzmann's transformation was used to analyze the experimental results obtained at different hydraulic pressures and the difference between the null (or atmospheric) and positive pressure results is used to accurately determine Kl and also Dθ . This paper will present the results obtained using this original method, possible interpretations and future research. 相似文献
108.
109.
Steven Hostyn Gitte VanBaelen Guy L.F. Lemire Bert U.W. Maes 《Advanced Synthesis \u0026amp; Catalysis》2008,350(16):2653-2660
9H‐α‐Carbolines have been prepared via consecutive intermolecular Buchwald–Hartwig reaction and Pd‐catalyzed intramolecular direct arylation from commercially available 2,3‐dichloropyridines and substituted anilines. The combination of a high reaction temperature (180 °C) and the use of DBU were found to be crucial for the intramolecular direct arylation reactions of the 3‐chloro‐N‐phenylpyridin‐2‐amines as no reaction was observed at 120 °C and 180 °C using different inorganic and other organic bases. On the other hand, nitrogen‐methylated pyridine analogues of these substrates {N‐[3‐chloro‐1‐methylpyridin‐2(1H)‐ylidene]anilines} do undergo ring closure at 120 °C, with K3PO4 as base, affording the respective 1‐methyl‐1H‐α‐carbolines in good yields. 相似文献
110.
Elnaz Shahbazali Emilie M. F. Billaud Arash Sarhangi Fard Jan Meuldijk Guy Bormans Timothy Noel Volker Hessel 《American Institute of Chemical Engineers》2021,67(1):e17067
Liquid-phase adsorption has hardly been established in micro-flow, although this constitutes an industrially vital method for product separation. A micro-flow UV-photo isomerization process converts cis-cyclooctene partly into trans-cyclooctene, leaving an isomeric mixture. Trans-cyclooctene adsorption and thus separation was achieved in a fixed-bed micro-flow reactor, packed with AgNO3/SiO2 powder, while the cis-isomer stays in the flow. The closed-loop recycling-flow has been presented as systemic approach to enrich the trans-cyclooctene from its cis-isomer. In-flow adsorption in recycling-mode has hardly been reported so that a full theoretical study has been conducted. This insight is used to evaluate three process design options to reach an optimum yield of trans-cyclooctene. These differ firstly in the variation of the individual residence times in the reactor and separator, the additional process option of refreshing the adsorption column under use, and the periodicity of the recycle flow. 相似文献