Canadian Journal of Chemical Engineering
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The relative exergy array—a new measure for interactions in process design and control Abstract In this paper, we present the relative exergy array (REA), a tool to measure the relative exergetic efficiency and the controllability of a process when a proposed process and control structure is postulated. The REA is a means to compare thermodynamic efficiency for control structures of multi input–multi output processes. Although only steady‐state information is employed, it is a tool for quick comparison between several candidate process control structures. Guidelines for interpreting the results obtained from the REA are presented and explained. A case study of dual composition control of a distillation column is presented and the results discussed. Une bonne compréhension de tous les domaines du génie chimique ainsi que de nombreux aspects sont nécessaires afin de concevoir efficacement un processus chimique. Par exemple, les organismes gouvernementaux exigent que tous les secteurs d'activité respectent certaines règles en matière d'impact environnemental. L'ingénieur chimiste chargé de concevoir un processus doit prendre ces règles en compte tout en essayant de créer le meilleur processus possible afin d'optimiser les bénéfices. L'exergie peut servir à mesurer la qualité d'un système, notamment en matière d'efficacité du processus. Un processus présente une efficacité thermodynamique élevée et est par conséquent rentable et écoefficace si les valeurs exergétiques des produits issus d'un processus sont proches des valeurs des matières premières. Dans ce document, nous présentons un nouvel outil, le tableau d'exergie relative (TER) permettant de mesurer l'efficacité exergétique relative ainsi que la contrôlabilité d'un processus lorsqu'un processus et une structure de contrôle sont proposés. Le tableau d'exergie relative permet de comparer l'efficacité thermodynamique des structures de contrôle de processus à entrées multiples et sorties multiples. Bien que l'on utilise uniquement l'information de fonctionnement normal, il s'agit d'un outil utile pour comparer rapidement plusieurs structures de contrôle de processus proposées. Ce document présente et explique des directives générales d'interprétation des résultats obtenus grâce au TER. Une étude de cas d'une double structure de contrôle d'une colonne de distillation est également présentée et les résultats sont commentés. © 2010 Canadian Society for Chemical Engineering
Canadian Journal of Chemical Engineering - Tập 89 Số 3 - Trang 545-549 - 2011
Pd catalyst supported on ZrO<sub>2</sub>‐Al<sub>2</sub>O<sub>3</sub> by double‐solvent method for methane oxidation under lean conditions Abstract The Pd catalyst supported on the Zr0.5 Al0.5 O1.75 composite material was prepared by the conventional impregnation and double solvent impregnation method. The effects of preparation method on the catalytic properties of the Pd/Zr0.5 Al0.5 O1.75 catalyst for methane combustion have been investigated systematically. The measurement was evaluated in a multiple fixed‐bed continuous flow micro‐reactor by passing a gas mixture simulating the exhaust emissions from lean‐burn natural gas vehicles. The as‐prepared catalysts were characterized by CO chemical adsorption, transmission electron microscopy (TEM), hydrogen‐temperature programmed reduction (H2 ‐TPR),and X‐ray photoelectron spectroscopy (XPS) measurements. The results of TEM and CO chemisorption showed that the introduction of double solvent during the preparation of Pd/Zr0.5 Al0.5 O1.75 was beneficial for the dispersion of Pd nanoparticles and obtained superior resistance to the sintering of Pd on the surface of Zr0.5 Al0.5 O1.75 . The H2 ‐TPR measurements demonstrated that the double solvent method increased the reducibility of the Pd catalyst. The XPS results further indicated that more active surface oxygen species also can be formed on the catalyst prepared via double solvent process. Thus, this catalyst exhibited better catalytic performance and hydrothermal aging resistance in the methane oxidation compared to its analogues with the same Pd content prepared by the conventional impregnation method.
Canadian Journal of Chemical Engineering - Tập 95 Số 6 - Trang 1117-1123 - 2017
Further studies on momentum dissipation of grid jets in a gas fluidized bed Abstract Four experimental aspects of momentum dissipation of grid jets in a gas fluidized bed of cracking catalyst are reported. First, an investigation was made into the radial distribution of axial momentum for air jets issuing from vertical long nozzles into a minimally fluidized bed. The theory of Abramovich was compared with these experimental results. Second, data on the distribution of axial momentum along the axis for vertical air jets issuing from single and multi‐hole grids were compared with previous work. Third, the axial dissipation of vertical air jets loaded with fluid cracking catalyst issuing into air and also into a fluid bed was studied. Finally, the shape of the boundary of a jet dissipating into a fluid bed was compared to that given by theory.
Canadian Journal of Chemical Engineering - Tập 49 Số 5 - Trang 557-561 - 1971
A continuous process for recovery of sulfur from natural gas containing low concentrations of hydrogen sulfide Abstract A continuous catalytic process was developed to remove hydrogen sulfide from a natural gas stream using activated carbon as catalyst. The concentration range of hydrogen sulfide in the gas stream studied was 300–3000 ppmv (0.0126–0.126 moles/m3 ). Virtually 100 percent conversion of hydrogen sulfide was achieved by the combination of various parameters. The “field gas” employed in this study exhibited cracking of some heavier hydrocarbons and made the product sulfur slightly brown. These hydrocarbons should therefore be separated from the gas stream prior to the oxidation reaction. No carbon monoxide or carbon dioxide was produced during the oxidation of hydrogen sulfide. It is concluded that the process described herein has the potential for the removal of hydrogen sulfide as sulfur from a sour natural gas stream on a continuous basis and could therefore eliminate an environmental problem which now exists.
Canadian Journal of Chemical Engineering - Tập 64 Số 6 - Trang 960-968 - 1986
A study of the heat transfer characteristics of novel Ni‐foam structured catalysts Highly exothermic reactions require catalyst beds with good heat transfer characteristics. Novel Ni‐foam structured catalysts have significant heat transfer efficiency compared with traditional packed beds, which is very suitable for the highly exothermic methanation reaction. The present work reports an experimental study of steady‐state heat transfer behaviour of a gas flowing through a fixed bed packed with Ni‐foam structured catalyst under various operation conditions. Experiments were carried out in a dedicated tubular reactor with inlet air temperature ranging from 160 to 200 °C, heating pipe temperature inside the fixed bed ranging from 400 to 500 °C, and air flow rate ranging from 4.0 to 6.0 Nm3 /h. Effective radial conductivity (λer ) and wall heat transfer coefficient (αw ) were derived based on the steady‐state measurements and the two‐dimensional pseudo‐homogeneous heat transfer model. The estimated values of λer and αw were between 2.17 and 3.34 W/m · K and 170 to 250 W/m2 · K respectively. Heat transfer properties of Ni‐foam structured catalyst are prominent compared with conventional packed bed. From the results it was found that the metal matrix and porous structure of the catalyst enhanced heat transfer. We anticipate that our research will open a new opportunity for design of new‐generation SNG process.
Canadian Journal of Chemical Engineering - Tập 94 Số 11 - Trang 2225-2234 - 2016
Modelling Vapour − Liquid Equilibrium of CO2 in Aqueous N-Methyldiethanolamine through the Simulated Annealing Algorithm
Canadian Journal of Chemical Engineering - Tập 83 Số 2 - Trang 344-353
Kinetic modelling of the pyrolysis of biomass and biomass components Abstract The kinetics of the pyrolysis of lignocellulosic materials was studied with a view of providing simple kinetic models for engineering purposes. Experimental data obtained by means of thermal analysis techniques suggest that the pyrolysis of fine particles (below 1 mm) can be considered to be controlled by pyrolysis kinetics. The rate of pyrolysis of one biomass type can be represented by the sum of the corresponding rates of the main biomass components (cellulose, lignin, hemicellulose). The kinetics of each of these components was simulated by a kinetic scheme capable of predicting the pyrolysis rate and the final weight‐loss for a wide range of pyrolysis parameters including various heating conditions.
Canadian Journal of Chemical Engineering - Tập 67 Số 1 - Trang 75-84 - 1989
The role of gas phase momentum in determining gas holdup and hydrodynamic flow regimes in bubble column operations Abstract Experiments conducted in 0.15 m diameter bubble columns using water and non‐aqueous liquids have shown that the gas velocity at which transition from the bubbly flow to the churn‐turbulent flow regime occurs is a function of gas density. The transition velocity increased with increasing gas density. The direct effect of gas density on gas holdup in the bubbly flow regime is small with only a slight increase in holdup being observed at higher densities (ϵG α ρg 0.04 ). In the churnturbulent region a much greater effect of gas density on gas holdup was observed. These differences were found to be a direct function of the differences in holdup values at the transition points. Gas holdup was found to be a function of the gas phase momentum. In the bubbly flow regime holdup was directly proportional to momentum while in the churn‐turbulent regime holdup was proportional to momentum to the one third power. Reasons for this behaviour are discussed, as well as the implied effects on liquid mixing in bubble column slurry reactors. The effects of gas density may offer an explanation for some apparently anomalous published results.
Canadian Journal of Chemical Engineering - Tập 72 Số 1 - Trang 3-12 - 1994
Neural network based objective flow regime identification in air‐water two phase flow Abstract The Kohonen self‐organising neural network was applied to identify flow regimes in horizontal air‐water flow. The neural network was trained with stochastic features derived from turbulent absolute pressure signals obtained across a range of flow regimes. The feature map succeeded in classifying samples into distinctive flow regime classes consistent with the visual flow regime observation.
Canadian Journal of Chemical Engineering - Tập 72 Số 3 - Trang 440-445 - 1994
Prediction of gas hold‐up in a bubble column filled with pure and binary liquids Abstract A dimensionless correlation for gas hold‐up in a bubble column filled with pure liquids and binary mixtures has been developed. The criteria of bubble coalescence in pure liquids and foamability of binary mixtures have been included successfully in the proposed correlation. For the first time, comprehensive data of gas hold‐up with respect to concentration in four binary systems are presented. The often‐reported enhancement of gas hold‐up in aqueous alcohol mixtures has been observed experimentally. The proposed correlation is able to predict successfully the trend of gas hold‐up enhancement with respect to concentration. The estimated values are found to be within 7% of the measured values.
Canadian Journal of Chemical Engineering - Tập 80 Số 1 - Trang 44-50 - 2002
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