共查询到20条相似文献,搜索用时 15 毫秒
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D. M. F. Prazeres 《加拿大化工杂志》1995,73(6):931-934
Exact analytical expressions are derived for the optimal design (minimum overall reaction volume) of N perfectly mixed membrane reactors in series carrying out an enzyme catalysed reaction with Michaelis-Menten kinetics. These equations enable the direct calculation of the smallest total reactor volume (holding time) needed for a given overall conversion degree, as well as the individual reactor volume and conversion degrees. Results are compared with the ones obtained with a series of N CSTRs and with a plug flow reactor. The theoretical superiority of membrane reactors versus CSTRs is demonstrated. 相似文献
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The published data in the literature and the reported models on foam-bed reactors have been reanalyzed. It is observed that the models have been developed assuming negligible conversion in the storage section although the storage constitutes 65–85% of the total volume of liquid/slurry charged into the reactor. For confirmation of the reported information, in the present work, experiments have been performed in foam-bed and bubble column slurry reactors for carbonation of hydrated lime slurry using carbon-dioxide gas under identical conditions. A comparison of the relative performances of the two reactors has been made. Storage section is found to be the main section governing the performance of the foam-bed slurry reactor. New mathematical models have been developed for both the reactors. The model predictions agree well with the experimental data. 相似文献
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Amit Varshney 《Chemical engineering science》2003,58(15):3413-3424
A mathematical model for oxidation of aqueous alkaline solution of sodium dithionite using air as an oxidizing medium in a foam-bed reactor has been developed under pseudo-zero-order conditions of reaction and was found to be in good agreement with the experiments. Reactor conditions were 30°C at atmospheric pressure and surfactant used in the foam contactor was octyl phenoxy polyethoxyethanol (Triton X-100). The results of simulation for concentration profiles of the dissolved gas-phase reactant inside foam film based on above model are presented for different gas flow rates, reaction rates, and times of contact. The effects of variables such as superficial gas velocity and initial liquid-phase reactant concentration on conversion are also studied and compared with experiments on oxidation of sodium dithionite. The results indicate that the conversion increases with the increase in the superficial air velocity and initial dithionite concentration. The model predicts the experimentally obtained conversions reasonably well. 相似文献
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Ibrahim M. Abu-Reesh 《Desalination》2005,180(1-3):119-132
Analytical expressions were derived for the optimal design (based on the minimum of the volume of the total number of reactors) of N continuously stirred membrane reactors (CSMRs) performing the enzyme-catalyzed reaction described by Michaelis-Menten kinetics with competitive product inhibition. The influence of membrane selectivity for both substrate and product on the total dimensionless residence time of the reactors (overall volume) was determined. The optimal design of N CSMRs (variable volume reactors) was compared with equal volume membrane reactors required to achieve the same degree of substrate conversion. The effect of kinetic and operating parameters on the performance of membrane reactors was determined. Optimization results show that membrane reactors are superior to continuously stirred tank reactors (CSTRs) in series at a high substrate rejection coefficient and low product rejection coefficient, high substrate conversion and using a small number of reactors. Also a high dimensionless Michaelis-Menten constant, high dimensionless inhibition constant and low substrate concentration in the feed to the first reactor improved the performance of the membrane reactors vs. CSTRs in series. The reduction in total volume of the optimal membrane reactors compared to CSTRs in series was up to 86% for the conditions in this work. A comparison between the optimum and equal volume design of membrane reactors in series showed no major difference in total volume between the two design criteria at a practical range of operating conditions. A volume reduction up to 16% was observed for the conditions in this work. 相似文献
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R.V. Chaudhari B.D. Kulkarni L.K. Doraiswamy V.A. Juvekar 《Chemical engineering science》1975,30(8):945-954
Approximate solutions to the problem of simultaneous absorption of two gases in a liquid accompanied by a complex chemical reaction have been presented based on the film theory. Two approximate profiles, a nonlinear exponential profile and a trigonometric profile, for the concentration of each of the gaseous species in the film have been used in analysing the problem. The complex scheme considered is: For the exponential case two approximations have been considered: [1] in which the higher order terms are included, and [2] in which the higher order terms are neglected.The results obtained using the two profiles have been compared with numerical solutions for the film theory in the range of from 1 to 3. The results show that both the approximations yield solutions close to the numerical, in particular case [1] of the exponential approximation. Some special cases have then been considered followed by a discussion of an industrially important system: simultaneous absorption of ethylene and chlorine in water to give ethylene chlorohydrin. 相似文献
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In this work the applicability of the micro-channel reactor technique to the production of promising platform chemical 5-hydroxymethyl furan (HMF) from fructose in aqueous solution is systemically investigated by performing CFD simulations. Influential factors including solvents, residence time distribution of reaction mixtures, heat transfer conditions and micro-channel configurations are evaluated in terms of the reaction performance indices, i.e., conversion of fructose, HMF selectivity and yield. A scale-up method from a single channel to a multiple channel reactor is also proposed. It is demonstrated that: 1) at the single channel scale, controlling residence times and temperature distribution of the reaction mixture within the channel is crucial for enhancing the reaction performance, while different channel configurations lead to marginal improvements; 2) for the scaling-up of the reaction process, a reactor module containing 15 circular parallel channels could be used as module blocks, which can be stacked one by one to meet the required reactor performance and production capacity. The present results show that micro-reactors are quite suitable for HMF production. 相似文献
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Simulating the typical carbonation step in a mineral CO2 sequestration,precipitated calcium carbonate (PCC) was prepared by bubbling CO2 gas into a rich Ca solution.These carbonation reactions were conducted at three pH ranges,namely 10.0-9.0,9.0-8.0,and 8.0-7.0,in which temperature and CO2 flow rate are additional experimental variables.The PCC obtained in experiments was examined by Fourier transform infrared spectroscopy (FrIR) and X-ray diffraction (XRD).It was found that supersaturation determined by pH value and flow rate of CO2 has significant influence on polymorph of PCC.Vaterite was preferably formed at high supersaturation,while dissolution of metastable vaterite and crystallization of calcite occurred at low supersaturation.High temperature is a critical factor for the formation of aragonite.At 70 ℃,vaterite,calcite and aragonite were observed to coexist in PCC because transformation from vaterite to aragonite via calcite occurred at this temperature.Scanning electron microscopy (SEM) technology was performed on prepared PCC,and various morphologies consistent with polymorphs were observed. 相似文献
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Ashok N. Bhaskarwar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1987,37(3):183-187
Gas absorption accompanied by a zero-order chemical reaction in a finite liquid-foam film has been analysed to obtain expressions for the amount of gas absorbed and for fractional absorption in such a film. These equations may be readily incorporated into a single-stage model of a foam-bed reactor to extend it to chemisorption with zero-order kinetics. The equations for physical absorption result naturally from a special case. 相似文献
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新装置投用前,非常有必要对其进行彻底的的清洗,这是保证整套装置能够顺利开车并生产出合格产品的一个非常重要的前提条件。本文介绍了氢化反应系统在装置改造后进行化学清洗的一个方法。 相似文献
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Gas absorption accompanied by an instantaneous irreversible chemical reaction into laminar falling films of power-law liquids was studied theoretically. The convective-diffusion equations for a solute gas and a liquid-phase reactant were solved numerically and the numerical solution for the reaction factor was obtained as a function of the Graetz number, the concentration ratio, the diffusivity ratio and the power-law index of the liquid. 相似文献
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On the basis of an idealized foam bed, a model to predict conversion in a foam-bed-reactor containing surfactant has been developed. The model takes into account the effect of surface resistance, arising due to the presence of a surface active agent, on gas absorption accompanied by a chemical reaction in a foam matrix. To verify the theory, experiments have been carried out in a semi-batch foam-bed-reactor for the absorption of air-carbon dioxide mixture in a foam of sodium hydroxide solution containing finite; concentrations of different surfactants. The surface resistance offered by the molecules of surfactant at the gas-liquid interface reduces the mass transfer rates significantly. The proposed model predicts fairly well the experimentally found depletion values of sodium hydroxide. 相似文献
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An analysis of gas absorption accompanied by chemical reaction in the presence of interfacial resistance is presented. The analysis indicates that the effect of interfacial resistance on interphase mass transfer is significantly higher in presence of a reaction compared to the pure absorption case. For fixed values of surface resistance and contact time, the difference between the amount of gas transferred across the interface with and without surface resistance increases as the value of reaction velocity increases. For ranges of contact time and surface resistance of practical relevance, the influence of surface resistance is too high to be neglected while designing gas-liquid contactors. 相似文献
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D. Thoenes 《Chemical engineering science》1980,35(9):1840-1853
Modelling of chemical reactors is reviewed with an emphasis on process development and scale-up. A distinction is made between modelling of chemical kinetics, of rate processes in volume elements and of whole reactors. Examples are mainly taken from papers presented at the Sixth International Symposium on Chemical Reaction Engineering. Special attention is given to the modelling of single phase reactors, fixed beds, trickle beds, fluid beds, and gas bubble reactors. 相似文献
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Deactivation disguised kinetic schemes in an isothermal transport reactor are differentiated by means of periodic operation of the reactor. A periodic rectangular pulse is assumed for the inlet concentration. Three numerical examples are given to demonstrate that the deactivation disguised kinetic models give different conversions under periodic operation. 相似文献