Percorrer por autor "Cruz-Pinto, J. J. C."
A mostrar 1 - 4 de 4
Resultados por página
Opções de ordenação
- Efficient computer simulation of the dynamics of na agitated liquid-liquid extraction columnPublication . Guimarães, M. M. L.; Gomes, M. L.; Regueiras, P. F. R.; Ribeiro, M. L.; Cruz-Pinto, J. J. C.Given the difficulties associated with experimentation upon liquid-liquid extraction processes, computer simulation of these processes has recently acquired great relevance and usefulness as complement, if not an alternative, to direct experimentation. This is becoming increasingly attractive, as both the power and the availability of personal computing increase. Recently, Ribeiro (1995), Ribeiro ef al. (1997)) developed a fast and precise algorithm, adapting population balance models as Coulaloglou and Tavlarides' (1977) for the dispersed phase breakage and coalescence, and both the rigid and the oscillating drop models as proposed by Cruz-Pinto ef al. (1983), for mass transfer. The algorithm enabled the simulation’ of the evolution in time of the trivariate joint distribution of drop properties in two-phase continuous mixers, in steady and transient states. A simplified version of this algorithm, that calculates the drop size distribution and the mean and standard deviation of solute concentration within each volume class, was further developed by Regueiras ef al (1996). In this work, the applicability of this simplified algorithm to the dynamic simulation of a Kithni liquid-liquid extraction column is illustrated. A transport model was developed from previous models of Cruz-Pinto (1979). Coulaloglou and Tavlarides’ (1977) drop interaction model was again adopted. It is shown that the algorithm is able to describe both the transient and the steady-state behaviour of a Kihni pilot column (Technical University of Munich), and the simulation runs that were made show good agreement with the experimental results. The present version of the algorithm predicts local hold-ups and drop size distributions at different column stages. So far, the results do not include mass transfer, but future work will contemplate this feature.
- The importance of drop coalescence in a stirred liquid-liquid extraction (Kühni) columnPublication . Gomes, M. L. A. C. N.; Guimarães, M. M. L.; Zamponi, G.; Stichlmair, J.; Regueiras, P. F. R.; Cruz-Pinto, J. J. C.; Cox, Michael; Hidalgo, Manuela; Valiente, ManuelExperiments performed at low agitation speeds, using the high interfacial tension toluene (dispersed)-water (continuous) system, in a pilot plant Kühni column, show that coalescence events are generally present and cannot be neglected in column-type liquid-liquid contactors, especially when the goal is the accurate modelling of the transient processes for control purposes. In this work, the features of this behaviour and the applicability to this situation of a new, fast and precise, recently developed algorithm, 1 that describes the dynamic behaviour of an agitated column, is illustrated. Experiments were performed at low agitation speeds, using the above high interfacial tension system. The simulations show reasonably good agreement with the experimental results and provide insight on the underlying behaviour mechanisms and important guidelines for the accurate modelling of the dynamics of the column.
- Precise and Fast Computer Simulations of the Dynamic Mass Transfer Behaviour of Liquid-Liquid Agitated ContactorsPublication . Guimarães, M. M. L.; Regueiras, P. F. R.; Ribeiro, L. M.; Madureira, C. M. N.; Cruz-Pinto, J. J. C.Algorithms for solving the population balance equations for the transient drop volume (v) and solute concentration (c) distributions and the dispersed phase hold-up of a continuous flow liquid-liquid system, with simultaneous drop coalescence and breakage, are very complex and make heavy demands on computing time, of the order of m4 (m being the number of discrete classes used). This paper simplifies and accelerates our already fast, recently developed algorithm, for the most common situation where a full description of the above bivariate (v and c) behaviour is not required. The mathematical foundations of the algorithm are developed and it is shown that meaningful, precise and very fast (oc m2) dynamic simulations of the full drop size distribution and of the width of the solute concentration distribution within each drop size fraction may be achieved in less than 8% of the real process time for a continuous flow stirred vessel, using an ordinary 486DX2/66MHz microcomputer. Besides the excellent time performance of the algorithm, the other important feature is that, as the full size-concentration distribution does not need to invoked or computed, a substantial economy in working memory is also achieved. Actual dynamic simulations of mass transfer and reacting systems have been performed. Limitations of space only compel us to restrict the discussion to mass transfer systems. The applicability of these techniques to real control situations is also highlighted.
- THE SIMULATION OF INTERACTING LIQUID-LIQUID DISPERSIONS - A NEW ALGORITHM AND ITS POTENTIALITYPublication . Guimarães, M. M. L.; Cruz-Pinto, J. J. C.; Regueiras, P. F. R.; Madureira, C. N. M.[Abstract] The simulation of interacting liquid-liquid dispersions undergoing mass transfer and/or chemical reactions is a major chemical engineering problem, that has not yet been satisfactorily solved. The difficulties do not exclusively lie on the experimental validation of the models and their predictions, but are still rooted on the inability of current algorithms to describe the real nature of the dispersion, namely its full trivariate structure - distribution of drop volumes (v), ages (tT) and _= solute concentrations (c) - where v, t and ce are not satistically independent. A survey is given of the authors' latest, recently published (1,2), work and a detailed discussion is then presented of the fine structure and behaviour of the dispersion; the major requirement of an adequate statistical analysis of the simulation results is also dealt with. The paper ends with the authors views on possible trends of future research on this topic.