Percorrer por autor "Madureira, C. M. N."
A mostrar 1 - 2 de 2
Resultados por página
Opções de ordenação
- Multi-criteria design optimization study of solvent extraction in mixer–settler unitsPublication . Pinto, Gilberto; Gomes, Elsa; Durão, F. O.; Madureira, C. M. N.; Guimarães, M. M. B. L.; Morais, S.Solvent extraction is considered as a multi-criteria optimization problem, since several chemical species with similar extraction kinetic properties are frequently present in the aqueous phase and the selective extraction is not practicable. This optimization, applied to mixer–settler units, considers the best parameters and operating conditions, as well as the best structure or process flow-sheet. Global process optimization is performed for a specific flow-sheet and a comparison of Pareto curves for different flow-sheets is made. The positive weight sum approach linked to the sequential quadratic programming method is used to obtain the Pareto set. In all investigated structures, recovery increases with hold-up, residence time and agitation speed, while the purity has an opposite behaviour. For the same treatment capacity, counter-current arrangements are shown to promote recovery without significant impairment in purity. Recycling the aqueous phase is shown to be irrelevant, but organic recycling with as many stages as economically feasible clearly improves the design criteria and reduces the most efficient organic flow-rate.
- 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.