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Heterogeneous studies in pulping of wood: Modelling mass transfer of alkali
Simão, João P. F.; Egas, Ana P. V.; Carvalho, M. Graça; Baptista, Cristina M. S. G.; Castro, José Almiro A. M.In this paper a heterogeneous lumped parameter model is proposed to describe the mass transfer of effective alkali during the kraft pulping of wood. This model, based on the spatial mean of the concentration profile of effective alkali along the chip thickness, enables the estimation of the effective diffusion coefficient that characterizes the internal resistance to mass transfer and the contribution of the ex...
Moving finite elements method applied to dynamic population balance equations
Duarte, Belmiro P. M.; Baptista, Cristina M. S. G.A moving finite elements scheme is developed and used for solving 1-D dynamic population balance equations (PBE). The method stands on the weighted finite-elements based approach, and the local solutions are represented by cubic Hermite polynomials. The weighting function is the gradient of residuals with respect to time derivatives of the solution at the nodes and nodal velocities. The general PBE considered i...
Continuous adiabatic industrial benzene nitration with mixed acid at a pilot pl...
Quadros, Paulo A.; Oliveira, Nuno M. C.; Baptista, Cristina M. S. G.A pilot plant for the continuous adiabatic nitration of benzene was constructed, reproducing the industrial operating conditions, in order to identify the reaction regime prevailing in this industrial process. Important process parameters were tested covering a wide range of operating conditions: reaction temperature (80-135 °C), benzene to nitric acid molar feed ratio (0.96-1.15) and stirring speed (390-1700 r...
Different Modeling Approaches for a Heterogeneous Liquid-Liquid Reaction Process
Quadros, Paulo A.; Reis, Marco S.; Baptista, Cristina M. S. G.Multivariate linear regression (MLR) techniques were used to develop empirical models which are able to predict the formation of the main product and byproducts of the adiabatic benzene nitration process, as a function of the main operating conditions. Experiments carried out in a pilot plant enabled us to reproduce the operating conditions of the industrial process, providing experimental data in the intermedi...
Different Modeling Approaches for a Heterogeneous Liquid−Liquid Reaction Process
Quadros, Paulo A.; Reis, Marco S.; Baptista, Cristina M. S. G.Multivariate linear regression (MLR) techniques were used to develop empirical models which are able to predict the formation of the main product and byproducts of the adiabatic benzene nitration process, as a function of the main operating conditions. Experiments carried out in a pilot plant enabled us to reproduce the operating conditions of the industrial process, providing experimental data in the intermedi...
Benzene nitration: validation of heterogeneous reaction models
Quadros, Paulo A.; Oliveira, Nuno M. C.; Baptista, Cristina M. S. G.The film and the Danckwerts penetration models were used to model the heterogeneous liquid-liquid reaction of benzene nitration. Analytical solutions were developed for both models considering a pseudo-first order reaction. Models were confronted with experimental results showing good predictions in the intermediate reaction regime (0.3<Ha<2). Profiles of both models were evaluated confirming similarities and i...
Nitrophenols Reduction in the Benzene Adiabatic Nitration Process
Quadros, Paulo A.; Castro, José A. A. M. Castro; Baptista, Cristina M. S. G.The benzene adiabatic nitration process has been carried out in a pilot plant to enable the study of this reaction under relevant industrial operating conditions, aiming to increase the reaction conversion and selectivity by reducing the nitrophenols. The influence of relevant operating parameters such as the reaction temperature, benzene-to-nitric acid molar feed ratio (FB/FN), and stirring speed was studied. ...
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