Modelagem e otimização do processo de liofilização : aplicação para leite desnatado e cafe soluve

AUTOR(ES)

Edinara Adelaide Boss

DATA DE PUBLICAÇÃO

2004

RESUMO

Freeze drying is a separation process based on the sublimation phenomenon. This process has the following advantages compared to the conventional drying process: the material structure is maintained, moisture is removed at low temperature (reduced transport rates), product stability during storage is increased, the fast transition from moisturized product to dehydrated product minimizes several degradation reactions. Freeze drying process has not been studied well enough compared to conventional processes. In order to put it to practice, a mathematical model based on fundamental mass and energy balance equations has been developed, based on a deterministic mathematical model proposed by LIAPIS and SADIKOGLU (1997). The proposed model contains the freeze-drying equations, which are solved by orthogonal collocation and Jacobi polynomial approximation. Factorial design was used to improve the dynamic mathematical model. The results show that the dynamic mathematical model represents well the process and is especially well suited for real time optimization. As a case study to illustrate the model utilization in a real time optimization procedure, the freeze-drying process was optimized by the method of Successive Quadratic Programming (SQP) used for solution of non-linear equations, for skimmed milk and soluble coffee. For the optimization of the freeze-drying process, the NLPQL routine developed by SCHITTKOWSKY (1985) was chosen. This algorithm adapted well to the used mathematical model and it showed itself robust for both case studies considered. The results showed that the optimization is an important tool in maximizing the amount of removed water and minimizing the time of the freeze drying process with significant impact on the energy consumption and hence in the process costs.

ASSUNTO(S)

planejamento experimental secagem por congelação modelos matematicos otimização matematica simulação (computadores)

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