Contribuição do trabalho mecânico nas equações de balanço em procedimentos de otimização.

Abstract

The integration of stirring systems in the calculation and optimization procedures has suffered a significant lack of attention, what it can reflect in the results because such systems provide an additional energy to the process, besides promote a better distribution of mass and energy. This is meaningful for the reactive systems, particularly for the Continuous Stirred Tank Reactor (CSTR), for which the key variables and parameters, as well as the operating conditions of stirring systems can play a pivotal role. Neglected these factors can lead to sub-optimal results as can be observed in the literature. It is also well known that the sole use of the First Law of Thermodynamics as an optimization tool can not yield expected results, hence the joint use of the First and Second Laws condensed into a procedure so-called entropy generation minimization (EGM) has shown itself able to drive the system towards better results. Therefore, the main objective of this thesis is to determine the effects of key parameters of the stirring system in the optimization procedures by means of EGM applied to the reactive and non reactive systems. Such considerations have been possible by dimensional analysis according to Rayleigh and Buckingham's method, which takes into account the physical and geometric parameters and the variables of the reactive system. Consider for the simulation purpose the production of propylene glicol, the results have shown a significant increase in the conversion rate from 36% (not-optimized system) to 95% (optimized system) with a consequent reduction of byproducts. In addition, it has been possible to establish the influence of the work of the stirrer in the optimization procedure for the reactive and non reactive systems. The results also indicate that the use of the entropic analysis as optimization tool has been proved to be simple, easy to apply and requiring low computational effort.