Análise exergética como ferramenta para otimização do processo de destilação.

Abstract

It has been a long time since we have been interested in energetic issues in our way of life. This was always, and seems that it will continue being, an extremely complex and polemic subject. Maybe a convergence point can be reach when it comes to the energy limited availability which, once destroyed, it can never be used again. So, the correct and optimized use of this essential resource utilized by humankind makes it imperatively important i f we want to continue improving life in this planet. Concerned about this matter, a lot of researchers looked for understanding what phenomena have been related with energy exchanges in the environment and in processes made by mankind. Because of that, Thermodynamic science and its fundamental laws were developed. The perfect combination o f these laws made possible processes enhancement and optimization according to an energetic point of view. By joining these laws, it has been arisen the exergy concept. This quality standard of energy, as preached by its developers and followers, became an important tool to improve the best use of energy. It began to talk freely about degradation of energy and not only about conservation of energy. The investigation of the exergetic losses showed to be a very important part in energetic balances through the deepest concept of irreversibility which allowed, along with efficiency definitions, that an extremely efficient and objective method could be developed in order to maximize the use of energy for general processes. But we can't talk about optimization without talking about capital costs that have everything to do with process improvements. Generally speaking, one follows the tendency of the other, viz., invariably more efficient processes are related with higher capital costs or smaller interest return rates. In this work various forms of process thermodynamic analysis were investigated based on the concept of exergy. In the first instance, general definitions about the subject were developed. As of this point, applications of those concepts were employed in some specific systems leading to a case study extracted from a real distillation process in a petrochemical plant from which the results of the thermodynamic and economic analysis of the optimized case were compared with the basic case in order to allow to the shareholders to choose the best alternative.