Avaliação de evaporadores de múltiplo efeito real utlizando excel

Abstract

Evaporation is the process of concentrating solutions, which occurs through the elimination of the solvent through boiling (steam generation). In the chemical industry it has significant importance, especially from an energy point of view. When the process occurs in a single stage, it is called a simple effect. However, it is very common to find it occurring in several stages, called multiple-effect evaporation. Multiple-effect evaporation is used in numerous processes, such as, for example, the production of sugar, condensed milk, salts, the chlor-alkali industry, etc. The steam produced in one effect has a high enthalpy and is therefore carried to the next effect until the last evaporator, thus providing better energy use of the process. Therefore, this Course Completion Work seeks to evaluate multiple-effect evaporators using Excel, bearing in mind that mass and energy balances have many variables to be analyzed. Furthermore, this tool is easy to access for students and professionals in the field. Using real data provided by a local sugar and energy industry, it was possible to calculate the currents of concentrated juice, steam generated and heating steam. In this way, we obtained the equipment vapor savings (EV) that corresponds to the coefficient of performance for each box individually and then determined the global coefficient of performance (COP) for the set of evaporators. According to the literature, an efficient evaporation system must have Ev >1. Our calculations found that the system studied meets this requirement perfectly. Every 1 kg of steam consumed evaporated 2.6 kg of water on average. Furthermore, we calculated the evaporation rate based on the estimation of the global heat exchange coefficients in each box and the evaluation of the exchange areas. It was found that the decrease in the exchange area is in agreement with the decrease in the evaporation rate. The set of results demonstrated that the convenience of the EXCEL tool can be used to calculate the efficiency of multiple effect evaporators.