Eficiência energética de evaporadores de múltiplos efeitos

Abstract

Evaporation is the removal of the solvent, in vapor form, from a solution. This operation occurs in a suitable equipment, called evaporator, and is used to concentrate a solution composed of a non-volatile solute and a volatile solvent. The concentration occurs by boiling the solution with the removal of the generated vapor. Evaporation in multiple effects is used in numerous processes, for example, sugar production, condensed milk, salts, etc. The steam produced has a high enthalpy that can be used, and simply sending it to the condenser is a waste of energy. To avoid this loss, and therefore to save energy, the multi-effect evaporators have been developed. A multi-effects evaporator consists of several evaporators connected in series, in which the steam produced in the first effect is used as heating vapor in the following effect. The steam generated in the last effect goes to a condenser. This is probably the most widely used industry operation for energy saving in evaporative systems. Its principle is to divide the evaporation into several bodies of equipment, called effects or stages, using water evaporated from an effect as a means of heating the next effect. During the work that culminated in the preparation and presentation of the TCC, a mathematical model for the multi-effect evaporator was developed due to the need to obtain average operating values and parameter estimates that can be used. The mathematical model is based on the mass and energy balances for the set of evaporators and they were solved to determine the intermediate currents of the evaporator cluster. In addition, the efficiency of the system was assessed and it was verified where losses are occurring in the process. The computer program generated results of the steam served (S) and the vapors produced in each evaporator (Vi). From these data, a COP, performance coefficient, of 4.48 was found. The Brix values of each stage were also determined. The solute was concentrated when passing from stage to stage and came out in the fourth effect with a value of 65 ° Brix, within the standards expected by the literature.