Comparação de abordagens termoeconômicas: aplicação a uma planta dual com ciclo a vapor e evaporação Multietapa Flash

Abstract

The focus of this work is a dual-purpose plant which operates in a Rankine Cycle with four closed feedwater heaters and one deaerator, whose function is to produce, at the same time, electricity and steam to be directed to the production of desalinated water in a MSF unit. The aim is to perform thermoeconomic evaluation by using cost allocation, using three thermoeconomic models (E, E&S and H&S), with its variants for formulation of auxiliary equations (multiproduct and subproduct criteria) in order to determinate exergetic cost of the final products. For E&S and H&S models, the MSF unit was studied in two ways: full and split into two components. The results were analyzed considering general aspects of thermodynamics and cogeneration, calculating irreversibilities, resource/product relations, in addition to the discussion about the behavior of ordered pairs exergetic unit cost of power x unit cost of water. The models E&S-MP proved to be inconsistent from the point of view of the thermodynamic aspects and advantages of applying cogeneration. The H&S model with no dismemberment of MSF unit is also consistent with in relation to the advantages of cogeneration, but that methodology is not effective in the aspect of the cost formation analysis. The other models are located in the region where cogeneration is notable advantageous, but some of them using arbitrariness inherent to the subproduct criteria. The other models studied E and H&S (with dismemberment of MSF) models proved to be most consistent.