Estudo comparativo da destilação em batelada operando com refluxo constante e com composição do destilado constante
Maíra Mendes Lopes
Estudo comparativo da destilação em batelada operando com refluxo constante e com composição do destilado constante / M.M. Lopes. --São Paulo, 2008. 155 p. Dissertação (Mestrado) -pelos ensinamentos e pela ajuda. À CAPES pela concessão da bolsa de mestrado. Às excelentes amigas Denise e Lilian pelo exemplo de profissionais e pelas diversas colaborações prestadas durante a elaboração deste trabalho. Aos meus pais pelo incentivo constante. Palavras-chave: Destilação. Destilação em batelada.
... o constante. Refluxo variável. Destilação em laboratório. Simulação matemática. ABSTRACT The aim of this study is to compare two operational methods of batch distillation of a binary system (methanol-ethanol): constant reflux and constant distillate composition. A phenomenological modeling concerning each mode was developed. It was based on material and enthalpy balances, equilibrium relationships, estimation of physical properties (specific heat and latent vaporization heat of mixtures), determination of ideal stages number (using McCabe-Thiele method), calculation of rebolier and condenser thermal loads and areas, steam and cooling water requirement, distillation time and some economical aspects. The mathematical model was implemented into an electronic spreadsheet. The predicted values were compared to experimental results from eight tests carried out in a laboratory sieve tray column (four at constant reflux and four at constant distillate composition), and a good consistency was found. Then several case studies concerning each distillation mode as well as the comparative performance were accomplished through mathematical simulations. Evaluation of the basic process variables such as reflux rate, initial load, distillate composition and flow rate was done. Rating of an existing plant and design of a new installation were considered in this process analysis. For an existing installation, lower distillation time, as well as higher distillation capacity and monthly profit were observed when distilling with constant distillate composition, keeping constant the flow rate of vapor from the column top. This process is also the more advantageous one when designing a new plant since smaller heat exchanger areas are required. However, to process a quantity in a same time, in a design of a new plan, as number of separation stages increases, monthly profit becomes almost the same among the studied distillation modes.