analise dinâmica de um chiller de absorção de brometo de lítio ...

ABSTRACTEthanol fermentation is an exothermic process and the yeast kinetics is dependentson temperature. The fermentation process thus requires a refrigerationsystem to remove the heat released. Currently, cooling towers are used torefrigerate the ethanol fermentation, however this system is not sufficient tomaintain the ideal temperature, around 32 ◦ C. This study proposes an alternativecooling system for use in ethanol fermentation employing a single-effectwater/lithium bromide absorption chiller as the working fluid, powered bywaste heat from sugar and ethanol production processes. Considering thatthere is energy integration between the production processes, a refrigerationsystem is needed to keep the fermentation temperature close to the ideal valueand increase the energy efficiency. The aim of this study was to model,simulate and analyze the dynamic behavior of an absorption refrigeration systemand fermentation process. The dynamic models of the absorption chillerand the fermentation process were applied using the software MATLAB RR2008a. The results of this study demonstrate the potential application ofthe absorption chiller to refrigerate the fermentation process. The introductionof an absorption chiller allowed a reduction in the average temperatureof around 2.4 ◦ C, an increase of around 0.3 kg m −3 h −1 in the fermentationproductivity and an increase of around 2.8 % in the fermentation efficiency.The final ethanol concentration increased by around 2.6 kg m −3 , that is, theethanol production increased by 2.3 m 3 for each fermentation process usingthe absorption chiller. The fermentation process can be optimized by increasingthe inlet substrate concentration. This may promote an increase in theenergy balance of the ethanol production process by improving the relationbetween the renewable energy produced in the sugar and ethanol sector andthe fossil energy used during the process. All of these advantages contributeto the development and growth of Brazil.Keywords: absorption refrigeration, ethanol fermentation