Ethanol Bioproduction in Three-Phase Fluidized Bioreactors

Abstract

In the last decade bioalcohol has become more and more important as an alternativeenergy source and chemical feed stock. Bioethanol production has been proposed as agasoline enhancer to reduce greenhouse gases, gasoline imports, and to boost the economy.Circulating fluidized beds (CFB) have been used in a variety of industrial processes due totheir distinct advantages of uniform temperature distribution, high gas-to- particle mass andheat transfer rates and flexible operation.The present study deals with the experimental analysis of the circulating fluidized bedreactor, which is applied to the fermentation of glucose to ethanol. The study takes intoconsideration the presence of three different phases; yeast (solid) which is continuouslyfluidized by the liquid stream (glucose solution), and the gas bubbles which greatly enhancemixing and the wake phase which follows tracks of the gas bubbles. The reactorperformance is analyzed as a function of major operating conditions, the yeast mass in thereactor (30-150gm/l), the concentration of glucose in feed (10-150gm/l), reactiontemperature (15,25,30,36,37, and 40ºC) , and velocities of gas and liquid feeds (0.01-0.1m/s).The results indicate that high glucose conversions can be obtained at high gas velocities, lowliquid velocities, high yeast concentration, and an optimum operating temperature of 36oC.