11 th International Conference on DEVELOPMENT AND APPLICATION SYSTEMS, Suceava, Romania, May 17-19, 2012 17 Abstract — Today’s concerning about global warming and the rapid depletion of coal, gas and crude oil reserves enforced the study of alternative fuels as bioethanol. Bioethanol can be blended at low concentrations with gasoline or diesel for use in today’s vehicles, and is considered to be a sustainable transportation fuel. Present paper deals with aspects regarding the simulation of fermentation bioreactor process and fermentation bioreactor control for ethanol production. The bioreactor model was implemented in Matlab Simulink and the results of simulation using different control strategies are presented comparatively. Index Terms — bioethanol production, continuous fermentation bioreactor, bioreactor modeling and simulation, bioreactor control. I. INTRODUCTION The main motivation for investments in research and process development concerning bioethanol production is environmental concern related to global warming. The focus is, in particular, turned towards the reduction of CO 2 emissions and other green house gases. Moreover, bioethanol production would decrease the dependency on the natural oil reserves, which can due to their restricted geographical localization cause political tension and economical instability. Bioethanol can be blended at low concentrations with gasoline (usually 10% ethanol and 90% gasoline) or diesel for use in today’s vehicles without engines modifications and without affecting vehicle warranty, and is considered to be a sustainable transportation fuel. Alternatively, if bioethanol is used in higher, or 100 % concentrations, but in this case adopted vehicles engines are typically needed. Starting with biomass harvesting, there are a number of steps to follow until the final product, the ethanol is obtain(figure 1). Fig. 1. Steps in bioethanol production. . Of these processes, present paper is studying the alcoholic fermentation of glucose to ethanol. The bioreactor in which the glucose fermentation takes place is a continuous stirred- tank reactor with constant substrate feed flow. The three main components of the bioreactor are[2]: - the biomass as a suspension of yeast fed into the system and evacuated continuously; - the substrate which is solution of glucose needed in order to feed the micro-organism; - ethanol as final product evacuated together with other components. Inorganic salts, which are necessary compounds for the formation of coenzymes, are added together with the yeast. II. BIOREACTOR MODEL The kinetic equation used in the bioreactor model represents the Monod modified equations based on Michaelis-Menten kinetics, proposed by Aiba et al., and described by Z.K. Nagy[2-4]. The mass balances for the biomass is expressed by equation (1) as: where c X represent the biomass(yeast) concentration(h -1 ), µ x is the maximum specific growth rate(h -1 ), c S is the glucose concentration(g/l), K S is constant in the substrate term for growth(g/l), K p represent constant of growth inhibition by ethanol(g/l), c P is the product concentration (g/l), F e is the outlet flow from the reactor(lh -1 ), V is the volume of the mass of reaction(l). The mass balance for product is obtain as[2]: where µ P represent the maximum specific fermentation rate(h -1 ), K S1 is the constant in the substrate term for ethanol production(g/l) and K P1 is the constant of fermentation inhibition by ethanol(g/l). Equation (3) represent the mass balance for the substrate: where R SX is ratio of cell produced per glucose consumed for growth, R SP is the ratio of ethanol produced per glucose consumed for fermentation, and c S,in represent the glucose concentration in the feed flow. For the reactor and jacket, the energy balance is described Simulation of Fermentation Bioreactor Control for Ethanol Production Ana Maria MARGINEAN, Viorel TRIFA, Calin MARGINEAN Technical University of Cluj-Napoca str.Memorandumului nr.28, RO-400114 Cluj-Napoca anamaria.marginean@gmail.com , trifa@edr.utcluj.ro , ignatc@edr.utcluj.ro