Experimental Investigation and Confirmation of Static/Dynamic Bifurcation Behavior in a Continuous Ethanol Fermentor. Practical Relevance of Bifurcation and the Contribution of Harmon Ray

Abstract

Professor Harmon Ray is my professor, and I am proud of that. I met him first in 1969 (35 years ago!) at the Chemical Engineering Department, University of Waterloo, Ontario, Canada, and since then, we have become friends and exchanged visits across thousands of miles. In June 1969 (just one year after graduating from Cairo University, Egypt), I was visiting some friends at Waterloo when I met Harmon; after a short discussion, he offered me the opportunity to continue my postgraduate studies with him, I accepted, changed my trajectory from studying in the U.K., and stayed in Waterloo to work with him. It was one of the most fruitful periods of my life. He taught me a lot about modeling, multiplicity, and catalytic processes. We were also lucky to be joined in Waterloo by Professor Milos Marek from Czechoslovakia and Professor Horn from Vienna. After I finished my M.Sc. degree, I was supposed to go with Harmon to SUNY-Buffalo to continue for my Ph.D., but for family reasons, I had to go to the U.K. to continue my Ph.D. first at University College London with Professors Peter Rowe and John Yates and then at University of Edinburgh with the late Professor Philip Calderbank and Professor David Cresswell. Harmon visited us in Edinburgh, stayed a few days, and gave very stimulating lectures. After I finished my Ph.D. in 1973, I returned to Egypt in 1974, and Harmon and I remained in continuous contact. When I had a brilliant B.Sc./M.Sc. student (Fouad Teymour, now Chairman of the Chemical and Environmental Engineering Department, IIT, Chicago) who wanted to continue for his Ph.D. in the U.S., I immediately advised him to join the group of Harmon at University of Wisconsin, Madison. Fouad joined Harmon's group and did excellent work on the flourishing field of bifurcation and chaotic behavior of polymerization reactors. Harmon and his group were and are still doing pioneering work in this field. After that, in the 1980s and 1990s, we exchanged visits: Harmon visited me in King Saud University in Riyadh and invited me to Madison, both of which were excellent visits. Harmon is one of the excellent students from the Minnesota group of Professors Rutherford Aris and Neal Amundson. Since he finished his Ph.D. in Minnesota in the late 1960s after completion of his bachelor at Rice University, he has pioneered very advanced work on modeling, bifurcation and chaos, and optimization and control for catalytic and polymeric processes. His cooperation with mathematicians and considerable contribution to the fundamentals of the field are also of great value. He has published hundreds of papers in top international journals, as well as a number of important books, made numerous presentations at a variety of conferences, and supervised a large number of well-known researchers in academia and industry. He has also won a large number of prestigious awards. I still remember the excellent party we had in Madison for his 60th birthday. Time is flying and he is now 65, but still as productive and innovative as ever. On the happy occasion of his 65th birthday, we congratulate him and wish him and his family the best of everything. My Ph.D. student Parag Garhyan and I thank the editorial board of Ind. Eng. Chem. Res. for giving us the opportunity to honor this outstanding academician. We take this opportunity to present some of the initial experimental work being done in our laboratory at Auburn University to verify static and dynamic bifurcation in a continuous fermentor producing ethanol from glucose. Said S. E. H. ElnashaieA model for ethanol production using pure glucose in a continuous perfectly mixed fermentor was developed, and extensive nonlinear analysis was carried out to explore the possibility of increasing the sugar conversion and ethanol productivity [Garhyan et al. Chem. Eng. Sci. 2003, 58 (8), 1479. Garhyan, P.; Elnashaie, S. S. E. H. Ind. Eng. Chem. Res. 2004, 43 (5), 1260]. An interesting mix of static and dynamic properties of the system was uncovered and analyzed. In the present work, laboratory-scale fermentation experiments were carried out to verify the existence of complex static and dynamic behavior such as multiplicity of steady states and periodic behavior.