EFFICIENT COOLING OF FERMENTATION VATS IN ETHANOL PRODUCTION – PART 1

By M.O.S. DIAS a, R. MACIEL FILHO a, C.E.V. ROSSELL b
a Laboratory of Optimization, Design and Advanced Control, School of Chemical Engineering, State University of Campinas, Brazil
b Interdisciplinary Center for Energy Planning, State University of Campinas, Brazil
diasmos@feq.unicamp.br


Abstract

Fermentation done at 34ºC (sometimes at higher temperatures) limits the ethanol content of the final wine, increases energy consumption during the distillation step, increases stillage volume, promotes infection, flocculation and yeast inhibition, so the advantages of operating fermentation at temperatures of 28ºC (at least 32ºC) are evident.
A review on factors such as: wet and dry bulb temperature daily and monthly profiles, design of cooling towers and heat exchangers, the use of more efficient cooling tower internals, steam jet water cooling production system, and the use of cooled water accumulators were done. Kinetics of heat evolution during ethanol production was analysed, and a model considering these factors was developed.
This model helps to design the cooling system in order to attain the desired fermentation temperature, larger ethanol content on final wine and less stillage volume per volume of ethanol produced.
Three options are explored in this work, considering the use of a cooling tower to provide cooled water during the coolest hours of the day and the use of secondary equipment to provide cooled water during the warmest hours of the day. The equipment considered were a water accumulator, a steam jet ejector and an absorption machine.
In the case of a water accumulator, the cooling tower size would be greater, but for both steam jet and absorption machine, there would be an increase in consumption of utilities.
All options would cause an increase in initial cost, and an economic analysis is to be made in part 2 of this work in order to help in making a final decision.

KEYWORDS: Bio-ethanol, fermentation cooling, energy consumption
ISSCT XXVIth CONGRESS Durban, South Africa 29th July - 2nd August 2007) http://issct.intnet.mu/ComCop2007.htm.