Example 4.11 A dilute solution of glucose enters a continuous fermentation process, where yeast cells convert it to ethanol and carbon dioxide. The aqueous stream entering the reac- tor is at 25°C and contains 5 wt% glucose. Assuming this glucose is fully converted to ethanol and carbon dioxide, and that the product stream leaves the reactor at 35°C, estimate the amount of heat added or removed per kg of ethanol produced. Assume that the carbon dioxide remains dissolved in the product stream.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
Example 4.11
A dilute solution of glucose enters a continuous fermentation process, where yeast
cells convert it to ethanol and carbon dioxide. The aqueous stream entering the reac-
tor is at 25°C and contains 5 wt% glucose. Assuming this glucose is fully converted to
ethanol and carbon dioxide, and that the product stream leaves the reactor at 35°C,
estimate the amount of heat added or removed per kg of ethanol produced. Assume
that the carbon dioxide remains dissolved in the product stream.
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