1. Abstract
Through the certification in energy management (ISO 50001), Abengoa Bioenergy France would like
to reduce its energy consumption. That is the context of my mission. I thought that increasing the
temperature in the bioreactors may be a solution. Increasing the temperature in bioreactors could
reduce the consumption of cold water used to maintain the temperature constant in the bioreactor and
mainly the consumption of overheated steam used after, to heat the corn smashed mixed. Laboratory
tests had already been done and agreed to try in an industrial scale.
The temperature curve of the corn smashed mixed before passing in the heat exchanger, showed a
peak in temperature corresponding to the maximal exothermicity at the end of the filling of the tank.
The increase of the setpoint temperature is logically combined to a raise of the temperature curve,
particularly for this peak. Hence, the time of fermentation at high temperatures is extended.
An increase of the temperature setpoint after the peak of exothermicity allows to finish as warm as if it
had been done at the beginning whithout raising high temperature during the peak of the
exothermicity. The raise of the final temperature of fermentation can be significantly seen in the corn
smashed mixed which arrives in distillation. The reduction of the overheated steam consumption could
allow to earn around tens of thousands of euros per year for an increase of 1°C. The earning due to the
reduction of cold water is negligible in term of quantity and cost.
Increasing the temperature setpoint as soon as the beginning of the fermentation has showed worse
fermentation performances. The glycerol/ethanol and acetaldehyde/ethanol ratio have increased. The
level of residual sugars has also increased. That is why I lead target of temperature during the
fermentation time. My goal was to know when was the best time to do it.
I found that target of temperature at 42 hours of the fermentation has increased in the same way the
temperature at the end of the fermentation without getting lagged performances.