In the ethanol production process, yeast is used as a biological agent to transform sugars into ethanol during fermentation. At this stage, it’s critical to control bacteria populations as they compete with yeasts for the sugars present in the fermentation medium. Bacteria consume sugar and produce acids, reducing the efficiency of ethanol production.
At the end of fermentation, the yeast is recovered and sent to a yeast treatment tank (YTT), where sulfuric acid is used to adjust the conditions of the medium and control the bacterial population. In this process, the control of the acid dosage is extremely important, since excess acid reduces the activity of the yeast, resulting in a drop in ethanol production.
To improve microbiological control, the Nalco Water team used PURATE™ technology, which unlike other programs, produces ClO2 in an appropriate generator, under controlled conditions, resulting in greater safety and efficiency in the application while ensuring the adequate amount of biocide without damage to yeast or to the environment.
The aqueous ClO2 solution generated by the PURATE technology was added directly to the YTT, ensuring the correct dosage for bacteria control.
With the use of PURATE technology in the microbiological control of fermentation, it was possible to reduce the consumption of sulfuric acid applied in YTT, as well as the volume of total biocide. With better control of the bacterial population, there was an increase in fermentation efficiency and a consequent increase in ethanol production.
Based on the production of ethanol of 120,000 m3/year, with the price of ethanol at USD $0.572/liter and sulfuric acid at USD $0.324/Kg, plus the replacement of NaClO2 by PURATE technology, the plant registered the following gains: