Evaluation of an insertion thermal mass flowmeter to monitor CO2 evolution rate in plant scale fermentations.

Stassi, P., Goetzke, G.P. and Fehring, J.F.

Abstract
Trials of the Fluid Components LT81A insertion thermal mass flowmeter as a sensor for monitoring carbon dioxide production in industrial scale brewery fermenting vessels are described. The sensor's operating principles are explained. The carbon dioxide evolution rate (CER) indicated by the sensor was used to calculate the total amount of carbon dioxide produced in the vessel since the onset of fermentation. This in turn was found to be proportional to the ethanol content of the fermenting brew (determined by HPLC). Although data from any given sensor showed a high degree of reproducibility, both between successive fermentations of the same beer brand and between different brands, some differences between sensors were found, indicating some degree of variability in calibration. Another problem was that leakage from the fermenting vessels sometimes caused low readings (because the gas lost through leaks did not pass the sensor). Successful application therefore requires correct calibration (preferably after installation), a gastight fermenter, and accurate fill level monitoring of the fermenter contents (in order to permit sensor readings to be expressed volumetrically). Potential uses of this technology include research applications as well as carbon dioxide collection management and fermentation process control in commercial breweries.
Keywords : brewing carbon dioxide fermentation flowmeter process control sensor