Measurement and control of oxygen in carbon dioxide.

Huige, N.J., Charter, W.M. and Wendt, K.W.

Abstract
Concentrations of O₂and other impurities in CO₂were measured at various locations in the CO₂purification system (Miller's Brewery, USA. A Zahn CO₂purity tester and four different polargraphic O₂analysers were used and their performance evaluated. CO₂purity depended on brew type, fermenter design, fermentation pattern, head space volume and O₂trapped when the fermenter was being filled. A number of fermentation processes are illustrated. For economy fermenters should be switched to CO₂collection when the O₂concentration in the combined CO₂flow is below a selected level. (In this plant an in-line O₂analyser is installed after the booster compressors). Water used in foam traps and water scrubber systems increase O₂in CO₂by about 6 and 22 ppm resp. O₂pick-up in the water scrubber was reduced by deaerating the water with waste vent gas from the CO₂condenser. By continuous venting of CO₂from the condenser headspace at 2.5% of the condenser feed rate the O₂concentration in CO₂was reduced on average by 20%. A distillation column designed to reduce O₂in CO₂with minimal CO₂loss is being investigated.
Keywords: analysis brewing carbon dioxide control oxygen purification recovery volatile compound