The choice and use of cylindro-conical fermentation vessels.
In equipping a new brewery it was desired to conserve the foaming properties of the wort to minimize fermentation losses and to ensure that vessels could be cleaned with the least possible amount of labour. To meet these requirements it was decided to use a strain of Saccharomyces cerevisiae which would give the desired flavour yet deposit to the bottom of the vessel instead of rising in a head. To accommodate 500 brl brews, vessels of total height 32.5 ft and diameter 12.25 ft were installed with 70 degree angle conical bottoms. Two cooling jackets were applied to the cylindrical body and one to the cone. The coolant selected was K2CO3 brine at 27 degrees F. The vessels were constructed in unpolished stainless steel EN58E to work with 20 ft wort depth at 20 psi. The wort is pitched with 0.5 lb yeast per brl at 66 degrees F and aerated after declaration and pitching. Fermentation proceeds with venting of CO2 for 30 h then the vessels are closed and pressure allowed to build up to the required carbonation level. After 35 to 45 h the coolant is applied and in 6 h the beer is brought from 73 degrees F to 50 degrees F. Yeast sedimentation continues till 60 h giving a dense slurry in the cone and about 2 million cells per ml in the beer. The yeast sediment is run off to be used for pitching and the beer is racked to the cellar tanks; with suitable yeast a green beer centrifuge is never used. Experience shows that the cooling jackets on the cones are not needed and that sedimentation of the yeast retains hop bitters in the beer so that the hop rate can be reduced by 15%. When lagers are produced with S. carlsbergensis in these vessels they can be filled to 670 brl but have to be lagged over the top to hold the temperature at 47 degrees F. Fermentation extends over 8 days before the beer can be chilled to 32 degrees F to deposit the yeast. Yeast is propagated by pitching 0.5 lb yeast from the laboratory into 30 brl of wort then aerating continuously for 36 h when sufficient yeast has grown to allow the addition of further 400 brl wort. Vessels are cleaned and sterilized by spraying with hot caustic detergent at 180 degrees F. After experience with these vessels further installations were made of 1480 brl and 3000 brl capacity. These are 60 ft high and 17.5 ft diam., with a wort depth of 56 ft; 4 cooling jackets are fitted on the cylindrical body and a covered way is provided round the yeast cones but otherwise the vessels stand in the open air.
Keywords: brewing cylindroconical tank fermentation survey