Clarification of fermenter beer.

Brash, A.D. and Shelswell, B.

Abstract
Variations in the yeast content of beer at racking cause uncertainty in the primary filtration. Cleansing by centrifuge may be automatically controlled; it gives no excessive loss of beer, negligible entrainment of air and a tank beer of determined composition. To secure these advantages a Westfalia automatic desludging centrifuge was installed controlled by a turbidity meter on the beer outflow. Beer from the fermentor contains wet yeast from 0.5% to 3 times that amount and holds 2.7% CO₂. When yeast begins to overflow from the collecting bowl the turbidity meter activates the desludge cycle. The beer valves close and 100 p.s.i. CO₂ is led into the feed line, the bowl opens for 1.2 sec. to give a partial desludge then closes again and the beer valves reopen. There is a momentary foam in the effluent beer due to the discharge of the CO₂ pressure but a time delay on the turbidity meter allows this to pass. With this control system the time between the desludge operations varies from 1.5 to 20 min. on a flow of 270 brls./hr. The yeast discharge contains 80% wet solids and is diluted with a little water to facilitate pumping to the yeast drier. The high yeast content of the discharge is achieved by only partial desludging at each cycle and the high carbonation prevents pick up of air in the beer. This process gives much longer runs on the beer filter and yeast is collected, dried and sold where previously it added greatly to the contamination of effluent on filter washing. The centrifuge is run continuously during the week and when not used for beer is run on water at a gallon per minute with the bowl opening every 15 min. Cleaning is done by passing 2% NaOH with additive through the apparatus for 20 min. The machine is only stopped once a month, opened out and inspected for wear. Cleansing by centrifuge allows considerable variation in the time beer is held in the fermentor and permits the use of powdery yeast.
Keywords: beer clarification fermentation