Engineering Session
Alexander Gertsman, Flottweg, Independence, KY, USA
ABSTRACT: Disc separators have been used in breweries for approximately 100 years, with an automatic type for over 60 years. Installation of these machines in the early years affected beer quality with issues such as oxygen pick up, consistent discharges, product heating, and hygiene. The issue of oxygen pick up was solved by several methods. One design offered a bottom fed hermetic separator where the feed was introduced via hollow spindle. The bowl of the machine with this design is pressurized, and the clarified beer is discharged with a co-rotating pump. The problems with this design are the use of expensive mechanical seals and requirement for high inlet pressure to the machine. The typical design of these bottom-fed separators incorporates use of a steep cone angle of the disc stack, which does not allow for maximum solids compaction. The best alternative was found with the use of a conventional top-fed separator with a shallow cone angle and hydrohermetic sealing to prevent oxygen pick up. For a while to ensure actual zero oxygen pick up it was still necessary to provide CO2 blanketing, but a new design from Flottweg eliminates its need. With new hygienic features separators can be effectively cleaned in place rather than requiring disassembly. Design must incorporate high grade finishes and avoid trapping areas. Using automation during cleaning is important to avoid personnel presence during use of chemicals. Product heating was largely addressed with the use of a water jacket. This concerns particularly the discharged yeast. With little space between the bowl and its housing and high rotational bowl speed, the air in this space is heated and consequently the bowl and the housing. When discharged yeast comes in contact with a hot surface it dries very quickly and requires more cleaning time. In colder conditions the yeast remains wet and can be flushed away easily. Effective water jacket design provides good sound insulation. In the early years of automatic separators the bowl piston used a hydraulic system that incorporated an operating slide, valve plugs, and springs to assist the return of the piston to closing position. This system, largely seen as obsolete, is still being used by some centrifuge manufacturers. It can’t deliver reproducible discharges due to the lag in the closing mechanism. The system uses lots of parts and is hard on maintenance. The most up-to-date modern design is Flottweg’s SoftShot, which uses two simple valves mounted to the side of the bowl for easy access. Working together with modern turbidity meters this system will produce consistent discharges maximizing beer yields. Modern control systems allow for programming of different recipes when processing a variety of beers and assigning different turbidity standards to any given brand. When processing green beer tanks or running tank bottoms one can also rely on a turbidity meter installed on incoming feed that prevents overloading of the centrifuge. Another turbidity meter can be used on feed to centrate bypass for ensuring consistent turbidity of wheat beer.
Alexander Gertsman received a B.S. degree in chemical engineering from New Mexico State University. He has been working with centrifuges for 16 years, including employment with Alfa Laval and currently Flottweg, both in North America. Alexander has been responsible for brewery applications and sales for Flottweg in North America since 2005. He is also a profound crafter of homemade kvass, a Russian national malt beverage.
