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.
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