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Better clear than cloudy

Quality-assured production of suspensions for beer filtration

Naturally cloudy or filtered? The Germans have a clear answer to this question. They prefer their cool blond beer clear. To ensure that their hop extract is always filtered evenly, the private brewery Waldhaus from the Black Forest requires a consistently high quality of the kieselguhr suspension used. To produce the suspension, the company therefore uses a TDS suction mixer from ystral, which has replaced a conventional agitator.

ystral TDS-Induction Mixer The TDS-induction mixer from Ystral is suitable for the production of suspensions in the food and beverage industry

The Waldhaus private brewery has its roots in 1833 and has been owned by the Schmid family for 125 years. Today it is managed by Dieter Schmid, the fourth generation of the Schmid family. The brewery has an annual output of a good 100,000 hl, and its most recent annual turnover was around 12 million euros. In addition to wheat beers and naturally cloudy beers, the brewery mainly produces filtered beers, which are the Germans' favorite drink.

Waldhaus is one of the most award-winning breweries in the world. In 2018 alone, it received 41 gold awards. Waldhaus' bestseller, the clear and filtered Diplom-Pils, was awarded this prize by the German Agricultural Society (DLG) for the 20th time in a row.

Kieselguhr ensures clarity

Naturally cloudy beers are usually bottled directly after the fermentation process. Because they are not filtered, they still contain the suspended and cloudy substances that are naturally produced during brewing. These are hop residues, a little yeast and proteins that form from the malt. In filtered beers, these clouding substances are removed without affecting the taste. This is achieved in the first step by so-called depth filtration using a kieselguhr suspension. Diatomaceous earth, a white, powdery substance, is obtained from the shells of fossil diatoms and is suitable for many applications as a filter medium.

In order to filter the beer, a diatomaceous earth suspension must first be produced. The quality of the beer essentially depends on a precise mixing ratio between diatomaceous earth and water. At the Waldhaus brewery, the use of the YSTRAL TDS suction mixer has improved the precise dosing of diatomaceous earth and filter aids.

Uncomplicated installation

The project itself was straightforward. Six weeks after contacting us by telephone, theTDS suction mixer was already fully integrated into the Waldhaus process chain. Dieter Schmid is convinced of the advantages of the new technology: "The clean operation of the TDS suction mixer prevents the formation of dust when the diatomaceous earth is introduced into the water. We also achieve better homogeneity of the diatomaceous earth suspension. The easier handling compared to conventional technology is another plus point."

How the mixer works

The TDS suction mixer works according to the rotor-stator principle. A fast-turning rotor, which is surrounded by a stator, generates a downward-directed jet that guides the liquid flow directly to the bottom of the tank. At the bottom of the tank, this flow splits and creates an upward flow on the outer wall. At the surface, the liquid flow is diverted back towards the bottom of the tank. A major advantage of the TDS suction mixer is the effective micro and macro mixing of the entire tank contents without the introduction of air. The vertical mixing across all tank levels results in a complete exchange of substances. Up to 90 % of the energy used is converted into the vertical flow and there are no rotating container contents.
A further advantage: even heavy sediments are suspended by the targeted flow without the formation of turbulence and air entrainment. For safety reasons, rotating parts are protected against unintentional intervention. Various designs are possible, such as tank installation from above, from the side or operation on a lifting frame; no tank fixation is required for open tanks.

Technical data of the mixer

ystral offers the TDS suction mixer with different outputs between 0.5 and 25 kW. The speed can be set between 750/ 1500, 1500/3000 or, with a frequency converter, infinitely variable up to 3600 min-1. An explosion-proof version is also available as an option.

The bearing flange is made of coated aluminum or stainless steel. 4404. Depending on the application, lip seals or mechanical seals (single or double) are used as sealing elements. The immersion part is made of stainless steel 1.4404, special materials are also possible.
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ystral Fachartikel DEI Suspensionen

Magazine: dei
Issue: 11/2019
Author: Bernd Weber

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