Beer sales in Germany have been shrinking moderately for years. In order to remain competitive, small and medium-sized brewers in particular have to increase efficiency in the brewing process and reduce product losses. The Löwenbrauerei Hall Fr. Erhard GmbH & Co. KG has developed a mobile pump unit with the plant manufacturer Wellmann Engineering that optimises yeast management. Due to decreasing beer wall and water consumption, the family brewery’s five-figure investment paid for itself within two years.
With about 70 employees, 70,000 hectolitres of beer output and a turnover of about 10 million euros per year, the Löwenbrauerei Hall is a typical medium-sized family brewery with an affiliated mineral water company. The roots of the brewery go back to 1724. Today, the Löwenbrauerei Hall is a member of Slow Brewing e. V. and the Freie Brauern. Both organisations are committed to preserving beer diversity and beer culture. The two managing partners Hans Firnkorn and Peter Theilacker are direct descendants of Johann David Deutelin, the founder of the Haller Löwenbräu brewing tradition, and are the tenth generation to run the family business. Brewing processes and yeast management have also been constantly modernised. In the mid-1990s, the Hallers began to switch to single-tank processes. The further development of yeast management then led to the integration of an assimilation plant for yeast, which was in use until 2014. It was followed by the construction of a fully automated yeast cellar. Using a process of harvest yeast and assimilation yeast, the private brewery has since produced around a dozen beers throughout the year as well as a handful of seasonal beer specialities.
In 2017, graduate brewmaster Hermann Mayerle saw potential for optimisation in the separation of the yeast that settles in the lower part of the cylindroconical tanks (ZKTs) after fermentation. As in many small and medium-sized breweries, Löwenbrauerei managed this process step manually: the yeast was extracted from the tank by means of a manually guided pump, while the brewer monitored through a viewing window whether he was still extracting yeast or already beer. Due to the formation of eddies in the tank, which could hardly be controlled from the outside, there was always a high loss of product, called beer wall, while yeast adhesions on the tank walls, for example, were not completely captured and extracted. If the yeast flow broke off in the meantime, edible beer was sucked out and unnecessarily disposed of. The yeast clots and plugs remaining in the tank regularly deposited on the filtration surfaces in the next process step, filtration, and impaired filter performance and filter service life.
“The process was no longer up to date – too uncontrolled and uneconomical,” says graduate brewmaster Hermann Mayerle, because in addition to the high beer wall, it unnecessarily tied up staff. On top of that: Due to the construction, the distance of the pipelines between the pump and the warehouse for the agricultural utilisation of the extracted yeast is about 50 metres. And the viscosity of the extracted yeast varied between thin and viscous, depending on the state of fermentation. To keep the medium pumpable over the entire length of the pipeline, the Hallers had to add drinking water. Mayerle wanted a more efficient, precisely controllable, reproducible process to draw off the yeast and lower the beer wall. This required an exact phase separation between beer and yeast. The yeast removal process was also to be automated further in order to tie up fewer personnel.
Analysis of the physical phenomena that occur during yeast extraction
Mayerle went in search of a partner for process engineering, automation and assembly, which he found in Wellmann Engineering, also a member of Slow Brewing e. V.. Together, they analysed the process flow of the yeast pumping-off procedure. The focus was on the relevant physical parameters such as flow velocity and gas saturation and differential pressure on the pump inlet and outlet sides. Other important aspects were the course of the pipeline and the yeast properties. Due to the varying homogeneity of the yeast in the course of fermentation, a series of viscosity measurements were carried out. On the basis of the viscosity analysis and the given piping routes, a precisely fitting pump could be selected and control technology realised. It quickly became clear that a mobile pump unit would be the most variable solution. Wellmann-Automation had the task of realising a compact control cabinet with a programmable logic controller and touch user interface that operates the installed measurement and control technology. The operator can start the desired pumping process via various pumping programmes. The system detects the separation of yeast from beer via the built-in measurement technology and switches off the pump-down process accordingly. In addition, further sensors monitor and control the yeast flow during the pumping process. Depending on the type of yeast, the pump can be operated individually and according to demand, so that the yeast can slip into the fermentation tank and is captured by the pump suction. The frequency-controlled pump works steplessly so that the yeast flow does not run off and no residues form in the cone of the ZKTs, which can lead to faults again during filtration. At the same time, the unit precisely separates the yeast and beer phases.
After two years in regular operation, master brewer Mayerle draws an all-round positive conclusion: “With the mobile pump unit, we increase efficiency and added value in the brewing process and my colleagues can concentrate more on their value-adding core activities.” The water consumption was significantly reduced, the total biowaste fell by around 15 per cent, so that the five-figure investment was fully amortised within 24 months.