New two-circuit refrigerating plant precipitates potassium bitartrate at subzero temperatures
Inführ – the name stands for quality sparkling wine and sustainable business. For over 150 years, Sektkellerei Karl Inführ KG in Klosterneuburg (Austria) has been producing sparkling wine. In addition to outstanding wines and other ingredients as well as a two-stage fermentation process lasting at least half a year, the multiple-award-winning wines are produced with the Charmat process and require precipitation of potassium bitartrate. This is a liquid at normal storage temperature but can be precipitated by cooling.
Old system replaced by modern equipment
The refrigeration equipment installed at Inführ for precipitating the potassium bitartrate had gotten old, and its efficiency and reliability no longer met today's standards. And so, the sparkling wine producer decided to invest in a new refrigerating plant for part of its production. Since 2018, this new plant has cooled more than half a million liters of sparkling wine per year. At this production volume, a refrigerating plant with a 30-kW refrigerating capacity is needed to precipitate the potassium bitartrate. It works using a brine cooling circuit. The brine circuit, which runs at a flow temperature of -12 °C, cools the content of the tank to below -5 °C – the once liquid potassium bitartrate precipitates at the below-zero temperatures and falls to the bottom of the tank.
To make this process possible, the Vienna-based plant constructor Mathias Richard Stefek designed a two-circuit system, with two compressors of type GEA Bock HGX44e for synthetic refrigerant. Each of these compressors has a displacement of 41.3 m³h (at 50-Hz operation). Besides the good value for the money, the plant constructor's good experience with the brand made the compressor choice clear. "We've installed and serviced many Bock compressors over the years. Their performance and long life convinced us," he said, praising the smooth operation and efficiency of the Bock products.
Reliability was a critical selection criterion
Reliability was also one of the main criteria for Sektkellerei Inführ. It not only influences selection of the compressor supplier, but also the design of the plant. "Thanks to the pair of compressors and the two-circuit system, the plant can refrigerate even when maintenance work is done on a machine, for example," Stefek reports.
One compressor is enough to generate around 60 percent of the maximum required capacity and ensure emergency operation at peak load. As a result, the production process is not impaired by a short standstill."
Because the Stefek Co. is also responsible for maintenance, it is planned as needed and placed in a time window when no peak load is expected. Accordingly, the compressors can be somewhat (slightly) smaller than they would be if the system were designed for one-hundred-percent redundancy at peak load. This had a positive influence on the plant costs. Another cost-reducing factor was that the water circuit for removing the compressor heat and the existing cooling tower could be reused.
Plant concept enables long service life
The Bock compressors are operated that both have about the same operating hours per year. This permits a long service life for the overall system. The mass of the brine circuit also reduces wear, as the compressors have fewer start-stop cycles, thanks to the buffer effect of the refrigerant.
The Stefek Co. mounted both compressors and the other components onto a shared frame and checked them for pressure resistance in the company's own workshop. As a result, the plant was delivered in its entirety to the sparkling wine producer and quickly connected with pipes. "This way, we reduced the work on site to a minimum," says Stefek. The new switch cabinet was also prefabricated, so it could be installed quickly. The Stefek team carried out the entire project in a short amount of time: Only four weeks passed between award of the assignment and installation of the refrigerating plant. Final commissioning was trouble-free. "The only thing we changed afterward was the amount of brine flow: We adjusted the mass flow rate to the refrigerating capacity to make operation more energy efficient," Stefek reports. Since then, the refrigerating plant with the Bock compressors has been running quietly and without malfunction – as expected.