Tank agitator retrofit improves energy efficiency

A new milk tank commissioning uncovers such convincing energy savings - the plant decided to retrofit 11 other tank agitators with Alfa Laval ALS agitators.

Located near Coburg, the company produces soft, hard and processed cheese, which is preserved exclusively with table salt. The natural cheese products are made using microbiological rennet to ferment the raw milk.

To increase production, the Milchwerke Oberfranken West plant has commissioned a new milk tank to expand its cheese production. An ALS agitator from Alfa Laval was installed in this tank to increase plant productivity and improve energy efficiency. After a three-month test, the results were so convincing that the dairy decided to retrofit eleven of the previously used agitators with an output of between 11 and 15 kW with ALS agitators.

The dairy installed a new 360,000-liter tank. With the aim of realizing cost savings through a more energy-efficient agitator, the dairy also decided to test a new type of agitator on the recommendation of its long-term supplier and Alfa Laval sales partner Euroflow: to test energy efficiency, hygiene and food safety, it installed an Alfa Laval ALS agitator that consumes only 4 kW of electrical power, instead of a conventional agitator with a consumption of 18 kW.

Smooth test phase

Milchwerke Oberfranken West began testing the agitator with a volume of 100,000 l of milk in the newly installed tank. The filling volume was then continuously increased to 150,000 l and then to the full tank capacity of 360,000 l. Samples were taken every hour to check the quality of the milk. Monitoring of milk ingredients, especially fat content, showed no changes in the cheese production line or in the manufacture of the product. As a further test, the standardized, non-homogenized milk was left in the tank for a day to see if there were any differences in the processing of the raw milk with the new agitator. The result: the test agitator worked smoothly throughout the entire process. After the three-month test phase, the dairy ordered eleven 2.2 kW ALS agitators to replace the conventional 11 to 15 kW agitators previously used in the other 220,000 l milk tanks.

Energy savings of up to 80%

The ALS agitators consist of a drive unit with bearing frame, a shaft with its own seal, and specially developed, energy-saving Ensafoil agitator blades (Ensafoil = Energy Saving Foil). These have a special geometry and therefore require less energy than conventional agitators. Energy consumption can be reduced by up to 80%. An electric drive motor transfers the energy required for mixing and stirring to the stirrer shaft either directly or via a gearbox. The shaft rotates and so do the impellers. The movement of the impellers generates a high product flow. The highly effective axial pumping effect ensures low shear stress. The result is efficient mixing and agitation of the entire tank contents. The agitators allow easy CIP cleaning and can be installed from above, below or from the side, as is the case with the milk tanks at Milchwerke Oberfranken West. The modular stirrers are available with a choice of two or three paddles and in various sizes for optimum power consumption.

 

Further projects planned

Milchwerke Oberfranken West assume that the flow behavior and the gentle treatment of the milk by the ALS agitators have had a positive effect on the final product. Following the successful retrofit of the agitators, the dairy is considering further energy saving projects. For example, the large dairy pumps can be replaced with more energy-efficient systems with higher electrical efficiency. In some cases, the electrical power of dairy pumps and motors could be reduced from 15 to 11 kW for the same hydraulic power.