Energy efficient hop kilning system with integrated hop oil recovery from the exhaust air

Sustainability Session
Ruslan Hofmann, VLB Berlin e.v., Berlin, Germany
Co-author(s): Roland Folz, VLB Berlin e.v., Berlin, Germany

ABSTRACT: After harvest green hops show water contents of 70–80%, which must be reduced to approximately 10%. During the hop kilning process fresh air is heated to approximately 65°C. The exhaust air has temperatures of 28–35°C and a relative humidity of up to 100%. In conventional hop kilning systems the air is released directly into the atmosphere. With the help of the company WOLF Anlagen-Technik GmbH & Co. KG a pilot heat exchange system was integrated into an industrial size hop kiln in the Hallertau region of Germany. The goal of the project was to decrease the consumption of fossil resources for heating and to recover volatile hop components from the exhaust air of the hop kiln. Via suction pipes the exhaust air may be conveyed to the heat exchanger. One pipe was equipped with a carbon filter to trap volatile hop components from the exhaust air of the hop kiln. The carbon filter material was analyzed using gas chromatography. The heat exchanging process generated condensate, which was analyzed in the same way. Hop oils were detected in the condensate as well as the filter material. At least 0.25 mg of hop oils per hour and m3 of exhaust air could be recovered. The exhaust air had a mean temperature of 31.3°C. Post heat exchange the air left the HE unit with a mean temperature of 23.2°C. In the mean, fresh air was heated from 15.0 to 24.4°C. Heat recovery resulted in an efficiency of approx. 50%. These figures led to a calculated 38 kW/hr energy recovery or a reduced energy consumption of 20.8%. According to the current price level (0.8 euro/L fuel oil) a theoretical saving of approx. 200 euro/day the kiln is running was achieved.

Ruslan Hofmann received his Diplom-Ingenieur (comparable to master of engineering) degree in brewing technology from Technische Universität Berlin, Germany. Before studying he worked for the Berliner Bürgerbräu Brauerei in Berlin. Since 2008 he has been employed at the research and educational institute Versuchs- und Lehranstalt für Brauerei (VLB) in Berlin e.V., where he worked in the packaging laboratory for nearly two years and afterward joined the Department for Brewing & Beverage Science and Applications. Ruslan is responsible for research projects in the field of packaging, raw materials, and flavor stability.