Tag Archives: hop drying

806–815 A. Rybka, P. Heřmánek and I. Honzík
Effect of rotors on the parameters of hop drying in belt dryers
Abstract |

Effect of rotors on the parameters of hop drying in belt dryers

A. Rybka*, P. Heřmánek and I. Honzík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
*Correspondence: rybka@tf.czu.cz

Abstract:

This article contains a design and verification for a technical solution aimed at optimising the hop drying process in belt dryer and at increasing the quality of the final product. Above the first belt of our belt dryer two evenly distributed double-arm rotors were installed and tested in operation to improve the permeability of the drying air through a flattened hop layer, as well as to improve the speed of drying. The measurements carried out in operation and comparing the drying process with the rotors switched on and off concluded that by inclusion of rotors the hop layer becomes more permeable, and when switched on, the rotors have a positive effect on faster reduction of the relative humidity and on increase of the drying air temperature. With rotors switched on, the percentage drop in the drying air relative humidity at the third inspection window of the first belt, compared to the first inspection window, was 41% on average (values obtained from data loggers and fixed sensors), the drying air temperature increased by 29%, and the hop moisture content decreased by 12%. Whereas with rotors switched off, the drop in the drying air relative humidity was only by 26% on average, the drying air temperature increased only by 14%, and the hop moisture content decreased by 12%. Based on long-term monitoring of fuel consumption during the whole harvesting season starting 2011 until 2017 inclusive, the average annual consumption of LFO (2011–2014) results in 494 L t-1 operating without rotors, and 431 L t-1 when operating with rotors (2015–2017). This implies that due to the implementation of rotors, the fuel saving being 13% is significant.

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859–865 A. Rybka, P. Heřmánek and I. Honzík
Theoretical analysis of the technological process of hop drying
Abstract |
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Theoretical analysis of the technological process of hop drying

A. Rybka*, P. Heřmánek and I. Honzík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
*Correspondence: rybka@tf.czu.cz

Abstract:

This article is aimed at the current questions concerning hop drying, a process which represents a significant part of energy consumption for hop producers. The water content drops during hop cone drying from the original approx. 80% of moisture to 8 or 10%. The drying medium is heated air, and the maximum drying temperatures range between 55 °C and 60 °C, remaining practically stable for the entire duration of drying. Hops are exposed to these temperatures for 6 to 8 hours. The current old and ageing belt dryers record large losses. Their modernisation and particularly new drying technologies need to derive from perfect knowledge of thermal characteristics of materials and drying devices. The drying process and the actual implementation necessarily depend on the knowledge of the entire process calculation that is why the paper introduction outlines simplified issues concerning a ‘theoretical dryer’ following the hx chart. An experimental measurement was carried out in an operating belt dryer. It included measurements of the drying medium thermal and moisture parameters and of the drying hop qualitative parameters. These drying parameters were monitored by means of continuously recording data loggers and of a laboratory analysis of the samples (hop moisture content, alpha bitter acids, Hop Storage Index). The drying process revealed that hops are practically dry (10 ± 2.0% of moisture content) already at the end of the second belt or possibly at the beginning of the third belt. It was also proven that hops are excessively dried (moisture content of 4 to 8%), adjusted to their final moisture of 8–10% through conditioning. Excessive drying results in considerate hop-cone shatter which makes the hop manipulation difficult during further processing, leading to larger losses of lupulin.

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