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Subject: drying ×

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    Influence of Tree Species, Harvesting Method and Storage on Energy Demand and Wood Chip Quality When Chipping Poplar, Willow and Black Locust
    (Basel : MDPI AG, 2020) Pecenka, Ralf; Lenz, Hannes; Jekayinfa, Simeon Olatayo; Hoffmann, Thomas
    The cultivation of fast-growing wood (e.g., poplar, willow or black locust) in short rotation coppices and agroforestry systems presents an opportunity for producing biomass sustainably in the agricultural sector. Cost-efficient agricultural wood production requires the availability of high-performance machinery and methods with which high-quality wood chips can be produced at low cost. It is known from harvesting short rotation coppices in practice that both the wood chip quality and the performance of the harvesting machinery depend on a variety of factors (e.g., harvesting method, weather conditions, tree species). That is why this study examines in detail the influence of the tree species (different varieties of poplar, willow, black locust) and the wood condition (fresh, stored or dried, frozen) on the specific energy demand for comminution in a stationary drum chipper and on the particle size distribution of the wood chips produced. For all the tree species examined, the chipping of dried as well as frozen stems was connected with a significant increase in the specific energy demand for comminution. An increase of 31% has been measured if poplar stems are chipped in frozen conditions (max. 6.31 kWh t−1). Drying led to an increase of 59% for dried willow stems (max. 6.67 kWh t−1). Drying and frost had also an influence on the size and quality of the wood chips, but no globally significant connection could be established for the examined tree varieties.
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    Energy interaction of sub processes in drying value chain using exergy waste. Study case: drying and greenhouse growing of tomato
    (Amsterdam : Elsevier, 2014) Ramireza, Tundra; Measa, Yunny; Gottschalk, Klaus
    In the drying value chain for fruits and vegetables, nine sub-processes have been identified. This work analyses the interaction between growing in greenhouses and drying sub processes for exergy and water flow reutilization. By thermodynamic model simulation, wet air from drying process is retrieved back to the crops within greenhouses. This interaction is an economic solution for the problem of high temperatures and low relative humidity within the greenhouses in hot dry environments. Humidity after the drying is quantified to estimate exergy profiles. Results are an average decrease of temperature of 12.8 °C and 8.7 °C and an increment of relative humidity of 7% and 9%, for different day conditions.