Abstract
Our paper presents the hammer mill working process optimization problem destined for milling energetic biomass (MiscanthusGiganteus and Salix Viminalis). For the study, functional and constructive parameters of the hammer mill were taken into consideration in order to reduce the specific energy consumption. The energy consumption dependency on the mill rotor spinning frequency and on the sieve orifices in use, as well as on the material feeding flow, in correlation with the vegetal biomass milling degree was the focus of the analysis. For obtaining this the hammer mill was successively equipped with 4 different types of hammers that grind the energetic biomass, which had a certain humidity content and an initial degree of reduction ratio of the material. In order to start the optimization process of hammer mill working process, 12 parameters were defined. The objective functions which minimize hammer mill energy consumption and maximize the milled material percentage with a certain specific granulation were established. The results obtained can serve as the basis for choosing the optimal working, constructive, and functional parameters of hammer mills in this field, and for a better design of future hammer mills.
Highlights
Accepted: 17 January 2021Lately, the depletion of conventional energy resources and concern for reducing greenhouse gas emissions represent the main argument for the use of renewable resources for energy production
The specific energy consumption was even 17–18% smaller in the case of using one step hammers, in comparison to the levels, which were given by two step hammers or with approximately 20% towards the three step hammers, these results being recorded in the case of grinding Miscanthus Giganteus stems
The distribution of the grinded material sizes resulted in a grinding process using a hammer mill is influenced by the dimension of the sieve orifices and the feeding flow with high influence on grinded material distribution, while the feeding flow presents a lower connection to the same distribution
Summary
The depletion of conventional energy resources and concern for reducing greenhouse gas emissions represent the main argument for the use of renewable resources for energy production. The authors reported that biomass moisture significantly influenced comminution energy consumption, especially for finer size reduction They found that the Retsch SK100 hammer mill was more energy efficient than the SM2000 knife mill due to the higher motor speed and axial feeding mechanism. Presented an evaluation of the biomass size reduction process, trying to insights for interested scientists, engineers, researchers, entrepreneurs for future development and investigation to improve the biomass utilization industry through technologies They concluded the importance of studying biomass size reduction in order to produce highquality grinded particles. The authors evaluated the most representative characteristics (moisture, bulk density, durability, ash content, chemical composition and high heating value) and compared them to specific standard They reported that their results showed significant differences among the analyzed pellets, exceeding the limits established by the standard.
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