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Briquetting is one of the recommended biomass agglomeration processes. The material subjected to briquetting gains valuable functional features related to higher energy density, appropriate moisture content, and increased bulk density. However, the briquettes need high mechanical durability to maintain high quality during transportation, loading, and other logistic steps before they will be delivered to the final consumer and utilized for energy purposes. The mechanical durability depends on many factors, including the particles comminution of the compacted biomass. Therefore, the aim of this study was to analyze the impact of particle comminution on the mechanical durability of wheat straw briquettes. The research was carried out in accordance with the international standard for solid biofuels PN-EN ISO 17831-1:2016-02. The briquettes were produced from three different fractions: 0–2 mm, 2–15 mm, and 15–45 mm. To obtain more data related to the mechanical durability of briquettes, the tests were also carried out outside the ISO standard conditions. During the investigations, the working chamber operation time was extended from 5 to 60 min, and the rotational speed of the working chamber was increased to 25 and 30 rpm, respectively. The results indicated that the mechanical durability index (Du) of briquettes decreases along with the increase in the particle size. According to the PN-EN ISO 17831-1:2016-02 standard, the highest mechanical durability was achieved for the 0–2 mm fraction (Du = 91.17%) followed by the 2–15 mm fraction (Du = 88.12%), and the lowest was achieved for the 15–45 mm fraction (Du = 84.48%). It was noticed that the increase in the working chamber operation time resulted in a decrease of the Du value. Moreover, the difference in mechanical durability (between t5 = 5 min and t60 = 60 min) was greater for a larger fraction (∆Du = 16.26% for 0–2 mm fraction, ∆Du = 21.04% for 2–15 mm fraction, and ∆Du = 23.43% for 15–45 mm fraction). It was also observed that the increase of the rotational speed of the working chamber caused a slight decrease in the value of the mechanical durability of briquettes for all investigated fractions. [ABSTRACT FROM AUTHOR]

For biomass compaction, it is important to determine all aspects of the process that will affect the quality of pellets and briquettes. The low bulk density of biomass leads to many problems in transportation and storage, necessitating the use of a compaction process to ensure a solid density of at least 1000 kg·m−3 and bulk density of at least 600 kg·m−3. These parameters should be achieved at a relatively low compaction pressure that can be achieved through the proper preparation of the raw material. As the compaction process includes a drying stage, the aim of this work is to determine the influence of the drying temperature of pine biomass in the range of 60–140 °C on the compaction process. To determine whether this effect is compensated by the moisture, compaction was carried out on the material in a dry state and on the materials with moisture contents of 5% and 10% and for compacting pressures in the 130.8–457.8 MPa range. It was shown that drying temperature affects the specific density and mechanical durability of the pellets obtained from the raw material in the dry state, while an increase in the moisture content of the raw material neutralizes this effect. [ABSTRACT FROM AUTHOR]