Evaluation of fibrous plant pellet moisture content dependence on produced biofuel quality characteristics

Abstract

Investigations of non-traditional herbaceous plants were carried out and physical-mechanical parameters of granules, such as density and resistance to compression, were determined. Investigations were carried out in the fields and laboratories of the Vytautas Magnus University Agriculture Academy (VMU AA) in 2017-2019. In the Institute of Agricultural Engineering and Safety technological-technical means of processing these plants, biofuel pellet production and usage for energy purposes were investigated. In the Lithuanian Energy Institute (LEI), parameters of granule thermal properties, such as the calorific value, elemental composition and ash content, were evaluated. Studies of pellets of unconventional herbaceous plants (fibrous hemp, fibrous nettle) have shown that as the moisture content of pellets increases, their density decreases. Density of the produced 10 ± 2 % moisture biofuel pellets showed that the highest density of pellets were obtained by pressing fiber hemp “Bialobrzeskie” granules – 1263.3 ± 45.1 kg·m-3, and the lowest density was of fibrous nettle granules – 1221.6 ± 32.7 kg·m-3. Density of the pellets is high enough to meet the requirements for granulated biofuels. The research results of the investigated pellet strength (compressive strength) showed that at 10.0 ± 0.1 % moisture content of granules, the maximum critical compressive strength under pressure of fibrous hemp “Bialobrzeskie” granules was 850 N force, and the least resistant fiber hemp “Epsilon 68” granules reached 550 N force. After evaluation of the thermal properties of the fibrous plant pellets, it was found that the prepared biofuel is sufficiently calorific, since its calorific value is close to that of straw and previously our investigated woody plants: the studied fibrous hemp reached 17.3-17.5 MJ·kg-1 and fibrous nettle was very similar – 17.2 MJ·kg-1 . These parameters meet the[...]