Evaluation of a hammer mill and planetary ball mill for hemp fibre decortication.

摘要

Hemp fibre is becoming an increasing interest to the biocomposite industry for its market potential. Hemp fibre is comparable to other synthetic fibres, such as glass, but its high tensile strength and durability make it a superior choice. For biocomposites to be equivalent to other synthetic products, hemp must be decorticated in such a manner to achieve optimal fibre yield. The objective of this study was to test different decortication machines, including a hammer mill and a planetary ball mill, and to study the final fibre state of the product and the effectiveness of each machine. For the hammer mill, three parameters, including feeding m ass, screen scenario, and pre-cutting scenario, were used to determine the power requirement, energy requirement, fibre yield, core yield, and effectiveness of decortication of the mill. For the planetary ball mill, two parameters, grinding speed and grinding duration, were used to determine the fibre yield, core yield, chaff, detaching efficiency, and performance index of the mill. An analysis of variance was performed on the hammer mill and planetary ball mill test variables to determine significant effects of the different treatments.;Grinding speed and grinding duration parameters had an effect on the planetary ball mill performance. Low grinding speeds and short grinding durations resulted in poor detaching efficiencies (52.6%) and low fibre yields (39.1%). Whereas, high grinding speeds and long grinding durations produced all chaff (100%). Optimal fibre yield and detaching efficiency was observed when grinding speed and grinding duration were 200 rpm for 4 min and 250 rpm for 6 min, respectively.;For the hammer mill, large screen scenarios (25.7 mm round-holed openings) and a small feeding mass (75 g) allowed for a maximum fibre yield for Retted hemp (34.5%). Whereas, a 75g feeding mass and small screen scenario (19 3 mm round-holed openings) produced a maximum fibre yield (15.9%) for Green hemp. Power and energy requirements for both Retted and Green hemp decreased as the screen scenario size increased. The combination of the 19.3 mm screen scenario, a feeding mass of 75 g, and pre-cut feedstock for Retted hemp performed the best in terms of fibre yield and effectiveness of decortication.