Comparative comminution efficiencies of rotary, stirred and vibrating ball-mills for the production of ultrafine biomass powders

Highlights: • Greater process efficiency when the milling device is suited to the biomass. • Milling that combines impact and attrition is more flexible and effective. • Milling that generates attrition efficiently yields fine biomass particles. • Agglomeration of fine particles significantly influences milling efficiency. Plant biomass as a substitute for fossil oil is one of the most promising pathways to reducing the environmental impact of human activities. Ultrafine comminution of plant materials can produce ultrafine powders suitable for direct use in advanced-technology applications as an engine, becoming a sustainable powdered biofuel. However, comminution is an extremely energy-intensive process, making it vital for industry to select the most efficient milling device for the biomass. Here, we comprehensively compared the efficiencies of three batch ball mills employable for ultra-fine comminution of plant materials. First, we led a ball motion study to estimate the predominant mechanical stresses generated by each device. Two biomasses with contrasted physical properties were milled using three devices to achieve a target particle size of 20 μm. Milling times and process energy consumption were recorded, and the particle size distributions and specific surface areas of the ground powders were measured. The balls mills were then compared based on several indicators of energy efficiency, productivity and processing speed. The results show that the energy input is better utilized in mills that work by attrition or by combined impact and attrition.