Pilot scale production of fuel pellets from waste biomass leaves: Effect of milling size on pelletization process and pellet quality

Abstract

This work investigates the effect of biomass milling size on pelletization process and pellet quality, using garden waste (a non-woody biomass feedstock). Three different milling sizes were considered, viz. ‘as received’ (>25.4 mm), coarse (25.4 mm), and fine (6.25 mm) at a moisture content of around 10% and a die size of 15 mm. The particle size distribution plots showed a significant difference in ‘median particle size diameter’ (D50) for all three cases. Nominal changes in pellet quality parameters (density, dimension, and durability) were observed during pilot scale pelletization with different milling sizes. However, the results showed an increased throughput capacity (29.5 to 60 kg h−1) with decrease in milling size from 'as received' to fine. In addition, the wet disintegration method was performed to analyze the internal particle size distribution of pellets. The results revealed that the difference in D50 values for the internal particle size of produced pellets was insignificant in above cases. Furthermore, the specific energy consumption value reduced from 141.2 to 100.2 kWh ton−1 by reducing biomass milling size from coarse to fine. The production cost reduced by 23% for fine feedstock as compared to coarse while producing pellets under given conditions.