Engineering Properties of Paddy Stalk for Biomass Processing

Abstract

Paddy stalk is an agricultural residue with potential for use as a biomass feedstock, but its effective handling and processing depend on reliable engineering-property data. This study characterised the physical, bulk, flow, and frictional properties of whole and ground paddy stalk to support the design of biomass-processing equipment. Sixty stalk samples, comprising equal numbers of small, medium, and large stalks, were evaluated for length, width, thickness, geometric mean diameter, aspect ratio, and individual weight. Loose and tapped bulk densities, true density, porosity, Carr’s compressibility index, Hausner ratio, angle of repose, and coefficients of internal and external friction were also determined. Size reduction increased the loose bulk density from 76.97 ± 1.07 to 142.65 ± 9.87 kg m-3 and the tapped bulk density from 102.63 ± 2.48 to 185.24 ± 11.40 kg m-3. The ground material had a true density of 855.94 ± 0.83 kg m-3, a porosity of 0.83 ± 0.003, a Carr’s compressibility index of 23.01 ± 0.59, and a Hausner ratio of 1.29 ± 0.01. Grinding reduced the angle of repose from 46.60 ± 1.99° to 37.91 ± 0.53° and lowered the coefficients of internal and external friction. These findings indicate that size reduction improves packing and flow behaviour and provide design parameters for equipment used in conveying, feeding, storage, and densification of paddy stalk.