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This paper shows the results of a collaborative project in which four different laboratories have carried out complementary characterization tests on samples of the same set of lignocellulosic biomass materials with the objectives of better understanding their properties and identifying any critical features of the different characterization procedures. Three different types of material were used as model biomasses: 1) Scots pine wood chips, as an example of a coarse and flaky particulate biomass with some elastic properties; 2) chopped straw of reed canary grass as a nesting biomass having long and flaky fibers; 3) Scots pine wood powder as a fine particulate with elastic and cohesive properties. Particle size and shape analyses were carried out with; calipers, 2D image analysis, 3D image analysis (ScanChip) and through mechanical sieving. Applications and validity limits of each of these techniques are evaluated and discussed. The flow function and internal friction 2 were determined with a Schulze ring shear tester, a Brookfield powder flow tester and a large ring shear tester. No significant differences in the results generated by these shear testing techniques were found. Wall friction measurements were carried out with a Schulze ring shear tester; a Brookfield powder flow tester; a large Jenike shear tester and a Casagrande shear box. Results, in this case, showed significant differences with a higher wall friction coefficient obtained with the larger shear cell. Additionally, tensile strengths of biomass materials were measured by the use of a novel measurement technique. Arching tests were carried out in a pilot scale plane silo with variable hopper geometry and results were compared with those predicted by applying the Jenike procedure and a modified procedure which assumed tensile strength was the controlling material property (rather than unconfined yield strength). Finally, safety of handling and storage was assessed by carrying out explosion tests on dusts from Scots pine and reed canary grass.KEYWORDS: lignocellulosic biomass, particle size, particle shape, flowability, arching, explosion RESEARCH HIGHLIGHTS: Suitable test methods were classified for three biomass classes  Different particle sizing methods give a wide range of results  Shear tests do not discriminate flowability differences between the biomass classes  Arching behavior depends more on tensile strength than on compressive strength  Scots pine and reed canary grass dusts are flammable

A low cost powder flowability tester for industry has been developed at The Wolfson Centre in collaboration with Brookfield Engineering and four food manufacturers: Cadbury, Kerry Ingredients, GSK and United Biscuits. Anticipated uses of the tester are primarily for quality control and new product development, but it can also be used for silo design.This paper presents the preliminary results from Round Robin trials undertaken with the PFT using the CRM -116 limestone standard test material. The mean flow properties have been compared to published data found in the literature for the other shear testers.

Biomass powders are often cohesive, have low bulk density and poor material flow characteristics which causes interruptions and variations in feeding systems. In this study, a range of biomasses -commercial charcoal, torrefied Norway spruce stem wood, non-treated Norway spruce stem wood, and reed canary grass -was milled (screen size: 1 mm) using two different milling methods; cutting mill and hammer mill, to form eight types of biomass powders. Powders were analyzed for loose density, Hausner ratio, compression ratio, angle of repose and for size and shape distributions. Size and shape were determined by mechanical sieving and optical particle size and shape analysis. Additionally, yield loci and wall yield loci were determined through standard bulk solids testing methods. Screw feeding properties of the eight biomass powders were determined by feeding the materials in a twin screw feeder -at constant rpm and at a constant feeding rate of 1 kg/h. Correlation analysis and principal component loadings were used to describe relations between material properties and feeding characteristics. When materials were fed at a constant rpm, feeding variability was closely correlated to the powders' angle of repose (long time step) and Hausner and compression ratio (short time step).

Berry , An investigation into the flowability of fine powders used in pharmaceutical industries. Ptec (2017),