Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Brown Coal Dewatering “Materials Grand Challenges” Melbourne Materials Institute, 20 August 2012 Anthony Stickland, Robin Batterham, Antoinette Tordesillas and Peter Scales

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Background Victorian Brown Coal is very wet High moisturecosts energy to remove  Reduces net calorific value  Increases CO 2 / MW  “Dirty” moniker (it does burn clean…) Holy Grail for any processing of brown coal is Efficient Dewatering –Make brown coal into black coal at minimum cost and energy –Vast resource with large potential impact Victorian Brown Coal

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Structure of Coal 2-phase micro-porous sponge Solid network is continuous –Particulate gel held together by van der Waals, hydrogen bonding and electrostatics –Able to support a load and transmit pressure Fluid has both continuous and discrete parts –Must break structure to get water out TEM image of raw Loy Yang brown coal from McMahon, Snook and Treimer, ‘The Pore Structure in Processed Victorian Brown Coal’, J Colloid Interface Sci. 252, 177 – 183 (2002) 100 nm

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Dewatering Options Solid-Liquid Separation –Thermal dewatering Boiler flue gases Drying beds –Mechanical dewatering E.g. filtration Structure Breaking –Shear ‘Kneading’ –Hydrothermal reaction E.g. Exergen CHTD Structure Breaking with SLS –Mechanical/Thermal Expression Compression + heat Batch process, low throughput –Compression + Shear Modified High Pressure Grinding Rolls

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Combined Shear + Compressive Loadings Many SLS processes involve combined loadings Generally enhances operational performance Need to understand particulate network behaviour under combined loads Raked thickeners Belt press filters Cross-flow filters Lamella settlers Disc stack centrifuges Decanting centrifuges Suspension cracking Wall slip in rheometry Compression Shear Compression + Shear Compression + Shear

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council New Experimental Techniques Need to measure behaviour under shear and compression Requires novel experimental methods Shear using “vane-in- infinite-medium” geometry Compression in a filter or under a sediment bed E.g. ‘Vane-in-a-filter’ (H. Teo, The University of Melbourne)

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council New Microstructural Understanding Columns of particles bear most of the load in powders Breaking structure necessitates shear to buckle the column ‘Confined Force Chain Buckling’ model Link microstructure and macroscopic behaviour Photoelastic birefringent patterns of force chains (R. Behringer, Duke University)

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council New Technology Modified High Pressure Grinding Rolls (HPGR) Compression at nip Shear through different rotational rates Perforated rolls give short Solid-Liquid separation pathway Continuous, high Throughput (H. Teo, The University of Melbourne)

Particulate Fluids Processing Centre A Special Research Centre of the Australian Research Council Summary / Discussion Points Structure of Brown Coal Dewatering of Brown Coal –Mechanical and thermal options Combined Compression and Shear –Measuring constitutive behaviour Confined Force Chain Buckling –A microstructural description of suspension rheology Modified HPGR –High throughput processing (courtesy A. Innocenzi, International Power) (A Innocenzi, International Power)