Brown coal dewatering
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Brown Coal Dewatering. “Materials Grand Challenges” Melbourne Materials Institute, 20 August 2012 Anthony Stickland, Robin Batterham, Antoinette Tordesillas and Peter Scales. Background. Victorian Brown Coal www.dpi.vic.gov.au. Victorian Brown Coal is very wet

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Brown Coal Dewatering

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Brown coal dewatering

Brown Coal Dewatering

“Materials Grand Challenges”

Melbourne Materials Institute, 20 August 2012

Anthony Stickland, Robin Batterham,

Antoinette Tordesillas and Peter Scales


Background

Background

Victorian Brown Coal

www.dpi.vic.gov.au

  • Victorian Brown Coal is very wet

  • High moisturecosts energy to remove

    • Reduces net calorific value

    • Increases CO2 / 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


Structure of coal

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

100 nm

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)


Dewatering options

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


Combined shear compressive loadings

Combined Shear + Compressive Loadings

  • Many SLS processes involve combined loadings

  • Generally enhances operational performance

  • Need to understand particulate network behaviour under combined loads

Compression

+ Shear

Compression

Shear


New experimental techniques

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)


New microstructural understanding

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

Photoelasticbirefringent patterns of force chains

(R. Behringer, Duke University)


New technology

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)


Summary discussion points

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

(A Innocenzi, International Power)

(courtesy A. Innocenzi, International Power)


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