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Non-invasive Study of Powder Blending Using NIR Spectrometry and Acoustic Emission

Non-invasive Study of Powder Blending Using NIR Spectrometry and Acoustic Emission. L.J. Bellamy, A. Nordon, D. Littlejohn CPACT, University of Strathclyde, Glasgow, G1 1XL. Luke Bellamy CPACT Strathclyde. Ideal Mixing Profile. Initial Mixing Phase. “over mixing”. Re-mixing. Segregation.

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Non-invasive Study of Powder Blending Using NIR Spectrometry and Acoustic Emission

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  1. Non-invasive Study of Powder Blending Using NIR Spectrometry and Acoustic Emission L.J. Bellamy, A. Nordon, D. Littlejohn CPACT, University of Strathclyde, Glasgow, G1 1XL Luke Bellamy CPACT Strathclyde

  2. Ideal Mixing Profile Initial Mixing Phase “over mixing” Re-mixing Segregation Composition Variance Mixing Time Luke Bellamy CPACT Strathclyde

  3. Experimental Plan Binary systems have been mixed to determine the effect of the physical properties of the particles and mixer parameters on mixing • Microcrystalline cellulose as bulk material • Second components chosen to display variation in key physical properties • Mixing monitored with non-invasive techniques Luke Bellamy CPACT Strathclyde

  4. Selected Materials Luke Bellamy CPACT Strathclyde

  5. Glass vessel Laboratory Scale Blending • Vessel and impeller scaled down from process unit used at GlaxoSmithKline, Ware,UK • Glass upper section allows non-invasive optical measurements • Mixing speed ranges from 0-125 rpm • Contained in cabinet with extraction Luke Bellamy CPACT Strathclyde

  6. Near Infrared Spectrometry • Zeiss Corona 45 NIR • Process instrument designed for non-invasive reflectance measurements • 128 element InGaAs array detector • Operated in absorbance mode • Spectra acquired every 0.5 seconds, 10 co-added scans with 32 ms integration • Reference was reflective white paper inside the mixing vessel Luke Bellamy CPACT Strathclyde

  7. Zeiss Corona 45 NIR Aspect software used to acquire spectra through PC link Luke Bellamy CPACT Strathclyde

  8. Passive Acoustic Emission Spectrometry • Agilent Infiniium oscilloscope • Broadband transducer 150 – 750 kHz • Signal acquired with 2 mHz sample rate and 8 k points every 2 seconds • Data imported into Matlab and signal, s, converted to power spectra using: Luke Bellamy CPACT Strathclyde

  9. Broadband transducer Linked directly to oscilloscope Agilent Infiniium oscilloscope Data acquired in C-program using GPIB link Luke Bellamy CPACT Strathclyde

  10. Mixing Procedure • Acoustic transducer coupled to glass • Mass of avicel added to mixer • NIR instrument positioned 13 mm from glass • Second compound added after 300 s through sliding window in top of cabinet • Mixing initially monitored for 7200 s to test stability of the mixed powder to segregation • Mixing generally stopped after 1200 s Luke Bellamy CPACT Strathclyde

  11. Corona must be positioned 13 mm from the vessel for optimum performance Transducer coupled with silicone sealant and held in place with tape Luke Bellamy CPACT Strathclyde

  12. First Derivative Spectra: Mixing Avicel and Aspirin 8956 cm-1 6086 cm-1 Luke Bellamy CPACT Strathclyde

  13. First Derivative NIR Absorbance at 8956 cm-1 Averaged mixing profile for mixing avicel and aspirin Luke Bellamy CPACT Strathclyde

  14. NIR Mixing Profiles at 8956 cm-1 Aspirin concentration varied at 75 g avicel fill and 50 rpm Luke Bellamy CPACT Strathclyde

  15. Monitor Mixing Using % RSD Mixing 10 g aspirin into 75 g avicel at 50 rpm Monitor % RSD of NIR signal at 8956 cm-1 Luke Bellamy CPACT Strathclyde

  16. Summed Passive Acoustic Power Spectra 75 g avicel fill with 10 g aspirin at 50 rpm Luke Bellamy CPACT Strathclyde

  17. Acoustic Mixing Profile 75 g avicel fill with 10 g aspirin at 50 rpm

  18. Mixing Experiments • Vessel properties investigated ─ Fill level (65, 75, 85 and 90 g avicel) ─ Impeller speed (25, 50, 75,100 and 125 rpm) • Particle properties investigated ─ Shape (spherical, needles, granular, cubic) ─ Concentration (5, 10, 20 and 25 g aspirin) ─ Particle size (<251, 251-500 and 500-853 µm) ─ Density (1.1 – 2.2 g/cm-3) Luke Bellamy CPACT Strathclyde

  19. Effect of Density and Shape in NIR Profile Povidone 30 Spherical 1.1 g cm-3 Povidone 90 Platelets 1.1 g cm-3 Potassium chloride cubic 2.2 g cm-3 Aspartame Needles 1.35 g cm-3 Luke Bellamy CPACT Strathclyde

  20. Effect of Particle Size - Citric Acid (static) Citric acid NIR spectra measured through glass beaker Luke Bellamy CPACT Strathclyde

  21. Effect of Particle Size - Citric acid (mixing) 75 g avicel fill with 7.5 g citric acid at 50 rpm, NIR Luke Bellamy CPACT Strathclyde

  22. Effect of Size at Different Concentrations: NIR Monitored at 6814 cm-1 75 g avicel fill, three size ranges, 50 rpm Luke Bellamy CPACT Strathclyde

  23. Effect of Size at Different Concentrations: Acoustics 75 g avicel fill, three size ranges, 50 rpm Luke Bellamy CPACT Strathclyde

  24. Effect of Impeller Speed and Shape: NIR 75 g avicel fill, 10g addition

  25. Selected Materials Luke Bellamy CPACT Strathclyde

  26. Effect of Impeller Speed : Acoustics 75 g avicel fill, 10g addition

  27. Conclusions • Both NIR and acoustic spectrometry can be used to monitor mixing processes non-invasively • NIR and passive acoustics are sensitive to particle size and concentration • Some regions of NIR spectra more sensitive to particle size variations • Shape and density seem to give variations in NIR mixing profile and mix at different rates • Impeller speed variations may lead to composition changes from NIR data Luke Bellamy CPACT Strathclyde

  28. Future Work • Mix multi-component systems • Tumble blender • Use pre-amps and filters to optimise acoustic signal detection • Fluorescence spectrometry will be investigated in near future Luke Bellamy CPACT Strathclyde

  29. Acknowledgements • Dr David Rudd and Dr Paul Frake, GlaxoSmithKline, Ware, UK • Centre for Ultrasonic Engineering (CUE) • CPACT and University of Strathclyde Luke Bellamy CPACT Strathclyde

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