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Insights into the structures of multiphase flow gained with tomographic instrumentation

Insights into the structures of multiphase flow gained with tomographic instrumentation. B.J. Azzopardi Process and Environmental Engineering Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom. Team.

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Insights into the structures of multiphase flow gained with tomographic instrumentation

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  1. Insights into the structures of multiphase flow gained with tomographic instrumentation B.J. AzzopardiProcessand Environmental Engineering Division, Faculty of Engineering, University of Nottingham,University Park, Nottingham, NG7 2RD, United Kingdom

  2. Team • Dr LokmanAbdulkareem; Dr Valente Hernandez Perez; Dr SafaSharaf; Dr MukhtarAbdulkadir; Dr Keith Jackson; Professor AbdulwahidAzzi (Visiting Research Fellow); Dr Chris Pringle (University of Bristol) From HZDR (Rossendorf) • Dr UweHampel;Dr Marco da Silva; Mr Sebastian Thiele; Plus many others From Atout Limited • Dr Andy Hunt

  3. Contents • Instrumentation • Wire Mesh Sensor • Electrical Capacitance Tomography • Comparison and testing (WMS vs ECT; WMS vs gamma; WMS vs Level swell) • Structures revealed in gas/liquid flow • Effect of pipe diameter • Spherical cap bubbles and wisps • Effect of inclination • Structures revealed in gas/solids flow • Flow facilities • Mass flow accuracy/Fluctuations/Generalisation of frequency trends • Implications on flow pattern

  4. Permittivity wire mesh tomography - principle Gas Voltage t e Current t Oil

  5. Electrical Capacitance Tomography Based on 8 or 12 external electrodes, the capacitance between pairs of which is measured in a rapid sequence

  6. ECT: How does it work? • PrinciplePermittivity distribution = Imaging parameter Capacitance measurements Image • Operations • Calibration: [C] = [S]  [] • Computation of pseudo inverse [S]* • Capacitance vector collection and imaging [ ] = [S]*  [C] The velocity profile is then derived from the concentration profiles using correlation techniques. As the concentration and velocity profiles, are now known, the flow rate can be calculated directly using the fundamental equation: Q(t) = ∫Co(s) . V(s) dS

  7. WMS/ECT comparison Simultaneous measurements made with air/silicone oil R5000 ECT R200 also tested Azzopardi, B.J. Abdulkareem, L.A., Zhao, D., Thiele, S., da Silva, M.J., Beyer, M., Hunt, A., “Comparison between Electrical Capacitance Tomography and Wire Mesh Sensor output for air/silicone oil flow in a vertical pipe”, Ind. Eng. Chem. Res.,Vol. 49, 2010, pp 8805-8811. Hunt, A. Abdulkareem, L.A. and Azzopardi, B.J., Measurement of Dynamic Properties of Vertical Gas-Liquid Flow, 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 Excellent agreement

  8. Simultaneous traces displaced Example from slug flow

  9. Simultaneous traces displaced Lack of exact overlap due to variation in individual bubble velocity

  10. Comparison of WMS/Gamma S. Sharaf, M. da Silva, B.J. Azzopardi, U. Hampel, C. Zippe, M. Beyer, Comparison Between Wire Mesh Sensor Technology And Gamma Densitometry, Meas. Sci. Tech. Vol. 22, 2011, 104019 (13 pp).

  11. WMS/Level swell comparison Run in bubble column mode, i.e., zero liquid flow rate Level swell is the increase in volume induced by bubbles. Measure liquid only height and two-phase height Experiments in 127 mm column with air/silicone oil

  12. Grid effect on bubbles

  13. Outputof WMS/ECT Comparison between contours of phase distribution taken simultaneously with both Wire Mesh Sensor and Electrical Capacitance Tomography. Superficial velocities: liquid = 0 m/s and gas = 1.4 m/s. a- WMS b- ECT a) Bubbly flow b) Slug flow

  14. Outputof WMS/ECT Superficial velocity Gas =0.15-2.38 (m/s) Liquid = 0.1 (m/s) Axial slice image 0.47 0.15 2.83 Bubbly slug Bubbly slug churn churn

  15. Air/water Liquid superficial velocity = 0.25 m/s Integral view Slice across diameter

  16. Air/silicone oil Liquid superficial velocity = 0.25 m/s Integral view Slice across diameter Szelinski, L., Abdulkareem, L.A., da Silva, M.J., Thiele, S., Beyer, M., Lucas, D., Hernandez Perez, V., Hampel, U., Azzopardi, B.J., Comparative study of gas-oil and gas-water two-phase flow in a vertical pipe, Chemical Engineering Science vol. 65,2010, pp 3836-3848.

  17. Bubble size distributions • Based on Cross-sectional area Volume

  18. Effect of different liquids

  19. Size resolved void fraction

  20. Movies 127 mm 67 mm Gas superficial velocity (m/s) 3 5.7 Gas momentum (rgugs2) 32.4 39 Liquid superficial velocity = 0.25 m/s in both cases

  21. New structures revealed Compare with X-ray photograph taken in 1965 Hernandez Perez, V., Azzopardi, B.J., Kaji, R., da Silva, M.J., Beyer, M., Hampel, U., “Multiple levels of structures in vertical gas-liquid pipe flow revealed by Wire Mesh Sensor studies”, International Journal of Multiphase Flow, vol. 36, 2010, pp 908-915.

  22. 90 º 80 º 60 º 45º 30 º 0 º Effect of inclination 0 º

  23. Effect of inclination on bubble size distribution

  24. Flow patterns seen (ECT) Courtesy of Dr Andy Hunt (Atout Process Limited)

  25. Link between frequency trend and flow pattern Courtesy of Dr Andy Hunt (Atout Process Limited)

  26. Classification map of Geldart showing present particles

  27. Flow facility –dense phase conveying To receiver mounted on load cells • Pulverised (ground) coal • Density = 1322 kg/m3 • Bulk density = 537 kg/m3 • Mean diameter = 60 mm ~8 m ~8 m

  28. Mass flow measurement For a steady flow – mass flow rates (kg/s) • Load cells = 1.2775 ECT = 1.284 Also tracked flow with oscillation Azzopardi, B.J., Jackson, K., Robinson, J.P., Kaji, R., Byars, M., Hunt, A., Fluctuations in dense phase pneumatic conveying of pulverised coal measured using electrical capacitance tomography, Chem. Eng. Sci., vol. 63, 2008, pp 2548-2558.

  29. Time resolved mass flow rate Expanding the time scale

  30. 3-D animation

  31. More information

  32. More complex oscillations Not unique similar behaviour seen in another run One oscillation has a frequency (~0.1 Hz) an order of magnitude smaller than the other (~1 Hz)

  33. More complex oscillations One oscillation has a frequency (~0.1 Hz) an order of magnitude smaller than the other (~1 Hz)

  34. Lower frequency oscillations From mass in package, bulk density and dimensions of bottom of hopper, it appears possible that these pulses are caused by slip/stick in feed hopper outlet

  35. Void fraction/PDF Churn Annular 12.5 m/s 28 m/s 47 m/s

  36. Flow pattern map Flow pattern maps of Sekoguchi & Mori, Bi et al. Data of present work (closed symbol) and Du et al. (open symbols)

  37. Correlation of frequency

  38. Conclusions • After careful testing, we have been applying electrical tomography instrumentation • This has identified flow behaviour in gas/liquid and gas/solids flows. • We continue to apply the techniques to these flow, to bubble columns, fluidized beds and oil/water flows • It also aid our work on volcanoes (gas/very viscous liquid flows)

  39. 300 Pa s silicone oil

  40. Fluidized bed -Cine film from ECT Minimum fluidizing velocity = 0.78 m/s Plane 1 Plane 2 Gas superficial velocity 1.05 m/s, Sampling frequency 2000 fps

  41. Time series of cross-sectionally averaged void fraction Plane 1 Plane 2 Gas superficial velocity in m/s 1.18 1.32 Sampling frequency = 2000 Hz

  42. Schematic of fluidized bed rig • Polyethylene • Density = 900 kg/m3 • Bulk density = 537 kg/m3 • Mean diameter = 3 mm

  43. Positions of ECT electrodes Plane 2 Plane 1

  44. Variation of void fraction with gas superficial velocity Effect of sampling rate. Plane 1

  45. Probability Density Function of void fraction Effect of gas superficial velocity. Plane 2

  46. Power Spectral Densities - plane 1 Sampling frequency equal to 2000 Hz Azzi, A., Azzopardi, B.J., Abdulkareem, L.A., Hilal, N, Hunt, A., Study of fluidisation using Electrical Capacitance Tomography, 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

  47. Instrumentation • Wire Mesh Sensor • Electrical Capacitance Tomography • Comparison and testing • WMS vs ECT • WMS vs gamma • WMS vs Level swell

  48. Wire Mesh Sensor Acquisition Unit Flow Wire Mesh Sensor Sensor da Silva, M.J., Thiele, S., Abdulkareem, L., Azzopardi, B.J. & Hampel, U. High-resolution gas-oil two-phase flow visualization with a capacitance wire-mesh sensor.. Flow Measurement and Instrumentation, Vol 21, pp 191-197, (2010).

  49. Time resolved mass flow rate

  50. Characteristic frequency Not frequency of rotary feeder

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