International Scientific Journal


The goal of this research is to establish the applicability of an electrostatic measuring technique for monitoring the quality of a coal-milling process in direct-firing systems. Such systems are used in large steam boilers fired with low-rank coal where the pulverized coal is transported pneumatically from the mills to the burner nozzles via ducts with large cross-sections. The electrostatic measuring method, in connection with intrusive rod-type sensors, was studied because it provides good spatial sensitivity and cost effectiveness. A laboratory test rig was constructed, where the pulverized coal carried by ambient air was employed for the experiments emulating the pneumatic transport of coal particles in direct-firing systems. The test rig enables an extensive variation of the most influential parameters, like the mass-flow, the velocity and the size of the particles. A linear, multi-regression analysis of the results of the experiments was carried out and the appropriate regression model enabling a determination of the mean diameter of the particles using the electrostatic signal was chosen. Based on the results of the study the electrostatic measuring technique can be used for monitoring the size of pneumatically transported particles. The appropriate regression model needs to be chosen for each particular application to describe the dependency of the acquired electrostatic signal on the influential parameters of the pneumatic transport.
PAPER REVISED: 2019-08-08
PAPER ACCEPTED: 2019-08-13
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THERMAL SCIENCE YEAR 2020, VOLUME 24, ISSUE Issue 6, PAGES [4061 - 4073]
  1. Zhang, J., Air-Solids Flow Measurement Using Electrostatic Techniques, In Electrostatics, Canbolat, H., (Ed.), InTech, Rijeka, Croatia, 2012, pp. 61-80
  2. Gajewski, J. B., Electrostatic Nonintrusive Method for Measuring the Electric Charge, Mass Flow Rate, and Velocity of Particulates in the Two-Phase Gas-Solid Pipe Flows - Its Only or as Many as 50 Years of Historical Evolution, IEEE Trans. Ind. Appl., 44 (2008), 5, pp. 1418-1430
  3. Qian, X., et al., Quantitative characterization of pulverized coal and biomass-coal blends in pneumatic conveying pipelines using electrostatic sensor arrays and data fusion techniques, Meas. Sci. Technol., 23 (2012), 8, pp. 1-13
  4. Xu, C., et al., Investigations into sensing characteristics of electrostatic sensor arrays through computational modelling and practical experimentation, J. Electrostat., 70 (2012), 1, pp. 60-71
  5. Rahmat, M. F., Kamaruddin, N. S., An electrodynamic sensor for electrostatic charge measurement, Int. J. Smart Sens. Intell. Syst., 2 (2009), 2, pp. 200-212
  6. Krabicka, J., Yan, Y., Finite-element modeling of electrostatic sensors for the flow measurement of particles in pneumatic pipelines, IEEE Trans. Instrum. Meas., 58 (2009), 8, pp. 2730-2736
  7. Jurjevčič, B., et al., The Characterization of Pulverized-Coal Pneumatic Transport Using an Array of Intrusive Electrostatic Sensors, IEEE Trans. Instrum. Meas., 64 (2015), 12, pp. 3434-3443
  8. Živković, G., et al., Numerical simulation of the influence of stationary louver and coal particle size on distribution of pulverized coal to the feed ducts of a power plant burner, Thermal Science, 13 (2009), 4, pp. 79-90
  9. Belošević, S. V., et al., Modeling of pulverized coal combustion for in-furnace NOx reduction and flame control, Thermal Science, 21 (2017), 3, pp. S597-S615
  10. Jurjevčič, B., et al. A Surveillance of direct-firing system for pulverized-coal using statistically treated signals from intrusive electrostatic sensors, Journal of Mechanical Engineering, 63 (2017) 4, pp. 265-274
  11. Klinzig, G. E., A review of pneumatic conveying status, advances and projections, Powder Technology, 333 (2018), pp. 78-90
  12. Taghavivand, M., et al., Study of electrostatic charging of single particles during pneumatic conveying, Powder Technology, 355 (2019), pp. 242-250
  13. Saleh, K., et al., Relevant parameters involved in tribocharging of powders during dilute phase pneumatic transport, Chemical Engineering Research and Design, 89 (2011), pp. 2582-2597
  14. Matsusaka, S., Masuda, H., Simultaneous measurement of mass flow rate and charge-to-mass ratio of particles in gas-solids pipe flow, Chem. Eng. Sci., 61 (2006), 7, pp. 2254-2261
  15. Carter, R. M., et al. On-line measurement of particle size distribution and mass flow rate of particles in a pneumatic suspension using combined imaging and electrostatic sensors, Flow Meas. Instrum., 16 (2005) 5, pp. 309-314
  16. Zhang, J., et al., Analyses of Characteristics of Ring-Shaped Electrostatic Meter, Chem. Eng. Commun., 197 (2009), 2, pp. 192-203
  17. Despotović, Ž., V., Some Experiences in the Exploitation of Triboelectric Sensors for Measuring Concentration of Particulate Matter on Thermal Power Plants, Infoteh-Jahorina, 12 (2013), pp. 1118-1124
  18. Qian, X., et al., Measurement of the Mass Flow Distribution of Pulverized Coal in Primary Air Pipes Using Electrostatic Sensing Techniques, Proceedings, 2nd IEEE International Instrumentation and Measurement Technology Conference, Taipei, Thailand, 2016, pp. 1-5
  19. Coulthard, J., et al., Online pulverized-fuel monitoring at Methil power station, Power Engineering Journal, (1997), pp. 27-30
  20. Rodrigues, M. V., et al., Measurement of the Electrostatic Charge in Airborne Particles: II-Particle Charge Distribution of Different Aerosols, Brazilian Journal of Chemical Engineering, 23 (2006), pp. 125-133
  21. Zhang, J., et al., On-line Continuous Measurement of Particle Size Using Electrostatic Sensors, Powder Technology, 135-136 (2003), pp. 164-168
  22. Petrović, V. S., et al., The possibilities for measurement and characterization of diesel engine fine particles, Thermal Science, 15 (2011), pp. 915-938
  23. Woodhead, S. R., et al., Electrostatic sensors applied to the measurement of electric charge transfer in gas-solids pipelines, J. Phys.: Conf. Ser., 15 (2005), pp. 108-112
  24. Peng, L., et. al., Characterization of electrostatic sensors for flow measurement of particulate solids in square-shaped pneumatic conveying pipelines, Sensors Actuators A Phys., 141 (2008), 1, pp. 59-67
  25. Soong, T. T., Fundamentals of Probability And Statistics for engineers, Wiley, New York, USA, 2004
  26. Hurvich, C. M., Tsai, C. L., Regression and time series model selection in small samples, Biometrika, 76 (1989), 2, pp. 297-307
  27. ASTM - D197 − 87, ‘Standard Test Method for Sampling and Fineness Test of Pulverized Coal', 2012
  28. Nifuku, M., Katoh, H., A study on the static electrification of powders during pneumatic transportation and the ignition of dust cloud, Powder Technol., 135-136 (2003), pp. 234-242
  29. Kuštrin, I., Lenart, J., Electrostatic Sensors on a Lignite - Fired Boiler for Continuously Monitoring the Distribution and Velocity of Pulverized Coal, VGB Powertech, 95 (2015), 7, pp. 33-37
  30. Saleh, K., et al., Relevant parameters involved in tribocharging of powders during dilute phase pneumatic transport, Chem. Eng. Res. Des., 89 (2011), 12, pp. 2582-2597
  31. Gulič, M., et al., Proračun ventilatorskih mlinova, (Fan-impact mill calculations - in Serbian language), Udruženi, Belgrade, Serbia, 1982
  32. N. Degiuli, N., Barbalic, N., Marijan, G., Causes of Sampling Measurement Uncertainties when Determining the Particle Concentration in a Gaseous Environment, J. Mech. Eng., 53 (2007), pp. 297-309
  33. Joint Committee for Guides in Metrology, JCGM 100:2008 Evaluation of measurement data - Guide to the expression of uncertainty in measurement, corrected version 2010, 2010

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