An improved charge-sensing method for dust concentration monitoring based on active charging

To address the issues of significant errors, which may exceed permissible limits, and a high lower detection limit in traditional charge-sensing dust concentration monitoring methods for low-concentration dust (≤50 mg/m³), this study proposes an improved method based on active charging. An analysis of the working principles of traditional methods reveals their shortcomings: low electrostatic charge on dust particles, susceptibility to environmental interference, and unstable charge polarity, all of which complicate signal acquisition and processing. To overcome these challenges, active charging is introduced to increase the charge level and stabilize the polarity of dust particles. A mathematical model of the dynamic induced charge for the improved method is derived, and a charge-sensing monitoring unit employing active charging is developed. Through laboratory experiments, the signal-to-noise ratio (SNR) characteristics of the monitoring unit are investigated for aluminum dust, coal dust, flour, and cement dust under various charging voltages and low dust concentration conditions. The reasons for the observed variations are analyzed in depth. The minimum charging voltage needed to achieve the required SNR is determined, along with its corresponding lowest detectable dust concentration. Experimental validation demonstrates that, under the minimum charging voltage condition, the improved monitoring unit achieves a lower detection limit of 5.5 mg/m³ that satisfies standard error requirements, which is at least 4.5 mg/m³ lower than that of traditional methods. In the low-concentration range of 5.5 mg/m³-50.0 mg/m³, the monitoring errors for aluminum dust, coal dust, flour, and cement dust all comply with the standard requirements. Compared with the no-charging condition, the monitoring errors under the 20 kV charging condition are reduced by 6.4%, 6.1%, 5.4%, and 5.3% for the four types of dust, respectively.