High-precision measurement of respirable coal dust mass concentration: A dual-wavelength complementary laser optical sensor approach based on Mie scattering

Abstract

To address the shortcomings of detection inaccuracy at low concentrations and poor stability in current coal mine respirable dust detectors, a portable, high-precision, dual-wavelength dust sensor for mining applications was developed. Mie scattering theory of irregular particles was used to establish a light scattering model for polydisperse respirable coal dust. Numerical simulations were conducted using MATLAB and COMSOL. The effects of particle size, incident wavelength, and scattering angle on the distribution of the scattered light intensity were analyzed using standard spherical coal dust as an approximation. Experimental validation was performed using respirable coal dust samples. From these analyses and experiments it was determined that laser wavelengths of 450 and 637 nm and a scattering angle range of 12–28° were optimal. A custom-designed annular receiving structure, laser triggering timing circuit, and multi-stage amplification circuit were developed. The optical structure was adjusted and optimized, and a three-dimensional modeling of the sensor was developed, followed by component selection and assembly. Using the experimental setup, coefficient calibration and error detection were performed. The results showed that at dust concentrations of 5, 20, and 100 mg/m³, the sensor's short-term average measurement errors were 2.30 %, 3.60 %, and 4.25 %, respectively. Compared with other sensors, the developed sensor demonstrated superior accuracy and stability, and overcame the limitations of single-wavelength detectors of respirable dust. This work provides a novel approach and methodology for accurate dust detection in coal mines.