Mechanism of the influence of relative humidity on coal mine dust light scattering and the correction of mass concentration inversion

Abstract

The relative humidity in underground mines fluctuates due to various factors, including geological conditions, ventilation, temperature, and dust suppression. As humidity increases, dust particles undergo hygroscopic expansion and aggregation, leading to changes in particle size and refractive index. Here, we established a humid aerosol light scattering measurement platform and introduced a relative humidity deviation factor to quantify the deviation in scattered light intensity per unit mass concentration of coal dust and rock dust under different humidity conditions. Under high-humidity conditions, the scattering intensity of coal dust decreases by about 30 %. In contrast, Rock dust, however, exhibits an ∼8.7 % increase due to hygroscopic growth, yet the overall relative humidity deviation factor remains approximately 0.789. Given this divergence, we revealed the mechanism by which the coupling of relative humidity and chemical composition affects the light scattering behavior of mine dust. Exponential fitting (with R² = 0.981 and R² = 0.965) and polynomial fitting (with R² = 0.995 and R² = 0.993) were performed for the correction coefficients of scattered light intensity and the particle size growth functions of coal dust and rock dust under different humidity conditions. The experimental results indicate that by constructing a dynamic humidity correction model to adjust the inversion of dust mass concentration, the relative measurement error of the sensor for dust mass concentration under conditions of medium or high humidity can be reduced to less than 10 %. This represents a novel approach for the accurate detection of dust in mines.