31 / 2023-05-15 03:14:14

Effect of ambient relative humidity on particle filtration performance

relative humidity,dust pollution,particulate matter,filtration efficiency,hygroscopicity

Dust hazard is one of the main safety problems faced by mine employees. The development and application of various types of high-efficiency dust removal technologies is an important measure for the comprehensive management of mine dust. In recent years, filtration technology has been gradually promoted from surface industrial sites to underground working spaces due to its better purification effect on respirable dust. However, field applications show that the actual effect of dust filtration is easily influenced by the ambient humidity in underground coal mines. The impact of humidity on filtration efficiency is complex and multifactorial, requiring further precise experimentation and quantitative analysis to derive clearer patterns. Furthermore, it is crucial to delve into the underlying mechanism of how environmental humidity affects the filtration performance of particles, rather than solely describing experimental observations.

This study investigated the variation pattern and intrinsic mechanism of particle filtration performance with different ambient relative humidity (RH) through experimental methods. Hygroscopic sodium chloride (NaCl) particles and non-hygroscopic alumina (Al₂O₃) particles were used as experimental objects. Two types of particulate matter scales, nano and micron, were introduced in the experiments and fibrous materials were selected as filtration media. The purpose of this study is to clarify the effect of ambient relative humidity on the filtration effect for particulate matter. The variation laws of filtration resistance, filtration efficiency, and dust loading efficiency for dust particles under different ambient humidity were tested.

 The results indicate that the pressure drop increased linearly in filtering hygroscopic particles at low humidity (RH20% and 50%), and a sharp elevation in pressure drop occurred at high humidity (≥RH80%). Non-hygroscopic particles were less affected by variations in humidity, but the growth in pressure drop was more significant at saturation humidity (RH 100%). The initial filtration efficiency of the filter media was not sensitive to variations in the relative humidity in the environment, and it was not affected by differences in the moisture absorption capacity of the particles. The filtration efficiencies of sodium chloride and alumina particles of the same particle size measured at different humidity levels are close to each other. The initial efficiency of the filter media first decreased and then increased with increasing particle size. At a particle size of 100 nm, the measured filtration efficiency reached its lowest value of about 0.665 ± 0.01. The filtration efficiency for hygroscopic particles in the loading process was greatly affected by the relative humidity. When the relative humidity is lower than its own deliquescence point, the filtration efficiency increased slowly and continuously; after the relative humidity exceeded the deliquescence point, the filtration efficiency declined continuously with the particle deposition. For non-hygroscopic particles, their filtration efficiency in the loading process exhibited a slow growth trend under different relative humidity. After the particle deposition mass reached 15 g·m^-2, the efficiency growth rate at 100% relative humidity showed a large increase. In addition, variations in ambient humidity had a more significant effect on the filtration performance of nanoparticles than microparticles. The results of this research could provide guidance for the application and improvement of particulate matter filtration technology in mine dust control.