Characteristics of Dust in Ventilation Air from Hard Coal Mine Exhaust Shafts and Its Implications for VAM Utilisation Technologies

Methane contained in ventilation air from hard coal mines (VAM, ventilation air methane) represents a significant environmental and technological challenge due to very large volumetric airflow rates and low methane concentrations. The feasibility of applying VAM utilisation technologies depends not only on methane concentration but also on ventilation air quality, including dust content, humidity and gaseous contaminants. This paper presents an analysis of dust in air emitted from hard coal mine exhaust shafts in Poland and Romania, based on measurement data and studies conducted within the ProVAM project. The dataset includes 155 dust concentration measurements from 24 main fan stations, supplemented by analyses of dust composition and particle size distribution for selected shafts. The results show that, in the analysed dataset, most reported mean total dust concentrations were within the range of approximately 1–3 mg/Nm3, with considerable temporal variability. Particle size analysis performed for two selected Polish shafts showed that fine particles dominate in terms of number, whereas coarser particles contribute disproportionately to the volume weighted distribution and, approximately, to the mass contribution. The results are compared with the requirements of VAM oxidation technologies, particularly regenerative thermal oxidisers (RTOs), for which selected commercial systems specify technical reference values for dust concentration in the supplied air. In many analysed cases, particularly where dust was dominated by incombustible mineral matter, air pre-treatment should be considered before ventilation air is introduced into VAM utilisation systems. A comparative assessment of dry dust-removal methods is also conducted, including gravitational, inertial, centrifugal, filtration and electrostatic devices. Considering the operating conditions of mine ventilation air, including high airflow rates, high humidity and dust characteristics, cyclone battery systems are discussed as a technically justified candidate for the primary dust-removal stage, while their final applicability requires site specific verification. The results indicate that dust removal should be considered an integral element in the design of methane emission reduction systems based on VAM utilisation technologies.