Investigation of the settling dynamics and behaviour of PM2.5 and PM1.0 present in coal dusts in controlled environmental conditions

Fine particulate matter (PM 2.5 and PM 1.0 ) is a major pollutant in coal processing industries. These particles exhibit Brownian motion but do not remain suspended indefinitely, settling over time. This study investigates the deposition characteristics of PM 2.5 and PM 1.0 in a confined setup, analysing how concentration diminishes under varying initial conditions. The experimentation involved introducing 250 mg, 500 mg, 750 mg and 1 g coal dust into a chamber of size (100 cm × 30 cm × 40 cm), where calibrated PMS7003 sensors recorded the concentration level of PM 1 and PM 2.5 at four different levels, viz. at ground levels, 30 cm, 60 cm and 90 cm height. The analysis showed that the concentration depletion rate due to deposition is governed by diffusion deposition and coagulation. A universal equation has been developed for varying initial concentration and lapsed time. Coagulation is mostly observed in high concentration. Deposition rate constant reduce with increase in initial concentration. At low initial concentration 50 percent concentration reduction time is 15–16 min for both PM 1 and PM 2.5 which increases at higher concentration. Same pattern is observed for 90 percent concentration reduction time. Time to reach the permissible limit as per Indian National Ambient Air Quality Standards increases gradually from 35 min to 2.5 h. • PM 1 and PM 2.5 decay faster initially due to coagulation at high concentrations. • Concentration drop slows at higher initial concentration due to steric hindrance. • PM levels show steady 50 % & 90 % reduction times, increasing at higher concentrations.