Wall loss rates of polydispersed aerosols in a stirred vessel were studied theoretically and experimentally. A formula for the polydispersity factor of the wall loss rate was derived using the moment method of log-normal size distribution and compared with numerical calculations. The representative theory of Crump and Seinfeld (1981) was used as the wall loss rate of monodispersed aerosols in which the Brownian diffusion, the turbulent eddy diffusion, and the gravitational settling are included as wall loss mechanisms. The results of the analysis show that the wall loss rate of a polydispersed aerosol is substantially higher than that based on a monodispersed size distribution model if the particle size distribution can be represented reasonably well by a log-normal function. The existing diagram showing the loss rate as a function only of the particle size was expanded to include the polydispersity effects. Experimental measurements of particle wall loss rate were performed by observing the time-dependent changes in particle number concentration for various stirring intensities in a cylindrical stirred chamber. It was shown that by correcting for the polydispersity effect, the dependence of the wall loss rate on particle size and stirring intensity agreed with the theory of Crump and Seinfeld (1981).

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The effect of particle size on the combustion and explosion properties of grain dust is investigated by Hartmann tube, cone calorimeter (CC), and thermogravimetry (TG), it aims to provide fundamental experimental data of grain dust for an in-depth study on its potential risk. The fine-grain dust facilitates the decrease in the minimum ignition temperature (MIT) of dust layer and dust cloud, as well as the obvious increases in the maximum explosion pressure P max (climbs from 0.36 to 0.49 MPa) and pressure rising rate dP/dt (rises from 6.05 to 12.12 MPa s À1 ), leading to the increases in maximum combustion rate (dw/dτ) max and combustion characteristic index S, corresponding to the greater or severer potential risk. Because the E corresponding to combustion increases from 106.05 (sample with a particle size of 180-1250 μm) to 153.45 kJ mol À1 for the sample of 80-96 μm, the combustion process gradually transforms from diffusion-controlled into a kinetically controlled mode with the decreasing particle size of grain dust, together with the retardation of initially transient charring. It determines that the competition between the charring and combustion dominates the decomposition, and the combustion prevails for the coarse particle, while the charring controls the combustion for the fine-grain dust.

The effect of different carbon allotropes on the explosion and combustion of potato‐starch dust is preliminarily investigated by modified Hartmann tube and cone calorimeter (CC), using expandable graphite (EG), naturally flaky graphite, vermicular graphite, and carbon black as the dust suppressants, respectively. The results show that the maximum explosion pressure (Pmax) decreases from 0.66 to 0.39 MPa and the peak heat release rate reduces from 31.45 to13.64 kW·m−2 for the EG‐starch blended dust, due to the physically shielding effect of the fluffy and charring layer. It clarifies that the combustion of starch is mainly governed by Zhuralev–Lesokin–Tempelman 3D diffusion calculated by the modified Coats–Redfern integral method; the carbonaceous materials block the pyrolysis and migration of volatiles, leading to a decrease in DTGmax. It establishes a comprehensive method to evaluate the explosion and combustion of organic combustible dust, combining the CC with combustion kinetics effectively.