Adsorption of Moisture by Grain Dust and Control of Dust Hazards

摘要

Literature data on the theory of drying thin layers of grain was reviewed and mean values of the diffusion constant calculated. Kinetic data for the reverse process, the adsorption of moisture by grain, is very limited. No data were found on the adsorption or desorption of moisture by grain dust particles suspended in air. Accepting a diffusion mechanism and the diffusion constants obtained from the data on grain kernels, the time required for a small dry particle of dust, 100 to 20 mu m diameter, to reach 80% equilibrium moisture content in air at 23 exp 0 C was calculated to be in the range of 84s to less than one second. Experimental data were obtained on the adsorption of moisture from humidified air by corn dust of different size fractions ranging from 0.894 to less than 0.074 mm dia, by corn starch and by corn meal. A diffusion mechanism appears to be valid for the larger dust particles. Difficulty in obtaining a uniform dispersion of the smaller particles in air and apparatus limitations made it impossible to confirm or disprove theoretical predictions. However, the attainment of 14 to 15% moisture in initially dry dust within one minute was demonstrated. The results indicate that the introduction of humidified air in an enclosed grain conveying system may greatly reduce the dispersibility and explosibility of the grain dust. (ERA citation 05:034124)