Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2004
Publication Date: 1/1/2005
Citation: Brabec, D.L., Maghirang, R.G., Casada, M., Haque, E. 2005. Characterization and modeling of a high-pressure water-fogging system for grain dust control. Transactions of the ASAE. 48 (1):331-339. Interpretive Summary: Grain dust is a health risk to workers and a fire risk for facilities. Several dust control methods are available such a pneumatic system and suppression with edible oils. A high-pressure fogging system was tested for potential as a dust control method. The drop size and induced airflow characteristic of the high-pressure fog were identified. Airflow and particle trajectory mathematical models were calculated for typical grain receiving and for fog treatment at grain receiving. The mathematical models predicted air recirculation into the receiving hopper when the spray system was operated. Smoke test were used to validate the air flow models. The fogging system improved dust containment as demonstrated by the air and particle trajectory models. Fog emissions and deposits were generated and were small and manageable, but they could become a problem if mis-managed. The use of a spray-fog system for grain dust control would need approval from regulatory agencies and is currently restricted by U.S. laws protecting the quality of grain shipments
Technical Abstract: Grain dust, a health and safety risk, is generated whenever grain is loaded into or unloaded from hoppers and equipment. This research investigated airflow models and evaluated the particle dynamics from a high-pressure water-fog system for potential dust control at a grain-receiving hopper. A 0.2-mm (0.008-in.) spray nozzle was used to produce a plume of fog directed across a free-falling grain column. Ninety percent of the fog drops ranged from 10 to 40 µm in diameter. Average drop velocities in the plume cross section were over 10 m/s at 7.6 cm from the nozzle. The air-velocity pressures at 7.6 cm were parabolic in the radial direction, with maximum pressures over 275 Pa (1.1 in. H2O). Airflow distributions, grain-dust transport, and spray-droplet trajectories within the test chamber were modeled in three dimensions using FLUENT, which is a computational fluid dynamics (CFD) software program. Induced airflow from the spray fog caused recirculation of the air and dust particles in the lower part of the chamber. This recirculation pattern transported the dust from the grain pile back into the spray plume, where it mixed with the spray fog. Experiments in a test chamber, representing a section of a grain-receiving hopper, produced side-wall fog deposits of 11 mg/cm2/min in the middle where plume and airflow was restricted by the incoming grain. The side-wall fog deposits decreased to 1.5 mg/cm2/min near the outlet. Most grain-surface fog deposits ranged from 0.1 to 0.4 mg/cm2/sec.