Iron Ore Pellet Dustiness Part I: Factors Affecting Dust Generation

Iron ore pellets abrade during handling and produce dust. This study was conducted to determine what factors affect pellet dustiness, and whether dustiness can be related to the abrasion index. Factors studied included bed depth within a straight grate furnace; pellet chemistry; firing temperature; coke breeze addition; and tumble index. Abrasion indices for all pellet samples ranged from 1.9-5.0% (20 samples) and from 7.1-27.5% (5 samples). Pellets were dropped in an enclosed tower, which enabled the collection of airborne particles generated during pellet breakdown. The quantity of airborne particles generated by each pellet type was 10-100mg/kg-drop, or 50-500mg/kg over five drops through the tower. Pellet dustiness was predominantly affected by pellet chemistry and by pellet firing temperature. Results showed a nearly 21% increase in dustiness for every percent decrease in firing temperature - this was based on a typical firing temperature of 1280 degrees C. Pellet dustiness was regressed to the pellet abrasion index (for AI<5%), which yielded a correlation coefficient of 0.22. These results show that, although AI is one of the best indicators of fired pellet quality and can indicate high levels of dust, it could not explain the dustiness of good quality pellets. The second paper (Iron Ore Pellet Dustiness Part II) explains the relationship between AI and dust for good-quality pellets; and compares fines generation between pellets fired in Straight-Grate (Traveling Grate) and Grate-Kiln furnaces.