• Dust Management Technologies

Understanding and modelling dust generation mechanisms will assist greatly in tackling the root cause/s of fugitive dust emission problems. This also will help to optimize and minimize the size and cost of the “final” dust control system needed for a given product and application.  The total amount of air “generated” inside the container consists of: interstitial air entering the product discharging from the hopper outlet (due to expanding voidage inside the hopper); air being dragged by the material stream (referred to as induced air); entrained air (due to the expanding voidage of the free-falling stream of bulk material); displaced air (due to particles entering the container). Based on experience and research, entrained air has been found to be most dominant, even for relatively small drop heights. For example, Cooper and Wypych (2001) found that entrained air is proportional to drop height raised to a power of n = 5/3.It is interesting to note CEMA (2007) presents an equation for entrained (induced) air to assist in the design of dust control systems for conveyor transfers. This equation can be simplified to show that the drop height exponent, n = 2/3. This means that doubling drop height will result in a 60% increase in air entrainment (and corresponding control volume). However, based on the experimentally verified value of n = 5/3, a doubling of drop height will actually result in a 220% increase in air entrainment (not 60%). Hence, it appears that CEMA (2007) will significantly underestimate the effect of drop height on entrained air (and required control volume for effective dust control).