Use of Alabama Lignite in the Production of Lightweight Aggregate

摘要

Production of lightweight aggregate from Porter's Creek clay was chosen as a model process to be used in demonstrating the feasibility of using lignite fuel for rotary kiln mineral processing operations in or near the lignite belt. Pilot-scale rotary kiln testing and computer simulation of a commercial-scale operation using data from the pilot-scale tests demonstrated that lignite was a good fuel, requiring no auxiliary flame, for the processes provided the lignite fuel moisture content was less than about 20%. It was shown that hot kiln exhaust gases could be used to dry the raw lignite from about 50% moisture to 10% moisture, prior to lignite grinding and combustion, without the need for additional fuel for drying. Lignite could be delivered to the plant at a cost of $12.25/ton of lignite and would require an incremental investment of $128,500 in mining equipment. Equipment for drying the lignite with hot kiln exit gases prior to pulverization and burning represents the other major additional cost compared to a plant which burns bituminous coal plant. Using the heat requirement per ton of lightweight aggregate product from the computer simulations, the $38/ton delivered price of bituminous coal to a similar plant in Livingston, Alabama, and the relative heating values of the two competing fuels, an after tax savings of $0.58/ton of lightweight aggregate produced was projected, and an after tax discounted cash flow rate of return at 13.5% on additional invested capital was calculated. It may thus be concluded that lignite is a viable fuel for rotary kiln processing operations located in or near the lignite belt in Alabama. Lignite should be given serious consideration as the energy source for any new, as well as existing, energy-intensive industry located in that area of the state. (ERA citation 08:013894)