10 - Rotary Kiln Minerals Process Applications

Abstract

From the fuel requirement point of view, rotary kilns are the most flexible of all lime kilns. They are successfully fired with natural gas, fuel oil, and pulverized fuels of all types including coal, coke, and sawdust. There are many processes that employ the rotary kiln as the primary reactor, encompassing all industries including food, dedicated dryers, minerals processing, etc. This chapter focuses on minerals and materials processing and provides some of the key industrial processes that use a rotary kiln as the primary workhorse. Rotary kiln technology evolved from the struggles of early engineers and inventors to produce cement and lime in an efficient, safe, and economic way. The cement and lime processes and some of the carbothermic reduction processes that employ the rotary kiln as the primary device are described. The processes of iron ore reduction (the SLRN process) and illmenite ore reduction (the Becher process) and the lightweight aggregate process are examined. Rotary cement kilns can be classified into wet-process kilns, semi-dry kilns, dry kilns, preheater kilns, and precalciner kilns. The pertinent process chemistry and the heat requirements that drive them so as to be consistent with the transport phenomena theme are shown.