Lime Kiln Optimization: Managing the Inputs to Stabilize the Outcome

This technical paper discusses the requirements for optimized lime kiln control and presents an optimization control package which has been applied to a number of lime kiln processes. These high level supervisory systems oversee the coordination of the basic lime mud washing, fuel combustion, lime burning and kiln operation controls to stabilize the process and to attain the even lime quality required for a more stable causticizing process. These optimizing controls achieve a steadiness of operation that the most experienced operators would find difficult or impossible to achieve. To achieve this steadiness of operation, these optimization control systems strike a balance between input and output conditions and the internal kiln temperature profile by employing process running models, adapted from operating experiences, and fuzzy logic controls. Once stabilized, the process energy consumption can be reduced. Also, under these conditions, gaseous effluents can be minimized. Results from two European applications of lime kiln control are presented. In addition to achieving a high degree of stability in the process and in the lime quality these controls have resulted in significant energy savings and have increased the capacity of the causticizing process.