Improving Lime Kiln Efficiency: A Mill Study, 2014 PEERS Conference

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Optimization of the lime kiln requires an examination of the entire lime cycle. In order to increase the energy efficiency of the lime kiln, it is important for all auxiliary unit operations to function correctly. It is also imperative that the lime and liquor in the system to be of an acceptable quality. The current work details a kiln energy efficiency study performed by the Covington VA mill. From a recausticizing standpoint lime quality is much easier to control than liquor quality as liquor passes through many operations that are not under the Lime Kiln Operator’s control. As recausticizing is a fairly closed cyclical process where lime is concerned, saturation of impurities to the point of operational issues must be considered. Impurities include magnesium oxide, silicas, phosphorous and other metals. Other “impurities” left behind from ineffective unit operations may also concentrate within the lime cycle. All operations in the lime cycle can affect the amount of impurities allowed to enter the kiln. Specific cycle performance indicators such as lime mud solids entering the kiln must be viewed from a perspective that does not exclude these considerations and their potential impact. In order to get a true picture of the cost of operating the lime cycle, one must consider all of the inputs. The four main inputs in this cycle are power (electrical and fuel), fresh lime, caustic, and water.