Online Image Analysis of Nodule Particle-size Distribution for the Control of Lime Kiln Operation, 2023 PEERS Conference

To maximize efficiency of the recausticizing process in a pulp mill, it is of great importance to produce a reburned lime with high and consistent reactivity. The reactivity of the produced lime has in prior investigations shown to be connected to the nodule size of the lime and, as well as the dusting behavior of the kiln. Therefore, keeping track of the size of the nodules produced in the lime kiln could be a promising indirect method to measure the performance of the lime kiln. The aim of this study was therefore to evaluate an image analysis camera, 3DPM, for the online monitoring of nodule size distribution of the lime kiln. A series of full-scale trials were performed in a lime kiln of a kraft pulp mill, in which a camera was mounted to the exit conveyor of the lime from the kiln. The nodule size distribution was analyzed for correlation with the lime temperature, flue gas temperature and rotational speed of the kiln. The 3D camera monitoring was stable over time and the results show that the lime temperature had the most significant effect on the nodule size. The rotational speed of the lime kiln and the flue gas temperature showed limited effect on nodule size but had significant impact on the specific energy demand. The overall conclusion of the study was that the 3D camera methodology can be used to correlate the effect of lime temperature with the nodule size distribution and is suggested to be implemented to automatically control the lime temperature, to produce lime of high and consistent reactivity at decreased specific energy use.

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