# Investigation of Inner Lining Loss and Correlation with Steel Structure Quality in Rotary Kilns
## 1 Introduction
The quality of the product in the rotary kilns is highly dependent on the thermal profile. Thermal imaging can be used to ensure that the product is heated to the correct temperature and for the appropriate duration, resulting in a consistent and high quality product [34]. During a rotary kiln shutdown, point clouds were collected. Ladle refractory linings used in the steel industry can be checked for gaps and cracks with a special laser scanner [35]. We use the laser scanning method to determine how much of the inner layer has been lost. Every year, the internal lining of the rotary kiln is inspected and repaired as necessary. The inspection is performed by piercing the inner lining with a drill and then measuring the depth of the remaining brick. Unfortunately, since drilling is only performed in a single line along the entire length of the rotary kiln, measurements cannot be taken over the entire surface area of the rotary kiln. The laser scanner is used to measure the entire interior area and determine how much loss there is. There are different ways to determine the cost. The first option is based on the difference between the point cloud of the inner lining and the point cloud of the outer steel structure. To do this, the plans must show the thickness of the outer steel structure. The second choice is to make a perfect model of the inner lining and determine how different it is from the actual point cloud. The previous work closest to this paper is Refractory Brick Lining Measurement and Monitoring in a Rotary Kiln with Terrestrial Laser Scanning [32]. Laser scanning with a Zoller + Frohlich Imager(r) 5010c scanner of the interior of a rotary kiln was used to determine the loss of the interior lining. A cylinder was fit to the point cloud of the inner lining using the RANSAC [36] method and the CloudCompare software [37]. The cylinder axis was used to determine the rotation axis of the rotary kiln. In this paper, a similar method was chosen with the difference of determining the cylinder on the outer shell of the rotary kiln. On the steel outer shell, the deformations are not similar on the inner lining. The axis is determined on a better quality substrate without loading a large number of outliers. The determination of the ovality of the rotary kiln by laser scanning has already been dealt with by [23; 38; 39]; this article does not deal with innovative solutions to improve the ovality results. The contribution of this article lies in finding the relationship between the loss of the inner lining and the ovality. At the same time, it lists the possible point cloud analysis if the rotary kiln is scanned inside and outside. The correlation between lining loss and ovality in rotary kilns is a novel finding that has important implications for the maintenance and operation of these industrial vessels. Previous research has shown that lining loss is a major problem in rotary kilns, but the underlying causes of lining loss have not been fully understood. The new finding that ovality is a significant factor in lining loss provides a new avenue for research into the prevention and mitigation of lining loss. This paper introduces a laser scanning method that enables the simultaneous estimation of lining loss and ovality using a single measurement system. This innovative approach facilitates the examination and modelling of the correlation between lining loss and ovality. The laser scan data presented in this paper are applicable for additional analyses outlined in the study. In the Material and Methods section, we elucidate the employed rotary kiln and its associated parameters. In addition, we detail the methods utilised for measurement and the procedural intricacies of the entire process. The Results section encompasses potential analyses derived from laser scan measurements, encompassing aspects such as the loss of inner lining, ovality, radius disparities, and the correlation between inner lining loss and ovality, along with the material loss in the riding ring.