Deformation and Wear Analytics in Reheating Furnaces Using 3D Laser Measurement Technology

During a standard measurement procedure, the terrestrial laser is positioned scan-by scan around the vessel or inside the furnace or kiln, capturing both the refractory surface as well as some fixed steel structures positioned near the refractory lining. These structures are mandatory and provide essential reference points that ensure precise alignment of a newly created point cloud with previous scans of the same vessel or kiln. This solution is currently applied to electric arc furnaces (EAFs), ladles, RH degasser lower vessels, and blast furnace runners, using a web-based visualisation tool, as shown in Figure 1.

Parallel to this solution for the iron and steel industry, a similar approach has also been implemented for rotary kilns in the cement industry [3,4]. RHI Magnesita offers these kiln inspections and can identify areas and sections requiring repair within just a few hours. The results, including a report and point cloud evaluations are also available online via the web-based cloud platform, as illustrated in Figure 2. This service is accessible through the RHI Magnesita Customer Portal [5].

Generating a 3D CAD image of a refractory lining or steel shell typically involves combining RHI Magnesita’s technical lining drawings with information from the 3D scans of the outer furnace and surrounding infrastructure, acquired during the refractory lining scanning process. This combination ensures a high level of accuracy and enables identification of potential improvements in both mechanical (shell) and refractory design. Furthermore, this approach of creating theoretical references eliminates the need to scan safety linings, which is sometimes not possible due to installation of the wear and permanent lining at the same time.

Figure 3 shows various stages during a holding furnace lining inspection. In Figure 3a the measured wear lining (1), the redrawn steel shell of the kiln (2), and the redrawn safety lining (3) are shown. In particular, the measured wear lining (1) and the redrawn safety lining (3) serve as references to calculate the wear after a campaign and determine the residual brick length (RBL). The segmented colour code depicts the initial RBL after relining (Figure 3b) and makes the identification of high-wear areas over time (Figures 3c and 3d) easy for the operator.

As with the holding furnace at Kovohuty a.s., 3D scans of the anode furnace were performed under various conditions by both RHI Magnesita and customer personnel. To complete the reference model, Kovohuty a.s. also provided steel structure scans from a third party, enabling the creation of a CAD model through the combination of scan data and technical drawings.

The images in Figure 4 are similar to those presented in Figure 3, but highlight the applicability of this CAD approach to even larger kilns. Another detail worth mentioning is the importance of selecting the correct colour coding for presenting the results to the operators. The standardised one-code version of Figure 4c was considered to lack a certain level of detail for identifying critical areas requiring repair actions. However, the subsequently developed segmented colour edition (Figure 4d) supports decisionmaking more effectively and is now the default in RHI Magnesita 3D reports.

Hot scanning a complete lining on a regular basis is challenging—not only technologically and from a health and safety perspective, but also financially. In the steel industry, standard measurement procedures often require placing the laser inside the vessel to obtain a full 360° scan of the lining condition. To avoid high investment costs and provide a more flexible solution, RHI Magnesita now applies the same scanning technology used for cold conditions to perform hot scans. This streamlined approach focuses on capturing the critical areas of the kiln necessary to safely continue production.

To ensure the safety of both operators and equipment, the measurements are performed at an adequate distance in the immediate vicinity of the hot furnace. As a result, the inspection area is restricted to the field of view available through the furnace’s charging doors. Figure 5 illustrates the results from this approach, with Figure 5a showing the RBL on the back region of the furnace before operation. The RBL of the kiln roof and back before a local repair is depicted in Figure 5b, while the hot measurement, performed approximately 6 months later, is shown in Figure 5c. The grey-coloured area depicts the inspection area accessible during the hot measurements, compared to the goldcoloured unused lining, captured under cold conditions with the scanner inside the furnace.