Análisis del impacto de los procesos de fabricación del cok en la vida útil del refractario silíceo de los hornos y evaluación de las técnicas de reparación

Abstract

In the manufacture of steel coke, there are a series of circumstances inherent to the process which can affect the life of the refractory material with which the ovens of the batteries are built. On one hand this research will deal with the impact of aspects such as sticky ovens and hard pushes on the refractory. On the other hand, the next step will be to analyze the different oven repair techniques, defining the most appropriate ones depending on the area of the oven to be repaired and type of damage to the refractory. For this purpose, data will be obtained from a Didier design coke plant built in the 1970s. Coke batteries are a series of ovens placed one after the other, hence the name. The ovens are made entirely of refractory material. The only metallic parts found in the coke ovens are armatures and fasteners. That is why it is essential to prevent the refractory from deteriorating, shortening the useful life of the coke ovens as a consequence. Research appearing in the technical and scientific literature provide instructions and good practice advice to extend the life of coke oven refractory, but without considering the impact that hard pushes and sticky ovens can have. Of the types of refractories of which coke batteries are composed, we will only deal with silica material. This is the type of refractory with which the combustion and coking chambers of the ovens are almost exclusively built. Its characteristics and behavior make silica a major player in the service life of a coke battery. Therefore, any aspect of the process that is susceptible to damage this refractory will have a great impact on the life of the coke manufacturing equipment. Traditionally sticky ovens have been treated simply as a problem which moderately slow down operations, affecting cok production performance, whereas hard pushes have been considered as a potential source of damage with immediate effect. The relevance of this study lies in the evaluation of the damage that both sticky ovens and hard pushes are likely to cause on the refractory of the ovens. This damage may require major repairs, with the result that the oven would be out of service while repairing, having a clear impact on productivity and in some way on the useful life of the coke batteries. The initial hypothesis is that sticky ovens and hard pushes cause refractory damage; by analysing the data, conclusions will be drawn which, in a novel way, will help coke plant technicians to manage their operations, while minimizing the impact on the refractory of the equipment. For the development of the study, data will be collected on sticky ovens, hard pushes and the scope of refractory repairs. A transversal and a longitudinal study will be carried out. In the transversal, data will be collected from eight batteries, with thirty ovens each, that is, over a period of two years. Each oven is operated five hundred eleven times per year. In the longitudinal study, data from two ovens will be analyzed over a period of ten years of operation. In both studies it will be concluded that hard pushes and especially sticky ovens cause damage to the refractory. To carry out the analysis, we collected data on the number of hard pushes that each oven experienced in the study period, either transversally or longitudinally. On the other hand, the number of sticky ovens in the aforementioned period. At the same time, information is collected on the scope of the repair that each oven had, both in the application of ceramic welding and the number of pieces of fused silica placed. To choose the type of refractory repair, a description will be made of the different techniques available on the market and the characteristics of the products used. The refractories installed in the design phase and the operating conditions of the ovens will be chosen as a reference standard. The conclusions of the work tell us that hard pushes causes damage to the refractory due to mechanical stress and sticky ovens also due to thermal shock. In the case of hard pushes, the negative effect is not always immediate and is influenced by the magnitude of the oven removal resistance. Among the different repair techniques, ceramic welding is the one that provides a better relationship between execution time and lining duration. Replacement with crystalline or fused silica bricks offers longer useful life but its execution time is long and expensive. Keywords- Cok ovens, silica refractory, ceramic welding, sticky ovens, hard pushes.