Análise de propriedades térmicas de material refratário usado Como revestimento interno de caldeiras

Abstract

One of the major problems in furnace and boiler maintenance is the material applied to the internal thermal insulation that constitutes the combustion chamber. Routine interruptions to repairs large thermal steam installations, where the boiler is the most costly and worrisome equipment, can represent irreversible damage to the installation, with costs that can render repairs infeasible. The main reason is exactly the refractory material that protects the boiler internally, because it does not support successive processes of thermal expansion and contraction, being subject to the appearance of cracks and deterioration of the refractory material. In this context, this project has the purpose of implementing a test procedure of the refractory material to be used in the boiler, in order to allow the analysis of its most important thermal parameters, in order to select the appropriate coating. Objectively, this paper aims to attend to the fluidized bed boiler in development at the Laboratory of Combustion in Renewable Energies (LACER), through a partnership with the Water and Sewage Company of Ceará (CAGECE), with financial support from BNDES. This boiler should operate using dry sludge from periodic discharges of an anaerobic biological reactor, which degrades the biomass of wastewater. To maintain similarity to the technical characteristics of the boiler prototype in development, a test specimen was designed with dimensions close to the combustion chamber of the boiler, coating it internally with the refractory material selected for the study. The prototype was filled with ceramic alumina beads and heated with electrical resistance, in order to guarantee a temperature inside the porous medium similar to that of boiler operation. Thus, tests were carried out to characterize the thermal and mechanical properties of the material. For this, thermocouples were used to monitor the temperatures and to identify the thermal conductivity of the refractory. Through this experimental study, it was possible to observe the influence of the operation and design parameters, allowing to anticipate the perception about some operational problems of the boiler, which can minimize the risks to safety and the costs of operation and maintenance