The Influence of Moisture content in Thermal Insulating Material on the Thermal State of Castner Furnace

Abstract

Constant world growth of electric steel production volumes leads to increase of capacities of arc furnaces, which require the usage of high quality graphite electrodes of large sizes. The production and usage of large-scale graphite products is explained by the fact that a diameter increase of the melting electrodes allows to reduce the specific costs of both electricity and electrodes number during the manufactured electrostatic furnace. For graphitization of electrodes of large diameters (600 mm and more), according to the basic technical and economic indicators, it is the most efficient and appropriate to use direct-heating furnaces, which operate using Castner method. The most important factors that mainly affect the quality of finished electrode products are the level of achieved temperatures in carbon blanks and speed of their heating during the graphitization process. What is important, these factors depend on the properties of the selected heat-insulating materials and mainly on its moisture content. In order to study the effect of moisture content in the heat-insulating material on the thermal state of the Castner furnace, a numerical model of the heat-electric state of the graphite furnace was used, which takes into account the thermal effects of the chemical reactions of carbonation gasification, the mechanism of transfer of moisture and water vapor, the conversion of hydrogen and carbon monoxide into a heat-insulating material. On the basis of numerical analysis, the influence of the moisture content of the heat-insulating material on the thermal state of the Castner furnace in the process of graphitization of large-scale electrode billets was investigated. As a result of the analysis of the results of numerical experiments, it has been established that instability of the moisture content of the heat-insulating materials in the furnace requires adjustment the schedule for electric energy introduction into the furnace in order to prevent the mechanical destruction of the blanks due to high speed of their heating in a dangerous temperature range characterized by intense sulfur oxide separation or electricity overrun.