Utilization of Sound Signals to Evaluate the Risk of Slopping in Oxygen Converters

摘要

The evolution of the sound signal produced during the operation of an industrial converter was investigated. Data from a large group of heats with different process parameters were compiled and analyzed. Main results of theses analyses showed that: At the beginning of the process the sound signal is high due to the fact that slag is not properly formed yet. As the blow progresses, the decarburization rate increases and the slag begins to foam. This is the part of the process where the sound signal exhibits its lower value and slopping events are more frequent. Towards the end of the blow, the decarburization rate decreases and the emulsion height is reduced, therefore the sound signal rises again. In those cases where slopping events were registered, the sound signal in the main blow period was carefully analyzed. When the slopping severity increases, the minimum of the sound signal is lower and the time it spends below a critical value is longer. Therefore, the percentage of the time that the signal is under this critical value (defined as Sound Signal Attenuation) was taken as representative of the slopping tendency of the heat. The Sound Signal Attenuation increases with the silicon content of the metallic charge. This is mainly attributed to the higher SiO_2 content of the slag at the beginning of the process, which raises its viscosity and foaming index. The proportion of solid metallic materials charged into the converter also showed a clear impact on the signal attenuation. To a lesser extent, the slag weight and the amount of solid pig iron and manganese ore added also affected the sound attenuation. On the other hand, for present conditions, the use of recycled converter slag didn't show any effect. As a result of these analyses, an application that predicts the slopping tendency of the heats was developed. Knowing in advance the amount and composition of the different materials to be charged, the system seeks in the historical database those cases with similar process conditions and evaluates the potential risk of slopping. This is a useful tool to select process parameters for specific charging conditions and to compare different scenarios.