Modeling and control of submerged-arc ferrosilicon furnaces.

摘要

The occurrence of electric arcs plays an important role in a ferrosilicon furnace. As the arcs are the main source of electric power generation in the furnace, changes in the arcing conditions will affect the total process conditions significantly. In addition, using electric measurements the effects of electric arcing may indirectly give important information about inner process variables. Based on these facts, the thesis gives a comprehensive review of arcing theory related to the arcs present in submerged-arc furnaces. Focus is placed on the properties of such arcs and their influence on the conditions in the cavities in a ferrosilicon furnace. Attention is also given the modeling aspects of electric arcs. Different model descriptions of direct current (DC) arcs are reviewed, and three-dimensional analytic models and channel models are discussed. A further subject is dynamic models of alternating current (AC) arcs. Empirical dynamic models of AC arcs are briefly described, while dynamic AC arc models based on arc channel modeling, are considered in more detail. This part of the thesis concludes with the recommendation to use dynamic AC arc channel models to describe the arcing in submerged-arc ferrosilicon furnaces. The study of the electrical conditions in a ferrosilicon furnace has verified the importance of a satisfactory electrical control system. It can be further concluded that significant information about inner process variables is accessible by the use of a model-based estimator operating on electrical measurements. The chemical reactions in the ferrosilicon process are treated and a stoichiometric model is described. Important terms related to the process are defined, and models of possible reaction patterns are discussed. This discussion concludes with a recommendation about how the process variables should be used in the metallurgical control of the furnace. 141 refs., 123 figs., 12 tabs.