Fluidized bed furnace for roasting zinc concentrates as a control object

Abstract

The relevance of the research is caused by continuous increase in using zinc in the world. Obtaining of zinc is an expensive process, one of the stages of which is roasting of sulfide zinc concentrates (charge) in a fluidized bed furnace using air blast enriched with oxygen. Since the granulometric composition of the charge, its moisture content and composition are variable, the temperature of the fluidized bed can vary and requires continuous monitoring by the operator. A huge mass of material determines the large bed inertia, therefore, it is necessary to use an automatic control system. The main aim of the research is to optimize the operation of the fluidized bed furnace for roasting sulphide zinc concentrates, in par ticular, to introduce automatic control of the fluidized bed temperature in order to avoid temperature fluctuations over a wide range. A significant decrease of the bed temperature leads to degradation of the concentrate roasting, as a consequence, the yield of the final product (zinc) decreases. As the temperature rises, the danger of bed slagging increases substantially due to the possible local overhea ting. To do this, it is necessary to obtain the dependence of the bed temperature on the charge rate, both by calculation and experimen tally, on the basis of the studied kinetics of zinc concentrate oxidation in the fluidized bed furnace. Object of research is the fluidized bed furnace of the Chelyabinsk Zinc Plant for roasting sulphide zinc concentrate. Methods: obtaining the calculated dependence of the fluidized bed temperature on the charge rate based on the studied kinetics of zinc concentrate oxidation; an experimental study of the dynamics of the change in the bed temperature with a change in the charge rate. Results. The authors have developed the mathematical model of the transient processes in the fluidized bed furnace for calcining zinc concentrates, which makes it possible to calculate the change in the bed temperature and the combustible substances concentration in it with a change in the charge rate. Comparison of the calculations with the experimental data showed good convergence of the results. On the basis of the obtained data, an approximate model of the fluidized bed furnace in the Ovatsiya PTA and an algorithm of the flui dized bed temperature regulator were developed. The introduction of a temperature regulator at the Chelyabinsk Zinc Plant will enable automatically maintain the specified fluidized bed temperature, the constancy of the combustible in the bed, eliminate undesirable char ges, and reduce the danger of slagging the layer. © 2018 Tomsk Polytechnic University, Publishing House. All right reserved.