Modelagem e controle de um processo de dosagem de carvão mineral e de um processo de endurecimento de pelotas de minério de ferro

Abstract

This work describes the steps of a classical control system design applied to an industrial iron ore pelletizing plant facility. The study includes the following segments:description of the process, mathematical modeling, assessment of the level of interaction among variables, definition of the control strategies, design of PID controllers and decouplers, practical implementation of the control system, and, finally, analysis of final results. The dosing system for coal and iron ore and the pellet indurating machine, where the system is applied, is described in detail. The variables to be controlled and manipulated in the furnace are investigated and determined. The method of identification through step response is utilized in the mathematical modeling of the pellet induration process. The estimate of parameters of the second order models is carried out with the use of classical graphic methods. The Transfer Function Array (TFA) standard technique is employed in the assessment of the level of interaction among variables and in the selection of the most appropriate pairing of controlled and manipulated variables. The process control strategy is defined based on the TFA recommendations and previous knowledge of the process behavior. The direct synthesis method is used to design the controllers based on the process models and the desired close-loop responses. Control loop interactions are reduced by adding decouplers to the conventional PID configuration. The design method is algebraic and based on mathematical models that describe the interactions. Aspects of the practical implementation of the control system are also described.