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Modelagem, controle e otimização do processo dos fornos de reaquecimento de placas

Reheating furnaces are commonly found in the steel industry for thermal treatment of slabs from continuous casting process. These slabs are uniformly reheated, following a suitable temperature profile so as to they can be sent to the milling stage with the necessary mecanical and metallurgical properties. Besides, it is desirable to have a satisfactory dynamic control of the temperature in order to reduce the fuel consumption, since the reheating process is the most expensive part of the whole hot strip mill plant. In this paper it is presented the improvement developed in dynamic control in reheating furnace of hot strip mill plants of Usiminas. To achieve that, a methodology consisting of the application of a systematic experimental modeling, PI and PID controllers design, simulation, investigation of advanced control strategies (feedforward and switched controls and Smith predictor) and performance assessment has been used on main loops of process. Relative gain array metrics have been used to assess the input-output variable pairing and the coupling among the zones. According to several tests performed in closed-loop (in the real plant), the assessed results confirm the improvement achieved with the tuned control loops (by simulation). A reduction of 3.7% in the oil consumption has been observed, thanks to the improvement in the control loops and in the process efficiency. It means a monthly average saving of 182 thousand liters of oil.

Reheating furnace; mathematical modeling; advanced control; performance improvement


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