EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Nowadays, energy efficiency represents the main challenge in iron & steel industries. The key aspect for the achievement of this crucial specification is constituted by the optimization of the involved billets reheating and rolling processes. In particular, the major difficult is the need of a concurrent and coordinated optimization of the reheating furnaces and of the rolling mill stands. For this purpose, most control systems exploit several groups of heating curves, obtained from offline modelling procedures. In these solutions, the lack of an adaptive framework is observed. i.Process/Steel-RHF represents the first Advanced Process Control (APC) system for reheating furnaces based on an adaptive Model Predictive Control (MPC) strategy: the patented adaptive constrained multivariable control algorithm exploits an optimal prediction of all the reheating furnaces variables, leading to an optimized management of all furnace conditions. Different modelling techniques have been used: black-box identification techniques have been employed for the furnace variables (i.e. furnace zones temperature, valves positions, temperature difference between adjacent furnace zones, smoke-exchanger temperature, oxygen contents), while a parameter varying first principles model has been developed for each billet that is located in the furnace. i.Process/Steel-RHF APC strategy allows an adaptive multivariable optimization of reheating furnaces, able to guarantee optimal operating points in all process conditions. It assured a specific fuel consumption decreasing in the range 3% - 7% in all the current applications, with a service factor greater than 95 %. The global reheating furnaces operating framework assures a coordination with the rolling mill phase. In October 2015 i.Process/Steel-RHF APC system has been awarded as the most innovative energy efficiency project in Italy, because it successfully addressed the problem of holistic optimization of a reheating furnace enslaved to a rolling-mill.