Improving energy efficiency of an austenitization furnace by heat integration and real-time optimization

We study the effect of heat integration on fuel savings for a currently operating industrial austenitization furnace. More than 40% of the heat input to the system (heated indirectly by radiant-tube burners) is discharged in the burner exhaust. We report on the potential energy savings resulting from capturing some of the exhaust heat to preheat the inlet air to the burner using a recuperator - a specialized gas-to-gas heat exchanger. The novelty of this work is the development of a detailed model of the recuperator, capturing essential physics such as local convection and long-range surface-to-surface radiation heat transfer, and using the model for simulation and operational optimization of the furnace. The operation of the furnace with a recuperator installed at every burner requires 15.93% less fuel input to the system compared to the base case without recuperators, with negligible changes in the part exit conditions. Optimization of the furnace using a response-surface methodology further reduces the fuel consumption by 5.87%.