Second law analysis of a furnace for metal heating

Abstract

The industry represents an important sector of the final energy consumption and despite the effort made so far, energy saving potential still remains in this sector. This paper presents an example of energy efficiency improvement in a furnace for metal heating by adjustment of burners and recovery of heat. The useful concept of exergy is used to investigate the exergy efficiencies of the furnace operating in different situations: with air preheating using the waste heat contained in exhaust gases and with different air excess. The overall exergy efficiency of the furnace decreases with the increase of air excess and increases from 29.65% to 52% by using air preheating. The exergy efficiency of combustion is higher (70%) than the exergy efficiency of heat transfer from flue gas to metal (36.4%).