Exergy and its efficiency calculations of shaft furnace for sinter pellet production

In ferrochrome production, chromite ore fines are first agglomerated as green pellets and then fired in a shaft furnace (SF) to produce sintered pellets. These sintered pellets are then charged to a submerged electric arc furnace (SAF) for the production of ferrochrome alloy. The SAF off gases are utilised in the SF to heat green pellets resulting in sintered pellets. The specific energy consumption of sinter pellet production was observed to be 1.9–2 GJ per tonne of pellet. The exergy efficiency of the existing process and a variation of it was evaluated in this work. Presently, 47% excess air is used for the combustion of SAF off gases and carbon present in green pellets and the only valuable product in the existing process is the sinter pellets. We have considered the case with only 20% excess air and the valuable products are sinter pellets and power generation.