Original Article

Effect of CaO based dual flux addition on iron ore pellet properties

JSW Steel Limited, Bellary (dt), India

^* e-mail: uma.devi@jsw.in

Received: 2 September 2024
Accepted: 4 December 2024

Abstract

Limestone and wollastonite are the main CaO bearing fluxes. Wollastonite is a calcium silicate (CaSiO₃) and limestone is a calcium carbonate (CaCO₃). Wollastonite has an LOI of 6–8%, whereas limestone has 42–44%. The CaO content in limestone and wollastonite is 50.51% and 45.30% respectively. To study the effect of wollastonite as a lime-bearing flux on iron ore pellet properties, detailed laboratory studies have been carried out by replacing the limestone with wollastonite. The Cold crushing strength (CCS) of the pellet increased from 282 to 295 kg/t, the reduction degradation index (RDI (–6.3 mm)) was reduced from 10.5% to 9.2%, and the reducibility index (RI) was reduced from 72% to 71.4% at pellet basicity (CaO/SiO₂) of 0.30. The improvement in the physical and metallurgical properties of the pellets with 40% wollastonite was due to the presence of small pores with a higher pore density. The distribution of slag phase around the hematite particles is uniform throughout the pellet, and there are more recrystallized hematite particles with better slag bonding. The addition of CaO and SiO₂ in the form of wollastonite improves the pellet properties in the form of slag phase. Pellet with lime-based dual flux with 40% wollastonite specific consumption of raw material was reduced by 2kg/ton of pellets due to the presence of negligible amount of loss of ignition (LOI) in wollastonite; and 7% of CO₂ emissions was reduced due to the absence of carbonate.