A Canadian Perspective on the use of Biochar in Iron Ore Pelletizing


Olivier Lacroix, COREM; Mathieu Dubé, COREM

In the context of greenhouse gases emissions reduction efforts, utilization of biochar as a renewable and carbon neutral alternative energy source for the induration of iron ore could become an attractive option. In this study, biochar samples from various producers were gathered for characterization and testing. Mineral processing aspects (rheology, settling, wet grinding) were investigated at laboratory scale. Induration aspects were studied at laboratory scale through material characterization (chemical analyses, heating values, SEM, TGA) and at pilot scale through pot-grate tests. Biomass and biochar availability, costs and quality were determined and pyrolysis processes reviewed. For the tested biochar samples, the Bond work index and settling rates were twice as less than those of coke. Because of high slurry viscosity, dilution to ≤30% solids is required for wet grinding. Heating values similar to coke and lower SiO2 and Al2O3 content are typical. TGA and SEM analyses revealed that biochar has a lower ignition temperature than coke. Pot-grate tests showed that complete substitution has a slight negative impact on pellet quality but ≤50% substitution has no significant impact. In 2013, available biomass within 200 km of Sept-Îles would have allowed a slow pyrolysis plant located near Pointe-Noire to produce about 150 kt of biochar per year to replace 33% of the coke breeze then used by the three iron ore pellet producers from Québec and Labrador. Limitations such as biochar cost and the lack of demonstrated slow pyrolysis plant with sufficient capacity still remain.