An innovative approach to replace bentonite in hematite ore pelletizing with organic binder

Abstract

There is a continuous endeavor to replace bentonite with any other suitable inorganic or organic binders.Organic binders generally burn at around 300–350°C and lose their binding property and cause crumblingin most cases. This study aimed to develop a process to use a suitable organic binder for the developmentof blast furnace quality pellets using some additives which can overcome the strength loss pelletsduring induration. The wastes generated from pulp industries viz. Ca-lignosulphonate (Ca-LS) and Na-lignosulphonate (Na-LS) have been used as binders in hematite ore pellets. To alleviate the strength loss at300–350°C, lower iron oxide (FeO and Fe3O4) containing materials viz. Linz-Donawitz (LD) sludge and millscale have been added. FeO and Fe3O4 in these materials will be oxidized at the mild oxidizing atmo-sphere of the induration strand and initiate diffusion bonding at around 300°C. Therefore, the strengthloss due to burning will be compensated by the strength gain due to diffusion bonding. From theexperimental study, it has been found that Ca-LS is a better binder than Na-LS and LD-sludge (LDS) isa better additive than mill scale. A combination of 0.4% Ca-LS with 5% LDS addition can prevent strengthdeterioration at 300–350°C during drying and gives a good-quality pellet in terms of strength, thermalshock resistance, reducibility, reduction degradation, and swelling index, which is comparable withbentonite added pellet. Thus, 04% Ca-LS with 5% LDS shows its good application potential to replacebentonite in hematite ore pelletizing.