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 degrees C and lose their binding property and cause crumbling in most cases. This study aimed to develop a process to use a suitable organic binder for the development of blast furnace quality pellets using some additives which can overcome the strength loss of pellets during 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 at 300-350 degrees C, lower iron oxide (FeO and Fe3O4) containing materials viz. Linz-Donawitz (LD) sludge and mill scale have been added. FeO and Fe3O4 in these materials will be oxidized at the mild oxidizing atmosphere of the induration strand and initiate diffusion bonding at around 300 degrees C. Therefore, the strength loss due to burning will be compensated by the strength gain due to diffusion bonding. From the experimental study, it has been found that Ca-LS is a better binder than Na-LS and LD-sludge (LDS) is a better additive than mill scale. A combination of 0.4% Ca-LS with 5% LDS addition can prevent strength deterioration at 300-350 degrees C during drying and gives a good-quality pellet in terms of strength, thermal shock resistance, reducibility, reduction degradation, and swelling index, which is comparable with bentonite added pellet. Thus, 04% Ca-LS with 5% LDS shows its good application potential to replace bentonite in hematite ore pelletizing.