Research On Composite Binder Of Iron Ore Pelletization

Iron ore pellet has many advantages as a kind of burden for iron making, such as better metallurgical properties and obviously improving the permeability of the burden bed in the blast furnace. It is regarded as an essential and excellent charge for optimizing the furnace structure, and widely used in iron and steel industry. In recent years, most of steel companies in China are developing pellet production at a higher rate, specially grate—kiln pellet production technology. At present, bentonite as one kind of binder is used in many pellet plants. However, many residues are obviously left in the pellets after they are fired, which decreased TFe of the roasted pellet decreased. Therefore, developing new binders to substitute bentonite or decrease the benionite dosage is an effective way to improve TFe of the roasted pellets.The experiments result of making pellets by adding single binder showed that when 3% bentonite,drop strength was 5.5 per 0.5m; when the binder with 0.4% A, the drop strength was 3.2 per 0.5m and the dosage of A is between 0.2% to 0.4%,the strength of roasted pellet was more than 10N/p,the single binder of bentonite not only increase the dosage but also decrease TFe of roasted pellets and was difficult to achieve requested technical indicators of pellets. But the burst temperature was high. High speed mechanical mixture can effectively improve the quality of pellets. The green ball was improved with the increase dosage of organic A. The burst temperature first increased then decreased slightly.The experiment results of the pellets added composite binders,2% bentonite and 0.2% A showed that the fall strength was almost 7.8per 0.5 m, compression strength can be 14.69N/p,burst temperature was 720℃. With the addition of inorganic binder B, composite binder effect markedly improved. Adjust their proportion by experiments, when the binders was added 1% bentonite,0.15%A and B, the green fall strength was 7.5 per 0.5m. Replaced Ca-bentonite with Na—bentonite, the dosage of binders was still unchanged, the green ball fall strength was markedly improved, from 7.5 to 10.3 per 0.5m, the compression strength 15.63N/p, much higher than production requirements.The pellets using the sodium of bentonite as binder the strength and burst temperature were increased with increased the swelling degree. When swelling degree was 39 ml/g, the fall strength was 10.4 per 0.5m, while the selling degree was 57 ml/g, the fall strength was 12.7 per 0.5m. When swelling degree was 40 ml/g, the burst temperature was higher than 720℃.From the mechanism analysis of composite binders, we knew that binders play different roles, and at different time work than simple increase dosage. The 3 binders were highly hydrophilic,organic A and inorganic B have highly cohesive, which can improve the green ball strength; because of the structure of bentonite, while was in the drying process, will not cause the green ball burst that rapid dehydration caused too much vapor pressure Inorganic binder B has structure of [SiO4] enhanced the strength of dry ball.