Armin Abazarpoor ¹, Mohammad Halali ¹

Affiliations
1 Materials Science and Engineering Department, Sharif University of Technology, Azadi Street, PO box 11365-11155, Tehran, IR

Abstract

Objective: The dimensional properties of iron ore pellet feed including specific surface area and particle size distribution in the ball mill was studied using response surface area method. Methods/Statistical analysis: The effect of the operational parameters of dry ball mill including ball charge (20-40%), grinding time (30-50 min) and balling distribution (Small, Mixed and Large) on dimensional properties of pellet feed was meticulously examined and optimized using response surface methodology based on Central Composite Design (CCD). Responses were 80% passing size (D80) and Blaine (BL). A total of 30 grinding experiments were designed and carried out in the CCD method. Regression models and response surfaces were obtained for each response. Findings: The results predicted by these models showed good agreement with experimental values. In the studied range it was deduced that D80 is decreased and BL increased when grinding time and ball charge increased. Also, the production of fine particles improved using balling distribution of level B (mix balls), instead of one ball size distribution. 3D graphs were applied to visually evaluate each parameter effect on responses. The optimum conditions of ball mill operational parameters to reach the best pellet feed for each blast furnace burden and direct reduction iron (DRI) pellet feed were revealed using CCD optimization. The predicted values BL and D80 were found to be in a reasonable agreement with the experimental values, with R2 as correlation factor being 0.91 and 0.92 for BL and D80, respectively. Improvements: The optimum condition for having a suitable blast furnace burden was: Ball distribution level B, Ball charge= 21.8-22.4 %, Grinding time= 40.1-42.9 min. Also, the optimal condition for DRI pellet feed preparation was: Ball distribution level B, Ball charge= 21.8-22.1 %, Grinding time= 42.1-44.6 min.

Keywords

Ball Mill, Central Composite Design, Particle Size, Pelletizing, Specific Surface Area.

Full Text

   

Armin Abazarpoor ¹, Mohammad Halali ², Hediyeh Khatibnezhad ²

Affiliations
1 Young Researchers and Elite Club, Anar Branch, Islamic Azad University, Anar, IR
2 Department of Materials Science and Engineering, Sharif University of Technology, Tehran, 11365–11155, IR

Abstract

In this study the leaching of a high rutile containing slag in sulphuric acid has been investigated to find optimum leaching conditions. Using "Fractional Factorial" technique it was deduced that leaching temperature and duration, acid concentration and particle size are the most prominent parameters in the leaching process. The optimization of the leaching process was investigated using the "Rotatable Central Composite Design" technique. The four prominent parameters were studied at 5 different test values each. 3D response surface was employed to illustrate interaction of the parameters. The optimum leaching conditions for the ilmenite concentrate are thus recognized as: T = 123.9˚C, time = 323 min, acid conc. = 8.73 mol/ltr, particle size = 33-60 μm. Under these conditions the theoretical and experimental recovery of titanium for the concentrate are found to be 58.2% and 56.1% respectively. Using the same technique the optimum conditions for the slag are found as: T = 122.2˚C, time = 255 min, acid conc. = 11.84 mol/ltr, particle size = 54-95 μm. Under these conditions the theoretical and experimental recovery of titanium for the slag are found to be 67.4% and 66.2% respectively.

Keywords

Factorial–Based Methods, Ilmenite, Leaching Optimization, Slag, Sulphuric Leaching

Full Text