Studying the efficiency of lime-soda sinter process to extract alumina from colored kaolinite ores using factorial technique of design of experiments

Abstract EN

As the increasing demand for alumina in recent years with the result diminishing reserve of bauxite, the need to secure a domestic raw material base is driving research in new technologies to process low grade ores into alumina, with the intention that these technologies will lead to a significant reduction of bauxite and alumina transportation costs, allow the extraction of more valuable components from the ore and reduce environmental impact.

Clays are types of the low-grade aluminum ores, they're also well abundant which make them a potential substitutes for Bauxite.

In this work, lime soda sinter process was adopted for extracting alumina from kaolinitic claystone from Al-Ga'ara formation (Duekhla) quarry in western Iraq.

The operation efficiency of sintering was studied in which the whole process has been done with three stages: the sintering process for the raw materials, leaching and carbonizing processes to precipitate and separate the alumina from the leach pregnant solution .

Factorial technique of Design of Experiments (DOE) module in Minitab was used as a principal methodology to examine the sintering efficiency over alumina extraction.

The results obtained showed that the optimum parameters for the sintering operation were CaO/SiO2 molar ratio of 2.2, Na2O/Al2O3 molar ratio of 1.2, sintering temperature at 1213 °C for 90 min.

The sintered materials were leached with sodium carbonate solution, and sodium aluminate solution was obtained.

By bubbling carbon dioxide gas into this extract solution aluminum hydroxide [Al(OH)3] has been precipitated and on calcination at 1200 °C for 2 hrs, alpha alumina (α-Al2O3) was obtained with purity of 98.5 %.