Aluminium extraction from a calcium aluminate slag using sodium carbonate based on the critical examination of the patented industrial Pedersen process

Abstract

The extraction of aluminium from calcium aluminate phases by leaching with Na2CO3 solutions has been researched intermittently for more than a hundred years. In the 21st century, this process has gained a renewed interest for the design of novel metallurgical methods. The Pedersen Process has been the only known successful industrial scale application of calcium aluminate leaching to date. The engineering principles that ensured plant operations remained, until recently, unknown. These principles are critically assessed for the first time, based on recently retrieved patents submitted at the time the Pedersen process was in operation. The findings of the previous analysis were used for an experimental study with the two goals: (i) to validate the principles applied in the industrial Pedersen process and (ii) to apply these principles in designing an optimized leaching process for calcium aluminate slags originating from alternative Al sources. The calcium aluminate slag used in this study is the by-product of an aluminothermic reduction process for Si production along with an 8% (w/w) Na2CO3 aqueous solution. Results confirmed the majority of the assumed principles. All the tested leaching conditions produced Al extraction in the range of 75% - 95% (w/w).