Influence of Coke Calcining Level on Anode Real Density, L_C and Other Properties Using a Constant Baking Cycle

Abstract

Real density (RD) and crystallite size (L_C) are common measures to control coke calcination levels. They are also measured routinely on anode core samples as a means of tracking anode baking levels. Many anode producers target anode RD levels which are at least 0.02 g/cm³ higher than the calcined petroleum coke (CPC) RD to minimize differential reactivity between the CPC and binder derived carbon. Depending on the calcining process parameters and technology, coke RD and L_C can vary significantly. Shaft CPC often shows a higher RD and L_C than rotary kiln CPC due to the longer residence times. Coke blends with CPC having different RD and L_C values are now regularly used by aluminum smelters. This paper reports on the results of pilot anode studies to evaluate the impact of the starting CPC RD and L_C on final anode RD, L_C and other properties such as specific electrical resistivity and carboxy reactivity.