Impurity level distribution in GPC and CPC and impact on anode properties

Abstract

Aluminum smelter specifications for trace metal impurities in calcined petroleum coke (CPC) are based on a bulk analysis of the coke. Recent experience shows that it is important to understand the distribution of impurities when considering new sources of green petroleum coke (GPC). Most GPC sources have a uniform distribution of impurities like vanadium, iron, silicon and calcium throughout the particle size range but some sources show a concentration of iron, silicon and calcium in the fines fraction. The paper presents a review of the origin and distribution of impurities in GPC and the results of an investigation into the root cause of elevated calcium levels in a GPC source used in an anode-grade CPC blend. High levels of calcium in the fines fraction of the CPC had a significant negative effect on anode CO2 reactivities. The paper highlights the need to be cautious when using new GPC sources. Copyright © 2014 by The Minerals, Metals & Materials Society.