Refinery Feedstocks, Coke Structures and Aluminum Cell Anodes

Abstract

Selected commercial and experimental petroleum cokes derived from a variety of refinery feedstocks ranging from aromatic to asphaltic materials have been examined in the laboratory. A wide spectrum of coke structures has been observed resulting from the different types of feedstock and coking conditions used. In laboratory-scale anodes prepared by using conventional procedures sponge cokes derived from the residuals of paraffinic and several mixed crudes gave good results. When, however, the bulk density of these cokes was low, modification of the aggregate size distribution and adjustment in the binder content were necessary to obtain acceptable results. The use of anisotropic, needle-type, cokes from aromatic residuals did not result in a significant improvement of test electrode properties. Isotropic cokes including those derived from asphaltic feedstocks gave acceptable results in the laboratory when used alone or in a blend with anisotropic cokes. With this type of coke, however, the selection of the degree of grinding, the aggregate size distribution, and the binder content was more critical than with regular sponge cokes. Changes in coke structure have also been followed in production cell anodes. Observations in the laboratory and in the plants have been in general agreement.