Compaction properties of carbon materials used for prebaked anodes in aluminum production plants

The anodes used in aluminum production are formed by compaction of a paste composed of binder matrix and coarse particles of petroleum coke (aggregates). Binder matrix composed of a coal tar pitch and fine calcined petroleum coke is usually characterized by coke and/or pitch content and also by the fineness of the coke particles. Since the coke particles are rigid and assumed to be non-deformable during compaction, the deformation behavior of the binder matrix plays a crucial role in the anode paste compaction process. Compaction of binder matrix with different compositions in a rigid closed die was studied in this work. Binder matrix compositions were compacted to a maximum uniaxial pressure of 70 MPa at 150°C. Different strain rates of 2.9 × 10− 4 s− 1 and 2.9 × 10− 3 s− 1 enabled us to evaluate the contribution of viscous behavior of the material to the compaction of binder matrix as a function of its composition and deformation rate. A similar experimental compaction procedure with strain rates of 1.8 × 10− 4 s− 1 and 1.8 × 10− 3 s− 1 was applied on paste samples with different pitch contents. This study revealed that the compaction of binder matrix and anode paste with conventional compositions is not significantly a time dependent process. Viscous behavior may therefore not have a significant contribution to the compaction of the material.