Effect of heat treatment on desulphurization of petroleum coke

Abstract

Calcined petroleum coke (CPC) is one of major constituent used for making graphite electrodes. Increasing demand of graphite electrodes requires more and more quantity of high quality-low sulphur calcined petroleum coke. The sulphur content of the petroleum coke strongly depends on the nature of the coking feed stock (crude oil) and its sulphur content. High sulphur coke (>1%) is not desirable for making graphite electrodes because evolution of sulphur causes puffing in the temperature range of 1,400-2,200 °C during graphitization. In this study, attempt has been made to reduce the sulphur of calcined petroleum coke by heat treatment to the acceptable level for making graphite electrodes. A high sulphur coke (approx. 2%) was heat treated up to 1,800 °C in inert atmosphere in order to reduce the sulphur content. It was observed that most of the sulphur goes off up to 1,800 °C. A sample of size 12x80 mm was prepared (by extrusion method) from desulphurized petroleum coke using coal tar binder pitch as binder at 125 °C. The extruded samples were carbonized at 900 °C, followed by graphitization at 2,900 °C. The graphitized rods were characterized for various properties such as apparent density (AD), electrical resistivity (ER), flexural strength (FS) and compared with the properties of samples made from electrode grade CPC.