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The ISO Coke Air Reactivity test has been used by the smelting industry for many years but its use as a calcined coke specification is decreasing. This paper presents a review of previous work published on this test and presents experimental data on a wide range of cokes currently being used for anode production. Coke air reactivities are strongly dependent on coke calcination levels and it is possible to drive air reactivities lower by increasing calcining temperatures. With the general increase in sulfur level of high sulfur cokes used in anode coke blends, higher calcining levels are not desirable due to their negative influence on coke porosity as a result of thermal desulfurization. Many smelters are now adopting lower real density specifications, which runs counter to achieving the low coke air reactivities required to meet coke air reactivity specifications.

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The sulfur level of high sulfur cokes used by the calcining industry for blending is increasing. During calcination, petroleum coke desulfurizes and the rate of sulfur loss is dependent on both the sulfur level and final temperature. Desulfurization negatively affects coke properties such as real density and porosity and additional desulfurization during anode baking can negatively affect anode properties. This paper is a follow-up to a 2007 TMS paper on desulfurization and presents the results of additional studies on anode and coke desulfurization versus equivalent baking level and discusses the effect of the level of calcination of high sulfur cokes on anode reactivity. The results indicate that the coke calcination levels must be set with coke sulfur levels in mind. It also shows that blending with high sulfur cokes need not be detrimental to anode properties. Symbols and Abbreviations T eqEquivalent temperature in [°E] as a measure of anode baking level according to ISO 17499 L c Average carbon crystallite height in coke in [Å] according to ISO 20203 or ASTM D5187-02 S The sulfur concentration of the cokes in [wt%] determined by XRF according to ISO 12980 -2000 HS High sulfur level petroleum coke, S > 3 wt% NS Normal sulfur level petroleum coke, 2 < S < 3 wt% LS Low sulfur level petroleum coke, S < 2 wt%

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