Observations on the Coke Air Reactivity Test

Abstract

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.

Aluminium Primary Production Off-Gas Composition and Emissions: An Overview

“…Vanadium is considered a catalyst for air burn (ISO 12982-1:2000) and, as such, contributes to excess carbon consumption, although this is debated. 19 The alkali and alkali earth elements accumulate in the bath, resulting in the need to periodically tap surplus bath from the cells to maintain the desired composition (NaF/AlF 3 ratio). Since both Na and, to some extent, Ca are introduced to the anodes through recycling of butts, these elements are higher in the baked anodes than indicated in Table I, Na typically > 200 ppm.…”

Effect of Crystallinity on the Wettability of Petroleum Coke by Coal Tar Pitch

“…They explained that the area decreases due to decrease in voids as a result of increase in the graphitization level of coke at higher calcination temperatures . Various researchers reported a clear-cut decrease in electrical resistivity of coke with increasing calcination temperature. ,, Numerous authors have found that final real density of the coke is determined by the final coke calcination temperature and residence time. , In general, undercalcined coke has lower real density and crystalline length compared to anode-grade standard calcined coke ,, shown in Figure .…”

“…Crystalline length is a measure of the rearrangement and alignment of the graphite planes which increases as the calcination temperature increases. − Oberlin described that during calcination from 700 to 1300 °C, the interlayer defects of the basic structural unites of carbon reduce and crystallites start to grow larger and the crystallites are largest at the highest calcination temperature . Coke CO 2 reactivity decreases with increasing crystallite structure due to increase in the size of crystallites .…”