ASTM D6558-00A(2015)e1

5.1 The CO₂ reactivity rates are used to quantify the tendency of a carbon artifact to react with carbon dioxide. Carbon consumed by these unwanted side reactions is unavailable for the primary reactions of reducing alumina to the primary metal. CO₂ dusting rates are used to quantify the tendency of the coke aggregate or binder coke of a carbon artifact to selectively react with these gases. Preferential attack of the binder coke or coke aggregate of a carbon artifact by these gases causes some carbon to fall off or dust, making the carbon unavailable for the primary reaction of reducing alumina and, more importantly, reducing the efficiency of the aluminum reduction cell.

5.2 Comparison of CO₂ reactivity and dusting rates is useful in selecting raw materials for the manufacture of commercial anodes for specific smelting technologies in the aluminum reduction industry.

5.3 CO₂ reactivity rates are used for evaluating effectiveness and beneficiation processes or for research purposes.

1.1 This test method covers the thermogravimetric (TGA) determination of CO₂ reactivity and dusting of shaped carbon anodes and cathode blocks used in the aluminum reduction industry. The apparatus selection covers a significant variety of types with various thermal conditions, sample size capability, materials of construction, and procedures for determining the mass loss and subsequent rate of reaction. This test method standardizes the variables of sample dimensions, reaction temperature, gas velocity over the exposed surfaces, and reaction time such that results obtained on different apparatuses are correlatable.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.