Measurement and Improvement of Carbon Anode Properties

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The objective of the current research proposal is to develop methods to characterize the anode behavior (thermal expansion, cracking) during baking, to improve the wettability of coke by pitch, and to decrease the reactivity of anodes made with low sulfur coke. These projects are original and fundamental in nature. Project 1- Improvement of the wettability of coke by pitch using surfactants: Pitch is the binder and has to be mixed well with the dry aggregate. During baking, pitch carbonizes and forms links between the dry aggregate particles. Thus, it has to wet the dry aggregate well which will in turn result in denser anodes. The wetting of coke by pitch involves chemical and physical interactions. Surface functional groups play an important role in wettability. In this project, the effect of surface functional group modifications and addition of surfactants on wettability of coke by pitch will be studied in order to improve the pitch/coke interactions. Wettability experiments will be carried out before and after surface modifications. The carbonization level of pitch will be determined in TGA, and the interactions will be characterized using different techniques such as FTIR and XPS. Project 2- Decreasing the reactivity of anodes made with low sulfur coke: Sulfur (S) plays a significant role in inhibiting the catalytic effects of metals such as vanadium (V) and nickel (Ni) on anode reactivity. On the other hand, approximately 95% of the SO2 emissions generated by smelters can be attributed to S found in the petroleum coke. Therefore, S content of the coke has to be optimized. Many coke suppliers mix high and low S cokes to have an anode-quality coke. The objective of this project is to treat low S cokes so that the anodes produced with them have low anode reactivity in addition to low SO2 emissions. To reduce the reactivity of anodes made with low S coke, it is necessary to add some compounds which can counteract the catalytic activities of transition metals. In this project, different additives will be used. These will be added to the raw materials, and anodes will be made and baked in the UQAC laboratory. Then, the reactivities of these anodes will be tested. Project 3- Measurement of the thermal expansion coefficient (TEC) with image analysis during baking: During baking, anodes go through dimensional changes (expansion around 150-200ºC and contraction as the baking continues). The characterization of these dimensional changes would yield valuable information (especially on cracking) to help improve the anode quality. However, the measurement of TEC is generally carried out for baked anodes. The equipment cannot handle green anodes due to devolatilization. The objective of this project is to measure the dimensional changes of anode samples during baking using the image analysis which is a nonintrusive technique. These data are necessary for modeling the behavior of anodes in the baking furnace. Also, a comprehensive understanding of the factors affecting these changes will help reduce anode cracking. Project 4- Detection of crack formation during baking using audible sound: Cracks in anodes can be investigated indirectly after baking by measuring different properties (such as density) of the anode cores. There are also direct methods such as tomography or microscopy which allow the study of crack formation. All of these approaches indicate cracks of the final product at room temperature, and none shows at which stage of baking the cracks form. This information would reveal the causes of cracks. The objective of this project is to detect the stage and the position of crack formation and growth during baking using audible sound. Such information will help adjust the baking conditions to obtain better anode quality.