The Gasification Reactivity of Carbons - New Developments

The reactions of chars (or “carbons”) with oxidizing gases are among the most important of industrial reactions. Basic to utilization of any solid fuel, and important in processes ranging from activated carbon production to steel-making, they have been extensively studied for more than a century, e.g., 1,2. It is a tribute to the complexity of the processes involved that they have not yet yielded to intensive study, and a quantitatively predictive description of the phenomenon is not yet in hand. The difficulties in developing such a quantitative description are well-known. First, the materials from which the carbons are derived leave an indelible imprint on their character. Second, the temperature history of their preparation also has a significant impact. Modeling the complexity of the relevant pyrolysis processes still represents an imposing challenge (see the presentation by Serio et al. in this symposium). Third, the presence of small amounts of additional elements, serving as catalytic agents, influence both the course of carbon formation and subsequent gasification behavior. Finally, subtle aspects of combined phase and reaction behavior can drive the morphology of the carbons across a wide spectrum of characteristics (see the presentations by Hurt et al. and Winans et al. in this symposium). These morphological differences also play a key role in the subsequent reaction behavior of the carbons, as it is the ability of the oxidizing gases to gain access to the porosity in the carbon which determines some key aspects of the reaction process. Improvements in the quantitative description of these phenomena will require experimental examination of all of these processes at a greater level of detail. No single study will be able to provide all of the pieces, and progress will continue to be achieved through many fundamental examinations of various aspects of the processes. In this presentation, a key focal point will be the question of how porosity develops during gasification processes, and what this tells us about several of the above issues.