Air Reactivity of Petroleum Cokes:  Role of Inaccessible Porosity

Abstract

This paper presents a detailed study of the air reactivity of petroleum cokes measured at temperatures between 400 and 600 °C using a combination of characterization techniques and reactivity measurements. The microstructure of the coke was found to comprise an essentially inaccessible pore system at low temperatures of 77−273 K used in characterization, and it is more accessible to oxygen at higher temperatures of about 773 K used in oxidation. The correlation of reactivity data using the random pore model suggests that the true micropore area is significantly larger than that measured using physical gas adsorption methods. The difference in surface area can be attributed to the low kinetic energy of gas molecules at the lower temperatures of characterization; as a result, they are unable to overcome the pore mouth energy barrier. By examining the variation of coke structure with burnoff level, we find that most of the internal reaction occurs in pores in the narrow pore width range 1−2 nm. For pores greater than 2 nm, however, the surface areas remains essentially constant with burnoff level. The apparent activation energy of the coke-air reaction derived from the extracted rate constants falls in the range 145−160 kJ/mol.

Characterization of carbon anode constituents under CO 2 gasification: A try to understand the dusting phenomenon

“…The CO 2 surface area of coke, butt and anode significantly increases up to 55% of gasification while that of the pitch remains constant. These results are in accordance with the observations reported by Tran et al [51] and Feng and Bhatia [31] speculating that while the micropores are not accessible for CO 2 molecules at the beginning of gasification, they become so as the gasification progresses. During the gasification, the pores smaller than 1 nm (pore size defined by Tran et al [51]) open gradually and the surface area measured by CO 2 increases.…”

Evolution of Anode Porosity under Air Oxidation: The Unveiling of the Active Pore Size

“…The rate of reaction increased gradually between 0 and 70 wt % of gasification and decreased between 70 and 80 wt %. This trend of apparent reaction rate exhibiting a maximum has often been remarked in carbon consumption studies in the literature [32,[44][45][46][47]. Bhatia and Perlmutter [46] and Ballal and Zygouraki [47] explained the maximum rate with the combination of two opposite effects: the augmentation of the reactive surface with pore growth and pore accessibility, and the disappearance of this surface area with pore coalescence and consumption of carbon material.…”

Réactivité de l'anode et désulfuration :

“…Malgré le nombre important d'études consacrées à ce sujet, il existe encore des divergences d'opinions en ce qui a trait à la réactivité. En effet, pour certains auteurs [25], la réactivité est fortement reliée à la longueur cristalline (Le) tandis que pour d'autres la réactivité est plutôt reliée à la surface accessible [13,[15][16][17][18][19].…”

“…En ce qui concerne la réactivité au CO 2 de l'anode, il semble exister des contradictions dans la littérature [1,2,[25][26][27][28]. Certaines études démontrent que la sous-calcination du coke est bénéfique pour les propriétés de l'anode [1,2,28,25], d'autres en viennent à la conclusion inverse [27] et d'autres suggèrent qu'il n'y a pas de lien entre la sous-calcination du coke et la réactivité anodique [26].…”

“…Certaines études démontrent que la sous-calcination du coke est bénéfique pour les propriétés de l'anode [1,2,28,25], d'autres en viennent à la conclusion inverse [27] et d'autres suggèrent qu'il n'y a pas de lien entre la sous-calcination du coke et la réactivité anodique [26]. Il est alors impératif d'éclaircir ce point pour mieux comprendre les paramètres qui sont responsables de la réactivité du coke et de l'anode.…”