Constant Thickness Porous Layer Model for Reaction between Gas and Dense Carbonaceous Materials

Using oil-sands petroleum coke as the raw material and sulfur dioxide as the activating agent at 700 °C, the process of pore development in dense carbonaceous materials was studied. The time dependence of porosity was established from measured values of specific surface area (SSA), which could not be explained using conventional porous layer theories. Incorporating the Random Pore Model with measurements of particle size and porous layer thickness, a model was developed based on the existence of a porous layer of constant thickness. The model was found to accurately reproduce experimental time dependence of SSA. The results confirm a constant thickness of the porous layer for the activation conditions studied, which results from competing effects of carbon gasification reaction and penetration of the activating agent into the carbon particle interior. The model predicts a higher achievable SSA for a greater constant porous layer thickness, smaller initial particle size, and lower inorganic ash content. This model was found to be useful in predicting the maximum porous layer thickness of a dense material undergoing activation or gasification using only measured values of SSA, pore size distribution, and particle size as inputs.