Influence of Potassium on the Rate of Boudouard Reaction of Coke
Saburo KOBAYASHI, Yasuo OMORI
In order to reveal influence of potassium, taken up by coke particles from N2-K(g) gas mixture, on the overall rate of Boundouard reaction of coke, a mathematical model is developed. The three unknown parameters for the catalytic action of potassium, contained in this model, are fitted to the experimental data of the overall rate. The temperature dependences of these parameters show that the catalytic action lowers with raising temperature. Potassium reduces both the apparent activation energy and the frequency factor for the reaction; the former lowers considerably with increase in potassium content in the range less than 1 wt%.
The model is able to make estimation on extent of the reaction zone in the particles. The local concentration of the reaction on the outer shell of particle, due to the rate-enhancing effect of potassium, is considered to reduce the strength of carbon matrix in this portion. Although non-homogenity of the concentration profiles of potassium and carbon dioxide within coke particles complicates quantitative relationship between the overall rate and amount of potassium taken up, a simple empircal expression representing the relation is obtained.