Rate of Potassium Uptake of Coke from N₂-K_(g) Gas Mixture

Abstract

It is well known that potassium circulates in blast furnaces and that potassium taken up by coke reduces the strength and enhances the reactivity of coke. The kinetics of potassium uptake by coke from gases is fundamental to elucidate accumulation of potassium in coke and contribution of coke to the circulation. The experimental results on the rate of the potassium uptake from N₂-K_(g) gas mixtures with 10^-4 to 10^-3 atm as partial pressures of potassium, in the temperature range from 900 to 1 100°C, have proved that the rate depends on size of coke particle and partial pressure of potassium, and has maximum values in the vicinity of 1000 °C.
The mathematical analysis of the experimental results, assuming the first reversible reaction as the chemical process and taking into account the diffusion of potassium vapor within coke particle, shows that, with raising temperature, the reverse rate constant increases significantly and the equilibrium constant decreases in the similar extent, while the other factors have no significant dependence on temperature. The mathematical model developed here is able to represent, in good agreement with experimental results, not only the overall rate of the potassium uptake but also the concentration profile of potassium within coke particle.