Temporal variations of unreacted core shape and its effects on total reaction rate for gas-solid reaction

It is investigated in the present paper how an initially nonspherical parti cle in a shrinking core regime changes its shape temporally, and how much t he eccentricity of the particle affects the total reaction rate (i.e., conv ersion), The pseudo-steady state assumption may be applied because the core shrinking rate is sufficiently low. The resultant Laplace equation is solv ed by using the boundary element method to yield the reactant concentration s on the core, which are then used to predict the shrinking process of the core, The shape change of a spheroidal core is also analytically predicted with asymptotic analysis. It is shown that the two different approaches pro duce equal results. The spheroidal core becomes more and more eccentric wit h time, to be very slender when the core size is much reduced. The more non spherical the particle, the faster the total reaction rate. For a highly no nspherical particle with an aspect ratio of 3.2, one may undergo about 17% error in determining the reaction constant if the spherical core is employe d in the data analysis.