Solution of models for gassolid noncatalytic reactions by orthogonal collocation on finite elements with moving boundary

A variable size grain model is used to describe gassolid non-catalytic reactions which are accompanied by change in solid structure. A finite element collocation method with a moving boundary is developed to describe gas and solid concentration profiles in the reacting pellet and to compute conversion-time relationships. Such a method is necessary in case of structural changes which lead to complete pore mouth blockage and gives good results until such blockage occurs. A modified shrinking core model is used as an approximation after the time at which complete pore mouth closure occurs. The developed computational algorithms show that the effect of structural changes on time-conversion relationship is significant.