A process control algorithm for reaction-diffusion minimum time heating cycles for binder removal from green bodies

Minimum time heating cycles have been simulated for binder removal from ceramic green bodies where the product of binder decomposition exits the green body via diffusion. The model consists of the reaction-diffusion partial differential equation, ordinary differential equations describing the reaction kinetics and a heating function, and algebraic equations, one of which imposes a constraint on concentration or pressure to avoid failure of the green body. Two solution approaches were compared: an earlier approximate method based on the pseudo-steady state assumption combined with a variational calculus algorithm and a new approach based on the finite element method combined with a process control algorithm. The agreement between the two solution strategies reinforces the validity of the pseudo-steady state approximation and the utility of the process control methodology. The latter, which was also applied to problems in which no approximate solution was obtainable, is thus a general method for obtaining minimum time heating cycles.