A numerical method is proposed to tackle the continuous optimal contro
l problems involving industrial thermal processes. The latter are char
acterized by their complex mathematical models. Formulated through var
iational calculus using the Pontryagin maximum principle, the resultin
g two-point boundary value problem is discretized with a Euler central
differentiation scheme. Solution is obtained by the Newton-Raphson me
thod, and Richardson extrapolation is used to increase accuracy and re
fine the grid automatically as needed. The Jacobian matrix is evaluate
d numerically. The program, named COMMIN, helps reduce considerably th
e heavy mathematical development and the ensuing programming work, stu
mbling blocks for process engineers faced with optimal control problem
s. An example is worked out. This new method promises to open new poss
ibilities for applications in an important class of engineering proble
ms.