ABSTRACT
An important question in the chemical industry is if it is possible to estimate important variables based on a limited number of measurements. without model and measurements an estimation of the concentration profile is impossible. A large number of estimation methods that all start with a state model has been developed. Energy, momentum, and continuity equations often have this form, and, in case of distributed processes, it is a matter of discretization with respect to the geometric coordinates. Algebraic relationships have to be substituted into the differential equations. Sometimes the differential equations have derivatives of more than one variable; in that case one has to separate these derivatives in the left-hand side of the equation.
