The determination of the moments of the impulse response of chemical processes from the basic transformed equations

The parameters of simple transfer function models of chemical processes can be obtained from the complex models usually derived by matching the moments of the impulse response of the two models. The most difficult step is the determination of the moments of the complex model. The normal method is to derive from the complex model a transfer function and to differentiate this to obtain the moments αi using the relation An alternative and simpler method is presented which involves deriving the moments by application of this relation directly to the basic transformed equations of the complex model. This makes the moments the dependent variables in the equations which can then be solved by normal methods.