This paper describes the implementation of a self‐tuning controller (STC) on a bench‐scale tube‐wall reactor for the Fischer‐Tropsch synthesis using a plasma‐sprayed iron catalyst. The concentration of the hydrocarbons in the C10 range in the reactor effluent was controlled by manipulating the H2/CO ratio of the inlet synthesis gas. The output of the self‐tuner was cascaded to two PI‐controllers which maintained a constant total inlet gas flow rate as well as ensuring the desired H2/CO ratio. The concentration measurement was performed by an on‐line gas chromatograph with an analysis time of approximately 30 s. The performance of the STC in set‐point tracking, rejection of randomly occurring deterministic disturbances, and estimation and adaptation to the unknown process dead time was investigated. The STC was able to reduce the variance of the process output and of the manipulated variable when compared to the variances obtained with a PI‐controller.

A single variable pole-placement self-tuning controller (PPSTC) is used to simulate examples typical of chemical processes; i.e., open-loop stable, unstable, and unstable non-minimum phase systems with unknown varying process dead time. The PPSTC is shown to be effective in each case. Set-point tracking and rejection of randomly occurring deterministic disturbances for all three types of processes are achieved. Simultaneous estimation of process parameters and process time delay is realized by using a recursive extended least squares method.