Self‐Tuning control of fischer‐tropsch synthesis in a tube‐wall reactor

Abstract

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.