Gilbert F. Froment

A DIGITAL COMPUTER CONFIGURATION FOR OPTIMIZED CONTROL OF A THERMAL CRACKING REACTOR

Abstract In the early 1970s a joint research project was started by the Laboratories of Automatic Control and Petrochemische Techniek. The purpose of this project was to develop a control system that optimizes the operation of thermal cracking reactors. Therefore a semi-industrial pilot plant was constructed. For control a powerful PDP 15 digital computer was linked to a PDP 8 process computer near the cracking furnace. The PDP 8 performs all input and output tasks to the process. The PDP 8 sends chemical analysis results and other measurements to the PDP 15. This last computer performs then control and optimization calculations and sends new temperature set points to the PDP 8. The hierarchical control structure is mainly divided in three levels. On the lowest level temperatures are controlled. On an intermediate control level pressure measurements are used to detect disturbances before they are measured with the slow gas chromatographs. The parameters of this inferential control algorithm can be tuned via a black box approach or based on the available physico-chemical models. On the highest level the gas chromatograph results are used to control the disturbances that are not compensated for by the inferential controller. As will be shown in the paper the results of the hierarchical control system are very promising