Abstract: In order to solve some problems existed in the fractionation section of paraxylene unit, state space models for xylene column and its reboiler furnaces in the section were set up by analyzing the mechanism and the influence factors. Based on the predictive control theory, advanced process control system was developed and applied in the section. The operation stability of the unit was improved significantly and the energy consumption was reduced, e.g. the energy consumption of the reboiler furnaces reduced 265 MJ for per ton paraxylene, thus a production cost of 5.6 MRMB was saved annually.

Key words: advanced process control, paraxylene unit, state space model, xylene column, application