ABSTRACT

In this work, a reactive distillation process for the production of a fuel additive has been modelled, simulated and controlled using proportional-integral-derivative (PID) control method. The fuel additive considered was isopropyl alcohol that was produced from the reaction occurring between propylene and water, with diisopropyl ether as a side product. In accomplishing the work, the ChemCAD model of the process was first developed using SCDS Distillation Column #1 and the fluid package employed was UNIFAC property model. The ChemCAD column had 15 stages where the feed stream for water was the 6th stage and the one propylene was the 10th stage; the section of the column between the two feed streams was the reaction section of the column. After simulating the developed ChemCAD model to convergence, it was converted to dynamic type from which the dynamic responses of the system were generated and used with the aid of MATLAB to develop transfer function model having the reboiler duty, the reflux ratio and the temperature of the bottom product as the input variable, the disturbance and the output variables of the process, respectively. The obtained transfer function of the model was used to develop both open-loop and closed-loop Simulink models for the process that were used to carry out the open-loop and the closed-loop simulations of the process. The closed-loop simulation was carried out with the desire of achieving a fuel additive product with a mole fraction of 0.97. This was accomplished using a PID controller applied inferentially via the product temperature and tuned by trial-and-error technique. It was observed from the results obtained that isopropyl alcohol could be produced successfully from a reaction between propylene and water using reactive distillation suppressing the associated side reaction. It was also found out that it is possible to control the mole fraction of isopropyl alcohol inferentially using bottom temperature because temperature and mole fraction have been found to be dependent on each other. Finally, it has has been shown that a reactive distillation has been controlled to give high purity of isopropyl alcohol of approximately

0.97 mole fraction as the bottom product in the developed reactive distillation column using the PID controller with trial-and-error tuning technique.