Dynamic Simulation and Control of a Complete Industrial Acetic Acid Solvent Dehydration System in Purified Terephthalic Acid Production

In the production of purified terephthalic acid (PTA), the acetic acid solvent dehydration system is a typical heterogeneous azeotropic distillation system. In this work, a rigorous process simulation of the complete industrial acetic acid solvent dehydration process is conducted. To achieve both the bottom- and top-product specifications, remove the accumulated p-xylene (PX), and recycle the methyl acetate (MA) despite feed flow rate disturbances, a suitable control strategy of this complete system is proposed. The control strategy requires only a side draw and organic reflux to control the tray temperatures of the dehydration column, the bottom heating steam to control the tray temperature of the PX purification column, and top-product reflux to control the tray temperature of the entrainer recovery column; this strategy can be easily implemented in industry for wider applications. From dynamic simulation and analysis, the control strategy can maintain the product purities, overcome the drawback of the PX imbalance, achieve the transition to the desired operation more quickly, and better maintain the stability of the overall solvent dehydration system under a disturbance in the upper-zone feed streams.