Abstract: For the renovation project of C₈ and C₉ aromatic hydrocarbon distillation units, simulation design was carried out using conventional two tower process and distillation tower process with side lines, and non dominated sorting genetic algorithm was used to optimize the process. Firstly, simulations were conducted on the conventional two tower process for the C₈ and C₉ removal towers. When the purity (w) indicators of C₈ and C₉ products were required to be 0.98 and 0.9999, respectively, the total heat load of the conventional two tower process reboiler was calculated to be 33.52 MW. Then, the conventional two tower process was optimized, and the total heat load of the optimized two tower reboiler was 23.40 MW. Furthermore, a single-sided line extraction process and a double-sided line extraction process were constructed separately, and the steady-state structure of the distillation tower was optimized. It was found that, while meeting the purity requirements, the total heat load of the reboiler using both single-sided and double-sided distillation processes was significantly reduced, to 21.86 MW and 21.55 MW, respectively. Finally, the single-sided process with better structural controllability was selected, and simulations were conducted for temperature dynamic control structure and temperature side flow ratio dynamic control structure. The results showed that both the temperature control structure and the temperature side line proportional control structure can effectively cope with dynamic control of feed flow rate ±10% disturbance and feed composition (w) ±5% disturbance, while the steady-state deviation of the temperature side line proportional control structure was smaller.

Key words: aromatic hydrocarbon separation, side line distillation, dynamic control