Abstract:
The control of industrial dual high-purity methanol distillation columns is complicated since there are non-linearities involved. Due to economic factors, these distillation columns have strict product ethanol specification (less than 10 ppm), and require a high level of product recovery. Because of environmental factors the bottoms flow cannot contain more than 5 ppm of methanol for a prolonged period. Industrial methanol producers achieve this target by over refluxing the distillation column which creates a plant bottleneck. In this work, a control scheme was proposed to control a real life industrial dual high-purity methanol distillation column without exceeding specifications set by a commercial methanol producer with minimal reflux ratio. The control scheme keeps the product specification at the top by controlling the product flow, while an ethanol profile composition analyser located nearby the side draw is used to control the reboiler duty. The simulation results show that the proposed method can provide a reliable set-point track performance.