Simulation-assisted design of a distillation train with simultaneous column and sequence optimization

Optimal design and operation of a distillation train plays an important role in the energy and cost reductions. The distillation column structures, operating conditions, and distillation sequence are always interactive, which poses a challenge for optimal design of a distillation train. This work presents a one-step method to perform optimal design of a distillation train considering the interaction of distillation columns and distillation sequence. Rigorous simulation models for all the involved distillation tasks are constructed in Aspen HYSYS. A simulation-optimization model is then established considering product specifications as constraints, aiming to minimize the total annualized cost. To solve the problem effectively, genetic algorithm is modified by incorporating the distillation sequence matrix, which ensures that all possible distillation sequences can be evaluated accurately and reduces the number of decision variables for optimization. A styrene process is studied to illustrate the proposed method, which gives a slightly lower total annualized cost.