Design and optimization of energy-efficient liquid-only side-stream distillation configurations using a stochastic algorithm

The liquid-only side-stream option is sometimes preferred to replace the vapor–liquid interconnection in thermally coupled distillation to achieve similar energy efficiency but easier controlling. This work enumerates all possible liquid-only type distillation sequences for ternary systems before a fair comparison of them, through a case study of equimolar BTX (benzene–toluene–xylene) mixture. The optimization problem can be formulated as a mixed integer nonlinear programming (MINLP). A self-adapting dynamic differential evolution (SADDE) algorithm is used to address its difficulties from inherent nonlinearity and nonconvexity. This stochastic optimization algorithm, written in MATLAB, is linked to Aspen Plus to ensure calculation accuracy. Evaluation and comparison of ten configuration varieties verify the outperformance of liquid-only type configurations over simple distillation sequences with main equipment in common, saving both in energy and economic cost.