An improved isoenergetic-isochoric flash algorithm and its application in the dynamic simulation of distillation column

Although UV flash is currently the most rigorous flash algorithm in the field of dynamic simulation, the algorithm suffers from problems such as poor stability and significant solution errors. By fully considering the influence of composition changes on various factors in the separation process, the traditional UV flash algorithm has been improved by simplifying the iterative equations and optimizing the calculation order, and applied to the dynamic simulation of distillation columns. A dynamic simulation model of distillation columns based on the improved UV flash algorithm was proposed. The improved UV flash algorithm was verified using four flash cases under different operating conditions and one actual industrial distillation column case. The results show that the improved UV flash algorithm outperforms the traditional UV flash algorithm in terms of computational efficiency, accuracy and robustness. Compared with the conventional UV flash algorithm, the calculation results for the distillation column model based on the improved UV flash algorithm are closer to the simulation results of the HYSYS distillation column dynamic model. The calculation time is reduced from 1.331 s to 0.310 s, and the relative errors of the simulation results of the intensity variable and the final product composition are less than 1% and 1.5%, respectively. The results show that the improved UV flash algorithm is more suitable for calculations of the dynamic simulation of a distillation column, and can provide a reliable flash algorithm for the establishment of a digital twin model of the dynamic process in a distillation column.