Chinese Journal of Chemical Engineering ›› 2021, Vol. 29 ›› Issue (1): 266-278.doi: 10.1016/j.cjche.2020.08.051

• Process Systems Engineering and Process Safety • Previous Articles     Next Articles

Enhanced temperature difference control of distillation columns based on the averaged absolute variation magnitude

Yang Yuan, Kejin Huang, Xing Qian, Haisheng Chen, Lijing Zang, Liang Zhang   

  1. College of Information Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China
  • Received:2020-02-10 Revised:2020-07-08 Online:2021-01-28 Published:2021-04-02
  • Contact: Kejin Huang
  • Supported by:
    The research funding is from China Postdoctoral Science Foundation (No. 2019M650453), Fundamental Research Funds for the Central Universities (ZY1930), National Natural Science Foundation of China (21808007, 21878011, 21676011, and 21576014), and Open Foundation of State Key Laboratory of Chemical Engineering (No. SKL-ChE-18B01).

Abstract: Temperature difference control (TDC) schemes can clearly suppress the adverse influence of pressure variations on product quality control of various distillation columns (DCs) by employing temperature differences (TDs) between the sensitive stage temperature (TS) and reference stage temperature (TR), i.e., TS-TR, to infer the controlled product qualities. However, because the TDC scheme has failed to specially take the corresponding relationship between the TD employed in each control loop and the controlled product quality into account, it may suffer from relatively large steady-state errors in the controlled product qualities. To address this problem, an enhanced TDC (ETDC) scheme is proposed in the current article, in which an enhanced TD (ETD), i.e., TS-α×TR, is employed to replace the conventional TD for each control loop. While the locations of the sensitive and reference stages of the ETD are respectively determined according to sensitivity analysis and SVD analysis, the adjusted coefficient α is set to be the ratio between the averaged absolute variation magnitudes (AAVMs) of the TS and TR so that the relationship between the TS and TR can be appropriately coordinated. With reference to the operations of three different distillation systems, i.e., one conventional DC distilling an ethanol (E)/butanol (B) binary mixture, one conventional DC distilling an E/propanol (P)/B ternary mixture, and one dividing-wall distillation column distilling an E/P/B ternary mixture, the performance of the ETDC scheme is assessed by compared with the conventional TDC scheme and the double TD control (DTDC) scheme. The dynamic simulation results show that the ETDC scheme is better than the conventional TDC scheme with reduced steady-state errors in the controlled product qualities and improved dynamic responses, and is comparable with the DTDC scheme despite the less temperature measurements are employed.

Key words: Distillation column, Temperature difference, AAVM, Temperature inferential control, Process control