A steady-state analysis method for optimal operation of dividing-wall column. (2nd November 2018)

• Record Type: Journal Article
• Authors: Luo, Junwen; Xu, Chunjian; Zhang, Yawen; Yan, Kaixin; Zhu, Jesse
• Is Part Of: Computers & chemical engineering. Volume 119(2018)
• Page Start: 112
• Page End: 127
• Publication Date: 2018-11-02
• Subjects: Dividing-wall column -- Optimal operation -- Online optimization -- Feedback -- Sensitivity analysis -- Steady state; A light component -- B middle component -- C heavy component -- xA mole fraction of A in feed -- xB mole fraction of B in feed -- xC mole fraction of C in feed -- DWC dividing-wall column -- Q energy consumption -- LQR low energy consumption region -- F feed condition -- MV manipulated variable -- MVO manipulated variable for optimization -- MVLQR manipulated variables low energy consumption region -- CV controlled variable -- CVLQR controlled variables low energy consumption region -- HVLQR hybrid variables low energy consumption region -- Lmp liquid flow entering the top of prefractionator from the main column -- Vmp vapor flow entering the bottom of prefractionator form main column -- RL the ratio of Lmp to liquid flow above the dividing wall -- RV the ratio of Lmp to liquid flow above the dividing wall -- xpm, A the mole fraction of light component A in liquid flow entering the main column from the bottom of prefractionator -- ypm, C the mole fraction of heavy component C in vapor flow entering the main column from the top of prefractionator -- k the degree of closeness between Q and Qmin -- kmin, mode 0 the kmin under Mode 0 -- kmin, mode 1 the kmin under Mode 1 -- kmin, mode 2 the kmin under Mode 2 -- kFBmin, mode 1 the kmin under Mode 1, when feedback is used for online optimization -- kFBmin, mode 2 the kmin under Mode 2, when feedback is used for online optimization -- kIEmin, mode 1 the kmin under Mode 1, when implementation error and disturbance are considered simultaneously and feedback is used for online optimization -- kIEmin, mode 2 the kmin under Mode 2, when implementation error and disturbance are considered simultaneously and feedback is used for online optimization; Chemical engineering -- Data processing -- Periodicals; 660.0285
• DOI: 10.1016/j.compchemeng.2018.05.010
• Languages: English
• ISSNs: 0098-1354

Abstract

Highlights: Whether the optimal operation of dividing-wall column (DWC) can be realized without adjusting vapor split ratio can be determined. For ternary separation, dilution effect in DWC is proposed. It reveals DWC may need online optimization. Feedback is used for the online optimization of DWC. The relation between degree of closeness (between energy consumption ( Q ) and Q min ) and setpoint range of manipulated variable/control variable can be acquired. Disturbance and implementation error can be handled by using the proposed method. Abstract: Optimal operation indicates energy consumption ( Q ) close to its Q min while product specifications are satisfied. Generally, for DWC, there are two manipulated variables (MVs) to keep Q close to Q min . Therefore, there are three operation mode, which are two MVs online optimization (Mode 2), single MV online optimization (Mode 1) and two MVs fixed (Mode 0). A steady-state analysis method for optimal operation of DWC with disturbance is presented. In the method, whether optimal operation can be achieved under Mode 0/ Mode 1 can be determined. Feedback is used for the online optimization under Mode 1 and Mode 2. The relation between degree of closeness (between Q and Q min ) and setpoint range of manipulated variable/control variable can be acquired. For ternary separation, dilution effect in DWC is proposed. It reveals DWC may need online optimization. Implementation error is discussed. Disturbance and implementation error can be handled by using the proposed method simultaneously. The important ternary separation of benzene, toluene, and o-xylene in industry is used as an example to illustrate the method. In the case, optimal operation can be realized under Mode 1 and Mode 2.