Optimal Operation of a DWC by Self-Optimizing Control: Active Vapor Split Approach

Document Type: Research Article

Author

Faculty of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood, I.R. IRAN

Abstract

Dividing Wall Column(DWC) offers the large potential for operating and capital cost saving in compared with conventional distillation sequence. In the studied DWC in this study, the aid of Vmin diagrams, it is shown that without a suitable value for vapor split fraction bellow the dividing wall in different operating conditions, the energy requirement increases from optimal value and it will lead to the suboptimal operation. Accordingly, a control structure based on
the self-optimizing concept is designed using vapor split fraction as the control degree of freedom (active vapor split). To find the best self-optimizing Controlled Variables (CV) the exact local method is used. It is shown that the value of loss with the aid of active vapor split is lower than 0.7 percent of nominal value with using the conventional single measurement self-optimizing CV, which is a reasonably small value, and using a more complex combination of measurement as a self-optimizing CV provides a little enhancement in reducing the loss. So, including vapor split fraction in the self-optimizing control structure of the DWC can save energy and in the meantime avoid the complexity of combination of measurement. Moreover, the dynamic simulation studies show that the proposed control structure with the simple decentralized control loops can conveniently stabilize the plant and reject the effects of disturbances.

Keywords

Main Subjects


[1] Kiss A.A., Distillation Technology – Still Young and Full of Breakthrough Opportunities, Journal of Chemical Technology and Biotechnology, 89: 479-498 (2014).

[2] Li H., Wu Y., Li X., Gao X., State-Of-The-Art of Advanced Distillation Technologies in China, Chemical Engineering Technology, 39(5): 815-833 (2016).

[3] Kiss A.A., “Advanced Distillation Technologies - Design, Control and Applications”, John Wiley and Sons, Inc. (2013).

[4] Kiss A.A., Novel Applications of Dividing-Wall Column Technology to Biofuel Production Processes, Journal of Chemical Technology and Biotechnology, 88(8): 1387-1404 (2013).

[6] Schultz M., Stewart D.G., Harris J.M., Rosenblum S.P., Shakur M.S., Obrien D.E., Reduce Costs with Dividing-Wall Columns, Chemical Engineering Progress, 98: 64-71 (2002).

[7] Yildirim O., Kiss A.A., Kenig E.Y., Dividing Wall Columns in Chemical Process Industry: A Review on Current Activities, Separation and Purification Technology, 80: 403–417 (2011).

[8] Staak D., Grutzner T., Schwegler B., Roederer D., Dividing Wall Column for Industrial Multi Purpose Use, Chemical Engineering and Processing: Process Intensification, 75: 48– 57 (2014).

[9] Donahue M.M., Roach B.J., Downs J.J., Blevins T., Baldea M., Eldridge R.B., Dividing Wall Column Control: Common Practices and Key Findings, Chemical Engineering and Processing: Process Intensification, 107: 106-115 (2016).

[10] Kaibel B., “Dividing-Wall Columns, in Distillation: Equipment and Processes”, Editor, Gorak A., Olujic Z., Academic Press(2014).

[11] Ehlers C., Egger T., Fieg G., Experimental Operation of a Reactive Dividing Wall Column and Comparison with Simulation Results, AIChE Journal, 63(3): 1036-1050 (2017).

[12] Schroder M., Ehlers C., Fieg G., A Comprehensive Analysis on the Reactive Dividing-Wall Column, Its Minimum Energy Demand, and Energy-Saving Potential, Chemical Engineering Technology, 39(12): 2323-2338 (2016).

[13] Schroder M., Fieg G., Influence of Reaction System Properties on the Energy Saving Potential of the Reactive Dividing-Wall Column: Separation Properties, Chemical Engineering Technology, 39(12): 2265-2272 (2016).

[14] Dai X., Ye Q., Qin J., Yu H., Suo X., Li R., Energy-Saving Dividing-Wall Column Design and Control for Benzene Extraction Distillation via Mixed Entrainer, Chemical Engineering and Processing: Process Intensification, 100: 49–64 (2016).

[15] Kiss A.A., Luo H., Bildea C.S., Energy Efficient Bioethanol Purification by Heat Pump Assisted Extractive Distillation, Computer Aided Chemical Engineering, 37: 1307-1312 (2015).

[16] Le Q.K., Halvorsen I.J., Pajalic O., Skogestad S., Dividing Wall Columns for Heterogeneous Azeotropic Distillation, Chemical Engineering Research and Design, 99: 111-119 (2015).

[17] Kiss A.A., Suszwalak D.J.P.C., Enhanced Bioethanol Dehydration by Extractive and Azeotropic Distillation in Dividing-Wall Columns, Separation and Purification Technology, 86: 70-78 (2012).

[18] Li R., Ye Q., Suo X., Dai X., Yu H., Feng S., Xia H., Improving the Performance of Heat Pump-Assisted Azeotropic Dividing Wall Distillation, Industrial and Engineering Chemistry Research, 55(22): 6454–6464 (2016).

[19] Jobson M., Dividing Wall Distillation Comes of Age, The Chemical Ehgineering, 766: 30-31 (2005).

[20] Rodríguez-Angeles M.A., Gomez-Castro F.I., Segovia-Hernandez J.G., Uribe-Ramírez A.R., Mechanical Design and Hydrodynamic Analysis of Sieve Trays in a Dividing Wall Column for a Hydrocarbon Mixture, Chemical Engineering and Processing: Process Intensification, 97: 55–65 (2015).

[21] Okoli C.O., Adams T.A., Design of Dividing Wall Columns for Butanol Recovery in a Thermochemical Biomass to Butanol Process, Chemical Engineering and Processing: Process Intensification, 95: 302–316 (2015).

[22] Liu Y., Zhai J., Li L., Sun L., Zhai C., Heat Pump Assisted Reactive and Azeotropic Distillations in Dividing Wall Columns, Chemical Engineering and Processing: Process Intensification, 95: 289–301 (2015).

[23] Benyounes H., Benyahia K., Shen W., Gerbaud V., Novel Procedure for Assessment of Feasible Design Parameters of Dividing-Wall Columns: Application to Non-Azeotropic Mixtures, Industrial and Engineering Chemistry Research, 54(19): 5307–5318 (2015).

[24] Ehlers C., Schroder M., Fieg G., Influence of Heat Transfer Across the Wall of Dividing Wall Columns on Energy Demand, AIChE Journal, 61(5): 1648-1662 (2015).

[25] Gorak A., Olujic Z., Distillation: Equipment and Processes, Academic Press (2014).

[26] Arjomand A., Fanaei M.A., Optimal Operation of a Three-Product Dividing-Wall Column with Self-Optimizing Control Structure Design, Iranian Journal of Chemistry and Chemical Engineering (IJCCE), 34(1): 107-117 (2015).

[27] Ramapriya G.M., Tawarmalani M., Agrawal R., Thermal Coupling Links to Liquid-Only Transfer Streams: An Enumeration Method for New FTC Dividing Wall Columns, AIChE journal, 62(4): 1200–1211 (2015).

[28] Sun J., Ge H., Chen W., Chen N., Chen X., CFD Simulation and Experimental Study on Vapour Splitter in Packed Divided Wall Column, The Canadian Journal of Chemical Engineering, 93(12): 2261–2265 (2015).

[29] Huaqiang G., Xiangwu C., Nan C., Wenyi C., Experimental Study on Vapour Splitter in Packed Divided Wall Column, Journal of Chemical Technology and Biotechnology, 91(2): 449–455 (2016).

[30] Dwivedi D., Strandberg J.P., Halvorsen I.J., Preisig H.A., Skogestad S., Active Vapor Split Control for Dividing-Wall Columns, Industrial and Engineering Chemistry Research, 51(46): 15176–15183 (2012).

[31] Ling H., Luyben W.L., New Control Structure for Divided-Wall Columns, Industrial and Engineering Chemistry Research, 48: 6034-6049 (2009).

[32] Halvorsen I.J., Minimum Energy Requirements in Complex Distillation Arrangements, Ph.D. Thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, (2001).

[33] Underwood A.J.V., Fractional Distillation of Multi-Component Mixtures, Industrial and Engineering Chemistry Research, 41(12): 2844-2847 (1949).

[34] Poling B.E., Prausnitz J.M., O'Connell J.P., The Properties of Gases and Liquids, McGraw-Hill (2001).

[35] Fidkowski Z., Krolikowski L., Thermally Coupled System of Distillation Columns: Optimization Procedure, AIChE journal, 32(4): 537-546 (1986).

[36] Dejanovic I., Matijasevic L.J., Olujic Z., Dividing Wall Column-A Breakthrough Towards Sustainable Distilling, Chemical Engineering and Processing: Process Intensification, 49: 559-580 (2010).

[37] Mutalib M.I.A., Smith R., Operation and Control of Dividing Wall Distillation Columns Part1: Degrees of Freedom and Dynamic Simulation, Trans IChemE, 76(Part A): 308-318 (1998).

[38] Skogestad S., Plantwide Control: The Search for the Self-Optimizing Control Structure, Journal of Process Control, 10(5): 487-507 (2000).

[39] Halvorsen I.J., Skogestad S., Morud J.C., Alstad V., Optimal Selection of Controlled Variables, Industrial and Engineering Chemistry Research, 42: 3273-3284 (2003).

[40] Kariwala V., Cao Y., Bidirectional Branch and Bound for Controlled Variable Selection. Part II: Exact Local Method for Self-Optimizing Control, Computers and Chemical Engineering, 33: 1402-1412 (2009).

[41] Alstad V., Skogestad S., Hori E.S., Optimal Measurement Combinations as Controlled Variables, Journal of Process Control, 19: 138-148 (2008).

[42] Kiss A.A., Rewagada R.R., Energy Efficient Control of a BTX Dividing-Wall Column, Computers and Chemical Engineering, 35: 2896-2904 (2011).

[43] Skogestad S., Simple Analytic Rules for Model Reduction and PID Controller Tuning, Journal of Process Control, 13: 291-309 (2003).

[44] Panahi M., Skogestad S., Selection of Controlled Variables for a Natural Gas to Liquids Process, Industrial and Engineering Chemistry Research, 51: 10179−10190 (2012).