Stabilization of the dynamic behavior of a UNIPOL process for polyethylene production

Ghasem, N.M. and Hussain, M.A. (2004) Stabilization of the dynamic behavior of a UNIPOL process for polyethylene production. Developments in Chemical Engineering and Mineral Processing, 12 (1-2). pp. 199-216. ISSN 0969-1855

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Polyolefins have become one of the most important plastics worldwide due to continuous improvements in catalysts and processes. Gas-phase polymerization of olefins is one of the most important polymerization processes. Compared to other processes such as slurry and solution polymerization, gas-phase processes have many distinct advantages, e.g. reduced capital and operating costs. Moreover, gas-phase polymerization offers a large variety of products, which could not be produced by other processes. However, sheeting and agglomeration of polymer particles are two serious problems, which can occur in modern gas-phase polymerization processes. Overheating of particles may occur due to very high reaction rates. The temperature of a particle can then rise above the softening temperature. In this work, recent theories of bifurcation and chaos are used to analyze the dynamic behavior of the UNIPOL process for the gas-phase production of polyethylene using a Ziegler-Natta catalyst. The dynamic behavior covers a wide range of the design and operating parameters domain for this industrially important unit. A conventional proportional-integral-derivative (PID) controller was implemented to stabilize the desired operating point on the unstable steady-state branch to a certain range of catalyst injection rate. By contrast, it was found that the controlled process can go through a period doubling sequence leading to chaotic strange attractors. The practical implications of this analysis can be very serious, since chaos is shown to exist close to the desired operating point where high polyethylene production rates can be achieved.

Item Type: Article
Additional Information: Export Date: 5 March 2013 Source: Scopus CODEN: DCEPE Language of Original Document: English Correspondence Address: Hussain, M.A.; Department of Chemical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; email: References: Bandyopadhyay, J.K., Kumar, V.R., Kulkarni, B.D., Regulatory control of chaotic non-isothermal CSTR (1993) AIChE J., 39, pp. 908-912; Brindley, J., Kapitaniak, T., Elnaschie, M.S., Analytical conditions for strange chaotic and nonchaotic attractors of quasi periodically forced Van der Pol's equation (1991) Physica D, 51, pp. 28-38; Bukur, G.L., Amundon, N.R., Modelling of fluidized bed reactors-II (1974) Chem. Eng. Sci., 30, pp. 847-858; Bukur, G.L., Amundon, N.R., Fluidized bed combustion kinetic model (1982) Chem. Eng. Sci., 37, pp. 17-25; Choi, K.Y., Ray, W.H., The dynamic behavior of fluidized bed reactors for solid catalyzed gas phase olefin polymerization (1985) Chem. Eng. Sci., 40, pp. 2261-2279; Doedel, E.J., AUTO86 software for continuation and bifurcation problems in ordinary differential equations (1985), Technical Report, California Institute of Technology, PasadenaElnashaie, S.S.E.H., Abashar, M.E., On the chaotic behavior of forced fluidized bed catalytic reactors (1995) Chaos Solitons & Fractals, 5 (5), pp. 797-831; Elnashaie, S.S.E.H., Ibrahim, G., Teymour, F., Chaotic behavior of an acetycholinesterase enzyme system (1995) Chaos Solitons & Fractals, 5 (6), pp. 933-954; Elnashaie, S.S.E.H., Ajbar, A., Period adding and chaos in fluidized bed catalytic reactors (1996) Chaos Solitons & Fractals, 7 (8), pp. 1317-1331; Gear, C.W., (1971) Numerical Initial Value Problems in Ordinary Differential Equations, , Prentice-Hall, New Jersey; Ghasem, N.M., Effect of polymer growth rate and diffusion resistance on the behavior of industrial polyethylene fluidized bed reactor (2001) Chem. Eng. Technol., 24 (10), pp. 1049-1057; Ghasem, N.M., Effect of polymer particle size and inlet gas temperature on the industrial gas phase fluidized bed reactor (1999) Chem. Eng. Technol., 22 (9), pp. 777-783; Jackson, E.A., (1991) Perspectives of Nonlinear Dynamics, , Cambridge University Press, UK; Jaisinghani, R., Ray, W.H., On the dynamic behavior of a class of homogeneous continuous stirred tank polymerization reactors (1977) Chem. Eng. Sci., 32, pp. 811-825; Kapitaniak, T., Elnaschie, M.S., A note on randomness and strange behavior (1991) Physics Letters, 154, pp. 249-253; Kim, J.Y., Laurence, R.L., Mathematical model and analysis of PMMA solution process (1998) Korean J. Chem. Eng., 15 (3), pp. 287-296; Kunii, D., Levenspiel, O., (1991) Fluidization Engineering. 2nd Edn, , Butterworth, USA; Lim, S., Choung, S., Song, K., Studies on the effects of external electron donor in propylene polymerization (1996) Korean J. Chem. Eng., 13 (1), pp. 21-29; McAuley, K.B., Talbot, J.P., Harris, T.J., A comparison of two-phase and well-mixed models for fluidized bed polyethylene reactors (1994) Chem. Eng. Sci., 49 (13), pp. 2035-2045; Schmidt, A.D., Ray, W.H., The dynamic behavior of continuous polymerization reactors: Isothermal solution polymerization in a CSTR (1981) Chem. Eng. Sci., 36, pp. 1401-1410; Shinbrot, T., Grebogi, C., Ott, E., Yorke, J.A., Using small perturbation to control chaos (1993) Nature, 36 (3), pp. 411-420; Teymour, F., Ray, W.H., Chaos, intermittency and hysteresis in the dynamic model of a polymerization reactor (1991) Chaos Solitons & Fractals, 1 (4), pp. 295-315; Teymour, F., Ray, W.H., The dynamic behavior of continuous polymerization reactors. IV. Dynamic stability and bifurcation analysis of experimental reactors (1989) Chem. Eng. Sci., 44 (9), pp. 1967-1982; Teymour, F., Ray, W.H., The dynamic behavior of continuous polymerization reactors. V. Experimental investigation of limit cycle behavior for vinyl acetate polymerization (1992) Chem. Eng. Sci., 47 (15-16), pp. 4133-4145; (1985) Subroutines for Mathematics and Statistics, 1. , Users Manual, FORTRAN; Dgear 1-10, IMSL Inc., Houston, USA
Uncontrolled Keywords: Chaos; Fluidized bed; Instability; PID; Polyethylene; UNIPOL process; Agglomeration; Catalysts; Chemical variables control; Fluidized bed process; Molecular dynamics; Phase diagrams; Polymerization; Temperature; Three term control systems; Gas phase polymerization processes; Polyethylene production; Sheeting; Ziegler-Natta catalysts; Polyethylenes.
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TP Chemical technology
Divisions: Faculty of Engineering
Depositing User: Mr Jenal S
Date Deposited: 10 Jul 2013 06:36
Last Modified: 20 Oct 2014 02:56

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