H2. The characteristics of a homogenized reactor for the polymerization of ethylene

Hoftyzer, P. J.; Zwietering, Th.N.

doi:10.1016/0009-2509(61)85081-1

Cited by 39 publications

(12 citation statements)

References 7 publications

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“…A number of researchers have made studies on the analysis of polymerization reactor systems. A majority of these studies focused on the continuous stirred-tank reactor (CSTR) (Goldstein and Hwa, 1966;Goldstein and Amundson, 1965;Zeman and Amundson, 1965;Warden and Amundson, 1962;Hoftyzer and Zwietering, 1961;Thies and Schoeneman, 1970), and relatively few on the tubular reactor ( Mullikin et al, 1965;Cintron-Corder0 et al, 1968).…”

Section: Page 450mentioning

confidence: 97%

“…A stability analysis of the CSTR steady state for free radical addition polymerization systems has also been undertaken by several authors such as Hoftyzer and Zwietering ( 1961), Warden and Amundson (1962), Goldstein and Amundson ( 1965), and Goldstein and Hwa ( 1966). All of these studies have focused on the linearized version of the dynamic equations.…”

Section: Page 450mentioning

confidence: 98%

“…In commercial practice, the high pressure process is undertaken in both autoclaves and tubular reactors. Earlier efforts in analyzing the steady state solutions of the high pressure polyethylene system have been directed either to the continuous stirred-tank reactor or to the ideal case of the tubular reactor, namely the plug flow reactor (Goldstein and Hwa, 1966;Hoftyzer and Zwietering, 1961;Volter, 1963). However, in the commercial operation of high pressure polyethylene tubular reactors, consideration of axial mixing is of practical importance.…”

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Analysis of the high pressure polyethylene tubular reactor with axial mixing

Agrawal

Han

1975

AIChE Journal

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A theoretical study was carried out for the analysis of the high pressure polyethylene tubular reactor with axial mixing (TRAM). In the study, the Contraction Mapping Theorem in the square-integrable function space Lz[O, 11 was first used to derive a uniqueness criterion for the existence of the steady state solution of the polyethylene TRAM. Then, an algorithm was derived which enabled us to compute the profiles of reactor temperature and concentration. Details of reactor performance were investigated in terms of the reactor operating and design variables: heat transfer coefficient, feed temperature and concentration, axial mixing, the length of reactor, and the distribution of preheating and cooling zones of the reactor. Also investigated in this study was the product quality in terms of the number-average molecular weight and molecular weight distribution as affected by change in reactor operating conditions and by the chain transfer reactions. The free-radical polymerization of ethylene at high pressure is a reaction of broad commercial and theoretical interest. In commercial practice, the high pressure process is undertaken in both autoclaves and tubular reactors. Earlier efforts in analyzing the steady state solutions of the high pressure polyethylene system have been directed either to the continuous stirred-tank reactor or to the ideal case of the tubular reactor, namely the plug flow reactor (Goldstein and Hwa, 1966;Hoftyzer and Zwietering, 1961;Volter, 1963). However, in the commercial operation of high pressure polyethylene tubular reactors, consideration of axial mixing is of practical importance. This is because a flow control valve located near the reactor exit is used to give periodic pulsation to prevent the rapid buildup of polymer scale on the reactor wall which would adversely affect the heat transfer coefficient. The pulsations increase axial mixing in the reactor and consequently influences the monomer conversion, temperature profile, and the product quality. SATISHIn the present paper, a theoretical study will be presented which analyzes the performance of the high pressure polyethylene tubular reactor including the effect of axial mixing. For the study, an abstract function space, the square-integrable function space L2[0, 11, was first introduced to derive a uniqueness criterion for the existence of the steady state solution of the system differential equations. Then, the resulting system integral equations were numerically solved by the use of a successive approximation scheme to obtain the profiles of monomer concentration and temperature in the reactor.One of the most important problems encountered in operating a polymerization reactor is to control the product quality, namely the molecular weight and its distribution. Therefore it is of practical importance to develop a simulation model which can predict the product quality as affected by the reactor operating conditions. In the present paper, we shall present some predicted results for the product quality of polyethylene produced by m...

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Section: Page 450mentioning

confidence: 97%

Section: Page 450mentioning

confidence: 98%

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confidence: 99%

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Analysis of the high pressure polyethylene tubular reactor with axial mixing

Agrawal

Han

1975

AIChE Journal

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“…1975; Hoftyzer and Zwietering, 1961) that up to five steady states exist in this system. Autocatalytic behavior of both the polymerization and decomposition make this reactor extremely sensitive to temperature disturbances.…”

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Runaway phenomena in low‐density polyethylene autoclave reactors

1996

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“…Moreover, theoretical investigations have indicated that through the addition of con troller action, stable operation may be obtainable in a continuous reactor. Among these investigations were those by Hoftyzer and Zwietering (1961) and by Warden and Amundson (1962) on thermal-catalytic initiation in a continuous reactor. Comparable work on the other modes of initiation has not been done, although the recent studies by Hashimoto e t al.…”

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Photopolymerization in a continuous stirred‐tank reactor: Experiment

Chen¹,

Kuan²,

Setthachayanon³

et al. 1980

AIChE Journal

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from t=O. However, for k, the standard deviation at t,=O is as high as at t0=34 x and passes through a minimum at to = 11.32 x The selection of the initial state in this case should come as a trade off between gains in the reliability of k2 and losses for kl. It appears that a good compromise is obtained when the starting point t = 11.32 x is used. SUMMARYQuasilinearization algorithm was applied to a typical chemical engineering parameter estimation problem. Using only portions of the data length during the early iterations, as proposed by Wang and Luus (1978), the size of the region of convergence was significantly enlarged. Without the problem of having to have a good initial guess, quasilinearization becomes a very powerful tool for estimating parameters, since it possesses the property of very fast convergence rate and is easy to program.Furthermore, the effect of using different sections of the data during the early iterations was demonstrated. Although a method to obtain the optimum section of the data is not proposed, the effect of using different starting points on the reliability of the estimated parameter values, during the early iterations. was illustrated. NOTATION ei i j J k l = random experimental error associated with state i = index relating to state variable = index relating to point in time = sum of squares of deviations performance index Pa-672

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H2. The characteristics of a homogenized reactor for the polymerization of ethylene

Cited by 39 publications

References 7 publications

Analysis of the high pressure polyethylene tubular reactor with axial mixing

Analysis of the high pressure polyethylene tubular reactor with axial mixing

Runaway phenomena in low‐density polyethylene autoclave reactors

Photopolymerization in a continuous stirred‐tank reactor: Experiment

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