Simulation and optimization of polymer molecular weight distribution with nonideal reactors

Zhang, Chi; Shao, Zili; Chu, Xiaoyu; Xu, Chengyun; Wang, Jiajun; Feng, Lianfang

doi:10.1016/j.compchemeng.2017.03.017

Cited by 11 publications

(7 citation statements)

References 28 publications

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“…1, 4-7, and 22-29), population balance equations of all the other species (Eqs. [10][11][12][13][14][15][16][17][18][19], and dynamic MWD calculation (Eqs. [30][31][32].…”

Section: Single-stage Formulationmentioning

confidence: 99%

“…Using this EO model as a basis, a fully connected process superstructure was generalized, with which the optimal reactor network configurations with specifications on MWDs were determined. Zhang et al 18 used computational fluid dynamics (CFD) software to develop ideal and nonideal reactors models for the low-density polyethylene process, and compare the optimal operating conditions given the specified MWD.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic optimization for grade transition processes using orthogonal collocation on molecular weight distribution

Chen

Eason

et al. 2019

AIChE Journal

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To meet the demands of a competitive market, an industrial plant often produces several grades of polymer product through the same process in an economical way. As molecular weight distribution (MWD) is a crucial quality index of polymers, dynamic optimization for grade transition based on MWD is highly important, but challenging. This study considers the development of optimization models for MWD‐based grade transition. An MWD reconstruction method using orthogonal collocation in two dimensions is developed to capture the dynamic feature of MWD in time and the distributive feature in chain length. The simultaneous collocation approach is adopted to discretize the model. Two optimization formulations are proposed to describe minimizing the transition time as well as off‐spec production. Both formulations inherit the advantages of the simultaneous collocation approach. The numerical results show that the proposed methods can efficiently solve the grade transition problem with MWD specification, and obtain high performance control profiles to reduce the production cost. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1198–1210, 2019

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“…1, 4-7, and 22-29), population balance equations of all the other species (Eqs. [10][11][12][13][14][15][16][17][18][19], and dynamic MWD calculation (Eqs. [30][31][32].…”

Section: Single-stage Formulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic optimization for grade transition processes using orthogonal collocation on molecular weight distribution

Chen

Eason

et al. 2019

AIChE Journal

Self Cite

View full text Add to dashboard Cite

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“…Nevertheless, there are few CFD studies that have taken MWD into consideration. For instance, Zhang et al 23 simulated the spatial MWD in a nonideal LDPE reactor and process optimization at a given target MWD curve to achieve the optimal operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Industrial Styrene Polymerization in Nonideal Tower Reactors

Wang

2022

Ind. Eng. Chem. Res.

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An integrated model combining computational fluid dynamics (CFD) with polymerization kinetics was developed to investigate the industrial styrene thermal polymerization process. The comprehensive kinetic model was coupled with the CFD model by user-defined function (UDF) codes based on the method of moments. Meanwhile, a simulation based on the ideal reactor model was conducted. The results predicted by CFD, including the monomer conversion, molecular weight, and molecular weight distribution described by Flory’s distribution, compared satisfactorily with the plant data and exhibited higher accuracy than those of the ideal reactor model. A higher reaction temperature and a lower volume flow rate result in a higher monomer conversion and a wider molecular weight distribution. The increase of rotational speed of helical ribbon impellers improves the mixing efficiency and uniformity of species concentration in the stirred sections. The CFD model could provide valuable guidance for the optimization of operation conditions and the design of nonideal reactors.

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“…Their combination requires careful consideration of computational issues involved. Zhang et al 23 developed the spatial MWD computation with a CFD model. In their work, they interfaced with Fluent to conduct CFD simulations and optimized the operations using the Nelder Mead simplex method.…”

Section: Introductionmentioning

confidence: 99%

Operational Optimization of Polymerization Reactors with Computational Fluid Dynamics and Embedded Molecular Weight Distribution Using the Iterative Surrogate Model Method

Kong

Eason

Chen

et al. 2020

Ind. Eng. Chem. Res.

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The calculation of molecular weight distribution (MWD) in conjunction with a computational fluid dynamics (CFD) reactor model is computationally expensive as both the CFD and the MWD require large-scale computations. Operational optimization of polymerization reactors using high-fidelity models like CFD and MWD becomes even more challenging. In this work, a novel method of MWD simulation with a CFD model is first proposed. To overcome the computational expense of the CFD simulations during optimization, an iterative surrogate model method is proposed. Instead of building an accurate and global model with a large set of simulation data, this method uses a limited set of simulation data and updates the optimization iteratively. Optimality of the proposed method is analyzed. A low-density polyethylene production process in an autoclave reactor is used for demonstration. The results show that the proposed iterative method can greatly reduce the computation time and effectively obtain the optimal result.

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Simulation and optimization of polymer molecular weight distribution with nonideal reactors

Cited by 11 publications

References 28 publications

Dynamic optimization for grade transition processes using orthogonal collocation on molecular weight distribution

Dynamic optimization for grade transition processes using orthogonal collocation on molecular weight distribution

Numerical Analysis of Industrial Styrene Polymerization in Nonideal Tower Reactors

Operational Optimization of Polymerization Reactors with Computational Fluid Dynamics and Embedded Molecular Weight Distribution Using the Iterative Surrogate Model Method

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