Simulation of three‐stage nylon 6 reactors with intermediate mass transfer at finite rates

Gupta, Santosh K.; Kumar, Anil; Agrawal, K.K.

doi:10.1002/app.1982.070270831

Cited by 25 publications

(8 citation statements)

References 26 publications

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“…According to the above assumptions, and referring to the model for the SSP of Xie and for polymerization in the liquid phase of Gupta et al, the final mass balance equations for the SSP of Nylon 6 have been obtained with the method of moments.…”

Section: Methodsmentioning

confidence: 99%

“…The researches on Nylon 6 SSP reaction have been reported in many literature. Gupta developed a theoretical molecular model for SSP of Nylon 6 and discussed the effect of segmental diffusion on reversible step growth polymerization and the diffusional effects on the rate constants . Based on Gupta's work, Li et al inserted end‐to‐end distance distribution into the SSP model of Nylon 6 and investigated the effects of the operation conditions on SSP .…”

Section: Introductionmentioning

confidence: 99%

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Modeling of the Dehydration Process Coupled with Solid‐State Polymerization in Nylon 6 Drying Column

Sun

Qin

et al. 2015

Macro Reaction Engineering

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Drying of wet Nylon 6 chips is a significant process for dehydration after granulation. During the process, the flow pattern of gas-solid phases is countercurrent flow, while the mass transfer and solid-state polymerization (SSP) are deeply coupled with each other. In this paper, the mass transfer behavior for dehydration at drying conditions has been investigated by single pellet experiments using Thermogravimetric Analyzer (TGA). A diffusion model for dehydration has been developed and the diffusion coefficient has been estimated by TGA test data. Besides, the SSP reaction characteristic has been independently studied in a polymerization tube at different temperatures. The reaction kinetics parameters, including the rate constants and equilibrium constants for both forward and reverse reactions, have been obtained by fitting the experimental data. Based on that, an integrated model combining the mass/heat transfer and polymerization reaction has been presented for the industrial continuous Nylon 6 drying process. The influences of drying conditions including the initial number average degree of polymerization, inlet nitrogen temperature, and flow rate, on distribution profiles of temperatures, water contents, and degree of polymerization of chips along the column height have been simulated. The integrated model can be used to predict the industrial drying process.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling of the Dehydration Process Coupled with Solid‐State Polymerization in Nylon 6 Drying Column

Sun

Qin

et al. 2015

Macro Reaction Engineering

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“…Kinetics of hydrolytic polymerization of ε‐caprolactam has been extensively studied1–10 in batch reactors. These kinetic models were also used to investigate the polymerization process in continuous tube reactors 5, 11–19. Recently, we had reported modeling of an industrial VK (Vereinfacht Konitnuierliches) tube reactor, using monocarboxylic acid (monoacid) stabilizer, where the effect of the complex internal structure (heat exchanger, internal gratings) of the reactor was considered 20.…”

Section: Introductionmentioning

confidence: 99%

Effect of diacid stabilizers on kinetics of hydrolytic polymerization of ϵ‐caprolactam in industrial reactors

Agrawal¹,

Gupta²,

Devika³

et al. 2007

J of Applied Polymer Sci

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The rate constants in hydrolytic polymerization of e-caprolactam are dependent on the concentration of carboxylic acid groups in the reaction medium. Therefore, the use of diacid stabilizers for regulating molecular weight are likely to have favorable effect on the kinetics of polymerization compared to monoacid stabilizers, which are traditionally used in such polymerizations. To understand the kinetics of polymerization in the presence of diacid stabilizer compared to monoacid stabilizer, mathematical kinetic models were developed using the end group approach. These models were used to quantify the effect of both stabilizers on nylon-6 synthesis in a closed isothermal batch reactor at different temperatures in the range of 245-2658C. The kinetic model for the diacid-stabilized system was then extended to an industrial VK tube reactor using the process model developed earlier for the monoacid stabilized system. Both the mathematical modeling and experimental results showed that the presence of diacid stabilizer could significantly enhance the overall kinetics of the reaction compared to the monoacid stabilized system and in turn, resulted in reduction of the polymerization time by about 20-25%. The study suggests that diacid stabilizers may be used preferably over monoacid stabilizers in synthesis of nylon-6 to reduce the cost of polymerization.

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“…[12][13][14][15] The importance of water removal from the reaction mass in a tubular reactor was realized by many authors. 5,11,[16][17][18][19] As a result, the tubular reactors were modeled by assuming two principal zones: 11,16,17 a top vaporizing zone simulated as a single or a series of continuous stirred tank reactor(s) (CSTR) and a bottom nonvaporizing plug-flow zone. The CSTR models were used to account for the water removal and back mixing caused by the escaping vapors in a VK tube.…”

Section: Introductionmentioning

confidence: 99%

“…Similar models have also been extended for simple tubular reactors without consideration of the effects of internal gratings and heat exchangers. , The radial variations in the temperature and the concentrations of species in a simple tube reactor have been studied under isothermal, adiabatic, and nonadiabatic conditions. − The importance of water removal from the reaction mass in a tubular reactor was realized by many authors. ,,− As a result, the tubular reactors were modeled by assuming two principal zones: 11,16,17 a top vaporizing zone simulated as a single or a series of continuous stirred tank reactor(s) (CSTR) and a bottom nonvaporizing plug-flow zone. The CSTR models were used to account for the water removal and back mixing caused by the escaping vapors in a VK tube.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Hydrolytic Polymerization of Nylon-6 in Industrial Reactors: Part I. Mono-Acid-Stabilized Systems in VK Tube Reactors

Agrawal¹,

Devika²,

Manabe³

2001

Ind. Eng. Chem. Res.

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Nylon-6 polymerization in a VK tube (vertical column) reactor is largely not understood because of the complex internal structure of the reactor and the unavailability of essential industrial data on polymerization. In the present study, the hydrolytic polymerization of nylon-6 has been simulated in an industrial VK tube reactor for concentrations of various species. The model, which assumed a flat velocity profile in the radial direction, predicted the industrial results with high accuracy. The internal design of the reactor appears to be responsible for getting close to plug-flow conditions inside the VK tube. An empirical relation based on temperature and pressure was used to determine the water profile along the vertical axis of the reactor. Because the pressure increased along the axis of the reactor and the temperature first increased and then decreased, the model predicted a lowest water content (LWC) point at near the highest temperature point. The concentration of water at the LWC point was found to be critical in determining the properties of the end product. The model suggested three main zones in a VK tube reactor: a very small top turbulent zone, where most of the water was lost, followed by a large middle zone, which was a vaporizing plug-flow tubular zone, and a bottom zone, which was a nonvaporizing plug-flow tubular zone. The vaporizing zone ended and the nonvaporizing zone began where the LWC point was achieved. The small turbulent zone at the top did not appear to affect the end polymer properties of polymerization. This model was found to be useful in carrying out process optimization and suggesting improvements in VK tube designs for higher productivity.

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Simulation of three‐stage nylon 6 reactors with intermediate mass transfer at finite rates

Cited by 25 publications

References 26 publications

Modeling of the Dehydration Process Coupled with Solid‐State Polymerization in Nylon 6 Drying Column

Modeling of the Dehydration Process Coupled with Solid‐State Polymerization in Nylon 6 Drying Column

Effect of diacid stabilizers on kinetics of hydrolytic polymerization of ϵ‐caprolactam in industrial reactors

Simulation of Hydrolytic Polymerization of Nylon-6 in Industrial Reactors: Part I. Mono-Acid-Stabilized Systems in VK Tube Reactors

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