Design Correlations for Autothermal Reactors with Internal Countercurrent Heat Exchange

Ampaya, J.P.; Rinker, Robert G.

doi:10.1021/i260061a010

Cited by 7 publications

(5 citation statements)

References 1 publication

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“…They presented a theoretical analysis with experimental verification for cocurrent reactor/heat exchanger, which leads to a scheme that gives isothermal reactor conditions, decreased parametric sensitivity and improved stability, although this can be achieved only within narrow windows of operation. Somewhat less related is the work of Ampaya and Rinker (1977) among many others, who studied the effects of operating and design parameters for autothermal reactors with internal countercurrent heat exchange.…”

Section: Scopementioning

confidence: 99%

A design approach based on phase plane analysis: Countercurrent reactor/heat exchanger with parametric sensitivity

Akella

Lee

1983

AIChE Journal

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A design approach based on a phase diagram of inlet temperatures is proposed for the countercurrent reactor/heat exchanger for highly exothermic reactions with inherent parametric sensitivities. The phase diagram shows the region of safe operation on a plane of feed and coolant inlet temperatures, free from runaway conditions. The boundaries surrounding the safe operation region are defined by design parameters. Simple procedures applicable to arbitrary expressions of global rate are developed for the phase diagram. The multi-pronged design problem of selecting the design parameters and operating conditions for the maximum possible conversion within the constraints due to the parametric sensitivities is condensed into and represented by a phase diagram and an analysis on the phase plane. A design alternative which eliminates the necessity of the preheater for highly exothermic reactions is discussed and the advantages are quantitatively illustrated to assert that this design should be seriously considered as a viable alternative. SCOPEChemical reactors, especially those in which highly exothermic reactions occur, are operated very carefully due to the existence of parametric sensitivities with respect to fluctuations in most of the operating variables. These reactors can be operated safely only within a narrow range of operating variables such as feed and coolant inlet temperatures due to the possibility of runaway as a result of this parametric sensitivity. For these highly exothermic reactions with the sensitivity problem, therefore, a liquid coolant instead of a gaseous coolant is used so that a better control of reactor temperature can lead to a wider range of safe operating conditions. Many studies have been reported in literature to predict the parametric sensitivity and establish runaway criteria for tubular reactors. Bilous and Amundson (1956) studied the parametric sensitivity with respect to feed concentrations and temperatures for quasi-isothermal tubular reactors and developed a method for prediction of such behavior based on transient response. Chambre (1956) and Barkelew (1959) used phase plane analysis for the general solution of the nonlinear equations for tubular reactors and established the boundary between stable and unstable regions. Oroskar and Stern (1979) extended the work of the above two investigators to obtain exact conditions leading to either stable or runaway reactor operation. Van Welsenaere and Froment (1970) took a different approach which requires comparatively less amount of computation to obtain conditions leading to runaway operation. All the above studies were confined to mostly first order kinetics and to some extent to nth order kinetics. The temperature behavior in a countercurrent reactor/ heat exchanger was investigated by Grens and McKean (1963).Among those who studied new schemes of design for improved stability of reactors were Degnan and Wei (1979,1980). They presented a theoretical analysis with experimental verification for cocurrent reactor/heat exchanger, which l...

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Section: Scopementioning

confidence: 99%

A design approach based on phase plane analysis: Countercurrent reactor/heat exchanger with parametric sensitivity

Akella

Lee

1983

AIChE Journal

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Section: Process Modelmentioning

confidence: 99%

“…A reactor diameter dR = 2 cm, a feed rate = 13 cm' s-', a feed temperature To = 500 K and a total pressure P = 2 MPa were used. The applied heat transfer coefficient k,, = 0.015 J cm-' s-' K-' was calculated from the given experimental and material data (Emig et al, 1972;Ampaya and Rinker, 1977). A reaction rate model of the catalytic ammonia synthesisgenerally gives the time dependent increase of the ammonia partial pressure dpNH,/dt as a function of the partial pressure of all components piThis broadly applied empirical model of a reversible reaction was proposed by Temkin and Pyshev ( 1940) and consists of the terms for the forward and the backward reaction, as usual, with the respective rate constants k , and k2, and a dimensionless fitting parameter rn.…”

mentioning

confidence: 99%

Simulation of temperature peak attenuation by catalyst dilution in a tubular packed‐bed reactor

1983

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Temperature peak attenuation is an important problem for safe process control. Simulations of the axial temperature and product progression in stationary ammonia synthesis with different axial catalyst dilutions have been carried out. It is demonstrated that the requirement of temperature peak attenuation together with a maximum product yield can be met by an optimal catalyst dilution profile at the entrance of the bed.

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“…Mukosei et al (1968) also investigated the steady-state regimes of tubular reactors with internal, external and combined heat exchange. Inoue and Komiya (1968) and Ampaya and Rinker (1977a) investigated the stability of a tubular reactor with internal heat exchange with regard to the critical feed temperature for several different operating and design parameters. Inoue and Komiya (1968) developed conditions for the stable operation of the autothermal reactor for both reversible and irreversible reactions.…”

Section: Introductionmentioning

confidence: 99%

“…The results of this method are only qualitative and are useful in predicting the qualitative effect of varying parameters on the stability of the reactor. Ampaya and Rinker (1977a) adopted a similar approach and related the critical feed temperature (at extinction) to various operating and design parameters for the case of the water-gas shift reaction. Later, conditions for reactor runaway were also developed by Inoue (1978).…”

Section: Introductionmentioning

confidence: 99%

Multiplicity features of adiabatic autothermal reactors

Lovo

Balakotaiah

1992

AIChE Journal

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Singularity theory, large activation energy asymptotics, and numerical methods are used to present a comprehensive study of the steady-state multiplicity features of three classical adiabatic autothermal reactor models: tubular reactor with internal heat exchange, tubular reactor with external heat exchange, and the CSTR with external heat exchange. Specifically, we derive the exact uniqueness-multiplicity boundary, determine typical cross-sections of the bifurcation set, and classify the different types of bifurcation diagrams of conversion us. residence time. Asymptotic (limiting) models are used to determine analytical expressions for the uniqueness boundary and the ignition and extinction points. The analytical results are used to present simple, explicit and accurate exp*essions defining the boundary of the region of autothermal operation in the physical parameter space.

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Design Correlations for Autothermal Reactors with Internal Countercurrent Heat Exchange

Cited by 7 publications

References 1 publication

A design approach based on phase plane analysis: Countercurrent reactor/heat exchanger with parametric sensitivity

A design approach based on phase plane analysis: Countercurrent reactor/heat exchanger with parametric sensitivity

Simulation of temperature peak attenuation by catalyst dilution in a tubular packed‐bed reactor

Multiplicity features of adiabatic autothermal reactors

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