New model of micromixing in chemical reactors. 1. General development and application to a tubular reactor

Pohorecki, Ryszard; Bałdyga, J.

doi:10.1021/i100012a007

Cited by 38 publications

(12 citation statements)

References 14 publications

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“…In this report we wish to interpret the plume length measurements of Rice et al (1964) and Pohorecki and Baldyga (1983) from a fundamental viewpoint, starting with the probability density function (PDF) method (Toor, 1962) which, for the conditions of the experiments, will be seen to reduce to Danckwerts' (1957) result. We do not include the measurements of Kristmanson and Danckwerts (1961) because of uncertainties raised by their use of a two-color indicator and a weak base.…”

mentioning

confidence: 99%

Chemical indicators as mixing probes. A possible way to measure micromixing simply

Li¹,

Toor²

1986

Ind. Eng. Chem. Fund.

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Earlier workers have introduced a base into the center of a turbulent acid stream with phenolphthalein in both streams and measured the length of the visible plume as a function of reagent equivalence ratio. The probability density function (PDF) method, applied to their data taking into account the reversibility of the instantaneous ionization reaction, shows that for the conditions of the experiments the visible plume may be considered to be made up of interspersed eddies of essentially fully colored base and colorless acid. The time-average fraction of the colored indicator is related to the scalar PDF, and the scalar root-mean-square concentration fluctuations have been determined by assuming that the time-average concentration that is just visible to the eye is the same as the usual concentration which is just visible and that the PDF is the beta distribution. These values are not unreasonable and point toward the possibility of obtaining micromixing data simply.

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mentioning

confidence: 99%

Chemical indicators as mixing probes. A possible way to measure micromixing simply

Li¹,

Toor²

1986

Ind. Eng. Chem. Fund.

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“…However, in this case different turbulence model seem to affect the predicted plume length, as shown in Figure 10. [24]. The model results reported by Hjertager et al [15] are also shown for comparison.…”

Section: Wallmentioning

confidence: 87%

“…Figure 9 Second tubular reactor plume length computed using various TKI models with 𝜅 − 𝜖 model vs. the experimental values in [24]. The model results reported by Hjertager et al [15] are also shown for comparison.…”

Section: Wallmentioning

confidence: 96%

“…The third set of experimental data investigated has been carried out in the steady-state isothermal tubular reactor sketched in Figure 8 [24]. An alkaline solution A (sodium hydroxide) has been injected from the capillary (concentric to the larger reactor tube), while an acid solution B (hydrochloric acid) has been fed to the circular corona between the capillary and the reactor wall, leading to a neutralization reaction [23]:…”

Section: Second Tubular Reactormentioning

confidence: 99%

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A CFD hybrid approach to simulate liquid-phase chemical reactors

Rizzotto

Florit

Rota

2019

Chemical Engineering Journal

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“…Lamellar mixing models provide an alternative approach to modeling the complex interactions between local motion, molecular diffusion, and chemical reaction in the mixing of miscible reactive fluids. Pohorecki and Baldyga (1983a, b) proposed using the spectral interpretation of mixing in an isotropic turbulent field in order to explain micromixing effects in homogeneous liquid phase chemical reactors. The authors in their further work ( 1 9 8 3~) used the same model to evaluate the influence of the intensity of mixing on the rate of precipitation in an agitated, perfectly macromixed vessel.…”

Section: Diflusion Modelsmentioning

confidence: 99%

Mixing in continuous crystallizers

Tavare

1986

AIChE Journal

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The review is concerned primarily with some aspects of mixing in continuous crystallizers and recognizes the central importance of the interplay between the mixing and crystallization (or precipitation) processes in the design and performance evaluation of industrial crystallizers. The paper adopts a unifying treatment from a chemical reaction engineering viewpoint in which the Lagrangian approach to mixing in crystallizer systems is emphasized. The concepts of macro-and micromixing applied to crystallization configurations have been introduced with due emphasis on the modeling efforts. The present state of knowledge in various related areas of continuous mixing is assessed to help direct future trends in research. N. S. Tavare Department of Chemical EngineeringUniversity of Manchester Institute of Science and TechnologyManchester, M60 lQD, England SCOPEIn recent years notable progress has been achieved in applying formalized unifying chemical reaction engineering principles to the analysis, simulation, and design of crystallizer configurations, but one significant gap in our understanding of crystallization processes is their interaction with mixing process. Using an analogy with the mixing description conventionally used in chemical reactors, this paper attempts to formalize the interplay between mixing and crystallization from the Lagrangian perspective. The mixing process is generally characterized by two distinct and independent elements, macro-and micromixing. The objectives of this review are to report the present state of the art and to direct further work on the characterization of mixing and its effects on the overall performance in conventional crystallizer configurations. Such a review may help in evaluating some of the research trends in this field. CONCLUSIONS AND SIGNIFICANCEThe present article attempts a comprehensive treatment of mixing in continuous crystallizers from the Lagrangian perspective and has resulted in a recognized and straightforward chemical reaction engineering approach to the analysis of crystallization processes. The first part of the review deals with macromixing aspects, which covers major developments in analysis of residence time and crystal size distributions (RTD and CSD) with particular reference to modeling work. Clearly, CSD modeling is and will remain a popular and central topic of crystallization research. Both RTD and CSD studies should become more detailed and widespread for their greater engineering utility in the design, performance evaluation, and control of industrial units.The second part of the review highlights the relatively new and important area of micromixing, i.e., mixing at the molecular scale. A small number of process simulation studies at extreme levels of micromixing have clearly demonstrated the enormous effects of the micromixing level on overall crystallizer performance. This may provide a comparatively sensitive and useful indicator of intermediate levels of micromixing. Characterization of real vessels of crystallization systems with complex no...

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New model of micromixing in chemical reactors. 1. General development and application to a tubular reactor

Cited by 38 publications

References 14 publications

Chemical indicators as mixing probes. A possible way to measure micromixing simply

Chemical indicators as mixing probes. A possible way to measure micromixing simply

A CFD hybrid approach to simulate liquid-phase chemical reactors

Mixing in continuous crystallizers

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