scholarly journals Oscillatory flow chemical reactors

2014 ◽  
Vol 68 (3) ◽  
pp. 363-379 ◽  
Author(s):  
Danijela Slavnic ◽  
Branko Bugarski ◽  
Nikola Nikacevic
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Flow Pattern ◽  
Heat And Mass Transfer ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Oscillatory Flow ◽  
Market Competition ◽  
Plug Flow

Global market competition, increase in energy and other production costs, demands for high quality products and reduction of waste are forcing pharmaceutical, fine chemicals and biochemical industries, to search for radical solutions. One of the most effective ways to improve the overall production (cost reduction and better control of reactions) is a transition from batch to continuous processes. However, the reactions of interests for the mentioned industry sectors are often slow, thus continuous tubular reactors would be impractically long for flow regimes which provide sufficient heat and mass transfer and narrow residence time distribution. The oscillatory flow reactors (OFR) are newer type of tube reactors which can offer solution by providing continuous operation with approximately plug flow pattern, low shear stress rates and enhanced mass and heat transfer. These benefits are the result of very good mixing in OFR achieved by vortex generation. OFR consists of cylindrical tube containing equally spaced orifice baffles. Fluid oscillations are superimposed on a net (laminar) flow. Eddies are generated when oscillating fluid collides with baffles and passes through orifices. Generation and propagation of vortices create uniform mixing in each reactor cavity (between baffles), providing an overall flow pattern which is close to plug flow. Oscillations can be created by direct action of a piston or a diaphragm on fluid (or alternatively on baffles). This article provides an overview of oscillatory flow reactor technology, its operating principles and basic design and scale - up characteristics. Further, the article reviews the key research findings in heat and mass transfer, shear stress, residence time distribution in OFR, presenting their advantages over the conventional reactors. Finally, relevant process intensification examples from pharmaceutical, polymer and biofuels industries are presented.

scholarly journals Modeling Residence Time Distribution (RTD) Behavior in a Packed-Bed Electrochemical Reactor (PBER)

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Sananth H. Menon ◽  
G. Madhu ◽  
Jojo Mathew
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Flow Model ◽  
Plug Flow ◽  
Flow Characteristics ◽  
Theoretical Models ◽  
Packed Bed ◽  
Electrochemical Reactor ◽  
Tracer Studies

This paper focuses on understanding the electrolyte flow characteristics in a typical packed-bed electrochemical reactor using Residence Time Distribution (RTD) studies. RTD behavior was critically analyzed using tracer studies at various flow rates, initially under nonelectrolyzing conditions. Validation of these results using available theoretical models was carried out. Significant disparity in RTD curves under electrolyzing conditions was examined and details are recorded. Finally, a suitable mathematical model (Modified Dispersed Plug Flow Model (MDPFM)) was developed for validating these results under electrolyzing conditions.

scholarly journals Explicit Residence Time Distribution of a Generalised Cascade of Continuous Stirred Tank Reactors for a Description of Short Recirculation Time (Bypassing)

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 615 ◽  
Author(s):  
Peter Toson ◽  
Pankaj Doshi ◽  
Dalibor Jajcevic
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Flow Reactor ◽  
Plug Flow ◽  
Stirred Tank ◽  
Stirred Tank Reactors ◽  
Delayed Impulse ◽  
In Series ◽  
Back Mixing

The tanks-in-series model (TIS) is a popular model to describe the residence time distribution (RTD) of non-ideal continuously stirred tank reactors (CSTRs) with limited back-mixing. In this work, the TIS model was generalised to a cascade of n CSTRs with non-integer non-negative n. The resulting model describes non-ideal back-mixing with n > 1. However, the most interesting feature of the n-CSTR model is the ability to describe short recirculation times (bypassing) with n < 1 without the need of complex reactor networks. The n-CSTR model is the only model that connects the three fundamental RTDs occurring in reactor modelling by variation of a single shape parameter n: The unit impulse at n→0, the exponential RTD of an ideal CSTR at n = 1, and the delayed impulse of an ideal plug flow reactor at n→∞. The n-CSTR model can be used as a stand-alone model or as part of a reactor network. The bypassing material fraction for the regime n < 1 was analysed. Finally, a Fourier analysis of the n-CSTR was performed to predict the ability of a unit operation to filter out upstream fluctuations and to model the response to upstream set point changes.

Quantitative Analysis of Residence Time Distribution in Kenics Static Mixer

2012 ◽  
Vol 499 ◽  
pp. 198-202 ◽  
Author(s):  
Dan Jin ◽  
Hai Ling Fu ◽  
Jian Hua Wu ◽  
Dan Sun
Keyword(s):  
Quantitative Analysis ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Plug Flow ◽  
Axial Direction ◽  
Static Mixer ◽  
Mixing Quality ◽  
Experimental Approaches ◽  
The Mean

The residence time distribution in Kenics static mixer is investigated using experimental approaches. Experimentally, RTD measure in SK with pulse tracer technology was used to characterize flow and mixing quality. The effect of velocity on the RTD was investigated for all sections. The results show that the flow in SK mixer tends to the plug flow along the axial direction when the velocity increases. The quantization analysis, the effect of factors on the mean residence time, is done by using the power function considering the numbers of mixer element, diameter, element aspect radio, and velocity. The validity of this function is testified by other experiments.

The Mixing Characteristics and Residence Time Distribution of Cut Tobacco Particles in Drum Mixer

2011 ◽  
Vol 396-398 ◽  
pp. 297-301
Author(s):  
Wen Kui Zhu ◽  
Dong Liu ◽  
Jin Song Du
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Plug Flow ◽  
Processing System ◽  
Rotating Speed ◽  
Drum Mixer ◽  
Method Effects ◽  
Residence Time Distributions ◽  
Cut Tobacco

Residence time distributions were determined for the continuous processing of cut tobacco in the rotary drum by introducing expanded cut tobacco tracers to the inlet of the processing system using the negative step change method. Effects of rotating speed of the rotary cylinder and solids flow rate on the mixing homogenization and residence time distribution (RTD) of experiment materials was investigated. PER-CSTR series model and multistage CSTR model were used to fit the experimental results. The result shows mixing homogenization increased significantly with the increasing feeding rate of cut tobacco and decreasing drum rotating speed. PER-CSTR series model is more suitable to describe the RTD characteristics of flow materials in drum. The axis movement of cut tobacco along the drum is approximate to the plug-flow.

scholarly journals Derivation of a Multiparameter Gamma Model for Analyzing the Residence-Time Distribution Function for Nonideal Flow Systems as an Alternative to the Advection-Dispersion Equation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Irucka Embry ◽  
Victor Roland ◽  
Oluropo Agbaje ◽  
Valetta Watson ◽  
Marquan Martin ◽  
...  
Keyword(s):  
Dispersion Equation ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Flow Reactor ◽  
Plug Flow ◽  
Absolute Deviation ◽  
Suitable Alternative ◽  
Advection Dispersion ◽  
Flow Systems

A new residence-time distribution (RTD) function has been developed and applied to quantitative dye studies as an alternative to the traditional advection-dispersion equation (AdDE). The new method is based on a jointly combined four-parameter gamma probability density function (PDF). The gamma residence-time distribution (RTD) function and its first and second moments are derived from the individual two-parameter gamma distributions of randomly distributed variables, tracer travel distance, and linear velocity, which are based on their relationship with time. The gamma RTD function was used on a steady-state, nonideal system modeled as a plug-flow reactor (PFR) in the laboratory to validate the effectiveness of the model. The normalized forms of the gamma RTD and the advection-dispersion equation RTD were compared with the normalized tracer RTD. The normalized gamma RTD had a lower mean-absolute deviation (MAD) (0.16) than the normalized form of the advection-dispersion equation (0.26) when compared to the normalized tracer RTD. The gamma RTD function is tied back to the actual physical site due to its randomly distributed variables. The results validate using the gamma RTD as a suitable alternative to the advection-dispersion equation for quantitative tracer studies of non-ideal flow systems.

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