Scale-Up of Oscillatory Helical Baffled Reactors Based on Residence Time Distribution

2017 ◽  
Vol 40 (5) ◽  
pp. 907-914 ◽  
Author(s):  
Safaa M. R. Ahmed ◽  
Anh N. Phan ◽  
Adam P. Harvey
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Scale Up

Modelling of Fluidized Bed Reactors

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Joachim Werther ◽  
Ernst-Ulrich Hartge
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Fluidized Bed ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Scale Up ◽  
Fluidized Bed Reactor ◽  
Fluidized Bed Reactors ◽  
Model Calculations

The fluidized bed reactor has a lot of advantages: excellent gas-solid contacting, no hot spots even with highly exothermal reactions, good gas-to-particle and bed-to-wall heat transfer and the ease of solids handling which is particularly important if the catalyst is quickly ageing. However, the list of disadvantages is as long: broad residence time distribution of the gas due to dispersion and gas-bypass in the form of bubbles, broad residence time distribution of solids due to intense mixing, erosion of bed internals and the attrition of the catalyst particles. A particular disadvantage of the fluidized bed reactor is its difficult scale-up. The historical experience with the FCC process is that in the early 40's of the last century this process was successfully scaled up from a 5 cm dia. pilot-scale unit to a 4.5 m dia. bed in the production unit. On the other hand, around 1950 the scale up of the Fischer-Tropsch synthesis in the fluidized bed failed completely. Modern process design should be able to avoid such disasters by making use of modeling and simulation tools. However, a modeling tool which is really helpful in planning and designing of an industrial fluidized bed reactor has to fulfill a lot of requirements. It should be able to describe the influence of the several changes which are typical for the scale-up process, for example enlargement of bed diameter, bed height and fluidizing velocity, changes of gas distributor design, introduction of in-bed heat exchanger tubes and baffles. In the present work a modelling approach is presented which is able to handle the most important aspects of industrial fluidized bed reactors. A particular focus is to describe the relationship between catalyst attrition, solids recovery in the reactor system and chemical performance of the fluidized bed reactor. The competing influences of attrition of the catalyst particles and efficiency of the solids recovery lead to the establishment of a catalyst particle size distribution (PSD) in the bed inventory which in turn influences via the hydrodynamic characteristics of the fluidized bed the performance of the chemical reactor. The usefulness of this approach is illustrated with model calculations for a fictituous first order reaction where the fluidized bed is equipped with different solids recovery systems including one single stage cyclone, several cyclones in parallel, two- and three-stage cyclone systems, respectively. Model calculations illustrate the significance of a high efficiency of the solids recovery in order to keep the fines in the system which is decisive for a high performance of the reactor. The calculations reveal that it may take months until a quasi steady state of the bed particle size distribution is obtained.

scholarly journals Impact of Particle and Equipment Properties on Residence Time Distribution of Pharmaceutical Excipients in Rotary Tablet Presses

Pharmaceutics ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 283
Author(s):  
Daniel Puckhaber ◽  
Sebastian Eichler ◽  
Arno Kwade ◽  
Jan Henrik Finke
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Process Development ◽  
Continuous Production ◽  
Scale Up ◽  
Powder Flow ◽  
Production Scale ◽  
Influence Of Process Parameters ◽  
Custom Made

Paddle feeders are devices commonly used in rotary tablet presses to facilitate constant and efficient die filling. Adversely, the shear stress applied by the rotating paddles is known to affect the bulk properties of the processed powder dependent on the residence time. This study focuses on the residence time distribution (RTD) of two commonly applied excipients (microcrystalline cellulose, MCC; dicalcium phosphate, DCP), which exhibit different flow properties inside rotary tablet presses. To realistically depict the powder flow inside rotary tablet presses, custom-made tracer powder was developed. The applied method was proven to be appropriate as the tracer and bulk powder showed comparable properties. The RTDs of both materials were examined in two differently scaled rotary tablet presses and the influence of process parameters was determined. To analyze RTDs independent of the mass flow, the normalized variance was used to quantify intermixing. Substantial differences between both materials and tablet presses were found. Broader RTDs were measured for the poorer flowing MCC as well as for the production scale press. The obtained results can be used to improve the general understanding of powder flow inside rotary tablet presses and amplify scale-up and continuous production process development.

Design and Scale-up of Modular Capillary Helical Flow Inverter Reactors With Narrow Residence Time Distribution

2019 ◽  
Author(s):  
Norbert Kockmann ◽  
Waldemar Krieger ◽  
Mira Schmalenberg
Keyword(s):  
Residence Time ◽  
Pressure Loss ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Modular Design ◽  
Scale Up ◽  
Reactor Performance ◽  
Lab On Chip ◽  
Modular Concept ◽  
On Chip

Abstract Lab-on-chip processes often require long dwelling times leading to coiled capillary reactors with laminar flow. These tubular reactors are designed for a reaction time, unfortunately with a wide residence time distribution. This contribution presents a modular concept based on coiled flow inverters (CFI), which achieve high radial mixing with narrow residence time distribution at low Reynolds numbers [1]. The modular design enables quick adaptation to changing residence times and flow rates with low pressure loss. The tube diameters range from capillaries with a few 100 μm to several millimeters for high throughput and long residence time. With the aid of a design space diagram, the required pipe diameters and lengths can be quickly determined based on standardized coil diameters [2]. The modular concept enables various arrangements for different residence time and flow rate requirements with minimum pressure loss. In the laboratory, for example, a chemical process in the throughput range of a few grams per hour can be developed and processed in the simple device. The results can be scaled via the platform concept to higher production rates with constant residence time characteristics. The scale-up concept can easily be displayed and designed graphically in the reactor performance diagram.

scholarly journals A novel technique for residence time distribution (RTD) measurements in solids unit operations

2021 ◽  
Vol 32 (2) ◽  
pp. 611-618
Author(s):  
Atena Dehghani Kiadehi ◽  
Mikel Leturia ◽  
Franco Otaola ◽  
Aissa Ould-Dris ◽  
Khashayar Saleh
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Novel Technique ◽  
Unit Operations
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