scholarly journals Novel Evaluation Method to Determine the Local Mixing Time Distribution in Stirred Tank Reactors

2021 ◽  
pp. 100098
Author(s):  
J. Fitschen ◽  
S. Hofmann ◽  
J. Wutz ◽  
A.v. Kameke ◽  
M. Hoffmann ◽  
...  
Keyword(s):  
Time Distribution ◽  
Evaluation Method ◽  
Mixing Time ◽  
Stirred Tank ◽  
Stirred Tank Reactors

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.

Hydrodynamic Investigation in an Annular Reactor with Mixing Time and Residence Time Distribution: Flow Rates Estimation with the Gauss-Newton Gradient Technique

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Skandar Rjeb ◽  
Ahmed Hannachi ◽  
Ratal Abdelhamid
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Search Algorithm ◽  
Mixing Time ◽  
Chemical Reactor ◽  
Computer Code ◽  
Flow Rates ◽  
Stirred Tank Reactors ◽  
Gradient Technique

In this work, flow patterns within an annular chemical reactor were characterized. The reactor was modeled by a cascade of communicating Continuous Stirred Tank Reactors (CSTRs) exchanging flow rates of variable intensities. Mixing time and Residence Time Distribution measurements were used as basis for flow modeling. A Matlab computer code has been developed to predict the exchanged flow rates through the minimization of an objective function. This paper describes the parameter estimation technique which is based on the Gauss-Newton method with a linear search algorithm. Only two opposite flow rates between reactor compartments were assumed and were identified for various mixing conditions. For the studied cases, the predicted responses were close to the experimental measurements.

Experimental Investigation of the Use of Synthetic Jets for Mixing in Vessels

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Mushtak Al-Atabi
Keyword(s):  
Mixing Time ◽  
Synthetic Jets ◽  
Stirred Tank ◽  
Fluid Viscosity ◽  
Stirred Tank Reactors ◽  
Mixing Performance ◽  
Shear Rates ◽  
Local Shear ◽  
Continuously Stirred Tank Reactor ◽  
Visualization Techniques

Mixing is an important process in various industries. Different designs have been suggested in order to reduce the local shear rates in mechanically stirred mixing vessels, also known as continuously stirred tank reactors, in order to account for the mixing requirements for sensitive materials such as biological materials and biofluids where the high shear rate may damage the sensitive materials. This paper reports on the development of a continuously stirred tank reactor that can be used to achieve a variety of mixing assignments. This mixing is achieved using synthetic jets. The mixing performance was assessed using flow visualization techniques. The effects of fluid viscosity on mixing time were investigated. The results are very encouraging and are suggestive that the use of synthetic jets in mixing is a viable alternative to the conventional methods of mixing in vessels.

CFD Analysis and Design Optimization in a Curved Blade Impeller

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Nazila Sutudehnezhad ◽  
Ramin Zadghaffari
Keyword(s):  
Flow Field ◽  
Mixing Time ◽  
Computational Method ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Stirred Tank Reactors ◽  
Analysis And Design ◽  
Curved Blade ◽  
Reported Data

Abstract Mixing efficiency in stirred tank reactors is an important challenge in the design of many industrial processes. The effect of blade shape on mixing efficiency has been studied in the present work. The computational method has been used to investigate the flow field, power consumption, pumping capacity, hydraulic efficiency, and mixing time in a fully baffled tank stirred by a Rushton turbine and different curved blade impellers. Flow in a stirred tank reactor involves interactions between flow around rotating blades and stationary baffles. The flow field was developed using the sliding mesh (SM) approach in computational fluid dynamics (CFD). The realizable k-ε was used to model the turbulence. A reasonable agreement between the experimental reported data and simulation results indicated the validity of CFD model. It has been revealed that increasing the blade curvature, at approximately the same mixing time would enhance the mixing efficiency up to 61.3 % in comparison with the Rushton turbine. This mixing efficiency would favor the employment of curved blade impellers due to the cost-benefits of stirred tank operations.

Removal of lead by sulfate-reducing bacteria in anaerobic continuous stirred tank reactors

2016 ◽  
Vol 14 (3) ◽  
pp. 557-561
Author(s):  
Nguyễn Thị Yên ◽  
Kiều Thị Quỳnh Hoa
Keyword(s):  
Sulfate Reducing Bacteria ◽  
Stirred Tank ◽  
Synthetic Wastewater ◽  
Terminal Electron Acceptor ◽  
Stirred Tank Reactors ◽  
Sulfate Reducing ◽  
Sulfide Production ◽  
Continuous Stirred Tank ◽  
Continuous Stirred Tank Reactors ◽  
Reducing Bacteria

Lead contaminated wastewater negatively impacts to living organisms as well as humans. In recent years, a highly promising biological process using the anaerobic production of sulfide ions by sulfate-reducing bacteria has presented itself as an alternative option for the removal of lead. This process is based on microbial utilization of electron donors, such as organic compounds (carbon sources), and sulfate as the terminal electron acceptor for sulfide production. The biogenic hydrogen sulfide reacts with dissolved heavy metals to form insoluble metal sulfide precipitates Removal of lead by an enriched consortium of sulfate-reducing bacteria (DM10) was evaluated sulfate reduction, sulfide production and lead precipitation. Four parallel anaerobic continuous stirred tank reactors (CSTR, V = 2L) (referred as R1 - R4) were fed with synthetic wastewater containing Pb2+ in the concentrations of 0, 100, 150 and 200 mg L-1 of lead and operated with a hydraulic retention time of 5 days for 40 days. The loading rates of each metal in R1- R4 were 0, 20, 30 and 40 mg L-1 d-1, respectively. The results showed that there was no inhibition of SRB growth and that lead removal efficiencies of 99-100% for Pb2+ were achieved in R2 (100 mg L-1) and R3 (150 mg L-1) throughout the experiment. For the highest lead concentration of  200 mg L-1, a decrease in efficiency of removal (from 100 to 96%) was observed at the end of the experiment. The obtained result of this study might help for a better control operation and performance improvements of reactors.

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