Dispersion of Floating Solid Particles in Aerated Stirred Tank Reactors:  Minimum Impeller Speeds for Off-Surface and Ultimately Homogeneous Solid Suspension and Solids Concentration Profiles

2006 ◽  
Vol 45 (2) ◽  
pp. 818-829 ◽  
Author(s):  
Atsushi Tagawa ◽  
Naoki Dohi ◽  
Yoshinori Kawase
Keyword(s):  
Solid Particles ◽  
Stirred Tank ◽  
Concentration Profiles ◽  
Stirred Tank Reactors ◽  
Solids Concentration ◽  
Solid Suspension

Power consumption and solid suspension performance of large-scale impellers in gas–liquid–solid three-phase stirred tank reactors

2004 ◽  
Vol 97 (2-3) ◽  
pp. 103-114 ◽  
Author(s):  
N. Dohi ◽  
T. Takahashi ◽  
K. Minekawa ◽  
Y. Kawase
Keyword(s):  
Power Consumption ◽  
Large Scale ◽  
Stirred Tank ◽  
Stirred Tank Reactors ◽  
Three Phase ◽  
Solid Suspension ◽  
Suspension Performance

CFD Simulation of Solid Suspension in a Stirred Reactor Driven by a Dual Punched Rigid-Flexible Impeller

2018 ◽  
Vol 16 (5) ◽  
Author(s):  
Deyin Gu ◽  
Zuohua Liu ◽  
Facheng Qiu ◽  
Jun Li ◽  
Changyuan Tao ◽  
...  
Keyword(s):  
Reference Frames ◽  
Cfd Simulation ◽  
Energy Dissipation Rate ◽  
Solid Particles ◽  
Stirred Tank ◽  
Two Phase ◽  
Stirred Reactor ◽  
Solid Suspension ◽  
Computational Fluid Dynamics Cfd ◽  
Solid Liquid

Abstract Solid suspension characteristics were predicted by computational fluid dynamics (CFD) simulation in a stirred tank driven by a dual rigid-flexible impeller and a dual punched rigid-flexible impeller. An Eulerian-Eulerian approach, standard k-ε turbulence model, and multiple reference frames (MRF) technique were employed to simulate the solid-liquid two-phase flow, turbulent flow, and impeller rotation in the stirred tank, respectively. The CFD results showed that dual punched rigid-flexible impeller could increase the axial velocity and turbulent kinetic energy dissipation rate, and decrease the quantity of sediment solid particles compared with dual rigid-flexible impeller. Less impeller power was consumed by dual punched rigid-flexible impeller compared with dual rigid-flexible impeller at the same impeller speed. It was found that punched rigid-flexible impeller was more efficient in terms of solid suspension quality than dual rigid-flexible impeller at the same Pw. The simulated results for the axial solid concentration were in good agreement with the experimental data.

Suspension of solid particles in multi-impeller three-phase stirred tank reactors

2001 ◽  
Vol 79 (1) ◽  
pp. 107-111 ◽  
Author(s):  
Naoki Dohi ◽  
Yukimasa Matsuda ◽  
Norihiro Itano ◽  
Kimio Minekawa ◽  
Takanori Takahashi ◽  
...  
Keyword(s):  
Solid Particles ◽  
Stirred Tank ◽  
Stirred Tank Reactors ◽  
Three Phase

A Comprehensive Review of Just Suspended Speed in Liquid-Solid and Gas-Liquid-Solid Stirred Tank Reactors

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Rouzbeh Jafari ◽  
Jamal Chaouki ◽  
Philippe A. Tanguy
Keyword(s):  
Operating Conditions ◽  
Stirred Tank ◽  
Geometrical Parameters ◽  
Optimum Level ◽  
Successful Operation ◽  
Stirred Tank Reactors ◽  
Comprehensive Knowledge ◽  
Solid Suspension ◽  
Successful Design ◽  
Scientists And Engineers

For successful design and operation of Liquid-Solid (LS) and Gas-Liquid-Solid (GLS) stirred tank reactors engineers and scientists must define geometrical and operating conditions for a specific medium (specified physical properties) in such a way that provides the optimum level of solid suspension. Failure to design the stirred tank reactor to achieve optimum conditions and maintain the system at these conditions during operation may be detrimental to product quality (selectivity and yield) and cost. Successful design and operation require comprehensive knowledge about how the state of solid suspension may be affected by changing physical, operational, and geometrical parameters. Also, accurate correlations are necessary to fulfill that objective. This article intends to provide that background for scientists and engineers. It critically surveys the published work in this field and makes specific recommendations for the appropriate conditions that provide the successful operation of agitated vessels.

scholarly journals CFD simulations of stirred-tank reactors for gas-liquid and gas-liquid-solid systems using OpenFOAM®

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xiaofei Hu ◽  
Aziz Dogan Ilgun ◽  
Alberto Passalacqua ◽  
Rodney O. Fox ◽  
Francesco Bertola ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Chemical Engineering ◽  
Flow Patterns ◽  
Solid Particles ◽  
Effective Density ◽  
Stirred Tank ◽  
Engineering Science ◽  
Stirred Tank Reactor ◽  
Stirred Tank Reactors ◽  
Tank Reactor

Abstract An open-source CFD software OpenFOAM® is used to simulate two multiphase stirred-tank reactors relevant to industrial processes such as slurry polymerization and fuel production. Gas-liquid simulations are first performed in a single-impeller stirred-tank reactor, studied experimentally by Ford, J. J., T. J. Heindel, T. C. Jensen, and J. B. Drake. 2008. “X-Ray Computed Tomography of a Gas-Sparged Stirred-Tank Reactor.” Chemical Engineering Science 63: 2075–85. Three impeller rotation speeds (200, 350 and 700 rpm) with three different bubble diameters (0.5, 1.5 and 2.5 mm) are investigated. Flow patterns compared qualitatively to those from experiments. Compared to the experimental data, the simulations are in relatively good agreement for gas holdup in the reactor. The second multiphase system is a multi-impeller stirred-tank reactor, studied experimentally by Shewale, S. D., and A. B. Pandit. 2006. “Studies in Multiple Impeller Agitated Gas-Liquid Contractors.” Chemical Engineering Science 61: 486–504. Gas-liquid simulations are performed at two impeller rotation speeds (3.75 and 5.08 RPS). The simulated flow patterns agree with published pictures from the experiments. Gas-liquid-solid simulations of the multi-impeller stirred-tank reactor are also carried out at impeller rotation speed 5.08 RPS. The addition of solid particles with a volume fraction characteristic of slurry reactors changes the flow pattern significantly. The bottom Rushton turbine becomes flooded, while the upper pitched-blade downflow turbines present a radial-pumping flow pattern instead of down-pumping. Nonetheless, the solid phase has a similar flow pattern to the liquid phase, indicating that the particles modify the effective density of the fluid.

An experimental investigation into vapor dispersion and solid suspension in boiling stirred tank reactors

2002 ◽  
Vol 41 (3) ◽  
pp. 267-279 ◽  
Author(s):  
N Dohi ◽  
Y Matsuda ◽  
K Shimizu ◽  
K Minekawa ◽  
Y Kawase
Keyword(s):  
Experimental Investigation ◽  
Stirred Tank ◽  
Stirred Tank Reactors ◽  
Vapor Dispersion ◽  
Solid Suspension

Simulation of flow field characteristics in scheelite leaching tank with H2SO4–H3PO4

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jiangtao Li ◽  
Guoxiang Cao ◽  
Zhongyang Tang ◽  
Zhongwei Zhao
Keyword(s):  
Calcium Sulfate ◽  
Low Cost ◽  
Flow Characteristics ◽  
Solid Particles ◽  
Stirred Tank ◽  
Environment Friendly ◽  
Mixed Acid ◽  
Solid Suspension ◽  
Flow Field Characteristics ◽  
Good Environment

Abstract Digesting scheelite by using H2SO4–H3PO4 is an environment-friendly and low-cost technology. The key approach to achieving efficient scheelite decomposition involves providing a good environment with uniform material composition for the growth of calcium sulfate. Therefore, numerical simulation of gypsum particle suspensions in a square stirred tank with a frame-type agitator for leaching scheelite was investigated. Simulated optimized results showed that the homogeneity of a multiphase flow system increased with the speed of the agitator. Reducing off-bottom clearance eased the dispersion of gypsum into the liquid. Adding baffles increased turbulence intensity and axial velocity in the tank, which eased solid suspension. The suspension improved, together with increases in the torque and power requirements of the agitator when the speed changed and baffled were added. However, when the solid suspension improved, the stirring torque and power slightly decreased, under a different off-bottom clearance of the agitator. Meanwhile, with residence time distribution as an evaluation criterion, the experimental results verified that the flow characteristics of the solid particles improved after optimization. This study can provide a theoretical basis and guidance for the optimization of the design and enlargement test of the stirred tank for leaching scheelite with sulfuric–phosphorous mixed acid.

Tracer test and hydraulics modeling of a large WWTP

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
C. Fall ◽  
N. Flores-Alamo ◽  
M. Esparza-Soto ◽  
C. M. Hooijmans
Keyword(s):  
Activated Sludge ◽  
Treatment Plant ◽  
Tracer Tests ◽  
Tracer Test ◽  
Stirred Tank ◽  
Mixing Models ◽  
Concentration Profiles ◽  
Stirred Tank Reactors ◽  
Rhodamine Wt ◽  
Sampling Schedule

Tracer tests with rhodamine WT were performed at the biggest wastewater treatment plant of Mexico (‘Dulces Nombres’ WWTP, 5 m3/s). The aim was to develop the hydraulics sub-model to represent the aeration tanks, in the context of a project for calibrating the activated sludge model N°1 (ASM1). The planning of the experiment was performed by pre-simulation in AQUASIM, which allowed determining the quantities of dye (8 L per reactor) and sampling schedule that were required. After the tests, the rhodamine concentration profiles of the outlet mixed liquors were fit with different alternative of tank mixing models. Simulating the tracer data allowed to estimate the unknown influent flows, as well as determine the best hydraulics model: 4 completely stirred tank reactors retro-connected through the RAS (return activated sludge).

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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