Suspension of ultrahigh concentration solids in an agitated vessel

Wang, Steven; Parthasarathy, Rajarathinam; Bong, Eng Ying; Wu, Jie; Slatter, Paul

doi:10.1002/aic.12657

Cited by 36 publications

(55 citation statements)

References 22 publications

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“…There is a rich literature on the role of power input in the design and operation of mechanically agitated stirred tanks . In the current study, impeller power consumption was determined by measuring the reactive torque experienced by the impeller shaft using a strain gauge–telemetry system.…”

Section: Methodsmentioning

confidence: 99%

Size distribution of bubbles in agitated viscous Newtonian and non‐Newtonian solutions

Momiroski

Bhattacharya

Davoody

et al. 2018

Asia-Pacific J Chem Eng

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The effects of impeller type, Newtonian shear thinning liquid viscosities, and noncoalescing conditions on the impeller gas cavities, impeller power consumption, and Sauter mean bubble diameter (d 32 ) in a multiphase agitated vessel were systematically studied. An underwater recording technique was used to study gas cavities and bubble size in various operating and design conditions. The gas cavity images were used to relate d 32 to gas cavity structure. It was observed that d 32 values increase with an increase in Newtonian and shear thinning liquid viscosities. Results also indicate that impellers operating in shear thinning liquids consume higher gassed power at the same operating conditions compared with those in Newtonian fluids. In addition, the d 32 values in noncoalescing liquids are substantially smaller compared with those in coalescing solutions at the same P g /V. Mathematical correlations are proposed for estimating the d 32 in the impeller discharge stream and P g /V in viscous Newtonian and non-Newtonian solutions.KEYWORDS bubble size, gas cavities, gas-liquid hydrodynamics, mathematical correlations, non-Newtonian liquid, power consumption Nomenclature and symbols:Greek letters: σ, surface tension, N/m; η, microscale of turbulence, m; ρ L , liquid phase density, kg/m 3 ; μ L , liquid phase viscosity, Pa·s; μ G , gas phase viscosity, Pa·s; τ, torque, N·m; v, kinematic viscosity of liquid, m 2 /s Letters and subscripts: a G-L , gas-liquid interfacial area, m 2 /m 3 ; C, impeller clearance, m; Ca c , critical capillary number, dimensionless; D, impeller diameter, m; d, particle size, m; d max , maximum stable diameter, m; d 32 , Sauter mean diameter, m; d bi , average bubble diameter in Equation (2), m; ε, energy dissipation rate, W/kg; G, strength of the applied strain rate around the bubble, 1/s; g, gravitational acceleration, m/s 2 ; H, liquid height, m; k, impeller constant; L, scale of the main flow, m; M s , mass of solids, kg; N, impeller speed, rps; n i , number of bubbles in Equation (2); N jsg , impeller speed for complete off-bottom solids suspension in three-phase systems, rps; N js , impeller speed for complete off-bottom solids suspension in two phase systems, rps; N P , power number; P g , gassed power input, W; S, dimensional coefficient; Q g , gas flow rate, vvm; T, tank diameter, m; V, liquid volume, m 3 ; V S , superficial gas velocity, m/s; vvm, volumetric flow rate of gas per minute per volume of liquid in the tank; u 2 , mean square velocity difference, m 2 /s 2 ; X, solid loading ratio, kg/kg Abbreviations: CMC, carboxymethyl cellulose; MIBC, methyl isobutyl carbinol

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Section: Methodsmentioning

confidence: 99%

Size distribution of bubbles in agitated viscous Newtonian and non‐Newtonian solutions

Momiroski

Bhattacharya

Davoody

et al. 2018

Asia-Pacific J Chem Eng

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“…In the processing industry, some stirred reactors are often operated satisfactorily with rigid or deformable particles circulating at the lower region of the stirred reactor given that the particles are sustained in active or semi‐active flow. In this case, they are operated at degrees of stirring around the so‐called just‐off‐bottom condition 8–12. However, this is not sufficient for many industrial cases, and a great number of applications expect the solids or catalysts to be completely dispersed or distributed throughout the reaction and crystallization systems.…”

Section: Introductionmentioning

confidence: 99%

Optimized Stirred Reactor for Enhanced Particle Dispersion

et al. 2016

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Homogeneous dispersion of particles is crucial for many processes where the reaction rate is highly dependent on relative rates of mixing or degree of homogenization. These processes include crystallization, polymerization, and some mineral-refining processes. Complete particle dispersion in high-concentration slurries is researched experimentally and numerically. Computation fluid dynamics results suggest that cloud height is an excellent indicator for mixing homogeneity, and energy efficiency can be enhanced by removing baffles over a range of solids concentrations under the complete dispersion condition. The power required to maintain a high cloud height in a stirred tank can be predicted via a simple power number analysis. The proposed unbaffled design can be potentially beneficial to some industrial processes like crystallization.

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“…In order to maintain the given goals, process intensification appears to be one attractive strategy to notably minimize unit volume while keeping the productivity in the mineral refineries. The ultimate goal of process intensification was proposed to intensify the mixing units that deal with ultra-high concentration reactive and/or inert particles in complex fluids (Wang et al, 2012a(Wang et al, , 2012b(Wang et al, , 2016aWu et al, 2016). Ultra-high (fine) solids loadings tend to modify slurry viscosity and/or rheology, and recent experimental and theoretical analysis have showed that homogenization of high concentration slurries in the stirred reactors is rather difficult (Wang et al, 2012a(Wang et al, , 2012b(Wang et al, , 2016a.…”

Section: Mixing Of Suspension With High Concentration Solidsmentioning

confidence: 99%

“…The ultimate goal of process intensification was proposed to intensify the mixing units that deal with ultra-high concentration reactive and/or inert particles in complex fluids (Wang et al, 2012a(Wang et al, , 2012b(Wang et al, , 2016aWu et al, 2016). Ultra-high (fine) solids loadings tend to modify slurry viscosity and/or rheology, and recent experimental and theoretical analysis have showed that homogenization of high concentration slurries in the stirred reactors is rather difficult (Wang et al, 2012a(Wang et al, , 2012b(Wang et al, , 2016a. The challenges are linked to the formation of stagnant regions (e.g., cavern) and isolate mixing regions (IMRs), settling of heavy particles and flotation of light particles (Wang et al, 2013;Wu et al, 2016).…”

Section: Mixing Of Suspension With High Concentration Solidsmentioning

confidence: 99%

Intensification of Mixing Processes with Complex Fluids

Ohmura

Masuda

Wang

2018

J. Chem. Eng. Japan / JCEJ

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The present paper provides an overview of the intensi cation of mixing processes with complex uids. First, mixing processes of rheologically complex uids and their design methodology are discussed. An example of process intensi cation of mixing with rheologically complex uids using a Couette-Taylor ow reactor is introduced. Second, the intensi cation of the mixing of a suspension with high concentration solids and a novel approach for solid-liquid separation using a stirred vessel are discussed. Finally, a perspective of the intensi cation of mixing processes with complex uids is summarized.

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Suspension of ultrahigh concentration solids in an agitated vessel

Cited by 36 publications

References 22 publications

Size distribution of bubbles in agitated viscous Newtonian and non‐Newtonian solutions

Size distribution of bubbles in agitated viscous Newtonian and non‐Newtonian solutions

Optimized Stirred Reactor for Enhanced Particle Dispersion

Intensification of Mixing Processes with Complex Fluids

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