Power Consumption in Stirred Tanks Provided with Multiple Pitched-Blade Turbines

Armenante, Piero M.; Mazzarotta, Barbara; Chang, Gwo-Ming

doi:10.1021/ie980692o

Cited by 35 publications

(21 citation statements)

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“…The power number N p , is based on an angular momentum balance around the impeller1–3, 71 and is one of the most widely used design specifications in mixing operations The power number is a function of the Reynolds number and geometry of the system, including all dimensions of the impeller and the position(s) of the impeller(s) in the tank,4, 5 but the most significant variable is the geometry of the impeller 1, 6. For fully turbulent flow of a single‐phase fluid, N p is a constant.…”

Section: Introductionmentioning

confidence: 99%

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

et al. 2011

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Current literature relies almost exclusively on the power number to compare and characterize impellers. Industrial mixing requirements may rely on conditions far away from the impeller. A protocol is proposed to compare impellers designed for turbulent mixing on the basis of impeller hydrodynamic performance and mixing process objectives. A hydrofoil impeller (KPC), and a mixed‐flow impeller (45° down‐pumping PBT), each at two diameters, were used to test the protocol. Fourteen measures were considered. Five are recommended for full characterization: power number, momentum number, and peak rate of dissipation of turbulent kinetic energy to characterize conditions at the impeller; power at just‐suspended speed to compare the efficiency of solids suspension at the bottom of the tank; and point of air entrainment as a measure of turbulence penetration to the free surface. These five measures provide complete information about mixing performance and good differentiation between the impellers and geometries. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2573–2588, 2012

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Section: Introductionmentioning

confidence: 99%

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

et al. 2011

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“…In order to design stirred tank reactors for a three-phase system confidently, information on the hydrodynamics is required. Most previous research has focused on the solid suspension or power consumption in a multi-impeller three-phase system with impellers of the traditional Rushton or pitched-blade turbine types (Dutta and Pangarkar, 1995;Saravanan et al, 1997;Armenante et al, 1999;Dohi et al, 2001). The results reflect confusion about the effect of solids on gas holdup and gas-liquid mass transfer, with conflicting results indicating an increase, decrease, or no effect on the gas holdup and mass transfer coefficients in three-phase systems (Kawase et al, 1997a).…”

Section: Introductionmentioning

confidence: 99%

Gas Dispersion and Solid Suspension in a Three-Phase Stirred Tank With Multiple Impellers

Bao

Hao

Gao

et al. 2006

Chemical Engineering Communications

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Despite much research on gas-liquid-solid systems and their widespread application in industry, gas dispersion with solid suspension in multistage stirred reactors equipped with multiple impellers has received little attention. We report here the critical just-suspension impeller speed for different concentrations of solid particles, gas holdup, and shaft power in a vessel of 0.48 m diameter with four baffles and dished base. Five agitator configurations, each with three impellers mounted on a single shaft, have been used in the experiments. Two novel impeller designs were used, a deep hollow blade (semi-ellipse) disc turbine (HEDT) and four-wide-blade hydrofoil impellers. The hydrofoils were used in both up-pumping (WH U ) and down-pumping (WH D ) modes. Glass beads of 50 $ 150 lm diameter and density 2500 kg Á m À3 were suspended at solid volumetric concentrations of 1.5, 3, 6, 9, and 15%. Results show that these suspended solids have little effect on the relative power demand. Agitators using the HEDT radial dispersing impeller at the bottom have a higher relative power demand (RPD ¼ P G =P U ) than those with WH D or WH U as the lowest one. For all impeller combinations there is little or no effect on gas holdup with increasing solid concentrations. Of the five different impeller combinations, those with an axial flow bottom impeller have significantly higher just-suspension agitation speeds and power consumption, so mounting the hydrofoil impeller at the bottom is not the optimal configuration for particle suspension. Of these impeller combinations, at a given gas flow rate the arrangement of HEDT þ 2WH U has the highest relative power demand, gas holdup, and power input for both the suspension of settling particles and gas dispersion.

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“…The flotation cell is modeled after the Rushton flotation cell (Rushton, Costich et al 1950;Deglon, O'Connor et al 1997;Armenante, Mazzarotta et al 1999;Jenne and Reuss 1999) as shown in Figure 3 Feed entered the flotation cell mid-way up one side. On the opposite side, tailings were pumped from the bottom of the cell with a variable speed peristaltic pump.…”

Section: Methodsmentioning

confidence: 99%

Establishment of the Center for Advanced Separation Technologies

Hull¹

2006

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INTRODUCTIONThe U.S. is the largest producer of mining products in the world. In 1999, U.S. mining operations produced $66.7 billion worth of raw materials that contributed a total of $533 billion to the nation's wealth. Despite these contributions, the mining industry has not been well supported with research and development funds as compared to mining industries in other countries. To overcome this problem, the Center for Advanced Separation Technologies (CAST) was established by Virginia Tech and West Virginia University to develop technologies that can be used by the U.S. mining industry to create new products, reduce production costs, and meet environmental regulations. This endeavor is supported through U.S. DOE Cooperative Agreement No. DE-FC26-01NT41091: Establishment of the Center for Advance Separation Technologies.Much of the research to be carried out at CAST will be longer-term, high-risk, basic research, and will be carried out in four broad areas: a) Solid-solid separation b) Solid-liquid separation c) Chemical/Biological extraction, and d) Sensor and control development.Distribution of funds has been handled via competitive solicitation of research proposals through Site Coordinators at the two universities. Two RFP's have been issued to date. The first of these, referred to as the CAST I -Round 1 RFP, was issued on August 17, 2001 and closed October 15, 2001. A total of 12 proposals were received in response to this first RFP. These were first reviewed and ranked by a group of technical reviewers (selected primarily from industry). Based on these reviews, and an assessment of overall program requirements, the CAST Technical Committee made an initial selection/ranking of proposals and forwarded these proposals to the DOE/NETL Project Officer for final review and approval. This process took some 6 months to complete but 8 projects were in place at the constituent universities (5 at Virginia Tech and three at West Virginia University) by May 17, 2002. This was followed, on June 1, 2002 with the CAST I -Round 2 RFP, which closed on July 19, 2002. A total of 12 proposals were received in response to this second RFPfive were selected for funding. These were in place at the constituent universities (2 at Virginia Tech and 3 at West Virginia University) by March 1, 2003.All thirteen of these projects are listed below by category, along with brief abstracts of their aims and objectives. The recovery of coarse particles by flotation is a common problem in the coal and minerals processing industry. The objective of this project is to develop methods of extending the upper particle size limit for flotation. The availability of such a technology will improve processing efficiency and greatly simplify the plant flowsheet. Two different complementary approaches will be used to achieve the project objective. One is to use novel flotation reagents that will help increase the attachment force between air bubbles and coarse particles, and the other is to develop new flotation machines specifically de...

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Power Consumption in Stirred Tanks Provided with Multiple Pitched-Blade Turbines

Cited by 35 publications

References 13 publications

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

Gas Dispersion and Solid Suspension in a Three-Phase Stirred Tank With Multiple Impellers

Establishment of the Center for Advanced Separation Technologies

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