Energy efficiency study on axial flow impellers

Wu, Jie; Graham, Lachlan; Nguyen, B.; Mehidi, Mohamed Nabil Noui

doi:10.1016/j.cep.2006.01.007

Cited by 28 publications

(15 citation statements)

References 9 publications

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“…10 In practice, this method is rather problematic, for example a single particle (or a small quantity) stationary in a corner may not be suspended even at very high-agitator speeds; thus, it is rather meaningless and unreliable to rely on the status of a small quantity of particles to determine the just off-bottom suspension condition. As an alternative approach, 11 the sedimentation bed height denoted as H B was recorded vs. the speed, as the impeller speed was reduced from a full solids suspension condition (at higher speeds). The just off-bottom speed N js is defined at a point where H B ¼ 0.…”

Section: Methodsmentioning

confidence: 99%

“…Figure 6b shows the effect of changing impeller type, where the essential difference between A310 and RTF4 is that the former has a higher power number (with three blades, P 0 ¼ 0.31) and the latter has a lower power number of 0.16 (four blades), whereas both use hydrofoils and are equally efficient in terms of pumping. 11 It is evident that the usage of a low power number impeller led to increased power consumption to suspend solids particles from the tank bottom at the current high solids concentration (0.40 v/v). Figure 7 shows the effect of removal of baffles.…”

Section: High Solids Concentration At Improved Energy Efficiencymentioning

confidence: 99%

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High solids concentration agitation for minerals process intensification

Wang

Graham

et al. 2010

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).By using mixing intensification involving high solids concentration as a means to achieve process intensification for the mineral process industry is discussed here. Improving agitator energy efficiency is essential for operating at high solids concentrations. It is shown that improved agitator energy efficiency can be achieved by removing baffles and using higher power number impellers at high solids loadings. Power consumption (50-80%) reductions were demonstrated in the experiments. It is also suggested that slurry stratification in tanks can be used to boost either solids residence time or slurry mass flow. Basic equations related to solids residence time and solids throughput are presented for guidance toward minerals process intensification. An example on doubling throughput via intensification is presented.

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Section: Methodsmentioning

confidence: 99%

Section: High Solids Concentration At Improved Energy Efficiencymentioning

confidence: 99%

High solids concentration agitation for minerals process intensification

Wang

Graham

et al. 2010

AIChE Journal

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show abstract

“…For a Reynolds number below 10,000 (e.g., at 600 rpm), the turbulent regime is reached after 30 h of hydrolysis. According to Wu et al [26], a decreased Reynolds number produces an increased chance for energy and mass transport improvements.…”

Section: Rheology Datamentioning

confidence: 98%

Sugarcane bagasse enzymatic hydrolysis: rheological data as criteria for impeller selection

Pereira

Teixeira

et al. 2010

J Ind Microbiol Biotechnol

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The aim of this work was to select an efficient impeller to be used in a stirred reactor for the enzymatic hydrolysis of sugar cane bagasse. All experiments utilized 100 g (dry weight)/l of steam-pretreated bagasse, which is utilized in Brazil for cattle feed. The process was studied with respect to the rheological behavior of the biomass hydrolysate and the enzymatic conversion of the bagasse polysaccharides. These parameters were applied to model the power required for an impeller to operate at pilot scale (100 l) using empirical correlations according to Nagata [16]. Hydrolysis experiments were carried out using a blend of cellulases, β-glucosidase, and xylanases produced in our laboratory by Trichoderma reesei RUT C30 and Aspergillus awamori. Hydrolyses were performed with an enzyme load of 10 FPU/g (dry weight) of bagasse over 36 h with periodic sampling for the measurement of viscosity and the concentration of glucose and reducing sugars. The mixture presented pseudoplastic behavior. This rheological model allowed for a performance comparison to be made between flat-blade disk (Rushton turbine) and pitched-blade (45°) impellers. The simulation showed that the pitched blade consumed tenfold less energy than the flat-blade disk turbine. The resulting sugar syrups contained 22 g/l of glucose, which corresponded to 45% cellulose conversion.

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“…Estas son descritas en tres categorías típicas: las de orden de magnitud del diámetro (o tamaño) de la máquina, fluctuaciones periódicas asociadas al paso de álabe y perturbaciones de pequeña escala, asociadas con las estructuras turbulentas del flujo. Para el diseño de tanques agitadores, se han establecido técnicas experimentales con el propósito de conocer parámetros de funcionamiento, el consumo de potencia, homogeneidad de fluidos, entre otros (Zwietering, 1958;Wu et al, 2006;Wu et al, 2010a;Wu et al, 2010b;Ibrahim, 2012). Además, a partir de ensayos experimentales se logra obtener correlaciones empíricas mediante la relación entre variables y parámetros de funcionamiento.…”

Section: Introductionunclassified

Estudio del Comportamiento Fluido-Dinámico de un Agitador a Escala Reducida Mediante Simulación Numérica

et al. 2017

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* Autor a quien debe ser dirigida la correspondenciaRecibido Sep. 25, 2016; Aceptado Dic. 9, 2016; Versión final Mar. 10, 2017, Publicado Jun. 2017 Resumen Se presenta el estudio del comportamiento de un agitador con impulsor hidroala (hydrofoil), usado para mezclar agua con partículas polimetálicas en la industria minera, mediante simulación numérica con software de dinámica de fluidos computacional (CFD). La mezcla tiene densidad promedio de 1.623 kg/m 3 , viscosidad aparente de 0.065 kg/m·s y fue modelada como un líquido homogéneo no-newtoniano. En la simulación el problema se resuelve mediante un modelo homogéneo Euler-Euler para flujo bifásico de superficie libre en estado estacionario, utilizando el modelo de turbulencia k-ε. Se obtuvo la curva de potencia, que relaciona el número de potencia (Np) con el número de Reynolds (Re), a partir de la curva de torque del impulsor en función de su velocidad angular entre 200 y 700 rpm. Se encontró que Np converge asintóticamente a 0.32 en régimen turbulento, valor que está en correspondencia con los resultados experimentales obtenidos en el presente estudio y los disponibles en la literatura. Palabras clave: agitador; número de potencia; impulsor hidroala; CFD; mezcladores Study of the Fluid-Dynamic Behavior of a Reduced Scale Stirred Tank through Numerical Simulation AbstractThis paper presents the study of the behavior of a stirred tank with hydrofoil impeller, used to mix water with polymetallic particles in the mining industry, through numerical simulation with CFD software. The mixture has an average density of 1.623 kg / m 3 and an apparent viscosity of 0.065 kg / m-s, and was modeled as a non-newtonian homogeneous liquid. The homogeneous Euler-Euler model for free surface biphasic flow in steady state is solved in the simulation, using the k-ε turbulence model. The power curve, which correlates the power number (Np) with the Reynolds number (Re), was obtained from the torque curve of the impeller versus its angular velocity between 200 and 700 rpm. It was found that Np asymptotically converges to 0.32 in turbulent regime, a value that is in agreement with experimental results obtained in the present study and those available in the literature.

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Energy efficiency study on axial flow impellers

Cited by 28 publications

References 9 publications

High solids concentration agitation for minerals process intensification

High solids concentration agitation for minerals process intensification

Sugarcane bagasse enzymatic hydrolysis: rheological data as criteria for impeller selection

Estudio del Comportamiento Fluido-Dinámico de un Agitador a Escala Reducida Mediante Simulación Numérica

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