A solids mixing rate correlation for small scale fluidized beds--颗粒学报PARTICUOLOGY

Gorji-Kandi, S., Alavi-Amleshi, S. M., & Mostoufi, N. (2015). A solids mixing rate correlation for small scale fluidized beds. Particuology, 21, 55-64. https://doi.org/10.1016/j.partic.2014.10.003

A solids mixing rate correlation for small scale fluidized beds

S. Gorji-Kandi ^a, S.M. Alavi-Amleshi ^a, N. Mostoufi ^b *

a Department of Chemical Engineering, Iran University of Science and Technology, Tehran, Iran
b School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran

10.1016/j.partic.2014.10.003

Volume 21, August 2015, Pages 55-64

Received 16 July 2014, Revised 18 September 2014, Accepted 6 October 2014, Available online 31 December 2014, Version of Record 6 June 2015.

E-mail: mostoufi@ut.ac.ir

Highlights

• Digital image processing method was applied to obtain the tracer concentration.

• Mixing rate was evaluated by analyzing the evolution of mixing index.

• A correlation was proposed to estimate the mixing rate in a small scale fluidized bed.

Abstract

A new first degree solids mixing rate is proposed to evaluate the mixing of solids in small scale fluidized beds. Particle mixing experiments were carried out in a 2D fluidized bed with a cross-section of 0.02 m × 0.2 m and a height of 1 m. White and black particles with average diameters of 850 and 450 μm were used in our experiments. Image processing was used to measure the concentration of the tracers at different times. The effects of four representative operating parameters (superficial gas velocity, ratio of tracer particles to bed particles, tracer particle position, and particle size) on mixing are discussed with reference to the mixing index. We found that the Lacey index depends on the concentration of the tracers. The position of the tracers affects the initial mixing rate but not the final degree of mixing. However, the new mixing rate equation does not depend on the initial configuration of the particles because this situation is considered to be the initial condition. Using the data obtained in this work and that found in literature, an empirical correlation is proposed to evaluate the mixing rate constant as a function of dimensionless numbers (Archimedes, Reynolds, and Froude) in small scale fluidized beds. This correlation allows for an estimation of the mixing rate under different operating conditions and for the detection of the end point and/or the time of mixing.

Graphical abstract

Keywords

Fluidized bed; Solids mixingTracer; Digital image processing; Mixing index; Mixing rate

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