International Journal of Scientific Engineering and Technology Volume No.2, Issue No.6, pp : 492-495
(ISSN : 2277-1581) 1 June 2013
Fluid to Particle Mass Transfer Studies in Downers R.Praveen Kumar1, Anurag Parihar2, 1.Department of Chemical Engineering, SASTRA University, Thanjavur Tamil Nadu email id: praveenkumar@scbt.sastra.edu; praveenrevuri@yahoo.co.in 2. Process Engineer Dr. Reddyâ€&#x;s Laboratory Hyderabad. Abstract- Gases to particle mass transfer coefficients are measured in a downer.The effects of gas velocity, solid flux and particle size on Mass transfer coefficients are studied. The effect of downer diameter on Mass transfer coefficients was studied by plotting Mass transfer coefficients in terms of dimensionless parameters. Downers are down flow fluidized beds. They offer several advantages compared to risers. 1. Reduced gas and solid back mixing. 2. Reduced contact time between different phases 3.Better control over the reactions. These advantages become significant in several fields where down flow fluidized beds (downers) are used e.g. petroleum industry (FCC), glass industry, fertilizer industry, etc.Some studies have already been done on other parameters of downers like Heat transfer, Particle velocity profiles, etc. The present work reports experimental observation on fluid to particle mass transfer in downers. Keywords- Downers, FCC, Mass transfer coefficients, Solid flux
EXPERIMENTAL SECTION Solid storage
Downer
Water Empty drum tank
Sand collector.
1. INTRODUCTION. The key benefits of downers over risers are: reduced gas and solid backmixing near the wall region, reduced contact time between gas and solid phases, plug flow behavior and so on. These advantages become more significant in the fields of fluid catalytic cracking and combustion reactions. Some information is available in the literature on hydrodynamics of downers such as particle velocity profiles[3],axial and radial solid flux profiles[1], solid holdup and pressure gradient distributions[2],[4],[5],[8],reactor performance[6],[9], and heat transfer studies[11].
Air Compress or. Experiments were conducted in downers of height (88cm) and internal diameters (5cm) made with Plexiglas. The experimental set up is as shown in fig. Washed and dried sand kept in solid storage tank few minutes before start of experiment. Air from compressor send into water drum (33cmID, 55cm height) to get saturated air. The exit air from water drum again send to an empty tank(37cmID,58cmheight) to avoid entrained water
For gas- solid reactions in downers, in general, are fast and so can be limited by gas phase mass transfer to solid surface. In general mass transfer rates depend on mass transfer coefficient, gas velocity, and Particle size and so on. The present work reports experimental observations on to gas to particle mass transfer in downers.
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