Author
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DICKEY, LELAND |
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PARRIS, NICHOLAS |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 2/27/2004 Publication Date: 3/15/2004 Citation: Dickey, L.C., Parris, N. 2004. Transferring corn meal from an ethanol extract to water: settling dependence on fine particle content. Meeting Abstract. Corn: Feedstock of the Future. Corn Utilization Technology Conference Proceedings, June 7-9, 2004, Indianapolis, IN. Interpretive Summary: Technical Abstract: Separating solid particles from ethanolic corn extracts by gravitational settling into a water layer has been studied as part of a project to develop a low cost method to extract ethanol-soluble protein from corn meal (1). During settling some of the extract liquid is entrained by the settling extracted corn particles. The amount of liquid entrained was determined by measuring the ethanol transferred to the water after a batch of extract had been settled. When fine particles were pumped, as part of the extract, into the 7 liter settling layer at a high enough rate, they formed a particle layer at the extract liquid/water interface. A layer formed when settling was slower than the rate of particles transiting through the extract layer. The major variable in all sedimentation models is the local particle volume fraction. It is necessary to keep the local particle volume fraction below a critical value to prevent hindered settling. In the case of a liquid/liquid interface hindered settling leads to the formation of a dense consolidated layer that will retard the descent of the particles. At this critical volume fraction a suspension will no longer resist compression elastically and will irreversibly consolidate (2). No particle layer formed when the mass fraction of particles in the extract was .10 or less, this is higher than the very low value, ~0 that would have been extrapolated from published settling data for denser particles (3). Overall entrainment for the settling was about the same as entrainment during centrifugation. In-line measurements and recordings of ethanol concentration, density and particle content of the water stream carrying settled coarse particles from the settling tank showed that specific entrainment was greater for finer particles. Settling can be used for particle/liquid separations other than agricultural extracts, recovery of solvents used in coal conversion or wood pulping for example. In most cases solvent conservation is increasingly important and avoidance of solvent recovery by evaporation from a solids mass (the centrifuge dry product) is the primary benefit and saving the capital and operating expense of a solvent-capable centrifuge is a significant secondary advantage of settling a solvent/particle mixture. |
