Solids concentration profiles at different heights, in a T=500 mm vessel mechanically stirred by a Lightnin A310 impeller, were measured by means of electrical impedance technique. A new probe was designed and employed. Its main advantage is that it is absolutely non-intrusive and that it can be used for laboratory as well as for industrial scale stirred tank reactors. Two sets of spherical glass particles (density of ρS=2500 kg/m3) of narrow size distribution (dp=90 and 600 μm) and solids load up to 40% (wt.solid/wt.liquid x100) were used. Three sizes of a Lightnin A310 impeller, set a clearance C=T/4 from the vessel flat bottom, were used: D/T= 0.346, 0.386 and 0.5. The liquids used were water and aqueous solutions of glycerine (Newtonian behaviour, viscosity 1 to 10 mPa s). Power consumption was determined with a strain gauge technique. For solid loadings greater than 10% and depending on the stirrer speeds, an interface between the suspension and a clear liquid layer was observed towards the top of the vessel. This is of critical importance in slurry catalyst reactor design, as mixing between the dense suspended layer and the clear liquid above it is very limited. Besides solid concentration distribution, both power consumption and height of interface were measured at each impeller speed.
Experimental measurements of solid concentration distribution in mechanically stirred solid-liquid systems
BRUNAZZI, ELISABETTA;PINTUS, SANDRO
2004-01-01
Abstract
Solids concentration profiles at different heights, in a T=500 mm vessel mechanically stirred by a Lightnin A310 impeller, were measured by means of electrical impedance technique. A new probe was designed and employed. Its main advantage is that it is absolutely non-intrusive and that it can be used for laboratory as well as for industrial scale stirred tank reactors. Two sets of spherical glass particles (density of ρS=2500 kg/m3) of narrow size distribution (dp=90 and 600 μm) and solids load up to 40% (wt.solid/wt.liquid x100) were used. Three sizes of a Lightnin A310 impeller, set a clearance C=T/4 from the vessel flat bottom, were used: D/T= 0.346, 0.386 and 0.5. The liquids used were water and aqueous solutions of glycerine (Newtonian behaviour, viscosity 1 to 10 mPa s). Power consumption was determined with a strain gauge technique. For solid loadings greater than 10% and depending on the stirrer speeds, an interface between the suspension and a clear liquid layer was observed towards the top of the vessel. This is of critical importance in slurry catalyst reactor design, as mixing between the dense suspended layer and the clear liquid above it is very limited. Besides solid concentration distribution, both power consumption and height of interface were measured at each impeller speed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
