Jet Mixing of Liquids in Long Horizontal Cylindrical Tanks

Abstract

Large storage tanks may require mixing to achieve homogeneity of contents for several reasons: prior to sampling for mass balance purposes, for blending in reagents, for suspending settled solids for removal, or for use as a feed tank to a process. At Oak Ridge National Laboratory, mixed waste evaporator concentrates are stored in ∼190-m3 (50 000-gal) horizontal tanks, about 3.7 m (12 ft) in diameter and 18 m (60 ft) in length. This tank configuration has the advantage of permitting transport by truck and therefore fabrication in the shop rather than in the field. A survey of the literature revealed no information on mixing large storage tanks with length-to-diameter ratios greater than 2. Jet mixing experiments were carried out in two model tanks: a 0.87-m3 (230-gal) Plexiglas tank that was ∼1/6 linear scale of the actual waste tanks and a 95-m3 (25 000-gal) tank that was about 2/3 linear scale of the actual waste tanks. Mixing times were measured by the use of a sodium chloride tracer and several conductivity probes distributed throughout the tanks. Several jet sizes and configurations were tested. In the 0.87-m3 tank, jet diameters of 0.016, 0.022, and 0.041 m (0.62, 0.87, and 1.61 in.) were used. In the 95-m3 tank, jet diameters of 0.035 and 0.049 m (1.38 and 1.93 in.) were used. One-directional and two-directional jets were tested in both tanks. Mixing times for each tank were correlated with the jet Reynolds number and for the two tank sizes using the recirculation time for the developed jet.

Mixing in a fluid jet agitated tank: effects of jet angle and elevation and number of jets

“…The equilibrium temperature, T , can be easily calculated and was found to be 302:7295 K. The mixing time was measured according to the above criterion which means that the temperature at any point inside the tank should be in the range of 300 ± 0:136475 K. The numerical model can also be used to solve for concentration. Most experimental studies including those of Fossett and Prosser (1949), Fox and Gex (1956), Lane and Rice (1982) and Perona et al (1998) quantiÿed mixing by taking experimental readings of the measured variable at a small number of predetermined locations. These locations need not coincide with those where the mixing time is longest.…”

CFD Modelling and Simulation of Jet Mixed Tanks

“…It was reported that alternating jets gives 15% less mixing time at the same power input as compared with steady jets. Perona et al (1998) studied the performance of jet mixers in long horizontal tanks. Considerable literature and measurements on jet mixing in tanks are available.…”

On the computational fluid dynamics (CFD) analysis of the effect of jet nozzle angle on mixing time for various liquid heights

“…Generally, the surrounding fluid is entrained by jet within L/d of 400 (Harnby et al, 1997;Perona et al, 1998;Wasewar and Sarathi, 2008). These results ensured that the jets can entrain the external liquid and generate the circulation inside the tanks.…”