CST Suspension Analysis for Slurry Pumps of Tank 40
Tank 40 simulation models with four submersible slurry pumps available for the CST suspension operations have been developed to provide operational guidance of slurry pumps for an efficient sludge removal. A series of the modeling calculations have been performed for key operational parameters such as pump operation mode, number of operating pumps, and to provide a recommendation for CST suspension and mixing operations in Tank 40. Reference design and operating conditions shown in Table 1 were used to perform the modeling analysis of the tank CST mixing. In the analysis, the pump was assumed to be stationary or rotating. Solid obstructions including the pump housing, the 14 inches riser, and 6.75-ft tank support column were included in the simulation models. Free surface motion of the tank liquid was neglected for high tank liquid level using the literature information. Steady-state and transient analyses with a two-equation turbulence model were performed with FLUENTTM. All analyses we re based on three-dimensional results. A suspension capability was evaluated assuming that local fluid velocity can be used as a measure of CST suspension and mixing. For a minimum suspension velocity of 1.1 ft/sec for the largest CST size of 700 microns, the results indicated that at least two existing slurry mixers running at 3800 gpm flowrate per nozzle could keep CST solids suspended from the tank with a 200 in liquid level. In this case, the exception is for the fluid region with less than 20 wt contents of CST material. This is based on the conservative assumption that the largest CST size of 700 micron diameter remains unchanged neglecting a friable effect during the entire period of pump operations. The length of time that the CST material is exposed to the liquid stream lower than minimum suspension velocity is also important in affecting the ability of the liquid stream to suspend CST particle, and this effect is quantified in the present analysis by using the literature result s. The model results show that at least two pumps on opposite sides could keep suspending the CST material based on the slurry with 35 wt contents, but that at lower concentrations, particles larger than about 400 microns would tend to settle quickly and probably not remain in suspension long enough for the opposite jet to come around and stir that region of the tank. The main conclusions are as follows: The steady-state flow patterns on the horizontal discharge plane follow a series of parabolic curves similar to that of a free jet available in the literature. For the simulations, a series of the modeling calculations was performed with indexed stationary and rotating pump operations. The calculated results demonstrated that the existing slurry pumps running at 7600 gpm could suspend the CST particles from the tank with a 200 in liquid level, based on a minimum sludge suspension velocity of about 1.1 ft/sec for 700 micron CST particle. The suspension distance for the transient model with pump rotations is smaller than that of the steady-state model with indexed pump orientations for given operating conditions. However, total suspension extents for the two modeling cases have about the same area.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 828772
- Report Number(s):
- WSRC-TR-2004-00207; TRN: US0404280
- Resource Relation:
- Other Information: PBD: 1 Apr 2004
- Country of Publication:
- United States
- Language:
- English
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