Tank 5 Model for Sludge Removal Analysis

LEE, SI

Savannah River Site (S.C.)

关键词: Removal;    Sludges;    Orientation;    Oscillation Modes;    Computational Approach;   

DOI  :  10.2172/835095
RP-ID  :  WSRC-TR-2004-00418
RP-ID  :  AC09-96SR18500
RP-ID  :  835095

美国|英语

来源: UNT Digital Library

【 摘 要 】

Computational fluid dynamics methods have been used to develop and provide slurry pump operational guidance for sludge heel removal in Tank 5. Flow patterns calculated by the model were used to evaluate the performance of various combinations of operating pumps and their orientation under steady-state indexed and transient oscillation modes. A model used for previous analyses has been updated to add the valve housing distribution piping and pipe clusters of the cooling coil supply system near pump no. 8 to the previous tank Type-I model. In addition, the updated model included twelve concrete support columns. This model would provide a more accurate assessment of sludge removal capabilities. The model focused on removal of the sludge heel located near the wall of Tank 5 using the two new slurry pumps. The models and calculations were based on prototypic tank geometry and expected normal operating conditions as defined by Tank Closure Project Engineering. Computational fluid dynamics models of Tank 5 with different operating conditions were developed using the FLUENT (trademark) code. The modeling results were used to assess the efficiency of sludge suspension and removal operations in the 75-ft tank. The models employed a three-dimensional approach, a two-equation turbulence model, and an approximate representation of flow obstructions. The calculated local velocity was used as a measure of sludge removal and mixing capability. For the simulations, modeling calculations were performed with indexed pump orientations until an optimum flow pattern near the potential location of the sludge heel was established for sludge removal. The calculated results demonstrated that the existing slurry pumps running at 3801 gpm flowrate per nozzle could remove the sludge from the tank with a 101 in liquid level, based on a historical minimum sludge suspension velocity of 2.27 ft/sec. The only exception is the region within maximum 4.5 ft distance from the tank wall boundary at the we st corner of the tank. Further results showed that the capabilities of sludge removal were affected by the presence of twelve concrete support columns, the indexed pump orientation, the number of operating pumps, and the pump flowrate. The major impact of the results for the presence of the 2-ft support columns is that the sludge cleaning distance is reduced by about 1.5 ft, compared to the model with no support columns. However, the impact of the cleaning distance for the presence of 2-in cooling coil pipe clusters near the pump nozzle is found to be negligible. Sensitivity results showed that for a given tank level and pump location, a higher pump flowrate would result in better performance in suspending and removing the sludge. The results also showed that the presence of flow obstructions such as concrete support columns were advantageous for certain pump orientations in terms of guidance of the flow direction.