Thermodynamic Modeling of the SRS Evaporators: Part V. Validation

Pareizs, J.M.

Savannah River Site (S.C.)

关键词: Evaporators;    Aluminium;    Sodium;    Hydroxides;    36 Materials Science;   

DOI  :  10.2172/816421
RP-ID  :  WSRC-TR-2002-00331
RP-ID  :  AC09-96SR18500
RP-ID  :  816421

美国|英语

来源: UNT Digital Library

【 摘 要 】

A thermodynamic model has been proposed to predict solids formation in the SRS evaporators from measured feed compositions using a commercially available software package, the Geochemist's Workbench (GWB). In support of this work, researchers at Pacific Northwest National Laboratory (PNNL) and Oak Ridge National Laboratory (ORNL) have performed experiments to evaluate solids formation under evaporator-like conditions in the laboratory. The purpose of this report is to compare these experimental results to the calculated results from GWB. Researchers at PNNL conducted experiments to evaluate the thermodynamic boundary between the precipitation of the deleterious sodium aluminosilicate gel (NASgel) and the field of benign potential precipitation of aluminum hydroxide formation. Several solutions were prepared and held at several temperatures to evaluate solids formation over various periods of time. Observed solids compared well to GWB calculations. Researchers at ORNL prepared several mixtures of simulated SRS Tank 43 (high aluminum) and DWPF recycle (high silicon) solutions. These solutions were then evaporated, and precipitated solids were examined by XRD. Again, there was good agreement between observations and GWB calculations. No NASgel was identified, and none was predicted to form. Researchers at ORNL also prepared several high caustic solutions, additional mixtures of simulated SRS Tank 43 and DWPF solutions, and simulated 3H evaporator feed. Solids deposition on stainless steel coupons with and without evaporation was examined. Because these solids were not rigorously characterized, direct comparison to GWB calculations is not appropriate. However, it should be noted that NASgel was not predicted by GWB to form, and no NASgel was identified in these experiments. Overall, the experimental observations validate the GWB calculational results, showing that GWB is an appropriate tool for use in SRS evaporator modeling and control.