Insight into ion exchange column dynamics through application of an analytical model of system performance

Abstract

ABSTRACT The Direct Feed Low-Activity Waste flowsheet provides for the early production of immobilized low-activity waste (LAW) by feeding waste directly from Hanford tank farms to the Hanford Tank Waste Treatment and Immobilization Plant (WTP) for vitrification. Prior to the transfer of feed to the WTP LAW Vitrification Facility, tank waste supernatant will be pretreated by the Tank Side Cesium Removal (TSCR) system to meet the WTP LAW waste acceptance criteria (<3.18E-5 Ci 137Cs/mole of Na). This pretreatment will remove cesium from the waste stream using ion exchange (IX). The selected media for IX is crystalline silicotitanate (CST), product number IONSIV-R9140-B, manufactured by Honeywell UOP LLC (Des Plaines, IL). Testing was conducted to improve the understanding of the parameters that impact dynamic ion-exchange performance and to better define IX processing using Low-Activity Waste Pretreatment System (LAWPS) prototypic IX unit operations. Column testing at full height scale was conducted to gain insight into ion-exchange column dynamics and evaluate the application of an analytical model on system performance. Nominal process conditions used 5.6 M Na simulant processed in a lead/lag column format containing 1.15 L 18 × 15 mesh CST in 2.54-cm-diameter columns, 226 cm tall CST beds. Two process flowrates were tested: 1.30 and 1.82 bed volumes (BV) per hour. This work demonstrated that an analytical method can provide a reasonable estimate of the expected performance within the bounds of the assumptions employed for the analytical solution.