Technical letter report: Submerged bed scrubber sediment resuspension testing for the Hanford Waste Vitrification Plant

During-vitrification operations in the Hanford Waste Vitrification Plant (HWVP), some feed components will be vented from the melter to the melter offgas cleaning equipment. The current HWVP reference process for melter off.-gas treatment includes a submerged bed scrubber (SBS) to provide the first stage of off-gas scrubbing and quenching. During most melter/off-gas test runs at Pacific Northwest Laboratory (PNL) with the Pilot Scale Ceramic Melter (PSCM) and at the West Valley Demonstration Project (WVDP), no significant quantities of sedimentation were accumulated in the SBS scrub tank. However, during test run SF-12, conducted at West Valley, approximately 6 in. of sedimentation accumulated in the scrub tank. This raised concerns that a similar accumulation could occur with the HWVP SBS, If such an accumulation rate occurred during a sustained melter run, the SBS would soon cease to function. To alleviate the potential for sedimentation buildup, the HWVP SBS design includes a sparge ring at the bottom of the scrub tank. The sparge ring will be operated intermittently to prevent buildup of solids which could interfere with circulation with the SBS Scrub tank. This report presents the results of testing conducted to evaluate the effectiveness of the HWVP sparge ring design. Section 2 contains-the conclusions and recommendations; Section 3 summarizes the objectives; Section 4 describes the equipment and materials used; Section 5 gives the experimental approach; and Section 6 discusses the results. The appendices contain procedures for sediment resuspension testing and particle size distribution data for silica and sediment.