A crucible salt saturation method for determining sulfur solubility in glass melt

Abstract

Experiments were conducted to determine sulfur solubility in Hanford low‐activity waste (LAW) glass melts by a sulfur saturation method. Sulfur‐incorporated glass melts were prepared by salt saturation and bubbling methods. The salt saturation method was performed by mixing crushed premelted baseline glasses with an excess amount of Na2SO4 prior to melting the mixture at 1150°C for 1 hour. The bubbling method involved bubbling the glass melt at 1150°C in a Pt crucible with an SO2/O2/N2 gas mix to equilibrate the melt at a known pressure of SO3. Preliminary results suggested that performing 1 cycle of mixing and melting was not sufficient to saturate the glass. The bubbling method successfully incorporated sulfur into the glass but caused significant losses of sodium from the melt. In order to saturate the glass melt with sulfate without causing noticeable sodium loss, a modified crucible salt saturation method was developed by repeating the mixing and melting of the glass and salt mixture. For all 3 representative LAW glasses tested in this study, it was found that after 3 mixing and melting cycles, the sulfur concentration reaches a plateau, indicating reasonable sulfur saturation.

Sulfur solubility in low activity waste glass and its correlation to melter tolerance

“…Thirteen of these glasses (Table ), with between 0.5% to 1.5 wt% SO 3 , were selected for this study . To evaluate the experimental errors of the sulfur solubility test, several duplicate tests were conducted and test results for three of the glass compositions examined in this study were also measured in a previous study and included for reference …”

“…This process was conducted to determine whether furnace time impacted sulfur solubility and melt volatility. There were also sulfur solubility test results for LAWA161, LAWB99, and ORPLG27 from previous work (Section S2, Table ). These three tests were completed earlier on the same glass compositions and under the same conditions, so they were treated as replicate samples to evaluate procedural uncertainties.…”

“…Melter feeds with high concentrations of sulfate salts are prone to salt segregation in the melter . Segregated salts are potentially damaging to the waste melters employed at the WTP due to high corrosivity .…”

“…A number of crucible‐scale experimental approaches have been used with significant differences in the resulting measured sulfate solubility () . Jin et al recently developed a simple and inexpensive measurement method that ensures equilibrium solubilities are obtained without excessive chemical changes due to volatility or salt extraction. Questions remain regarding how the results from this method compare to those of and what method uncertainties should be expected.…”

“…In this study, the Jin et al measurement method was applied to a series of glass compositions with previously reported values . The results are compared to better understand the relationship between thermodynamic solubility and segregation in nominal melter operating conditions and crucible tests.…”