article posted 09 Jan 2016
Pavel Hrma Pavel Hrma is a scientist emeritus at the
Pacific Northwest National Laboratory, Richland, Washington.
Feed-to-melt conversion process
Pavel Hrmaa*, Derek R. Dixona,
Bradley R. VanderVeera, Benjamin P. McCartya,
Carmen P. Rodrigueza,
Jaehun Chuna, Richard Pokornyb,
Tetsuji Yanoc, Michael J. Schweigera,
Albert A. Krugerd
Conversion of nuclear waste melter feed to molten glass proceeds in two stages.
First, multiple feed reactions evolve copious amounts of gases that are released
through open pores. Second, the glass-forming phase traps residual gases,
giving rise to a transient foam layer. When the foam collapses and residual
refractory grains completely dissolve, the conversion process is virtually
completed. In the waste glass melter, the rate of the conversion process
(the glass production rate) depends on the feed spreading on the surface
of molten glass, the heat needed to convert the feed to melt, and heat transfer
rate from the melt pool through the foam layer to the reacting feed layer.
To understand the spreading of the feed slurry, basic rheological parameters
of drying feed slurry and dry reacting feed were determined. The conversion
heat was measured with simultaneous differential scanning calorimetry-thermal
gravimetry. The volume expansion of feed (foaming) was monitored by observing
heated feed pellets.
The cold cap (the body of feed floating on molten glass in a
continuous waste glass melter in the process of conversion) was produced and
monitored in the laboratory-scale melter (LSM). Quenched cold caps were analyzed
for spatial distribution of the extent of conversion. Effects of selected feed makeup
parameters, such as the glass-forming melt viscosity and particle size of quartz
(added as a glass former), were evaluated.
(a) Pacific Northwest National Laboratory, 902 Battelle Blvd.,
Richland, WA 99352, USA
(b) Department of Chemical Engineering, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
(c) Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku
(d) U.S. Department of Energy, Office of River Protection,
Richland, WA 99352