article posted 14 Jan 2016
Richard Pokorny graduated in 2010 from the University of Chemistry and Technology
Prague with a Master of Science in chemical engineering. During his diploma thesis,
he focused on mathematical modeling of transport properties in heterophase polymers.
After that, he joined the Glass and Materials Science Team at the Pacific Northwest
National Laboratory as a post-master research associate under the supervision of
professor Pavel Hrma. From 2010 to this day, Richard is responsible for the development
of the mathematical model of a cold cap, and is thus interested in all kinds of
batch-to-glass conversion problems. In the meantime, he is also completing his
PhD studies at the University of Chemistry and Technology Prague.
Conversion of nuclear waste melter feed into glass:
Development and application of the cold cap mathematical model
Richard Pokorny *,1, Jaroslav Klouzek 1,
Donna P. Guillen 2, Pavel Hrma 3
The cost and schedule of nuclear waste treatment and immobilization is greatly
dependent upon the rate of glass production during vitrification. The melter feed
combines tank waste with glass additives mixed together in water based slurry.
This melter feed is charged into a Joule-heated melter from the top, where it forms
a porous layer of reacting and melting material that floats on the molten glass,
commonly referred to as the cold cap. Without an accurate model of the cold cap,
where the batch-to-glass conversion takes place, it is impossible to reliably predict
the melting rate and the melter performance.
In this work, we thus report on the
development of an advanced model of the cold cap. This model incorporates the
dynamic behaviour of the foam layer, which is formed by gas-evolving reactions
in the later stages of the batch-to-glass conversion process. The growth and collapse
of this foam layer controls the glass production rate.
Our previous mathematical
model of the cold cap was revised to include the functional representation of primary
foam behavior and to account for the slurry spreading at the cold cap upper surface.
The batch melting rate is computed as a response to the dependence of the primary
foam collapse temperature on the heating rate and melter operating conditions,
including the effect of bubbling on the cold cap lower and upper surface temperatures.
The simulation results are in good agreement with experimental data from
laboratory-scale and pilot scale melter studies. The cold cap model is being integrated
into the full three-dimensional computational fluid dynamic and heat transfer model
of the waste glass melter.
1 Laboratory of Inorganic Materials, Joint Workplace of the University of Chemical
Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic and the Institute
of Rock Structure and Mechanics of the ASCR, v.v.i., V Holesovickach 41, 182 09
Prague 8, Czech Republic
2 Idaho National Laboratory, 750 University Blvd., Idaho Falls, ID 83401, USA
3 Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, WA 99352, USA