Effect of Melter-Feed-Makeup on Vitrification Process

Abstract

Increasing the rate of glass processing in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) will allow shortening the life cycle of waste cleanup at the Hanford Site. While the WTP melters have approached the limit of increasing the rate of melting by enhancing the heat transfer rate from molten glass to the cold cap, a substantial improvement can still be achieved by accelerating the feed-to-glass conversion kinetics. This study investigates how the feed-to-glass conversion process responds to the feed makeup. By identifying the means of control of primary foam fonnation and silica grain dissolution, it provides data needed for a meaningful and economical design oflarge-scale experiments aimed at achieving faster melting.

Conversion of batch to molten glass, II: Dissolution of quartz particles

“…Kham [116] measured a for various commercial batches using a sensor operating with temperature pulses; a gradually increased from~3.5 × 10 − 7 m 2 s − 1 at 350°C to~4 × 10 − 7 m 2 s − 1 at 650°C. Values recently obtained for high-level waste batches [3] for T b 700°C were of the order 10 − 6 m 2 s − 1 . It is worth mentioning that already in the late 1950s, Jack and Jacquest [43] measured the thermal diffusivity of batches at temperatures ≤700°C, obtaining 2.6 × 10 − 7 m 2 s − 1 .…”

“…1-3 as functions of temperature (A0 data were reported in a previous paper [3] and are reproduced here for completeness). The lines in the figures are an arctan approximation function fitted to data as described in the following section.…”

“…As the short literature review below attempts to communicate, batch melting reactions have been studied over the past 100 years, partly driven by the desire to understand them and partly by the glassmakers' need to mitigate problems with glass melting and to increase the rate of melting in glass-melting furnaces [1]. As in our previous studies [2][3][4][5], we used batches formulated for a high-alumina simulated nuclear waste. The silica source was quartz with particles that varied from 5 to 195 μm in size.…”

Conversion of batch to molten glass, I: Volume expansion

“…As we stressed in previous papers [4][5][6][7], the impact of primary foam on the batch melting process is not entirely clear, though it appears to have a generally negative effect. While primary foam does help homogenize the melt and assists in the dissolution of residual solids, batches that strongly foam have been shown to melt slower than batches producing limited foam [8].…”

“…As in the previous studies [4][5][6][7][8], our main concern is to gain knowledge of how to influence batch expansion by changing the batch makeup without changing the glass composition. In the case of waste glass, these changes are limited to adjusting the glass-forming and modifying additives because the waste is processed as received.…”