To reduce energy consumption of an oxy-fired glass furnace, energy loss via the flue gas and through the furnace walls should be minimized since they account for approximately 40 % of the energy usage. One way to minimize flue gas energy loss is to pre-heat the raw batch materials and/or cullet. Energy analysis was conducted to evaluate the maximum amount of energy recoverable and that required for the pre-heating. The maximum pre-heating temperature was calculated under conditions of constant and reduced rate of natural gas usage. Since the flue gas temperature from an oxy-fired furnace is on the order of 1350 °C, the maximum temperature for batch pre-heating that could be potentially employed was above 500 °C. However, handling loose batch at such high temperatures is likely to be physically difficult to accomplish reliably. On the other hand, batch in an agglomerated form, such as granules, may be pre-heated easily. Analysis of the heat transfer from flue gas to a single granule was investigated first through computational fluid dynamics (CFD) modeling. Parameters studied included the average diameter and thermal conductivity of the granule, the inlet flue gas temperature, and the flue gas velocity and composition. The data was used to evaluate the time needed to preheat a single representative batch granule to a given target temperature under various heating conditions. In addition, the time-dependent temperature and velocity distributions for the modeled geometry were determined. The results show that granule diameter and gas velocity both have a significant impact on the rate of granule heating.
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