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Show EFFECT OF OPERATING PARAMETERS ON N O X PRODUCTION IN A FLAT GLASS FURNACE 2 eludes Carvalho (1983), Carvalho and Lockwood (1985), Kobayashi and Richter (1992), Webb (1997), and Carvalho et al. (1997). This study seeks to use the best available engineering tools to study N O x reduction techniques used and proposed for use in float glass furnaces. Such a computational study provides distinct advantages over prototype testing, since a typical rebuild of industrial float glass furnaces costs $50 - 80 million, and new furnaces are 2 - 3 times this amount. The different N O x reduction techniques studied here are compared on the basis of three figures of merit developed as part of a comprehensive program to explore the characteristics of such furnaces and optimize their operation. They are furnace i) fuel utilization efficiency, ii) combustion efficiency, Hi) heat flux uniformity on the melt surface, and iv) N O x production (in p p m and lb/ton of glass produced). Fuel utilization efficiency is the fraction of the fuel's heating value which is transferred to the glass melt, and is quantified here by determining that fraction as well as the exhaust gas temperature and average radiative flux absorbed by the glass melt for each simulation. The combustion efficiency relates to the conversion of carbon in the fuel to C 0 2 , and is evaluated here by the concentration of C O in the exhaust stream. Higher concentrations of C O in the exhaust indicate lower combustion efficiency in the furnace. A parameter has been devised to assess the heat transfer uniformity on the glass surface, and is defined here as Heat Flux Uniformity = \A{Cd-Cd)dA \A€addA (1) Values of the uniformity parameter greater than 0 reflect increasingly non-uniform heat flux delivered to the glass melt. While a value of 0 may not be the optimum for industrial melting scenarios, it nevertheless provides a measure of the non-uniformity of the flame radiation to the glass melt and can be used along with local heat flux information in a design optimization setting. The N O x production expressed in terms both of exhaust concentration (ppm) and generation rate (in lb/ton of glass produced as is the convention in the industry) provides a parameter for assessing the pollutant characteristics of the different furnace concepts explored. Port Centerline Furnace Inlet Wall 1 Inlet Entrance to Exhaust Port Glass Surface Centerline Between Portnecks Fuel Inlet Figure 2. Dlustration of port module used in most numerical simulations. |