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Show model furnace since this is a common fuing configuration, and since the model flat glass furnace is of the side port design. The container glass model furnace uses regenerators and produces 250 ton per day of glass at a furnace fuing rate of 4.2 million Btu per ton of glass melted. In addition to fuing natural gas, approximately 1750 kW of electric boosting is used. Over the cycle, the average air preheat temperature is 21 OO°F, and the average exhaust gas temperature at the exhausting port is 2700°F. NOx emissions are 7 lb N02 per ton of melted glass or 1,287 ppm NO (dry, 3 percent 02). Gas Reburning Evaluation Methodology To estimate gas reburning performance on the model furnaces, a methodology consisting of the following steps was followed: (1) critical parameters needed to optimize reburning perfonnance on glass furnaces were identified, (2) conceptual reburning system designs were developed for the model furnaces, (2) heat transfer and mass balances were calculated to establish overall gas and air temperatures throughout the furnace, and (3) the temperature predictions and a reburning process kinetic model were u 'd to estimate the potential reductions in NOx emissions achievable with gas reburning. Reburning Process For application to glass furnaces, the overall reburning process can be divided conceptually into three lones as shown in Figure 4: • Primary Zone: In this lone, fuel and air are fired through the existing burners on the furnace at normal or slightly reduced primary fuel stoichiometry. The level of NO x exiting the lone is the input to the reburning process. • Reburning Zone: The reburning fuel is injected downstream of the primary lone to create a fuel rich, NOx reduction lone. NOx from the primary lone reacts with hydrocarbon fragments fonned during oxidation of the reburning fuel and is reduced to molecular nitrogen. • Burnout Zone: In this fmal lone, air is added to produce overall fuel lean conditions and oxidize carbon monoxide and any remaining fuel fragments exiting the reburning lone. Extensi ve bench and pilot scale research programs have been conducted by EER under funding from U.S. Environmental Protection Agency, the Gas Research Institute, and the U.S. Department of Energy. These studies have quantified the impact of process parameters on reburning effectiveness and provided scaling methodologies. Although a wide range of proces~ pararr.etcrs influence overall NOx reductions and must be specified in a reburning application, fortunatel}, not all of the parameters are of fll"St order importance. The reburning process is primarily controlled by the stoichiometric ratios of the primary, reburning, and burnout lones (SR 1, SR2. and SR 3). reburning lone fuel mixing, temperature and initial NOx level. Long lone residence times. hot combustion gases, and high initial NOx all work to enhance the NOx reduction achievable with gas reburning. These characteristics are well matched in glass furnaces. 4 |