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Show III. CONVENTIONAL AIR-FUEL BASED GLASS MELTING Before discussing the TEAM processes in detail, a brief description of conventional air-fuel based glass melting is provided as background and for comparison purposes. Conventional glass melters are direct fired with natural gas or oil and preheated air. The waste heat from the furnace preheats the combustion air via a regenerator. Figure 1 shows a traditional regenerative type glass furnace. Figure 2 depicts the process flow diagram for a 250 TPD conventional air-fuel based glass melting operation. The solid raw material constituents for glass manufacture are batch (sand, soda, lime, salt cake, etc.) and cullet (recycled glass). These are fed to the process at one end of the furnace. The batch must be very well mixed to produce good quality glass and is wetted with approximately 3% water by weight to reduce segregation. The combustion air is passed through a regenerator where it is preheated before entering the furnace through a number of ports. Natural gas is injected into the preheated air stream and combusts over a bath of batch, cullet and molten glass. The products of combustion exhaust from the furnace through ports on the opposite side of the furnace. As the flue gas passes through the regenerator, it heats the checker brick work in the regenerator. Every 10 to 30 minutes the furnace reverses and the combustion air is redirected through the regenerator which has been heated by the melter flue gas. Regenerators typically preheat combustion air to approximately 2,000°F, recovering roughly 60% of the heat available in the flue gas. To comply with environmental regulations, the melter flue gas also goes through a unit for NOx removal (e.g. THERMAL DeNOx) and an electrostatic precipitator for reduction of particulate emissions before being vented to the stack. Regenerators recover a substantial portion of the heat in the melter flue gas and improve the operating economics of glass manufacture. However, they are very expensive ($1.5 to 2 MM for the 250 TID glass plant considered here). De-commisioned regenerators pose a significant disposal problem as described earlier. Also, plugging of regenerators, hot spots, and maldistribution of the combustion air are all significant concerns. NOx and particulate reduction equipment, shown in Figure 2, are often required to comply with local environmental regulations. Adding this equipment dramatically increases glass manufacturing cost through added capital costs. Also, practicing THERMAL De NO technology in a regenerative process is complicated because t~e temperature window moves during the regenerative cycle. IV. TEAM PROCESSES All three Thermally Efficient Melter Alternate (TEAM) processes developed use oxy-fuel firing in the glass melter, followed by heat recovery from the flue gas to further improve overall economics and environmental compliance. The common design basis for the TEAM processes is presented below followed by a detailed description of each process. - 3 - |