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Show Batch Annealing Furnace Field Test An intensive educational showcase of eleven technologies that save energy, reduce pollution, and raise productivity was recently organized by the U S Department of Energy and Bethlehem Steel, Burns Harbor Division in Indiana. Oscillating combustion was selected as one such technology and it was demonstrated on batch annealing furnace #8 (see Figure 1 1) in their cold sheet mill during the showcase on April 30, 1998. The furnace is used to anneal coils of steel sheet after they have been rolled to the desired thickness. This process restores the formability and malleability of the steel to make it easier to stamp into shapes. The plant has several batch annealing furnaces, and they move from base to base. Figure 11. F O U R - S T A C K B A T C H A N N E A L I NG F U R N A C E W I T H T E N B U R N E RS Subsequent to the showcase, a series of tests was undertaken to determine the thermal and emissions performance of the furnace when operating with oscillating combustion as compared with normal steady operation. Tin. batch annealing furnace has ten, flat flame-type burners. Each burner is retrofitted with an oscillating combustion valve package using the CeramPhysics SSP valve. The valve package has two parallel legs-one with the oscillating valve and the other with a limiting orifice that is set to match the average flow of the oscillating valve. Isolation valves allow selection of one leg or the other and also allow for the removal of the oscillating valve during furnace operation for inspection, adjustment, or replacement. The SSP valves are also insulated to protect them from thermal radiation from a hot neighboring stack when the furnace covering the stack is moved to a new base. Five CeramPhysics oscillating valve controllers are mounted on the front of the furnace near the main furnace controls. Each controller operates two valves that oppose each other from opposite sides of the furnace. Burners on opposite sides of the furnace are oscillated out of phase with each other, while burners adjacent to each other are oscillated either out of phase or in phase with each other (see Figure 12). Due to the higher pressure needed to overcome the pressure drop of the oscillating valves and to provide the higher gas flow during the high-flow half of the oscillating cycle, the flow ratiu control regulator on the furnace was replaced with one that could deliver the natural gas to the oscillating valves at the requisite pressure. Instrumentation was installed to monitor furnace emissions (NOx, C O . T H C , CO: , and 02) and exhaust temperatures and continuously record the natural gas consumption. Data was collected for the most common annealing cycles used at the site (see Table 5). Fuel use and N O x emission data were analyzed for complete pairs of cycles-one using steady flow and one using oscillating combustion-for each date reported in the table. These were then compared to calculate the fuel savings and N O x reductions. Each pair of cycle used the same steel load. (afrc98pdoc) 8 |
