OCR Text |
Show 0.30 I 0.211 I 0.20 0.111 0.10 . ~ 0.011 0.00 0 20 18 - • BAR MILL CONTINUOUS FURNAC. TOTAL SPECIFIC OXYGEN CONSUMPTION o 40 eo eo 100 TOH8/HOUfI 120 L£GENO 0 0 0 GROUP 1 '" '" '" GROUP 2 ••• GROUP 3 O/lOUPl .. _3/11 .. 31211 OIIOUP 2 .. _ 4/01 TO B'17 _318_I/20T07101 140 Fig. 5 - Specific oxygen consumption for three periods of oxygen system operation Table 2 - Fuel savings results RESULTS OF FURNACE OPERATION WITH AIR AND uA" BURNER SYSTEMS U.S. STEEL - 18·2 BAR MILL CONTINUOUS FURNACE GARY WORKS -Ai-r -Ox-yge-n Overall Furnace: Specific Fuel Consumption (MMBTU/Ton) Fuel Savings (MMBTU/Ton) (%) For Zones Converted: Specific Fuel Consumption (MMBTU/Ton) Fuel Savings (MMBTU/Ton) (%) Oxygen Consumption (Tons/Ton Steel) 18 - II CONTINUOUS FURNAC. AVERAGE OXYGEN CONSUMPTION 3.00 2.17 0.83· 28 1.59 0.76 0.83 52 0.062 0'13-r-----------------------, 0.11 0.11 0.1 CUI1 .3"1 '''1 3m 4/01 4/118 4111 4/22 4121 1"3 II» 1121 I/OI lItO 1"7 1/24 _M Fig. 6 - Average specific oxygen consumption 263 Improvements were also made in the furnace light-up practice which helped reduce the oxygen consumption. Figure 6 shows the average specific oxygen consumption for the 15 week test period. The oxygen consumption for both the rolling period and the light-up period was reduced substantially from the beginning period to the last few weeks. As mentioned previously, one of the most important parameters in oxygen conversion is the drop in flue gas temperature due to the lower volume of flue gases. Though the flue gas temperature was measured, it was still difficult to determine precisely what this drop in flue gas temperature may have been. However, based on the overall fuel savings, it is estimated that the flue gas temperature was about 300 OF less than for the air system at similar operating conditions. The final results are in good agreement with our initial predictions. ZONE AND FLUE GAS TEMPERATURE MEASUREMENTS Thermocouples were located in the roof throughout the Preheat and No. 1 Heat zones in order to monitor temperature uniformity. Temperature uniformity is most critical at high production rates simply because there is less residence time for the steel to even out once it reaches the hearth area. Therefore, two cases will be examined where the production rate was at the maximum of 200 tons/hr for at least two hours. In the following two figures, three thermocouple readings are plotted vs. time. The three thermocouples are in a row spanning the width of the furnace located towards the end of the No. 1 Heat zone before entering the No. 2 Heat zone. Figure 7 presents data from the oxygen system and Figure 8 is a case from the air data before the oxygen conversion. The periods to focus on are from around 11 :00 to 16 :00 in Figure 7 and from 11 :00 to 13:00 in Figure 8, where the production rates were around 200 tons/hr. These figures show that the temperature was relatively more uniform across the width of the furnace with oxygen in the two zones as compared to air. It is difficult to analyze temperature uniformity because the transient nature of the operation makes it hard to find two cases that operate under similar conditions in order to compare them. However, in general, temperature uniformity was not a problem with the oxygen system. Both surface quality and production rate were not adversely affected by the oxygen system. The reasons it is difficult to analyze temperature 'uniformity are the same reasons that make it difficult to analyze differences in flue gas temperature between air and oxygen. However, since these two cases seem to be roughly similar, they can serve as a basis for comparison. |