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Show produced less O & M costs for G R and oxygen (cost per ton of steel produced) The economics are based on the following assumptions: • The material and heat balances previously discussed Capital costs of $340,000 and $250,000 for GR and OEA respectively • Cost of oxygen of $30/ton • Operating hours of 8,000/yr Fuel cost of $2/MMbtu • Capital recovery factor identical to the EPA ACT (1994) document, 7% interest and 15 yr life • A twenty percent increase in furnace productivity • Finished steel at $0.22/lb, and a 1.2, 2.5 and 5 % revenue enhancement from production increase The economics of the three concepts relative to base line performance are detailed in Table 2. G R capital costs have been annualized, 37,330 $/yr, with a capital recovery factor based on the E P A A C T (1994) assumptions. Fuel efficiency impacts could vary between 0 and $73,600/yr, depending on G R heat release/absorption. The cost-effectiveness of G R is calculated on the basis of annualized cost/ton N O x removed, and evaluated parametrically as a function of its impact on furnace efficiency shown in Figure 14. The modelling results currently suggest slight to some decrease in furnace efficiencies (between 1.22 to 1.25 Btu/ton), resulting in 1100 to 1900 $/ton N O 2 reduced, respectively. G R and LNB's could be used in combination to achieve control levels approaching 7 5 % reduction, similar to selective catalytic reduction. The importance of recovering the reburn fuel heating value suggests that this should be one of the focuses of the development plan. Specifically, the reburn fuel jets need to be placed well upstream of the exit to the last heating zone and the O F A jets should be close coupled, e.g., providing about 400 m s of mixing/reaction time. For the base case 9 0 % of the flue gas flow is at a velocity of about 20 fps at the injection point, indicating that the injectors should be spaced 8 ft apart. Because of the substantially lower flows when oxygen enrichment is used, the distance could be reduced about 3 0 % or to about 5 ft. Thus there is sufficient time/temperature to recover a significant amout of the reburn fuel as useful steel heating. OEA without and with reburn is directed at debottlenecking a production line and are of primary interest in increasing revenues due to production increases. The annualized cost per ton of steel increases because of the cost of O 2 (about 0.48 $/ton) and capital, even though there is an off setting fuel savings of about 0.3 $/ton. The potential value (2.5 to 5 % incremental value) of a 2 0 % production increase (23 T P H ) is about $10 to 20/ton for finished steel priced at $440/ton. Thus, there is some considerable advantage to debottlenecking with net savings of over $600,000 on $ 590,000 of capital, an excellent return of the investment. Figure 15 shows the cost of implementing oxygen enrichment with and without reburning for different levels of revenue increase. The importance of maximizing the flame radiation to minimize O2 consumption is suggested and is the other major focus of the development plan. 11 |
