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Raising Steam Superheat In general however from actual plant experiences, it usually does fairly closely match the limiting flow for the lower (original) steam superheat condition. For abbreviation of Figure 3, the details of the "blocks" of back-pressure and vacuum exhaust turbines shown in Figure 1 are not given in the Revised cases (Figures 2, and 3). The efficiencies of these respective turbines were maintained constant for all revised calculation cases. Higher Steam Superheat Advantages It has long been understood by most companies that increased steam superheat is key to minimizing energy consumption of the steam system and plant, improves capacity of the turbines and reduces load on boiler feed-water pumping. In this example illustrated in Figure 3, the boiler feed-water pumping load is reduced by 2.2% for 30 Deg F higher 1500 psi steam superheat. Energy savings at 82% (HHV) furnace efficiency is 13.3 MM Btu/Hr, HHV, equivalent to $335,000 per year savings, based on $3.00/MM Btu (HHV) energy cost. The economic benefits of improving steam superheat for this example can be illustrated in the following table of economics. |
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