| 摘要 |
A feedwater heater (14) in a heat recovery steam generator (A,B) lies within a flow of hot exhaust gas. The feedwater heater (14) converts subcooled feedwater into saturated feedwater water, the temperature of which is only lightly above the acid dew point temperature of the exhaust gas so that corrosive acids do not condense on coils (18) of the feedwater heater (14). Yet the temperature of the saturated feedwater lies significantly below the temperature of the exhaust gas at the coils (18), so that the coils (18) operate efficiently and require minimal surface area. Pumps (26, 28, 30) elevate the pressure of the saturated feedwater and direct it into an economizer (64, 90) where, owing to the increase in pressure, the water is again subcooled. The economizer (64, 90) elevates the temperature still further and delivers the higher pressure feedwater to evaporators (34, 70, 78) that convert it into saturated steam that flows on to the superheaters (50, 78, 84). Higher pressure pegging stem admitted to the feedwater heater (14) controls the pressure—and temperature—of saturated steam and water in the feedwater heater (14). |
