Steam is supplied to a two-stage turbine at 40 bar and 500 °C. In the first stage the steam expands isentropically to 3.0 bar at which pressure 2500 kg/h of steam is extracted for process work. The remainder is reheated to 500 °C and then expanded isentropically to 0.06 bar. The by-product power from the plant is required to be 6000 kW. Assume that the process condensate returns at the saturation temperature to mix adiabatically with the condensate from the condenser. It is required to improve the efficiency by employing regenerative feed heating by taking off the necessary bleed steam at the same point as the process steam. The process steam is not returned to the boiler, but make-up water at 15 °C is supplied. The bleed steam is mixed with the condensate and make-up water at 3.0 bar such that the resultant water is at the saturation temperature corresponding to 3.0 bar. Calculate: (i) the steam supply necessary to meet the same power and process requirements; (ii) the amount of bleed steam; (iii) the heat supplied in kW. Neglect feed-pump terms. ANSWERS: (16 480 kg/h; 2660 kg/h; 15 460 kW)
Steam is supplied to a two-stage turbine at 40 bar and 500 °C. In the first stage the steam expands isentropically to 3.0 bar at which pressure 2500 kg/h of steam is extracted for process work. The remainder is reheated to 500 °C and then expanded isentropically to 0.06 bar. The by-product power from the plant is required to be 6000 kW. Assume that the process condensate returns at the saturation temperature to mix adiabatically with the condensate from the condenser. It is required to improve the efficiency by employing regenerative feed heating by taking off the necessary bleed steam at the same point as the process steam. The process steam is not returned to the boiler, but make-up water at 15 °C is supplied. The bleed steam is mixed with the condensate and make-up water at 3.0 bar such that the resultant water is at the saturation temperature corresponding to 3.0 bar. Calculate: (i) the steam supply necessary to meet the same power and process requirements; (ii) the amount of bleed steam; (iii) the heat supplied in kW. Neglect feed-pump terms.
ANSWERS: (16 480 kg/h; 2660 kg/h; 15 460 kW)
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