Consider a thermal power plant with reheating and cogeneration. It produces 5 MW of power and 4 MW of process heat. The steam enters the high-pressure turbine at 8 MPa and 480 °C and expands to 1.2 MPa, to be reheated to 450 C. Subsequently, at a pressure of 0.8 MPa, a fraction of 0.152 of steam is extracted, which is sent as process heat. Then, at a pressure of 0.25 MPa, another extraction is made to preheat feed water in a closed heater, whose condensate (saturated liquid) expands and is sent to the condenser, whose pressure is 15 kPa, from which saturated liquid comes out. Subsequently, it is pumped to a mixer where it joins with the subcooled liquid at 120 C and 0.8 MPa that comes from the industrial process, to be later pumped to the steam generator. Consider the isentropic efficiencies of the turbines of 88% and of the pumps of 82%. In the steam generator and in the superheater, natural gas is used, whose simplified composition is 83.2% CH4, 11% C2H6, 0.8% S, 3.6% N2 and 1.4% CO2 by volume, and is fed at a At a temperature of 17C, it burns completely with 10% excess air entering at 17C, 45% relative humidity, and 86 kPa pressure. The combustion gas contains SO2, CO2, H2O, O2 and N2, and is fed to the steam generator at a temperature of 923 K, with an efficiency of use of thermal power of 90%. Develop the following: a) Draw a sketch of the T-s diagram of the cycle. b) Thermodynamically characterize the cycle, quantifying the properties for each current: T [C], P [bar], h [kJ/kg], s [kJ/kg(K)], [kJ/kg) and phase. Consider T0= 300 K and Po= 100 ka c) Thermal performance. d) Exergetic efficiency.
Consider a thermal power plant with reheating and cogeneration. It produces 5 MW of power and 4 MW of process heat. The steam enters the high-pressure turbine at 8 MPa and 480 °C and expands to 1.2 MPa, to be reheated to 450 C. Subsequently, at a pressure of 0.8 MPa, a fraction of 0.152 of steam is extracted, which is sent as process heat. Then, at a pressure of 0.25 MPa, another extraction is made to preheat feed water in a closed heater, whose condensate (saturated liquid) expands and is sent to the condenser, whose pressure is 15 kPa, from which saturated liquid comes out. Subsequently, it is pumped to a mixer where it joins with the subcooled liquid at 120 C and 0.8 MPa that comes from the industrial process, to be later pumped to the steam generator. Consider the isentropic efficiencies of the turbines of 88% and of the pumps of 82%. In the steam generator and in the superheater, natural gas is used, whose simplified composition is 83.2% CH4, 11% C2H6, 0.8% S, 3.6% N2 and 1.4% CO2 by volume, and is fed at a At a temperature of 17C, it burns completely with 10% excess air entering at 17C, 45% relative humidity, and 86 kPa pressure. The combustion gas contains SO2, CO2, H2O, O2 and N2, and is fed to the steam generator at a temperature of 923 K, with an efficiency of use of thermal power of 90%.
Develop the following:
a) Draw a sketch of the T-s diagram of the cycle.
b)
c) Thermal performance.
d) Exergetic efficiency.
e) The exergy destroyed in the entire cogeneration cycle as a block.
f) The composition of the exhaust gases.
g) The volumetric flow and mass flow of natural gas that is required to satisfy the heat needs in the steam generator and in the superheater, in [m3/min].
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