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Hi, Thanks for the reply. Yes, I realized that I made a mistake calculating the first stage's steam quality. I did calculate the second stage and got a steam quality of 89% which satisfies the problem statement. About part ©, should I divide the amount of sulfur (0.46%) by the molar mass of the sulfur (32.06) or should I directly multiply the amount of coal by 0.46?

A coal-fired steam power plant operates on the ideal Rankine cycle. Feedwater from the condenser at P1 = 10 kPa is pumped to the boiler at P2 = P3 = 20 MPa, where it is superheated and exits the boiler at T3 = 550 °C. The moisture content in the turbine is not to exceed 12% (i.e. steam quality is to be maintained above x = 0.88 throughout the turbine). Up to two reheat stages can be added to the steam cycle to satisfy this requirement. If needed, one stage can be added to reheat the steam to T5 = 525 °C at P4 = P5 = 10 MPa. If more reheating is required, a second stage can be added to reheat the steam to T7 = 500 °C at P6 = P7 = 2.5 MPa. A process diagram for single reheat is shown schematically below. (a). How many reheat stages are required for this power plant (no reheat, single reheat, or double reheat)? Provide calculations in support of your answer. (b).What is the thermal efficiency η th of the power cycle? ©. Determine the annual emission of sulfur dioxide, mSO2, in metric tons, from this power plant, if the net generating capacity of the plant is 600 MW, and the boiler is 88% efficient in transferring combustion heat into the feedwater superheat and steam reheat stages. The boiler burns, to completion, Power River Basin coal that has a heating value of 22,800 kJ/kg and contains 0.46 wt% sulfur. Assume that all of the sulfur content of the coal is emitted as SO2 in the combustion flue gas, and that the coal-burning plant has a capacity factor of 0.85; i.e. the boiler is operational for 85% of the hours in one calendar year. (1 metric ton = 1000 kg) --------------------------------------------------------------------------------------------------- I completed the first 2 parts of the problem andI found out that one reheating stage is enough to active a steam quality morethan 88.2%. I also calculated the thermal efficiency of 38/6% of this powerplant. My question is about part 3. How can I approach? thanks

A gas turbine power plant operates on the regenerative Brayton cycle as shown in the figure. Compression occurs in two stages, with interstage cooling, and expansion in the turbine likewise occurs in two stages, with interstage reheating. The cycle operates between the pressure limits of P1 = P9 = P10 = 100 kPa and P4 = P5 = P6 = 1200 kPa. Interstage cooling/heating occur at the thermodynamic optimum P2 = P3 = P7 = P8 = 346.4 kPa (i.e. the geometric mean of the intake air and combustor pressures). Air enters each compression stage at T1 = T3 = 300 K. Combustion gases enter the first and second stages of the turbine at T6 = 1400 K and T8 = 1300 K respectively. The compressor and the turbine both have an isentropic efficiency of 80%. The regenerator has an effectiveness of 75%; i.e. εregen = (h9 – h10)/(h9 – h4) = 0.75. Assuming that the gas power cycle can be modeled using the air standard assumptions, with variable (i.e. temperature-dependent) specific heats for air, and an air mass flow rate m = 90 kg/s, determine the following: (a). The net work output Wnet (MW) for the cycle. (b). The back work ratio rbw; i.e. the fraction of the turbine work output that is used to drive the compressor. ©. The water supply rate, mW (kg/s), needed for interstage cooling in the compressor, if liquid water at ambient temperature (300 K) is sprayed into the air between the two compressor stages to provide evaporative cooling. (d). The second-law efficiency η II = η th /η max for this gas turbine cycle; i.e. the ratio of the actual thermal efficiency to the maximum possible (Carnot) efficiency. ------------------------------------------------ Parts a & b are done. I have done all theanalysis across the power plant and have found all the temperatures in eachstage (1-10). I have two questions: 1- It mentions in problem statement that the airhas variable specific heat, does it mean that I have to use different valuesfor the specific heat in each stage like compressor, coolant, etc. depending onthe temperature in that stage? 2- For part C, how can I find the water supplyrate in interstage cooling? Thank you