3. Consider a steam generator that burns biomass in 140% theoretical air. It contains a combustion chamber, and four heat exchangers i a drum/downcomer riser system that vapourizes the water, ii) a superheater, iii) a reheater, and iv) an air pre-heater. Because of the nature of biomass supply, the fuel composition may vary. When disassociated, the fuel contains 75-95% Carbon by mass with a heat of combustion of 32,770 kJ per kg of Carbon in the fuel (see Table A-25 in Moran et. al), and the remainder of the fuel is inert N2, which gets released upon burning Assume the following molecular weights C: 12 g/mol. O 16 g/mol, N: 14 g/mol a) If the combustion gasses exit the air-preheater at 450 k, determine the rate of heat transfer in kJ/s from the combustion gasses (combined for the four heat exchangers plus any losses), if the fuel mass flow rate is 32 kg/s, for the fuel that is 75% Carbon by mass. Assume the air enters the combustion chamber at 300 k Plot the rate of heat transfer out of the combustion gasses as a function of varying fuel Carbon content from 75-95% b) c) Carbon mass fraction relative cost per unit fuel A supplier will guarantee fuel composition based on cost. The fuel is more expensive if it is to have a higher carbon content, as in the table: 0.75 0.76 0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 1.05 1.1 1.12 1.13 1.1325 1.135 1.1375 1.14 1.1425 1.145 1.1475 1.148 1.149 1.15 1.16 1.18 1.2 Plot heating value per unit cost of fuel, and determine which carbon mass fraction is the most economical to use? d) The combustion gases take the path state 1 - downcomer/risers state 2- superheater-state 3-reheater-state 4 - air pre-heater 0.86 assuming no losses, determine the temperature at state 4, for the 75% Carbon case, if 60% of the heat is transferred to the downcomer/risers, 15% is transferred to the superheater 15% is transferred to the reheater, and 10% to the air pre-heater 0.88 0.89 0.9 0.92 0.93 0.94 0.95 1.22 1.24 Using the results from part d, determine the temperature of the fresh air exiting the air pre-heater if it enters at 300K. Up until this point, we have assumed that the combustion exhaust gas exiting the air pre-heater was 450K, and your calculations should show that it is hotter than that. In four or five sentences, discuss how this assumption affects your calculations and what could be done to improve the estimate e)