Exam 2020 06 15 Solutions

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Department of Energy Politecnico di Milano Author Pag.1 of 12 Date 23/06/2020 Milan, 06th June 2020 Exam – Advanced Thermodynamic and Thermoeconomics 15-06-2020 Exercise 1. Let’s consider an innovative biomass-fed steam cycle. The thermal energy required by the steam cycle to generate the steam is provided by a dedicated combustion chamber supplied by biomass feedstock. Biomass is pre-treated (PT) by reducing water content and increasing the temperature thanks to a contribution coming from the combustion chamber (stream 4) at steady conditions. The combustion chamber (CC) takes in input the pre-treated feedstock (stream 1), ambient air (stream 2) and produces useful heat for the steam cycle (Q̇ ୠ୭୧୪ୣ୰) at 2000 K. Flue gases (stream 3) are then treated before being given off by means of a flue gases treatment (FGT) system which investment costs are reported in Table 2. The steam cycle gets in input the heat required to vaporize water. The condenser of the steam cycle discharges Q̇ ୡ୭୬ୢ to the environment. Consider that the water coming from the turbine enters into the condenser at 44°C and exits at 42°C. The overall work produced by the steam cycle is Ẇ ୬ୣ୲. Consider that T0 and P0 are respectively: 298 K and 1 atm. Abbreviations: PT – pre-treatment; CC – combustion chamber; FGT – flue gases treatment; SC – steam cycle. Table 1 State Exergy [MW] 0 Input feedstock 100 1 Treated feedstock 105 2 Ambient air 0 3 Treated flue gases 18 4 Treatment heat 15 Quantity Energy [MW] Q̇ ୠ୭୧୪ୣ୰ 80 Q̇ ୡ୭୬ୢ 40 Ẇ ୬ୣ୲ Net power 45 Table 2 Unit cost of feedstock [€/MWh] 20 Z – PT (Investment, O&M) [€/h] 50 Z – CC (Investment, O&M) [€/h] 150 Z – SC (Investment, O&M) [€/h] 1000 Z – FGT (Investment, O&M) [€/h] 350 FIGURE 1. PLANT CONFIGURATION pre-treatmentcombustion chamberSteam cycle03142…