05 07 2023 TEM Problems solutions

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Department of Energy Politecnico di Milano Author Pag.1 of 14 Date 21/07/2023 Exam – Advanced Thermodynamic and Thermoeconomics 05-07-2023 Exercise 1. Let’s consider an innovative biomass -fed steam cycle. The thermal energy required by boiler of the steam cycle 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 ( Q̇boiler) at 2500 K. Flue gases (stream 3) are then treated before being discharged after 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 Q̇cond to the environment. Consider that the water coming from the turbine enters into the condenser at 55°C and exits at 50°C. The overall work produced by the steam cycle is Ẇnet. 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 110 2 Ambient air 0 3 Treated flue gases 15 4 Treatment heat 20 Quantity Exergy [MW] Q̇boiler 70.5 Q̇cond 3.4 Ẇnet Net power 50 Table 2 Unit cost of feedstock [€/MWh] 15 Z – PT (Investment, O&M) [€/h] 30 Z – CC (Investment, O&M) [€/h] 120 Z – SC (Investment, O&M) [€/h] 800 Z – FGT (Investment, O&M) [€/h] 250 FIGURE 1. PLANT CONFIGURATION pre-treatment combustion chamber Steam cycle 0 3 1 4 2 Department of Energy Politecnico…