02 04 07 2022 TEM Exercises solutions

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Department of Energy Politecnico di Milano Author Pag.1 of 15 Date 12/07/2022 Milan, 29th June 2022 Exam – Thermoeconomics and Energy Modelling 04-07-2022 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 boiler) 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 cond to the environment. Consider that the water coming from the turbine enters the condenser at 44°C and exits at 42°C. The overall work produced by the steam cycle is Ẇ net. Consider that T 0 and P0 are respectively: 298 K and 1 atm. Abbreviations: PT – pre-treatment; CC – combustion chamber; FGT – flue gases treatment; SC – steam cycle. With reference to the data provided, it is required to: 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 boiler 80 Q̇ cond 35 Ẇ net 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…