Advanced exergy analysis and environmental assesment of the steam cycle of an an incineration system of municipal solid waste with energy recovery

This work presents an advanced exergy and environmental analysis of a steam cycle of a municipal solid waste incineration plant, with energy recovery for electricity generation; employing MSW of the city of Santo Andre in Sao Paulo State, Brazil. Initially, a plant energy analysis is accomplished to determine some thermodynamic performance indicators, as well a conventional exergetic analysis is performed, to determine the magnitude of exergy destruction in each one of plant main components. To identify the potential for improvement in the incineration steam cycle, an advanced exergetic analysis was done, with exergy destruction divided into four categories: endogenous, exogenous, avoidable and unavoidable. With all this it was calculated that total plant exergy destruction can be reduced by 8.4%, through increments in efficiency in plant components taking into account best existing technologies and operating parameters that represent an avoidable total cost of $2'830,624 per year. Finally, a Life Cycle Analysis using the IMPACT Method 2002 + was carried out to determine environmental impacts of plant operation considering two cases: Reference Case (Case A) and the Improved One (Case B). Case B was divided in three comparative scenarios (B1, B2 and B3) which were considered to evaluate the environmental impact of plant operation and dislocation of primary energy. The results shows that reduction of avoidable exergy destruction in a steam generating cycle leads to an emission index reduction from 531 to -224 kg CO2eq/MWh, while a primary energy displacement about 3.69 kWh per unit of electric energy available was reached, using MSW as fuel in steam cycle.