A new method to overcome difficulties of measurements for energy and exergy auditing of municipal solid Waste-to-Energy plants
2022
Hejrandoost, Masoud Lotfi | Fazelpour, Farivar | Saraei, Alireza
The current study develops the energy auditing method presented in ASME PTC 4.3 and introduces a novel and applicable method to exergy audit the waste-to-energy power plants. The presented method does not require the waste’s chemical analysis, and the heating value of the solid waste (fuel) is calculated using energy and mass balances around several control volumes within the system instead. Moreover, to calculate the chemical exergy of the fuel, based on its HHV, a set of equations are tested, and the best one is chosen that yields the most negligible error. The fuel mass flow is estimated indirectly using an innovated method. The energy and exergy efficiencies are estimated by the indirect method. The different sources of exergetic inefficiency are presented that are defined as nine exergy losses and two exergy destruction elements. Losses are mainly due to the exiting exhaust gas from the stack, exiting residue and leachate, unburnt carbon, and casing heat loss. Irreversibilitties in the gasifier, combustion chamber, and the HRSG is defined as the exergy destructions that contribute to efficiency reduction. Finally, the developed method is applied to the actual data acquired from an existing power plant in Iran. According to the results of the exergy audit, the exergy efficiency of the considered plant is 25.3%. Here, the exergy destruction in the gasifier and combustion chamber and the exergy loss due to the exiting exhaust gas have the most remarkable impact on reducing the efficiency of the system.
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