Modeling and thermodynamic analysis of Municipal Solid Waste Dryer: A parametric study

Abstract

Due to the landfill leachate and the lack of drainage beds for collecting and directing leachate, especially in developing countries, the need to study municipal solid waste (MSW) dryers is of particular importance. According to the technical literature, so far no comprehensive study has been performed on MSW dryers considering with the actual components of the waste and the moisture content above 40%. Here a comprehensive study for wet MSW dryers consists of three different parts is performed. In the first part, a semi-theoretical mathematical model is developed to calculate the drying rate (internal) of wet MSW. For this purpose, with the laboratory results in the technical literature and Statistica software, a suitable mathematical model for drying MSW is validated and determined. Then, the external drying rate is determined according to the type of dryer selected and after its validation; it is compared with the internal drying rate. In the second and third parts, after validation of EES developed code, energy and exergy analysis are reviewed and finally parametric study is performed to investigate the effects of different parameters on energy and exergy efficiencies of unsorted wet MSW drying process. The results show that the best model for drying the unsorted MSW is the logarithmic model with a corresponding R^2 of 0.999. The internal and external evaporation rates are 0.157 and 0.165 kg/s and it is seen these two rates are well matched together and differ by only 5%. The energy efficiency and exergy efficiency of the dryer are 13.92% and 2.91%, respectively. According to the parametric study, the inlet air temperature and the temperature of inlet MSW have the greatest effect on energy efficiency, respectively. Inlet air conditions such as absolute humidity of inlet air and atmosphere pressure have the greatest effect on the exergy efficiency of MSW drying.