Numerical Simulation Study Of The Drying Process Of MSW

Waste incineration is a effective processing method for waste endlessly, which can rapidly diminsh the volume and mass of waste and make waste innoxious. The drying of waste is important, because water in waste would reduce its caloric and buring efficiency. In this paper, the drying characteristics of waste is studied by numerical simulation, the results get from which can be used for further research on combustion model and can provide reference for the drying technology of waste.In this paper, heat and mass transfer inside the waste as well as between the waste and hot air is studied accroding to the similarity between waste and porous media. A mathematics model on the drying process of waste has been built in the base of volume-average theory , which is described by two state-variable: moisture content and temperature. Through discretization of governing equations and boundary condition equations using the alternating direction implicit method and the fully implicit method, numerical results of drying process are computed by Fortran language.In this paper, the drying of different types of waste in muffle and Circulating Fluidized Bed on different conditions is simulated by the drying model and computational procedures above, then we can get the characteristics of average moisture content, average temperature and drying rate and the distribution of moisture content and temperature inside waste. Comparing with the average moisture contents, it shows that the calculated results and the experimental results inosculate well, from which it can be concluded that the drying model is reasonable and can be used in engineering studies.The results showed that at beginning of the drying process, there is smaller moisture content difference between boundary and center. Then the difference becomes larger and the shape of the moisture content distribution sketch map becomes gibbose. At last, the difference is smaller and the shape of the map becomes plane. Drying process would be affect in varying degrees by heat and mass transfer coefficients at the surface, volume of materials, initial moisture content, drying temperature and air relative humidity.