Effects of hydrothermal treatment on characteristics and combustion behaviors of municipal solid wastes

The conversion of municipal solid wastes (MSW) to energy for co-combustion with coal may be a viable MSW disposal solution from the view point of suppression of the environmental pollution as well as reduction of coal consumption. This paper describes the application of innovative hydrothermal technology on different kinds of MSW to produce powder-like solid products appropriate for co-combustion with coal. In this work, three kinds of surrogated MSW (Japanese MSW, Indian MSW and Chinese MSW) different in composition and characteristics were subjected to the hydrothermal treatment (HT) at 220 °C and 2.4 MPa for 30 min. After the HT, the combustion behaviors of the samples were determined by investigating the sample weight loss (TG) and the rate of weight loss (DTG) through the thermogravimetric analysis (TGA). In addition, the effects of the HT on the characteristics and the combustion behaviors of the MSW were explored by comparing with three standard samples such as rice, cellulose and polypropylene (PP) both before and after the HT. The results obtained in this study can be drawn as the following: The HT is capable for converting MSW into uniform powder samples with low moisture content, regular shapes and high bulk density. During the HT, the hydrolysis reaction leads to the loss in volatile matter and the carbonization results in the gain in fixed carbon. The higher heating values of the three kinds of MSW after the HT are enhanced by 1.01–1.41 times (energy content per weight) and 6.39–9.00 times (energy content per volume). The combustion behaviors of the MSW in this study before the HT were dominated by the substance major in weight whereas for the ones after the HT, the intrinsic characteristics of the MSW can play an important role in determining the combustion behaviors.