Heat production in municipal and industrial waste as revealed by isothermal microcalorimetry

Self-ignited fires at municipal solid waste (MSW) storage sites are relatively common. The minimization of the phenomenon of self-heating in the waste can reduce the risks for smouldering combustion. The purpose of this work was to develop a method that can be used to measure and characterize the heat production in MSW. The method is based on isothermal heat conduction microcalorimetry (IMC). The heat production in MSW was determined based on sampling from two sites in two different geographical locations in Sweden. Both the original waste and milled/homogenised waste were tested. The heat production was measured at different temperatures together with gas analysis using micro-gas chromatography. The activity in the waste, in terms of its heat flow, increased when the temperature increased up to 60 °C and decreased at higher temperatures, e.g., 70 and 80 °C. The consumption of oxygen and the production of carbon dioxide, together with the heat production, indicated that aerobic metabolism was responsible for the heat production. This is further strengthened by the marginal heat production observed for ultraviolet treated waste. The results showed that IMC is a valuable tool for characterising the self-heating in municipal and industrial waste.

Fuel Gas Production From Self-Sustaining Smouldering Combustion of Lignocellulosic Waste

Smouldering combustion has shown to be an effective application for soil remediation and as a waste treatment method for solids with high moisture content. The experimental set-up of smouldering combustion reactors is similar to autothermal fixed-bed gasification, updraft reactor configuration. In this study, smouldering experiments were conducted using lignocellulosic agricultural waste. The moisture content of lignocellulosic biomass was varied between 10 % to 50 %. Air flux was varied between 1.8 and 7.4 cm/s. Experiments were also conducted with varying oxygen concentration in the airflow (3.6 – 21 %), addition of sand (4 and 8 g/g) and other lignocellulosic material (wood pellets, and residual berry plant). Fuel gas with maximum H2, CO, CH4, CO2 concentrations of 7.7, 32.6, 2.3, and 57.4 % (N2 free) respectively were obtained with 10 % moisture content and 7.4 cm/s air flux. The smouldering yielded 1.24 Nm3/kgfeed_dry of gas with calorific value of 1.82 MJ/Nm3 (HHV).