Investigation of thermochemical conversion characteristics of refused derived fuel

Municipal solid waste (MSW) management is a critical issue in most countries where the population is fast growing, primitive collection system is still preferred and the landfill spaces are limited. In an effective management system, different waste management activities are harmonized in order to meet the requirements of environmental, economic and social parameters. Selecting and combining the most appropriate activities that ensure the protection of human health and the environment are also called as integrated solid waste management. A well designed integrated waste management system includes waste prevention, re-use, recycling, energy recovery and disposal.In this study refused derived fuel, which is the combustible fraction left after segragating recoverable fraction (glass, polypropylene, polyethylene, scrap metals etc.) from municipal solid waste,was used. Study was done in four stages. First stage was dedicated to characterize the refused derived fuel. Proximate analysis, ultimate analysis and calorific value were determined in this stage.In the second stage of the study, thermal analysis was done under inert atmosphere by using thermogravimetry (TG) and differential thermogravimetry method. To interpret the pyrolysis profile of RDF, thermal analysis was done on the main constituents of RDF, namely paper, polypropylene (PP), high density polyethylene (HDPE) and fiber. Thermal decomposition of RDF under inert atmosphere was coherent with the pyrolysis profiles of the RDF constituents. Thermal decomposition of RDF, apart from moisture removal at low temperature reagion (<110°C), occurred in three steps. Decomposition of cellulosic fraction occurred between 293-355°C. Plastic fraction of RDF was decomposed between 430-495°C where the maximum weight loss was observed at 470°C. The third step between the temperatures 634-696°C denoted CaCO3 decomposition.In the third stage of the study ignition temperature, burnout temperature, peak temperatures and total conversion rates were investigated by thermal analysis under oxidative atmosphere. Besides, the effects of mixing ratio of waste fibre with RDF on calorific value and combustion profile were investigated. The thermal decomposition of RDF and RDF-WF mixtures under oxidative atmosphere included devolatilization, char combustion and CaO and CO2 evolution as a result of calcination reaction.In the last stage of the study, ash content and ash forming elements were investigated. The RDF ash which was mainly comprised of CaO, SiO2 and Al2O3 had high concentrations of Cu, Zn and Ba.