Investigation of fuel values and combustion characteristics of RDF samples

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Environmental Engineering, Turkey

Approval Date: 2014

Thesis Language: English


Principal Supervisor (For Co-Supervisor Theses): Faika Dilek Sanin

Co-Supervisor: Aysel Atimtay


Municipal solid waste (MSW) is an unavoidable by-product of human activities. The generation of MSW tends to increase with the growing population and the economic development of the society. Landfilling is one of the most common disposal methods for MSW in the world. However, there are numerous disadvantages of landfills including the potential to create air, soil and water pollution. Also, many valuable resources are wasted when waste is landfilled. Furthermore, many countries have established rules to limit the amount of organic fraction (biodegradable) of wastes sent to landfill, and encourage establishing environmentally sustainable waste management strategies. In this sense, waste to energy strategies have come prominence because the strategies increase resource efficiency and replace fossil fuels with renewable energy resources (material and energy recovery instead of landfill disposal). Producing Refuse Derived Fuel (RDF) is one of the waste to energy strategies. RDF is an alternative fuel produced from energy-rich MSW materials diverted from landfills. This study aims to investigate the thermal characteristics and co-combustion efficiency of two RDF samples obtained from two municipal solid waste recovery facilities in Turkey as alternative fuels. On these samples, proximate and ultimate analyses are conducted in order to articulate the thermal characteristics of both RDF. Thermogravimetric analyses (TGA) are conducted to observe the combustion behavior of RDF samples, coal and petroleum coke samples. Also, elemental compositions of RDF samples’ ash are determined by XRF analysis. These samples are co-combusted in a lab-scale reactor in mixtures with coal and petroleum coke at certain percentages where co-combustion processes and efficiencies are investigated. The all analysis indicated that calorific values of RDF samples on dry basis are close to that of coal and a little lower compared to petroleum coke used in this study. However, when the RDF fraction in the mixture is higher than 10%, the CO concentration in the flue gas increases and so the combustion efficiency decreases crucially; furthermore, the combustion characteristics of the fuel mixtures changes from char combustion to volatile combustion. However, RDF addition to the fuel mixtures decreases the SO2 emission. No NOx profile was obtained in this study showing the effect of RDF addition. Also, when the RDF is combusted alone the slagging and fouling indices of its ash was found as higher than the limit values.