Co-Firing of Refuse-Derived Fuel with Ekibastuz Coal in a Bubbling Fluidized Bed Reactor: Analysis of Emissions and Ash Characteristics

Converting municipal solid waste (MSW) into valuable feedstocks, such as refuse-derived fuel (RDF), is a sustainable method according to the concept of waste management hierarchy. A heterogeneous composition with a good calorific value and lower emissions allows RDF to be used for energy recovery purposes. We have earlier analyzed the generation and thermochemical characteristics of the MSW produced in Kazakhstan. This work aims to study the combustion characteristics in terms of emissions and ash composition to evaluate the possibility of RDF co-firing with Ekibastuz coal. In particular, RDF is blended with high ash bituminous coal (Ekibastuz coal) and co-fired in the laboratory scale bubbling fluidized bed reactor (BFB) at a bed temperature of 850 °C. The co-firing tests of RDF to coal samples were conducted under various proportions to analyze flue gas compositions. Experiments were carried in the presence of bed material (sand), and the fuel particles were fed in batch mode into the hot riser. The BFB reactor had a height of 760 mm and internal diameter of 48 mm. The gaseous products in the flue gas were analyzed by FTIR spectrometry (Gasmet Dx4000). Ash composition was examined by XRD, XRF, SEM, and PSD. The results showed that a high RDF content decreased SO₂ emissions to 28 ppm, while it negatively affected NO_x release to 1400 ppm, owing to excess air. The emissions of gases from different blended samples and mineral transformations were investigated and discussed in this study.