The effect of pretreatment on pyrolysis and combustion characteristics of refuse derived fuel

Refuse Derived Fuel (RDF) does not have a homogeneous composition due to the reason that it is obtained by applying certain physical processes to municipal solid waste. Previous studies, which are done on RDF, have indicated that RDF produced in Turkey has a high inorganic material content, that?s why both pyrolysis profile and combustion characteristics of RDF are different from those produced in other countries. The most important effect that affects the pyrolysis characteristics and combustion properties has been found as inorganic based fillers and additives in paper and plastics. In the present MSc thesis, the samples which were taken from Süreko Recydia A. Ş. were leached with water and acid solutions (HCl and HNO3) prepared in different concentrations (weight percentage 2%, 5% and 10%). The effect of pretreatment on pyrolysis and combustion characteristics of RDF were investigated. At the end of the each leaching process, the heating value of the RDF was increased and the amount of ash was decreased. No change was seen in the sulfur content of RDF. At all leaching processes, which were done with HNO3, an increase in the weight percentage of nitrogen was observed. The reason was the adsorption of HNO3 solution to the surface of the RDF. Raw RDF was thermally decomposed in three stages. The first stage (250-350oC) represented the degradation of cellulosic fraction; the second stage (400-500 oC) represented the degradation of plastic fraction and the third stage (250-350oC) represented the degradation of carbonate based inorganic filling material. Leaching with water did not change the pyrolysis characteristics of RDF, but increased the cellulosic fraction and decreased the carbonate fraction. At all concentrations of HCl and HNO3 investigated, it was determined that cellulosic fraction was increased and the third stage was completely removed. Additionally, leaching period had no effect in acid leaching process. Combustion profile of raw RDF under pure oxygen reflected one step reaction and combustion occurred in the gas phase with the burning of volatile materials released through pyrolysis step. Leaching with water did not change the combustion profile but increase the reaction conversion. After leaching with acids, the peak temperatures where the maximum weight loss were seen decreased. This indicated that combustion started earlier. Similarly, leaching with acids increased the conversion.