Co-firing biomass with coal in bubbling fluidized bed combustors

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2007

Öğrenci: ZUHAL GÖĞEBAKAN

Danışman: NEVİN SELÇUK

Özet:

Co-firing of biomass with coal in fluidized bed combustors is a promising alternative which leads to environmentally friendly use of coal by reducing emissions and provides utilization of biomass residues. Therefore, effect of biomass share on gaseous pollutant emissions from fluidized bed co-firing of various biomass fuels with high calorific value coals have extensively been investigated to date. However, effect of co-firing of olive residue, hazelnut shell and cotton residue with low calorific value lignites having high ash and sulfur contents has not been studied in bubbling fluidized bed combustors to date. In this thesis study, co-firing of typical Turkish lignite with olive residue, hazelnut shell and cotton residue in 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustion (ABFBC) Test Rig was investigated in terms of combustion and emission performance and ash behavior of different fuel blends. The results reveal that co-firing of olive residue, hazelnut shell and cotton residue with lignite increases the combustion efficiency and freeboard temperatures compared to those of lignite firing with limestone addition only. O2 and CO2 emissions are not found sensitive to increase in olive residue, hazelnut shell and cotton residue share in fuel blend. Co-firing lowers SO2 emissions considerably while increasing CO emissions. Co-firing of olive residue and hazelnut shell has no significant influence on NO emissions, however, reduces N2O emissions. Co-firing cotton residue results in higher NO and N2O emissions. Regarding to major, minor and trace elements partitioning, co-firing lignite with biomasses under consideration shifts the partitioning of these elements from bottom ash to fly ash. No chlorine is detected in both EDX and XRD analyses of the ash deposits. In conclusion, olive residue, hazelnut shell and cotton residue can easily be co-fired with high ash and sulfur containing lignite without agglomeration and fouling problems.