Date

2018

Author

Baghirzade, Mammadbaghir

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Coal continues to play a significant role in energy production over the world. However, its limited procurement and enormous side effects on global warming, make governments and organizations turn towards renewable energy resources like biomass which is CO2 neutral. Prior to utilization of fuels in power plants, it is important to investigate fuel behavior at high temperatures and high heating rates, i.e., close to heating rates in industrial applications. This understanding enables engineers to design appropriate and efficient boilers. However, until now, Turkish fuels have not been analyzed under high heating rate and high temperature conditions in laboratory settings to resemble the actual pulverized fuel combustion boilers. Therefore, in this study, combustion behavior of Turkish lignite and biomass fuels were studied in a laboratory environment close to the real conditions available in commercial power plants (i.e. pulverized fuel boilers). This work performed combustion and fast pyrolysis of Turkish biomass and lignite fuels, namely hazelnut shell (HS), olive residue (OR) and Soma lignite (SL) at high heating rates (~3000 ºC/s) in a novel wire mesh reactor (WMR). Particular emphasis was given to understand ash and char yields, their morphology and chemical composition, volatile yield, char reactivity of the chars obtained at high heating rates (~2200 ºC/s, 4550 ºC/s) and at elevated temperatures (~1100 ºC, 1500 ºC). In order to understand effect of moisture on fast pyrolysis conditions, dried and as received hazelnut shell fuels were pyrolyzed at two different temperatures, 1100 ºC and 1550 ºC, at heating rates of 2200 ºC/s and 4550 ºC/s respectively. Volatile yields from dried and as received HS chars obtained from both pyrolysis conditions, showed higher values nearly 85 wt.% than proximate analysis (PA) (HS-A: 75 wt. %, HS-D: 79.5 wt.%) performed at low heating rates (20 ºC/min). To investigate synergetic effect of co-pyrolysis of coal and biomass, two different blends of Soma lignite (SL) and hazelnut shell (HS) with mixing ratios of 50-50 wt.% and 75-25 wt.% were pyrolyzed. Thermogravimetric analysis (TGA) was conducted to carry out isothermal char combustion to study reactivity of individual and blended chars. In order to have kinetically controlled combustion environment in TGA, 400 º C for biomass chars, 450 º C for lignite and blended chars were decided as isothermal combustion temperatures. Individual hazelnut shell chars showed higher reactivity than individual lignite and blended chars and, therefore, shorter 90% burnout time (9.6 min) was observed for hazelnut shell chars compared to lignite (342 min) and blended chars (~160 min). Brunauer–Emmitt–Teller (BET) surface analysis was performed to determine surface areas of individual and blended chars obtained from high heating rate pyrolysis in WMR. Biomass chars were characterized by low surface areas (10-15 m2/g) due to rapid volatilization phenomenon at high heating rates.

Subject Keywords

Lignite., Biomass., Pyrolysis., Wire netting.

URI

http://etd.lib.metu.edu.tr/upload/12622440/index.pdf
https://hdl.handle.net/11511/27580

Collections

Graduate School of Natural and Applied Sciences, Thesis