dc.description.abstract | This research investigates that evaluation on energy yields and metals partitioning characterization in co-gasification of sewage sludge (SS) and industrial wastewater sludge (IS) using fluidized bed gasifier with controlling temperature (600~800℃), IS ratio (0% to 60%), and steam-to-biomass ratio (S/B)(0 to 1.0).The functional group of gaseous speciation, thermal and kinetic characteristics in co-gasification of SS and IS by a thermal gravimetric analysis connected with a Fourier-transformed infrared spectrometer (TGA-FTIR) were also discussed.
The experimental results indicated that the thermal decomposition stages of tested sludge were including cellulose/semi-cellulose cracking stage (200~400℃), lignin decomposition stage (400~600℃), and fixed carbon volatilization stage (800~900℃) by TGA-FTIR. In the case of pyrolysis condition, the functional group of carbonyl, aromatic, O-H, and C-H were identified via devolatilization and dehydration reaction during thermal conversion process. When the CO2 used as reaction atmosphere, the functional group of C-O was identified in the gaseous products resulting in Boudouard reaction. In the case of gasification reaction (ER 0.3), the above functional groups were also identified in thermal conversion. However, the functional groups of ether and organic acid were extra speciation identified in the gaseous products. Based on the analysis results of pyrolysis condition, the activation energy was significantly decreased from 44.5 kJ/mol to 22.1 kJ/mol with IS addition ratio increasing from 0% to 100%. In the case of CO2 and air gasification, the activation energy was also decreased from 37.7 kJ/mol to 19.5 kJ/mol and from 40.7 kJ/mol to 19.1 kJ/mol with an increase in IS addition ratio, respectively. This is because the catalytic effect on the promotion of thermal reaction resulting in IS contains some Fe/Mn contents.
In the case of gasification temperature 800℃, the hydrogen production was increased from 9.1 vol. % to 12.46 vol.% with the IS addition ratio increasing from 0% to 40%. The cold gas efficiency (CGE) was significantly increased from 37.89% to 60.85%. Meanwhile, the energy conversion and CGE were increased with the steam-to-biomass ratio increasing. This is due to the steam will enhance the water gas reaction in the gasification process. Based on the energy distribution analysis results, the energy yield was approximately 30%~50% produced from gaseous products in co-gasification of tested sludge. In the case of gasification temperature 800℃, the total energy recovery rate was approximately ranged from 31.59% to 50.91%. By increasing IS addition ratio, it could enhance the total energy recovery rate in co-gasification. The metals partitioning results indicated that the Cu, Zn, and Cr were partitioned in solid phase with an increase in IS addition ratio. However, Pb partitioning percentage of solid phase was decreasing with IS addition ratio increasing. The metals partitioning characteristics were affected by sludge and metals physicochemical properties. In summary, the basic characterization of sewage sludge and industrial wastewater sludge and their kinetic parameters during thermal process were established, but also the confirmation on performance of industrial wastewater sludge used as co-gasification material and feasibility of improving energy yield. Therefore, the results of this study could provide the good information for energy conversion technologies selection of organic sludge waste. | en_US |