Characteristics of reaction kinetic and energy yield in Biomass-to-Energy by a catalytic gasification

• Main Authors: Kuang-Li Chien, 簡光勵
• Other Authors: Kung-Yuh Chiang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/53667735579952255354

博士 === 逢甲大學 === 環境工程與科學所 === 100 === This research investigates the establishment of characteristics of common kinds of biomass in Taiwan for selecting and suggesting of the pretreatment technologies in biomass-to-energy conversion process. The corrosion and agglomeration of gasifer caused by the different properties of feedstock were also studied. To develop the kinetic parameters of the biomass gasification, the thermogravimetric analysis was used in this research for establishing the operation parameters in biomass gasification and/or catalytic gasification. Besides, the enhancement of energy yield efficiency and improvement of agglomeration in fluidized bed gasifer were also discussed. Based on the characteristics results of the various kinds of biomass, volatile matter and fixed carbon content of all tested biomass were ranged between 60% to 80% and 10% to 20%, respectively. The higher volatile matter content, H/C ratio (or O/C ratio), and H2O/FC ratio in biomass resulted in lower ignition temperature during thermal conversion process. Meanwhile, higher H2O/FC ratio in biomass could promote the water-gas reaction and the water gas shift reaction resulted in large amounts of combustible gas yield during thermal conversion process. In addition, according to the results of alkali index, bed agglomeration index, and the base-to-acid ratio analysis, the tendency of agglomeration in gasifier increased with an increase in sum of K2O and Na2O composition of biomass. In this research, the highest sodium and potassium content was found in the ashes of agricultural wastes, such as banana trimmings, longan trimmings, rice straw and bamboo’s chopsticks, It can conclude that above biomass caused easily ash deposits in quartz sand or gasifier wall resulting in an increasing tendency of ash melting and agglomeration. According to the results of mass change rate of biomass over time by thermogravimetric analysis method, the reactivity of gasification in the all tested biomass were found in decreasing order as: agricultural wastes, woody biomass, and waste-derived-fuels. On the other hand, using carbon dioxide as a carrier gas in gasification reaction could lower the activation energy to promote the efficiency of thermal decomposition in biomass gasification. Furthermore, the tested mineral catalysts used in this research can enhance the thermal decomposition efficiency of the all tested biomass as well as decreasing the activation energy, reaction time and increasing the reactivity. The results of energy yield of disposal chopsticks in fluidized bed gasifier showed that the synthesis gas yield and heating value increased with the gasification temperature increasing from 600℃ to 800℃. The synthesis gas yield and heating value were ranged from 49.54% to 64.06% and 9.28 MJ/Nm3 to 12.12 MJ/Nm3, respectively. However, increasing the gasification temperature could tend to the agglomeration in the fludized bed gasifier. The tested catalysts, such as CaO, silicate, zeolite, and Fe/Mn sludge, could promote the synthesis gas yield in gasification. In the case of 5% tested catalysts addition and gasification temperature of 600℃, the synthesis gas yield and heating value increased approximately from 49.54% to 52.79% and from 9.28 MJ/Nm3 to 10.03 MJ/Nm3, respectively. In summary, the tested catalysts could significantly reduce the tendency of agglomeration, enhance the efficiency of synthesis gas yield, and improve the quality of synthesis gas in a low-temperature catalytic gasification.