Study On Fuel Staging Cyclone Gasification And Characterization Of Gasification Char Of Wood Powder

In recent years, the development and application of biomass energy has attracted more attention due to the environmental and energy problems became major concerns. Wood powder is the garbage of wood production and the rational utilization of these biomass resources could turn the waste into wealth by generating electric power and supply heating gas.Cyclone gasifier is a new type of entrained-flow reactor with low temperature and high product quality. In this paper, wood powder is staged gasified by cyclone gasifier. The effect of feeding ratio, air equivalence ratio and the feeding amount on the gasification were studied. The experimental results indicate that when the secondary air which was fed into the lower part of the gasifier is less than 2 Nm~3/h, the effect of gasification is not good. Increasing the secondary air lower from 3.5-5.5 Nm~3/h , the effect of gasification was improved obviously. It shows the optimum air equivalent ratio is between 0.26 and 0.29, and the staging feeding ratio of lower part is no more than 20% of total feeding. The low heating value of experiment is 5.36-5.77 MJ/Nm~3, the biogas yield is 1.7-1.84 kg/Nm~3, the gasification efficiency is 61%, the tar content of gas is 2/15-1.39 g/Nm~3.The Drop tube furnace was used to study the characteristics of gasified char of wood powder in this paper. The experiments of gasification were done in different temperatures (800-1000℃), different air equivalent ratios(ER=0,0.16,0.26,0.36) and different residence time(0.5s,0.7s,0.9s,1.1s) in which the particle size of wood powder is below 0.7mm. The surface microstructure, specific surface area, pore volume and pore size distribution of chars in different conditions were analyzed by SEM(Scanning electron microscopy)/EDS(X-ray energy dispersive spectroscopy) and the mercury intrusion porosimetry apparatus. The experimental results show that the temperature is the most important parameter which affects the gasified char. The specific surface area increases as the temperature increases. When the temperature is higher than 1000℃, the remelting appears in the surface of char, due to the original eukaryotic cell structure is damaged by alkali metals Potassium. The gasified char was influenced by metaph deformation and volatile release, in which the former was achieved in 0.5s and the effect of volatile release was greatly improved as the gasification temperature, residence time and as well as the air equivalence ratio. The experiment results indicates that the temperature has great impact on the character of gasification coke, the specific surface area increased by the increasing of temperature. A few surface of coke is melted when the temperature is above 1000℃,which is connected with the low coke ash melting points caused by alkali metal K. Plastic deformation and volatilize both have influence at gasification coke. Plastic deformation is done in the 0.5s settling time. The pore-creating of volatilize has more effects on gasification by the increasing of temperature, residence time and air equivalence ratio.