| This research has been implemented as one of activities of projects "Research on high temperature air gasification for biomass" (863 scheme, No. 2001AA514013) and "Research on process of high-temperature gasification for Municipal Solid Waste (MSW)" (invested by Zhuzhou Torch Industrial Furnace Inc., Hunan Province). To optimize the performance of system including the high-temperature air generator and high-temperature gasifier, and to promote the level of collecting and utilizing low-heat value and low-density energy from MSW, biomass and low-heat value fuel in our country, a new mathematic model of gasification has been established and hot gasification tests have been carried out.Based on material balance, energy balance and chemical equilibrium, the mathematic model of gasification has been established. The model can be applied to all kinds of solid fuel. The effects of biomass species, air temperature and fraction of steam in the feed gas on gasification has been researched. The conclusions are shown as below:At 900~1300℃, the high-heat-value (HHV) of syngas and gasification efficiency increase with the increase of gasification temperature. When air temperature increases by 100℃, the HHV of syngas increases by 0.25~0.32 MJ/Nm~3. As the gasification of pine sawdust as concerned, the HHV of syngas increases by 22.41% when gasification temperature rises from 900℃ to 1300℃ and reaches 7.1 MJ/Nm~3 at 1300℃.The HHV of syngas and gasification efficiency increase with the increase of fraction of steam in the feed gas. When the fraction of steam in the feed gas increases by 10%, the HHV of syngas increases by 0.46~0.53 MJ/Nm~3. Concerning the gasification of pine sawdust at 1100℃, when the fraction of steam in the feed gas increases to 60%, the HHV of syngas increases by 44.87% and is close to middle heat value.Compared with high temperature air gasification, when theoxygen is used as gasifying agent for gasifying pine sawdust at 1300°C, the HHV of syngas increases by 83.94% and reaches middle heat value.> The model can forecast the results of gasification reaction. Hot gasification tests for sawdust have been completed. Through the new methods of self-heating, the temperature inside the gasifier can quickly increase to 1200°C and ensure high temperature gasification reactions. The experimental results of heat value and the content of CO2 and CxHy accord with the ones from the model. The fact that high-temperature air gasification can make the HHV of syngas higher is proved. When gasification temperature is 1000°C, The syngas with HHV of 6.19 MJ/Nm3 has been gained at temperature of 1000°C.The effect of the pressure on the gasification reaction has been studied. The results show that when the pressure increases, the gasification reaction rate will be faster, the concentration of CO and H2 reduce, the concentration of CH4 increase and undecomposed vapor increase. When the pressure increases from 1 to 200atm, the concentration of CH4 will increase from 0.06% to 5.66%. Pressure has little effect on the heat value of syngas. |
