生物质气化技术是将低品位的生物质能转换成高品位能源的有效途径.该文以稻壳和麦秸半焦为试验对象，进行了低温下生物质半焦的水蒸气气化试验，研究了浸渍法制备的碱金属催化剂和气化温度对生物质半焦气化行为的影响.结果显示，对于稻壳半焦气化而言，相同负载量的 K 基催化剂的催化效果明显优于 Na 基催化剂，相比非催化时稻壳半焦的碳转化率分别提高了18.2%和13.5%，差异明显.增加 K2CO3负载量有利于半焦气化反应的进行，但负载量不宜超过30%.不同的煅烧温度，催化剂的活性组分存在形式有较大差别，负载量为30%的K 基催化剂在800℃煅烧后具有最佳的催化效果.相同条件下，麦秸半焦的气体产率和碳转化率均较高，在700℃下添加该催化剂时分别达到130.0 mol/kg 和95.9%，相比非催化时分别提高了57.0%和34.1%.随着温度的降低，气体产率和碳转化率均明显下降，该文催化条件下的半焦气化温度不宜低于700℃.研究结果可为生物质低温气化高效催化剂的选择提供理论依据.%The low-temperature catalytic gasification of biomass is a promising technology for hydrogen production from the energy point of view due to its relatively low heat input. And it has attracted the worldwide interests. However, the lower char conversion efficiency and higher tar yield at low-temperature are unsolved problems to the technical application of low-temperature catalytic gasification. In order to overcome these issues, numerous researches are being focused on the catalyst development. As the studies concerning catalytic gasification of biomass char under relatively low temperature (T≤750℃) are fairly limited, catalytic gasification of two biomass char samples, rice husk and wheat straw, were investigated at relatively low temperature in this paper. The impregnated alkali metal catalysts were prepared in this study. In which, Al2O3 was used as carrier of the catalyst, and potassium carbonate and sodium carbonate were used as active ingredient, respectively. In addition, the catalyst components were detected by X-ray diffraction analysis (XRD). Using the prepared catalysts, catalytic steam gasification of biomass char was carried out in a lab-scale fluidized bed reactor at the temperature between 600 and 700℃ ℃ to investigate the performance of catalysts. And the effects of catalyst parameters including active ingredient, ingredient contents and calcination temperature, and gasification temperature on the behavior of char gasification were also studied. The results revealed that both potassium based catalyst and sodium based one have significant catalytic action on biomass char conversion. Moreover, potassium based catalyst exhibited better catalytic performance than sodium based one with the same content of active component in rice husk char gasification process. Compared with non-catalytic rice husk char gasification, carbon conversion efficiency was increased by 18.2% and 13.5% using 30KAl(600) and 30NaAl(600), respectively. Increasing K2CO3 content was beneficial to improving char conversion efficiency, and also increasing CO and H2 yield. However the active component contents were inadvisable beyond 30%. The catalyst prepared at different calcination temperature generated the different existing forms of active components. 30KAl(800) catalyst calcinated at 800℃ showed the optimal catalytic action on the char gasification. X-ray diffraction analysis (XRD) showed that the 30KAl(800) catalyst contained K2Al2O2(CO3)2·3H2O, and thus it may be a more effective component. The results showed that both gas yield and carbon conversion efficiency of wheat straw char were higher than those of rice husk char under the same gasification conditions. Thus it also reveals that alkali metal contained in biomass ash has catalytic action on char gasification. The gas yield and carbon conversion efficiency of wheat straw char reached 130.0 mol/kg-char and 95.9% respectively using 30KAl(800) catalyst at the gasification temperature of 700℃, which were 57.0% and 34.1% higher than those of non-catalytic gasification. It was also found that the gas yield and carbon conversion efficiency significantly reduced with decrease of gasification temperature. When gasification temperature was decreased to 600℃, the carbon conversion efficiency was only 19.1% using 30KAl(800) catalyst. Thus it was not appropriate for gasification at temperature below 700℃ based on the study.
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