催化热解生物质制取富氢气体的研究

Production of hydrogen-rich gas from biomass by catalytic pyrolysis

在实验室自制的固定床反应器上,考察了秸秆和锯屑的热解行为,研究了热解产物分布特别是富氢气体的体积分数和产率,着重研究了(5种金属氧化物和2种碳酸盐催化剂)的催化效果。结果表明,温度从500℃提高到850℃,秸秆和锯屑的热解气产率分别从29.0%提高到40.6%,35.0%提高到46.5%,而对应的富氢气体的体积分数分别从41.2%提高到48.2%,40.6%提高到47.0%;在5种金属氧化物中,Cr2O3显示了最好的催化效果,在750℃时对应的热解气产率与不使用催化剂相比提高了10%,富氢气体的体积分数提高了13%;催化剂(CaCO3和Na2CO3)占生物质的质量分数对热解气和富氢气体产率有明显的影响,当质量分数从0增加到30%时,热解气和富氢气体产率增加较明显,而后其值的增加可以忽略,因此推荐使用的催化剂质量分数为30%。

Aimed at producing hydrogen-rich gas, pyrolysis of rice straw and sawdust was carried out in a fixed-bed reactor at different temperatures with catalyst (Cr_2O_3, MnO, FeO, Al_2O_3, CaO, CuO and Na_2CO_3). The results show that at current operating conditions, total gas yield and hydrogen-rich gas yield are low. However, it could be improved by using catalysts. The addition of Cr_2O_3 at 750?℃ leads to the increase of the total gas yield by 10% and the concentration of hydrogen-rich gas by 13%. High temperature favours the yield of total gas and the concentration of hydrogen-rich gas. When the temperature rises from 500?℃ to 850?℃, the yield of total gas and the concentration of hydrogen-rich gas, for rice straw pyrolysis, increase from 29.0% to 40.6%, and 41.2% to 48.2%, respectively; for sawdust pyrolysis from 35.0% to 46.5%, and 40.6% to 47.0%, respectively. The catalysts used exert positive effect on pyrolysis of rice straw and sawdust, however, Cr_2O_3 appears stronger catalytic role than other metal oxides. 30% catalysts (CaCO_3, Na_2CO_3) is recommended because higher amount of catalyst almost does not improve catalytic activity again. The addition of CaCO_3 or Na_2CO_3 increases the yields of total gas and also of hydrogen-rich gas. Catalytic performance of Na_2CO_3 shows a little bit better than that of CaCO_3 in the case of rice straw pyrolysis.