生物质粗燃气自热重整调变的热力学分析

运用吉布斯自由能最小化方法对生物质粗燃气自热重整过程进行了热力学分析,研究了重整反应过程中的温度,O2/CH4摩尔比及焦油摩尔分数等因素对平衡产物组成的影响规律。研究结果表明:低温有利于CO歧化与加氢反应,而高温促进了CH4和CO2的转化,提高合成气H2+CO摩尔分数,降低H2/CO摩尔比。O2/CH4摩尔比的增加有利于生物质燃气从部分氧化反应向完全氧化反应转变,促进了CH4的重整反应而抑制了CO2的转化;O2/CH4摩尔比的增加降低了合成气H2+CO摩尔分数,降低了H2/CO摩尔比,在重整后的生物质粗燃气中,n(H2)/n(CO)≈1。积碳量随温度升高和O2/CH4摩尔比的增加逐渐减少,随着焦油(C10H8)物质的量的增加而增加。焦油物质的量增加提高了合成气中H2与CO摩尔分数,是重整反应的重要原料。优化的生物质燃气自热重整反应条件为温度1 023 K,O2/CH4摩尔比0.7,焦油摩尔分数<1%。

Thermodynamic analysis on autothermal reforming of biomass syngas

The thermodynamic equilibrium analysis on the autothermal reforming of biomass syngas was performed by using the minimization of Gibbs free energy.The effects of operation parameters such as temperature,O2/CH4 mole ratio and tar mole fraction on the reforming performances were studied.The results show that both the CO hydrogenation and Boudouard reaction are promoted,whereas methane reforming is restrained at lower temperature.Increasing temperature facilitates the conversion of methane and CO2,the increase of mole fraction of syngas formed and the decrease of H2/CO mole ratio.The increase of O2/CH4 mole ratio promotes the methane reforming and restrains the CO2 conversion,and it increases the amount of syngas formed and decreases the H2/CO ratio.After reforming,the n(H2) ∶ n(CO) is about 1.The amount of carbon deposit presents a decreasing trend with increasing temperature and O2/CH4 ratio.As an important raw fuel,tar can promote the total amount of syngas whereas resulting in carbon formation.The optimal autothermal reforming conditions were designed as 1 023 K,mole ratio of O2/CH4=0.7 and tar mole fraction<1%.