碳酸钾对生物焦水蒸气气化性能的影响

Effect of Potassium Carbonate on Steam Gasification of Biomass Char

以落叶松炭、椰壳活性炭为原料,在微波固定床水蒸气气化装置上考察了碳酸钾添加方式和添加量对生物焦水蒸气气化性能的影响。结果表明:与传统的浸渍法相比,机械混合法操作简单,具有更高的水转化率、碳转化率、合成气产率、氢气产率,且气化气中合成气的占比更高。在生物焦催化气化过程中存在饱和K_(2)CO_(3)添加量,水蒸气气化反应活性越低的生物焦的K_(2)CO_(3)饱和添加量越高。在不添加和低K_(2)CO_(3)添加量的条件下,生物焦的气化性能主要取决于其原料的特性,而随着K_(2)CO_(3)添加量的增加,原料气化性能的差异逐渐弱化,K_(2)CO_(3)的催化作用占据主导,当添加量大于所有原料的饱和添加量之后,生物焦原料的差异性不再成为生物焦气化反应性能的影响因素。在饱和K_(2)CO_(3)添加量下,落叶松焦炭最高的水转化率和碳转化率可分别达到96%和72%,最高的合成气产率和氢气产率分别为每千克生物焦1 268 g和105 g,分别是相同反应条件下未添加K_(2)CO_(3)反应体系的4.7倍和2.1倍。在显著改善生物焦的水蒸气气化活性的同时兼顾反应的经济性,质量分数1.25%~5%是较佳的K_(2)CO_(3)添加量。

Larch char and coconut shell actived carbon were selected as the raw materials of the microwave fixed bed steam gasification unit, where the steam gasification reactions were conducted with the addition of K_(2)CO_(3). The experimental results indicated that, compared with impregnation, mechanical mixing gained not only an easier operation, but also higher water conversion, carbon conversion, syngas yield, hydrogen yield, and higher syngas proportion in gasification gas. The saturated addition amount of K_(2)CO_(3) existed and increased with the decrease of the reactivity of biomass char. The steam gasification performance of biomass char mainly depended on the characteristics of the raw materials in case of no or a small amount of K_(2)CO_(3) addition. With the increase of the amount of K_(2)CO_(3) added, the disparity in gasification activities between different biomass char narrowed while the catalytic effect of K_(2)CO_(3) gradually took over control. The difference of feedstocks was no longer a factor influencing the steam gasification reactivity of biomass char with a K_(2)CO_(3) addition amount exceeded the saturated addition amount of all the raw materials. With the saturated addition amount of potassium carbonate, the highest water conversion of larch char reached 96% and 72%, the highest synthesis gas yield and hydrogen yield were 1 268 and 105 g·kg^(-1) biochar, respectively, which were 4.7 times and 2.1 times of the reaction without K_(2)CO_(3) under the same reaction condition. The optimal addition amount of K_(2)CO_(3) between 1.25% and 5% can not only dramatically improve the steam gasification activity of biochar, but also take the economy of the reaction process into account.