不同钙基吸收剂对玉米秸秆热解气化制氢特性的影响

Effects of different calcium-based absorbents on hydrogen production of corn stalk pyrolysis-gasification

为了揭示不同钙基吸收剂对生物质热解气化制氢特性的影响机理,以玉米秸秆为原料在一个两段式热解气化装置上研究了添加不同钙基吸收剂对其制氢特性的影响,结果表明:煅烧石灰石、煅烧碳酸钙和煅烧白云石等3种吸收剂的添加均可有效吸收玉米秸秆热解气化过程中生成的CO_2,促进水气变换(WGS)反应的平衡向右移动,从而生成更多H_2;同时,吸收剂的主要组分CaO还可催化玉米秸秆热解挥发分的裂解与气化反应以及WGS反应,从而显著提高产气中H_2的体积分数与产率。另外,煅烧白云石中的含镁组分还显示出对气化过程以及CO_2吸收具有进一步的催化作用,使得其在玉米秸秆热解气化过程中可获得更高的H_2体积分数(71.8%)和产率[224.5 m L/(g db biomass)]。

The aim of this study is to reveal the influencing mechanism of different calcium-based absorbents on the hydrogen production of biomass pyrolysis-gasification. Using corn stalk as feedstock, the effects of several calcium-based absorbents on the hydrogen production characteristics were investigated in a two-stage fixed-bed biomass pyrolysis-gasification system. The results indicated that the addition of calcined limestone, calcined CaCO3 and calcined dolomite could effectively absorb the CO2 generated during the pyrolysis-gasification of corn stalk, which thus shifted the chemical equilibrium of water gas shift（WGS） reaction to produce more H2. Meanwhile, it was found that the main components CaO in the absorbents could also catalyze the cracking and steam gasification of pyrolytic volatiles as well as the WGS reaction, hence significantly increased the volume concentration and yield of H2 in the product gas. Furthermore, the magnesium component in the calcined dolomite was proved to have further catalytic effect on the gasification process as well as the CO2 absorption reaction to achieve a higher H2 concentration of 71.8% and yield of 224.5m L/（g db biomass）.