CaO对木屑水蒸气气化制取富氢燃气的影响

Influence of CaO on Hydrogen-rich Gas Production by Steam Gasification of Sawdust

以木屑为生物质原料,水蒸气为气化介质,CaO为催化剂,在固定床气化炉中进行生物质催化气化制取富氢燃气,考察了CaO与木屑中碳元素的物质的量比(n(Ca)/n(C))、气化温度和水蒸气流量对生物质水蒸气气化特性的影响。结果表明,当n(Ca)/n(C)由0增加至1.0时,H_2体积分数由45.58%增至58.62%,产气率由1.04 m^3/kg增至1.38 m^3/kg,当n(Ca)/n(C)继续增至1.5时,两者均有增加,但是变化不明显;气化温度从700℃增至750℃时,产气中H_2体积分数由51.78%增至58.62%,CO_2由19.89%降至12.60%,继续升高温度,H_2体积分数逐渐降低,燃气热值也降低;水蒸气流量由0.1 g/(min·g)增至0.34 g/(min·g)时,H_2的体积分数由58.62%增至62.55%,水蒸气流量继续增大时,H_2的体积分数和产氢率降低,燃气热值也降低。通过实验选择的最佳气化条件为以CaO为催化剂,n(Ca)/n(C)为1,气化温度750℃,水蒸气流量为0.34 g/(min·g),此时,制取的富氢燃气中H_2体积分数达到最大为62.55%,产氢率为85.08 g/kg,燃气热值为11.41 MJ/m^3。

The steam gasification experiments of sawdust for production of hydrogen-rich gas were carried out in the high- temperature fixed bed reactor using steam as gasification agent and CaO as catalyst. The effects of the molar ratio of CaO and carbon element of sawdust （n（ Ca）/n（C） ）, temperature and steam flow rate on gasification characteristics were investigated. The results showed that with the increament of n（ Ca）/n（C） from 0 to 1.0, the volume fraction of hydrogen increased from 45.58 % to 58. 62 % , and the dry gas yield increased from 1.04 m3/kg to 1.38 m3/kg; the hydrogen content and dry gas yield only showed a modest increase as the n（ Ca）/n（C） increased to 1.5. With increasing the gasification temperature from 700 to 750 ℃, the volume fraction of hydrogen significantly increased from 51.78 % to 58.62 % , and that of carbon dioxide decreased from 19. 89 % to 12. 60 % ; as the temperature kept rising, the hydrogen content and the low heating value decreased. By increasing the steam flow rate from 0. 1 g/（ min. g） to 0. 34 g/（ rain＂ g）, the volume fraction of hydrogen increased from 58. 62 % to 62. 55 %. However, the hydrogen content, the hydrogen yield and the low heating value decreased when the steam flow rate was higher than 0. 34 g/（ min. g）. The optimized conditions with CaO as catalyst were n（ Ca）/n（C） = 1, the gasification temperature 750℃ and the steam flow rate 0. 34 g/（ min· g）. Under these conditions, the volume fraction of hydrogen was 62. 55 % , the hydrogen yield was 85.08 g/kg, the low heating value was 11.41 MJ/m3.