钙基固定剂对制氢和污染性气体减排的影响

Effect of Ca-based sorbents to hydrogen production and pollutant gas emission reduction

在未来相当长的一段时间内,煤气化仍是大规模制取氢气的主要途径。目前,常规煤气化过程得到的是H2、CO和CO2为主的混合气,需要通过净化、变换和分离工艺才能得到洁净的氢气,工艺过程复杂。采用连续式超临界水反应装置,以质量分数为20%的水煤浆为反应原料,考察了Ca/C摩尔比和温度对褐煤制氢系统的影响。试验结果表明:Ca(OH)2不仅可以很好地固定气相中的CO2和硫化物,而且对煤气化过程也表现出较好的催化作用。反应温度600℃,压力为25MPa的条件下,与未加Ca(OH)2相比,Ca/C摩尔比为0.45时,气体中CO2的体积分数由50.7%降至1.0%,趋于完全固定;硫化物浓度由10 878mg/m3降至807mg/m3;H2的体积分数由32.4%增至73.3%。Ca(OH)2对煤气化的催化作用在高温下更加明显。

Hydrogen is being promoted as the main green fuel for the future.Traditionally,hydrogen is produced in a large scale by coal gasification.The reserves of lignite in China are more than 140 billion tons while its utilization efficiency is rather low.Main obstacle of utilization of the coal in combustion or gasification process is that the water content in low rank coal is much higher than that in high rank coals.Hydrogen-rich gas production from Xiaolongtan lignite was successfully performed in a continuous supercritical water reactor with feeding of coal water slurry.The effects of Ca/C molar ratio and temperature on carbon gasification efficiency,product distribution and yields of gas were investigated.The content of CO2 and sulfid in gas product decreases,while that of hydrogen increases with the increase of Ca/C molar ratio.At Ca/C molar ratio of 0.45,nearly all CO2 is fixed.Correspondingly,the content of hydrogen in gas is 73.3%.Moreover,Ca（OH）2 catalyses gasification and water-shift reaction.The catalytic performance of calcium hydroxide is distinct at higher temperature.