霍州煤氧化性气氛下热解预脱硫及硫的变迁

SULFUR REMOVAL AND TRANSFORMATION OF HUOZHOU COAL DURING PYROLYSIS UNDER OXIDATIVE ATMOSPHERE

利用流化床反应系统对霍州原煤在氧气浓度(体积分数)分别为2.5%,5.5%和8.5%O2-N2混合气,热解温度分别为400℃,500℃,600℃,700℃和800℃,热解停留时间为20min的条件下进行了热解预脱硫的研究.结果表明,在氧气浓度为5.5%,热解温度为700℃时的脱硫效果最佳,脱硫率可达70%以上.而且,与惰性气氛下热解相比,半焦产率没有明显降低.当继续加大氧气浓度或升高热解温度时,虽然脱硫率有所增加,但是半焦产率却大大降低,且半焦产率的降幅要大于脱硫率的升幅.通过热解质谱(PY-MS)实验表明,在1%O2-He气氛下,SO2和CO2在500℃以前的逸出趋势基本相同,这说明氧气在低温时对不稳定有机硫中的CS键能够选择性断裂,此时煤中的CC键不受影响;随后CO也开始逸出,使得它们的逸出趋势稍微发生了变化,最后这三个峰基本在同时达到了最大,这是由于随着温度的升高,CS键被氧气选择性断裂的同时,CC键也大量参与到了反应中来,使氧气由原来的过量变得相对不足,从而使得部分碳转化为CO.

Huozhou （HZ） raw coal was used to study sulfur removal in fluidized bed reactor under 2.5%,5.5% and 8. 5% O2-N2 atmosphere;at the temperature of 400 ℃,500 ℃, 600 ℃, 700 ℃ and 800 ℃, and the residence time is 20 min. The optimal condition of sulfur removal is under 5.5%O2-N2 atmosphere at 700 ℃ ,sulfur removal can reach about 70%. Compard with char yields under inert atmosphere, the one decreases a little. However, with the increasing of oxygen content, sulfur removal increases, while the char yields decrease much ,and decreasing ratio of char yield is higher than the increasing ratio of sulfur removal. In this study, PY-MS was also used to study the sulfur transformation during pyrolysis,the evolution trends of SO2 and CO2 are almost the same before 500 ℃ under 1% O2-He atmosphere, which suggests that oxygen selectively breaks the bonds of C-S of unstable sulfur compounds in the coal at lower temperature, and at this time the bonds of C-C are not influenced, as the intensity of CO is also very low. With the temperature increasing,CO starts to evolve, which makes the trends of SO2 and CO2 change a little, at last the peaks of these gases reach maximum at the same temperature. This suggests that with the temperature increasing, when oxygen breaks the bonds of C-S in the stable sulfur compounds,most bonds of C-C are also broken. Most bonds of C-C take part in reaction with the oxygen, which make the oxygen not enough to oxide the C to CO2, so most of C are transferred to CO.