煤岩有机显微组分热解过程中HCN和NH_3生成规律的研究

Studies on the formation of HCN and NH_3 during coal macerals pyrolysis

经等密度梯度离心分离,从褐煤、长焰煤、气煤和贫煤四种不同变质程度煤中获得了高纯度的有机显微组分。用石英管式反应器在600℃～900℃考察了煤岩有机显微组分热解过程中HCN和NH3的生成规律。实验结果表明,在显微组分热解过程中HCN主要是挥发分二次裂解的产物。在镜质组热解过程中,煤的变质程度越高,HCN的生成率越低,热解温度越高,HCN的生成率越高;同一种煤三种有机显微组分热解过程中,HCN的生成不仅与显微组分挥发分的质量分数有关,而且与显微组分中氮的存在形态有关,在较低温度热解时吡咯型氮质量分数高的煤样HCN的生成率较高。显微组分热解过程中NH3来自于挥发分的二次热裂解,与焦的热裂解有关,随煤变质程度增高,镜质组热解过程中NH3的收率降低;对同一种煤三种煤岩有机显微组分,由于其黏结性不同,含氮官能团和氢自由基的接触几率不同,生成NH3的能力也不同,惰质组的NH3生成率最高,壳质组最低;温度对NH3的生成也有影响,800℃NH3的生成率最高,惰质组NH3的生成率为11.8%,壳质组NH3的生成率为5.2%。

Coal maceral concentrates of high purity were prepared from four different rank coals by Density Gradient Centrifugation method. The formation of HCN and NH_3 during macerals pyrolysis was investigated in a tubular quartz reactor at the temperature of 600?℃～900?℃. The results show that HCN is mainly produced by the secondary thermal cracking of coal volatile. It also shows that the HCN yield increases with temperature and decreases with coal rank for vitrinite pyrolysis. For three macerals from Pingshuo gas coal, the yield of HCN is not only related to their volatile content but also associated with the nitrogen functional group in different macerals. Macerals withmore pyrrole-type nitrogen could release more HCN at lower temperature. As for the formation of NH_3, besides the volatile thermal cracking, the char pyrolysis also plays a important role. The yield of NH_3 depends on the probability of contact between nitrogen functional group and hydrogen radical. On the experiment conditions, the NH_3 yield decreases with coal rank for vitrinite pyrolysis. The inertinite of less caking has more nitrogen converted to NH_3 than vitrinite and liptinite. The yield of NH_3 during pyrolysis at 800?℃ is maximum with 11.8% for inertinite and 5.2% for liptinite.