神木原煤及其热解半焦的燃烧与污染物排放规律研究

Study on Combustion and Pollutant Emission of Shenmu Raw Coal and its Pyrolytic Semi-coke

为了研究原煤制半焦过程中颗粒表面官能团的变化,首先采用傅里叶变换红外光谱(FTIR)技术,对比分析了原煤与半焦中官能团的含量和类型。结果表明,原煤热解制半焦过程中,除脂肪族CH2,CH3较稳定以外,芳香族中酯、酸、醛、酮的C=O和芳核的C=C全部受热断裂、部分羟基反应生成了羧基、部分官能团中C-H被芳香环取代。这些反应活性较高的基团的减少,导致半焦相比原煤有明显的燃烧滞后性。在此基础上,利用热重–红外联用(TG-FTIR)技术,对比分析了原煤与半焦的燃烧和污染物排放规律。结果表明,相比原煤,半焦燃烧产生的灰壳较厚、透气性较差,导致其燃烧不稳定、不充分;虽然半焦中含氮、含硫物质的总量和种类更少,但由于焦炭的还原作用和大量生成的CO,半焦燃烧释放出更多的HCN,NH3和COS。

In order to study the change of surface functional group in the process of making semi-coke from raw coal,in this work,the content and types of functional groups in raw coal and semi-coke were compared and analyzed by Fourier transform infrared spectroscopy(FTIR)firstly.The results showed that in the process of making semi-coke from raw coal,except that aliphatic CH2 and CH3 were relatively stable,in the aromatic group,the C=O of esters,acids,aldehydes and ketones and the C=C bonds of aromatic nuclei were all broken.Carboxyl groups are generated by part of hydroxyl reaction,while C-H of part of functional groups is replaced by aromatic rings.The reduction of these groups with high reactivity results in obvious combustion hysteresis of semi-coke compared with raw coal.On this basis,TG-FTIR technology was used to compare and analyze the combustion and pollutant emission characteristics of raw coal and semi-coke.The results showed that compared with raw coal,the ash shell produced by semi-coke combustion was thicker and less breathable,resulting in less stable and insufficient combustion.Although the total amount and types of nitrogen-containing and sulfur-containing substances in semi-coke were less,more HCN,NH3 and COS were released from semi-coke combustion due to coke reduction and large amount of CO generation.