有机含氧官能团对煤的热解和燃烧过程具有重要影响。目前关于引入的外来官能团对煤热转化过程中生成NOx的影响的研究较为欠缺。本研究使用过氧化氢、过氧乙酸、硝酸和过硫酸铵4种典型的化学试剂对2种煤阶的煤粉(无烟煤煤粉和烟煤煤粉)进行了化学氧化改性,利用13C-NMR和XPS分别获得了改性前后煤粉含氧官能团和含氮官能团的变化规律,并对原煤和改性煤进行了热解和燃烧实验。13C-NMR结果表明:过氧乙酸溶液和过氧化氢溶液均可通过氧化使煤中烷基芳香碳和氧基取代芳碳断键。5%(质量分数)过氧乙酸溶液可在煤中引入醇羟基、羧基等官能团,1%和5%(质量分数)的过氧化氢溶液与煤粉反应无法引入含氧官能团。XPS结果表明:5%过氧乙酸溶液可将煤粉表面的吡咯型氮(N-5)、吡啶型氮(N-6)氧化为氧化物氮(N-X)结构。此外,过氧乙酸溶液和过二硫酸铵溶液可将煤中芳香胺结构氧化为—NO2基团,此结构在180℃开始受热分解。在热解过程中,过氧乙酸溶液改性后的煤粉在更低的温度下释放出了更多的NOx,N2O释放温度降低至200℃,NOx生成途径发生了改变。过氧乙酸溶液对两种煤的改性效果一致,且对于无烟煤来说,粒径越小,过氧乙酸溶液改性效果越明显。过氧乙酸溶液改性后,煤粉中燃料氮向气相氮的转换得到调控与强化,为后续煤燃烧烟气中NOx的脱除创造了更多的时间与空间,丰富了NOx生成理论。基于实验结果,本研究提出了过氧乙酸改性与空气分级技术耦合的NOx减排新设想。

The presence of organic O-containing functional groups in coal can significantlyO-containing and N-containing functional groups, and the pyrolysis and combustion experiments of raw and modified coal were conducted successively. The 13C-NMR results reveal that both per-acetic acid solution and hydrogen peroxide solution can break alkyl aromatic and O-substituted ar-yl carbon by oxidation in coal. A 5% (mass fraction) peracetic acid solution is able to introduce functional groups such as alcohol hydroxyl group and carboxyl group into coal, whereas 1% and 5% (mass fraction) hydrogen peroxide solutions do not exhibit such performance. XPS results indicate that a 5% peracetic acid solution can oxidize pyrrole nitrogen (N-5) and pyridine nitrogen (N-6) on the surface of pulverized coal into oxide nitrogen (N-X) structure. Additionally, the aromatic amine structure in the coal can be oxidized to form —NO2 group by peracetic acid solu-tion and ammonium persulfate solution. This structure begins to decompose upon heating at 180 ℃. During the pyrolysis process, the samples modified by peracetic acid solution release more NOx at a lower temperature, consequently lowering the release temperature of N2O to 200 ℃, thereby altering the NOx generation pathway. The two kinds of coal have the same modification effect. For anthracite, with the particle sizes decreasing, the modification effect becomes more obvious. After peracetic acid modification, the conversion of fuel nitrogen to gas phase is strengthened, which enriches NOx formation theory and creates more time for the subsequent removal of NOx. Based on the experimental results, a novel approach to reduce NOx emission is proposed, which involves coupling peracetic acid modification with air classification technology.