基于多尺度效应的低阶煤低温快速热解及其粘结机理研究

Coal, especially the coking coal, is the foundation for the development of the coking industry. With the rapid development of iron-making industry in China, the problem of the shortage supply of coking coal becomes more and more prominent. On the other side, the reserve of the low rank coal with low cost and low contents of sulfur and ash accounts for about half of the total coal reserves in China. It's beneficial for expanding the coking resources, lowering the coking cost and adjusting the contents of ash and sulfur if they can be applied to coal blends. However, they cannot be directly employed to coal blending coking using the conventional coking process due to their poor caking property or non-caking property. Hence, Studies on their modification technology and the science underlying the improvement of their caking property by modification treatment is necessary to give us a better theoretical guidance for enlarging their mass blending ratio during the practical coal blending coking. The work here is to investigate the effect of the transformation of functional groups and the release discipline of the volatile substances on the caking property of low rank coal by low temperature rapid pyrolysis under different conditions, mainly by changing the heating rate, final pyrolysis temperature, coal particle size and the composition. Besides, research of the relationship between the coal particle size, its heating rate and the generation of plastic mass, curing temperature range is also carried out further to reveal the mechanism of the improvement of caking property of low rank coal by low temperature rapid pyrolysis.

煤炭是炼焦业赖以生存和发展的物质基础。我国炼焦煤资源紧缺，但低煤化度弱粘结性煤资源比较丰富，且低灰、低硫、价廉，如能在炼焦配煤中增加其用量，不仅可以扩大炼焦煤源，降低成本，而且可以调节焦炭的灰分、硫分。但低煤化度弱粘结性煤的粘结性差，如果直接配用，会导致焦炭质量恶化，因此，研究低煤化度弱粘结性煤的改质处理技术及其粘结机理，对改善其粘结能力, 扩大其在炼焦配煤中的配入量，具有重要的理论和实践意义。本课题旨在通过对低煤化度弱粘结性煤进行低温快速热解处理的基础上，着力于热解速率、热解终温、煤粒度及其组成等工艺因素，多尺度研究煤低温快速热解过程中官能团的变化及其挥发物质的析出规律对其粘结性的影响，以及不同粒径煤及其受热升温速率对其胶质体的产生和固化温度区间的关系，进而揭示出低温快速热解对提升低煤化度弱(非)粘结性煤粘结性的影响规律及其粘结机理，为低煤化度弱粘结性煤的提质处理提供理论依据。

本项目对神府煤进行了温度、加热时间、升温速率等尺度的低温快速热解实验，借助粘结力指数G’、红外、溶剂抽提、平均最大反射率、SEM、高温热台显微镜、热重分析仪、PY-GC-MS等分析仪器对热解改质机理进行了研究。.（1）神府煤粘结力指数测定结果表明，加热终温420℃、处理时间25min的效果最好。.（2）随着处理温度的升高，处理时间的延长，N2和CO2气氛下神府煤的Vdaf降低，由43.3%降至15.1%,真相对密度增加，C含量增加，H、O、N元素减少，S含量基本不变，芳碳率和粘结力指数增大，固化温度升高，b’先升高后减小，塑性温度区间变宽；三种酸性含氧官能团（总酸性基、羧基、酚羟基）都呈减少的趋势；总酸性基脱除率Dep与Vdaf以及△G’与总酸性基脱除率Dep呈线性相关：.Dep=0.0492△Vdaf+0.3283(r=0.9572＞R0.05=0.666).△G’=2.5912Dep-0.8219 (r=0.9810＞R0.05=0.666).（3）处理后煤样FTIR分析表明，部分含氧官能团、脂肪烃、氢键等发生了变化，处理后煤样芳香聚合程度增强。.（4）随着快速加热处理温度的升高，处理时间的延长，煤样的镜质组最大平均反射率缓慢升高，反射率分布区间变宽，镜质组最大平均反射率与Vdaf呈一元线性回归： =-0.0475Vdaf+2.2543(r=0.9163＞R0.05=0.811).（5）与原煤相比，热处理后的神府煤XRD表现出衍射峰强度增强，宽度变窄，衍射峰位置向2θ较大的方向偏移，堆积高度Lc增大，芳香片层间距d减小，且抽提率低于原煤。.（6）热重分析得知， 400℃之前，失重率没有明显的变化，处理后神府煤的失重速率小于原煤的失重速率，峰值较原煤低；高温热台显微镜观察发现，低温热解不能明显促进神府煤中胶质体析出。.（7）快速热处理神府煤样替代气煤，所炼制焦炭M25有所改善，光学各向异性组织含量（OTI值）有所增加，反应性降低，M10略有下降。.（8）煤快速热解焦油的主要组成包括芳烃（以单环到三环为主）、脂肪烃（C11～C22）、含氧化合物（主要为酚类及呋喃）及少量含氮化合物和含硫化合物，其中芳香烃的相对含量最高。.（9）基于ReaxFF力场在ADF软件中对优化后的模型进行1400～2600 K的热解计算。此外，课题还进行了神府煤热解产物的催化转化研究。