山西三高粉煤煤灰不均匀熔融规律及灰熔聚流化床结渣机理研究

Gasification is the fundamental technique of clean utilization of coal. Pressurized ash agglomerating fluidized bed gasification technology is most adaptable to Shanxi coal with high ash content, high sulfur content and high fusibility temperature. But it still has difficulties such as high carbon content in fly ash, low operation rate and low capacity. Based on our previous work, we found that the uneven fusibility within coal ash is why ST is not well relevant to practical slagging problem. In this project, it is proposed that coal power is separated with flotation into different fractions according particle size and density. In each fraction the type, content and chemical composition of minerals are analyzed with optical microscopy, SEM, XRD and XRF. The distribution of Fe, K and Na are analyzed with 13C NMR and XRF. The formation of eutectic mixture under the condition of pressurized ash agglomerating fluidized bed gasification is studied with High temperature quenching method. In the last, the slag on the hearth and wall of pressurized ash agglomerating fluidized bed is analyzed. All the data are compared and related, so that the slagging mechanism can be deduced and an integrated slagging theory can proposed, which will be a sound base for saving the difficulties in the utilization of Shanxi coal with high ash content, high sulfur content and high fusibility temperature.

气化是煤炭洁净加工利用的源头技术，灰熔聚流化床煤气化工艺更适合山西三高煤种，但还存在飞灰含碳量高、气化炉运转率低和处理能力低等问题，这些都和煤灰熔融性密切相关。本项目组前期工作发现，用ST反映炉膛结渣趋势与实际情况不符根本原因是煤灰不均匀熔融。本研究提出用选矿法先按粒度和密度对粉煤进行分离，用光学显微镜、SEM、XRD、XRF等方法测定矿物质种类、含量和化学成分随粒度和密度的定量分布规律；将各级别粉煤模拟加压气化条件进行灰熔融性AFT和TMA研究，掌握煤灰熔融性随粒度和密度的不均匀分布规律；用13C NMR、XRF研究粉煤中易熔成分铁、钾、钠的不均匀分布规律；用高温淬冷法研究粉煤中低共熔物的形成规律；最后，对灰熔聚流化床炉膛结渣、炉壁挂渣进行分析测试，并和上述数据进行对应分析，掌握矿物质对粉煤灰熔聚流化床气化结渣影响机理，构建完整的结渣理论，为解决山西三高煤种综合利用难题奠定基础。

灰熔聚流化床煤气化是山西“三高”煤一个有前途的加工利用方法，但存在飞灰含碳量高、气化炉运转率低和处理能力低等问题。本课题采集了山西晋城、大同煤，定量研究了矿物含量和组成、熔融性以及粒径随粒度和密度的微观不均匀分布规律，构建了灰熔聚流化床结渣机理。..将煤样破碎到6 mm以下，筛分为0.5-6.0 mm四个粒度级别，发现随着粒径增大灰分含量增加，但化学组成和矿物组成没有明显变化，灰熔融性也没有显著变化。将煤样进一步粉磨到0.2mm以下，筛分为45-105 μm六个粒径范围，发现化学组成随粒度发生明显分化，都呈现出随着粒度的增大SiO2 、Fe2O3含量增大， Al2O3、CaO和SO3降低的趋势；灰熔融温度都呈现出随着粒度增大降低的趋势。..采用有机重液对磨细到0.2mm以下煤样进行浮沉分离，发现山西煤粉密度分布在1.3-2.0 g•cm-3之间，由于粘土、石英、黄铁矿、方解石等矿物和有机质结合规律的不同，呈现出随着密度提高SiO2、Fe2O3、CaO、SO3不断升高、Al2O3含量不断降低的变化规律。煤粉中矿物质含量及矿物质种类在煤粉中不均匀分布，还表现为煤灰熔融温度随密度提高而下降的规律。.山西煤变质程度高，易熔成分钾、钠含量都不高，随粒度、密度变化规律不明显，而铁主要以硫铁矿形式存在于高密度煤粉中。随着受热温度提高，煤灰中残留的S含量下降，1300 oC下各子样中的硫几乎接近于零，硫对高熔点山西煤的灰熔融性是没有影响的。.煤灰颗粒大小对结渣也有影响。研究发现，山西三高煤粉中低密度子样灰分粒径最小，中等密度略大，而高密度子样中灰分颗粒最大。.实际锅炉结渣是一个受煤灰熔融性、煤灰颗粒大小、气流温度和流场等多种因素影响的复杂过程，灰熔聚流化床结渣是煤中矿物质在煤粉中矿物质不均匀分布的结果。