Study on viscosity-temperature characteristics of high Si/Al coal ash
ZHANG Yunpeng,DING Hua, BAI Xiangfei
神东矿区煤灰分较低,矿物组成的波动对煤灰黏温特性影响较大,尤其是高硅铝比煤在高温下黏度普遍偏高,造成气化过程中堵渣问题严重。通过浮沉试验,利用扫描电镜定量分析了神东矿区煤中主要矿物组成,利用高温煤灰黏度测定仪测得煤灰黏温曲线,采用FactSage7.3以煤灰成分为基础对其进行了黏温特性模拟。结果显示:神东矿区样品矿物组成主要是伊利石型黏土矿物(相对质量分数为20%~70%,下同)、方解石(6%~34%)、黄铁矿(2%~10%)、菱铁矿(3%~50%),存在部分碎屑成因石英(6%~24%)与伊利石共生;伊利石含量高且部分伴生石英造成样品硅铝含量及硅铝比高,煤灰成分中硅铝相对质量分数为50%~75%,硅铝比为2.3~3.1,这是导致神东煤灰黏度较大的主要原因;样品中方解石是主要的含钙矿物,填充于煤的裂隙或有机质组分中的结构孔隙中,由于高温下钙离子对熔体网络的解聚和破坏作用,所以钙含量较高会导致黏度相对较低;另外,铁系矿物主要是硫化物矿物黄铁矿和碳酸盐矿物菱铁矿,铁含量相对较高导致较多二价铁离子与6个氧原子连接形成八面体结构致使网络结构松散,也会在一定程度上降低煤灰黏度。对神东矿区4种商品煤混配后的模拟结果表明,煤灰的最佳配比质量为4∶6到7∶3,煤样配比为4.1∶5.9~8.3∶1.7能够较好地满足液态排渣气化炉的操作温度和黏度区间。
The coal ash content in Shendong Mining Area is low,and the fluctuation of mineral composition has a great influence on the viscosity-temperature characteristics of coal ash,especially the viscosity of coal with high Si/Al is generally high at high temperature,resulting in serious slag plugging problem in the gasification process. Through the float and sink analysis,the main mineral composition of Shendong Coal Mine was quantitatively analyzed by using SEM. The viscosity-temperature curve of coal ash was measured by using high temperature coal ash viscosity tester. The viscosity-temperature characteristics of coal ash were simulated by Factsage 7.3 based on its composition. The results show that:the mineral composition of samples in Shendong Mining Area is mainly illite clay mineral (20%~70%),calcite (6%~34%),pyrite (2%~10%),siderite (3%~50%),and some clastic quartz (6%~24%) coexists with illite; the high content of illite and some associated quartz result in high Si-Al content and Si/Al ratio of samples,the Si-Al content in coal ash components is 50%~75%,and the Si/Al ratio is between 2.3 and 3.1,which is the main reason for the high viscosity of the coal ash in Shendong.; calcite is the main calcium mineral in the sample,which is filled in the cracks of coal or structural pores of organic matter components. Due to the depolymerization and destruction of the melt network by calcium ion at high temperature,the high Ca content will lead to relatively low viscosity; In addition,the iron series minerals are mainly sulfide minerals pyrite and carbonate minerals siderite. The relatively high Fe content leads to more divalent iron ions connected with six oxygen atoms to form octahedral structure,resulting in loose network structure,which will also reduce the viscosity of coal ash to a certain extent. The simulation results after mixing four kinds of commercial coals in Shendong Mining Area show that the optimal coal ash ratio is between 4∶6 and 7∶3,and the coal sample ratio is between 4.1∶5.9 and 8.3∶1.7,which can better meet the operating temperature and viscosity range of liquid slag discharge gasifier.
Shendong Coal; coal ash viscosity; Factsage; gasification; viscosity temperature characteristics
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会