煤中典型矿物在高温下演变规律

Evolution law of typical minerals in coal under high temperature

煤中典型矿物可以分为6种:黏土矿物、硫化物、磷酸盐、碳酸盐、硫酸盐和其他矿物。煤中矿物在升温过程中的演变过程对煤灰黏温特性影响较大,因此煤中矿物构成对煤炭的应用范围和利用途径造成一定的影响。通过研究煤中主要矿物的构成和不同矿物组合在升温过程中的变化规律,可为气化原料煤的选择和调节气化用煤煤灰黏温特性提供参考。笔者阐述了煤中主要矿物在高温下的转化过程及其主要产物。将高岭石、伊利石、黄铁矿等8种矿物根据矿物特性分为3组,采用FactSage软件在1000~1600℃进行了模拟研究。计算过程中选择惰性气氛,每隔100℃进行一次计算,每个矿物均以1 mol的量参与计算,出现新的矿物或旧矿物消失的条件下,该温度点的矿物组成也进行模拟计算。研究结果表明,高岭石和伊利石组成的系统在1600℃时仍存在莫来石,透长石在1145℃消失,1145~1286℃生成了白榴石。黄铁矿、磷灰石、方解石、菱铁矿、石膏、石英组成系统生成的铁尖晶石在1106℃消失,羟基磷灰石在1455℃时消失。当8种矿物共存时,生成的羟基磷灰石在1285℃时消失,莫来石在1118℃时消失。1448℃后固体大部分进入熔渣。莫来石是煤中典型的耐高温矿物,当煤灰中低熔点矿物形成熔渣后,可与莫来石反应生成低温共熔物,降低了煤灰中固体物质的含量,有利于改善煤灰黏温特性。

Typical minerals in coal can be divided into six types:clay mineral,sulfide,phosphate,carbonate,sulfate and other minerals.The evolution process of minerals in coal under the temperature increasing process has big effect on viscosity-temperature characteristics of coal ash,therefore,the minerals constitution has certain effect on application range and utilization path of coal.Through analyzing the main minerals constitution in coal and variation low of different minerals groups under the temperature increasing process,the reference of gasification raw coal selection and viscosity-temperature characteristics adjustment of gasification coal ashcould be provided.In this paper,the conversion processof main minerals in coal under high temperature and the main product of process were demonstrated.8 kinds of minerals such as kaolinite,illite and pyrite were divided into 3 groups according to their mineral characteristics,The simulation study was carried outrespectively by utilizing the FactSage software in the temperature range of 1000~1600℃.The inert atmosphere was selected in calculation process,and the calculation was done once every 100℃,and every mineral was calculated as amount of 1 mol.When a new mineral appeared,or an old mineral disappeared,the minerals constitution at this temperature was calculated as well.The results show that,in the system which is composed of kaolinite and illite,the mullite still exists under the temperature of 1600℃,the sanidine disappears at 1145℃,and the leucite is generated in 1145-1286℃.Hercynite generated in the system which is composed of pyrite,apatite,calcite,siderite,gypsum and quartz disappears at 1106℃,the hydroxyapatite disappears at 1455℃.When these 8 kinds of mineralsallcoexist,the hydroxyapatite generated disappears at 1285℃,the mullite disappears at 1118℃.After 1448℃,most of solid entersinto the slag.Mullite is a typical refractory mineral in coal,and when the low melting mineral in coal ash becomes the slag,it can react with mullite to generate the low temperature eutectic,and the solid matter content can be reduced,which is good at improving the viscosity-temperature characteristics.