准东煤热解过程中不同赋存形态钠变迁规律的研究

利用加压管式反应器对准东煤进行了一系列热解实验,并采用溶剂逐级萃取的方法研究了煤中各赋存形态钠在不同热解温度、停留时间及其压力下的变迁规律。研究发现,原煤中钠主要是以水合离子态和钠长石的形式存在,有机态钠含量较少。在500-700℃时,随着挥发分的释放,水可溶性钠结合到煤焦的碳基质上,转化为盐酸可溶但水不可溶性的钠,少量有机钠会挥发至气相中。在700-900℃时,可溶性钠与高岭土等矿物质反应生成盐酸不可溶性钠。1 000℃时,钠的挥发量显著增加;部分高岭土与方解石分解生成的氧化钙反应生成钙长石,抑制了可溶性钠与高岭土之间的反应。煤中各形态钠的变迁主要发生在热解初期,与挥发分的释放同时进行。提高热解压力对钠的变迁行为没有影响。

Release and transformation behaviors of sodium species with different occurrence modes during pyrolysis of Zhundong coal

A series of pyrolysis experiments on Zhundong coal were conducted by using a pressurized tube reactor. Under different pyrolysis temperature, residence time and pressure, the release and transformation behaviors of sodium species with different occurrence modes were investigated by the method of sequential chemical extraction. The results indicate that sodium species are mainly in the form of hydrated ion and albite, and organic forms are quite less. At 500-700℃, water-soluble sodium would be combined with char matrix, forming hydrochloric acid-soluble but water-insoluble sodium. At 700-900℃, soluble sodium could react with minerals such as kaolin, forming insoluble aluminosilicate. At 1 000℃, release of sodium became intense; part of kaolin might be involved into reactions with lime, which inhibited its reactions with soluble sodium. Besides, it is found that release and transformation behaviors of sodium mainly take place at the initial stage of pyrolysis along with release of volatiles and raising pressure has negligible influence on those behaviors.