Chemical transformation of sodium species during direct liquefaction of a sodium-rich Zhundong coal under different atmospheres and CO2 gasification of the direct coal liquefaction residue
Chemical transformation of sodium species during direct liquefaction of a sodium-rich Zhundong coal under different atmospheres and CO2 gasification of the direct coal liquefaction residue
复制标题
富钠准东煤在不同气氛下直接液化过程中钠形态的化学转化及煤直接液化残渣的CO2气化
DOI：
10.1016/j.fuel.2017.10.119
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发表时间：
2018
期刊：
影响因子：
7.4
通讯作者：
Li Wen
中科院分区：
文献类型：
--
作者：
Li Xiao;Bai Zong-Qing;Li Wen
准东煤田位于中国西北部，具有矿物质含量低、全硫含量低等特点。准东煤中还含有大量的钠离子，这是准东煤有效利用的一个障碍。为了更好地了解钠物种在煤直接液化（DCL）过程中的详细行为和转化机理，研究了不同液化气氛下ZDC中钠物种的化学转化。由于煤直接液化残渣（DCL）的气化通常用于生产合成气，以补偿DCL的成本，因此也考察了富钠DCL的CO2气化反应性。结果表明，H2和供氢溶剂对ZDC的直接液化都是必不可少的。在H2气氛下，钠离子在二氢呋喃中的保留率均略低于N2气氛下的保留率。同时，在H2气氛下，产生更多的CO2。DCL过程中钠形态的转化与大气环境密切相关，在H2气氛下，交换性钠形态转化较多。此外，发现硝酸钠是ZDC中的水溶性钠物质之一，并且含钠硅酸盐可以在高温下形成。更重要的是，水溶性的钠物种被证明是具有催化作用的二氧化碳气化反应的DPO4。通过详细计算，建立了水溶性钠物种含量与反应性指数之间的定量线性方程，可用于精细预测ZDC衍生D2O3的气化反应性。
The attractive Zhundong coalfields located in the Northwestern PR China are featured by many high qualities, such as low contents of mineral matters and total sulfur. However, a significant amount of sodium species are also embedded in the Zhundong coals (ZDC), which has been a barrier for efficient utilization of them. In this work, to better understand the detailed behaviors of sodium species and the transformation mechanisms during direct coal liquefaction (DCL), chemical transformation of sodium species in a ZDC under different liquefaction atmospheres was investigated. As gasification of the direct coal liquefaction residue (DCLR) is commonly used to produce syngas that compensates for the cost of DCL, CO2 gasification reactivity of sodium-rich DCLR was examined as well. The results show that both H-2 and hydrogen-donor solvents are essential for direct liquefaction of ZDC. Under H-2 atmosphere, retention ratios of sodium species in DCLR were all slightly lower than those under N-2 atmosphere. In the meantime, more CO2 were produced under H-2 atmosphere. As for transformation of sodium species during DCL, it is suggested to be closely related with the atmosphere, since more exchangeable sodium species were converted under H-2 atmosphere. Additionally, sodium nitrate was found as one of the water-soluble sodium species in ZDC and sodium-containing silicates could be formed at high temperatures. More importantly, the water-soluble sodium species in DCLR are proved to have catalytic effects on CO2 gasification reactivity of DCLR. Through careful calculations, a quantitative linear equation has been established between the water-soluble sodium species content and the reactivity index, which can be used to finely predict gasification reactivity of DCLR derived from ZDC.