高温气化条件下Na_2O对煤灰中矿物质演化行为的影响

利用XRD和FT-IR考察了高温弱还原气氛下Na_2O对两种硅铝含量不同的煤灰中矿物质组成的影响,揭示了Na_2O影响煤灰熔融特性的本质。通过Fact Sage计算了高温下矿物质反应的ΔG,探讨了Na_2O影响煤灰中矿物质组成的机理。结果表明,Na_2O对煤灰矿物质组成的影响与原煤灰的硅铝含量密切相关。硅铝总含量82.89%的煤灰,Na_2O含量为5%-20%时,钠长石和霞石的生成是煤灰熔融温度降低的主要原因;当Na_2O含量大于20%时,导致煤灰熔融温度降低的原因是霞石的生成。硅铝总含量47.85%的煤灰,Na_2O含量小于10%时,没有含钠矿物质生成;当Na_2O含量大于10%时,主要生成菱硅钙钠石、青金石和含钠的硅铝酸盐矿物,导致煤灰熔融温度降低。Fact Sage计算表明生成含Na矿物质反应的ΔG较小,其在高温下更容易发生。

Effect of Na2O on mineral transformation of coal ash under high temperature gasification condition

In order to reveal the mechanism of Na₂O influence on ash fusion temperatures (AFTs), effect of Na₂O on mineral transformation of two coal ashes with different SiO₂+Al₂O₃ levels were investigated by XRD and FT-IR under reducing atmosphere at high temperature. Thermodynamic software package FactSage was used to calculate the ΔG of reactions between minerals to reveal the mechanism of Na₂O influence on mineral transformation. It is found that the effect of Na₂O on mineral compositions depends on SiO₂+Al₂O₃ levels of coal ash. For ash with 82.89% SiO₂+Al₂O₃ while Na₂O content is 5%-20%, albite and nepheline are formed, leading to a decrease of AFTs. However, only nepheline is formed when Na₂O content is higher than 20%. For ash with 47.85% SiO₂+Al₂O₃, when Na₂O content is less than 10%, no Na-containing mineral is observed. When Na₂O content is higher than 10%, Na-containing minerals such as combeite, lazurite and sodium aluminium oxide are formed, resulting in a decrease of AFTs. Furthermore, FactSage results reveal that Na-containing mineral is easily formed at high temperature due to low ΔG of the reactions.