镁质贫镍红土矿热分解理论计算与实验研究

Thermal Decomposition of High-magnesium Low-nickel Laterite:Theoretical Calculation and Experimental Study

以镁质贫镍红土矿为原料,对其进行焙烧热分解实验,研究红土矿受热分解过程中的脱羟基反应与重结晶过程的物相转变。以蛇纹石热分解物相转变的实验研究为基础进行模拟结果验证,通过理论计算模拟了实验过程,以阐明镁质红土矿升温过程中的物相转变作用机制。结果表明,红土矿中主要成分是蛇纹石相(Mg_3Si_2O_5(OH)_4),升温至612℃后发生脱羟基反应,生成非晶态硅酸盐;继续加热至817℃发生重结晶反应,生成橄榄石和顽辉石相以及少量的SiO_2。通过密度泛函理论(DFT)计算Mg_3Si_2O_5(OH)_4原子的键长、态密度、密立根布居等参数,对其热分解过程进行分子动力学计算模拟。结果显示,动力学模拟条件下,蛇纹石内部羟基以氢氧根的形式直接脱离,生成非晶态硅酸盐产物,继续升温,非晶态硅酸盐中SiO_2有离解分离的趋势,参与重结晶过程,生成结晶度良好且致密的橄榄石和顽辉石相,计算模拟结果与实验结果吻合较好。

The high-magnesium low-nickel laterite was taken as raw material,the thermal decomposition experiment by calcination was carried out to study the phase transformation of dehydroxylation and re-crystallization during the thermal decomposition of laterite.Based on the experimental study on phase transformation of thermal decomposition of serpentine,the experimental process was simulated by theoretical calculation to clarify the phase transformation of magnesite laterite during heating process.The results indicated that Mg3Si2O5(OH)4 was the major ingredient of laterite,dehydroxylation reaction occurred when temperature exceeded 612℃,and amorphous silicate mineral generated.Subsequently,the recrystallization occurred when heating up to 817℃,generating peridot phase,enstatite,as well as a small amount of SiO2.By means of density functional theory(DFT),the atomic bond length,state density and Millikan population of Mg3Si2O5(OH)4 were calculated,and its molecular dynamics calculation during thermal decomposition was simulated.The results showed that under the condition of kinetic simulation,the hydroxyl groups in Mg3Si2O5(OH)4 would be separated directly in the form of hydroxyl to form amorphous silicate products.With the rising temperature,the SiO2 in amorphous silicate tended to dissociate and separate,participating in re-crystallization process and producing peridot phase and enstatite with better crystallinity.The calculation simulated results were well fitted with the experimental results.