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为了了解磷铁在真空蒸馏过程中的物相变化规律,本文通过热力学计算,得到磷铁在压力为10~10~5Pa下的化学反应吉布斯自由能和分解反应温度的关系。计算表明磷铁的分解反应主要分三个阶段:(1209~1350 K)FeP生成Fe、Fe_3P和P_2;(1350~1693 K)主要是Fe_2P发生分解生成P_2、Fe_3P和Fe;当温度高于1693 K时,Fe_3P开始分解生成P_2和Fe。并在1373,1473,1573,1673 K等温度条件下,恒温60 min,对磷铁进行了真空蒸馏实验,考察其残渣物相及元素含量变化。结果表明,当温度由1373升高到1673 K时,磷不断减少,由16.3%降到了10.75%,磷铁物相变化为FeP→Fe_2P-Fe_3P→Fe,与热力学计算结果相符。实验证明,可以通过真空蒸馏的方法回收磷铁副产中的磷。
In order to understand the phase transformation law of the iron and phosphorus during vacuum distillation, the relationship between Gibbs free energy and decomposition temperature of the chemical reaction of phosphorus and iron under the pressure of 10 ~ 10 ~ 5Pa was obtained by thermodynamic calculation. Calculations show that the decomposition reaction of ferrophosphorus is mainly divided into three stages: (Fe2O3, Fe3P and P_2) from (1209 ~ 1350 K); (1350 ~ 1693 K) mainly decomposes Fe_2P to produce P_2, Fe_3P and Fe; when the temperature is higher than 1693 When K, Fe 3 P began to decompose to generate P 2 and Fe. Under the isothermal conditions of 1373, 1473, 1573 and 1673 K, the iron and phosphorus were vacuum-distilled for 60 min to investigate the changes of the phase and the elemental content of the residue. The results showed that the phosphorus decreased continuously from 16.3% to 10.75% when the temperature increased from 1373 to 1673 K, and the phase change of the ferrophosphorus to FeP → Fe_2P-Fe_3P → Fe was consistent with the thermodynamic calculation. Experiments show that phosphorus by-product of phosphorus and iron can be recovered by vacuum distillation.