Thermodynamic study of Multi-Component Calcium Ferrite

以试剂级粉末为原料，合成了三种成分不同的季铁氧体钙，研究了样品在CO-CO_2气体混合物中的还原顺序和平衡。(1)将三种不同化学成分的样品在1300℃的温度下在空气中烧制1小时。组成矿物鉴定结果表明，合成样品大部分为季型铁酸钙。(2)含CaO、SiO_2和Al_2O_3的磁铁矿（‘Fe_3O_4‘）和浮士体（’FeO’）将季系铁酸钙还原为铁。季系铁酸钙的还原顺序与二元铁酸钙不同。(3)季铁酸钙除初始还原阶段外的还原顺序由下式给出。‘Fe_3O_4’(s)+CO(g)=3'FeO'(s)+ CO_2(g) (1)'FeO'(s)+CO(g)=Fe(s)+ CO_2(g)(2)还原季铁酸钙的平衡CO浓度高于还原纯氧化铁的平衡CO浓度。还原季铁酸钙的CO-CO_2气体组成曲线与还原氧化铁的CO-CO_2气体组成曲线基本平行。根据季铁酸钙的组成，反应(1)和(2)的平衡CO浓度的值也不同。

Three kinds of quaternary calcium ferrites, whose composition differed from each other, were synthesized from reagent grade powders and the reduction sequence and the equilibria of those samples with CO-CO_2 gas mixture were investigated and the following results were obtained.(1) Three kinds of samples having different chemical compositions were fired at 1300ﾟC for one hour in the air. The result of the identification of constituent minerals, revealed that most part of the synthesized samples consisted of quaternary calcium ferrite.(2) Quaternary calcium ferrite is reduced to iron by way of magnetite('Fe_3O_4') and wustite('FeO'), which contained CaO, SiO_2, and Al_2O_3. The reduction sequence of quaternary calcium ferrite is different from binary calcium ferrite.(3) The reduction sequence of quaternary calcium ferrite is given by the following equations except for the initial reduction stage.'Fe_3O_4'(s)+CO(g)=3'FeO'(S)+CO_2(g) (1)'FeO'(s)+CO(g)=Fe(S)+CO_2(g) (2)The equilibrium CO concentrations for the reduction of quaternary calcium ferrite were higher than those for the reduction of pure iron oxides. The lines of temperature-equilibrium CO-CO_2 gas composition for the reduction of quaternary calcium ferrite were in approximately parallel with those for the reduction of iron oxides. Depending on the composition of quaternary calcium ferrite, the values of the equilibrium CO concentration for the reactions (1) and (2) varied.