Solubility and Activity of Iron Oxide in Solid Solutions between Ca₂SiO₄ and Ca₃P₂O₈ at 1573 K

Abstract

Towards better understanding of fundamental dephosphorization slags of the FeO-CaO-SiO 2 -P 2 O 5 quaternary system, this study aimed at clarifying the thermochemical properties of iron oxide in Ca 2 SiO 4 -Ca 3 P 2 O 8 solid solutions. The solubility and activity of FeO in the solid solutions coexisting with CaSiO 3 at 1 573 K were determined by SEM-EDX analysis and a gas equilibrium method, respectively. Based on the present experimental results, the phase relationships could be explained that the solid solution of high FeO solubility coexists with CaSiO 3 and liquid slag of low FeO content, while the solid solution of low FeO solubility coexists with CaO and liquid slag of high FeO content.

Effect of Iron Oxide Dissolution on Thermochemical Property of Solid Solution between Ca₂SiO₄ and Ca₃P₂O₈ at 1573 K

“…1 was the same as that in the preceding study by T. Saito et al 10) for comparison. The compositions of Samples B to D were identical to those in the previous work, in which the FeO activities were measured in <C2S-C3P-W2S>SS + CS 35) .…”

“…The details of the procedure have already been reported in the previous study 35) . Hence, only a brief description is given in this paper.…”

“…The concentrations of phosphorus in initial metals were set to zero or high values, while those of iron were the equilibrium values calculated from Eqs. ( 4), (17), and ( 19) with the FeO activities given in Table 2 35) . Phosphorus contents in alloys without initial P would increase while those with initial high -P would decrease, which corresponds to Reaction (5) proceeding toward left or right hand, respectively.…”

“…The standard states of 𝑎 CaO and 𝑎 SiO 2 are taken to be pure solid CaO and SiO2, respectively. The activities of PO2.5 and FeO are expressed as 𝑎 PO 2.5 = (𝑎 P 2 O 5 ) 0.5 (35) dlog𝑎 PO 2.5 = 0.5 dlog𝑎 P 2 O 5 (36) 𝑎 FeO = 𝛾 FeO ⋅ 𝑋 FeO (37) dlog𝑎 FeO = dlog𝛾 FeO + dlog𝑋 FeO Fig. 8 = dlog𝛾 FeO + log 𝑒 𝑋 FeO d𝑋 FeO (38) , where 𝛾 FeO is the activity coefficient of FeO.…”