Thermodynamics of Phosphate and Phosphide in BaO-BaF<SUB>2</SUB> Melts

Effect of Atmosphere and Slag Composition on the Evolution of PH3 Gas during Cooling of Reducing Dephosphorization Slags

“…20) Consequently, when the CaO content are 20 and 25 mass%, Fliquid was estimated to be 0.99 and 0.93, respectively. Figure 2 shows the effect of CaO content in the CaOCaF2 flux on the distribution ratio of phosphorous at 1 823 K. Under the highly reducing conditions, phosphorous is expected to dissolve into the flux as phosphide ions as follows: [4][5][6][7][8][9][10][11] .............. (7) ...... (8) where and are the activity and the activity coefficient of the phosphide ions in the slag phase, respectively, aP and fP are the activity and the activity coefficient of phosphorous in the SiMn alloy phase, respectively, is the oxygen partial pressure, and is the activity of free oxygen, i.e. the basicity of the slag.…”

“…However, the conventional oxidizing dephosphorization technique is not applicable to manganese alloys because silicon or manganese will be oxidized before phosphorous under oxidizing conditions. [4][5][6][7][8] Therefore, the dephosphorization should be carried out under a strongly reducing atmosphere to produce a low phosphorus manganese alloys. The mechanism of reducing dephosphorization using lime-based highly basic fluxes has been reported by several authors, [4][5][6][7][8][9][10][11] and recently reviewed and experimentally confirmed by the present authors in previous study.…”

“…[4][5][6][7][8] Therefore, the dephosphorization should be carried out under a strongly reducing atmosphere to produce a low phosphorus manganese alloys. The mechanism of reducing dephosphorization using lime-based highly basic fluxes has been reported by several authors, [4][5][6][7][8][9][10][11] and recently reviewed and experimentally confirmed by the present authors in previous study. 12) However, because the calcium phosphide (Ca 3 P 2 ), which is a reaction product of the reducing dephosphorization mechanism, is very active when it is exposured to moisture, the hazardous phosphine gas (PH 3 ) evolves.…”

Thermodynamic Assessment of Liquid Mn–Fe–Si–C–Ca–P System by Unified Interaction Parameter Model

“…There were also some reports about the reducing de-P mechanism using CaO-based slags. [20][21][22][23][24][25][26] In order to get a full understanding about the thermodynamics of the reducing de-P process, it is of great importance to know the activities of different components involved in the manganese ferroalloys, such as Ca, P, Si, Mn and C. Efforts have been devoted to describe the thermodynamic properties of Mn-based melts. A large amount of experimental works has been done for the systems Mn-Fe, [27][28][29][30][31][32][33] Mn-Si, [34][35][36][37][38][39][40][41][42] Mn-C, 35,36,[43][44][45][46][47][48][49][50][51] Mn-Fe-Si, 52,53) Mn-Fe-C, [45][46][47]49,[54][55][56][57][58][59][60] Mn-…”

Conversion of Calcium Phosphide to Calcium Phosphate in Reducing Dephosphorization Slags by Oxygen Injection

“…However, the conventional oxidizing dephosphorization technique is not applicable to manganese alloys because silicon or manganese will be oxidized before phosphorous under oxidizing conditions. [4][5][6][7][8] Therefore, the dephosphorization should be carried out under a strongly reducing atmosphere to produce a low phosphorus manganese alloys.…”