Thermodynamic Measurement of Di-calcium Phosphate

Abstract

The thermodynamic properties of the CaO-P 2 O 5 system are important to develop an effective refining process in the iron and steel industry. In this study, the thermodynamic properties of (CaO) 2 P 2 O 5 were investigated because the properties are necessary to develop a new dephosphorization process. The vapor of gaseous phosphorus and phosphorus oxide in equilibrium with a mixture of (CaO) 2 P 2 O 5 and (CaO) 3 P 2 O 5 at 1373 K to 1498 K (1100°C to 1225°C) were detected directly as an ion current by double Knudsen cell mass spectrometry. Comparing the ion currents with those from a mixture of Al 2 O 3 P 2 O 5 and Al 2 O 3 , which is used as a reference mixture in this study, the Gibbs energy change of the following reaction was calculated:

The influence of annealing conditions on the Ca/P ratio and phase transformations in bulk calcium phosphates

“…We cannot clarify the exact chemical formulas of evaporated volatile species, however, this information could be obtained by employing thermal analysis coupled with a mass analyzer. According to Nagai et al , 22 phosphates could be removed in the form of P 2 , PO, and PO 2 . Moreover, the obtained results suggest that α-TCP can be prepared by one-step annealing of widely commercially available single-source precursors.…”

Conversion of Mill Scale Waste into Valuable Products via Carbothermic Reduction

“…Therefore, low activity of oxygen in the metal is expected leading to appropriate conditions for the removal of the sulphur and desulphurization of the metal, as it is indicated from (8). On the contrary, these conditions encourage rephosphorization process and consequently the phosphorus content in the metal increases as the reducing agent increases, as it is indicated from (11).…”

“…Dephosphorization and desulfurization of hot metal are known to proceed under different conditions. The most popular method of desulphurization is removal of sulphur from metal to the basic reducing Journal of Metallurgy 5 slag, while the most popular dephosphorization is removal of phosphorous from metal to the basic oxidizing slag, as indicated from the following chemical equations [9][10][11]:…”

Predicting Melt Formation and Agglomeration in Fluidized Bed Combustors by Equilibrium Calculations

“…Reactions (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) are incomplete to estimate the full speciation of K, Ca, Mg, P and Si. Calcium phosphates are for instance not limited to Ca(PO3)2, Ca2P2O7 and Ca3(PO4)2, as can be observed in the CaO-P2O5 binary phase diagram [51] (see Figure 6). Furthermore, Na is not included in this discussion, because its concentration is in most biofuels much lower than that of K (Table 1).…”

“…In this case, after formation of Ca(PO3)2, the excess of P2O5 reacts to CaP4O11 and Ca2P3O17, as can be observed in the CaO-P2O5 binary phase diagram in Nagai et al [51]. These components were not included in the calculations, because thermodynamic data were lacking.…”