P_2O_5 Solubility Behavior and Resource Utilization of P-Bearing Slag

摘要

In order to recycle the phosphorus in P-bearing steelmaking slag and make it used as slag phosphate fertilizer, the citric acid solubility of P-bearing steelmaking slag was researched. The research results show that the citric acid solubility of P-bearing steelmaking slag is decreased with the increasing of P_2O_5 and Fe_2O_3 content for the CaO-SiO_2-Fe2O_3-P_2O_5 slag system. Added CaF_2 into slag can easily form the fluorap-atite (Ca5(PO_4)_2F) that can't be dissolved in 2% citric acid solution, which makes citric acid solubility of the slag decreased obviously. And added MgO, MnO or Na_2O into slag can prevent the precipitation of β-Ca_3(PO_4)_2 phase with low citric acid solubility, which makes the citric acid solubility of slag increased. While for the CaO-SiO_2-Fe2O_3-P_2O_5-X (MgO, MnO or Na_2O) slag system, MgO and MnO in slag mainly enters into RO phase, which has no effect on the phosphorus existence form in slag and has little influence on citric acid solubility of the slag. The Na_2O in slag changes the phosphorus existence form in slag, but the generated Na_2Ca_4(PO_4)_2SiO_4 and Na_3PO_4 also have good citric acid solubility, which also has little effect on citric acid solubility. Al_2O_3 and TiO_2 modification only increases the phosphorus content in phosphorus-rich phase, does not change the phosphorus existence form in slag, which makes the citric acid solubility increased slightly. While SiO_2 modification prevents the precipitation of β-Ca_3(PO_4)_2 phase with low citric acid solubility, which makes citric acid solubility of the slag increased significantly. The modified slag without fluoride makes the citric acid solubility increased to 95% and meets the requirement of producing slag phosphate fertilizer.