P2O5 Solubility Behavior and Resource Utilization of P-Bearing Slag

Abstract

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 P2O5 and Fe2O3 content for the CaO-SiO2-Fe2O3-P2O5 slag system. Added CaF2 into slag can easily form the fluorapatite (Ca5(PO4)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 Na2O into slag can prevent the precipitation of β -Ca3(PO4)2 phase with low citric acid solubility, which makes the citric acid solubility of slag increased. While for the CaO-SiO2-Fe2O3-P2O5-X (MgO, MnO or Na2O) 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 Na2O in slag changes the phosphorus existence form in slag, but the generated Na2Ca4(PO4)2SiO4 and Na3PO4 also have good citric acid solubility, which also has little effect on citric acid solubility. Al2O3 and TiO2 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 SiO2 modification prevents the precipitation of β -Ca3(PO4)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.

Study of the State of Industrial P2O5‐Containing Slags Relevant to Steelmaking Processes Based on a New Thermodynamic Database Developed for CaO–FeOx–P2O5–SiO2–MnO–MgO–Al2O3 Slags − Part I: Ternary and Lower Order Systems

“…Since the initial phosphorous content of the hot metal in such processes was higher than 1 wt% at the time, the final P 2 O 5 contents in slags typically ranged between 10 and 20 wt %. Recently, increased attention has being drawn again to this system due to the expected increase in the Phosphorous content of iron ores and subsequently, in the P 2 O 5 contents of the final slags . It was reported that when the Phosphorous content of hot metal is equal to 0.3 wt% or higher (which would be the case when high phosphorous iron ores are used), the P 2 O 5 content of the slag will be higher than 10 wt% .…”

“…Recently, increased attention has being drawn again to this system due to the expected increase in the Phosphorous content of iron ores and subsequently, in the P 2 O 5 contents of the final slags . It was reported that when the Phosphorous content of hot metal is equal to 0.3 wt% or higher (which would be the case when high phosphorous iron ores are used), the P 2 O 5 content of the slag will be higher than 10 wt% . For a proper evaluation of the state of phosphorous containing industrial slags, it is thus important to study the state of the CaO–FeO x –P 2 O 5 oxide system as well as the higher order systems based on it.…”

“…However, a successful refining of high phosphorous hot metal would be advantageous from both an economical and ecological perspective: The slag produced would be high in P 2 O 5 and could thus be used as an additional source of phosphrous . This has led to increased attention in studying the separation possibilities of phosphorous from P 2 O 5 ‐containing slags . In this context, the availability of a thermodynamic database suitable for investigating both low and high phosphorous slags contributes to the evaluation of the potential as well as pointing out the limitations of phosphorous removal for different starting conditions and blowing strategies.…”

Effects of Acid and Na₂SiO₃ Modification on the Dissolution Behavior of 2CaO·SiO₂-3CaO·P₂O₅ Solid Solution in Aqueous Solutions

“…J. Diao et al 9) and L. Lin et al 10) studied the solubility of P 2 O 5 from synthesized steelmaking slag in 2% citric acid. The dissolution ratio of P increased and reached 96% when Na 2 CO 3 was added to the slag during synthesis, which resulted from Na 2 Ca 4 (PO 4 ) 2 SiO 4 formation.…”

Extraction of Phosphorus from Steelmaking Slag by Selective Leaching Using Citric Acid

“…Recently, citric acid, which is often used to test the fertility of phosphate fertilizer and steelmaking slag, 15,16) has been shown to dissolve P more effectively than nitric acid by suppressing the precipitation of HAP. 17) This suppression occurs because the Ca cations form complexes with citrate in aqueous solution, decreasing the concentration of dissolved Ca below the solubility of HAP.…”