Behavior of Phosphorous Transfer from CaO-FetO-P2O5(-SiO2) Slag to CaO Particles

Abstract

Lime particles (0.5 to 1 mm) were added by dropping to CaO-Fe t O-P 2 O 5 slag at 1 400°C, followed by stirring and the reaction products near a CaO particle/slag interface were determined by a microprobe analysis (EPMA-EDX). The 3CaO · P 2 O 5 and 4CaO · P 2 O 5 phases were crystallized depending on the amount of added CaO particles which are rapidly dissolved after the contact with a molten slag. The phosphorous distribution ratios between calcium phosphates and CaO-Fe t O slag obtained at temperatures between 1 400 and 1 570°C are higher than those between 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and CaO-SiO 2 -Fe t O slag. Lime particles (0.3 to 0.5 mm) are added to CaO-SiO 2 -Fe t O-P 2 O 5 slag at 1 400°C and the reaction products near a CaO particle/slag interface are determined by EPMA-EDX. The 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution layer is formed on the surface of a CaO particle and thereafter the CaO-Fe t O slag layer is formed between a CaO particle and 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution layer which is surrounded by CaO-SiO 2 -Fe t O-P 2 O 5 slag. It is also experimentally confirmed that the meso-phase slag refining is superior to conventional slag refining and the discrepancy between the theoretical and experimental results obtained by the meso-phase slag refining is discussed.KEY WORDS: phosphorous distribution ratio; lime; calcium phosphate; dicalcium silicate.again and heated at 1 600°C for 24 h, followed by He quenching.CaO-Fe t O and CaO-Fe t O-P 2 O 5 slags: The CaO powder produced by the aforementioned method, reagent grade Fe t O and 3CaO · P 2 O 5 were well mixed and the mixture was melted at 1 420°C under Ar flowing atmosphere in an Fe crucible, followed by stirring with an Fe rod. The melt was quenched by using a water-cooled sandwich type Cu plates. The present slag compositions D1 and D2 are plotted in the CaO-Fe t O-P 2 O 5 phase diagram 8,9) shown in Fig. 1. The slag samples were ground to below 3 mm by a stainless steel ball mill. ProcedureThe CaO-Fe t O-P 2 O 5 or CaO-Fe t O slag was melted at 1 400°C in an Fe crucible under Ar flowing atmosphere (200 cm 3 · min Ϫ1) and then CaO (0.5 to 1 mm) or calcium phosphate (20 to 50 mm) particles were added by dropping into a molten slag, followed by stirring with an Fe rod. A melt was quenched by using a water-cooled sandwich type Cu plates. In the experiments carried out at temperatures above 1 500°C, a MgO crucible containing Fe was used in stead of an Fe crucible. This procedure denotes the isothermal method.In the experiments where calcium phosphate phase is crystallized during cooling, the CaO-Fe t O-5mass%P 2 O 5 slag D3 (mp 1 560°C) shown in Fig. 1 was melted at 1 600°C under Ar flowing atmosphere in a MgO crucible containing Fe. The melt was cooled to 1 570°C at 0.83°C · min Ϫ1 and held for 30 min. Then, it was cooled at 2.5°C · min Ϫ1 from 1 570 to 1 400°C, followed by quenching in water. For comparison a melt was cooled from 1 600 to 1 570°C at 0.83°C · min Ϫ1 and quenched in water after holding for 30 min at 1 570...

Reaction Behavior of P2O5 at the Interface between Solid 2CaO·SiO2 and Liquid CaO–SiO2–FeOx–P2O5 Slags Saturated with Solid 5CaO·SiO2·P2O5 at 1 573 K

“…Since many studies 1,[4][5][6][7][8][9] had confirmed that phosphorus in the liquid phase can be fixed into the 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution or compounds by CaO contained in the steelmaking slag, the idea is proposed to innovate the present refining process by promoting the transfer of phosphorus from liquid phase to solid phase for better dephosphorization. Reduction of the lime consumption and slag emission can be achieved by improving the utilization efficiency of solid CaO or 2CaO · SiO 2 phase in the steelmaking slag.…”

Estudo Da Partição Do Fósforo De Escórias De Um Forno Elétrico a Arco Através Da Termodinâmica Computacional

“…Urban, 2015) [2] Na maioria dos casos, escórias utilizadas em desfosforação são básicas e, portanto, saturadas em silicato dicálcico, 2CaO.SiO₂ (também chamado de C₂S). Sabe-se que o silicato dicálcico e o fosfato tricálcico formam uma solução sólida ao longo de uma ampla gama de composição, o 2CaO.SiO₂-3CaO.P₂O₅ (C₂SC₃P) [3]. Em seu trabalho, Campos demonstrou matematicamente que as reações de desfosforação ocorrem somente na interface entre o metal e a escória [4].…”

Effect of Na₂O on Phosphorus Enrichment and Separation in P-Bearing Steelmaking Slag

“…2,3) However, blast furnace slag and steel slag used as agricultural fertilizer and soil improvement is totally 230 000 tons in China 2010, accounts for 0.5% of total blast furnace slag and steel slag using amount, so the utilization of steel slag for fertilizer is very low.…”

“…Lu LIN, 1,2) * Yan-ping BAO, 1) Wei JIANG 3) and Qi-fan WU 3) Journals Publishing Center, University of Science and Technology Beijing, 30 Xueyuan Rd., Haidian, Beijing, 100083 China.…”