Behavior of phosphorous transfer from CaO-FetO-P 2O5(-SiO2) slag to CaO particles

Abstract

Lime particles (0.5 to 1 mm) were added by dropping to CaO-Fe tO-P2O5 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 2O5 and 4CaO · P2O5 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-FetO slag obtained at temperatures between 1 400 and 1 570°C are higher than those between 2CaO · SiO2-3CaO · P2O5 solid solution and CaO-SiO2-Fet0 slag. Lime particles (0.3 to 0.5 mm) are added to CaO-SiO2-FetO-P2O 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 · P2O5 solid solution layer is formed on the surface of a CaO particle and thereafter the CaO-FetO slag layer is formed between a CaO particle and 2CaO · SiO 2-3CaO · P2O5 solid solution layer which is surrounded by CaO-SiO2-FetO-P2O5 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. © 2006 ISIJ.