LAUSR

The behavior of phosphorus-bearing minerals is characterized from coking coals to the feed coke and the blast furnace (BF) coke using scanning electron microscope and thermodynamic calculations. In coals, they are represented mostly by apatite (major phase, used for thermodynamic calculations), crandallite, gorceixite, goyazite, monazite and xenotime. Apatite fully transforms to Ca4P2O9 and Ca3P2O8 at coking temperatures. In the samples of BF coke, phosphorus-bearing phases are 5-30 μm in size. In the case of a closed system (inside pieces of coke, no gas), phosphorus is presented in the BF in the form of Ca4P2O9 and Ca3P2O8 up to 1250 °C. Above this temperature, it will be transformed to Fe3P (stable until 1495 °C). A further rise in temperature leads to the transformation of Fe3P to Fe2P (stable up to 1930 °C – tuyere level of the BF). In the case of an open system with intensive flow of BF gas, the formation of Fe3P from Ca4P2O9 and Ca3P2O8 will start at 1178 °C. The Fe2P will appear near 1494–1495 °C, and after that it will go to a molten state.