鹼性氧氣爐 (BOF) 爐渣是煉鋼過程中不可避免的副產品之一，隨著鋼產量的增加，爐渣產生的增長率也在增加。其中大部分元素有再利用價值，可以在煉鋼過程中作為原料再利用。然而，轉爐石中磷含量高，限制了其在煉鋼過程中的循環利用。磷濃縮和積累在鐵水中，最終導致鐵脆化，因此，在不引起其他有害影響的情況下將爐渣中磷去除以提高轉爐石的循環利用是相當重要的。本研究以氯化轉爐石和兩階段還原法對轉爐石的脫磷進行可行性探討，石墨為主要還原劑，氯化鈣為氯化劑以促進鐵相還原及揮發行為，關鍵參數包括爐渣鹽基度、氯化劑劑量、二階還原劑劑量和加入的溫度，以及反應的溫度。XRF和ICP-OES用於測定爐渣元素組成，XRD鑑定結晶相，EPMA和SEM-EDS分析元素分佈圖和磷的遷移。實驗結果顯示，碳熱還原的最佳磷氣化量為添加14 wt%的C及20 wt%的SiO2，在脫磷率49.72%時，氣化量達到18.85%。爐渣的熔點隨著CaCl2的增加而降低，提升爐渣和還原劑的質傳速率，也容易形成鐵滴，在滲碳作用的效果下，同時也促進了爐渣再磷化。兩階段還原的最佳磷氣化量為添加12 wt%的CaCl2及20 wt%的SiO2，和在1350 °C下添加7 wt%的C，脫磷率為35.63%，氣化量為24.45%。發現CaCl2會先還原鐵，並且結合部分Fe形成FeCl2氣體逸散。此外1350 °C下添加的C使磷有最大脫磷率，因為爐渣中鐵含量減少，使得再磷化反應減少，以達到氣相脫磷。

Basic oxygen furnace (BOF) slag is one of the inevitable by-products of the steelmaking process, and as steel production increases the growth rate of slag production. Most of the elements have economic value and can be reused as raw materials in the steelmaking process. However, the high phosphorus contents in converter stone limits its recycling in the steelmaking process. Phosphorus concentrates and accumulates in molten iron, eventually leading to iron embrittlement, so it is important to remove phosphorus from slag without causing other harmful effects to improve the recycling of BOF slag. In this study, chlorinated BOF slags and two-stage reduction method were used to discuss the feasibility of dephosphorization of BOF slag. Graphite was used as the main reducing agent, and CaCl2 was used as the chlorinating agent to promote iron reduction and volatilization behavior. The operation parameters include basicity, chlorinating agent dosage, two-stage reducing agent dosage and temperature of addition, and reaction temperatures. The XRF and ICP-OES were used to determine the elemental compositions of the slag. The XRD can be used to identify the crystalline phase, and EPMA and SEM-EDS can be employed to analyze the elemental distribution mapping and phosphorus migration. The experimental results show that the optimum phosphorus gasification amount for carbothermic reduction is adding 14 wt% C and 20 wt% SiO2, and the gasification amount reaches 18.85% when the dephosphorization rate is 49.72%. The melting point of the slag decreases with the increase of CaCl2, which increases the mass transfer rate of the slag and the reducing agent, and also easily forms iron droplets. The occurrence of carburization also promotes the re-phosphating of the slag. The optimum phosphorus gasification amount for the two-stage reduction is the addition of 12 wt% CaCl2 and 20 wt% SiO2, followed by adding 7 wt% C at 1350 °C, the dephosphorization rate can reach 35.63% with the gasification amount of 24.45%. It is found that CaCl2 could reduce iron first, and combine with part of Fe to form FeCl2 gas to escape. Moreover, the addition of C at 1350 °C achieves the maximum dephosphorization rate of phosphorus, because the iron content in the slag is reduced, which reduces the re-phosphating reaction to proceed gas-phase dephosphorization.

Balloy, D., Tissier, J.-C., Giorgi, M.-L., & Briant, M. (2010). Corrosion mechanisms of steel and cast iron by molten aluminum. Metallurgical and Materials Transactions A, 41(9), 2366-2376.
Brooks, G., Hasan, M., & Rhamdhani, M. (2019). Slag basicity: what does it Mean? Paper presented at the 10th International Symposium on High-Temperature Metallurgical Processing.
Chang, H.-H., Chen, I.-G., Lu, K.-M., & Liu, S.-H. (2021). Effect of Heating Rate on Carbothermic Reduction and Melting Behavior of Iron Ore-Coal Composite Pellets. ISIJ International, 61(11), 2715-2723.
Chen, Z., Li, R., Zheng, X., & Liu, J. (2021). Carbon sequestration of steel slag and carbonation for activating RO phase. Cement and Concrete Research, 139, 106271.
Cheng, C., Xue, Q., Zhang, Y., Han, F., & Wang, J. (2015). Dynamic migration process and mechanism of phosphorus permeating into metallic iron with carburizing in coal-based direct reduction. ISIJ International, 55(12), 2576-2581.
Heo, J. H., Chung, Y., & Park, J. H. (2016). Recovery of iron and removal of hazardous elements from waste copper slag via a novel aluminothermic smelting reduction (ASR) process. Journal of Cleaner Production, 137, 777-787.
Heo, J. H., & Park, J. H. (2017). Thermochemical analysis for the reduction behavior of FeO in EAF slag via Aluminothermic Smelting Reduction (ASR) process: Part Ι. Effect of aluminum on Fe & Mn recovery. Calphad, 58, 219-228.
Huang, T., Liu, S.-H., & Shiau, G.-H. (2014). Effect of volatile matter content of coal on carbothermic reduction of ore/coal composite pellets packed in a tall bed. China Steel Techn. Rep, 27, 11-19.
Jiang, L., Bao, Y., Hu, X., Chen, Y., Liu, G., Han, F., . . . Wu, J. (2018). Experimental investigation on BOF slag oxidation in air. Ironmaking & Steelmaking, 46(8), 747-754.
Jiang, M.-f., Cui, Y.-y., Wang, D.-y., Min, Y., & Liu, C.-j. (2013). Effect of modification treatment for reduction of dephosphorization slag in hot metal bath. Journal of Iron and Steel Research International, 20(1), 1-6.
Jung, S. M., & Do, Y. J. (2006). Reduction behaviour of BOF slags by carbon in iron. Steel research international, 77(5), 312-316.
Jung, S. M., Do, Y. J., & Choi, J. H. (2006). Reduction behaviour of BOF type slags by solid carbon. Steel research international, 77(5), 305-311.
Kanari, N., Allain, E., Filippov, L., Shallari, S., Diot, F., & Patisson, F. (2020). Reactivity of Low-Grade Chromite Concentrates towards Chlorinating Atmospheres. Materials, 13(20), 4470.
Kanari, N., Gaballah, I., & Allain, E. (1999). A study of chromite carbochlorination kinetics. METALLURGICAL AND MATERIALS TRANSACTIONS B, 30(4), 577-587.
Kanari, N., Gaballah, I., & Allain, E. (2000). Use of chlorination for chromite upgrading. Thermochimica acta, 351(1-2), 109-117.
Kanari, N., Mishra, D., Filippov, L., Diot, F., Mochón, J., & Allain, E. (2010). Kinetics of hematite chlorination with Cl2 and Cl2+ O2: Part I. Chlorination with Cl2. Thermochimica acta, 497(1-2), 52-59.
Kim, T., & Lee, J. (2011). Recovery of Fe and P from CaO-SiO2-FetO-P2O5 slag by microwave treatment. Materials Transactions, 52(12), 2233-2238.
Krasnyanskaya, I., & Podgorodetskii, G. (2014). Removal of phosphorus from CaO-SiO2-MgO-Al2O3-P2O5 melts to the gas phase. Steel in Translation, 44(5), 345-349.
Kubo, H., Matsubae-Yokoyama, K., & Nagasaka, T. (2010). Magnetic separation of phosphorus enriched phase from multiphase dephosphorization slag. ISIJ International, 50(1), 59-64.
Kumar, V., Kumar, S., Prasad, J., Keshari, K., Ghosh, S., & Bhakat, A. K. (2017). Feasibility Study of Dephosphorization of Slag Generated from Basic Oxygen Furnace of an Integrated Steel Plant.
Li, B., Li, L., Guo, H., Guo, J., Duan, S., & Sun, W. (2020). A phosphorus distribution prediction model for CaO–SiO2–MgO–FeO–Fe2O3–Al2O3–P2O5 slags based on the IMCT. Ironmaking & Steelmaking, 47(7), 771-780.
Li, C. X., Xue, Y. K., & Wang, S. H. (2019). Fundamental Research on Gasification Dephosphorization with Coke Powder Reducing Converter Molten Slag. Paper presented at the Key Engineering Materials.
Lin, Y., Yan, B., Shu, Q., & Fabritius, T. (2021). Synergetic valorization of basic oxygen furnace slag and stone coal: Metal recovery and preparation of glass-ceramics. Waste Management, 135, 158-166.
Liu, C., Huang, S., Wollants, P., Blanpain, B., & Guo, M. (2017). Valorization of BOF steel slag by reduction and phase modification: metal recovery and slag valorization. METALLURGICAL AND MATERIALS TRANSACTIONS B, 48(3), 1602-1612.
Liu, S., He, X., Wang, Y., & Wang, L. (2021). Cleaner and effective extraction and separation of iron from vanadium slag by carbothermic reduction-chlorination-molten salt electrolysis. Journal of Cleaner Production, 284, 124674.
Luz, A., Martinez, A. T., López, F., Bonadia, P., & Pandolfelli, V. (2018). Slag foaming practice in the steelmaking process. Ceramics International, 44(8), 8727-8741.
Matsui, A., Nakase, K., Kikuchi, N., Kishimoto, Y., Takahashi, K., & Ishida, K. (2011). Phosphorus separation from steelmaking slag by high temperature reduction with mechanical stirring. TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN, 97(8), 416-422.
Mochizuki, Y., Tsubouchi, N., & Sugawara, K. (2020). Separation of valuable elements from steel making slag by chlorination. Resources, Conservation and Recycling, 158, 104815.
Monaghan, B., Pomfret, R., & Coley, K. (1998). The kinetics of dephosphorization of carbon-saturated iron using an oxidizing slag. METALLURGICAL AND MATERIALS TRANSACTIONS B, 29(1), 111-118.
Morita, K., Guo, M., Oka, N., & Sano, N. (2002). Resurrection of the iron and phosphorus resource in steel-making slag. Journal of Material Cycles and Waste Management, 4(2), 93-101.
Muraki, M., Fukushima, H., & Sano, N. (1985). Phosphorus distribution between CaO-CaF2-SiO2 melts and carbon-saturated iron. Transactions of the Iron and Steel Institute of Japan, 25(10), 1025-1030.
Nagata, K., & Bolsaitis, P. (1987). Selective removal of iron oxide from laterite by sulphurization and chlorination. International Journal of Mineral Processing, 19(1-4), 157-172.
Nakase, K., Matsui, A., Kikuchi, N., & Miki, Y. (2017). Effect of slag composition on phosphorus separation from steelmaking slag by reduction. ISIJ International, 57(7), 1197-1204.
Nakase, K., Matsui, A., Kikuchi, N., Miki, Y., Kishimoto, Y., Goto, I., & Nagasaka, T. (2013). Fundamental research on a rational steelmaking slag recycling system by phosphorus separation and collection. Journal for Manufacturing Science & Production, 13(1-2), 39-45.
Nekvasil, H., DiFrancesco, N. J., Rogers, A. D., Coraor, A., & King, P. (2019). Vapor‐deposited minerals contributed to the Martian surface during magmatic degassing. Journal of Geophysical Research: Planets, 124(6), 1592-1617.
Oh, M. K., Kim, T. S., & Park, J. H. (2020). Effect of CaF2 on phosphorus refining from molten steel by electric arc furnace slag using direct reduced iron (DRI) as a raw material. METALLURGICAL AND MATERIALS TRANSACTIONS B, 51(6), 3028-3038.
Rao, L., Dong, Y., Gui, M., Zhang, Y., Shen, X., Wu, X., & Cao, F. (2020). Growth, Stratification, and Liberation of Phosphorus-Rich C2S in Modified BOF Steel Slag. Materials, 13(1), 203.
Sano, N., Tsukihashi, F., & Tagaya, A. (1991). Thermodynamics of Phosphorus in CaO-CaF2-SiO2 and CaO-CaF2-CaCl2 Melts Saturated with CaO. ISIJ International, 31(11), 1345-1347.
Senderowski, C., Chodala, M., & Bojar, Z. (2015). Corrosion behavior of detonation gun sprayed Fe-Al type intermetallic coating. Materials, 8(3), 1108-1123.
Shen, X., Chen, M., Wang, N., & Wang, D. (2019). Viscosity property and melt structure of CaO–MgO–SiO2–Al2O3–FeO slag system. ISIJ International, 59(1), 9-15.
Shen, X., Chen, M., & Zheng, X. (2021). Migration Behavior of Components in Converter Slag during Smelting Reduction Process Using Aluminum Dross. ISIJ International, 61(1), 49-54.
Shin, D. J., Gao, X., Ueda, S., & Kitamura, S.-y. (2019a). Selective Reduction of Phosphorus from Manganese Ore to Produce Ferromanganese Alloy with Low Phosphorus Content. Journal of Sustainable Metallurgy, 5(3), 362-377.
Shin, D. J., Gao, X., Ueda, S., & Kitamura, S.-y. (2019b). Separation of Phosphorus and Manganese from Steelmaking Slag by Selective Reduction. METALLURGICAL AND MATERIALS TRANSACTIONS B, 50(3), 1248-1259.
Su, T. H., Yang, H. J., Lee, Y. C., Shau, Y. H., Takazawa, E., Lin, M. F., . . . Jiang, W. T. (2016). Reductive Heating Experiments on BOF‐Slag: Simultaneous Phosphorus Re‐Distribution and Volume Stabilization for Recycling. Steel research international, 87(11), 1511-1526.
Suk, M.-O., Jo, S.-K., Kim, S.-H., Lee, K.-Y., & Park, J.-M. (2006). X-ray observation of phosphorus vaporization from steelmaking slag and suppression method of phosphorus reversion in liquid iron. METALLURGICAL AND MATERIALS TRANSACTIONS B, 37(1), 99-107.
Sun, Y.-s., Li, Y.-f., Han, Y.-x., & Li, Y.-j. (2019). Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore. International Journal of Minerals, Metallurgy, and Materials, 26(8), 938-945.
Sun, Y. H., Liu, Q. T., Wu, S. P., & Shang, F. (2014). Microwave heating of steel slag asphalt mixture. Paper presented at the Key Engineering Materials.
Uchida, Y.-i., Sasaki, N., & Miki, Y. (2018). Change of phosphorus-concentrated phase in low basicity steelmaking slag. ISIJ International, 58(5), 869-875.
Wang, C., Zhang, J., Liu, Z., Jiao, K., Wang, G., Yang, J., & Chou, K. (2017). Effect of chlorine on the viscosities and structures of CaO-SiO2-CaCl2 slags. METALLURGICAL AND MATERIALS TRANSACTIONS B, 48(1), 328-334.
Wang, S., Tong, S., Li, C., Xue, Y., Zhang, K., & Sun, H. (2022). Phosphorus (p) migration behavior in the process of converter slag gasification dephosphorization. Metalurgija, 61(1), 149-152.
Xia, Y., Li, J., Fan, D., & Hou, G. (2019). Effects of interfacial oxygen potential and slag phase changing during slag formation process on dephosphorization behavior. ISIJ International, ISIJINT-2019-2052.
Xue, P., He, D., Xu, A., Gu, Z., Yang, Q., Engström, F., & Björkman, B. (2017). Modification of industrial BOF slag: Formation of MgFe2O4 and recycling of iron. Journal of Alloys and Compounds, 712, 640-648.
Xue, Y., Li, C., Zhou, C., Zhao, D., & Wang, S. (2019). Removal mechanism of phosphorus by carbothermic reduction of steel slag. High Temperature Materials and Processes, 38(2019), 905-915.
Xue, Y., Tian, P., Li, C., Zhao, D., & Wang, S. (2020). Reduction Mechanism of P2O5 in Steel Slag. Transactions of the Indian Institute of Metals, 73(1), 251-258.
Xue, Y., Tian, P., Li, C., Zhou, C., Zhao, D., & Wang, S. (2021). Dephosphorization mechanism and phase change in the reduction of converter slag. High Temperature Materials and Processes, 40(1), 253-264.
Xue, Y., Wang, S., Zhao, D., & Li, C. (2019). Experimental Study on Phosphorus Vaporization for Converter Slag by SiC Reduction. In REWAS 2019 (pp. 391-399): Springer.
Xue, Y., Zhao, D., Wang, S., Li, C., & Guo, R. (2020). Phosphorus vaporization behaviour from converter slag. Ironmaking & Steelmaking, 47(8), 892-898.
Yan, C., Yoshikawa, N., & Taniguchi, S. (2005). Microwave heating behavior of blast furnace slag bearing high titanium. ISIJ International, 45(9), 1232-1237.
Yan, Z., Deng, Z., Zhu, M., & Huo, L. (2021). Effect of CaCl2 Addition on the Melting Behaviors of CaO-SiO2-FeOx Steelmaking Slag System. METALLURGICAL AND MATERIALS TRANSACTIONS B, 52(2), 1142-1153.
Yokoyama, K., Kubo, H., Mori, K., Okada, H., Takeuchi, S., & Nagasaka, T. (2007). Separation and recovery of phosphorus from steelmaking slags with the aid of a strong magnetic field. ISIJ International, 47(10), 1541-1548.
Yoshikawa, N., Sunako, M., Kawahira, K., Suzuki, K., Miyamoto, K., & Taniguchi, S. (2018). Carbothermic Reduction Kinetics of Phosphorous Vaporization from Tri-calcium Phosphate (TCP) Under Microwave Rapid Heating With/Without the Presence of Fe3O4. METALLURGICAL AND MATERIALS TRANSACTIONS B, 49(3), 969-976.
Zhang, W., Liu, W., Li, J., Shang, Y., Liu, Z., & Xing, H. (2016). High phosphorus slag gasificating dephosphorization of sintering atmosphere. Integrated Ferroelectrics, 168(1), 107-114.
Zhang, Y., Xue, Q., Wang, G., & Wang, J. (2018). Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction. ISIJ International, 58(12), 2219-2227.