Dephosphorization Rate Research Articles

Dephosphorization study on hydrogen reduction-melting separation of high-phosphorus oolitic hematite

In order to clarify the dephosphorization mechanism of DRI (Direct Reduced Iron) derived from hydrogen reduced high-phosphorus iron ore during the electric arc furnace melting process, slag was prepared using reagent-grade powder based on the gangue mineral composition of high-phosphorus oolitic hematite. By incorporating varying amounts of CaO, FeOx, and reduced iron powder, experiments simulating the dephosphorization of melting separation slag from DRI with different basicity and metallization rates were conducted at 1873 K. The results show that phosphorus in the iron primarily exists in the form of Fe-P-O spherical slag inclusions and FexP, while in the slag, phosphorus mainly resides within the silicate phases. As the amount of CaO added increases, there is a significant decrease in the phosphorus content within the slag inclusions, and the P-containing compounds in the iron gradually shift from FexP and Fe3(PO4)2 to FeO. As the dephosphorization capacity of the slag increases, the distribution of phosphorus-rich phases in the rapidly cooled slag becomes more extensive. When the basicity increases to 3, the phosphorus-rich phases in the slag transition to 2CaO·SiO2 and 3CaO·SiO2. When the basicity is fixed at 2.5, regulating the metallization rate can control the FeOx content in the melting slag, thereby enhancing the dephosphorization ability of slag. The results show that under conditions of a DRI basicity of 2.5 and a metallization rate of 85%, slag/metal separation can produce low-phosphorus iron with 0.022 wt% P, achieving a dephosphorization rate exceeding 95%.

Numerical analysis and industrial practice of single-flow post-combustion oxygen lance with high oxygen supply intensity

The oxygen supply process is a vital operation in converter steelmaking, which is to inject oxygen and kinetic energy into the liquid bath with an oxygen lance. Herein, a single-flow post-combustion oxygen lance (SF-PCL) with four primary holes and six secondary holes was designed to increase the oxygen supply intensity of a 60-ton converter in a steel plant. The attenuation and coalescence behaviors of supersonic jets for the conventional four-hole oxygen lance (COL) and the newly designed SF-PCL were studied by numerical simulation. And then, their metallurgical effects were verified by industrial practice. The simulation results indicated that the SF-PCL effectively suppresses the attenuation and coalescence of supersonic jets as well as simultaneously increases both the impact area and penetration depth. In industrial practice, compared with the COL, the newly designed SF-PCL increases the oxygen supply intensity from the original 4.89 m3 (t·min)−1 to 5.43 m3 (t·min)−1, rises the dephosphorization rate by 1.4%, shortens the blowing time by 34 s, reduces the ferrous charges consumption by 7 kg t−1 and decreases the total iron content in final slag by 0.85%.

Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud

The basic oxygen steelmaking process is based on the CaO-FeO-SiO2 ternary slag system, characterized by a high melting point and low lime dissolution rate, often becoming one of the key factors limiting the efficiency of the converter. The bulk solid waste red mud, produced by the Bayer alumina process and rich in Fe2O3/Al2O3/Na2O, significantly reduces the melting point of the steelmaking slag system and enhances the efficiency of lime dissolution. This study utilized red mud as the main raw material to prepare a fluoride-free flux. An in situ online observation system was used to measure the melting point of the flux and the dissolution rate of lime in the flux. The results indicate that the melting point of the red mud-based flux is below 1200 °C, and under the same conditions, the lime dissolution rate is 10 to 15 times higher than when this flux is not used. Experiments in a 10 kg induction furnace show that using this flux, the dephosphorization rate under conditions without oxygen blowing is close to 40%, far higher than the rate achieved using CaF2. Under oxygen-blowing conditions, the dephosphorization rate using the red mud-based flux is comparable to that of CaF2, and significantly higher than without any flux, especially under high [C] content conditions. The data show that the red mud-based flux has the potential to be widely used as a fluoride-free flux in the steelmaking process.

Development of Solid Waste-Based Composite Calcium Ferrite Flux and Its Application in Hot Metal Pre-Dephosphorization.

To enhance the slagging efficiency of the lime-based slag system during the pre-treatment stage of hot metal, a composite calcium ferrite flux based on aluminum industry solid waste was developed in this study. The melting characteristics of the flux and its application in the pre-treatment of hot metal were investigated. The results indicated that the main phases of the composite calcium ferrite were CaFe2O4, Ca2Fe2O5, and Ca2(Fe,Al)2O4. It exhibited high oxidation, high alkalinity, and a low melting point, thereby achieving excellent melting performance. Simulations of various dephosphorization fluxes in the pre-treatment of high-phosphorus hot metal, ordinary hot metal, and kilogram-scale dephosphorization experiment processes were conducted. Under the same experimental conditions, the composite calcium ferrite flux was able to achieve a dephosphorization rate of over 90% and a final phosphorus content of less than 0.02 wt% under high carbon content ([%C] = 3.2 wt%). In the application of hot metal pre-dephosphorization, this flux was able to achieve efficient melting and rapid slagging of lime at a lower temperature, and its slagging time was 50% faster than that of calcium ferrite flux. In addition, this flux enhanced the utilization efficiency of lime during the steelmaking process, effectively prevented the agglomeration of slag, and achieved efficient slag-metal separation. These characteristics were significantly better than the application effect of calcium ferrite flux. This flux has significant implications for the industrial application of deep dephosphorization in the pre-treatment stage of hot metal or the early stage of converter steelmaking.

Dephosphorization Kinetics of Hot Metal at Low Slag Basicity and Low Temperature under the Different Fe2O3 Addition Amounts

In this article, the influence of the Fe2O3 addition amount on the dephosphorization kinetics of hot metal at the low slag basicity (CaO/SiO2) of about 1.6 and low temperature of 1623 K is investigated with laboratorial experiments and the kinetic model. Si and P contents in the hot metal during the whole dephosphorization process, and the endpoint FeO content in the slag, show good agreements between the calculated results with the kinetic model and experimental results. The peak value of dephosphorization rate linearly increases from 8.35 × 10−5 to 4.52 × 10−4 mass% s−1 when the weight ratio of Fe2O3 is increased from 5 to 10/100 g hot metal. With the increase in Fe2O3 addition amount, the mass transfer coefficient in the hot metal phase (km) and that in the slag phase (ks) and dephosphorization rate constant (k) all increase. The value of km is found to be 4.34 times that of ks. During the dephosphorization process, the rate‐controlling step converts from the mass transfer in slag phase to the mass transfer in hot metal phase in less than 10 min. With the increase in Fe2O3 addition amount, the value of interfacial oxygen activity of increases from 0.0102 to 0.0201.

The Melting Mechanism of Hydrogen Direct Reduced Iron in Liquid Slag

The heating and melting of hydrogen direct reduced iron (H‐DRI) in liquid slag is investigated experimentally at 1923 K. For the experiments, slags comprising the CaO‐SiO2‐MgO‐FeO‐Al2O3 system are first premelted at 1923 K in alumina crucibles. The molten slag bath is subsequently used to submerge samples of 7 g of H‐DRI with different degrees of reduction (90.4–99.8%). Following the submersion, the slag bath and the H‐DRI sample are quenched at different times (5–10 s). It is found that the liquid slag penetrates the porous network of the H‐DRI. The penetration is found to increase with lower reduction degrees. The reaction‐enhanced capillary action theory is proposed to explain the dependence. The reasoning is validated by a cold model consisting of a quartz capillary, water, and solid sugar. The slag penetration also enhances the heat transfer and the dephosphorization rate. The present findings can, therefore, aid in optimizing the hydrogen‐based steelmaking route.

Development and Application of Converter COMI-B Technology: A New Way of CO2 Utilization

CO2 has characteristic properties and reactions at the converter smelting temperature, and the chemical reaction between CO2 and elements such as C and Si in the molten pool has bubble proliferation and cooling effects, which can effectively improve the kinetic and thermodynamic conditions of converter smelting. Here, an experimental study and industrial test on the application of CO2 in converter smelting were carried out. The smelting effects of Mode-1 and Mode-2 with total CO2 injection amounts of 229 Nm3 and 196 Nm3, respectively, were compared, and the changes in molten steel and slag compositions, dust removal, and gas were analyzed. The test results show that converter top and bottom blowing CO2 technology (COMI-B) technology had significant metallurgical advantages over the N-Mode; the dephosphorization rate increased by 4.2%, slag (FeO) content was reduced by 2.04%, end point nitrogen content of molten steel was reduced by 20%, gas recovery increased by 8.29 Nm3/t, and soot production was reduced by 14.7%. The results of the study provide a reference for the application of COMI-B technology in converters in the iron and steel industry and develop a new path for resource utilization of CO2.

Effect of CaO-MgO-FeO-SiO2-xNa2O Slag System on Converter Dephosphorization

Na2O is an alkaline oxide, which can significantly improve the dephosphorization ability of converter slag. The effect of Na2O on the dephosphorization of converter slag was analyzed with a high-temperature dephosphorization experiment in a MoSi2 resistance furnace. We found that the dephosphorization rate increased with the increase of (Na2O) in the dephosphorization slag. The elements of Ca, Si, O, and P in the dephosphorization slag are distributed in the same area, mainly in the form of phosphate minerals, such as Ca2SiO4·0.05Ca3(PO4)2 and 6Ca2SiO4·Ca3(PO4)2. After adding Na2O, part of the Na will replace the Ca in the phosphorus-containing phase to form Ca2SiO4·Ca2Na2(PO4)2. The industrial test showed that the average dephosphorization rate in the early stage of the test heats with the CaO-MgO-FeO-SiO2-0.5%Na2O slag system could reach 62.39%, which was 19.62% higher than that of the conventional heats. The average basicity of the final slag was 0.19% lower than that of the conventional heats, while w(P2O5) increased by 0.36%, and T.Fe decreased by 0.69%. The average consumption of the slagging materials was 35.93 kg/t, which was 7.24 kg/t less than that of the conventional heats. Through thermodynamic calculation, we found that with the increase of (Na2O), the phosphorus distribution ratio between slag and steel increased significantly, the area of the liquid phase zone of the slag system increased continuously, and the viscosity decreased continuously.

Gasification Behavior of Phosphorus during Biomass Sintering of High-phosphorus Iron Ore

Developing the innovative technology for efficient utilization of high-phosphate iron ore was the inevitable choice of resource strategy. In this paper, exploring a new method of gasification removal of phosphorus by iron ore sintering technology based on biomass. Combined with theoretical analysis and experimental research, the effects of different conditions (biochar type, addition proportion, basicity) on the reduction and gasification behavior of phosphorus were studied. The results showed that the addition of biochar instead of part of the coke powder could promote the reduction of apatite and increase the dephosphorization rate compared with the full coke breeze. Among different types of biochar fuels (fruit shell charcoal, straw charcoal, bamboo charcoal), bamboo carbon had the greatest effect on the dephosphorization rate. The optimal reduction temperature was 1100°C, substitution proportion of bamboo charcoal was 20% and basicity was 0.5 for the phosphorus gasification and removal, and the corresponding dephosphorization rate was 28.77%. Selective reduction of iron and phosphorus existed in the reduction process, iron oxide took precedence over the reduction of apatite, and part of phosphorus gas entered the metal iron to form iron phosphide, resulting in the decrease of dephosphorization rate.

Study on gasification dephosphorization of phosphorus magnetite reduced by SiC

The mechanism of reduction and dephosphorization of phosphorus-containing magnetite was studied using SiC as reducing agent. The thermodynamic conditions for the reduction of Ca3(PO4)2 and Fe3O4 by SiC were simulated by FactSage7.1 thermodynamics software, respectively, indicating that the reduction of Ca3(PO4)2 by SiC is thermodynamically feasible, but the kinetic conditions of the system are not good when no liquid phase is formed. The Fe2SiO4 liquid phase can be formed by reducing Fe3O4 by SiC at 1200 ℃. When the SiC ratio is 10 wt.%, the liquid phase content is the largest, which can reach more than 60 wt.%. Therefore, in this paper, the Fe2SiO4 liquid phase generated by the reduction of Fe3O4 by SiC is used to improve the kinetic conditions of the reduction of Ca3(PO4)2 by SiC at high temperature, and relevant experiments were carried out. The research results show that the system generates a suitable amount of liquid phase at 1250 °C, and the gasification dephosphorization rate is the highest, which is 39.89 wt.%, at 1200 °C, the reduction reaction was not fully carried out, and the dephosphorization rate by gasification was only 23.79 wt.%. At 1300 °C, Fe3O4 was completely reduced to metallic Fe, which combined with the reduced P4 gas to form Fe2P. Gasification dephosphorization rate is only 28.25 wt.%.

A Novel Process Design and Industrial Practice of Single‐Slag Smelting in 120 t Converter

With the reduction of raw material quality and the improvement of user requirements, the cost of dephosphorization increases. Steel plants urgently need an efficient and economic dephosphorization process to support the production. To address this issue, first, the migration and distribution of phosphorus in the converter smelting process are described quantitatively. Based on the regular solution model, the influence of slag components and temperature on the dephosphorization capacity of steel slag is explored. Afterward, considering the phosphorus distribution ratio, melting point, and phosphorus capacity of slag, the advantages of the slag‐forming route with higher FeO content in rapid slag formation and dephosphorization are expounded. Based on the guidance of the slag‐forming route, the scheme of controlling oxygen lance position and charging is optimized, and a novel blowing control mode is proposed. Finally, industrial tests on a 120 t converter show that the optimized smelting mode significantly reduces the cost and improves the efficiency. As a result, the lime consumption used to smelt a ton of steel is reduced by 3.67 kg t−1, and the dephosphorization rate is still increased by about 3.07%.

Research on Magnesium Reduction Slag for Dephosphorization of Low-Silicon Hot Metal in Steelmaking Process

The melting temperature and viscosity of magnesium reduction slag were calculated by using Factsage thermodynamic software. The composition range of the magnesium-slag-based dephosphorizing agent was analyzed by drawing a multiphase diagram of the slag system. The Box–Behnken high-temperature dephosphorization experiment was designed to study the effect of different composition of magnesium-slag-based dephosphorizers on the dephosphorization rate of the steelmaking process. The results show that magnesium slag can be used as a slag-forming agent for smelting low-silicon hot metal to promote slagging, and the effect of each factor on the phosphorus removal rate is ranked, and the results are ω(Fe2O3) > basicity > ω(Al2O3): ω(Al2O3) has no significant effect on the rate of phosphorus removal. When the basicity was 2.8, ω(Fe2O3) was 25.94%, ω(Al2O3) was 6.73%, and ω(MgO) was 6%, the dephosphorization rate reached a maximum of 96.7%, and the error was experimentally verified to be 2.6% from the predicted value, indicating that the model can be optimized to determine the best magnesium-slag-based dephosphorization agent and has a good prediction of dephosphorization effect.

Effect of slag basicity and reduction time on carbothermal reduction behaviour of P-bearing steelmaking slag

ABSTRACT To realize the efficient reduction and recycling of phosphorus resources in P-bearing steelmaking slag, it is necessary to study slag composition and phase changes during carbothermal reduction under different conditions (slag basicity and reduction time). The thermodynamic and kinetic behaviours of carbothermal reduction dephosphorization of P-bearing steelmaking slag are systematically discussed as well. The results show that the reduction rate of FeO and P2O5 show an upward trend with the increase of reduction time at 1823 K. However, the reduction rate of FeO does not change much within 50 minutes. In the range of slag basicity from 0.5 to 2.5, the formation of Ca3(PO4)2 increases with the increase of slag basicity. However, the increase of slag basicity is not good for the occurrence of carbothermic reduction gasification dephosphorization reaction. Taking into account the higher formation of Ca3(PO4)2 and the better dephosphorization effect of carbothermic reduction gasification, the appropriate slag basicity for carbothermic reduction gasification dephosphorization is 1.0–1.5. Carbothermal reduction gasification dephosphorization reaction of P-bearing steelmaking slag is a second-order reaction, and the mass transfer of P2O5 in the slag is the rate-limiting step of the whole process. The kinetic equations that describe the variation of P2O5 content in slag with time are yielded through regression. At 1823 K, by controlling the appropriate slag basicity (1.0–1.5) and reduction time (at least 20 minutes), the gasification dephosphorization rate of the carbothermal reduction can reach more than 80%, which can realize efficient recovery of phosphorus resources in P-bearing steelmaking slag.

Synchronous pressing and refining after solid-phase preadsorption technology as a new method for rapeseed oil preparation

A new method for rapeseed oil preparation named synchronous pressing and refining after solid-phase preadsorption technology was investigated. Rapeseed and adsorbents were first mixed evenly to form premixes, and the product oils were then obtained by direct pressing and filtering. The phospholipid content, acid value, a* value, chlorophyll, carotene, polyphenol contents of crude oil increased, while L* and b* values decreased with increasing squeezing chamber temperature. A moderate adsorbent dosage and temperature could improve the refining effects. Silicon dioxide had the highest dephosphorization and deacidification rates of 95% and 42%, respectively, when the dosage was 30 g/kg at 130 °C. Activated clay decreased the chlorophyll and carotene contents by 75% and 38%, respectively. Sucrose fatty acid ester had dephosphorization and deacidification rates of 67s% and 41%, respectively. Ascorbic palmitate had a dephosphorization rate of 74% and retained polyphenols intactly. This technology would not affect the oil yield and could decrease the peroxide value of rapeseed oil. It realized the simultaneous completion of pressing and refining with the advantages of a short preparation time and environmental sustainability.

Simulation and application of post-combustion oxygen lance in a top-blown converter

ABSTRACT Flow field characteristics of conventional four-hole oxygen lance and single-flow post-combustion (PC) oxygen lance at steelmaking temperature are studied by numerical simulation, and the industrial trials are carried out in the 120 t top-blown converter to evaluate their metallurgical effects. The simulation results indicate that with the increase of ambient temperature, the potential core length of oxygen jet, jet velocity and radial width (jet diameter) increase. And the jet characteristics of PC oxygen lance are better than those of conventional lance in the radial and axial directions. The industrial trials show that, compared with the conventional lance, using the PC oxygen lance can shorten blowing time by 93 s, reduce actual oxygen consumption by 3.56 m3 t−1 and increase dephosphorization rate by 1.67%. Meanwhile, PC oxygen lance is better for slagging and solves the problem of splashing or drying caused by increasing the oxygen flow rate of the conventional lance.

A New Route to Upgrading the High-Phosphorus Oolitic Hematite Ore by Sodium Magnetization Roasting-Magnetic Separation-Acid and Alkaline Leaching Process

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P2O5 at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P2O5, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

Dephosphorization kinetics of high-P-containing reduced iron produced from oolitic hematite ore

Abstract To comprehensively utilize Fe and P in oolitic hematite ore, an innovative method was proposed to enhance P enrichment in the reduced iron during the reduction process. The reduced iron was then converted to low-P-containing molten iron and high-P-containing slag in the presence of CaO–SiO2–FeO–Al2O3 slag. In this study, the P content of the final iron after 0–1,800 s dephosphorization was investigated at different slag composition conditions, and the dephosphorization kinetics of the reduced iron was analyzed. The results showed that the P content of the final iron sample decreased rapidly within 600 s of dephosphorization and became almost constant with increasing dephosphorization time to 1,800 s. The basicity, FeO content, and Al2O3 content also affected the dephosphorization rate of the reduced iron. The apparent dephosphorization rate constant ranged from 1.141 × 10−3 to 2.363 × 10−3 g·(cm2·s)−1, and the overall mass transfer coefficient ranged from 2.47 × 10−3 to 3.38 × 10−3 cm·s−1. The rate-controlling step of the dephosphorization process was the mass transfer of P in both the slag and iron phases. The findings of this study provide a theoretical basis for the utilization of refractory oolitic hematite ore.

Hot metal dephosphorization process using calcium ferrite slag without fluorite

ABSTRACT To solve environmental pollution caused by using fluorite slagging in the process of hot metal dephosphorization, this paper applies pre-melted calcium ferrite slag in the production of stainless steel powder injection and oxygen dephosphorization process to replace fluorite slagging. The results show that the average hot metal dephosphorization rate of calcium ferrite slagging is 88.06%, and its dephosphorization effect is better than that of fluorite slagging. The average hot metal dephosphorization rate of fluorite slagging is 77.7%. The slag melting temperature during calcium ferrite slagging is 1137°C on average, which is lower than the melting temperature of fluorite slagging, and the slag melting temperature during fluorite slagging is 1296°C on average. When calcium ferrite slagging, the slag melting condition is good during the blow process. According to the results of material cost estimation, it is completely feasible to substitute calcium ferrite slag for fluorite slagging.

Carbon aerogel electrode for excellent dephosphorization via flow capacitive deionization

Flow-electrode capacitive deionization (FCDI) has emerged as a new method in dephosphorization, for its high efficiency and continuous operation. Using conventional carbon-based materials for fabricating FCDI electrodes have limitations in conductivity, specific surface area, toxicity, and dispersion. In this study, a new carbon aerogel (CA) was synthesized using the resorcinol–formaldehyde resin via an electric heating furnace drying method. N2 adsorption–desorption isotherm and electrochemical impedance spectroscopy shows that the material has high specific surface area and a high conductivity. CA has a faster dephosphorization rate and lower energy consumption (1.74 kWh/kg-P) (1.20 μg·min−1·cm−2) than that of activated carbon (AC) when used in FCDI dephosphorization owing to its good conductivity and dispersibility. This study demonstrates the commercial application potential of CA as an FCDI electrode material for phosphorus recovery.

Process optimization and characterization of arachidonic acid oil degumming using ultrasound-assisted enzymatic method

Ultrasound assisted enzymatic method was applied to the degumming of arachidonic acid (ARA) oil produced by Mortierella alpina. The conditions of degumming process were optimized by response surface methodology with Box- Behnken design. A dephosphorization rate of 98.82% was achieved under optimum conditions of a 500 U/kg of Phospholipase A1 (PLA1) dosage, 2.8 mL/100 g of water volume, 120 min of ultrasonic time, and 135 W of ultrasonic power. The phosphorus content of ultrasonic assisted enzymatic degumming oil (UAEDO) was 4.79 mg/kg, which was significantly lower than that of enzymatic degumming oil (EDO, 17.98 mg/kg). Crude Oil (CO), EDO and UAEDO revealed the similar fatty acid compositions, and ARA was dominated (50.97 ~ 52.40%). The oxidation stability of UAEDO was equivalent to EDO and weaker than CO, while UAEDO presented the strongest thermal stability, followed by EDO and CO. Furthermore, aldehydes, acids and alcohols were identified the main volatile flavor components for the three oils. The proportions of major contributing components such as hexanal, nonanal, (E)-2-nonanal, (E, E)-2,4-decadienal, (E)-2-nonenal and aldehydes in UAEDO and EDO were all lower than CO. Overall, Ultrasound assisted enzymatic degumming proved to be an efficient and superior method for degumming of ARA oil.