The machine learning models of multiple linear regression(MLR),support vector regression(SVR),and extreme learning ma-chine(ELM)and the proposed ELM models of online sequential ELM(OS-ELM)and OS-ELM with forgetting me...The machine learning models of multiple linear regression(MLR),support vector regression(SVR),and extreme learning ma-chine(ELM)and the proposed ELM models of online sequential ELM(OS-ELM)and OS-ELM with forgetting mechanism(FOS-ELM)are applied in the prediction of the lime utilization ratio of dephosphorization in the basic oxygen furnace steelmaking process.The ELM model exhibites the best performance compared with the models of MLR and SVR.OS-ELM and FOS-ELM are applied for sequential learning and model updating.The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500,with the smallest population mean absolute relative error(MARE)value of 0.058226 for the population.The variable importance analysis reveals lime weight,initial P content,and hot metal weight as the most important variables for the lime utilization ratio.The lime utilization ratio increases with the decrease in lime weight and the increases in the initial P content and hot metal weight.A prediction system based on FOS-ELM is applied in actual industrial production for one month.The hit ratios of the predicted lime utilization ratio in the error ranges of±1%,±3%,and±5%are 61.16%,90.63%,and 94.11%,respectively.The coefficient of determination,MARE,and root mean square error are 0.8670,0.06823,and 1.4265,respectively.The system exhibits desirable performance for applications in actual industrial pro-duction.展开更多
The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperatur...The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.展开更多
The formation of solid solution combined with tricalcium phosphate and dicalcium silicate could promote a considerable removal of phosphorus from liquid slag to solid during hot metal dephosphorization,and thus the de...The formation of solid solution combined with tricalcium phosphate and dicalcium silicate could promote a considerable removal of phosphorus from liquid slag to solid during hot metal dephosphorization,and thus the dephosphorization by using multi phase fluxes could significantly decrease the consumption of lime. However,the reaction mechanism of multi phase fluxes has not been understood clearly.In the present study,the phase diagram for the CaO-SiO2-FeO-P2O5 system has been measured with certain oxygen partial pressure at hot metal pretreatment temperature.Comparing with the CaO-SiO2-FeO system,shrinkage of liquid phase area at higher FeO contents was observed at 1 673 K with oxygen partial pressure of 9.2×10-11 atm.展开更多
At low basicity and low temperature, the dephosphorization behavior and phosphorus distribution ratio(LP) between slag and molten steel in the double slag and remaining slag process were studied with a 180 t basic oxy...At low basicity and low temperature, the dephosphorization behavior and phosphorus distribution ratio(LP) between slag and molten steel in the double slag and remaining slag process were studied with a 180 t basic oxygen furnace industrial experiment.The dephosphorization slags with different basicities were quantitatively analyzed.At the lower basicity range of 0.9–2.59, both LP and dephosphorization ratio were increased as the basicity of dephosphorization slag increased.Dephosphorization slag consisted of dark gray P-rich, light gray liquid slag,and white Fe-rich phases.With increasing basicity, not only did the morphologies of different phases in the dephosphorization slag change greatly, but the area fractions and P2O5 content of the P-rich phase also increased.The transfer route of P during dephosphorization can be deduced as hot metal → liquid slag phase + Fe-rich phase → P-rich phase.展开更多
The relation of Lp(the ratio P content in slag to P content in ferromanganese) and L_(mn),(the ratio Mn content in slag to Mn content in ferromanganese) with C content[C]in ferromanganese were tested by means of the e...The relation of Lp(the ratio P content in slag to P content in ferromanganese) and L_(mn),(the ratio Mn content in slag to Mn content in ferromanganese) with C content[C]in ferromanganese were tested by means of the equilibrium experiments of P and Mn between ferromanganese and BaO-BaF_2-MnO slag system.The results show that there exists in ferromanganese an optimum C content[C]* corresponding to maximum L_P and minimum L_(Mn)> which is closely related to oxygen potential in the system and the activity of P in the alloy.The control limits of oxygen potential in dephosphorization of ferromanganese are then analyzed.The theoretical limits and measures to improve ferromanganese dephosphorization with BaO-based slag are studied comprehensively based on previous research.展开更多
Combined with the practical experience of wastewater treatment plant, the chemical coagulants have inhibition effects on microorganism activity, with the influence degree of PAC (polyaluminium chloride) > AlCl3>...Combined with the practical experience of wastewater treatment plant, the chemical coagulants have inhibition effects on microorganism activity, with the influence degree of PAC (polyaluminium chloride) > AlCl3> Fe2(SO4)3. In synchronization dephosphorization, the inhibition rates of PAC in 10 ppm and 20 ppm are 11.9% and 33% respectively;while the inhibition rates of AlCl3 and Fe2(SO4)3 in 20 ppm are 15.8% and 8.5% respectively, compared with 9.6% and 5.4% in 10 ppm. Backwash wastewater from sand filter after adding coagulants has no direct inhibition effect on microorganism, but it results in inorganic components increase in active sludge. By taking North STP as an example, the VSS/SS ratio reduced from 0.65 after coagulants application to 0.54.展开更多
Prolonged sludge age sequencing batch biofilm reactor (SBBR) without sludge discharge appears high performance phosphorus removal in treating saline and high-phosphorus wastewater,which cannot be explained by traditio...Prolonged sludge age sequencing batch biofilm reactor (SBBR) without sludge discharge appears high performance phosphorus removal in treating saline and high-phosphorus wastewater,which cannot be explained by traditional biological dephosphorization theory. The new path and mechanism of phosphorus removal was discussed on the phosphorus balance of phosphorus removal system without sludge discharge. Phosphorus balance in sludge was studied on 26 running cycles of the phosphorus reduction system. The results show that there is only 0.12 mg/g poly-P in sludge at the end of each reaction period,not phosphorus uptake by polyphosphate-accumulating organisms (PAOs). It is found that 41.8 mg/L of external phosphorus gets lost per day averagely,and 155 mg of internal phosphorus in sludge gets lost. The matrix bound phosphine in sludge achieves 36.04 mg/kg measured by alkaline digestion,and there is 18.44 mg/kg in +1 valence state,a intermediate,in sludge. This implies that the phosphorus removal system of prolonged sludge age SBBR without sludge discharge is a phosphate reduction,and the path of dephosphorization is phosphate→hypophosphite→phosphine.展开更多
In the scale of ironmaking and steelmaking, the dephosphorization can be divided into four classes. The first level which is known very well by metallurgists is the dephosphorization for carbon steels and low alloy st...In the scale of ironmaking and steelmaking, the dephosphorization can be divided into four classes. The first level which is known very well by metallurgists is the dephosphorization for carbon steels and low alloy steels. The second level is that included in the pretreatment process of hot metal. It differs from the first level as it must consider how to treat the selective oxidation of ［P］ and ［C］. Furthermore, The contradictory of dephosphorization and desulphurization has to be harmonized. The third level is that for high alloy steels and the fourth is that for ferroalloys. In these cases, two technical ways either oxidizing dephosphorization or reducing dephosphorization can be selected. Whether which one is chosen, the key problem is to lower down phosphorous content efficiently meanwhile to keep the concentration of Cr and/or Mn almost lossless.
The cheapest raw materials for the production of high alloy steel are the returning scrap of that steel. Raising the proportion of the returning scraps in the total amount of raw materials is a very important measure to decrease the production cost. In order to avoid an obvious oxidation of Cr, Mn and so on during that melting process it is impossible to adopt the oxidational dephosphorization procedures which is generally carried out in the production of low alloy steel. In this case, after returning several times the phosphorous content in the scraps is accumulated. And then it gradually approaches to the level specified in the standard of the steel. Finally, it will become a waste. It was estimated that the market demand on high alloy steels as stainless steels would rapidly grow. So the scraps containing low phosphorous is urgently needed in a great deal.
On the other hand, the standards of some high alloy steels, which are designated for extremely severe environment only, allow a very low phosphorous content. For example, it is claimed that W［P］<0.015 %—0.020 % if the stainless steel products will contact with urea or nitric acid. If the resistance to corrosive fatigue and welding crack is highlighted the phosphorous content should be decreased to less than (100—50)×10－4 %. And Koros P J et al estimated that dephosphorous to 14×10－4 % will be wanted［1］.
So far no technology for dephosphorization of stainless steels can be widely adopted in industrial scale. This will be one of the major research projects in the coming century. This paper devotes to a discussion on the strategy of oxidational dephosphorization and the improvement of the reductional dephosphorization.展开更多
The slag formation path is important for efficient dephosphorization in steelmaking processes. The phosphorus capacity and the melting properties of the slag are critical parameters for optimizing the slag formation p...The slag formation path is important for efficient dephosphorization in steelmaking processes. The phosphorus capacity and the melting properties of the slag are critical parameters for optimizing the slag formation path. Regarding these two factors, the phosphorus partition ratio was calculated using the regular solution model(RSM), whereas the liquidus diagrams of the slag systems were estimated using the FactS age thermodynamic package. A slag formation path that satisfies the different requirements of dephosphorization at different stages of dephosphorization in a converter was thus established through a combination of these two aspects. The composition of the initial slag was considered to be approximately 15wt%CaO –44wt%SiO 2–41wt%FeO. During the dephosphorization process, a slag formation path that follows a high-iron route would facilitate efficient dephosphorization. The composition of the final dephosphorization slag should be approximately 53wt%CaO –25.5wt%SiO 2–21.5wt%FeO. The composition of the final solid slag after dephosphorization is approximately 63.6wt%CaO –30.3wt%SiO 2–6.1wt%FeO.展开更多
The molten steel was dephosphorized by high basic BaO-based slags （BaO-CaO-CaF2） to achieve ultra low phosphorus level. The dephosphorization ability of the BaO-CaO-CaF2 slags was tested. The phosphate capacity of t...The molten steel was dephosphorized by high basic BaO-based slags （BaO-CaO-CaF2） to achieve ultra low phosphorus level. The dephosphorization ability of the BaO-CaO-CaF2 slags was tested. The phosphate capacity of this slag system at 1 620 ℃ varied from 1018.03 to 1019.11 with an activity coefficient of P2O5 ranging from 10-19.47 to 10-18.09. The effect of BaO content, initial phosphorus content and oxygen potential of molten steel on dephosphorization was discussed. The phosphorus pick-up by the BaO-based slags was studied.展开更多
The dephosphorization experiments of low phosphorus containing steel by CaO-based and BaO-based fluxes were carried out. The effects of the oxygen potential in molten steel and the BaO content in the slag on dephospho...The dephosphorization experiments of low phosphorus containing steel by CaO-based and BaO-based fluxes were carried out. The effects of the oxygen potential in molten steel and the BaO content in the slag on dephosphorization and rephosphorization of molten steel were analyzed. The results showed that the dephosphorization ratio of more than 50% and the ultra-low phosphorus content of less than 0.005% in steel were obtained by the three kinds of dephosphorization fluxes as the oxygen potential of molten steel higher than 400×10-6. Rephosphorization of molten steel was serious as the oxygen content of molten steel lower than 10×10-6. BaO-based fluxes can improve the dephosphorization effect and reduce the phosphorus pick-up effectively under the condition of weak deoxidization of molten steel (the oxygen potential is about 100×10-6), but can not prevent rephosphorization under the condi- tion of deep deoxidization of molten steel (the oxygen potential less than 10×10-6).展开更多
In this work,the effects of pH value of waste water and initial concentration of phosphorus on dephosphorization materials were investigated.The materials were prepared by shaping,sintering and hydrothermal reshaping ...In this work,the effects of pH value of waste water and initial concentration of phosphorus on dephosphorization materials were investigated.The materials were prepared by shaping,sintering and hydrothermal reshaping oyster shell and silica micro-powder.Different concentrations of phosphorus-contained waste water were simulated with potassium dihydrogen phosphate solution,the effect of dephosphorization was tested with phosphomolybdenum blue spectrophotometer method,and the crystal phase and microstructure of materials were characterized by XRD and SEM methods.It was indicated that dephosphorization was completed in 6 h when the initial phosphorus concentration in waste water was lower than 15 mg/L,and the dephosphorization time prolonged as the increase of phosphorus concentration.It was observed that the pH value of waste water influenced dephosphorization significantly,and neutral subalkalic environment favored dephosphorization.When the pH value was 11,the efficiency of dephosphozation was the greatest.For waste water with an initial concentration of 20 mg/L,the dephosphozation rate is close to 100% in 8 h.展开更多
The vacuum treatment for simultaneous desulphurization and dephosphorization of hot metal and molten steel with pre-melted CaO-based slag was carried out. For pre-treatment of hot metal, both desulphurization and deph...The vacuum treatment for simultaneous desulphurization and dephosphorization of hot metal and molten steel with pre-melted CaO-based slag was carried out. For pre-treatment of hot metal, both desulphurization and dephosphorization are improved with the increase of CaO in slag, but deteriorated with the increase of CaF2 in slag. The average desulphurization and dephosphorization rate is 68.83 % and 78.46 %, respectively. For molten steel, the substitution of BaO for CaO in slag has minor effect on simultaneous desulphurization and dephosphorization. The desulphurization and dephosphorization rate is higher than 90 % and 50 % respectively with the lowest final sulfur and phosphorus mass percent being 0.001 2 % and 0.010 %, respectively. The overall effect of simultaneous desulphurization and dephosphorization of molten steel is better than that of hot metal.展开更多
Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high de...Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high dephosphorization efficiency can be reached at the temperatures ranging from 1 200 to 1 400°C.When the monazite pellets,made by pressing mixture of the monazite,charred coal and water into mould,were roasted at 1 400°C for 2 h,98%of phosphorus was removed from the monazite pellets.The roast time has little effect on the dephosphorization efficiency.Meanwhile,the particle size of the charred coal also has great influence on the dephosphorization efficiency of the monazite,and it is better to control particle size around 150μm,while Fe and Fe2O3 have neglectable effect on the dephosphorization of the monazite.展开更多
Laboratory study was carried out on deep dephosphorization of liquid steel by BaO-based fluxes at 1600℃ to achieve ultra low phosphorus level in the steel. A dynamic model of dephosphorization of liquid steel by BaO-...Laboratory study was carried out on deep dephosphorization of liquid steel by BaO-based fluxes at 1600℃ to achieve ultra low phosphorus level in the steel. A dynamic model of dephosphorization of liquid steel by BaO-based fluxes was established.According to the model, the controlling step of dephosphorization by BaO-based fluxes was the mass-transfer of phosphorus in steel phase under the condition of low phosphorus liquid steel. It is estimated that the apparent rate constant of dephosphorization by BaObased fluxes was 0.4×10-3-8.2×10-3 g/(cm2.s) and the mass-transfer coefficient of phosphorus in bulk steel was 0.025-0.04 cm/s.展开更多
The reduction and recovery of P_(2)O_(5)in dephosphorization slag were examined to establish a new recycling process for dephosphorization slag.The dephosphorization slag is obtained from the dephosphorization furnace...The reduction and recovery of P_(2)O_(5)in dephosphorization slag were examined to establish a new recycling process for dephosphorization slag.The dephosphorization slag is obtained from the dephosphorization furnace in the duplex converter process,and the content of P_(2)O_(5) in the dephosphorization slag can reach 9 wt.%.The dephosphorization slag is considered to be a prospective resource of phosphorus due to its high content of P_(2)O_(5).To explore the effects of temperature and Fe2O3 content in slag on phosphorus recovery from dephosphorization slag,the experimental slag was reduced by carbon powder in a resistance furnace.The results show that the temperature and content of Fe2O3 in slag have a significant effect on the reduction in P_(2)O_(5),and the reduction and recovery ratios of P_(2)O_(5) in slags increase with the increase in the experimental temperature and content of Fe_(2)O_(3),reaching 94.41%and 83.09%,respectively.It has been indicated that phosphorus recovery from dephosphorization slag using carbothermic reduction has significant environmental and economic benefits.展开更多
Dephosphorization slag is one of the bulk solid wastes generated from steelmaking.If P is effectively removed from dephosphorization slag,a phosphate source which can substitute for phosphate rocks is obtained;meanwhi...Dephosphorization slag is one of the bulk solid wastes generated from steelmaking.If P is effectively removed from dephosphorization slag,a phosphate source which can substitute for phosphate rocks is obtained;meanwhile,the tailings can be reutilized as a feedstock in steel plant.To realize the integrated utilization of dephosphorization slag,selective leaching was applied for removing the P-bearing mineral phase from dephosphorization slag.Alkaline oxide was added as the slag modifier and HCl was selected as the acid lixiviant.The P selective leaching from dephosphorization slags modified by Na_(2)O or K_(2)O was studied at different pH values.By modification,the mass fraction of P in the_(2)CaO∙SiO_(2)–3CaO∙P_(2)O_(5)phase increased,indicating that it was in favor of P_(2)O_(5)enrichment.As the Na_(2)O or K_(2)O content increased,the P leaching ratio from slag increased at pH 4,reaching about 80%,and that of Fe was nearly zero.Na_(2)O and K_(2)O modification played a similar role in enhancing the P leaching.The effect of alkaline oxide modification became weak at pH 3,and the slag without modification also realized a good P selective leaching in the HCl solution.To facilitate the P removal,the leaching of Fe from dephosphorization slag needs to be restrained.展开更多
The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot meta...The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot metal meanwhile retaining Nb in the steel products remains a challenge. We carried out a thermodynamic study on dephosphorization of Nbbearing hot metal and investigated the effects of the initial [C] content and the dephosphorization temperature on oxidation behaviors of [Nb] and [P]. In particular, we focused on thermodynamic analysis of dephosphorization of Nb-bearing hot metal with highly basic BaO-based slag. The results showed that the highly basic BaO-based slag system is more suitable for dephosphorization under oxidative conditions, and increasing the [C] content favors dephosphorization of Nb-bearing hot metal without oxidizing [Nb]. Moreover, the values of equilibrium oxygen activity for oxidation reactions of [Nb] and [P] are increased as the dephosphorization temperature increases. Considering the hot metal containing 0.02% of [Nb] in Baotou Steel, thermodynamic calculations indicated that the content of [P] can be reduced to 0.02%–0.05% and [Nb] remains unoxidized when dephosphorization occurs at the cconditions of T=1573–1673 K, [C]=4.0%, [Nb]=0.02%, aP2O5=10-24, aNb2O5=10-10.展开更多
Development of the efficient hot metal dephosphorization processes during steelmaking process is one of the most essential topics for the production of high grade clean steels. Since the formation of solid solution co...Development of the efficient hot metal dephosphorization processes during steelmaking process is one of the most essential topics for the production of high grade clean steels. Since the formation of solid solution composed of tricalcium phosphate and dicalcium silicate could obtain a considerable mass transfer of phosphorus from liquid slag into solid phase during hot metal dephosphorization, itcould obviously sustain a high phosphatecapacityof theliquid slag without huge consumption of lime or addition of fluxes, such as fluorite. The above outlines are the main idea of multi phase flux dephosphorization. For the last few decades, many studies have been done towards the scientific principles and the commercial utilization of this technique. However, the reaction mechanism by using multi phase fluxes remains unclear even by now due tolack of evidence. Based on those previous works, providing a reliable and available phase diagram for the fundamental understanding of the reaction mechanism of multi phase flux dephosphorization has become the main purpose of present research. As well known, the CaO-SiO2-FeO-P2O5 slag is the main component of current steelmaking process. Hence the CaO-SiO2-FeO-P2O5 system at equilibrium has been studied at 1673K with low oxygen partial pressure. The solid phase coexisting with liquid flux is approved to be the solid solution composed of CaO, SiO2 and P2O5. Phosphorus distributes mainly in solid solution rather than liquid phase.展开更多
基金supported by the National Natural Science Foundation of China (No.U1960202).
文摘The machine learning models of multiple linear regression(MLR),support vector regression(SVR),and extreme learning ma-chine(ELM)and the proposed ELM models of online sequential ELM(OS-ELM)and OS-ELM with forgetting mechanism(FOS-ELM)are applied in the prediction of the lime utilization ratio of dephosphorization in the basic oxygen furnace steelmaking process.The ELM model exhibites the best performance compared with the models of MLR and SVR.OS-ELM and FOS-ELM are applied for sequential learning and model updating.The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500,with the smallest population mean absolute relative error(MARE)value of 0.058226 for the population.The variable importance analysis reveals lime weight,initial P content,and hot metal weight as the most important variables for the lime utilization ratio.The lime utilization ratio increases with the decrease in lime weight and the increases in the initial P content and hot metal weight.A prediction system based on FOS-ELM is applied in actual industrial production for one month.The hit ratios of the predicted lime utilization ratio in the error ranges of±1%,±3%,and±5%are 61.16%,90.63%,and 94.11%,respectively.The coefficient of determination,MARE,and root mean square error are 0.8670,0.06823,and 1.4265,respectively.The system exhibits desirable performance for applications in actual industrial pro-duction.
基金the National Natural Science Foundation of China(Nos.51734005,51874071,and 51604063)the Fok Ying Tung Education Foundation for Young Teachers in the Higher Education Institutions of China(No.161045)+1 种基金the Liao Ning Revitalization Talents Program(No.XLYC1807111)the Fundamental Research Funds for the Central Universities of China(No.N180105030).
文摘The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.
文摘The formation of solid solution combined with tricalcium phosphate and dicalcium silicate could promote a considerable removal of phosphorus from liquid slag to solid during hot metal dephosphorization,and thus the dephosphorization by using multi phase fluxes could significantly decrease the consumption of lime. However,the reaction mechanism of multi phase fluxes has not been understood clearly.In the present study,the phase diagram for the CaO-SiO2-FeO-P2O5 system has been measured with certain oxygen partial pressure at hot metal pretreatment temperature.Comparing with the CaO-SiO2-FeO system,shrinkage of liquid phase area at higher FeO contents was observed at 1 673 K with oxygen partial pressure of 9.2×10-11 atm.
基金financially supported by the National Natural Science Foundation of China (No.U1960202)。
文摘At low basicity and low temperature, the dephosphorization behavior and phosphorus distribution ratio(LP) between slag and molten steel in the double slag and remaining slag process were studied with a 180 t basic oxygen furnace industrial experiment.The dephosphorization slags with different basicities were quantitatively analyzed.At the lower basicity range of 0.9–2.59, both LP and dephosphorization ratio were increased as the basicity of dephosphorization slag increased.Dephosphorization slag consisted of dark gray P-rich, light gray liquid slag,and white Fe-rich phases.With increasing basicity, not only did the morphologies of different phases in the dephosphorization slag change greatly, but the area fractions and P2O5 content of the P-rich phase also increased.The transfer route of P during dephosphorization can be deduced as hot metal → liquid slag phase + Fe-rich phase → P-rich phase.
基金This project is sponsored by the National Foundation of Natural Science of China
文摘The relation of Lp(the ratio P content in slag to P content in ferromanganese) and L_(mn),(the ratio Mn content in slag to Mn content in ferromanganese) with C content[C]in ferromanganese were tested by means of the equilibrium experiments of P and Mn between ferromanganese and BaO-BaF_2-MnO slag system.The results show that there exists in ferromanganese an optimum C content[C]* corresponding to maximum L_P and minimum L_(Mn)> which is closely related to oxygen potential in the system and the activity of P in the alloy.The control limits of oxygen potential in dephosphorization of ferromanganese are then analyzed.The theoretical limits and measures to improve ferromanganese dephosphorization with BaO-based slag are studied comprehensively based on previous research.
文摘Combined with the practical experience of wastewater treatment plant, the chemical coagulants have inhibition effects on microorganism activity, with the influence degree of PAC (polyaluminium chloride) > AlCl3> Fe2(SO4)3. In synchronization dephosphorization, the inhibition rates of PAC in 10 ppm and 20 ppm are 11.9% and 33% respectively;while the inhibition rates of AlCl3 and Fe2(SO4)3 in 20 ppm are 15.8% and 8.5% respectively, compared with 9.6% and 5.4% in 10 ppm. Backwash wastewater from sand filter after adding coagulants has no direct inhibition effect on microorganism, but it results in inorganic components increase in active sludge. By taking North STP as an example, the VSS/SS ratio reduced from 0.65 after coagulants application to 0.54.
基金Project (2008ZX07315-004) supported by National Water Pollution Controlled and Treatment Great Special of China
文摘Prolonged sludge age sequencing batch biofilm reactor (SBBR) without sludge discharge appears high performance phosphorus removal in treating saline and high-phosphorus wastewater,which cannot be explained by traditional biological dephosphorization theory. The new path and mechanism of phosphorus removal was discussed on the phosphorus balance of phosphorus removal system without sludge discharge. Phosphorus balance in sludge was studied on 26 running cycles of the phosphorus reduction system. The results show that there is only 0.12 mg/g poly-P in sludge at the end of each reaction period,not phosphorus uptake by polyphosphate-accumulating organisms (PAOs). It is found that 41.8 mg/L of external phosphorus gets lost per day averagely,and 155 mg of internal phosphorus in sludge gets lost. The matrix bound phosphine in sludge achieves 36.04 mg/kg measured by alkaline digestion,and there is 18.44 mg/kg in +1 valence state,a intermediate,in sludge. This implies that the phosphorus removal system of prolonged sludge age SBBR without sludge discharge is a phosphate reduction,and the path of dephosphorization is phosphate→hypophosphite→phosphine.
基金Project Supported by the Shanghai Science&Technology Development Foundation(G 01158)
文摘In the scale of ironmaking and steelmaking, the dephosphorization can be divided into four classes. The first level which is known very well by metallurgists is the dephosphorization for carbon steels and low alloy steels. The second level is that included in the pretreatment process of hot metal. It differs from the first level as it must consider how to treat the selective oxidation of ［P］ and ［C］. Furthermore, The contradictory of dephosphorization and desulphurization has to be harmonized. The third level is that for high alloy steels and the fourth is that for ferroalloys. In these cases, two technical ways either oxidizing dephosphorization or reducing dephosphorization can be selected. Whether which one is chosen, the key problem is to lower down phosphorous content efficiently meanwhile to keep the concentration of Cr and/or Mn almost lossless.
The cheapest raw materials for the production of high alloy steel are the returning scrap of that steel. Raising the proportion of the returning scraps in the total amount of raw materials is a very important measure to decrease the production cost. In order to avoid an obvious oxidation of Cr, Mn and so on during that melting process it is impossible to adopt the oxidational dephosphorization procedures which is generally carried out in the production of low alloy steel. In this case, after returning several times the phosphorous content in the scraps is accumulated. And then it gradually approaches to the level specified in the standard of the steel. Finally, it will become a waste. It was estimated that the market demand on high alloy steels as stainless steels would rapidly grow. So the scraps containing low phosphorous is urgently needed in a great deal.
On the other hand, the standards of some high alloy steels, which are designated for extremely severe environment only, allow a very low phosphorous content. For example, it is claimed that W［P］<0.015 %—0.020 % if the stainless steel products will contact with urea or nitric acid. If the resistance to corrosive fatigue and welding crack is highlighted the phosphorous content should be decreased to less than (100—50)×10－4 %. And Koros P J et al estimated that dephosphorous to 14×10－4 % will be wanted［1］.
So far no technology for dephosphorization of stainless steels can be widely adopted in industrial scale. This will be one of the major research projects in the coming century. This paper devotes to a discussion on the strategy of oxidational dephosphorization and the improvement of the reductional dephosphorization.
基金partially supported by the Fundamental Research Funds for the Central Universities (No. CDJZR 14130001)
文摘The slag formation path is important for efficient dephosphorization in steelmaking processes. The phosphorus capacity and the melting properties of the slag are critical parameters for optimizing the slag formation path. Regarding these two factors, the phosphorus partition ratio was calculated using the regular solution model(RSM), whereas the liquidus diagrams of the slag systems were estimated using the FactS age thermodynamic package. A slag formation path that satisfies the different requirements of dephosphorization at different stages of dephosphorization in a converter was thus established through a combination of these two aspects. The composition of the initial slag was considered to be approximately 15wt%CaO –44wt%SiO 2–41wt%FeO. During the dephosphorization process, a slag formation path that follows a high-iron route would facilitate efficient dephosphorization. The composition of the final dephosphorization slag should be approximately 53wt%CaO –25.5wt%SiO 2–21.5wt%FeO. The composition of the final solid slag after dephosphorization is approximately 63.6wt%CaO –30.3wt%SiO 2–6.1wt%FeO.
文摘The molten steel was dephosphorized by high basic BaO-based slags （BaO-CaO-CaF2） to achieve ultra low phosphorus level. The dephosphorization ability of the BaO-CaO-CaF2 slags was tested. The phosphate capacity of this slag system at 1 620 ℃ varied from 1018.03 to 1019.11 with an activity coefficient of P2O5 ranging from 10-19.47 to 10-18.09. The effect of BaO content, initial phosphorus content and oxygen potential of molten steel on dephosphorization was discussed. The phosphorus pick-up by the BaO-based slags was studied.
文摘The dephosphorization experiments of low phosphorus containing steel by CaO-based and BaO-based fluxes were carried out. The effects of the oxygen potential in molten steel and the BaO content in the slag on dephosphorization and rephosphorization of molten steel were analyzed. The results showed that the dephosphorization ratio of more than 50% and the ultra-low phosphorus content of less than 0.005% in steel were obtained by the three kinds of dephosphorization fluxes as the oxygen potential of molten steel higher than 400×10-6. Rephosphorization of molten steel was serious as the oxygen content of molten steel lower than 10×10-6. BaO-based fluxes can improve the dephosphorization effect and reduce the phosphorus pick-up effectively under the condition of weak deoxidization of molten steel (the oxygen potential is about 100×10-6), but can not prevent rephosphorization under the condi- tion of deep deoxidization of molten steel (the oxygen potential less than 10×10-6).
基金Supported by Fujian Science and Technology Administration (2004I003 and 20060037)
文摘In this work,the effects of pH value of waste water and initial concentration of phosphorus on dephosphorization materials were investigated.The materials were prepared by shaping,sintering and hydrothermal reshaping oyster shell and silica micro-powder.Different concentrations of phosphorus-contained waste water were simulated with potassium dihydrogen phosphate solution,the effect of dephosphorization was tested with phosphomolybdenum blue spectrophotometer method,and the crystal phase and microstructure of materials were characterized by XRD and SEM methods.It was indicated that dephosphorization was completed in 6 h when the initial phosphorus concentration in waste water was lower than 15 mg/L,and the dephosphorization time prolonged as the increase of phosphorus concentration.It was observed that the pH value of waste water influenced dephosphorization significantly,and neutral subalkalic environment favored dephosphorization.When the pH value was 11,the efficiency of dephosphozation was the greatest.For waste water with an initial concentration of 20 mg/L,the dephosphozation rate is close to 100% in 8 h.
基金Sponsored by Provincial Natural Science Foundation of Anhui of China
文摘The vacuum treatment for simultaneous desulphurization and dephosphorization of hot metal and molten steel with pre-melted CaO-based slag was carried out. For pre-treatment of hot metal, both desulphurization and dephosphorization are improved with the increase of CaO in slag, but deteriorated with the increase of CaF2 in slag. The average desulphurization and dephosphorization rate is 68.83 % and 78.46 %, respectively. For molten steel, the substitution of BaO for CaO in slag has minor effect on simultaneous desulphurization and dephosphorization. The desulphurization and dephosphorization rate is higher than 90 % and 50 % respectively with the lowest final sulfur and phosphorus mass percent being 0.001 2 % and 0.010 %, respectively. The overall effect of simultaneous desulphurization and dephosphorization of molten steel is better than that of hot metal.
基金Project(59804003)supported by the National Natural Science Foundation of China
文摘Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high dephosphorization efficiency can be reached at the temperatures ranging from 1 200 to 1 400°C.When the monazite pellets,made by pressing mixture of the monazite,charred coal and water into mould,were roasted at 1 400°C for 2 h,98%of phosphorus was removed from the monazite pellets.The roast time has little effect on the dephosphorization efficiency.Meanwhile,the particle size of the charred coal also has great influence on the dephosphorization efficiency of the monazite,and it is better to control particle size around 150μm,while Fe and Fe2O3 have neglectable effect on the dephosphorization of the monazite.
文摘Laboratory study was carried out on deep dephosphorization of liquid steel by BaO-based fluxes at 1600℃ to achieve ultra low phosphorus level in the steel. A dynamic model of dephosphorization of liquid steel by BaO-based fluxes was established.According to the model, the controlling step of dephosphorization by BaO-based fluxes was the mass-transfer of phosphorus in steel phase under the condition of low phosphorus liquid steel. It is estimated that the apparent rate constant of dephosphorization by BaObased fluxes was 0.4×10-3-8.2×10-3 g/(cm2.s) and the mass-transfer coefficient of phosphorus in bulk steel was 0.025-0.04 cm/s.
基金the National Natural Science Foundation of China(Grant Nos.51704080,51874102 and 52074093)the National Key Research and Development Program of China(Grant No.2019YFC1905200).
文摘The reduction and recovery of P_(2)O_(5)in dephosphorization slag were examined to establish a new recycling process for dephosphorization slag.The dephosphorization slag is obtained from the dephosphorization furnace in the duplex converter process,and the content of P_(2)O_(5) in the dephosphorization slag can reach 9 wt.%.The dephosphorization slag is considered to be a prospective resource of phosphorus due to its high content of P_(2)O_(5).To explore the effects of temperature and Fe2O3 content in slag on phosphorus recovery from dephosphorization slag,the experimental slag was reduced by carbon powder in a resistance furnace.The results show that the temperature and content of Fe2O3 in slag have a significant effect on the reduction in P_(2)O_(5),and the reduction and recovery ratios of P_(2)O_(5) in slags increase with the increase in the experimental temperature and content of Fe_(2)O_(3),reaching 94.41%and 83.09%,respectively.It has been indicated that phosphorus recovery from dephosphorization slag using carbothermic reduction has significant environmental and economic benefits.
基金the National Natural Science Foundation of China(52104326)the Fundamental Research Funds for the Central Universities(N2225016)+1 种基金the Anhui Special Support Plan(T000609)the Distinguished Professor of the Wanjiang Scholars Project.
文摘Dephosphorization slag is one of the bulk solid wastes generated from steelmaking.If P is effectively removed from dephosphorization slag,a phosphate source which can substitute for phosphate rocks is obtained;meanwhile,the tailings can be reutilized as a feedstock in steel plant.To realize the integrated utilization of dephosphorization slag,selective leaching was applied for removing the P-bearing mineral phase from dephosphorization slag.Alkaline oxide was added as the slag modifier and HCl was selected as the acid lixiviant.The P selective leaching from dephosphorization slags modified by Na_(2)O or K_(2)O was studied at different pH values.By modification,the mass fraction of P in the_(2)CaO∙SiO_(2)–3CaO∙P_(2)O_(5)phase increased,indicating that it was in favor of P_(2)O_(5)enrichment.As the Na_(2)O or K_(2)O content increased,the P leaching ratio from slag increased at pH 4,reaching about 80%,and that of Fe was nearly zero.Na_(2)O and K_(2)O modification played a similar role in enhancing the P leaching.The effect of alkaline oxide modification became weak at pH 3,and the slag without modification also realized a good P selective leaching in the HCl solution.To facilitate the P removal,the leaching of Fe from dephosphorization slag needs to be restrained.
基金Item Sponsored by Inner Mongolia Natural Science Foundation of China(2011MS0726)Inner Mongolia University of Science and Technology Innovation Foundation of China(2009NC016)Inner Mongolia Key Laboratory for Utilization of Bayan Obo Multi-metallic Resources Foundation of China(BO-13-003)
文摘The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot metal meanwhile retaining Nb in the steel products remains a challenge. We carried out a thermodynamic study on dephosphorization of Nbbearing hot metal and investigated the effects of the initial [C] content and the dephosphorization temperature on oxidation behaviors of [Nb] and [P]. In particular, we focused on thermodynamic analysis of dephosphorization of Nb-bearing hot metal with highly basic BaO-based slag. The results showed that the highly basic BaO-based slag system is more suitable for dephosphorization under oxidative conditions, and increasing the [C] content favors dephosphorization of Nb-bearing hot metal without oxidizing [Nb]. Moreover, the values of equilibrium oxygen activity for oxidation reactions of [Nb] and [P] are increased as the dephosphorization temperature increases. Considering the hot metal containing 0.02% of [Nb] in Baotou Steel, thermodynamic calculations indicated that the content of [P] can be reduced to 0.02%–0.05% and [Nb] remains unoxidized when dephosphorization occurs at the cconditions of T=1573–1673 K, [C]=4.0%, [Nb]=0.02%, aP2O5=10-24, aNb2O5=10-10.
文摘Development of the efficient hot metal dephosphorization processes during steelmaking process is one of the most essential topics for the production of high grade clean steels. Since the formation of solid solution composed of tricalcium phosphate and dicalcium silicate could obtain a considerable mass transfer of phosphorus from liquid slag into solid phase during hot metal dephosphorization, itcould obviously sustain a high phosphatecapacityof theliquid slag without huge consumption of lime or addition of fluxes, such as fluorite. The above outlines are the main idea of multi phase flux dephosphorization. For the last few decades, many studies have been done towards the scientific principles and the commercial utilization of this technique. However, the reaction mechanism by using multi phase fluxes remains unclear even by now due tolack of evidence. Based on those previous works, providing a reliable and available phase diagram for the fundamental understanding of the reaction mechanism of multi phase flux dephosphorization has become the main purpose of present research. As well known, the CaO-SiO2-FeO-P2O5 slag is the main component of current steelmaking process. Hence the CaO-SiO2-FeO-P2O5 system at equilibrium has been studied at 1673K with low oxygen partial pressure. The solid phase coexisting with liquid flux is approved to be the solid solution composed of CaO, SiO2 and P2O5. Phosphorus distributes mainly in solid solution rather than liquid phase.
