Reduction Of Slag Research Articles

Process Improvement for Liquid-Phase Metal Reduction from Steelmaking Dump Slags

Background/Objectives: This work was aimed at experimental studying the laboratory process and the results of liquidphase carbon (coke) reduction of the steelmaking slag conducted to obtain the metal and oxide phases which can be used in the metallurgical industry and building materials industry. Methods: The slag from the slag dumps of Zlatoust Metallurgical Plant (the Russian Federation) was an object of the study. The composition of the experimental samples of metal and slag was determined by electron probe microanalysis. Findings: The conducted experiments give grounds to assert that the process allows recovering almost completely iron, chromium and nickel contained in the slag. Major part of manganese, as well as some other components, including valuable elements – tungsten, molybdenum, titanium and vanadium, also passes into the molten metal. It has been shown that liquid-phase recovery of slag is acceptable to be carried out at temperatures of about 1500-1550°C. In this case, the slag reduction time (after heating the mixture up to the operating temperature) should not exceed 30 minutes. For a more complete recovery of valuable metals it is recommended to use the moment of the ‘boiling’ (intensive separation of gaseous carbon oxides) period completion as an indicator of the isothermal time end. Improvements/Application: Useful products of the recovery process are liquid metal and heavy metal-depleted oxide melt consisting mainly of calcia, silica, magnesia and alumina which may be used in cement manufacturing.

Influence of Selected Parameters on Reduction of Converter Slag - Studies with CFD Method

Abstract In this study influence of selected parameters on the process of reduction of converter slag from refining of Cu-Pb-Fe alloy was numerically examined. The process of the slag reduction is carried out in Q 80 converters of Hoboken type for copper removal. Converter slags show high concentration of lead therefore they can be seen as an important component for further processing in rotary-rocking furnaces together with other lead-bearing materials. Three-dimensional simulation was performed using the IPSA (Inter Phase Slip Algorithm) module of two-phase flow from PHOENICS package. Numerical simulations have forecasted influence of changes in the slag chemical composition and the process time on the process course.

Slag Formation – Thermodynamic Aspects and Experimental Observations

AbstractSlags have a central role in pyro-metallurgical processes. They bind impurity compounds and absorb reaction products like oxides and sulfides. Functional slags are made by adding lime, magnesia, fluorspar, bauxite, calcium aluminate or other compounds into the reactor vessel where they form the slag together with the targeted reaction products. Additionally, refractory materials of the vessel tend to dissolve into the slag and thus influence its properties. Converter process for steelmaking is a rapid process and slag formation is extremely essential to ensure slag’s metallurgical functions and to avoid harmful reactions with the refractory materials. In this contribution, the progress of understanding the phenomena controlling slag formation and means to promote it were shortly reviewed. Thermodynamic constraints in slag formation were examined and the influence of fluxing additions was experimentally stated. Prefabricated “self-fluxing” lime was tested in industrial scale and proved to be a potential slag forming agent. Slag formation in secondary metallurgy and reduction of slag with aluminum dross or granules were experienced, and the effect on desulfurization and steel cleanliness was discussed.

Recycling of High Ferrous Bauxite Reducing Slag for Synthesis of CaAl2 Si2 O8-Al2 O3-CaAl12 O19 Composite

CaAl2Si2O8-Al2 O3-CaAl12O19 (CAS2-Al2 O3-CA6) composite was synthesized through reaction sintering alumina and bauxite reducing slag. The CAS2-Al2O3-CA6 composite was mainly composed of α-Al2O3, CAS2, and CA6. Gehlenite (Ca2 Al2SiO7, C2AS) phase was effectively transformed to CAS2 and CA6 through high-temperature reaction sintering under weak oxidizing atmosphere at 1400 °C for 4 h. SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) analysis indicated that black and needle-shaped Al2 O3, rhombic or irregular polygonal-shaped FeAl2 O4, and glassy phase Ca2 Al2SiO7 disappeared after the reaction sintering. The light gray and flaky hexagon crystals of CaAl12 O19 (10 μm) and the grainy particles of Al2O3 (2–7 μm) were observed in the CAS2-Al2O3-CA6 composite. The gray crystals of CAS2 act as the binding phase and are distributed around CA6 and Al2O3. CAS2-Al2 O3-CA6 composite exhibits high refractoriness and service temperature, which are 1650 °C and 1450 °C, respectively. Reaction sintering of alumina and bauxite reducing slag is a feasible method for the synthesis of CAS2-Al2 O3-CA6 composite.

Extraction of iron from copper-plant slag

In the production of copper from sulfide ore, slag accumulates at the processing plant. In the present work, the phase transformations that occur in such slag during its reduction by the gasification products of carbon at 1100 and 1200°C are investigated. Experiments show that most of the iron present in such slag may be converted to metallic form by the gasification products of carbon in cupola furnaces at 1100°C. Subsequent increase in temperature to 1200°C improves the extraction of iron. In the indirect reduction of slag at temperatures above its melting point, metallic iron is mainly concentrated at the outer surface of the product, forming large inclusions that are easily extracted by magnetic separation. An expedient approach is to reduce laminar batch consisting of slag layers no thicker than 5 mm and interlayers of ground coal.

Smelting reduction of MgO in molten slag by liquid ferrosilicon

The smelting reduction of magnesium oxide was researched in this paper. The effect of molten slag composition and reduction temperature on percent reduction of magnesium oxide were discussed, and kinetics of smelting reduction of magnesium oxide in molten slag was studied. The results showed that the reduction extent of magnesium oxide increased by increasing either one of the following factors: the initial mass ratio of Al 2 O 3 /SiO 2 , the addition of CaF 2 , the initial molar ratio of Si/2MgO, and reaction temperature. The overall smelting reduction was controlled by mass transfer in slag with an apparent activation energy 586 kJ mol -1 .

Thermogravimetric study of the reduction of copper slag by biomass

The utilization of copper slag is an attractive option of iron resource. However, extra energy consumption is required and contributes to greenhouse gases. In this paper, biomass was introduced as a new kind of reductant for the reduction of copper slag to decrease the energy consumption. The reduction kinetics and reduction characteristics of three kinds of biomasses were studied by thermogravimetric analyzer (TG). The TG curves showed the reduction reaction of copper slag and biomass could be divided into three stages during heating process: drying and pyrolysis of biomass process ( 1100 K). Pine sawdust showed the best reducing property and the reduction ratios of pine sawdust, corncob and straw reached to 80.6, 76.1, and 60.0 %, respectively, when the mass ratio of biomass/slag was 2:1. As the additive, CaO had promotion effects on the reduction reaction. With the increase in CaO addition, the reduction ratio of copper slag increased firstly and reached a peak at CaO/slag was 0.3:1 and then it declined due to the changes of slag viscosity. By kinetics analysis, the reduction reaction confirmed well with shrinking core model (R1). The activation energy of reactions was affected by the addition of biomass and heating rate in experiments. With the increase in the addition of biomass, the activation energy of reduction reaction increased gradually; with the increase in heating rate, the activation energy of reduction reaction decreased.

Complex Processing of Industrial Products and Lead-Copper Concentrates

This article describes the modern technologies of processing of industrial products and copper-lead waste products, and their physical and chemical properties as well as laboratory tests for processing slurries and zinc slags. Experiments have shown that the temperature of the melt in the reduction of lead-containing slag should be within 1100–1200 °C. The key criteria for separating melting products to different phases are the difference in density, viscosity and surface tension of the melted slag. The separation of the molten slag to the phases and the reduction of the settling time of the melt in the furnace will be promoted by the increasing the density and surface tension of the lead and matte-molten slag, and reduction in viscosity of the latter. The processing of lead-copper-zinc containing sulfide raw material was carried by the reduction smelting method and the purging of melt with a natural gas at a rectangular electric furnace. Dust collection system was connected to the furnace through the duct work. The feedstock loading was carried out through the furnace crown. The purging of melt with natural gas was performed after the melting of the charge using the immersed gas supply tube. The gaseous products were derived from the melting furnace through the flue. The gas supply tube was fitted with a gear system to adjust the depth of the tube immersion. As results of experiments were obtained sharply separable intermediates with a high degree of concentration: lead into lead bullion to 92–94%; copper into matte to 90–91%; zinc to the slag and sublimates to 94–96%. Thus the material costs for processing of copper matte and zinc slag will be reduced and the yield of sublimates consisting primarily of vapor and metallic zinc sulfide will be decreased.

환원슬래그를 사용한 모르타르의 저온에서의 초기동해 방지에 관한 기초적 실험

In this research, it used cement powder and reduction slag, which generates high hydration heat in hydration reaction without heat cure below degree. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature due to own heat of concrete. and it is the result of physical characteristic and thermal property evaluation of reduction slag. Because reduction slag generates high hydration heat, compressive strength development is excellent. By generating highly hydration heat by and in reduction slag, compressive strength is developed in low temperature. In case of displacing only reduction slag without , it is indicated that quick-setting occurs by shortage of . For preventing quick-setting, gypsum is used essentially. According to this research result, in case of using reduction slag and gypsum as a ternary system, compressive strength developed 5MPa in 3 days below zero temperature. It is identified to prevent early frost damage of concrete below zero temperature.

환원슬래그를 사용한 모르타르의 저온에서의 초기동해 방지에 관한 기초적 실험

In this research, it used cement powder and reduction slag, which generates high hydration heat in hydration reaction without heat cure below –5℃ degree. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature due to own heat of concrete. and it is the result of physical characteristic and thermal property evaluation of reduction slag. Because reduction slag generates high hydration heat, compressive strength development is excellent. By generating highly hydration heat by C 12 A 7 and C 3 A in reduction slag, compressive strength is developed in low temperature. In case of displacing only reduction slag without SO 3 , it is indicated that quick-setting occurs by shortage of SO 3 . For preventing quick-setting, gypsum is used essentially. According to this research result, in case of using reduction slag and gypsum as a ternary system, compressive strength developed 5MPa in 3 days below zero temperature. It is identified to prevent early frost damage of concrete below zero temperature.

Mechanism and kinetics of the carbothermic reduction of titanium-bearing blast furnace slag

The carbothermic reduction experiments were carried out for titanium-bearing blast furnace slag from Panzhihua Iron and Steel Company in argon atmosphere at high temperatures. The effects of reduction temperature, isothermal treatment time and carbon particle sizes on the formation of TiC were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The SEM pictures show that the size of C has little influence on the particle size of TiC. The experimental results show that the shrinking core model is applicable and the carbothermic reduction is controlled by the chemical reaction. The apparent activation energy of reaction could be obtained to be 69.16 kJ/mol.

FEATURES OF THE APPLICATION OF NATURAL AND MAN-MADE MATERIALS FOR MICROALLOYING AND MODIFYING OF STEEL

The article is devoted to the study of the peculiarities of microalloying processes and steel modification with technogenetics and natural materials. The authors have researched metallurgical properties of barium-strontium natural modifiers and have estimated its influence on the melting temperature of the forming reducing slag. The received data have shown that the usage of the modifier in the conditions of industrial production is highly producible. Using the software package TERRA the assessment of barium and strontium reducibility with silicon and aluminum from their oxides has been fulfilled, as well as the possible mechanisms of a modifying influence of barium and strontium on the quality of metal has been studied. The possibilities of using vanadic converter slag have been shown for steel microalloying with vanadium. Efficiency assessment of vanadium reduction with carbon of the molten steel has been done. The authors have given the data of industrial testing of the studied materials, which have shown very good convergence with the theoretical calculations and conclusions. The recommendations to optimize the technology of mictoalloying and modification have been given. The use of the researched materials allows improving technical and economic indices of steel production process and significantly increases the quality of the end production. The conclusions on the perspective significant widening of using the technogenetics and natural materials have been done.

Effect of Basicity on Electroreduction with Controlled Oxygen Flow of Molten Slag Containing FeO

This paper reports on electroreduction with controlled oxygen flow (COF) for extraction of iron along with oxygen by-product from molten slags containing iron oxide at 1723 K. An electrolytic cell with COF was constructed by an iridium wire cathode and a porous platinum anode sintered on a one-end-closed magnesia-stabilized zirconia-based solid electrolyte tube. Effect of basicity of SiO2–CaO–Al2O3–MgO–FeO slag on electroreduction behavior of FeO was investigated by means of the linear sweep and the potentiostatic electrolysis. The possibility of the zirconia membrane as conductive noncorrosive anode material was also discussed. The results indicate that both cathode alloying and increasing slag basicity are helpful to the FeO electrolytic reduction in the molten slag. With the iridium wire as a cathode and an applied voltage at 2.5 V, higher slag basicity results in higher electrolysis rate and higher reduction ratio of the FeO; however, silicon is also precipitated during electrolysis. The applied voltage can cause the increased porosity in the zirconia membrane. The corrosion of the molten slag to the zirconia membrane during electrolysis is evidently aggravated when the slag basicity reaches 0.8. In order to minimize the corrosion of the molten slag to the zirconia membrane during electrolysis, the slag basicity of 0.6 is relatively advisable for extraction of iron under conditions of experimentation.

ELECTROCHEMICAL BEHAVIOR OF Ni2+ IN SiO2-CaO-MgO-Al2O3 MOLTEN SLAG AT 1673 K

The modern iron and steel industry produces large emissions of CO2 annually. Electrolytic reduction of molten slag containing iron oxide at high temperature using an inert oxygen evolving anode is an alternative process to reduce or eliminate the formation of CO2. In order to establish reasonable process parameters of electrolytic method for steel containing Ni, it is necessary to master the electrochemical behavior of Ni + in molten slag. However, investigations on the electrochemical behavior of Ni in molten slag at higher temperatures were very limited, which can probably be attributed to the experimental difficulties associated with the operation of high-temperature electrochemical cells. An electrolytic cell with a controlled oxygen flow and Pt, O2(air)|ZrO2 used as reference electrode was constructed integrally through a one-end-closed magnesia partially stabilized ZrO2 solid electrolyte tube. Electrochemical behavior of Ni + on Ir electrode was investigated in SiO2-CaO-MgO-Al2O3 molten slag at 1673 K by means of electrochemical techniques such as cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and potentiostatic electrolysis. The results show that both diffusion in the molten slag and electromigration in the ZrO2 solid electrolyte for the O are not rate-determining steps of electrochemi*国家自然科学基金项目51174148和武汉科技大学大学生科技创新基金研究项目14ZRA004资助 收到初稿日期: 2015-01-22,收到修改稿日期: 2015-04-27 作者简介:洪川,男, 1990年生,硕士生 DOI: 10.11900/0412.1961.2015.00065 第1001-1009页 pp.1001-1009

Response characteristics of iron smelting reduction of copper slags

The response characteristics of iron smelting reduction of copper slags were studied in this paper. With the molten slag basicity of 1·4, the γ (FeO) takes nearly a maximum value equalling to 4·27. The diffusion of (FeO) through the molten slag boundary layer to the molten slag–iron interface is found to be the rate-limiting step for the process of (FeO) smelting reduction. In a certain range, the iron smelting reduction rate increases obviously with the increase of residence time and reductant addition amounts. Result of iron smelting reduction rate of 93·64% is obtained in the optimal conditions: (i) N2 flow rate of 0·3 L min−1; (ii) molten slag basicity of 1·4; (iii) holding temperature of 1848 K; (iv) residence time of 30 minutes and (v) the reductant addition amounts of 1·2 (mass ratio of the anthracite and copper slags).

A New Technology for Copper Slag Reduction to Get Molten Iron and Copper Matte

The change of iron composition as well as the removal of copper from iron was investigated in the reduction process, and a new way to deal with copper slag was proposed. The iron in copper slag exists mainly in the form of fayalite, and the copper sulfide content accounts for just about 50%. Therefore, the magnetic separation as well as grinding floatation method is not suitable, and a pyrogenic treatment on copper slag is necessary. The carburization and desulfurization process is restricted to a degree within the carbon composite pellets, and copper matte phase precipitates from copper slag in the reduction process, which is immiscible with molten iron and slag. The copper content decreases to 0.4 % as the carbon content in molten iron reaches 3. 84 %, and the removal ratio of copper from molten iron approaches to 80%. The reduction and sulfurization process can be completed in one step, and the copper is separated from iron based on the ternary system of iron-matte-slag.

Carbothermic Reduction of Titanium-Bearing Blast Furnace Slag

AbstractThe carbothermic reduction experiments were carried out for titanium-bearing blast furnace slag in Panzhihua Iron and Steel Company in argon atmosphere at high temperatures. The effects of reduction temperature, isothermal treatment time and carbon content on the formation of TiC were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD pattern results showed that MgAl2O4 phase disappeared and the main phase of the reduced sample was TiC when the reduction temperature was higher than 1,773 K. The SEM pictures showed that the reduction rate of the titanium-bearing blast furnace slag could be increased by enhancing the temperature and the C content (carbon ratio ≤1.0). Furthermore, it was also found that TiC had the tendency of concentrating around the iron. The effects of additives such as Fe and CaCl2 on the formation of TiC were also studied in the present study.

전기로 환원슬래그를 제조 원료로 사용한 개량형 C12A7 광물계 급결제 및 성능 평가

전기로 환원슬래그를 제조 원료로 사용한 개량형 C12A7 광물계 급결제 및 성능 평가

A Comparison Study of the Oxygen-Rich Side Blow Furnace and the Oxygen-Rich Bottom Blow Furnace for Liquid High Lead Slag Reduction

This work investigates the characteristics of the oxygen-rich side blow furnace (OSBF) and the oxygen-rich bottom blow furnace (OBBF) as the reductive smelting reactor for molten high lead slag. The slags were collected from different sampling points of these furnaces during a regular high lead slag reduction process and analyzed. It is disclosed that lead content of the melt in the OSBF shows dramatic fluctuations, while melt from different sampling points of the furnace behave similarly, exhibiting the characteristics of batch reactor. An obvious axial lead content gradient is detected in the OBBF, showing the characteristics of a plug flow reactor. The industrial performances of these furnaces are also compared. The results indicate that 1.38% higher lead recovery can be achieved by using the OSBF instead of the OBBF. Unit energy consumptions of the OBBF–OSBF and OBBF–OBBF processes can be reduced to 230 kgce/t crude lead, which is 70 kgce/t crude lead less than that of the tradition Shuikoushan (SKS) process.

Study on Direct Reduction of Vanadium Slag

In this paper the process of direct reduction of vanadium slag was adopted. The main factor was determined by uniform experimental design and single factor analysis, and then the optimum process condition was drawn by the test. The test results showed that the regression equation curve fitting of the experiment data was very significant, the main factors affecting the vanadium slag reduction (according to the primary and secondary order) was the content of anhydrous sodium carbonate, roasting temperature, roasting time and reduction of carbon content. The factors for the reduction of the optimum process conditions are the carbon coefficient 1.04, roasting temperature 1100°C, roasting reduction time 4h, 4% mass percent of anhydrous sodium carbonate and slag. Under the optimum conditions, the actual rate of weight loss and theory rate of weight were close to 0, the results could be reproduced, and the vanadium slag metallization rate was 75%~83%.