BF Slag Research Articles

BF slag resistance of β-Si3Al3O3N5 material derived from Al salt cake

Abstract In the process of recycling of salt cake from secondary aluminium smelting, it was shown that a significant value addition can be made as β-Si 3 Al 3 O 3 N 5 could be successfully synthesized from the rest product after water-leaching by silicothermal reduction method. In order to evaluate its refractory application, the corrosion behavior in blast furnace slag was investigated under static condition at 1400–1480 °C in the present work. The results show that the β-Si 3 Al 3 O 3 N 5 material has good slag resistance. The apparent activation energy obtained for corrosion process is −388.7 kJ/mol, revealing a more complicated dissolution mechanism. The corrosion process is started with the dissolution of intergranular phase including the iron silicides and glassy phases in the specimens, which is aided by the softening at high temperature and the continuous attack from slag, then followed by the dissolution of β-Si 3 Al 3 O 3 N 5 grains in the slag.

Progress in Molten Blast Furnace Slag Treatment Using Dry Centrifugal Granulation Technology

The molten blast furnace slag (BF slag) is discharged at the temperature of about 1400-1550 °C, which contains a large amount of heat. At present, water quenching is the main technology to treat the BF slag, but this method not only consumes a huge amount of water, but also fails to recover the waste heat. Compared with water quenching, the dry centrifugal granulation has obvious advantages. There is no water consumed and the waste heat can be recovered efficiently, thus this technology has great potential. This technology mainly contains two processes: the granulating process and the heat recovery process. The present development statuses on those two processes are summarized respectively and the prospect of dry centrifugal granulation technology is forecasted.

The technological calculation for synergistic system of BF slag waste heat recovery and carbon resources reduction

In order to achieve the conversion and utilization of BF slag waste heat and CO2-rich industrial waste gas, a synergistic system was proposed. The methods of technological calculation and exergy analysis were conducted to determine the performance of the gasifier in the system using the coal/waste gas gasification reaction to recover the BF slag waste heat. Above 85% BF slag waste heat was recovered, and the exergy efficiency reached 78.38% in molten and granules slag gasifiers, and about 80% CO2 was converted to syngas in the waste gas. In the coal/waste gas gasification process, the BF slag was used as heat carrier to guarantee the gasification reaction. The physical heat of the BF slag and chemical heat of coal were converted to the chemical and physical heat of syngas. The syngas physical heat was also recovered by heat exchanger to produce steam in the system. The waste heat of one ton BF slag at 1773K was also calculated in the system consuming about 44.55kg/tslag Datong coal, 146.12m3/tslag industrial waste gas, and generated about 120m3 syngas. In the whole system, the BF slag waste heat was converted and utilized, and the CO2-rich waste gas was recycled. The energy consumption and CO2 emission were decreased in iron and steel enterprise, so as to achieve the objective of energy saving and emission reduction.

Preparation of Ti–Si–Al alloy by aluminothermic reduction of TiO2 bearing blast furnace slag

The aluminothermic reduction of Ti containing BF slag was carried out to prepare Ti–Si–Al alloy in this study in order to improve the recovery rate of the Ti from the vanadium–titanium magnetite ore and solve the deposit problem of huge amount of BF slag bearing 20–25%TiO2. It was found that the mass of alloy increased with increasing Al addition. The mass of the slag obtained was more than that calculated by FACTSage by 2–4%, meaning some unreduced oxide still remained in the slag, and/or that equilibrium was not obtained. The Perovskite and Pyroxene minerals disappeared, and the CaAl2O4 and MgAl2O3 were the dominant phases with increasing the Al2O3 in the slag. The Ti5Si3, AlTi3 and TiSi2 were the main phase in the solidified alloy. The LFe, LSi, and LTi, which represents the distribution ratio of the elements like Fe, Si and Ti between the metal and the slag, decreased with increasing temperature, and increased with increasing the Al addition. The measured LFe departed greatly from the equilibrium, while the measured LSi almost reached the equilibrium. The LTi reached the equilibrium when the Al addition was less than 18%, LTi departed from the equilibrium condition when the Al addition was more than 18%. The recovery of both Ti and Si increased with increasing the Al addition. For Ti, it reached 80% when the Al addition was above 20%. For Si, the recovery is always lower than that of Ti, it reached 70% when the Al addition was above 24%.Dans cette étude, on a effectué la réduction aluminothermique de laitier de haut-fourneau, contenant du Ti, pour préparer l’alliage de Ti-Si-Al afin d’améliorer le taux de récupération du Ti de minerai de vanadium-titanium-magnétite et de résoudre le problème de dépôt d’une quantité énorme de laitier de haut-fourneau porteur de ∼20–25% de TiO2. La masse de l’alliage augmentait avec l’augmentation de l’addition d’Al. La masse du laitier obtenu était plus importante que la masse calculée par FACTSage par ∼2–4%, indiquant qu’une certaine quantité de l’oxyde non-réduit subsistait dans le laitier et/ou que l’on n’avait pas atteint l’équilibre. Les minéraux de Pérovskite et de Pyroxène ont disparu et le CaAl2O4 et le MgAl2O3 constituaient les phases dominantes avec une augmentation de l’Al2O3 dans le laitier. Le Ti5Si3, l’AlTi3 et le TiSi2 constituaient la phase principale de l’alliage solidifié. Le LFe, le LSi et le LTi, qui représentent le rapport de distribution des éléments comme le Fe, le Si et le Ti entre le métal et le laitier, diminuaient avec une augmentation de la température et augmentaient avec une augmentation de l’addition d’Al. Le LFe mesuré s’éloignait grandement de l’équilibre, alors que le LSi mesuré atteignait presque l’équilibre. Le LTi atteignait l’équilibre lorsque l’addition d’Al était de moins de 18%, le LTi s’éloignait de la condition d’équilibre lorsque l’addition d’Al était de plus de 18%. La récupération tant du Ti que du Si augmentait avec l’augmentation d’addition d’Al. Quant au Ti, il atteignait 80% lorsque l’addition d’Al était au-dessus de 20%. En ce qui concerne le Si, la récupération était toujours plus faible que celle du Ti; elle atteignait 70% lorsque l’addition d’Al était au-dessus de 24%.

Mechanism of Dry Molten Slag Granulation Using a Rotating Multi‐Nozzle Cup Atomizer

AbstractAs the main by‐product in the iron‐making process, blast furnace slag (BF slag) contains a high amount of sensible heat which is a potential heat source with great value if treated properly. Although several technologies have been investigated during recent decades, few of them can be commercialized successfully.In the previous study, we developed a rotating multi‐nozzle cup atomizer (RMCA) for granulating the molten slag. The particle size distribution of the produced slag particle is narrow, the shape is spherical, and the degree of non‐crystallization is over 95%. In the current study, the models of the disintegration mechanism, the traveling trajectories and the temperature profile of the slag droplet are established. The particle size is analyzed theoretically and then compared with experimental results. It is found that the predicted results agreed with the experimental results very well. The models can provide guidance for designing commercialized atomizer and optimizing the operation parameters.

Evaluation of industrial wastes as sources of fertilizer silicon using chemical extractions and plant uptake

AbstractSix inorganic industrial‐waste materials (coal fly ash, bauxite‐processing mud, steel slag, two samples of air‐cooled blast furnace [BF] slag, and one sample of water‐cooled BF slag), along with wollastonite, were evaluated as fertilizer‐Si sources. Evaluation was carried out by analyzing total and extractable Si fractions in the materials, by incubating them at two rates with a Si‐deficient soil and measuring potentially available extractable Si and by measuring yield and Si uptake by two successive rice crops grown in the fertilized soils. Of the waste materials used, fly ash had the highest total Si content (29%) but a negligible quantity was present in extractable forms. Steel slag and bauxite‐processing mud had only 5%–7% Si content while BF slags contained 14%–18% Si. All materials, other than fly ash, increased the amount of extractable Si present in the soil. Additions of steel slag and bauxite‐processing mud caused greater increases in Si extractability than the air‐cooled BF slags while water‐cooled BF slag–treated soils contained notably high acid‐extractable Si. Because of the alkaline nature of the materials, and their reaction products, there was a positive relationship between extractable soil Si and soil pH. However, an equilibration experiment using NaSiO3 as the Si source confirmed that Si solubility in the soil decreased with increasing pH. Dry‐matter yields of rice, at the lower rate of Si addition, were increased by all treatments other than fly ash. The higher rates of steel slag and bauxite‐processing mud caused yield depressions. Total Si uptake by rice was increased by all treatments, other than fly ash, and was greater at the higher rate of Si addition. It was concluded that the BF slags are the most effective waste materials as fertilizer‐Si sources and that, in slag‐amended soils, CaCl2 and NH4 acetate are the most reliable soil‐test extractants.

A Study on the Carbon Nitriding Process of BF Slag Containing Titanium

The experiment was done in which the BF slag containing titanium produced by Pangang with vanadium-titanium magnetite was dealt with carbon and nitrogen. The possibility of the carbon nitriding reactions were analyzed theoretically. It is found by thermodynamic calculation that the carbon nitriding of TiO2 is easier than that of other oxides and the temperature of carbon nitriding of perovskite can be reduced with the presence of Al2O3 and SiO2 in slag. The phase composition and microstructure of production from carbon nitriding were studied using X-ray diffraction and SEM. It is approved that the main phase composition of production from carbon nitriding under N2 was Ti(C,N). The influence factors, temperature, holding time and particle size were investigated. The results show, the phase compositions of the slag is mainly perovskite; the most suitable temperature and holding time of carbon nitriding is about 1450°C; the most appropriate holding time was about 2 hours and the most suitable size of the slag particle is about 180 meshes. With the optimization of the process, the size of Ti(C,N) can be increased which will benefit the recycle of Ti(C,N) in ore dressing.

Cognition on the Molten Blast Furnace Slag Granulation Techniques in Contemporary China

Introduce characters and applications of granulation techniques of the molten blast furnace slag in contemporary China, describe characters and design ideas of two types of granulation boxes, represent three types of circulating granulation water systems, put forward matching proposal between the molten slag granulation system and the circulating granulation water system, analyze contemporary research and problems of waste heat recovery of the molten BF slag.

Influence of B2O3 on Viscosity of High Ti-bearing Blast Furnace Slag

The influence of B2O3 on the viscosity of high Ti-bearing BF slag is studied under Ar atmosphere from 1 773 K (1 500 degrees C) to about 1 593 K (1 320 degrees C). The results show that the additio ...

Calculating Model of Fe<sub>t</sub>O Activity in Alkali-Containing BF Slag

The FetO activity calculating model of alkali-containing BF slag was built according to the coexistence theory of slag structure at 1773K. The results reveal: it is correspond to reality and embody the structural characteristics of BF slag. The FetO activity of slag increases obviously with the w(CaO)/w(SiO2) increasing, decreases with the Al2O3 and MgO contents increasing.

Study on Viscosity of Titania Bearing Blast Furnace Slag

The viscosity of blast furnace slag which was taken from Shuicheng Iron and Steel Group Co. Limited was experimentally measured by column whirling method using the ND-II slag viscosity tester. By adding analytical reagent CaO, SiO2, Al2O3, MgO and TiO2 in accordance with orthogonal design, the contents of compositions in slag were adjusted in CaO/SiO2=1.16-1.24, 14.06-17.06mass%Al2O3, 5-7mass%TiO2, 8.96-9.96mass%MgO. The results showed that the viscosity of BF slag decreased with increasing TiO2; when the Al2O3 content in the slag was 14.06%, the viscosity of BF slag had a lowest value, a highest value had for 15.56% Al2O3 content, and a lower value for 17.06% Al2O3 content. There is no significant effect on the viscosity by both the magnesia and the binary basicity.

Recovery of Calcium from BF Slag and Synthesis of Zeolite A Using Its Residue

Recovery of Calcium from BF Slag and Synthesis of Zeolite A Using Its Residue

A Study on the Viscous Behaviour with K2O Additions in the CaOSiO2Al2O3MgOK2O Quinary Slag System

AbstractThe viscosities of CaOSiO220wt%Al2O310 wt%MgO‐K2O quinary slags with CaO/SiO2 from 0.8 to 1.2 at 1773 K with 1–5 wt% K2O additions were measured to estimate the effect of K2O on the viscous behaviour of the slags. The measured viscosity at 1773 K increased with K2O addition at a fixed CaO/SiO2, which is contrary to the effect of Na2O on the viscosity of BF slags. To qualitatively verify the changes in slag structure, FT‐IR spectroscopy was used. It was found that K2O induces Al2O3 to behave as an acidic oxide by forming [AlO4]5−‐tetrahedral units by the ionic compensation effect of K+ cations. However, regarding the effect of K2O on the silicate structure, it is observed that K2O has a negligible effect due to the consumption of O2− with the formation of [AlO4]5−‐tetrahedral units. Furthermore, it is also found that SiOAl bending became more complicated with K2O additions, which supports the selective effect of K2O on the aluminate structure of the slag. In spite of the more complicated structure with K2O additions, the critical temperature (TCR) decreased due to the gradual reduction of the liquidus temperature (TLQ) of the slags.

The removal of heavy metal ions from spiked aqueous solutions using solid wastes—Comparison of sorption capability

The removal of heavy metal ions from spiked aqueous solutions using solid wastes was explored in this work. The sorption capabilities of the sorption agents were compared and evaluation of an agent to replace activated carbon was performed. Experimental results indicated that rice hull ash was effective for sorbing Cd ion; all the solid wastes employed, for removing Cr ion; activated carbon and BF slag for uptaking Cu ion; activated carbon and rice hull ash, for removing Pb ion; activated carbon, activated clay, BF slag and rice hull ash, for abating Ni ion. Rice hull ash was found to be an alternative sorption agent to substitute costly activated carbon for abatement of heavy metal pollution in wastewater.

Experimental Study on Heat Transfer Characteristics of Apparatus for Recovering the Waste Heat of Blast Furnace Slag

Dry granulation, as a new process of molten BF slag treatment, is an attractive alternative to water quenching. The medium in the heat exchanging process is air which results in low efficiency. Therefore, the technique for waste heat of molten BF slag recovery is exploited. The waste heat is recovered by waste heat boiler which produces high pressure steam for generating electricity. The heat transfer characteristics of apparatus were investigated. The results show that the overall heat transfer coefficient can reach 111W/ (m2•K) and the heat recovery can reach 90% at most. If slag granule diameter is less than 2.5mm and descending velocity is higher than 1.0mm/s, the cooling rate of slag granule is over 10K/s. Then slag granules can be used as nicer materials to produce Portland cement. When slag granule descending velocity equaled to 1.1mm/s and the flux of water equaled to 0.15m3/h, small quantity of steam appeared in the first and second row tubes. They proved the feasibility of this technique. The application of this technique has a significant social meaning.

Feasibility Study for the System of Coal Gasification by Molten Blast Furnace Slag

At present, molten blast furnace slag is quenched rapidly using a large amount of water to produce a glassy-granulated slag without any recovery of its much sensible heat, polluting water and atmosphere. To solve these problems, a new heat recovery system is proposed. This system consists of melting gasifier, the 2nd gasifier and boiler in order to achieve stepped energy using. The melting gasifier and the 2nd gasifier use the endothermic heat of gasification reaction instead of sensible heat to recover the energy of molten blast furnace slag. The possibility of the new heat recovery system is studied. The reactions in melting gasifier are studied using STA409PC thermal analyzer and HSC chemistry software. The economic and environmental benefits are calculated based on the heat and mass balances. The results indicate that this method is possible and better than conventional methods such as hot water or steam production. The molten BF slag acts as not only thermal media but also good catalyst. The efficiency of melting gasifier is high and without pollution. Besides, this method can bring huge economic and environmental benefits which are important to the survival and sustainable development of iron-steel enterprises.

Numerical simulation of the temperature field of titania-bearing BF slag heated in a microwave oven

Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the specimen is studied by numerical simulation. The temperature in the center of the cylindrical slag specimen is the highest and the temperature decreases when the radius increases rapidly. In this case, the temperature rising rate decreases with heating time rapidly, and it tends to zero when the heating time is up to 150 s.

Sulfur Flow Analysis for New Generation Steel Manufacturing Process

Sulfur flow for new generation steel manufacturing process is analyzed by the method of material flow analysis, and measures for SO 2 emission reduction are put forward as assessment and target intervention of the results. The results of sulfur flow analysis indicate that 90% of sulfur comes from fuels. Sulfur finally discharges from the steel manufacturing route in various steps, and the main point is BF and BOF slag desulfurization. In sintering process, the sulfur is removed by gasification, and sintering process is the main source of SO 2 emission. The sulfur content of coke oven gas (COG) is an important factor affecting SO 2 emission. Therefore, SO 2 emission reduction should be started from the optimization and integration of steel manufacturing route, sulfur burden should be reduced through energy saving and consumption reduction, and the sulfur content of fuel should be controlled. At the same time, BF and BOF slag desulfurization should be optimized further and coke oven gas and sintering exhausted gas desulfurization should be adopted for SO 2 emission reduction and reuse of resource, to achieve harmonic coordination of economic, social, and environmental effects for sustainable development.

Separation of Iron Droplets From Titania Bearing Slag

Owing to smelting vanadium-titanium magnetite ore, the amount of iron entrainment in slag as droplets is far higher than that in conventional BF slag. However, the iron droplets can be easily settled by blowing air into the molten slag. The results show that more than 80% of iron droplets in titania bearing slag can be settled and separated after treatment. The temperature rise of molten slag during the oxidizing process and the decreased viscosity caused by the component change of slag as well as air stirring in slag both accelerate the iron droplets settling. The vanadium content in the settled iron droplets and the original iron droplets was obtained by chemical analysis. The possible reason for the increased vanadium in the settled iron droplets was discussed by thermodynamic principles.

Corrosion Behavior of BF Slag to SiAlON Bonded Corundum Refractories

The corrosion behavior of BF slag to sialon bonded corundum refractories using reaction nitriding technology at 1500°C was investigated by crucible test method. The results show that the reaction products of slag corrosion are anorthite, magnalium-spinel and glass phases. The corundum grains can react with MgO in the slag to produce magnalium-spinel, accompanying by expansion and liquating stepwise by slag. Erosion mechanism is oxidation-erosion-dissolving. This study is very necessary and useful to improve the property of BF slag resistance and to yield better overall properties of sialon bonded corundum refractories.