Vapor pressure measurement of lead and lead chlorides in FeO_T-CaO-SiO_2-Al_2O_3 system

Vapor pressure of lead and lead chlorides from FeOT？CaO？SiO2？Al2O3 slag system was measured by using Knudsen effusion method. The results suggest that the vapor pressures of lead and lead chlorides increase with increasing temperature. For the slag systems without chlorine, the logarithm of vapor pressure （lnp） shows highly linear dependency on the reciprocal of temperature （1/T）, and higher vapor pressure is observed in the condition where more metallic lead vapor is formed. In this case, the vapor pressure of lead increases with increasing slag basicity （w（CaO）/w（SiO2））, increasing FeO content andw（Fe2＋）/w（Fe3＋） ratio. For the case of slag system with chlorine addition, the total pressures of PbCl2 and PbCl increase with decreasing basicity and FeO content of slag.

Vaporization behavior of lead from the FeO-CaO-SiO_2-Al_2O_3 slag system

Vaporization behavior （1163-1463 K） of lead in the slag system of FeO-CaO-SiO2-Al2O3 with CaC% was examined. A thermodynamic estimation with the principle of Gibbs free energy minimization showed that the major vapor species from the sample of the FeO-CaO-SiO2-Al2O3 system＋PbO＋CaCl2 were metallic Pb, PbCl, PbCl2, and FeCl2, at the experimental temperature range. The experimental results show that the mole ratio of vaporized Cl in lead chlorides to vaporized Pb, simply expressed as Cl/Pb decreases with increasing temperature. The larger Cl/Pb means a larger ratio of gaseous PbCl2, since metallic Pb and PbCl vapors are formed in a similar reduction atmosphere. The evaporation is initially rapid and becomes steady after holding for 10 min. Gaseous PbCl2 is mainly formed during the heating period, and at the holding stage, it reacts with FeO to produce gaseous FeCl2 With regard to slag composition, FeO content and basicity significantly affect the evaporation of lead. High FeO content and high basicity promotes the formation of metallic Pb and PbCI, whereas, it prohibits PbCl2 evaporation.

Recent collaborative researches between Japanese universities and steel industry on the iron ore agglomeration process

The properties of iron ores used in ironmaking process have been drastically changed in the past couple of decades.Especially,the change has become significant in the last few years because of the considerable increase in the world steel production.The property change of the iron ore is mainly caused by the depletion of the hard and high-grade lump hematite ores.It has led to the increasing use of ores containing a larger amount of goethite/limonite,i.e.,hydro-oxides of iron.Typically,the proportion of pisolitic ores,which are course limonitic ores,has remarkably increased by several times in Japan.Further,large deposits of the fine goethite ores called Marra Mamba have been developed in Australia and exported to Asian countries.Such trends will be continued in future.Since the change of the ore properties affects not only to the productivity and yield of the sinter but also its metallurgical properties in the blast furnace,further improvement in the sintering technology/ process is required including the preliminary treatment process of raw materials.In order to make wide researches concerning the above issues,the research project 'New Sintering Process through Designing of Composite Granulation & Bed Structure' was formed in the ISIJ,which was the collaborative project between Japanese steel companies and several universities.The project was started in 2005 and carried on the wide range of studies for three and half years.Its main objects are the characterization of pisolitic/goethitic ores and the understanding the behavior during the iron ore sintering process.Further,considering the ore characteristics,some basic researches on the optimum designs of raw material blending,granulation,bed structure,and the metallurgical properties of the produced sinter were performed.The project have invented the technical principle of a new sintering process, namely MEBIOS(Mosaic EmBedding Iron Ore Sintering Process),characterized by the composite granulation and bed-structure,aiming to cope with the drastic shift of the ore properties.Another big issue fallen on the steel industry is the global warming.CO,emission from steelmaking industry occupies about 15%of the total value of the artificial emissions in Japan and therefore its reduction is urgently required.In order examine the possibility to minimize or to reduce further the CO_2 emission from the iron ore sintering process,the research project 'Technological Principle for Low-Carbon Sintering' has been formed since 2009 in the ISIJ.In this project,the analyses of the combustion rates of carbonaceous materials and heat transfer in the sintering bed are first examined by referring the previous studies.Further,experimental works will be conducted on the combustion/oxidation characteristics of biomass charcoal,some organic wastes,steel can scraps,mill scale and partially reduced iron ores as alternative agglomeration reagents of coke and anthracite coal.The effect of their use on the sintering process will be evaluated systematically.It is expected that the structural changes of the sintering bed is considerably different between carbonaceous materials,which disappear during combustion leaving a little amount of ash components and metallic iron bearing materials,which increase the mass and volume during its oxidation. Previous studies showed that the use of metallic iron bearing materials such as steel can scrap and mill scale led to significant decreases in the production rate.This project examines the characteristics of such changes of the sintering bed structure and mineral phases and main process parameters,which govern such phenomena.Further, it searches for a new process principle to overcome the demerits and realize the significant reduction of CO_2 emissions from the iron ore sintering process.In the symposium,summary of activities and the major results and progresses of the above two research projects will be introduced.

Numerical and Experimental Investigation on Heat Propagation Through Composite Sinter Bed With Non-Uniform Voidage:Part Ⅰ Mathematical Model and Its Experimental Verification

The mechanisms of heat transfer through the sinter beds of the MEBIOS process are discussed and their comprehensive mathematical model is proposed. The MEBIOS process, the concept of which has been proposed ear- lier by the authors, allows using both coarse and fine particles of iron ores in the same sinter bed. The study includes two parts. The first part describes the model content and the results of its experimental verification. The model ac- counts for coal combustion, limestone decomposition, moisture evaporation/condensation, and melting/solidifying of solid phases. The model predictions are in good agreement with the experimental data. Typical numerical results of the sintering process and the key parameters influencing the process efficiency are discussed in the second part of the study.

Numerical and Experimental Investigation on Heat PropagationThrough Composite Sinter Bed With Non-Uniform Voidage:Part Ⅱ Prediction of Process Efficiency

The results of numerical simulation of the mosaic embedding iron ore sintering （MEBIOS） process according to the model presented in the first part of the study are introduced. The main objective of the second part is the elucidation of key factors influencing the process efficiency, particularly the sintering completeness, velocity of the heat wave propagation and maximum temperature achievable in the pellet during the wave propagation. Numerical results reveal that the mass fraction of coal, diameter of coal particles and air inlet velocity are of prime importance in determining efficiency of the MEBIOS sintering process.