Baosteel's technological progress in ironmaking and future prospects

Ironmaking at Baosteel has focused on blast furnaces over the last 30 years. After passing through the stages of ＂learning＂, ＂tracking＂, ＂usage＂, ＂experimentation＂, ＂innovation＂ and ＂development＂, Baosteel ＇ s production capacity has grown steadily and its standard of technology is increasing. Remarkable progress has been made in the technologies of blending stack, thick layer sintering, low silicon and high anhydroferrite sintering, coal blending, and the high productivity with high pulverized coal injection （PCI） rate and long campaign of the blast furnaces. The entire ironmaking process is developing in the direction of high efficiency, low energy consumption, clean production, and environmental protection because the zero discharge of solid waste and industrial sewage has been achieved. After 20 years of development, Baosteel has become a modernized iron producer with an annual capacity of 28.85 Mt of sinter,7.26 Mt of coke and 22.50 Mt of hot metal （Pugang Corex furnace output included）, and its main economic and technological indices have reached a world-class level.

Practice of flue gas desulfurization application technology in Baosteel No.3 Sinter Plant

With the enhancement of domestic steel production capacity ,iron and steel enterprises have become one major source of SO2 emissions especially in the sintering process. Based on its own characteristics and combined with the experience of desulfurization, Baosteel No. 3 Sinter Plant has independently developed the gas spout-swriling limestonegypsum desulfurization technology, which includes processes, controls and equipments. The theory, process and control of the sintering desulfurization systems are described in this study. Through process monitoring, control and adjustment of operating parameters, the new desulfurization system fit in with the original sintering system. And the quality of the gypsum products is stable, which can be reused as by-product. This method can not only significantly reduce SO2 emissions,but also effectively reduce the cost of desulfurization.

New Application of Stainless Steel

Several rigid substrates such as stainless steel, titanium alloy, aluminum alloy, nickel foil, silicon, and sodium lime glass have been employed for manufacturing high quality TiO2 films by metal organic chemical vapor deposition （MOCVD）. The as-deposited TiO2 films have been characterized with SEM/EDX and XRD. The photocatalytic properties were investigated by decomposition of aqueous orange Ⅱ. UV VIS photospectrometer was employed to check the absorption characteristics and photocatalytic degradation activity. The results show that films synthesized on metal substrates display higher photoactivities than that on absolute substrates such as silicon and glass. It is found that solar light is an alternative to UV-light used for illumination during photodegradation of orange Ⅱ. TiO2 film on stainless steel substrate was regarded as the best one for photocatalysis.

Industrial Experiment on Coke Spraying With ZBS Additive in Blast Furnace

In order to improve the thermal properties of coke, an industrial experiment on the coke spraying with ZBS additive solution was carried out at coking plant and No. 6 blast furnace （2 000 m^3 ） of Kunming Iron and Steel Co Ltd. The coke reaction index （CRI） of the coke spraying with ZBS additive solution decreases by 10. 56 %, and the coke strength after reaction （CSR） increases by 7.80% in comparison with those of the un-sprayed coke. During the experiment, the average iron output increases by 66. 69 t/d, and the coke rate is reduced by 5. 21 kg per ton iron, while the fluctuation of furnace temperture is small, and sulphur content in hot metal and 100% of hot metal are acceptable.

Study on the volatilization kinetics of lead in carbon- containing pellets made of Zn- Pb- bearing dusts

This study investigated the volatilization kinetics of lead in pellets made of Zn-Pb-bearing dusts mixed with coal powder,in a nitrogen atmosphere and in the temperature range between 1 100 ℃ - 1 300℃ ,and showed that the reduction temperature has a significant effect on the volatilization rate of lead and that neither the particle size of the coal powder nor the extra carbon content has any effect on the volatilization rate. The obtained activation energy for the volatilization of lead is 88.74 kJ/mol. The volatilization rate of lead is controlled by both the lead evaporation reaction and the diffusion of gaseous lead through the gas boundary layer covering the surface of the reduced liquid lead.

Reduction behaviors of iron ore lump and pellets with H_2 -CO gas

The differences of reduction behaviors between iron ore lump and pellets were studied by conducting low temperature reduction degradation, static load reduction and droplet tests. These tests simulated the conditions of reduction temperature and hydrogen-containing gas in COREX. Due to its dense structure and low porosity compared with pellets, lump ore possesses poor reduction degradation index （RDI） and slower reduction rate in early and medium reaction stages ,showing signs of lower strength, lower softening and melting temperatures, as well as a wider melting zone and higher AP. That provides some basis to explain the phenomena of differential pressure rise,metallization decline and more sticking after the usage of lump ore in COREX plant.

Numerical Analysis of Blast Furnace Performance Under Charging Iron-Bearing Burdens With High Reducibility

The reducibility of iron-bearing burdens was emphasized for improving the operation efficiency of blast furnace. The blast furnace operation of charging the burdens with high reducibility has been numerically evaluated using a multi-fluid blast furnace model. The effects of reaction rate constants and diffusion coefficients were investigated separately or simultaneously for clarifying the variations of furnace state. According to the model simulation results, in the upper zone, the indirect reduction of the burdens proceeds at a faster rate and the shaft efficiency is enhanced with the improvement under the conditions of interface reaction and intra-particle diffusion. In the lower zone, direct reduction in molten slag is restrained. As a consequence, CO utilization of top gas is enhanced and the ratio of direct reduction is decreased. It is possible to achieve higher energy efficiency of the blast furnace, and this is represented by the improvement in productivity and the decrease in consumption of reducing agent. The use of high-reducibility burdens contributes to a better performance of blast furnace. More efforts are necessary to develop and apply highreducibility sinter and carbon composite agglomerates for practical application at a blast furnace.

Investigation on the relationship between hearth wall erosion and deadman permeability for large blast furnaces

In this study, the relationship between hearth wall erosion and deadman permeability was investigated based on the change in the hearth bottom and hearth sidewall temperatures. Additionally, the operation practice for controlling hearth wall erosion in the large No. 1 blast furnace at Baosteel was also investigated. The reasons for the decrease in the permeability of deadman coke were analyzed, and measures for improving the permeability of deadman coke and controlling hearth wall temperature rising were described. The results show that a decrease in deadman coke permeability is the main reason for refractory temperature increase and hearth wall erosion. This indicates the importance of monitoring changes in hearth working conditions and taking appropriate measures to maintain sufficient permeability of the deadman and balance the hot metal flow and drainage of slag. At this rate, the decline in the hearth bottom temperature and fast rising of the hearth wall temperature can be restrained.

Study on the volatilization kinetics of zinc in carbon-containing pellets made of Zn-bearing dusts

A study was carried out on the volatilization kinetics of Zn in the pellets made of Zn-bearing dusts mixed with coal powder in a nitrogen atmosphere and within the temperature range between 1 100℃and 1 300℃. The study shows that the reduction temperature has a significant effect on the volatilization rate of zinc and that either the coal particle size or the excess carbon content has no effect on the volatilization rate. The obtained activation energy for the volatilization of zinc is 79.42 kJ/mol. The volatilization rate of zinc is controlled by the reaction between the zinc oxides and CO.

Comprehensive longevity technology of Baosteel No.3 BF

Baosteel No. 3 BF has been running smoothly and stably for more than 18 years and has become China＇ s longest-life blast furnace, producing many advanced economical and technical indexes. Comprehensive longevity technology has been developed in terms of the design, operation, and maintenance of the No. 3 BF during the prolonged period of research and practice. To obtain stable and smooth operation and to prolong the campaign life, the following measures have been taken： appropriate designing of the furnace profile and cooling system; improving raw material quality and optimizing the operating system; improving the cooling intensity and water quality;and adopting various longevity maintenance measures to ensure the safety of the body and the hearth temperature.

Environmental-friendly Ramming Materials for Mud Package and Taphole of Large-scaled Blast Furnaces

The compositions, structures and properties of envi- ronmental-friendly ramming materials for mud package and taphole of large-scaled blast furnaces were studied. The results show that the formation of silica fibers makes structure of ramming materials dense. During the process of extruding mud and ramming materials, SiC is partly oxidized ; CaO , F% 03 and carbon penetrate towards the outer wall. The improvement of ramming materials can inhibit the penetration of molten slag, iron and carbon. The bulk density of environmental-friendly ramming ma- terials dried at 200 ℃ is 2.90 g · cm-3, the cold com- pressive strength of this kind of ramming materials dried at 200 ℃ is about 17. 0 MPa and fired at I 450 ℃ is about 39. 2 MPa.

Study on the stability control technology of large-scaled blast furnaces

Nowadays,there are two major trends,which are the increasing blast furnace （BF） working volume and the decreasing fuel resource as well as the decline in its quality,in the ironmaking filed. The two trends lead to the difficulty in the BF operation. The decline of the BF stability requires higher and more elaborate operational techniques. A reasonable and compatible BF comprehensive operating system,as the base of the BF stabilization,is desired to satisfy the demand of large-scaled BF developments. Based on the practical operation of Baosteel No. 3 BF in 2010, the present work analyzes and discusses the basic rules of large-scaled BF stable control techniques,and further optimizes and improves its gas flow control techniques, develops strategies against the decline in fuel quality, which will contribute to the promotion of largescaled BF operational techniques progress.

Level and potential of cleaner production in Baosteel's sintering process

It is necessary for the sintering process to carry out cleaner production, which is also of great significance to the iron and steel enterprises of a long-flow process. According to the cleaner production standard recently issued by China＇ s Ministry of Environmental Protection, the research detailed in this study has analyzed and estimated the level of cleaner production at Baosteel in the aspects of technical equipment, resource and energy utilization, product quality, emissions, recycling and environmental management, etc. The research also expatiated some effective measures with which cleaner production can be carried out in Baosteel＇s sintering process, and discovered some potential opportunities of cleaner production.

Countermeasures for dealing with the change of blast furnace raw materials

Following the dramatic increase of iron and steel output ,iron ore is increasingly in short supply ,and the quality of blast furnace （BF） raw materials is increasingly inferior. All these factors have a strong impact on the BF operation. According to the analysis of the raw material properties at Baosteel and the combination of the BF smelting mechanism and its operational practice, this study probes into the operational countermeasures for dealing with the change of raw materials and puts forward optimized BF control technology to ensure the operation of BFs is stable and smooth.

Practice of improving the hot blast temperature for the 2500 m^3 BF

A high blast temperature is an effective measure that improves pulverized coal injection （PCI）and energy consumption,decreases the cost of blast furnaces （BF）. Apart from using technology such as the increased vault temperature of the hot-blast stove, the increased temperature of the waste gas, the preheating of combustion air and gas, and fully closed mixed air valves, other measures, such as using an oxygen-enriched blast stove, burning high heating value converter gas, increasing the number of stove changes to reduce the time needed for stove blasts, were taken to increase the blast temperature of the 2 500 m3 BF in recent years. The blast temperature of the 2 500 m3 BF was continuously increased in these years. The monthly average temperature of the 2 500 m3 BF reached 1 158℃, with the highest blast temperature reaching 1 195 ℃ in 2006. This technique of increased blast temperatures has reached an advanced level in China.

On-site raw gas cut-off during the shut down of Baosteel phaseⅠcoke ovens

The preparation and implementation of raw coke oven gas cut-off, which was the key process involved with shutting down the Baosteel phase I coke ovens, were investigated, and the main technical points and countermeasures are presented.

The monitoring of burden distribution uniformity and even sintering technology

After expanding the capacity by widening the trolley of the No. 3 sintering machine, severe uneven sintering occurred in the trolley＇ s lateral distribution, which affected the output and quality of sinter. In this study, the quantitative evaluation indices of the burden uniform distribution in the width direction of the sintering machine is introduced for the first time. By measuring the temperature of discharged gas, a plane temperature field is constructed. Through analyzing the temperature field and the burden layer＇ s differential thermal equilibrium, a mathematical model for evaluating the indices, which is an online reflection of the degree of uniform distribution, is built. Following the improvements in burden distribution equipment ,the optimization of the ignition system and the dynamic adjustment of the process ,the problem of uneven sintering in lateral distribution has been solved, and the quality and the yield of sinter have been improved.

Investigation into characteristics of the char bed in the melter gasifier through tuyere probing

Tuyere coke probing was conducted at the Baosteel Corex Plant in order to gain a better understanding of the structure of the char bed in the melter gasifier （ MG ）. After screening, the specimens were observed by an optical microscope to determine the mechanism of the char bed formation. X-ray diffraction （XRD） was used to clarify the degree of graphitization and infer thermal history of coke. The results show that the amount of powder coming from lump coal in the burden is much more than that from coke. Based on this, measures for improving the char bed＇ s permeability are proposed.

Research on the optimization of tundish by water model

Based on the principle of similarity, water was used to simulate the flow of molten steel to analyze the flow field in a tundish. Several schemes of the tundish＇ s tracer shape were designed and corresponding water model experiments were conducted. During the experiments, a computer automatically collected data. The comparison of the residence time distribution（ RTD ） curves drawn according to the computer-collected data optimized the scheme and photographs originated from the experiments with ink as its tracer. It indicates that the water model can optimize the flow field of the tundish.

A novel method for modeling the phase change of iron ore particles in the cohesive zone of a blast furnace

Cohesive zone plays a vital role in the stable operation of a blast furnace(BF),yet the complex phase change process of iron ore particles in this zone is still not well understood.In this study,a novel one-dimensional(1D)unsteady phase change model was developed to elucidate the heat transfer and melting mechanisms of iron ore particles.After model validation,the effects of several key operating parameters(e.g.,particle diameter,gas velocity,initial temperature)on the phase change behavior of iron ore particles were analyzed,and the joint effect of multiple parameters was discussed.The results show that larger-sized iron ore particles possess lower specific surface areas,which in turn reduces their convective heat absorption capacity.Consequently,the distance from the solid-liquid phase interface to the particle surface increases,thereby slowing down the movement of the phase interface and pro-longing the melting duration of the particles.Increasing the gas velocity and the initial temperature does not have a significant impact on reducing the duration of the complete melting process.Under the specified conditions,it is observed that increasing the gas velocity by 3-fold and 9-fold results in a reduction of the melting duration by 2.4%and 8.3%,respectively.Elevating the initial temperature of iron ore particles results in a decrease in the core-to-surface temperature difference,a slower heating rate,and a shorter duration to achieve melting.Among the factors affecting the melting process,the particle diameter is found to be the most significant in terms of the liquid phase precipitation,mushy zone thickness,and core-to-surface temperature difference of iron ore particles.