Papers by Keyword: Direct Reduction

Abstract: Iron recovery from a lead slag in Henan province was carried out with the technique of coal-based direct reduction followed by magnetic separation. Scanning electron microscopy (SEM) was used to investigate the transformation of iron-containing minerals and the particle size of metallic iron generated by coal reduction. The results showed that technique is feasible for iron recovery from the lead slag. Under the conditions of weight ratio of slag: coal: CaO as 50:15:5, the roasted temperature of 1250 °C for 45 min, and then two stage of grinding and twice magnetic separation, the metallic iron powder was obtained with the iron grade of 92.85% and iron recovery of 92.85%. The iron-containing minerals in the forms of hercynite, fayalite and maghemite were mianly transformed into metallic iron and the particle size of metallic iron was more than 50μm. Therefore, the metallic iron in roasted product can be dissociated by coarse grinding and further was separated by magnetic separation to recover the metallic iron.

Abstract: Coke constitutes the major portion of ironmaking cost and its production causes the severe environmental concerns. So lower energy consumption, lower CO₂ emission and waste recycling are driving the iron and steel industry to develop alternative, or coke-free, ironmaking process. Midrex and HYL Energiron are the leading technologies in shaft furnace direct reduction, and they account for about 76% of worldwide production. They are the most competitive ways to obtain high quality direct reduced iron (DRI) for steelmaking. Therefore, in the present paper, some detailed information about these two processes are given. Much attention has been paid on process scheme, the feedstock, DRI product, heat recovery, reforming gas, hot discharge and transportation, and by-product emission. Its very important for direct reduction development in both natural gas-rich counties and natural gas-poor counties.

Abstract: This paper investigates the impact of additives and cooling way on the metallization rate of reduction product by the experiment of the coal-based direct reduction of vanadium titanomagnetite ; The promotion of direct reduction product metallization by additive species, additive content, reduction time and cooling way was studied and the optimal condition was found; when used 3% CaF₂ as additive reduced for 0.5h and used water quenching to cool down the product, finally got the product which metallization got 93.80% and 42.93% higher than the null sample.

Abstract: Considered the properties of limonite ore at Jiangxi, the raw ore pressing ball - direct reduction - magnetic separation flowsheet have been adopted. the pressing ball conditions, the influence factors and the grinding magnetic separation conditions experiments were carried out. The results shown that: When the dosage of coal was 20%, water was 10%, CMC was 0.5%, pressing ball under the pressure of 190 kN, the calcination temperature was 1100 °C, the roasting time is 50 min, roasted ore were magnetic separated after grinded to 85% through 200 mesh screen. the iron concentrate grade of 92.48% and recovery rate of 93.45% were achieved finally.

Abstract: A mathematical model of complex thermal processes with combustion, radiation and flow in rotary hearth furnace (RHF) for pellet direct reduction is established with CFD commercial software Fluent. Temperature distribution, pressure field and flow field in RHF are simultaneously analyzed by numerical method. It has been found that the temperature distribution in the furnace can meet the need of thermal institution for pellet direct reduction, and great pressure field and flow field can be formed on the basis of reasonable arrangement of burner, nozzle and partition. The simulation results would be helpful for engineering design and parameter optimization of RHF.

Abstract: Through carrying out large scale of experiments, the process of ‘rotary harth furnace direct reduction—deep reduction electric arc furnace—extracting vanadium from vanadium bearing slag—extracting titanium from titanium bearing slag gets through and the recovery of Fe, V and Ti reached 90.77%, 43.82% and 72.65% respectively. With the study on the laboratory experiments and industrial tests, the bottlenecks of this technology such as low metallization rate of vanadium-titanium magnetite in direct reduction process, low reduction rate of vanadium in EAF, vanadium-recovery of hot metal with high silicon content, titanium-recovery of high –Mg &Al slag with titanium, and so on, have been solved. Based on this, the metallization rate of vanadium-titanium magnetite in direct reduction process is more than 90%, reduction rate of vanadium in EAF deep reduction process is more than 80%, vanadium-recovery rate in slag is more than 65%, and titanium-recovery rate in slag is more than 75%. That means good study results have been gotten. Furthermore, low-carbon pig iron with good quality in EAF steelmaking are gotten. Otherwise, V₂O₅ sheet and titanium products can meet the requirements of GB3283-87 and PTA121, respectively.

Abstract: The current development of derect reduction technology for rotary hearth furnace (RHF) is introduced. It is essential to stable and continuous operation of the RHF carrying out the following technologies: the cold-pressing technology，design of the charging machine and discharging machine of the RHF, temperature, pressure and atmosphere in the furnace, and the antioxidation of the metallized pellets. The current develop situation of these technologies are fully discussed.

Abstract: The present paper reviews the situation and technology progress of lead smelting in China. According to the new lead smelting processes, this paper also presents a lead oxygen-enriched flash smelting technology, whose intellectual property rights are completely owned by China，it points out that lead smelting processes develop as follow: lower environmental pollution, higher metal recovery rate, more effective for complex low grade lead-bearing ore materials, lower energy consumption and higher automation degree.

Abstract: In order to recover secondary iron-bearing dust, with converter sludge, mill scale, gravitational ash, casthouse ash as raw materials, high basicity carbon composite pellets are prepared to make iron nuggets through self-reduction at high temperature. The study demonstrates that: The effectively separation of iron and slag, naturally pulverization of the slag phase, and good surface quality of bigger, glosser and brighter iron nuggets can be obtained with reduction temperature 1400 °C,C/O molar ratio 1.1,as well as basicity above 1.8 in this process; The iron phase is not generated well and proportion of small size iron nuggets increases when C/O molar ratio is increased; With C/O molar ratio increases or temperature rises, CO generated increases in direct reduction, which strengthen the reducibility atmosphere in the pellets, beneficial to the processing of desulfuration and dephosphorization; Rising temperature accelerates the generation of molten iron, so that, the fixed carbon contacts with the molten iron longer, which increasing the carbon in iron nuggets. More carbon is provided for the carburizing reaction for the sake of increasing C/O molar ratio, as a result of making more carbon in iron nuggets.

Abstract: For the re-concentration minerals of RE dressing tailings in Bayan Obo mine, Fe and P compounds were selectively reduced by the methods of coal-based direct reduction in reactionary pot. The metal and slag in sponge iron obtained from reduction was melted and separated. Compared to that in re-concentration minerals, the content of valuable elements oxide in melt-separation slag was enriched to about 2.5 times. Therefore, melt-separation slag can be used as the basic material to extract the valuable elements.