New Process of Pellets-Metallized Sintering Process (PMSP) to Treat Zinc-Bearing Dust from Iron and Steel Company
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inc-bearing dust generated in the iron and steel companies contains many valuable and detrimental elements, such as iron, zinc, and carbon, resulting in huge waste of resources and serious environment pollution. According to the statistic, approximately 4 9 107 tons zinc-bearing dust was generated in Chinese iron and steel industry in 2010, which was estimated as 1.6 9 107 tons Fe, 1.2 9 106 Zn, and 4 9 106 tons C, respectively.[1] In the present research, several techniques have been developed or proposed as the intermediate treatment processes based on the hydro-metallurgical process,[2] carbothermic reduction,[3] iron-reduction distillation process of zinc oxide in the dust,[4] chlorination of heavy metals with PVC,[5] lime addition and magnetic separation,[6] and so on. Carbothermic reduction is an effective way to treat zinc-bearing dust, and the waelz process (Rotary kiln) and RHF (Rotary hearth furnace) process have been applied into production. For waelz process, the zinc-bearing dust was mixed with reductant, and the mixture was charged into rotary kiln at the temperature of 1373 K to 1573 K (1100 °C to 1300 °C). The iron oxide was reduced into metallic iron, while the zinc was vaporized and recovered in the condensation.[7,8] However, the final product containing iron TIEJUN CHUN, Associate Professor, is with the School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243002, P.R. China. DEQING ZHU, Professor, is with the School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, P.R. China. Contact e-mail: springcsu@ 126.com; [email protected] Manuscript submitted September 16, 2014. Article published online November 20, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
should be agglomerated before as the burden for blast furnace. The accretion of rotary kiln is also a problem for waelz process. For RHF process, the zinc-bearing dust was mixed with the reductant for pelletizing, and the pellets were charged into rotary hearth furnace. The pellets were heated at 1623 K (1350 °C) by radiation heat transfer though the furnace wall and exhaust gas.[9,10] However, the productivity is low (about 0.1 to 0.2 t m2 h1) because the bed height is only 20 to 30 mm, and the efficiency of heat transfer is also low. Carbothermic reduction of composite pellet (iron ore concentrate and coal or coke) at oxidizing atmosphere was experimentally studied by Kasai, Misra, and Iguchi.[11–13] The results reported the reduction experiments of composite pellets in a combustion packed bed, and the pre-reduced product was manufactured. Therefore, it is a feasible way to produce pre-reduced product by sintering process with composite pellets containing zincbearing dust and reductant. In this paper, pelletsmetallized sintering process (PMSP) was developed to treat the zinc-bearing dust and manufacture the prereduced sinter product. The zinc-bearing dust was collected from Hangzhou Steelmaking Group, China. The mass contents of Fetotal, SiO2, CaO, Zn, Pb, and C are 46.78, 7.73, 5.72
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