Study On Reclamation Of Blast Furnace Sludge With Low Zinc

Blast furnace sludge as one of the major solid waste which is produced by iron and steel enterprises contains a certain amount of zinc, lead, bismuth and other heavy metals. Therefore, to develop a new recycling technology is imperative because that it is not suitable to return the blast furnace sludge to the sintering ingredients directly. Based on the research of the characteristics of the blast furnace sludge of the iron and steel enterprise in Hunan, the paper discussed that using pyrometallurgy enrichment method to get the crude zinc oxide and then making use of the wet leaching method to get active zinc oxide.Using of the blast furnace sludge which contains toner and zinc, crude zinc oxide was prepared by pyrometallurgy enrichment method. The effects of temperature and time for zinc volatilization rate in the blast furnace sludge and zinc oxide content during the pyrometallurgy enrichment process were studied. The optimum conditions that the temperature was increased from room temperature to1000℃with a rate of 10℃/min and then remained for 1 h under the protection of nitrogen were obtained. The zinc oxide content and zinc volatilization rate were high to 82.24% and 97%, respectively. In relative to the total iron content of raw blast furnace sludge materials, the total iron content of the blast furnace sludge which was roasted nearly increased by 10%.Wet purify the crude zinc oxide. The effects of temperature, the quantities of ammonia and ammonium bicarbonate, and liquid to solid ratio on the zinc oxide leaching rate in the wet leaching process were also studied. The optimal conditions were temperature 40℃, two times of theory amount of ammonia and ammonium bicarbonate, liquid to solid ratio 4:1 and time 2 h. The zinc oxide leaching rate could be high to 99.9%. Basic zinc carbonate can be precipitated after 90min of ammonia distillation. Aging time was 15 min to make a small part of the basic zinc carbonate particles to fully grow up, so it can save the zinc resources.The technique of DSC/TG was used to study the process of thermal decomposition. In particular, the differential thermal analysis curves were measured at different temperature raising-rate in nitrogen atmosphere for decomposition of the precursor basic zinc carbonate by thermal analysis apparatus. The kinetics process was studied with the method of Kissinger-Akahira-Sunose(KAS). The results show that the active energy of the main step is 146.89 kJ/mol.The precursor basic zinc carbonate, obtained in the wet leaching process, was calcined at 400℃for 30 min to produce active zinc oxide with 98.4% purity and 42.5 specific surface area. The total recovery rate of zinc oxide was high to 95.3%.