Recovery Of Potassium Chloride In Iron-containing Dust From Ferreous Metallurgical Process

Iron dust mud, as one of the main source of solid waste from iron and steel metallurgy, mainly refers to the electric arc furnace(EAF) dust(hereinafter referred to as sintering ashes) and blast furnace flue dust. The EAF dust is derived from the flue gas collection of electrostatic precipitator in the sintering process of iron and steel production. Normally, sintering ash consists of complex chemical compositions, except iron, some of which contain harmful elements such as potassium, copper, zinc and lead. Whereas for blast furnace flue dust, it is the coarser dust grain from gravity dust in the process of iron-smelting, and its compositions are also complicated by containing iron, carbon of incompletely combustion and some harmful elements such as potassium, lead, zinc, bismuth, copper, cadmium and arsenic.Based on the physi-chemical properties analysis of EAF dust, blast furnace flue dust and the related researches, a new process for recovering potassium chloride from EAF dust and blast furnace flue, which is composed of water-leaching, purification and decolorization, vacuum evaporation and cooling crystallization, was developed. It can solve the problem of the elements enrichment such as potassium, sodium etc. in the process of sintering dust recycling in iron and steel production, This technology also provides a new way to recovery potassium chloride from iron and steel metallurgical solid waste.The investigation showed that, the content of potassium chloride in the dust from Baotou Iron and Steel Co., Ltd(hereinafter referred to as Baotoul), Hunan Valin Iron and Steel Group Co., Ltd(hereinafter referred to as Xiangtan) and Tangshan Iron and Steel Group Co., Ltd(hereinafter referred to as Tangshan) was 12.09%, 11.90% and 39.58%, respectively. According to the granulometer analysis, the results showed that the median diameter of the dust from Baotou, Xiangtan and Tangshan was 4.21 μm, 23.84 μm, 6.63 μm, respectively. Correspondingly, the specific surface area was 0.20 m2/g, 15.00 m2/g, 0.36 m2/g, respectively.In the research of the recovery of potassium chloride from Baotou sintering dust, the recovering conditions of potassium chloride in potassium-containing solution from water-leaching process were studied. The results showed that, by vaccum evaporation from 120 ℃ of the beginning boiling temperature to 160 ℃ of the ending temperature, with a stirring speed of 50~60 r/min, when the evaporating concentration ratio was at 10.71, the content of potassium chloride in the product was up to 97.24% and the recovery yield of potassium chloride from the dust reached to 65.25%, respectively. This product could meet the first-class index requirements of GB6549-2011, the particle size distribution of the product was well concentrated.Whereas for the recovery of potassium chloride from Xiangtan sintering dust, the results showed that, by vaccum evaporation from 120 ℃ of the beginning boiling temperature to 140 ℃, 150 ℃, 160 ℃ and 170 ℃ of the ending temperature, respectively, with a stirring speed of 50~60 r/min, when the evaporating concentration ratio was at 10.71, the total average content of potassium chloride in the product was up to 95.68% and the total average recovery yield of potassium chloride from the dust reached to 81.87%, respectively. This product could also meet the first-class index requirements of GB6549-2011, the particle size was very uniform.By cooling crystallization of the evaporating concentration solution from Tangshan dust in the thermostatic cooling tank at 0 ℃, 5 ℃ and 10 ℃ respectively, the total average content of potassium chloride was 96.98% and the recovery yield reached to 74.46%, respectively. The product could meet the first-class index requirements of GB6549-2011. It was found by the analysis of laser granulometer and scanning electron microscopy that, the particle size was homogeneous and its distribution was concentrated.