Recycling of basic oxygen furnace steelmaking dust by in-process separation of zinc from the dust

Abstract

High zinc content in solid wastes from basic oxygen furnace steelmaking offgas cleaning systems is one of the main barriers for source recycling of the solid wastes back into ironmaking and steelmaking process. Over-limit zinc loadings to blast furnaces might damage blast furnace refractory materials, and hence shorten blast furnace campaign life. In addition, high zinc input into blast furnaces might also cause operation difficulties of the blast furnaces, and thus decrease blast furnace productivities. Therefore, how to separate zinc from the solid wastes in an economic way becomes a crucial step for recycling of the solid wastes in sintering–blast furnace ironmaking process. There are three general strategies of separating zinc from the solid wastes, which are referred to as before-process separation, post-process separation and in-process separation. In-process separation is to separate zinc from the solid wastes in the process while the solid wastes are being collected. In this research paper, industrial trials are reported on measuring zinc distributions in dry offgas cleaning systems of two ArcelorMittal basic oxygen furnace steelmaking plants. The results show that primary dusts contain negligible zinc and have good qualities comparable with virgin iron ores. Therefore, in-process separation strategy has a potential to be applied in existing basic oxygen furnace steelmaking offgas cleaning systems to make cleaner offgas byproducts without revamping the offgas cleaning systems. However, in order to recycle more of the solid wastes with low level of zinc, it will be needed to install high-efficiency primary dust collectors and more advanced offgas pre-conditioning mechanisms prior to the primary dust collectors.