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A large amount of iron dust and sludge is produced in the process of iron and steel metallurgy, and its efficient utilization has important economic value and environmental significance. In this study, a method of cold-bonded aggregate is used to co-process stainless steel pickling sludge (SSPS) and gravity dust (GD). The preparation process parameters of cold-bonded pellet are optimized. The role mechanism of the binder on cold-bonded aggregates is studied, and a new type of composite binder, bentonite-plant asphalt (B-PA), is invented. The optimal ratio of bentonite to plant asphalt is determined to be 3:1. The metallurgical performance of B-PA agglomerates is tested, with results showing an RDI+3.15 at 93.6%, a RI at 79.3%, an RSI at 14.2%, a DI at 4.01%, and a thermal cracking temperature reaching 721 °C. The microstructure of the agglomerates after performance testing is characterized using XRD and SEM. This cold-bonding pelletization technology is expected to be widely used in the efficient comprehensive utilization of metallurgical dust in the future, which is of great significance for reducing costs, increasing efficiency, and promoting green environmental protection in the steel industry. [ABSTRACT FROM AUTHOR]

Stainless-steel pickling sludge (SSPS) and blast-furnace gravity dust (BFGD) are solid wastes and hazardous materials produced during iron- and steel-making processes and are important secondary metallurgical resources. The comprehensive use of these two materials shows important environmental significance and economic value. Herein, the elemental content, phase composition, and microstructure of SSPS and BFGD samples were then analyzed. Then, a high-temperature process for SSPS, BFGD, and their mixtures (mass ratio of 1:1) in air and N2 was analyzed by thermogravimetry and differential scanning calorimetry, and the high-temperature calcination products were identified and analyzed using X-ray diffraction. In air, the mixture of SSPS and BFGD can generate SFCA after roasting at 1200 °C. In N2, the carbon in the BFGD reduced the CaSO4 in SSPS to CaS. Based on the high-temperature phase-transformation behavior of the SSPS and BFGD mixture under aerobic and anaerobic conditions, a novel process flow of mixture pelletizing‒sintering agglomeration–blast furnace smelting was proposed for the synergistic treatment of SSPS and BFGD. This process is expected to provide innovation for stainless steel production enterprises to realize the closed circuit recycling of solid waste without leaving the factory. [ABSTRACT FROM AUTHOR]

Stainless-steel pickling sludge (SSPS) and blast-furnace bag dust (BFBD) contain heavy metals such as Ni and Cr, which are harmful to the environment. A new approach of "using waste to treat waste" is proposed, and the process of using a direct reduction method to synergistically desulfurize and extract Zn from SSPS and BFBD to prepare metalized pellets is investigated. The results show that in the reduction roasting, the Fe, Ni, and Cr oxides can be reduced to metals and exist in the form of alloy phases; the metallization rate was 87.9 pct. ZnFe2O4 can also be reduced to Zn(g) at about 1000 °C and recycled in the flue gas, and the Zn extraction rate was 99.81 pct. Moreover, S was removed in the form of SO2 flue gas, and the desulfurization rate was 45.46 pct; the remaining S was present in the form of CaS, which could be removed in the subsequent blast-furnace smelting process, reducing the SO2 flue-gas pressure during the reduction roasting process. CaF2 was relatively stable and mainly exists in the slag phase. The metalized pellets satisfy the requirements for a blast-furnace charge entering the furnace and can realize efficient resource utilization of SSPS and BFBD. [ABSTRACT FROM AUTHOR]