Green Technology‐Based Utilization of Refractory Siderite Ores to Prepare Electric Arc Furnace Burden

Abstract

The rapid development of the steel industry in China has concurrently led to the rapid consumption and depletion of easily processible iron ores. Thus, considerable attention has been focused on the utilization of refractory iron ores to meet the requirements of the steel industry. [1,2] In this context, sideritecontaining FeCO 3 is an important and typical refractory iron resource, [3] with current deposits in China totaling to nearly 1.83 billion tons. However, the average iron grade of Chinese siderite is 33%, and thus, its direct utilization is difficult. Meanwhile, numerous studies have reported that only %10% of siderite ore is reused as siderite utilization is significantly limited by the low iron grade, fine grain size, and complex mineralogy. [4,5] Currently, most iron ores are used to prepare blast furnace burden. In contrast to easily processible iron ores, low-grade iron ores must first be preprocessed to high-grade iron ore concentrates, particularly in the case of low-grade siderite. In this regard, traditional processing methods such as flotation, magnetic, and gravity separation have been adopted to increase the iron grade. [6][7][8] However, siderite exhibits a fine iron grain size, complex mineralogy, and isomorphism, so it is difficult to improve the iron grade of siderite. In addition, the strength of the blast furnace burden made with siderite cannot meet the blast furnace requirement due to FeCO 3 decomposition and subsequent CO 2 liberation during the siderite roasting process. [9,10] Currently, it has been proven that magnetization roasting followed by magnetic separation is effective for treating siderite. [1,11] With this treatment, FeCO 3 can be transformed into Fe 3 O 4 , which is a high-quality concentrate used for preparing blast furnace burden. Nevertheless, coal is the first choice for magnetization roasting; however, this enhances the production cost and causes environmental pollution owing to coal combustion. [1] After magnetization roasting, the concentrate produced by siderite is used to prepare the blast furnace burden via the traditional blast furnace-basic oxygen furnace (BF-BOF) long process. However, the traditional BF-BOF long process, including coking, pelletizing, sintering, blast furnace ironmaking, and BOF steelmaking, consumes abundant coal and coke, leading to the release of large amounts of oxynitride and carbon dioxide. [12,13] According to the literature, [13][14][15] the traditional BF-BOF long process exhausts %80% CO 2 and 84% NO x in the steel industry. In 2016, China's steel industry contributed to 32% of CO 2 and 10% of NO x emissions. [16] Thus, siderite utilization based on traditional BF-BOF long processes causes serious environmental problems.To efficiently utilize siderite, Zhu et al. developed a technique called direct reduction roasting-magnetic separation. [5] With this treatment, FeCO 3 is transformed into Fe, which can be used as electric arc furnace (EAF) burden. This technique avoids coking, pelletizing, sintering, and blast furnace ironmaking p...