A New Type of Composite Coke Prepared from Steel Slag and Mixed Coal: Preparation Process and Microstructure

Abstract

Steel slag is a dense and rock-like byproduct of the steel production process. In China, more than 100 million tons of steel slag is produced each year. [1,2] However, only about 30% of the steel slag is utilized availably. [3,4] The main chemical components of steel slag are calcium oxide (CaO), ferrous oxide (FeO), magnesium oxide (MgO), and silicon dioxide (SiO 2 ). Currently, steel slag is widely used in various fields, such as coarse aggregates in roads and pavements and hydraulic engineering, fine aggregates in concrete, and supplementary cementation materials in blended cement. [5][6][7][8] In contrast, global warming has aroused continuous and widespread concern. CO 2 is the main greenhouse gas resulting in global warming, which is harmful to the balance of the natural ecosystem. [9] In 2019, the CO 2 emissions of China, the United States, Europe, and India were 9809.2, 4766.4, 3995.2, and 2309.1 Mt, respectively. [10] The total CO 2 emission of China accounts for more than 28% of the global total CO 2 output, far higher than other countries. [11] Moreover, China's iron and steel industry emits about 16.02% of the CO 2 produced by the global steel industry, which is one of the largest CO 2 emitters of industry. [12][13][14] Thus, how to effectively reduce CO 2 emission for the iron and steel industry has attracted significant interest. [15][16][17] Effective measures should be made to decrease CO 2 emissions for the iron and steel industry. The long process of blast furnacebasic oxygen furnace is the main process of the Chinese steel industry, accounting for more than 90% of China's crude steel production. [18] Blast furnace ironmaking accounts for over 70% of the energy consumption and about 80% of the CO 2 emission of the whole steel production process. [19] Therefore, blast furnace ironmaking is the key to energy saving and emission reduction in the iron and steel industry.To reduce the CO 2 emissions of the iron and steel industry, some low-carbon blast furnace technologies have been put forward or applied in practice. [20][21][22] Under these circumstances, some studies show that applying composite iron coke to blast furnaces could make the thermal reserve temperature drop, strengthen reduction in furnace, improve smelting efficiency, decrease coke ratio, and finally reduce CO 2 emission. [23][24][25][26] With using composite iron coke instead of 30% coke