Present situation and suggestion of comprehensive utilization of metallurgical slag in China

2.2 Comprehensive utilization

Because the composition and content of all kinds of metallurgical slag are not the same, their comprehensive utilization methods are also different. Because of its good chemical activity, blast furnace slag can be used as high quality raw material in the production of cement or concrete products. The steel dust and mud can be reduced by rotary kiln, rotary bottom furnace and melting furnace at high temperature, and the valuable metals such as iron and zinc can be recovered effectively. The secondary waste residue obtained can be used in the production of cement and other building materials. Steel slag is a kind of industrial solid waste difficult to use in metallurgical slag due to its poor stability and easy grinding, etc. At present, the main utilization methods are iron selection of steel slag, preparation of steel slag micro-powder, road base material, etc., but due to the above reasons, the market still holds a conservative attitude towards its comprehensive utilization products.

The comprehensive utilization of non-ferrous smelting slag after extracting valuable components is more complicated, among which the main uses of copper slag are cement, sand aggregate, casting stone, road base material, etc. After pretreatment, lead and zinc slag is mainly used in pyrometallurgy or glass-ceramics production. After pretreatment, nickel slag is mainly used in the production of fiber, nickel-iron-copper alloy, microcrystalline materials, ceramic heating plate, iron oxide red, mine filling materials; Cobalt slag is mainly used to produce electrode materials; After the harmless treatment of magnesium slag, it is mainly used for the production of carbon composite binder, magnesium slag heating body, ceramic particle, cement and other building materials, or the preparation of desulfurization agent, dephosphorization agent, ceramic filter material and other environmental treatment materials. Lithium slag is mainly used for the preparation of cement, concrete and other building materials, or the production of adsorbents, chemical raw materials, 13X molecular sieve and so on.

The utilization of electrolytic manganese slag mainly involves the recovery of manganese and selenium, the preparation of fertilizer, the production of cement, active powder, the preparation of free bricks, sintered bricks, ceramic bricks, new wall, ceramics, roadbed materials, acid-resistant bricks, glass-ceramics and so on. In 2020, the comprehensive utilization of metallurgical slag is about 506 million tons, and the comprehensive utilization rate is 73.48%.

3, metallurgical slag comprehensive utilization related patents, standards and demonstration projects

3.1 Patents and Standards

The comprehensive utilization of steel slag has always been a difficult point in the comprehensive utilization of bulk industrial solid waste. In recent years, research on the comprehensive utilization of steel slag has gradually increased, and in 2020, 576 patents related to steel slag have been applied for and 299 have been authorized. The related research mainly focuses on the preparation of building materials from steel slag, the pretreatment of steel slag and the recovery of valuable components in steel slag. Among them, the University of Science and Technology Beijing has obtained 11 patents, mainly related to steel slag collaborative preparation of cementing materials, steel slag recycling iron resources and other directions; Wuhan University of Technology has obtained 9 patents, mainly related to the preparation of cement, asphalt mixture and steel slag pretreatment to improve stability and other directions; MCC Building Research Institute Co., Ltd. has obtained 9 patents, the main direction is the pretreatment of steel slag.

There are 54 metallurgical slag related standards, including 18 recommended national standards and 24 industry standards (19 ferrous metallurgy direction, 4 building materials direction, and l transportation direction); There are 12 local standards (3 in Hebei Province, 2 in Jiangxi Province, 1 in Shanxi Province, 1 in Hubei Province, 1 in Liaoning Province, 1 in Henan Province, 1 in Sichuan Province, 1 in Jiangsu Province, and 1 in Shanghai), mainly concentrated in the fields of road base materials, pavement bricks, porous bricks, cement concrete and so on.

3.2 Demonstration Project

In this paper, the comprehensive utilization of iron and steel metallurgical solid waste, such as steel dust and mud, steel slag and blast furnace slag, is illustrated.

(1) Steel dust and mud. Baowu Group Yongsteel, Shaosteel, Zhan Steel and other steel bases, as well as Jiangsu Shagang have built a number of rotary bottom furnaces, using direct reduction process to treat zinc-containing dust and mud in steel plants, to obtain zinc oxide products and DRI pellets, the treatment scale of 20 ~ 30t/a; Wuyang Iron and Steel, Xinlian Environmental Protection and other companies built a number of rotary kilns, used to recover iron and zinc resources from steel dust and mud.

(2) Steel slag. Jiangsu Yongsteel Group Co., Ltd. built a 3D printing construction production line, using steel slag as 3D printing building "ink" raw material to prepare new building materials; Shanxi Jianlong Industrial Co., Ltd. annual output of 600,000 m2 road brick production line, annual consumption of steel slag 320,000 t; Hasco (Tangshan) Metallurgical Materials Technology Co., Ltd. uses steel slag to prepare roadbed concrete, machine-made sand, dry mixed mortar and other materials, and consumes 1.2 million tons of steel slag annually. Taigang Resources Co., Ltd. annual output of 300,000 t new building materials raw material production line; Jintaicheng Environmental Resources Co., LTD. Hc-high-performance concrete cementing material, ultrafine slag powder production line, the annual consumption of steel slag and other solid waste 2 million tons; Shanghai Baosteel Ningbo Ziheng Co., LTD. Annual output of 300,000 t steel slag grinding powder and 600,000 t slag grinding powder production line; Bin Xin Iron and Steel Group 700,000 t/a steel slag has pressure hot quenching treatment and processing and purification production line.