Current Situation of Comprehensive Reuse of Metallurgical Solid Waste

Metallurgical solid waste can be divided into slag, ferroalloy slag, steel slag, non-ferrous metal metallurgical slag and dust sludge, red mud, etc.

1) Slag: In the process of iron making, iron oxide is reduced to metallic iron at high temperature, and impurities such as silica and alumina in iron ore react with lime to form silicate and aluminosilicate as the main components of the melt. Slag is a solid waste with the largest discharge in the iron and steel metallurgical industry, and its discharge is directly related to the grade of the ore into the furnace and the smelting system.

2) Steel slag: Steel slag is discharged from converters, electric furnaces and refining furnaces during the smelting process. The slag formed by impurities in metal raw materials, fluxes and furnace linings is mainly composed of silicate and ferrite.

3) Dust sludge: formed with the gas flow or the flue gas discharged from the smelting equipment after oxidation. Generally, the content of iron or metal elements is high. It can be divided into converter sludge, blast furnace gas ash, iron-making dust dust, gas dust dust, etc. .

4) Red mud: Red mud is an industrial solid waste discharged from the aluminum industry during the extraction of alumina. Because of the large amount of iron oxide, the appearance is similar to that of red mud. About 1.0 to 1.8 tons of red mud are discharged for every 1 ton of alumina produced. .

The impact of metallurgical solid waste on the environment is mainly reflected in the following aspects:

1) Land occupation: Metallurgical solid waste such as steel slag is harder than granite. Except for backfilling foundations for a small number of projects, most of them are abandoned around, and even a large number of fertile fields are occupied.

2) Polluted soil and water bodies: If the metallurgical solid waste is not landfilled with proper anti-seepage measures, after weathering, rain and snow melting, and erosion by surface runoff, the harmful components in it are likely to generate high temperature and toxic liquids and penetrate into the soil, killing them. It destroys the microorganisms in the soil, destroys the ecosystem formed by the microorganisms and the surrounding environment, and even causes the plants to die; if the harmful components seep into the water body, it may further harm human health.

3) Dust hazard: The fine-grained waste slag in dust sludge and blast furnace slag will drift with the wind and spread to a distance under the strong wind; harmful gas and dust will be generated during transportation, causing air pollution.

Comprehensive reuse

NO.1 Metal recycling
Metallurgical solid waste contains a variety of other metals, often gold, silver, cobalt, antimony, palladium, platinum, etc. can be extracted, some of which can reach or even exceed the grade of industrial deposits, and the value of some recovered rare precious metals even exceeds the main metal the value of. For example, copper slag is collected in the recovery room, oxidized and sintered, and then processed by reduction method to recover copper particles; red mud contains 10%-45% iron, and a large amount of iron can be recovered to obtain high-grade iron-making concentrates It can also extract aluminum, titanium, vanadium, chromium, manganese and various rare earth elements and trace radioactive elements; coal fly ash and coal gangue contain iron, molybdenum, germanium, vanadium, uranium, aluminum and other metals, which are also valuable for recycling Wait.

NO.2 Utilization of building materials
The building materials industry plays a very important role in the disposal of metallurgical solid waste. On the one hand, steel slag stimulates activity by grinding and can replace cement in concrete construction projects, which can reduce cracks caused by concrete hydration heat and improve concrete’s later strength and wear resistance, frost resistance and corrosion resistance. This kind of steel slag cement is a On the other hand, the application technology of slag as a cement admixture and concrete admixture is very mature and widely used, and it is also an important comprehensive utilization direction; also, the physical composition of red mud is similar to clay, so Red mud is a good substitute for clay. Using red mud as the main raw material can produce a variety of bricks, such as steam-free bricks, fly ash bricks, decorative bricks, ceramic glazed bricks, etc. As the technology becomes more and more mature, the metallurgical solid waste has also stepped out of the embarrassment of “useless”, and has entered a new journey of “full of treasures”.

NO.3 Road engineering
The mixed slag formed by the crushing of slag is an excellent material for building road base and cushion, and has the characteristics of good flatness, water storage and temperature insulation.

NO.4 ceramic industry
The use of metallurgical slag to prepare ceramics is a high-value resource utilization approach. The inert components, heavy metals, free calcium oxide or alkali metals in the metallurgical slag can be converted into beneficial components in the ceramics, so that the ceramics have excellent mechanical properties, wear resistance, corrosion resistance, and heavy metal consolidation. At present, my country has the technical strength to use industrial solid waste to prepare ceramic materials, and this technology has obvious advantages.

NO.5 Environmental protection industry
Studies have shown that steel slag has chemical precipitation and adsorption. In the study of steel slag treatment wastewater, the removal rate of chromium is 99%, the removal rate of zinc is more than 98%, the removal rate of mercury is 90.6%, etc. Its physicochemical properties are considered to be a good mixture of adsorbents and coagulants, and are widely used in the research and treatment of water pollutants such as heavy metal ions, organic compounds, and acid gases such as NOx, SOx, and H2S.

China has carried out a lot of work on the comprehensive utilization of metallurgical solid waste and achieved many achievements, but the realization of comprehensive utilization of metallurgical solid waste is not limited to the above industries. The treatment and utilization of metallurgical solid waste involves many interdisciplinary fields, and more experts and enterprises in more fields are required to participate in it.