1. Introduction to the dry-process steel slag recycling technology of Xinxing Hebei Engineering Technology Co., Ltd.
The current domestic steel slag secondary treatment processes include:
1. Traditional dry process Processing technology: At present, the steel slag treatment method used by most domestic steel plants is a simple crushing and magnetic separation process. The equipment used is 1~2 jaw crushers or 1 cone crusher + several belt-type iron removers or 1~2 dry magnetic separators. There are many processes, incomplete separation of slag and iron, and the recycled scrap steel is of low grade (TFe content is about 40%), which is not conducive to steelmaking; the MFe content of the tailings is high (about 6%), resulting in a large waste of resources and poor economic benefits.
The impact of low-grade slag steel on steelmaking production is as follows:
a. Harmful elements such as sulfur and phosphorus in steel slag return to the molten steel and are continuously enriched, affecting the quality of the molten steel;
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b. Due to the large amount of impurities, the amount of slag increases and serious splashing occurs;
c. The inability to accurately determine the weight of the molten metal during the smelting process affects the accurate control of the chemical composition of the molten steel. During pouring, due to insufficient weight of molten steel, it is easy to cause short-length scraps;
d. SiO2, the main component in steel slag, will reduce the alkalinity and change the composition of the slag, which is beneficial to dephosphorization and increasing the service life of the furnace lining. unfavorable.
This process is generally used in small steel plants.
2. Water mill wet separation method: It requires large investment, takes up a lot of land, and the small-grained products are of high grade. It is not suitable for the treatment of large steel slag. The treatment of large slag needs to be coordinated with other rough separation methods, and the tail sludge must be concentrated. , sedimentation, dehydration, and drying processes can be used, which not only pollutes the environment but also increases land occupation and investment, and has poor economic benefits. The fatal disadvantages of this process are:
a. The cost of tailings mud treatment is high. At present, natural sedimentation and mechanical methods are used for tail mud treatment. The natural sedimentation method requires the construction of a large-scale sedimentation tank system, which takes a long time and has poor effects; the mechanical method, represented by Xiangtan Iron and Steel, uses inclined plate settlers and filter presses and supporting pools, pumps, and pipe network systems to process tailings mud. Either way, investment and operating costs are significantly increased.
b. The water content of the dehydrated tailings is also large, and the activity is lost after fine grinding and washing. It can no longer be used for the production of steel slag powder and basically loses its utilization value. And the scrap steel selected after washing is easy to rust. The main component of rust is Fe (OH) 2. Decomposition in the furnace will increase the hydrogen content of the steel and affect the quality of the steel.
c. The tailings mud sedimentation tank system requires a large amount of land, and since the tailings mud has no use value and can only be thrown away, it takes up a lot of land and pollutes the environment.
There are many domestic steel plants that use this process, and the representative steel plant is Xiangtan Iron and Steel Plant.
How to use simple and efficient process equipment to process steel slag and produce high-quality scrap steel, iron concentrate and easy-to-use dry tailings is the key technology to realize the high value-added utilization of steel slag.
In order to overcome the shortcomings of the traditional dry process and water-washed ball mill treatment process, Xinxing Hebei Engineering Technology Co., Ltd. learned from the advanced steel slag treatment processes of Japan and South Korea, digested and absorbed them, and developed a new steel slag treatment process. This process uses a special rod mill for steel slag to crush the steel slag, and achieves complete stripping of the slag and steel through comprehensive control of humidity, particle size, feed volume and other means. The product particle size is relatively uniform, with few over-crushed mineral particles, and the product particle size is about 3mm. Coupled with a variable magnetic field dry magnetic separator with a special structure, all metals are recovered.
All the steel slag products processed by this process are of good quality and can be used in a wide range of ways. The grade of scrap steel obtained is ~90%, which can fully meet the requirements for steelmaking; the grade of iron concentrate obtained is >65%, which can fully meet the requirements for sintering; the magnetic iron content of the obtained tailings is <1%, and it is dry tailings, which can be made into bricks. , production of micro powder, as aggregates, etc., has a wide range of uses and high usable value.
This technology is actually used in Xinjiang Special Steel and Jiyuan Steel Plant, and the recycling effect is good. 2. Design principles for emerging dry-process steel slag recycling technology
1. Adopt mature, reliable and practical advanced process technology, combined with the actual situation of the project and raw material conditions, so that the process configuration is reasonable and smooth, and the technical equipment level reaches Domestic leading and internationally advanced crushing and magnetic separation production lines of the same type.
2. The control system design requires advanced practicality, stability and reliability to ensure that the project is put into production smoothly.
3. Pay attention to the treatment of dust and noise during project production, and adopt reliable and complete environmental protection facilities. The design complies with the safety, health, and environmental protection standards promulgated by the country and the location of the enterprise.
Improve working conditions and increase production efficiency.
4. Adopt energy-saving technology and rationally utilize energy.
5. The design concept embodies the principles of strictness, precision, detail and practicality, optimizes the design, controls the investment scale, and improves the equipment level.
6. During the project implementation process, try not to affect the normal production of existing facilities, and fully consider the maintenance access of the facilities.
7. Implement relevant national, industry and local laws, regulations, standards and regulations, especially environmental protection, energy, safety and health, and fire protection standards and regulations. 3. Technical characteristics of emerging dry-process steel slag recycling technology
1. It is processed separately in three levels of particle size.
2. Use the vibration force of the rod mill to promote the separation of slag and steel.
3. Comprehensive control of three parameters (humidity, particle size, feeding amount) and precise process optimization to ensure complete separation of slag and steel.
4. The scrap steel has high grade, the tailings MFe content is low, and the energy consumption is low. 4. Technical conclusions
1. The "steel slag hot-stewing-dry magnetic separation" treatment technology can realize the mechanization and continuity of the entire steel slag treatment process, minimizing all aspects of the operation after it is put into operation. Therefore, using this solution for steel slag treatment can maximize its economic benefits.
2. After the steel slag is processed by the emerging dry steel slag crushing and magnetic separation process, the slag and steel are completely separated, and the scrap steel products obtained are of high grade, which can well meet the requirements of steel plants. It avoids the effects of low-grade steel slag on the steelmaking plant such as enrichment of harmful elements such as sulfur and phosphorus, large amounts of slag splashing, and casting defects caused by inaccurate weighing.
3. The metal iron content in the tailings of steel slag processed through the emerging dry steel slag crushing and magnetic separation process is less than 1.5%, which maximizes the recovery of steel materials, saves resources, and avoids waste.