Present Situation and Prospect of Development and Utilization Technology of Steel Slag in Angang Converter

I. Introduction

Converter slag (referred to as slag) is a byproduct of steel. For a long time, steel slag has not been comprehensively exploited and used, and has been piled up for a long time to form a slag mountain. It not only occupies a large amount of land, but also a large amount of dust also pollutes the environment. Making full use of the steel slag resources is not only the internal need to improve the environment and achieve sustainable development, but also the fundamental point of developing a circular economy and building resource-saving enterprises. Over the years, Anshan Iron and Steel has attached great importance to the development and utilization of steel slag, insisted on relying on scientific and technological progress, and strengthened the development and utilization of steel slag, which not only makes the steel slag currently produced online fully utilized, but also achieves zero emissions; and also plans and develops the former slag mountain. Use, the effect is very good. Anshan Iron and Steel development of circular economy and build a resource-saving business practices show that steel slag through the establishment of a sound development system, relying on scientific and technological progress, to achieve metallurgical solid waste turning waste into treasure, of harm into is entirely achievable. According to statistics, between 2000 and 2006, Angang handled a total of more than 90 million tons of metallurgical slag (including slag), a total profit of 200 million yuan, and an additional green area of ​​560,000 m ² , making the former pollution source a beautiful green in Anshan Iron and Steel. landscape. At present, Angang has a 2.4 million t/a steel slag magnetic separation processing line imported from Germany and the most advanced in China; a 600,000 t/a slag powder production line imported from Germany with world-class level and 450,000 t/a cement Production line; annual treatment of steel slag 2.3 million tons, iron slag nearly 1 million tons, water slag 4.8 million tons, output value of more than 300 million yuan. The company's five major categories of more than 20 varieties of metallurgical slag products are sold in 8 provinces and municipalities. At the same time, the company has 117 professional and technical personnel, providing strong talent support for the development and development of new slag products. After years of development, the slag development company has become the “leading” of the national metallurgical slag treatment industry, and all the indicators are at the leading level in the same industry.

Second, the development and utilization trend of steel slag circulation

(1) Steel slag for road slag

Steel slag is a rare and precious resource. The steel slag contains active mineral dicalcium silicate and tricalcium silicate. It has the hydraulic properties of cement (its strength can reach C10-C15) and can be used for road base, base and surface condensation. Form a hard cement stone. The steel slag road has better pavement smoothness, no collapse, good wear resistance, strong freeze-thaw resistance, good road stability, and long-term use can eliminate manual maintenance and better performance than gravel road. Therefore, after grading the steel tailings produced by the existing steel slag magnetic separation production line, the production of road slag is the direction of developing steel tailings. From the current effect of the steel slag of Anshan Iron and Steel Co., Ltd. for the construction of road slag, after the steel slag is treated by the hot suffocation process, the tail slag completely meets the requirements of the national standard road slag for steel construction, and the various indexes of the steel slag mixed for road construction are all better than gravel mixture, can replace gravel, powder coal ash, slag, lime and other active material. At present, Angang can produce three kinds of grading road slag, which are used for the base slag in the road engineering, the steel slag mixture in the base layer and the steel slag sand in the asphalt pavement.

(II) Application of steel slag micropowder

The steel slag micropowder is a product which is characterized by the potential activity of cement clinker after the steel slag is over-fired, and the steel tail slag is deep-processed and ground. At present, the country has formulated steel slag micropowder (GB/T20491-2006) and steel slag cement standard (GB13590-2006). During the “Eleventh Five-Year Plan” period, in order to realize the high added value utilization of steel tailings, steel slag micropowder is a nationally supported project that can apply for the national environmental protection special fund, and its input amount is 1/3 of the project investment amount. The steel slag hot stuffing process of Angang Slag Development Company has realized the stability treatment of steel slag, and it is completely feasible to make steel slag powder. In 2006, the steel tailings samples were airlifted to the ThyssenKrupp Hughes Company in Germany for grinding test. The results show that the steel tailings can be ground into steel slag powder to prepare steel slag double powder or steel slag cement.

(3) Application of ready-mixed mortar

The ready-mixed mortar is a powdery or granular mixture of inorganic cementitious materials, fine aggregates, mineral admixtures and additives, which are mixed in a certain proportion, and is also called dry mixed mortar, dry mortar, dry mortar and the like. Steel tail slag powder with particle size <5mm can be used as inorganic cementing material and fine aggregate in dry mortar.

From lime mortar, cement mortar to dry mortar, China's construction mortar is undergoing a profound transformation, and the result will make China the fastest growing and most applied country in the world. After decades of exploitation of natural sand resources in China, limited resources have been exhausted, prices have risen steadily, and huge market demand has been formed. At the same time, unreasonable exploitation of natural sand has caused serious damage to the environment. Therefore, it is very important to make full use of steel tailings waste.

In the urban construction, the mixing mortar on the construction site has a great impact on the construction site and the surrounding environment. In 2007, the four ministries and the two bureaus jointly issued a notice on the prohibition of on-site mixing of mortar in certain cities. Major cement cities in the country will ban the use of cement mixing mortar at the construction site in batches. Therefore, the application of mildly stirred dry mortar has broad prospects.

Third, research on steel slag treatment development technology

Due to the high content of f-CaO and f-MgO in the steel slag, it can react slowly with water (or water vapor) at normal temperature, and can also react rapidly with water (or water vapor) under certain temperature and pressure conditions; The volume expanded by 97.8% and 148%, respectively. Therefore, the treatment is not good, and the building materials industry will cause local stress on the interior of the building component or the road surface, causing cracking of the structure and even damage of the entire building, so that the utilization of the metallurgical slag is limited. To this end, further research work must be done to improve the performance of steel tailings.

(1) Research and characteristics of hot slag treatment process of steel slag

1. Research on hot suffocation treatment process of steel slag

The research on the hot suffocation treatment process of steel slag found that the self-de-pulverization of molten granulated metallurgical slag under the condition of water vapor can realize the slag pulverization, the slag-iron separation, the f-CaO and the f-MgO hydration. The magnetic material of steel slag is easy to be separated and the performance of steel tail slag is stable, which is the most fundamental problem that should be solved in the process of steel slag treatment.

The technical research plan is to use the technical measures such as multi-point uniform watering, natural scumming and extended aging time to perform hot boring treatment under open air conditions. The specific method is to turn the steel tanks entering the factory into the slag road by hot pouring method, and one slag road is generally divided into 8 areas for circulation operation. After a region is filled with metallurgical slag, it is subjected to multiple continuous watering (7 days), natural hot suffocation, then the shovel is used to descend the slope (the smoldering metallurgical slag is dumped), and finally, the steel slag is aged for 7 days. process.

2, steel slag hot boring treatment characteristics

The steel slag is formed at a temperature of 1600-1700 ° C. The steel slag contains hydraulic mineral dicalcium silicate and tricalcium silicate, and the total amount is above 50%. The steel slag belongs to the over-fired Portland cement clinker.

The hot slag of steel slag is to make the steel slag change from the hot-melt state to the normal temperature, which is a complex physical-chemical process in which the properties of the steel slag itself change. After the steel slag is hot and suffocated, it can eliminate harmful substances in the steel slag and retain the beneficial properties of the steel slag. The concrete performance is as follows: 1) The steel slag can be fully pulverized, and the effective separation of slag-iron can be realized, so that the magnetic substance in the steel slag can be easily separated; 2) the harmful substances f-CaO and f-MgO in the steel slag act in water vapor Dehydration to Ca(OH) ₂ and Mg(OH) ₂ eliminates the expansion factor of the steel slag; 3) The active mineral dicalcium silicate and tricalcium silicate in the steel slag achieve quenching, so that the steel tail slag remains High hydraulic hardness.

(II) Research on magnetic slag magnetic separation process

The existing magnetic separation line of the slag development company is a 2.4 million t/a steel slag magnetic separation processing line imported from Germany in 1988. It is the only steel slag magnetic separation processing line with the most advanced technology and the largest processing capacity in China, and 40% of the steel slag. The magnetic material is returned to the steel plant, and the remaining 60% of the steel slag is best used in the building materials industry. The process is a process in which the steel slag raw material is subjected to three-screen, two-break, and three-magnetic treatment.

After the magnetic slag treatment, the steel slag can be selected from the steel slag: slag steel with a TFe grade >80%, accounting for 10% of the steel slag original slag; grain steel with a particle size of 10-50 mm and a TFe grade of >62%, 10% of the steel slag raw slag; magnetic particle size of 0-10mm, 42% TFe grade, accounting for 20% of the steel slag raw slag, that is, 40% of the iron-containing material is magnetically selected from the steel slag.

Fourth, the key work of the development and utilization of metallurgical slag of Angang

—— Expand production scale and adapt to the needs of Anshan Iron and Steel to expand production capacity. At present, the steel slag treatment technology adopted by the company is a process in which steel slag is hot-sprayed and cooled, and then subjected to magnetic separation processing. The equipment has been in operation for 19 years, and the equipment is aging. There are still 3%-4% of metal iron in the steel slag which is not recovered, and the f-CaO and f-MgO in the tailings are not completely digested, and the utilization rate of steel slag is low. To this end, the existing steel slag hot boring treatment process and steel slag magnetic separation production line must be modified to reduce the content of metallic iron in the steel slag to less than 2%, and f-CaO and f-MgO are completely digested to improve the utilization of steel slag. . On the basis of summarizing the experience of Angang and domestic and international steel slag treatment and resource utilization, the paper has carried out a comprehensive and in-depth feasibility demonstration of the steel slag treatment and resource utilization project of Anshan Iron and Steel Co., Ltd., and proposed a set of steel slag treatment process scheme suitable for the production of Anshan Iron and Steel. The program includes the transformation of 2.4 million t / a steel slag three magnetic separation processing line, the construction of 2 million tons of steel slag hot boring production line and a 300,000 t / a steel slag powder production line, the transformation of metallurgical slag treatment process can fully meet Angang's 16 million The production scale of steel and the need to develop a circular economy.

——Developing internal potential and building a deep processing base for steel materials. At present, with a focus on 2.4 million tons of production lines, the pace of technological transformation and localization of equipment has been accelerated, and the production capacity of equipment has been comprehensively improved. The daily processing capacity of steel slag has reached more than 6,000 tons, and the annual output of slag steel, granular steel and magnetic separation powder has reached 20, 20, 400,000 tons, the annual efficiency can be 660 million yuan, and achieve the goal of 100% processing of new slag and 100% recovery of all steel materials in slag. In the future, we must further increase technological innovation, continuously strengthen process management, improve process standards, streamline operational procedures, implement management responsibilities, and dig deep into equipment production potential, and strive to achieve the goal of providing 1 million tons of steel materials to Angang annually.

——Developing metallurgical slag of the new steel mill of Bayuquan to promote the sustainable development of Anshan Iron and Steel. The new Bayuquan Steel Plant is the new economic growth point for Anshan Iron and Steel in the future and the focus of Anshan Iron and Steel's development of circular economy. According to the practical experience of metallurgical slag treatment for decades, combined with the latest technological achievements in the field of comprehensive development and utilization of metallurgical slag in the world, it is planned to build a hot slag capacity of 850,000 t/a and have a scum capacity of 650,000 t/a converter slag. Slag treatment production line, an annual processing capacity of 850,000 tons of metallurgical slag magnetic separation production line, an annual output of 300,000 tons of steel slag powder production line, a 300,000 t / a granular iron deep processing line, a 100,000 t / a thin slag production line and two A 600,000 t/a slag powder production line.

——Strengthen the management of production of slag steel and create conditions for steel mill production. Firmly establish quality awareness and overall situation awareness, continuously improve process procedures, improve product quality standards, and establish a closed-loop quality management control system throughout the entire production process. Strict inspection of slag steel into the warehouse, discharge, loading and other aspects, strict quality control. Strengthen inter-industry communication and coordination, continuously open the internal market of Anshan Iron and Steel, take effective measures to comprehensively improve the quality of products and loading, and ensure that 300,000 tons of high-quality slag steel is provided to Anshan Iron and Steel annually.

-- Increase the capacity of magnetic separation powder and foster new economic growth points. By optimizing the production process and improving key equipment, the magnetic separation powder yield will be greatly improved, from the previous annual output of 40,000 tons to nearly 400,000 tons, becoming the company's leading product. At the same time, the output of magnetic separation powder will be continuously increased, so that the daily output of magnetic separation powder will reach 2000t. In 2008, we will strive to provide 500,000 tons of magnetic separation powder for the company.

—— Expand the production scale of granulated blast furnace slag powder and build a fine raw material base for building materials industry. At present, the slag powder produced by the vertical grinding water slag is the only way to make the water slag harmless. Since 2006, Angang's slag powder has been widely recognized by domestic and foreign markets, sales volume has reached new highs, and the supply of products is in short supply, far from meeting the needs of users. In the future, we will further increase the sales of slag powder and strive to achieve the sales target of 600,000 tons by 2009.

V. Conclusion

Through the development of science and technology, the development and utilization of Angang Steel Slag has made great progress and the effect is outstanding. In the future, we will further strengthen cooperation with research institutes, increase the utilization of metallurgical slag in Angang, and strive to produce 1 million tons of steel materials for Angang every year to provide 1 million tons of building materials for the market. In this way, it not only solves the problem of metallurgical slag pollution, but also protects the ecological environment, expands the non-steel industry, makes rational use of waste resources, and realizes the goal of developing the Angang slag development company into a fine raw material base for building materials industry and a deep processing base for steel materials. To achieve the due contribution of Angang's goal of developing a circular economy and creating a harmonious Angang.

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