Treatment and comprehensive utilization of steel slag iron slag

Among the metallurgical slags, there are mainly blast furnace water quenching slag, steel slag, blast furnace heavy slag, etc., in which blast furnace water quenching slag and blast furnace heavy slag utilization rate is higher, while steel slag utilization rate is lower, only about 20%. The long-term stacking of unused metallurgical slag is not comprehensively utilized in time. On the one hand, the metallurgical slag will gradually lose its activity and it will be difficult to reuse. On the other hand, the metallurgical slag will occupy a large amount of land and will seriously pollute the environment. How to make heavy use of metallurgical slag has become a top priority for all steel companies.

1.1 Development direction of metallurgical slag resource treatment and comprehensive utilization

The metallurgical slag resource treatment and comprehensive utilization refers to magnetic separation and removal of iron from metallurgical slag and the use of tailings for the production of building materials. The waste steel recovered from the metallurgical slag can be returned to the steel plant for smelting and reuse; the magnetically recovered tailings can be used to produce cement mixed materials, road substrates, masonry cement, ready-mixed mortar, concrete bricks, perforated bricks, Metallurgical slag autoclaved aerated blocks and other building materials.

1.2 Metallurgical slag resource treatment and comprehensive utilization and energy saving and environmental protection

The method of producing energy-saving and environmentally-friendly building materials by using metallurgical slag is to use the renewable resources such as metallurgical slag, blast furnace gas and waste heat steam generated by the steel plant to produce a new process of energy-saving, environmentally-friendly and replaceable high-energy building materials. The steel slag after crushing magnetic separation and iron has more minerals such as free CaO, and these minerals are hydraulic. When steel slag is used together with blast furnace water-quenched slag, Ca(OH)2 precipitated by steel slag can promote alkaline slag, and slag can eliminate the adverse effect of free CaO in steel slag and improve product volume stability. . The heavy slag after crushing magnetic separation and iron removal has the characteristics of good density and good volume stability, and can replace gravel and yellow sand as the coarse and fine aggregate of building materials. In this paper, steel slag mixed materials, steel slag slag concrete bricks and metallurgical slag autoclaved aerated blocks are taken as examples to analyze the relationship between metallurgical slag comprehensive utilization and energy saving and environmental protection.

(1) Energy-saving and environmental protection analysis of steel slag mixed materials

Steel slag has been used in the cement industry for more than 30 years in China. According to incomplete statistics, domestically, 10 million tons of steel slag can be used annually. The steel slag mixture used for the production of cement must be dried. At present, the common drying method is to transport the steel slag mixture containing about 12% of water to the cement plant by car, and then use the combustion of coal to generate hot air for drying. This process increases the amount of car transport by 10% on the one hand and coal resources on the other. Nowadays, the economic way of using steel slag as cement admixture is to use the blast furnace gas, a by-product produced by the ironworks, to dry on the spot, which can greatly save the transportation volume of automobiles and oil, coal and other resources. Using the blast furnace gas produced by the ironworks, the blast furnace gas is dried on site. The first moisture per ton of steel slag is dried to 2% of the final moisture, and 150 cubic meters of blast furnace gas is required (the calorific value is 3500 kcal/m3). Each year, 10 million tons of steel slag mixed materials need 1.5 billion cubic meters of blast furnace gas, equivalent to 750,000 tons of standard coal (the calorific value of standard coal is about 7000 kcal / kg); 10 million tons of steel slag mixed materials per year (the distance is 30 kilometers) It can save 450,000 liters of oil for transportation of automobiles (the heavy-duty trucks consume 1.5 liters/100 kilometers per ton of steel slag oil) and the coal consumption is 750,000 tons.

(2) Energy-saving and environmental protection analysis of steel slag slag concrete brick

Steel slag slag concrete brick is mainly made of steel slag slag masonry cement as cementing material, steel slag, water quenching slag and blast furnace heavy slag as aggregate, and then a certain amount of additives are added, semi-dry pressing and forming, steel mill A metallurgical slag brick produced by the method of residual heat steam curing. It has been proved by theory and practice that the performance indexes of the steel slag slag concrete brick produced by the process are better than the national standard requirements, and the product cost is low. More than 90% of the production raw materials are metallurgical slag discarded by the steel plant, and the steel plant waste heat steam is used for maintenance. In line with national industrial policies for energy conservation and environmental protection. Taking Xinyu Iron and Steel Co., Ltd. as an example of a steel slag slag concrete brick production line with an annual output of 300,000 cubic meters, it can consume about 110,000 tons of steel slag, 110,000 tons of slag and 220,000 tons of heavy slag per year. It can use a large amount of metallurgical slag for steel mills. And produce good economic benefits.

The cementitious material used in the production of steel slag slag concrete bricks is made of metallurgical slag self-contained M22.5 masonry cement, eliminating the need for high-energy PS32.5 or more finished cement. The aggregate of steel slag slag concrete bricks uses the metallurgical slag of the steel plant on site, which can reduce the mining excavation volume and vehicle transportation volume of 360,000 tons of sandstone every year. The maintenance of steel slag slag concrete bricks is maintained by steel mill waste heat steam, which saves coal resources. The production line integrates the comprehensive utilization of metallurgical slag, waste heat steam, blast furnace gas and other renewable resources. It can save sand and stone transportation (with a distance of 30 kilometers) and use 162,000 liters of oil per year (heavy load trucks consume 1.5 per ton of steel slag oil). l / 100 km); can save 90,000 tons of finished cement per year, equivalent to about 10,000 tons of standard coal (110 kg / ton of finished cement); at the same time reduce the production and use of 200 million clay bricks per year, equivalent The standard coal is 30,000 tons (the clay brick coal consumption is 100 kg/m3). If 100 large-scale steel plants nationwide build an annual production line of 300,000 cubic meters of steel slag slag concrete bricks, the annual utilization of metallurgical slag will be about 44 million tons, saving 16.2 million liters of oil for transportation and 4 million tons of coal. In this way, the metallurgical slag discarded by the steel plant is used in large quantities, and the market of clay bricks is replaced a lot, and the cultivated land is protected. At the same time, since the steel slag slag concrete is a burn-free brick, energy saving can be achieved.

(3)Energy-saving and environmental protection analysis of metallurgical slag autoclaved aerated block production

The metallurgical slag autoclaved aerated block is made by adding steel slag and slag to the slurry, adding powdery composite additive, appropriate amount of gypsum and gas generating agent, and adding by gas, pre-culture, cutting, autoclaving and other processes. Gas block products. The metallurgical slag produced by the process has good performance in steam-pressing and aerating blocks, meets the needs of industrial and civil construction, and can consume metallurgical slag in large quantities. More than 90% of the raw materials used in the process are metallurgical slag. The steam is produced by using the blast furnace gas, a by-product of the ironworks, and the product cost is low. The production line consumes about 75 million cubic meters of blast furnace gas per year (heat value is 3200 kcal / cubic meter), equivalent to about 34,000 tons of standard coal (the calorific value of standard coal is 7000 kcal / kg). Taking Xiangtan Iron and Steel Group Co., Ltd. as an example of an annual production of 300,000 cubic meters of metallurgical slag autoclaved aerated block production line, it can consume about 140,000 tons of steel slag and 140,000 tons of slag per year. It can use a large amount of metallurgical slag and produce a good economy. benefit. If 100 large-scale steel mills in the country build an average of 300,000 cubic meters of metallurgical slag autoclaved aerated block production line, they can use about 30 million tons of metallurgical slag, saving 3.4 million tons of coal per year.