The metallurgical industry produces more than 1 billion tons of various industrial high-temperature wastes every year, and the stock is huge. Most of the waste residue is slag and steel slag produced by steel mills. At present, most of the storage methods for treating slag and steel slag solid waste are naturally stacked. During the stacking process, slag and steel slag are easily weathered into dust, which is alkaline when exposed to water, and the steel slag contains vanadium and titanium, which is easy to cause pollution to the surrounding environment.
Steel slag recycling is both environmentally friendly and economical. The use of slag and steel slag refers to deep processing into a reactive concrete component. A large number of studies have proved that the slag and steel slag can be ground into fine powder with a specific surface area of 400m2/kg～550m2/kg, which can be used as cement mixed material to produce steel slag cement. It can be used as concrete admixture after compounding with ore powder, and even Equally replace part of the cement, reduce the cost of cement, and greatly increase the added value of slag and steel slag products. In addition, the finer the slag and steel slag powder, the easier it is to release Ca(OH)2 during the hydration process, improve its stability, and improve the liquid alkalinity of the concrete system. It can act as a slag micro-powder alkaline activator. , so that the late strength of concrete is significantly improved. At the same time, the iron contained in the steel waste is also easily collected. At present, according to national standards and industry standards, the amount of slag and steel slag in cement is between 20% and 50%. Calculated by a 1 million tons cement grinding station, it is possible to directly mix about 300,000 tons of slag and steel slag powder without calcination, which can reduce 36,000 tons of standard coal, which can reduce carbon dioxide emissions by 100,000 tons.
The technology of slag and steel slag grinding technology mainly includes roller press + ball mill combined grinding, pre-grinding vertical mill + ball mill grinding, vertical grinding and grinding. Among them, the vertical grinding and grinding process is simple, the land occupation is small, the civil construction cost is low, the grinding efficiency is high, and the energy consumption is low, which is an ideal slag and steel slag treatment process.
1.Low comprehensive investment. The equipment integrates the functions of crushing、drying、grinding、powder separating and transportation, featuring simple system and compact layout, with the floor space of about 50% of that of the ball mill system. And it can be arranged outdoors so as to greatly reduce the investment costs.
2.Automatic control system. As the roller dose not contact grinding disc directly and the roller and lining board are made of high-quality materials. Therefore, they enjoy longer service life and less wear.
3.The equipment is provided with an expert automatic control system, realizing free switching between remote and local control to achieve easy operation and save labor coats.
4. High-quality finished products. The grinding roller does not directly contact the grinding disc, so the product contains very little iron and the iron contents due to mechanical wear can be easily removed, so that the whiteness and purity of the product can be effectively guaranteed.
5. High environmental protection standard. The system is wholly sealed and works under negative pressure, free of dust spillover and environmentally friendly, with the emission meeting the national standard.
The steel slag powder after grinding has excellent performance. The slag after grinding reaches the following quality index: specific surface area is 500±50m2/kg; activity index: 7 days activity index is greater than 75%, 28 days activity index is greater than 80%; density is 3150±150kg/m3; free CaO content ≤ 5.0%; metal iron content ≤1.0%; MgO content is 13%; water content ≤2.0%; alkalinity coefficient ≥2.0; fluidity ratio ≥98%.
In cement production, the specific steel slag application is as follows: PC32.5 grade green composite cement can be prepared by adding a large amount of steel slag and slag micron powder 30~40% cement clinker; replacing 20%-50% with steel slag ore powder Ordinary Portland cement can prepare C20～C60 different strength grade concrete with excellent performance; use medium slag-based expansion agent to prepare medium and low-grade mass concrete, its adiabatic ideal temperature rise is controlled below 50°C, and impermeability grade reaches P40. Above, the concrete cracking caused by temperature rise is effectively controlled, and the formation of delayed ettringite in mass concrete can be suppressed; the mineral admixture with high activity and compensating shrinkage function is developed, and its 28-day activity index is greater than 90%, when the dosage reaches more than 20%, it can cause micro-expansion of concrete, and the expansion rate starts to stabilize at 90 days, and the size is 1*10-4～3*10-4.