At present, the iron and steel industry has overcapacity. With the country's continuous strengthening of de-capacity, continuous deepening of supply-side reform, and increasing attention to environmental protection effects, energy conservation and consumption reduction have gradually become the key to the survival of iron and steel enterprises. However, the steel industry has a huge demand for refractories, and the annual output of waste refractories has reached 7 million tons. Among them, most of the refractory materials dismantled after use in steel mills are magnesium and carbon. Recycling it not only greatly saves the production cost, but also realizes environmental protection and solid waste recycling. Therefore, the development and utilization of waste MgO-C bricks at home and abroad are increasing.
In view of the problem of waste refractory treatment, foreign countries set up a company specializing in global waste refractory as early as 1980s, while domestic research on waste refractory gradually started after 2000. However, the early research progress was slow and the processing technology was low, which significantly reduced the product performance and resource value of waste refractory, and the use effect was not satisfactory, making it difficult to give full play to the potential utilization value of waste magnesia carbon bricks. The utilization status of waste magnesia-carbon bricks in iron and steel enterprises at home and abroad is as follows.
1.Preparing metallurgical auxiliary materials
As an important way of recycling economy in metallurgical enterprises, the recovery of waste refractory materials and preparation of metallurgical auxiliary materials have developed rapidly. Domestic Baosteel Co., Ltd. cooperated with Henglongxiang Co., Ltd. to make multi-functional magnesium balls by combining waste MgO-C bricks with some additives, which can replace dolomite as slag auxiliary materials in whole or in part, thus creating conditions for steelmaking, slag and slag splashing protection of converter. The analysis results show that the effect of using magnesium ball instead of dolomite is remarkable, and the final slag w (MgO) of furnace is more than 11%, which meets the requirements of smelting process. The slag hanging effect of using magnesium ball in slag splashing process is better than that of using dolomite, and the cost per ton of steel is reduced. After the subsequent improvement of this process, the waste tundish coating was used as the main binder, in which the oxides of K, Al and Na ions were helpful to the slag of fluxing converter. The waste magnesia-carbon brick powder and tundish powder were mixed with 60% and 40% by mass percentage respectively, and the use effect was more remarkable.