The Refractory is widely used in steel making systems, iron making systems, building materials systems, and steel rolling systems, and the Refractory has learned that in industries such as machinery, fire resistance and waste incineration, the use of Refractory has also achieved good results. High temperature industries such as steel, cement, and glass, as well as various industrial furnaces, consume large amounts of Refractory, which are bound to generate large amounts of waste Refractory. If they are recycled and reused, not only solve the problem of environmental pollution, but also greatly reduce the production cost of enterprises。
Waste Refractory are produced in the main production units of iron and steel enterprises, mainly for the routine repair of industrial kilns and the intermediate repair and overhaul of kilns. About 70 percent of the Refractory's annual consumption goes to the steel industry. As the global steel industry grows, especially in China, where steel production is growing by 20% a year, Refractory consumption is rising. Therefore, how to achieve the recycling of Refractory, steel industry has become an important aspect of achieving a circular economy. At the Second World Refractory in 2004, Refractory recycling was one of the key issues.
The Japanese steel industry has done a great deal of work on how to effectively utilize the waste Refractory, and in recent years the Refractory has been actively promoted in various steel mills. In 2001, for example, the Refractory used 4,100 tons a month, of which 1,003 tons, or 24 percent, would be Refractory, of which 750 tons would be used as paving materials and the rest as resources for reuse. Their main technical points in Refractory recycling are: (1) separate recycling. The type of Refractory used in a kiln varies from site to site. Mixing used Refractory makes Refractory difficult to manage, so they have to be sorted and recycled before they can be reused. Recovery according to magnesium oxide system, alumina system, carbon-containing system, carbon-free system and so on. In addition, mixed with different materials or iron sheet, but also through magnetic separation and other methods, to separate them. The used Refractory must first be broken down to 200 mm ~ 400 mm, and then further broken down into more manageable sizes below 20 mm by impact, compression or shearing in the subsequent crushing process. For the waste Refractory containing iron sheet, the iron content in the Refractory with particle size of 5 ~ 10 mm is reduced to less than 2% by electromagnetic separation method with magnetic strength of 12000 GAUSS or more. After crushing and removing iron powder as a re-use of raw materials, the particle size should be separated management. Classification generally use Metal Mesh screen, Mesh size according to the need to prepare, large Mesh above, small mesh below, for continuous screening. In the process of crushing, grinding and grading, care should be taken not to spread the dust, to seal the device, in the dust collector recovery. The collected dust can also be added to the raw materials for the production of landscape tiles. (2) the production materials of the new Refractory shall be added in an appropriate proportion. As the additive material, the particle size is 5 ~ 20mm or 1 ~ 5mm. With the increase of the proportion of the additive, the amount of water added will also increase, which will increase the porosity and reduce the durability of the product. With this tendency in mind, attention must be paid to the proportion of materials to be reused and where they are used. The particle size is 1 ~ 5mm in wet spraying and less than 1mm in dry spraying. It is difficult to remove iron and impurity completely by reusing material. If more than 20% reusing material is added, the durability will be reduced because of the harmful influence of impurity contained in it. A small amount of SIO2, Cao and other slag components in the waste Refractory will react with Al2O3, MgO and SIC in the new raw materials to form low melting point compounds. Therefore, the amount of recycled materials must be controlled. It can be used as a cascade, where the Refractory is used first as an intermediate Refractory and then as a lower Refractory.