What is the knowledge of waste refractory recycling?

1. Removal of waste refractory materials

Refractory materials are used in thermal furnaces and will be removed when they reach a certain service life. In the process of use, the high-temperature substances in the furnace are in contact with the furnace lining for a long time, and they have chemical reactions with the furnace lining and physical effects such as infiltration, diffusion and dissolution, which lead to the deterioration or erosion of the furnace lining, and sometimes the surface of the waste refractory material adheres to the surface of the furnace. The slag of the block even penetrates into the interior of the refractory to form inclusions. In particular, the refractory materials used in different parts of the kiln are different, resulting in different deterioration or erosion of the lining of the kiln. On the other hand, the surrounding environment of the kiln is different. During the dismantling process, the waste refractory material will inevitably adhere to impurities, dust and impurities. Therefore, in the process of dismantling the kiln, it should be dismantled carefully, preferably layer by layer, and the waste refractory materials should be stacked in different categories. During the demolition process, do not mix or stick the surrounding soil and debris into the waste refractory material. Because the refractory material is a high temperature phase, if it is mixed with interlayers, adhesions, dust, impurities, etc. It will lead to a decrease in the high temperature performance of the recycled products of waste refractories, which will affect the use of waste refractories. At present, when many iron and steel enterprises in my country dismantle the kiln, all the waste refractory materials in the kiln are mixed together, which makes it difficult to regenerate high value-added products from the waste refractory materials. 

2. Classification and selection of waste refractory materials

In practice, due to people's management and cognition issues, as well as time and site constraints, some different types of waste refractories are difficult to distinguish immediately from the site. In the process of dismantling the refractory material of the high-temperature kiln, the entire kiln lining is stacked together, which contains a lot of slag, inclusions, dust and soil. In this case, after the waste refractory materials are cleaned from the site and transported to the designated storage yard, they must be sorted and selected by skilled workers with certain identification ability. Different types of refractory materials can be identified and selected according to their appearance, color, density, hardness, strength, size and shape. The distinction between different grades of similar refractory materials should be more detailed. Only by sorting and sorting different types and grades of waste refractories can the added value of recycled products be improved. Therefore, sorting and sorting are very important steps.

3. Treatment method of waste refractory materials

3.1. Removal of soil, dust and impurities in waste refractory materials

For the classified waste refractory materials, if there is dust, mud and other debris on the surface, it must be removed manually. The adulterants are picked out by workers, and water, washing, and dirt and dust are washed off the surface. Through washing and sorting, the harmful substances in the waste refractory such as impurities, adhered soil and dust that affect the performance of the waste refractory can be removed, laying a good foundation for the application of the waste refractory.

3.2. Remove the slag layer and permeable layer of waste refractory materials

Under normal circumstances, the surface of waste refractory material has a layer of corrosive medium in the kiln such as slag, and often the corrosive medium in the kiln also diffuses and penetrates into the interior of the refractory lining, and reacts with the refractory material to form a metamorphic layer. Both the slag layer and the metamorphic layer affect the performance of waste refractories, and affect the high temperature performance and service life of recycled products. Therefore, these harmful components must be removed before crushing. The methods of removal include manual percussion and mechanical cutting. The manual knocking method is to knock the slag layer with a hammer, knock down the slag layer and the permeable layer, and then separate it from the waste refractory material. The mechanical cutting method is to put the waste refractory material with slag and permeable layer on the cutting machine and remove the harmful slag layer. The thickness of the slag layer and the permeable layer adhered to the surface of different waste refractories are different, and the bonding strength is different. When the bond strength is low, manual percussion method can be used, and when the bond strength is high, the harmful slag layer should be removed by mechanical cutting.

3.3. Crushing and crushing

When the waste refractory materials have been removed from various sundries, they also need to be crushed and crushed. Because to be recycled, waste refractory materials must be processed into particles or fine powders of different particle sizes. The processing process is carried out in various crushing and crushing equipment: firstly, the jaw crusher is used for coarse crushing, and then the cone crusher or roller crusher is used for secondary crushing. powder.

3.4. Iron removal of waste refractory materials

Scrap refractory materials contain metal clip iron and iron filings. In the process of crushing and crushing, due to mechanical wear and impact, the iron content in the waste refractory material will also increase. The presence of metallic iron in refractories affects the properties of recycled refractories. When metallic iron is mixed into the refractory product, at high temperature, the metallic iron will undergo an oxidation reaction to form iron oxide. Iron ions will change the valence with the change of the atmosphere in the kiln, and cause volume changes, which seriously affect the volume stability, thermal shock resistance and service life of the recycled products. On the other hand, the presence of iron oxide will cause a low eutectic reaction with the refractory material, which will promote the formation of the liquid phase and the decrease of the liquefaction temperature, resulting in the decline of the high temperature performance and other performance of the recycled product. Therefore, metallic iron must be removed from waste refractory materials. Using the principle that iron has magnetic properties, the waste refractory materials are subjected to magnetic separation treatment. The magnetic separation treatment is carried out in the process of crushing and crushing, which is beneficial to expose and separate the metal iron mixed in the gap of the refractory material and the mechanical iron in the crushing and crushing process, and is easy to remove.

3.5. Homogenization technology

The homogenization of refractory materials is a mature technology, and it is also very suitable to apply it to waste refractory materials. The sources of waste refractories are complex. Even for the same user or even the same kiln, the refractories used in different parts are different. It is quite difficult to sort them out completely. This inhomogeneity will cause the quality of waste refractories to fluctuate greatly, and the quality of waste refractories in different batches and locations may be different, which brings great difficulties to the use or regeneration of high-quality products. To this end, in addition to strengthening classification and sorting, homogenization should also be added. The homogenization treatment method is: put the indistinguishable waste refractory materials in the homogenization yard, and blend them mechanically or artificially to make them evenly distributed, which can ensure the quality of the recycled products produced by using the waste refractory materials as raw materials.

3.6. Separation technology

The waste refractories obtained by crushing and crushing are directly used as raw materials, and high-quality recycled products cannot be prepared: the main reason is that waste refractories are composed of many different materials, and also contain a certain amount of harmful components. Only by removing these harmful components and separating different raw material components can the inherent quality of the raw materials be improved and high-quality recycled products be prepared. Therefore, the broken and crushed waste refractories should be further processed to separate out different after-use refractories. Fire material composition.

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