1. Causes of damage to the refractory castable at the head of the kiln head coal injection pipe
1. Problems with the material and welding quality of heat-resistant steel nails
The working environment temperature of the kiln head coal injection pipe is high, and the surface temperature of the lining can exceed 1500℃. If the heat-resistant steel nails have poor high temperature resistance, they will oxidize quickly and cause the strength to decrease, which will cause the castable to fall off. The stress generated by the expansion of the nails will also destroy the structure of the castable. In addition, if the surface of the nails is not treated with anti-oxidation and anti-expansion, these adverse effects will be aggravated.
2. Inadequate preparation before construction
If the burner surface is not cleaned and rusted before construction, the welding quality of the nails will be affected. During use, the nails will cause the refractory castable to fall off. If the welding is not serious, or the contact area between the nails and the steel structure surface of the burner is too small, the nails will also be welded loose.
3. Unreasonable nail design and construction
If the diameter, size and arrangement of the nails are unreasonable, it will affect the construction quality and use effect of the castable. For example, if the diameter of the nails is too small or the arrangement is too dense, the castable may not be dense during the vibration process, thus affecting its service life.
4. Problems in the construction of refractory castables
- Small pouring space: Construction workers often add more water when mixing materials to improve the fluidity of the castable, but this will increase the porosity in the refractory lining, reduce the compactness, and thus reduce its strength.
- Uncompacted vibration: The lining is thin, the pouring space is small, and the nails are densely distributed between the mold and the burner, making it difficult to operate during vibration. Uncompacted vibration will shorten the service life of the castable.
- Insufficient maintenance: If the lining is not fully maintained after pouring, the early strength of the lining is low, the structure is loose, and it is easy to damage.
- Impact of winter construction: When the ambient temperature is low, the hydration of the binder is incomplete or not hydrated, or the castable body is frozen, which will reduce the strength of the castable or damage its structure.
5. Chemical erosion
Potassium, sodium, sulfur, chlorine and other harmful components from the raw fuel form alkaline sulfates and chlorides at high temperatures, which penetrate into the castables to react chemically and generate expansive minerals, causing the castables to crack and peel off.
6. Wear
The new dry kiln with multi-duct burners has a large amount of secondary air and a high wind speed into the kiln. In addition, the grate cooler is offset from the center line of the kiln, and the secondary air is accompanied by eddy current movement, which causes serious wear on the castables of the coal injection pipe. In particular, the castables at the lower end of the coal injection pipe head are first damaged by the secondary air carrying sand and dust.
7. Thermal shock
When the kiln system is in a continuous and stable working state, the thermal stress destructive effect generated inside refractory castable is very small. However, the rapid cooling caused by the emergency kiln stop will produce a severe thermal shock, which will seriously damage the castables, especially the castables at the lower end of the coal injection pipe head.
8. Other factors
Pile-up and beard-hanging: The high-temperature clinker piled on the upper part of the burner will corrode the castable, forming a "beard-hanging" phenomenon, affecting the combustion of coal powder and the shape of the flame, and will cause damage to the castable during processing.
Problems with the material itself: The castable itself is of poor quality, unscientific proportions, or impurities are mixed in during production, which will lead to rapid damage.
