First, the general requirements of high quality refractory castables:
1, the overall characteristics of the requirements
Unshaped refractory castable is the best supplement to the monolithic refractories, in furnace construction, its construction more often than brick complex, but it is more complex in cylinder shape, and often used in extremely harsh environment for the position. Therefore, it should have the following characteristics:
The high temperature strength and wear resistance to high. It depends on the manufacturer of refractory cement and the source of the aggregate.
The water demand is low, the general should not exceed 6.5%. It not only helps to improve the strength of the casting, but also can shorten the curing time;
The size distribution of uniform stability is a prerequisite for stable quality.
Because of the alkaline material preheater system of lining erosion is serious, therefore, requires good alkali resistance.
In different circumstances will have different physical and chemical indicators, in the firing system is higher for the requirements of castable pulverized coal burner and the kiln burner mouth, they must have high temperature resistance and higher wear resistance; for castable in kiln flue use requires a rise in anti scaling performance.
2, the requirements for the preparation of multi-functional pouring material
The ingredients of industrial ceramics, SiC, pure calcium aluminate cement, alumina powder and SiO2 powder. The calcium aluminate cement bonded castables system, the content of SiC is higher, the forming performance variation, but the alkali resistance and anti scaling performance is more excellent, the comprehensive performance of SiC content was three, 30%, 55% of the 15% materials could meet the requirements of refractories for precalcining system.
The dense ceramic industrial structure, low water absorption, good chemical stability, high silicon low aluminum component and alkaline gas reaction of calcium feldspar, potassium feldspar high viscosity liquid, adhered on the surface of casting material, forming glaze protective layer to prevent erosion, alkali, alkali resistance can be enhanced.
The silicon carbide (SiC) material hardness, can meet the raw material resistance to erosion and abrasion, its smooth surface, bonding with other materials and invasive are relatively poor, hard crust. The surface oxide layer will be formed at high temperature to protect the material from the erosion of alkali vapor.
3, silicon carbide (SiC) on the properties of castables as follows:
The SiC itself has the hydrophobicity, not easy to be wet, not easy to form water film, castable increased water consumption. Therefore, the more the content of SiC, the worse the workability and fluidity of the castable, the lower the flexural strength;
Due to the volume density of SiC (2.6~2.8g/cm3) is higher than the density of the ceramics (2.2~2.4g/cm3), the content of SiC increasing, the larger the volume density of materials. When the temperature increases, the content of SiC increases, the volume density will increase. For the change of material line, the SiC content was negative.
The SiC content of material strength of casting, especially in high temperature (1100 DEG C) are favorable. Especially when the SiC particle size is 150 mesh, it can not be completely oxidized, resulting in some cracks around the SiC particles, improving the thermal shock stability and strength of the castable. The non oxidized SiC also plays the role of particle reinforcement.
The SiC content is more, more conducive to the anti scaling performance of materials.
The increasing of SiC content, the more conducive to improve the performance of alkali.
Two, the use of weak points and Countermeasures of refractory castable in precalciner kiln
The precalciner kiln system is a kind of equipment which is operated under high temperature and high dust. The use of harsh conditions should be selected for different refractory castable varieties.
1, the castable kilns and coal injection pipe of short service life.
Before the kiln refractory material existence, peeling off block, alkali erosion performance is poor and other issues, the use of the general cycle is 4~8 months. Therefore, the position of castable refractories should be equipped with adequate fire resistance, mechanical strength, thermal shock resistance and alkali resistance in high temperature environment. It is suggested that using high performance or improved kiln special refractory castable, the product has excellent anti stripping performance, high temperature alkali resistance and anti erosion performance of cement clinker.
Refractory burner material compared to the previous kiln temperature changes more frequently, the temperature difference is bigger, but also by the strong alkaline atmosphere, clinker powder scouring. Castable by one meter in front of the lower part of the burner and prone to cracking, spalling, abrasion and other phenomena, the use of the general cycle is 3~5 months. According to the operating characteristics of the area, with coal material or improved coal injection pipe special refractory castable special casting pipe. The product has excellent spalling resistance and thermal shock stability.
2, the level of the preheater and decomposition furnace cone, feed pipe, the rise of the flue and other parts of the easy crust five.
More content when the harmful components of the original fuel in the kiln system alkali, sulfur and chlorine etc., and the operation is not easy at the time, leading to frequent crust, when using air guns, gun cleaning, not only safe, but also affect the life of castable. It is suggested that high strength silicon carbide castable. Alkali resistance and anti scaling, the product has excellent abrasion resistance.
3, the three wind pipe elbow and air valve parts by the clinker powder wear serious, short service cycle.
Under normal circumstances, the three working conditions of the temperature of the air with a fine powder of clinker at ~950 temperature of 750 degrees C, wind speed above 20m/s. For this part of the refractory lining wear is very serious, short is 2~3 months, a long 6 months or so, not only the refractory lining wear off, and often the steel grinding, the three air valve plate damage. It is suggested that the refractory castable is used.
4, kiln head lower, cooler front top refractory castables for life is short.
The pouring material is impacted by the high temperature clinker from the kiln mouth