Coal Spraying Nozzle Castable
With the upsizing of modern new dry cement production line, the output of cement clinker increases in multiples, the working condition of cement kiln refractory is harsher, the load refractory burdened is more and more large, so only high grade refractory material can promise the normal operation of cement production line. Coal spraying nozzle castable suffers severe high temperature dust containing air washing, and the temperature change is great, meanwhile, alkaline vapor concentration in the air is high. Therefore, coal spraying nozzle castable is easy to spall and strip, the service life of coal spraying nozzle is severely shortened. The service life of current coal nozzle castable is usually 6~8 months, shorter than the big repair period of cement kiln. So, high quality coal spraying nozzle castable is in urgent need.
RS brand coal spraying nozzle adopts corundum, mullite and silicon carbide as aggregate, alumina micro powder and silica micro powder as powder material, pure calcium aluminate cement as binder. Corundum has high bulk density, high rigidity and excellent wear resistance. Mulllite has very low linear expansion rate, good volume stability, so the thermal shock resistance of coal spaying nozzle castable is enhanced. SiC has high Mohs hardness and low linear expansion rate, at high temperature oxidization atmosphere, SiC is oxidized into SiO2 glaze shape protection film, which can resist alkaline gases corrosion, so coal spraying nozzle castable has good alkali corrosion resistance.
Coal Spraying Nozzle Castable Physiochemical Index
| Item |
Corundum mullite SiC castable |
| Al2O3 % |
70~75 |
| SiC % |
12~15 |
| SiO2 % |
6~10 |
| Bulk density g/cm3 |
2.85~2.95(1450℃, 3h) |
| Crushing strength Mpa |
45~65(1450℃, 3h) |
| Modulus of rupture Mpa |
5.5~7.0(1450℃, 3h) |
| Reheating linear change rate % |
+(0.1~0.3) (1450℃, 3h) |
Coal Spraying Nozzle Castable Granularity
The granularity and distribution directly determines the workability and the performance of coal nozzle castable. Coal spraying nozzle castable casted coal nozzle lining is thin, usually between 80~100mm, and anchoring part density is larger, it is not easy to be rammed by vibrator, so max. granule size should not exceed 5mm. As coal spraying nozzle castable should have excellent wear resistance, granularity distribution should comply with closest packing principle.
The Damage Mechanism of Coal Spraying Nozzle Castable
Coal spraying nozzle front end damage. As the front end contact directly with flame, its working temperature is between 1350~1400℃, meanwhile, is constantly suffers high temperature current washing.
Coal spraying nozzle castable through-wall crack. Secondary air enters into kiln through kiln hood, but its temperature fluctuation is huge, so coal nozzle castable temperature changes frequently, thermal stress causes the forming of through-wall crack, or even stripping.
Front end sintering damage. Coal nozzle front end 1m part suffers long term Alkaline gases corrosion, Al, Si and other components react with alkaline gases and produce low melting point eutectics, which leads to over sintering and cracking of front end.
The Casting of Coal Spraying Nozzle Castable
Coal spraying nozzle castable should adopt vertical casting, so the porosity is reduced and the density of the lining is increased. The mechanical strength and service life of coal spraying nozzle is significantly prolonged.
