In recent years, cement industry in China is growing leaps and bounds. The matured application of large process equipment has provided flying wings for the development of cement industry. In large cement projects, production lines with capacity of 5000t/d even 10000t/d have been often seen. The continuous highly efficient operation of cement enterprises can't do without the escort of wear-resistant ceramic of new high performance for equipment. According to the statistics by authority, the shutdown time caused by wear and abrasion in cement industry occupies 50%-55% of the total shutdown time. The maintenance work quantity caused by wear and abrasion has increased 60%-65% of the total maintenance work quantity of equipment. Wear and abrasion issue of equipment has become one of the critical factors that determine the high efficient operation. The successful solution of this issue has geared up the development of comprehensive competitiveness of cement enterprises.
Figure 1 Production line shutdown due to severe wear
1.Function and characteristic
Figure 2 application of wear-resistant ceramic on conic hopper
Valor series wear-resistant ceramic coating is a kind of new wear-resistant ceramic coating. It can effectively resolve the issues of wear and erosion of equipment caused by dust, material, smoke washing. Owning to its simple and convenient application, as well as applicability for various geometric shape and excellent wear-resistant property, it can ensure continuous and economic operation of the equipment. Therefore shutdown time, maintenance expense and production losses can be greatly reduced.
2.Portions to be applied
Figure 3 shows the typical process of cement industry. Marks are made where valor series wear-resistant ceramic can be applied. For orange portions, low temperature wear-resistant ceramic shall be applied. For red portions, high temperature wear-resistant ceramic shall be applied.
Figure 3 application portions of wear-resistant ceramic on new dry cement production line
Different wear-resistant ceramic can be selected for cement equipment according to different operation temperature. Table 1 shows the operation temperature of typical process equipment and selection of wear-resistant ceramic.
Table 1 operation temperature of typical process equipment and selection of wear-resistant ceramic.
| equipment | media | Work temperature(°C) | wear-resistant ceramic selected |
| Raw mill, cement mill, coal mill | raw material/cement/slag powder/coal powder | Max 120 | Valor400 |
| Coal powder conveying bend | Coal powder | Max 120 | Valor400 |
| Air duct of dust precipitator, exhaust air duct | Smoke/raw material/cement/slag powder | Max 120 | Valor400 |
| Cyclone separator | raw material/cement/slag powder/coal powder | Max 400 | Valor400 |
| Riser/cyclone of Primary preheater riser | Raw material | Max 500 | Valor700 |
| Valve of tertiary pipe | High temperature smoke | Max1200 | Valor1200 |
3. Construction method and curing
According to the variety of abrasive media and washing speed, the application thickness is different. For air ducts, bends and cyclone separator, the construction thickness is 20mm. For severely worn portions such as discharging conic hopper, chutes of powder separator, the thickness shall be increased up to 30mm or 40mm.
In case 20mm construction thickness be applied, weld steel mesh directly on the base plate after oil, paint and rust etc. Have been removed. Usually weld in interlaced mode. The distance between welding points shall be 200~300mm generally. Then apply with trowel the mixture made homogeneously on site by wear-resistant ceramic dry powder, water and steel fibre. As the curing time of wear-resistant ceramic at normal temperature is short, the mixed ceramic shall be used as soon as possible. The valid period for mixed ceramic varies from 30 to 60 min depending on the temperature at site. The residual mixture can't be used after it begins to solidify. In case over 20mm construction thickness be applied,weld spacing steel bar on the base plate of the equipment first. In case 30mm construction thickness be applied, 6mm diameter steel bar shall be used. In case 40mm construction thickness be applied, 8-10mm diameter steel bar shall be used. Then weld steel mesh on steel bars. The mixing and trowelling process are the same as the case of 20mm thickness.
In case of application under high temperature such as tertiary pipe valve, first install refractory casting material on the valve body. The thickness depends on the material of base plate and allowable heat losses. Then weld steel mesh on the refractory casting material and trowel wear-resistant ceramic coating.
The application of directional steel fibre increases the toughness of wear-resistant ceramic coating and enables the ability of resisting deformation. Therefore no matter when it is applied on site-installed equipment or when the equipment has to be lifted upon completing application on equipment, the strength and working life won’t be affected.
After curing for 3 days under normal temperature(20°C), the wear-resistant ceramic can meet strength and hardness requirement and can be put into use. Figure 5 shows the curing time curve at various temperature. Considering the curing time may be influenced by other factors during actual construction, figure 5 is only for reference.
Figure 5 curve for strength and curing time
4.working life
The working life of wear-resistant ceramic relates to the particle size, concentration, washing speed and washing angle of dust and powder. The smaller the particle size and concentration, the lower the washing speed, the narrower the washing angle, the longer the working life of the wear-resistant ceramic. Usually in air pipe of mineral slag micro-powder production line, when the micro-powder to surface area is 420-450m2/kg, concentration is 350g/Nm3,washing speed is 30m/s, washing angle is 30º, the 20mm thick wear-resistant ceramic coating can serve 8-10 years. As the medium in raw material mill and clinker mill has better wearing property, for the same thickness, the working life can be more than 10 years.
