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First, the welding of anchors
When constructing the lining of the rotary kiln, the inner wall of the cylinder should be cleaned first, including removing the castables and anchors remaining when the old lining adhered to the inner wall of the cylinder is removed, and the welding is resistant to the case where the inner wall of the cylinder is clean. Anchors made of hot alloy steel (generally 1Cr18Ni9Ti), the shape of the anchors are Y-shaped, V-shaped, etc. The common anchors for the rotary kiln lining are Y-type (see Figure 2). The arrangement and spacing of the anchors depend on The shape of the shell or member, the material and thickness of the liner, the temperature of use and the conditions of use (continuous or intermittent operation), and the magnitude of the thermal and mechanical stresses experienced by the liner. For metal anchors, the minimum spacing of the anchors used for the thin liner is 150 mm, while the maximum spacing of the anchors for the thick liner is 300 mm. If the thickness of the castable is 100mm, the diameter of the anchor is usually 6~12mm. If the thickness is above 200mm, the diameter is generally 10~12mm, and the height of the anchor is 70%~80% of the thickness of the castable. Anchor The spacing between rows is 200mm, and the spacing between rows and rows is 100mm. The calcining zone and the mid-range of the rotary kiln are maintained at a high level for a long time because of the long-term lining temperature, and the cylinder often has a certain degree of mechanical vibration. The anchor should be encrypted and bolded.
The anchors of the rotary kiln are generally arranged in two rows of each row, and the rows and rows are staggered. The metal anchor surface should usually be coated with asphalt, paraffin or wrapped with an electrical plastic tape with a thickness of about 1-2 mm because the metal has a higher coefficient of thermal expansion than the refractory. The welding of anchors should be firm and well-distributed, and the distribution and welding strength should be checked after welding. Then lay the tortoise shell mesh anchor, the height of the tortoise shell anchor should be 2/3 of the thickness of the insulation.
Schematic diagram of lining anchor in rotary kiln
Figure 1 Schematic diagram of the lining anchor in the rotary kiln
The castable is generally stirred by a powerful mixer to form a slurry, and then vibrated by a vibrating rod. The pouring process is divided into four steps of dry mixing, wet mixing, transportation and vibration forming of the castable. In order to fully mix the various grade materials and various additives of the castable material to obtain the maximum bulk specific gravity and the maximum application strength, it is generally required that the dry mixing time is not less than the wet mixing time of not less than 3 minutes, and the wet mixing should be strictly controlled. The amount of water and the amount of water should not be too large, because as the water consumption of the low cement refractory castable increases, the strength decreases and the apparent porosity increases.
After the castable is evenly mixed, it is discharged out of the machine and transported to the construction site by the trolley. Generally, the material is vibrated while feeding, and then vibrates for about 2 minutes after the addition of the material. The surface of the castable is flooded without overflowing and no large amount of bubbles are discharged. The vibration time should not be too long to avoid segregation of each grade material in the castable. It must be noted that the agitated material should be used up within 30 minutes and the material that begins the initial setting is prohibited.
Third, technical strengthening measures in the construction of lining
During the construction, every 600mm in the length direction, an expansion joint with a width of about 3mm and a depth of 4050mm should be opened to accommodate the volume expansion of the surface of the lining during the heating process.
Method of venting the venting hole: Between each of the two expansion joints, a venting hole having a diameter of 4-6 mm is used to pluck the venting holes of 1/2 to 1/3 of the total thickness of the lining body to facilitate the lining. The timely and uniform discharge of deep moisture during the kiln process.
Fourth, the health of the lining
After 24 hours of pouring of the castable, a certain strength has been formed, and the template can be removed for natural health. When the temperature of the refractory castable is not lower than 15 °C, the curing time is 3 days or more, and the heat preservation measures should be taken at low temperature, and natural curing is generally adopted during curing.
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