How to improve the durability of the tunnel kiln refractory kiln wall?

In tunnel kilns, refractory insulation bricks are generally laid on the inner surface of the metal plate of the kiln body or unshaped refractory materials are poured. However, such refractory kiln walls are heavy, the materials are not easy to handle, and the construction takes a long time. In addition, when the heat-insulating ceramic fiber material is pasted on the inner surface of the metal shell, the surface is easily damaged and peeled off when it comes into contact with the flame. In this regard, a foreign kiln company introduced a tunnel kiln wall construction method with high thermal insulation and durability.

The kiln wall construction method is to first lay a ceramic fiber insulation layer on the inner surface of the metal mesh of the kiln shell, and then set up a metal mesh with a ceramic coating. The metal mesh is fixed on the metal shell by bolts through the ceramic fiber insulation layer. The ceramic fibers used are made of silicon and aluminum raw materials melted in an electric furnace and fiberized by high-speed compressed air. The fiber can withstand high temperature of 1000 ℃ ~ 1500 ℃, and has good heat resistance and heat insulation. In addition, the fiber is long, twisted and intertwined, stable under rapid cooling and rapid heating, and has the advantages of light weight, low specific heat, and small heat storage. However, when the surface of the ceramic fiber is exposed to high-speed hot air, some of the fibers are peeled off and lost, and the thermal insulation performance is reduced. Therefore, a ceramic-coated metal mesh is arranged on the exposed surface of the ceramic fiber thermal insulation layer to prevent damage to the ceramic fibers. The metal mesh is made of heat-resistant metals such as carbon steel and stainless steel. In order to prevent the damage caused by the flame passing through and the impact of solid foreign objects, the mesh size should be 5mm~20mm. Metal mesh can use mesh stainless steel expanded mesh. In order to prevent metal oxidation corrosion and improve heat resistance, an effective method is to coat the surface of the metal mesh with a ceramic coating for protective treatment. In order to securely install the metal mesh, the mesh is fixed to the metal casing by bolts through the ceramic fiber insulation layer. The kiln wall lining constructed by this method is mainly composed of a ceramic fiber insulation layer, which is lightweight, has good heat insulation, and is easy to construct; The peeling caused by the flame contact; the third is that the heat resistance of the metal mesh itself is improved due to the coating of ceramic material, thereby improving the durability of the kiln wall.

The materials used in the construction of the kiln wall include the metal plate for the kiln shell, the bolts for right-angle welding on the inner surface of the metal plate, the ceramic fiber thermal insulation material laid on the metal plate surface and the ceramic coated metal mesh arranged on the ceramic fiber layer. The material used is bolted to the housing metal plate. In addition, there are washers, nuts and ceramic shrouds that protect the surface of the bolts. In the example, a carbon steel plate with a thickness of 2.3 mm is used as the metal plate of the kiln shell, and the bolts are made of heat-resistant stainless steel. The bolt pitch is 300mm~400mm. The ceramic fiber insulation layer uses silica-alumina fiber, and its thickness is 39mm in the construction state. The density of the ceramic fiber layer is 0.1g/cm3~0.13g/cm3, which is 1/10 lower than the 1.75g/cm3~1.90g/cm3 of the amorphous refractory. As the thickness of the ceramic fiber insulation layer increases, the surface temperature of the metal plate of the kiln shell decreases. Due to the light weight of the ceramic fiber thermal insulation layer, the overall mass of the refractory thermal insulation wall is reduced, and the construction is also convenient. The ceramic coated metal mesh used is a stainless steel mesh expanded metal mesh with a size of 1.2 mm × 7 mm × 14 mm, which is formed by coating the surface of the plate with a silicon-alumina ceramic coating material. The method of coating the ceramic material is to take 30%~35%, 15%~20%, and the rest is clay, based on the total solids, mixed with 20% water, and then add an appropriate amount of sodium silicate and organic binder, mix. The coating agent is applied to the surface of the mesh steel plate, dried, and baked at 600℃~700℃ to form a ceramic coating with a thickness of 2mm~3mm. It is better for the metal mesh to have holes that can isolate the flame, prevent high-speed heat flow, and protect the internal ceramic fiber insulation layer. The nuts are also preferably made of ceramic-coated metal or ceramic. Also, it is best to use a ceramic shroud to protect the nut.

The refractory kiln wall test constructed by this example shows that when operating at a kiln temperature of 900 ℃ ~ 960 ℃, the temperature of the metal plate of the kiln shell is 80 ℃ ~ 85 ℃, and it is fired for 6 hours a day. After six years of use, the kiln wall is almost not damaged.

It can be seen that the wall of the refractory kiln is lightweight, easy to construct, has good heat insulation, and has significantly improved durability.