Selection Analysis of Refractory Materials for Insulation Cotton Furnace
In recent years, there are more and more domestic insulation cotton production enterprises. However, due to the special composition and production process of thermal insulation cotton products, the refractory materials for the production of thermal insulation cotton kiln are becoming more and more important. At present, the life of China's thermal insulation cotton melting furnace is generally about 3 years, and the kiln age of more than 5 years is not much. The main reason is the choice of refractory materials in various parts of the melting furnace.
The design principle of the refractory material of the thermal insulation cotton furnace is: in a kiln period, the erosion of the refractory materials in various parts of the kiln is basically synchronized. This is the most economical and reasonable.
The refractory configuration analysis of each part is as follows:
(1) The wall of the melting part is generally below 1400 °C due to the low melting temperature, and the viscosity of the glass liquid is large, and the reaction diffusion rate is small, so the erosion on the wall is small. Generally, the 33-oxidation fused zirconia corundum brick is used. Just fine. For the cross-fired furnace, in order to achieve a longer kiln age, the chrome-zirconium corundum brick with a chromium content of 30% is required for the molten pool wall. No matter what kind of refractory material is used, no insulation is carried out near the liquid level line of the pool wall, and air cooling is used to extend the service life of the pool wall.
(2) The chest wall of the melting part of the melting part of the melting part is in the flame space of the melting furnace. Due to the action of the high temperature hot air flow, a large amount of volatiles of alkali and boron adhere to the surface and the gap of the chest wall brick, and chemical reaction with the chest wall brick causes erosion. Therefore, the chest wall brick generally selects a neutral refractory material or an alkaline refractory material having high temperature chemical stability, alkali resistance and boron resistance. For low kiln age chest walls, 33 fused zirconia corundum bricks are the best choice, but for long kiln age chest walls, sintered zircon bricks or chrome zirconium corundum bricks with a chromium content of 30% are better.
(3) The bottom surface of the melting section of the pool bottom tile has a large heat dissipation area at the bottom of the melting section. In addition to strengthening the heat preservation, it is also necessary to consider the erosion caused by the increase of the bottom temperature due to the heat preservation. The fused zirconia corundum brick pavement is the first choice for the bottom of the insulation cotton kiln. For most insulation kiln, the stability of this material is perfectly matched to the life of the furnace. When the glass depth of the melting furnace is less than 500 mm and the bubbling is used, the high temperature of the glass liquid at the bottom of the pool and the strong convection of the glass liquid generated by the bubbling greatly increase the mechanical erosion of the refractory material of the glass bottom by the glass liquid. It is difficult to meet the long kiln age (more than 5 years) by using the traditional fused zirconia corundum brick surfacing layer, so it is more suitable to choose chrome zirconium corundum brick containing 15% chromium.
(4) The melting part is large for the horseshoe flame insulation cotton melting furnace, most of the dome is made of silicon brick. Although alkaline glass is preferably made of alkaline bricks, silica bricks are inexpensive and have poor resistance to alkaline vapors. Due to the high content of boron and alkali in the insulation cotton composition, when the glass glaze on the surface of the brick is lost, the silica brick is easily eroded by the action of boron and alkali vapor, thereby affecting the life of the furnace. At present, the silicon brick dome of the domestic horseshoe flame insulation cotton melting furnace generally produces rat holes after 9 months to 1 year, which requires frequent maintenance, tinkering, and barely support for 3 years. Repairing the dome is both a cumbersome hot work and an impact on production. In order to obtain a kiln age of more than 5 years, the dome material of the thermal insulation cotton melting furnace is not suitable for the use of silica brick, but a chrome zirconium corundum brick containing 30% chromium or a special sintered mullite brick should be used.
(5) The fluid-fluid hole fluid hole is the most easily eroded part of the heat-insulating cotton melting furnace and cannot be repaired in a hot state. Therefore, the service life of the fluid-hole refractory material directly determines the life of the melting furnace. At present, the fluid hole of most insulation cotton melting furnaces uses shrinkage-free fused zirconia corundum bricks without production experience. Since the temperature of the molten glass of the heat insulating cotton melting furnace is low, generally below 1250 ° C, the erosion of the refractory material of the fluid hole is mainly mechanical washing. For small-tonnage thermal insulation cotton furnaces, non-shrinkage fused zirconia corundum bricks can fully meet the requirements of kiln age, but for large-tonnage and long-kiln insulation cotton kiln, the fluid-hole bricks use 50% chromium containing chromium. Zirconium corundum bricks will be more reasonable.
(6) The lattice brick insulation cotton contains high alkali and low boron, and the erosion of the magnesium brick is very severe. Moreover, the alkali vapor and the boron vapor are easily devitrified in the middle temperature region (810 to 940 ° C), and the viscosity of the crystallized material is large, and adheres to the surface of the lattice brick which is uneven after the erosion, thereby causing the blockage of the lattice brick. At present, the lattice brick of the glass wool melting furnace generally adopts alkaline brick, upper layer 97 magnesium brick or 98 magnesium brick, middle layer 95 magnesium brick or 96 magnesium brick, lower magnesia chrome brick and low porosity clay brick. The lattice brick thus arranged has a low cost, but since the alkali vapor and the boron vapor are crystallized and adhered to the checker brick, it is necessary to replace the checker brick for about one and a half years. For long kiln age bricks, cross-shaped fused zirconia corundum bricks are preferred.
(7) Pathway For the upper structure of the flame kiln passage, 33 fused zirconia corundum bricks or sintered zircon bricks are generally used. For the upper structure of the electric melting furnace passage, sintered mullite bricks can be used. The contact with the glass liquid can be 33 fused zirconium corundum brick or chrome zirconium corundum brick containing 30% chromium.
Reasonable refractory matching of insulation cotton kiln is the key to achieving high efficiency. Of course, the choice of refractory materials needs to take into account factors such as kiln age, investment, refractory status and production cycle, so that the operation of the furnace is the most effective and economical.