The firing temperature of brick and tile flat-top tunnel kilns is below 1200℃, and the highest temperature in the general firing system is around 1100℃. According to the firing system, the kiln is generally divided into three zones: preheating zone, firing zone, and cooling zone. The temperature of each zone is also different, so the requirements for the aluminum content and refractoriness of refractory bricks are also different.
In order to reduce the heat transferred to the outside through the wall, the apparent porosity of refractory materials is also clearly stated as a major indicator. The apparent porosity is an important indicator for evaluating the quality of refractory materials or products. It not only reflects the density of refractory materials, but also characterizes whether its manufacturing process is reasonable. In addition to lightweight refractory products, low-porosity raw materials or products are beneficial to improving product quality, improving the mechanical strength of products, reducing the surface area in contact with slag, and extending service life.
The compressive strength of refractory materials at room temperature is very high, and they will deform when subjected to pressure as the temperature rises. For tunnel kilns, the degree of deformation of refractory materials is required to meet production needs when the firing temperature is the highest, that is, the load softening point of refractory materials must meet design needs.
In order to reduce heat dissipation of the container wall, the inner and outer walls of the kiln wall are built with lightweight insulation materials such as lightweight insulation bricks, mineral wool interlayers, and perlite concrete and other applicable insulation materials. The type and thickness of each layer of each section of a kiln are determined according to the temperature of the section.
Testing indicators of refractory bricks in brick and tile tunnel kilns. Most design and construction units still use the above indicators as the standard for testing whether refractory fire bricks meet the technical requirements for the use of tunnel kilns. At present, the testing indicators of refractories bricks have been modified to various indicators such as compressive strength and load softening point.
At present, the construction of tunnel kilns has basically adopted a flat roof structure. At present, tunnel kilns with suspended ceiling structures are divided into two structures, one is a full cotton structure; the other is a composite structure of suspended ceiling bricks and cotton. Here we mainly explain the basic requirements for suspended ceiling bricks as follows:
Coordination of suspended ceiling refractories bricks: The coordination between suspended ceiling bricks is intricate, and the coordination between edges and corners makes the kiln roof firm and flat and produces a seal, which is more convenient for use as a kiln roof insulation layer. At present, various design units have different types and sorting of suspended ceiling bricks, and the specific brick type should be determined according to the kiln type.
Strength of suspended refractory bricks: The strength requirements of suspended bricks suspended on steel beams are extremely strict. Suspended bricks basically bear the load of all insulation materials on the kiln roof.
Precision requirements for construction between suspended ceiling refractory fire bricks: The suspended ceiling is a key project of the roasting kiln. The quality of the suspended ceiling directly affects the quality of the entire kiln and involves the entire production line. First of all, the suspended ceiling bricks and suspended ceiling panels should be inspected immediately after entering the site, and the suspended ceiling work can be carried out only after passing the inspection. The top can have a micro-arc of 20mm~30mm. The flatness of the top brick plate, the size of the seam between the brick plates, and the top height must be strictly guaranteed. The seam between the brick plates must be filled with high-purity high-aluminum wool, which can ensure the free expansion and contraction of each ceiling plate and ceiling brick, and also avoid the fire head from being strung together during kiln baking. At the same time, it is also necessary to ensure that the thermal expansion of the ceiling bricks in the high-temperature zone has enough space so as not to damage the ceiling structure.
Technical index requirements for ceiling refractory bricks: The aluminum content of ceiling bricks is generally selected as 42% h; N-:1 grade, and the refractoriness is 1760℃. The advantages of flat-top tunnel kilns are large output, easy operation, small preheating zone gas stratification, and stable structure. It has now become the leading product in the market. Flat-top tunnel kilns have more stringent technical requirements for kiln roof refractories bricks. The quality of a tunnel kiln depends on the refractory materials and construction accuracy. The selection of refractories bricks plays a decisive role in the construction quality of brick kilns, and reliable kilns are the guarantee of high-quality finished products. Therefore, the selection of reliable quality refractory fire bricks is the premise of ensuring the life of the kiln and the necessary condition for ensuring the normal production of the entire production line.
