Composite Precast Bricks for Rotary Kiln

Rotary kiln inner lining will be scoured by the hot materials in the kiln and corroded by the dust air, and also need good heat preservation behavior. Through many years' research with great concentration, our company has developed successfully hi-strength compound prefabricated brick. It has hi-strength wearing layer of good corrosion resistance, and light-weight layer of good heat preservation,assuring the increase of heating efficiency in the kiln. In addition, we have unique design in the brick shape and masonry mode, assuring the integral performance of the inner lining. Through the application in many pelletizing plants, various magnetizing roasting rotary kilns for activated grammite, roasting refinery coke,titanium pigment and siderite, the product has gained good effects and its life can reach more than two years, which can enhance the economic effect, save repair cost,and have won affirmation and praises of users.

 

The working layer of composite prefabricated bricks for rotary kilns is made of fused mullite, homogenized bauxite clinker, high-quality silicon carbide, andalusite, high-quality binders and additives. Its thermal conductivity is lower than that of similar products, with high thermal stability, high load softening temperature, high compressive strength at room temperature, stable chemical properties, high high-temperature wear resistance and certain resistance to alkali erosion.

The thermal insulation layer of composite prefabricated bricks for rotary kilns is made of high-quality refractory raw materials and binders, and is made through a special atmosphere sintering process. It has the characteristics of high bonding strength with the working layer, high compressive strength, and low thermal conductivity.

The thermal insulation layer of composite prefabricated bricks for rotary kilns is made of high-aluminum polylight, mullite, and corundum thermal conductive materials, with low density and good thermal insulation effect.

The lining of the rotary kiln is not only subject to the erosion of hot materials in the kiln and the erosion of dust gas, but also requires good thermal insulation performance. After years of dedicated research and development, our company has successfully developed composite prefabricated bricks for rotary kilns. The wear-resistant layer has high strength and good erosion resistance, and the lightweight layer has good thermal insulation effect, which ensures the improvement of thermal efficiency in the kiln. In addition, our unique design in brick type and masonry method guarantees the overall performance of the entire lining. After being used in many pellet plants, active ash, calcined petroleum coke, titanium dioxide and siderite magnetized roasting rotary kilns, it has achieved very good results and a service life of more than 2 years. It has improved economic benefits for users and saved maintenance costs, and has been recognized and praised by users.

At the beginning of this century, rotary kilns were built with single-layer high-alumina or alkaline bricks. Due to their high thermal conductivity, the kiln shell temperature was high (about 300°C), resulting in large heat loss and high energy consumption. Although double-layer or multi-layer masonry such as insulation boards, fiber wool or lightweight insulation bricks can reduce the kiln shell temperature, the rotation of the kiln body will cause the brick body and the insulation layer to be misaligned and loose, resulting in poor integrity, and easy brick drop or even collapse. The use of composite precast bricks for rotary kilns can effectively solve this problem. The heavy layer and the semi-light layer are combined into one, which not only reduces the kiln shell temperature, but also ensures the integrity of the kiln body during rotation. At the same time, it can also reduce the weight of the lining, which is beneficial to the operation of the rotary kiln.

The key to the development of composite precast bricks for rotary kilns lies in the stability and bonding strength of the joint between the heavy layer and the semi-light layer. After testing, it is known that the heavy and semi-light composites should meet the following two conditions:

(1) The materials of the heavy and semi-light matrix materials used for the composite should be similar. It is difficult to obtain good composite strength when two materials with large differences are combined.

(2) The difference in volume density between heavy and semi-light materials cannot be too large. If the volume density difference is large, cracks will occur at the joint due to inconsistent firing shrinkage. After multiple tests, the volume density of the semi-light material combined with mullite alkali-resistant bricks is about 1.8g/cm-3.

1: Design of composite prefabricated bricks for rotary kilns

Large rotary kiln lining bricks are generally built with knife-edge bricks with a length of 200-250mm, and the lining thickness is 230-270mm. The semi-light layer of composite bricks is generally 80mm thick and combined with the heavy layer pot tooth shape.

2: Product manufacturing

Heavy materials and semi-light materials are mixed and ground separately, weighed separately during molding, and partitions are added and positioned when adding materials. After molding using a 630t press, they are dried and fired at 1410℃ for 8h. The product is shown in Figure 4. The performance test results of the semi-light layer of composite bricks are listed in the table below.

Physical and chemical indicators of semi-light layer

3. Heat conduction calculation

The kiln heat transfer calculation is carried out based on the kiln temperature of 1200℃ in the firing zone and the ambient temperature of 30℃. The calculated kiln shell temperature is listed in Table 7. Through calculation, it can be seen that the use of composite bricks can reduce the kiln shell temperature by about 50℃, which greatly reduces the heat loss of the kiln body and reduces energy consumption by more than 5%.

Physical and chemical indicators of composite prefabricated bricks for rotary kiln

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