As the lining of the rotary kiln, it is not only subject to the erosion of hot materials in the kiln and dust gas, but also requires good thermal insulation performance. After years of dedicated research and development, our company has successfully developed high-strength composite prefabricated bricks, which have high wear-resistant layer strength, good erosion resistance, and good thermal insulation effect of the lightweight layer, ensuring 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, lime, petroleum coke, white powder, nickel iron and magnetized roasting furnace rotary kilns, it has achieved very good energy-saving effects 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.
Rotary kilns are mostly built with single-layer high-aluminum or alkaline bricks. Due to their high thermal conductivity, the kiln shell temperature is high (about 300°C), resulting in large heat loss and high energy consumption. Although double-layer or multi-layer masonry forms 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 bricks are prone to falling or even collapse. The use of composite bricks 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.
Products Description
The key to the development of composite bricks lies in the stability and strength of the joint between the heavy layer and the semi-light layer. Through experiments, it is known that the heavy and semi-light composite should meet the following two conditions:
(1) The materials of the heavy and semi-light matrix materials used for compounding should be similar. It is difficult to obtain good composite strength when two materials with large differences are compounded.
(2) The difference in volume density between heavy and semi-light materials should not be too large. A large difference in volume density will cause cracks at the joint due to inconsistent firing shrinkage. After many tests, the volume density of the semi-light material compounded with mullite alkali-resistant bricks is most suitable at around 1.8g/cm3.
1. Composite brick design
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-lightweight layer of composite bricks is generally 80mm thick and combined with the heavy layer pot tooth shape, as shown in the figure below.
2. Product preparation
Heavy materials and semi-light materials are mixed and ground separately, weighed separately during molding, partitions are added and positioned when adding materials, and then molded by a 630t press and dried, fired at 1410℃ for 8h. The performance test results of the semi-light layer of the composite brick are listed in the table below.
Semi-lightweight layer physical and chemical indicators
|
A1203 % |
Bulk density(g•cm-3) |
Normal temperature compressive strength MPa |
Thermal Conductivity (350℃±25℃) [W/(m•k)-1] |
|
53.6 |
1.83 |
35.4 |
0.85 |
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 the table below. 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%.
Kiln shell temperature
|
project |
Bulk density (g•cm-3) |
Thermal conductivity(350℃±25℃) [W/(m•k)-1] |
Lining brick thickness mm |
Kiln shell temperature ℃ |
|
LZ-75 High Alumina Brick |
2.45 |
1.65 |
250 |
293 |
|
Composite brick |
2.30/1.83 |
1.30/0.85 |
170/80 |
238 |
Physical and chemical indicators of composite prefabricated bricks for rotary kiln
|
Item |
High-strength composite prefabricated bricks (wear-resistant layer ) |
|
|
Bulk density(g/cm3) ≥ |
2.50 |
|
|
Al2O3 (%) ≥ |
70 |
|
|
Compressive strength (MPa) |
110℃×24h ≥ |
60 |
|
1100℃×3h ≥ |
80 |
|
|
Flexural strength (MPa) |
110℃×24h ≥ |
8 |
|
1100℃×3h ≥ |
12 |
|
|
Line change rate after burning (%) |
1100℃×3h |
±0.5 |
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