by With the continuous renewal and progress of cement production technology, a single production line of cement kiln is developing towards large-scale.
The new dry process cement production technology has the characteristics of high kiln temperature, fast kiln speed, complex system structure and serious erosion of volatile components such as alkali, which puts forward more stringent requirements for refractories for cement kiln.
Amorphous refractories have been widely used in cement industry because of their excellent performance, convenient construction and energy saving, accounting for nearly 50%.
However, amorphous refractories have high requirements for on-site construction quality, and it is easy to add too much water on site, resulting in rapid decline of castable performance and burst during baking.
Preform is to shape the amorphous refractory.
The preparation process is between the fixed refractory and the amorphous refractory.
In terms of performance, it has the advantages of both fixed and amorphous.
It is a new direction of the progress of the construction and application technology of amorphous refractory.
It has developed rapidly in recent years.
This paper summarizes the characteristics of refractory prefabricated parts and their application and performance requirements in different parts of cement kiln.
The characteristics and requirements of fire-resistant prefabricated parts are to divide the pre construction parts into small pieces in advance, design the appropriate shape, and then make the mold according to the shape, and then transport it to the site for construction and installation after pouring, forming, curing and baking in the factory.
The application of fire-resistant prefabricated parts changes the on-site pouring construction method of traditional castable, makes the construction simple and easy, saves on-site mixing, pouring or tamping and the corresponding equipment required, greatly saves the construction time, makes the on-site construction conditions not affected by the construction environment and season, and is more conducive to ensuring the construction quality.
In order to facilitate fabrication, transportation and installation, the shape of prefabricated parts shall not be designed too large and complex, and the size shall be unified as much as possible.
In addition, the combination between blocks shall be considered, so as to enhance the integration effect after construction.
The construction part needs to be cleaned, otherwise it will affect the installation accuracy and effect of fire-resistant prefabricated parts.
Most of the parts used for fire-resistant prefabricated parts are in special parts under harsh environments such as high temperature, cement clinker scouring, wear, rapid cooling and heating, which are prone to mechanical deformation.
They need to have good corrosion resistance, good wear resistance, high-temperature gas scouring resistance and excellent thermal shock resistance.
To meet the performance requirements, the ratio of raw materials is the basis, which is similar to the requirements of castables, but castables need to pay attention to the performance in the whole temperature range from construction to service conditions, while fire-resistant prefabricated parts, as finalized products prepared with castables, can pay attention to the performance after baking.
Many manufacturers have listed the performance indexes of prefabricated parts under different temperature conditions, which is actually of little reference significance to cement manufacturers.
In view of this situation, the raw materials and proportion of refractory prefabricated parts can be adjusted on the basis of castable, and more attention needs to be paid to the performance after baking.
Refractory materials in key parts of cement kiln need high construction quality in the construction process.
However, during the maintenance of cement kiln, the construction period is generally short, and the construction quality of on-site pouring is difficult to guarantee.
The quality of construction has a great impact on the service life of refractory materials.
The increase of water content will increase the porosity and reduce the strength of castable, and seriously affect the wear resistance of castable.
After the construction of castable, there must be a certain curing time, and baking treatment must be carried out after the curing, otherwise it is easy to burst.
Because the manufacturing process of refractory prefabricated parts is carried out in the production enterprise, it can overcome the adverse effects of on-site construction time, environmental seasonal temperature changes, on-site construction management and other factors.
After sufficient maintenance and strict baking, it can ensure the construction quality, greatly reduce the quality problems caused by non-standard construction, and give full play to the performance of refractory materials.
Direct ignition after installation can shorten the maintenance time and create good economic benefits.
2.
Performance requirements for prefabricated parts in different parts of the cement kiln 2.1 the low wall and top prefabricated parts of the grate cooler are located in a special position, with complex flue gas composition, high temperature and high wind speed.
The dust in the flue gas is mostly small particles of cement clinker, which is not only large, but also hard, and has serious erosion and erosion of refractory materials.
Therefore, overtemperature or burn through phenomenon is very common in the grate cooler, Therefore, the reasonable selection and construction quality of refractory materials in this part are very important.
The prefabricated parts in this part usually use high alumina and silicon carbide as aggregates, calcium aluminate cement as binder, add ultra-fine powder and admixture, and add a certain amount of heat-resistant steel fiber to make the prefabricated parts with appropriate shape according to the construction specification of low cement castable [3].
The shape, size and structural form of prefabricated parts are related to their use parts.
For the prefabricated parts used for the low wall of the grate cooler, in order to improve the stability of the low wall structure, the upper and lower surfaces of each prefabricated part are respectively provided with grooves or tabs.
Through the combination between tongue and ditch, the sliding between blocks is limited and the integrity and stability of masonry structure are improved.
For the top part of the grate cooler, especially in a high-temperature area, the prefabricated parts can be welded or bolted to the top through anchors, or directly hung on the steel plate.
The construction effect is shown in Figure 1.
The typical performance indexes of the low wall and the top prefabricated parts of the grate cooler are shown in Table 1.
Table 1 performance index of preform for grate cooler Fig.
1 construction effect of preform at the top of grate cooler Fig.
2.2 preform of tertiary air duct bend the lining of tertiary air duct bend of cement kiln not only needs to withstand the scouring of high-speed tertiary air flow filled with a large amount of fine particle clinker, but also needs to withstand serious alkali corrosion under the working temperature of 800 ~ 1200 ℃, resulting in frequent peeling of lining..
