The reasons that affect the performance of the castable and the construction and maintenance of the kiln mouth castable

The position of the cement rotary kiln mouth is subject to factors such as clinker abrasion and high temperature harmful gas corrosion for a long time, and the use conditions are very harsh. Therefore, the materials used in this part are required to have good thermal shock resistance, wear resistance and erosion resistance; Kiln mouth guard iron is used at the kiln mouth. In order to facilitate the construction of the kiln mouth, castables are generally used at the kiln mouth.

Castable is one of the commonly used unshaped products in refractory materials. Due to the different properties of the castable, we need to pay attention to the method of use during the construction process. The incorrect use method will affect the performance and service life of the castable.

1. Brief introduction of affecting the performance of kiln mouth castables

1.1 Gradation of castable particle size

Generally, the castable is composed of specific material according to a certain proportion of particles and powder. In the mixing process of the castable, the shape of the particles and the amount of powder added have a great impact on the mixing performance of the castable. If there is more aggregate, it is easy to cause pitting on the cast surface, and the powder has more bones after vibration. The sinking of the material will easily cause the aggregate to sink and the surface will be powdered and lose strength, and it will also affect the flow properties of the castable.

In the process of producing bypass injection materials, we must pay attention to the problem of particle gradation, sample burning materials, and do particle size analysis of burning materials.

1.2 The fluidity of the castable

The more fluid castable is, the easier it is to fill the model and flatten the surface, and the easier it is to obtain a construction body with a uniform structure, which is convenient for construction. Factors affecting the flow value of the kiln-mouth castable include: particle gradation, the nature and amount of dispersant, and the amount of water added. Among them, particle gradation and dispersant are the main influencing factors.

After configuring a reasonable particle gradation, pay attention to the performance and amount of dispersant. Our company's kiln mouth castable generally uses sodium tripolyphosphate.

1.3 Condensation of castable

The kiln mouth castables produced by our company use cement and micro-powder as binders to promote the coagulation of the castables. If the setting is too fast or too slow, it is not good for construction. Too fast coagulation will lose fluidity during use after mixing, and the material will coagulate, making the castable unusable; too slow coagulation will not be conducive to demoulding and affect the construction progress.

2. Construction of kiln mouth castable

At present, the construction of kiln mouth castables is generally divided into the removal of old castables-welding anchors-supporting mold-casting and demoulding. In the construction process of the kiln mouth castable, the general demolition work takes up a large proportion of time and is time-consuming and labor-intensive.

2.1 Demolition

It is difficult to dismantle the castable of the cement rotary kiln mouth, and the material is selected with good material and high sintering strength, so it is difficult to dismantle. Under normal circumstances, there are two ways to remove the excavator hammer removal and manual pneumatic pick removal. If a large number of kiln bricks need to be built during construction, they are demolished using excavator hammers. If only the castable at the kiln mouth needs to be dismantled, the cost and schedule should be considered comprehensively, and an excavator or manual method should be selected for dismantling.

After dismantling, check the surface deformation and oxidation of the kiln shell, and check whether there is any loosening or burning of the kiln mouth guard iron. If there is a problem, it needs to be reported to the owner in time and dealt with accordingly.

2.2 Welding anchors

The castable is combined with the cylinder by the welding of anchors. Due to the effect of high temperature, we generally choose heat-resistant steel as the raw material of the anchors, and generally use Cr25Ni20 heat-resistant steel as the raw material of the anchors for the honey mouth.

Kiln mouth anchors are generally divided into three sizes and models. Taking 5000t rotary kiln as an example, Y-200 anchors are welded on the cylinder, Y-150 anchors are welded on the kiln mouth guard iron, and the kiln mouth end is welded with V -100 anchors. According to the construction requirements, the anchors shall be welded firmly according to the required spacing of the anchors, and bitumen paint shall be applied as an expansion release space.

2.3 Installation template

The thickness of the castable at the entrance of the kiln should be the same as the height of the first two ring bricks. When installing the template, a top stick of the same height as the brick should be welded in the anchor gap to support the template to the corresponding height. The anchor should be 20~40mm lower than the top rod as the anchor protection layer. When installing the template, use iron wires and steel bars to fix the template tightly to prevent the mold from running out. When we install the template, we usually start pouring when the length of 1000~1200mm is installed, which is convenient for feeding and vibration, and also convenient for the reservation of expansion joints.

2.4 Pouring kiln mouth castable

In the construction of the castable, it is necessary to first add the castable into the mixer for dry mixing, especially the castable for the binder and the material. After 1 minute of dry mixing, start to add water and stir. Adjust the amount of water according to the amount of water added in the construction requirements and the use of the site. After the mixing is evenly released, the mixed material is added to the kiln mouth mold and vibrated. The amount of water added should not be too large, which will easily cause the aggregate to sink during the vibration process and affect the overall performance of the castable. If the amount of water added is too small, the material will not flow. If the vibration is not in place, the phenomenon of empty mode will easily occur. One mold is poured into each mold, and an expansion joint is reserved.

2.5 Demoulding

The castable after pouring needs to be naturally dried for more than 12 hours to be demoulded, to prevent the castable from not condensing or the condensing strength is not high, and the castable is damaged during demolding.

3. Maintenance

After demoulding is completed, the castable needs to be naturally cured for 3 days before it can be used. The longer the curing time, the more moisture inside the castable will be discharged, which is more beneficial to use.

4. Summary

The construction technology of the kiln mouth castable mainly needs to grasp the performance of the material, control the amount of water added, and the vibration is in place. During the pouring process, it is necessary to pay attention not to run the slurry and leak the slurry. If the slurry leakage occurs, use fiber cotton to plug the mold in time. Gap.