High-alumina dense refractory castable is one of the most widely used amorphous refractory products in the modern cement industry. It is often used in cement kiln mouths, kiln door covers, hot sections of grate coolers, etc. The castables in these parts are used in baking or Explosion is prone to occur during the ignition stage.
To address this problem, on the one hand, the quality of on-site construction and baking needs to be improved, and on the other hand, the anti-explosion performance needs to be improved.
Effect of cement addition amount on anti-burst performance
When the cement addition amount increases from 3% to 5%, the anti-burst temperature of the sample does not change, both are 600°C. When the cement addition amount continues to increase to 7% and 9%, the anti-explosion temperature of the sample increases from 600°C to 700℃ and 800℃, and when the cement content is further increased to 11%, the anti-burst temperature of the sample is still 800℃, and the anti-burst temperature does not continue to increase.
The main reason for bursting during use is that during the accelerated heating process, the stress (mainly water vapor pressure) generated inside the sample near the heating surface exceeds the ultimate strength of the sample. Increasing the amount of cement added within a certain range can Significantly improves its strength and thus its ability to withstand water vapor pressure, thereby improving its resistance to bursting.
Therefore, appropriately increasing the amount of cement added can effectively increase the anti-burst temperature.
The influence of fiber material
The anti-burst temperatures of high-aluminum dense refractory castables using polyvinyl alcohol, polyethylene, polypropylene and polyester fiber are 900℃, 600℃, 600℃ and 800℃ respectively. Polyvinyl alcohol has the best anti-burst performance.
Polyvinyl alcohol (water-soluble) has a low water-soluble temperature (80°C). When the sample is heated, the polyvinyl alcohol fiber can produce an exhaust channel earlier. The earlier the exhaust, the pressure generated by water vapor will have a greater impact on the refractory castable. The damage is also smaller.
Therefore, polyvinyl alcohol fiber is suitable to be used as its explosion-proof agent.
Effect of fiber length and diameter
When the length of the explosion-proof fiber increases from 3mm to 4-5mm, the anti-burst temperature of the sample does not change (both are 600°C). When the fiber length continues to increase to 6mm, the anti-burst temperature increases to a certain extent, reaching 700°C. ℃. When the fiber diameter increases from 6 μm to 30 μm, the anti-burst temperature of the sample increases to a certain extent. When the fiber diameter continues to increase from 30 μm to 40 μm, 60 μm and 120 μm, the anti-explosion temperature of the sample does not change (all are 600°C ).
Explosion-proof fibers that are too short make it difficult to fully disperse when the castable is mixed, and it is more difficult to form a network-like exhaust channel inside, resulting in poor anti-explosion effect. However, the channels left after longer explosion-proof fibers are burned out are longer and are easy to connect to each other to form The passage that connects with the outside world is more conducive to the ventilation of the material and is beneficial to improving the anti-explosion performance. However, the increase in the length of the explosion-proof fiber will lead to poor dispersion of the fiber and poor fluidity of the castable. If the diameter of the explosion-proof fiber is too small, the resistance to bursting will be poor (caused by capillary phenomena), while if the diameter of the explosion-proof fiber is too thick, the number of breathable channels formed by the fiber will be reduced, which will not be enough to form a favorable through-network, and the bursting resistance will also be reduced. unfavorable.
Therefore, when the length of the explosion-proof fiber changes in the range of 3-5mm and the diameter changes in the range of 30-60μm, the anti-explosion performance of the high-aluminum dense refractory castable does not change basically.
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Through the above analysis of factors affecting the burst resistance of high-aluminum dense castables, the following conclusions can be drawn:
(1) Appropriately increasing the amount of cement added will play a certain role in improving the bursting performance.
(2) Explosion-proof fiber materials have a significant impact on the burst resistance, and polyvinyl alcohol fiber has a good effect on improving the burst resistance of high-aluminum dense refractory castables.
(3) The length and diameter of the explosion-proof fiber have little impact on the anti-explosion performance within a certain range.