Causes of Refractory Damage in Cement Kiln Transition Zone

　　In the cement kiln transition zone, refractory materials are subjected to corrosion and pressure from various aspects during use, resulting in a service life that is usually 40% lower than that in the firing zone. The following is an introduction to the reasons for the damage of refractory materials in the transition zone of cement kiln.

　　1. Effect of high temperature

　　The ambient temperature in the transition zone is relatively high, where the material temperature is 1000°C~1300°C, and the gas temperature is 1400°C~1600°C. Although the material is fully heated after entering the kiln, it cannot reach the firing state, which is affected by the firing zone. , the transition zone is in a thermally unstable state, and the kiln skin disappears over time, resulting in direct exposure of the kiln lining to high temperature environments.

　　2. Chemical attack

　　Volatile components such as melt in cement clinker, silicate low-melt in coal ash, K2O, SO2, KCl and other volatile components directly erode and infiltrate the surface of refractory bricks. Under the action of temperature gradient and concentration gradient of the erosion layer, the structure layer changes. As time goes by and the temperature field changes, the metamorphic structural layer is prone to cracking and falling off.

　　3. Coal injection pipe and fuel change

　　The temperature field in the transition zone is susceptible to continuous changes due to the influence of coal injection pipes and fuel changes.

　　The flame shape of the coal injection tube is affected by the particle size, ash content, volatile matter content and injection speed of coal powder. Improper adjustment of the internal and external wind of the coal injection pipe, excessive wind pressure of the coal delivery fan, and low secondary air temperature, etc., make the combustion speed of the pulverized coal lower than the forward speed of the pulverized coal particles in the kiln. unstable.

　　Refractory materials are prone to thermal fatigue when the temperature field changes repeatedly, and general materials cannot withstand the rapid cooling and rapid heating caused by temperature field changes, resulting in damage to the lining bricks in the transition zone.

　　4. Mechanical force

　　Since the rotary kiln shell has a certain inclination between the supporting points, as the rotary kiln operates, there will be periodic bending synchronous with the rotation.

　　The rotary kiln of the three groups of tugboats adopts a statically indeterminate structure. When each tugboat group has different expansion due to temperature differences, the coaxiality of the kiln shell will deviate, resulting in a large additional load. Especially in bad weather or sudden power failure, the kiln shell will be bent and deformed due to uneven heating up and down, so that the refractory bricks in the kiln will bear a large extrusion stress. Fracture, or even overall displacement.