What Factors Affect the Service Life of Rotary Kiln Lining?

2023-06-08

The burning zone of Rotary kiln is the place where the material is strictly used in the kiln lining. The factors affecting the service life of Fire brick in the kiln zone mainly include the following three points:

1、 Influence of Physical Property Index Advantages on Fire brick

Slag resistance refers to the resistance of refractory materials to chemical attack. Slag resistance is very important for Rotary kiln when the initial layer of kiln skin is formed and when the viscosity of materials is too large or the kiln skin falls off due to local high temperature.

Porosity and thermal conductivity play an important role in forming the initial layer of the Rotary kiln skin, and when the kiln skin falls off partially, refractory materials with large porosity and thermal conductivity will help to timely repair the kiln skin. But at the same time, it may show a great destructive effect, making the thin layer of Fire brick peel off.

In the production process of Fire brick, their physical and chemical changes generally do not reach the equilibrium state of calcination temperature and time, and there are also Fire brick that are not fully calcined. Therefore, when the Rotary kiln is no longer subject to high temperature in use, most Fire brick will undergo irreversible burning shrinkage due to the production of their own liquid phase and the filling of pores. Therefore, the stability of Fire brick volume at high temperature shall be considered when selecting fired Fire brick.

Layered peeling of hot surface is the main form of damage of Rotary kiln lining after thermal shock. If partial kiln skin falls off at the same time, the service life of Fire brick will be greatly shortened.

2、 Influence of calcination and fuel nozzle on Fire brick.

When using coal as fuel, the volatile and ash components of coal play a decisive role and directly affect the shape of the flame. Pulverized coal with high volatile content and low ash content can shorten the black flame and form a low-temperature long flame calcination. It is generally beneficial for protecting the kiln lining, but the volatile content is too high. If the flame is fast, the temperature of the kiln clinker can reach 1260 degrees Celsius or above. When the secondary air temperature exceeds 900 degrees Celsius, it is easy to burn out the coal nozzle, causing it to deform or burn out, and even create gaps, resulting in a disordered flame shape. The kiln lining is already damaged before it is replaced. The volatile content of coal is too low (less than 20%), and the ash content is too high (more than 28%). A large amount of coal powder cannot be completely burned, and it will settle in the material. The large amount of heat released by combustion can also damage the kiln skin.

The structure of coal spray nozzles is often not given enough attention in production. The shape and outlet size of the nozzle mainly affect the mixing degree and spraying speed of coal powder with the same primary air. In order to strengthen the mixing of air and coal, it is also possible to install air wings inside the nozzle, but it should be noted that excessive rotation radius of the swirling air can easily damage the kiln skin.

3、 Influence of raw meal composition fluctuation on Rotary kiln Fire brick.

Fluctuations in the chemical composition of raw meal will not only affect the baking quality of clinker, but also cause great damage to the Rotary kiln skin. When the aluminum content is too high and the liquid viscosity is high, the kiln skin will collapse in large quantities, which is difficult to control in operation, and is detrimental to the protection of the kiln lining. In production practice, the aluminum rate is generally controlled between 1.3 and 1.6; When adopting high saturation, high silicon content, and low liquid phase batching, it is easy to produce viscous material erosion, abrasion of the kiln skin, making the kiln skin thinner, and in severe cases, damaging the kiln lining. In production practice, when the silicon content is controlled at 2.5, the saturation ratio should not exceed 0.92. When the silicon content is controlled at 2.8, the saturation ratio should not exceed 0.9

Fluctuation of raw material feeding amount will do great harm to the Rotary kiln lining. When there is too much feeding in the kiln, the exhaust air volume at the kiln tail is generally reduced, and the amount of pulverized coal is increased for strong burning, so that the heat load of the burning belt increases rapidly, which will cause serious damage to the kiln lining. When there is too little incoming material in the kiln, the pulverized coal flame will obviously drop, and the kiln skin in this area will fall off and become thinner under high temperature, and rush to the thinner material layer. If the air volume and coal consumption are not adjusted in time, the kiln skin and Fire brick will easily be burned. In addition, fluctuations in raw material feeding rate can lead to instability of the thermal system inside the kiln, and excessive temperature can cause the kiln skin to fall off or be damaged.

In the actual operation of Rotary kiln, it is inevitable that the kiln lining is damaged. Attention to the above aspects and reasonable measures will help to extend the service life of Rotary kiln and reduce the economic burden.