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How should the refractory brick of rotary kiln be protected?

Date:2019-10-10 10:05     writer:cement editor     Views:

The main function of the refractory brick of rotary kiln is to protect the kiln barrel from high temperature gas and high temperature materials and ensure the normal production.In industrial production, the service life of refractory bricks in the firing zone is very short, which often leads to unplanned kiln stopping for maintenance. It is a key factor affecting the quality, high yield, low consumption and annual operation rate of cement kiln.How should the refractory brick of rotary kiln be protected?

refractory brick

1. Erosion of refractory bricks of rotary kiln

In the process of clinker calcination, the gas temperature in the kiln is much higher than the temperature of the material. Every rotation of the kiln, the lining surface of the kiln is subjected to periodic thermal shock, the temperature variation range is 150~250℃, and thermal stress is generated within the range of 10~20mm surface layer of the lining.Kiln lining also withstands alternate radial and axial mechanical stresses of brick masonry caused by kiln rotation, as well as erosion and wear of calcined materials.Due to generate silicate melt at the same time, under the environment of high temperature is easy to interact with kiln lining refractory brick surface form initial layer, and at the same time the gap along the firebrick seep into the interior of the brick, and bonded refractory together, make the brick surface of 10 ~ 20 mm within the scope of the chemical composition and phase composition change, reduce the technical performance of refractory brick.When the sintering range of materials is narrow or a short flame is formed and a local high temperature is generated, the lowest temperature on the surface of the kiln skin will be higher than the solidification temperature of the material, the surface layer of the kiln skin will change from solid state to liquid state and fall off, and then form a new initial layer of the kiln skin after penetrating into the initial layer of the kiln skin from the surface to the inside.When this situation occurs repeatedly, the firing belt lining will gradually become thinner from thickness, or even completely fall off, resulting in partial exposure of the kiln cylinder and red kiln.In fact, the failure of kiln lining in the firing zone is exactly like this. The thickness of residual bricks in the high-temperature zone is generally distributed in an arc with a larger curvature radius, and sometimes the arc bottom falls on the inner surface of the kiln shell.

refractory brick

2. Protection of refractory bricks of rotary kiln

Slag resistance refers to the ability of refractories to resist chemical erosion, which is very important in the formation of the initial layer of the kiln skin and when the material has a large viscosity or local high temperature causes the kiln skin to fall off.

Thermal surface layering is the main form of damage of rotary kiln firing with kiln lining after thermal earthquake: if the local kiln skin falls off at the same time, the service life of refractory brick will be greatly shortened.

When using coal as fuel, the volatile content of coal and ash play a decisive role, directly affecting the shape of the flame.The pulverized coal with higher volatile content and lower ash content can shorten the black head, forming a kiln clinker temperature of more than 260℃ and the secondary air temperature of more than 900℃. It is easy to burn out the nozzle, making it out of shape or broken, producing a disordered flame shape and damaging the kiln lining before it is replaced.If the volatile content of coal is too low and the ash content is too high (over 28%), the incomplete combustion of a large amount of pulverized coal will settle into the material for combustion and release a large amount of heat, which will also damage the kiln skin.



Fuel nozzle structure is often not paid enough attention to in production, nozzle shape and outlet size mainly affect the mixing degree and ejecting speed of the same wind, sometimes in order to strengthen the mixing of wind coal, can also be installed in the nozzle wind wing, but pay attention to the cyclone feng rotation amplitude is too large scanning kiln skin.

The fluctuation of raw material feeding quantity is harmful to kiln lining.When there are too many incoming materials in the kiln, it is necessary to close the exhaust air volume at the end of the small kiln, increase the amount of pulverized coal for forced fire and strong burning, so that the heat load of the burning zone increases rapidly and the lining of the kiln is seriously damaged.When there are too few incoming materials in the kiln, the pulverized coal flame is obviously inclined downward, and the kiln skin in this area will fall off and become thin under the 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 firebrick will be easily burned.In addition, the fluctuation of raw material feeding quantity will lead to the instability of the thermal system in the kiln and the excessive temperature, which will cause the kiln skin to fall off or be damaged.

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