The cause analysis and countermeasures of refractory lining damage in rotary kiln

Date: 2019-07-22 Views:

Based on the summary and analysis of the common problems and damage reasons of inner lining of rotary kiln, this paper puts forward the countermeasures in the selection of resistant materials, construction management and operation, so as to provide reference for similar projects.
 

1. Cause analysis and countermeasures of fire resistance damage

 

1.1 mechanical stress damage

 

1.1.1 thermal expansion crushed firebrick


When the temperature of the kiln rises to a certain degree, the heat expansion will generate pressure in the axial direction of the kiln, causing the adjacent refractory bricks to squeeze each other. When the pressure is greater than the strength of the refractory brick, the surface of the refractory brick will flake off.The following measures should be taken:

(1) lay dry firebrick with reasonable side board, and leave 2mm fireclay seam for wet firebrick.

(2) keep a suitable brick retaining ring.

 

1.1.2 stress damage of iron plate


At the hot end of the brick, the clad iron plate reacts with the magnesium oxide in the brick at high temperature to form a magnesium-iron compound, which increases the volume and compreses the brick, resulting in horizontal fracture.In view of this situation, should change the fire brick veneer iron or fire mud instead.
 

1.1.3 large-area torsion dislocation of firebrick


Because the masonry is too loose, the kiln often starts and stops, which leads to the deformation of the kiln cylinder, causing the kiln cylinder to move relative to the cold surface of the lining brick, resulting in the twisted dislocation of the lining brick and the blasting crack of the brick surface.The following measures should be taken:

(1) during masonry, the large face of firebrick shall be hammered with wood hammer, and the lock brick shall be locked tightly, and wedge iron shall be added twice.

(2) maintain a stable thermal system.

(3) the deformation part of the kiln cylinder is leveled with high-temperature cement.

 

1.1.4 elliptic stress extrusion


Due to the increase of the gap between the rotary kiln wheel and the pad iron, the cylinder has a greater ellipticity, which results in the extrusion of refractory brick.The ellipticity of the cylinder should be tested regularly. If the ellipse value exceeds 1/10 of the diameter of the kiln, the gasket should be replaced or the gap of adjusting wheel belt should be increased.
 

1.1.5 iron stress extrusion of locking port


When locking bricks, too much iron lock mouth too tight, will lead to the formation of the lock mouth at the brick groove.The following measures should be taken:

(1) at the same lock. The number of lock iron shall not exceed 3 pieces.

(2) spacing of locking iron should be scattered as far as possible.

(3) when locking bricks inside and outside the opening tightness should be consistent.

(4) locking iron should be kept away from thin locking bricks as far as possible.

 

1.1.6 block ring extrusion firebrick


Block brick ring at the block brick (special-shaped brick) due to extrusion fracture and crack, in view of this situation should be changed into a single block brick ring for double block brick ring, block the whole brick on the block ring to avoid processing special-shaped brick.

1.2 thermal damage

 

1.2.1 overheating


Local overheating in the temperature of the furnace leads to the melting of refractory bricks and the formation of pits.In order to avoid this situation, the burner should be properly adjusted and the fireproof material should be selected in different parts.
 

1.2.2 thermal shock phenomenon


Due to the sudden change of temperature thermal stress caused by peeling and cracking of brick surface, it is mainly caused by the frequent opening and stopping of extremely hot and cold.The production operation should be stabilized and a reasonable heating and cooling kiln system should be established.
 

1.3 chemical erosion damage


1.3.1 city erosion


The vapor phase alkali salt compound infiltrates into the brick space to condense and solidify, and the horizontal permeation layer of alkali salt is formed in the brick body.
 

1.3.2 hydration phenomenon


MgO reacts with water to form Mg(OH)2, increasing the volume and thus destroying the overall structure of the firebrick.As MgO and CaO firebrick will have hydration reaction, the storage, transportation and masonry of firebrick should be protected from moisture, water and rain.

From the above damage mechanism of refractory brick, it can be seen that the standard construction of refractory materials can effectively extend the service life of refractory materials, and professional and dedicated masonry personnel is an important factor to ensure the quality of refractory construction.

 

2. Selection principle of refractories

 

In the selection of refractories, the following requirements should be met:


(1) high temperature resistance.Can run in the environment above 800T for a long time.

(2) high strength and good wear resistance.The refractories in rotary kiln must have certain mechanical strength to withstand the expansion stress at high temperature and the stress caused by shell deformation of rotary kiln.At the same time, because of the wear and tear of burden and flue gas, the refractories need to have better wear resistance.

(3) it has good chemical stability.To resist the erosion of chemicals in smoke.

(4) good thermal stability.Can withstand the alternating stress of incineration.In the case of unstable stopping, starting and rotating operation, the temperature in the kiln changes greatly, without cracking or peeling.

(5) thermal expansion stability.Although the thermal expansion coefficient of rotary kiln shell is greater than the expansion coefficient of rotary kiln refractory, the shell temperature is generally around, and the temperature of refractory material is generally more than 8001, which may lead to greater expansion of refractory material than rotary kiln shell, easy to fall off.

(6) stomatal rate should be low.If the porosity is high, the flue gas will penetrate into the refractory and erode the refractory.

Rotary kiln in the configuration scheme of refractory brick, the quality of refractory brick, the storage, the brick masonry of refractory brick, the kiln drying kiln, production each link improper handling can affect the service life of rotary kiln, through the adoption of a series of measures to maintain of firebrick, help to use the most economical kiln lining to achieve the best use effect.

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