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The use of refractory bricks in cement kiln directly affects the operating rate of cement kiln and clinker production. The service life of the new dry-process cement kiln refractory bricks should not be less than 10 months, and the brick consumption per ton of clinker should be less than 500 grams. Otherwise, the reasons affecting the life of the refractory bricks should be carefully analyzed in order to improve and improve.
There are three main factors affecting the service life of refractory bricks in the kiln:
First, the quality and configuration of refractory bricks;
Second, the process production status;
Third, the storage and construction of refractory bricks.
The first aspect is the premise. Choosing high-quality products and reasonable selection configuration is the necessary condition to ensure normal use. Proper storage and high-quality masonry are reliable guarantees for prolonging the service life of refractory bricks. It will suffer from the comprehensive damage of mechanical stress and chemical stress. The damage phenomenon and its causes are analyzed as follows:
Mechanical stress damage
1. Thermal expansion smashes refractory bricks
When the temperature of the kiln rises to a certain extent, the thermal 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 refractory brick surface will be peeled off. The following measures should be taken in response to this situation: 1. Dry refractory bricks, set reasonable sideboards, and set 2mm fire mud joints for wet refractory bricks; 2. Leave suitable brick blocks.
2, iron plate stress damage
At the hot end of the refractory brick, the magnesium oxide in the surface iron plate and the magnesia brick reacts at a high temperature to form a magnesium iron compound, and the compound is increased in volume, and the refractory brick is extruded and fractured horizontally. In response to this situation, the refractory brick veneer should be replaced or replaced with fire mud.
3, refractory brick large area skew misalignment
Because the masonry is too loose, the kiln is frequently opened and closed, and the kiln cylinder is deformed, so that the relative movement of the kiln cylinder and the cold surface of the lining brick causes the lining brick to be twisted and misaligned, and the brick surface is cracked and dropped. The following measures should be taken in response to this situation:
(1). During the masonry, the large surface of the refractory brick is hammered with a wooden hammer, the locking brick should be locked, and the wedge iron is carefully added twice;
(2). Maintain a stable thermal system;
(3). The deformation part of the kiln cylinder is flattened with high temperature cement.
(4) Elliptical stress extrusion
The kiln wheel has a larger rug gap to produce a larger ovality resulting in refractory brick extrusion. For this case, the ellipticity of the cylinder should be checked periodically. If the ellipse value exceeds 1/10 of the diameter of the kiln (for example, 4.7 m kiln diameter, the maximum ellipse value is 0.47%), the pad should be replaced or the horn should be added to adjust the wheel gap.
4, the lock iron stress extrusion
When the brick is locked, the iron in the lock is too tight, which will result in the formation of a brick groove at the lock. The following measures should be taken in response to this situation:
(1). The iron at the same lock is not more than 3 pieces;
(2). The spacing of the lock iron is dispersed as much as possible;
(3). When the brick is locked, the outer mouth is tight and uniform;
(4). Lock the iron as far as possible from the thin lock brick.
5, brick ring extrusion refractory brick
The retaining bricks (shaped bricks) at the brick blocking ring are subject to crushing and cracking, and in this case, the single-track brick ring should be changed into a double-stop brick ring, and the bricks should be built on the brick blocking ring to avoid processing the shaped bricks. .
Local overheating of the kiln temperature causes the refractory brick to melt and form a pit. In order to avoid this, the burner should be properly adjusted and a reasonable refractory material should be selected at different locations.
2, thermal shock phenomenon
The thermal stress caused by sudden changes in temperature causes spalling and cracking of the brick surface, mainly due to the frequent opening and closing of extremely cold and extremely hot. Stable production operations should be established and a reasonable heating and cooling kiln system should be established.
3. Chemical erosion damage
(1). Alkali erosion
The gas phase alkali salt compound penetrates into the voids of the brick body to condense and solidify, and forms a horizontal permeation layer of the alkali salt in the brick body, and the alkali salt content in the kiln should be reduced in the production.
(2) Chromium erosion
Under the attack of excess alkali salt, chrome ore and K2 (Na2Cr6) are formed by free (K, Na) 2O. The hexavalent alkali chromate produced by chemical reaction not only damages the brick body, but also pollutes the environment and seriously poisons the body. Health, so the use of magnesium chrome bricks should be reduced and stopped, replaced by magnesium aluminum spinel, magnesium iron spinel, dolomite bricks and so on.
(3) Hydration phenomenon
MgO reacts with water to form Mg(OH)2, which increases in volume and destroys the overall structure of the refractory brick. Since refractory bricks containing MgO and CaO have hydration reaction, it is necessary to ensure that moisture, water and rain are avoided during storage, transportation and masonry of refractory bricks. From the damage mechanism of the above refractory bricks, it can be concluded that the standardization of refractory construction can effectively extend the service life of refractory materials. Professional, dedicated and experienced furnace construction is an important part of the use of refractory materials.
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