1、Mechanical damage
Subjected to a combination of pressure, pull, twist, shear mechanical stress. Kiln rotation, cylinder ellipticity, lining brick and cylinder body and between the brick and brick extrusion, twisting, kiln cylinder body deformation, will produce mechanical stress between the brick lining. When the cylinder body and the belt gap is larger, so that the kiln cylinder body ellipticity increases, lining brick subject to alternating stress increases, the most serious mechanical stress on the belt part of the wheel. I plant in the renewal of the brick has occurred after the kiln barrel bending, violent vibration coupled with the kiln lining when there is local overheating, causing carcass deformation extrusion lining, and then the wheel adjustment takes a long time, 6m from the kiln in front of the entire third wheel with a red kiln, refractory bricks in a part of a large area off, digging, the wheel adjustment normal kiln no longer vibrate, this time after no red kiln phenomenon.
2、Sharp cooling and rapid heating
A large amount of literature points out that the alkaline expansion coefficient is large and produces huge thermal stress during the heating process, so the heating should be slow when drying the kiln, so that the expansion of the kiln cylinder complements the expansion of the brick to play the role of kiln compensation. This is the key to using alkaline bricks. But in actual production is difficult to accept 10 ~ 20 several hours of kiln drying time, found the problem directly start high temperature fan for rapid cooling kiln. After cooling into the kiln can be found without kiln skin of magnesia chrome brick spalling damage, 1680 silicomel brick all occur surface spalling, fracture at the surface hard, some broken pieces obviously hanging on the brick. Firing band of magnesium-chromium brick due to the kiln skin buffered temperature fluctuations, the damage is smaller. After the inspection in order to grab production, the requirement of fast cold kiln is bound to lead to damage to the brick, for the second carcass temperature rise laid the causative factors, refractory brick accidents are frequent.
3、Change of the original fuel
Only in stable kiln conditions, brick lining to adhere to and maintain a solid kiln skin, kiln lining life can be guaranteed, and the stability of the thermal regime requires the stability of the original fuel, due to difficulties in the supply of coal, coal ash from 32% to 45% change between, initially to adapt to the high ash coal, into the kiln raw material saturation is relatively high, but the coal ash changes too often, and no coal homogenization yard, so that the raw material into the kiln and coal ash It is difficult to correspond to the ash content of the coal, which has a great impact on the condition of the kiln.
After the inspection and feeding, the solid kiln skin is about 20m, and the magnesium-chromium bricks are completely under the kiln skin. But due to the fluctuation of coal quality, kiln skin not end frequently sticky hanging and fall off, and brick close adhesion in the brick to form a mechanical anchor of the kiln skin off with the brick body layer together with peeling off, so that the brick body thinning, kiln skin shortened to about 16m, so that part of the magnesium-chromium brick lose kiln skin protection, kiln skin end due to coal ash sink, kiln skin thicker, less liquid phase amount of raw material here to wash abrasion magnesium brick.
Firing belt with direct bonding magnesia-chromium brick is mainly due to direct bonding magnesia-chromium brick high temperature resistance, easy to hang kiln skin, but due to the brick silicate content is very low (0.5% ~ 2.5% SiO2), brick magnesia, spinel is mainly direct bonding, silicate phase isolated in the gap, surrounded by magnesia, spinel grains, high temperature resistance improved, but the microstructure toughness is poor, so that the brick thermal shock stability, the Alkali corrosion resistance and resistance to oxidation and reduction of atmospheric changes in the ability to have a considerable reduction.
Especially in the kiln to open and stop more frequently used, life is greatly shortened, no kiln skin as a barrier magnesia chrome brick, surface temperature changes with the kiln conditions, frequent replacement of kiln skin, will make the expansion coefficient of magnesia chrome brick thermal fatigue, chemical erosion, liquid phase alkali salt infiltration into the brick structure deterioration, reduce the resistance to thermal fatigue performance, so that the carcass temperature in this several rings of magnesia chrome brick at rising, and eventually red kiln, in order to fill hanging kiln skin in the carcass Surface spraying water forced on the fire brick to form kiln skin, but the kiln's thermal expansion of the brick lining within the compressive stress compensation role disappeared, is not conducive to brick lining life, plus, the brick is too thin to form a stable kiln skin, many times red kiln. Only into the kiln digging patch, the thinnest part of the brick is only about 40cm. In the kiln mouth at 2m magnesium-chromium brick has also appeared similar situation.
Into the kiln raw material satiation ratio stable moderate, but the coal ash is large, so that the firing zone to form a 'low temperature' kiln skin, loose porous not solid, when the coal ash suddenly reduced, and the coal jet pipe walking mechanism failure, the coal jet mouth flush with the kiln mouth, can not be sent into the kiln, so that the kiln temperature rises, the kiln ring off, "low temperature "Kiln skin is not stable, coupled with clinker dust scouring, erosion, and the extrusion of dozens of meters of bricks in the kiln, so that 2m at the shaped brick cracking, falling brick, red kiln.
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