The mechanism of phosphate combined with high alumina refractory bricks hanging on kiln skin
Phosphate-bonded high-alumina bricks are often used as lining materials in cement-coordinated waste incineration rotary kilns. Because of their better wear resistance, the use of transition zones and cooling zones in the kiln is longer than that of ordinary high-alumina bricks. 2 to 3 times longer. In use, the kiln skin mechanism of phosphate-bonded high-alumina bricks is as follows:
1) Using phosphate combined with high alumina refractory bricks and phosphate wear-resistant bricks as the lining material of cement rotary kiln for waste incineration power generation, with the participation of appropriate waste and pulverized coal combustion temperature and the participation of molten coal ash, 15 %~20% of the liquid phase, while the cement clinker produces about 20%~25% of the liquid phase. When the liquid phase and viscosity between the clinker and the surface of the kiln lining refractory bricks reach a certain level, the first layer of kiln skin begins to stick. There is a reaction between the kiln skin and the brick surface, that is, between the waste incineration ash powder and clinker, coal ash and refractory bricks, and the reaction also penetrates into a certain depth of the brick surface, and the penetration depth mainly depends on the refractory bricks and waste incineration. Chemical composition of ash, clinker, coal ash. When the phosphate-bonded high alumina brick Al2O3≥80%, the first layer of kiln skin and permeable layer formed is mainly C2AS.
2) The firmness and density of the kiln skin of the phosphate-bonded high alumina refractory bricks mainly depends on the generated C2AS. The more C2AS and the less CAS2, the firmer and firmer the kiln skin, and vice versa. The change of the silicon rate and aluminum rate of the clinker also plays a decisive role in whether the kiln skin can be fastened or not. Salt combined with high alumina bricks is used as the lining material of cement rotary kiln for waste incineration power generation. The performance of the kiln skin depends on the content and chemical composition of AI2O3 and Fe2O3 in waste incineration ash, coal ash and cement materials. The supply of surface metamorphic layer and the depth of reaction penetration are also important reasons that directly affect the firmness and density of the kiln skin.
3) Phosphate-bound high alumina refractory bricks are used as lining materials for cement rotary kilns for waste incineration power generation. Practice has proved that using phosphate-bound high-alumina bricks containing Al2O3 ≥ 80% as kiln lining materials, when the temperature is lower than 1450 ℃, the liquid phase is insufficient. When the temperature is higher than 1490℃, too much liquid phase will easily cause burning flow, so the normal temperature difference of the kiln skin hanging on the cement rotary kiln of waste incineration power generation is 20℃~30℃ .
4) When the temperature is low, the kiln skin cannot be hung or hung firmly, so that there is a lack of a layer of kiln skin with sufficient thickness for protection between the brick surface and the ash powder and materials in the kiln. For machine-pressed phosphate-bonded high-alumina bricks, due to their high density and high thermal conductivity, if the kiln lining brick body is not thick and the kiln skin is too thin, it is very easy to cause the red kiln of the cylinder.
5) When the staff operates carelessly, there is too little material or running coal, or the amount of garbage is too small, and the exhaust cannot be enlarged in time, the flame extends deep into the kiln to the position where the kiln skin is not thick enough, and the material in the kiln accumulates. This causes local heating in the kiln, resulting in rapid erosion of the kiln skin and kiln lining. Therefore, when using phosphate combined with high alumina bricks as the kiln lining material for the decomposition zone and preheating zone, the accumulation and agglomeration of local materials in the kiln should be prevented.
6) Phosphate combined with high alumina refractory bricks is used as the kiln lining material of the rotary kiln for waste incineration power generation. It often occurs that the brick lining is heated too fast when the kiln is opened, and the kiln skin is damaged due to excessive cooling when the kiln is stopped. When the kiln skin falls off, the temperature of the brick surface rises rapidly by 500°C to 600°C, causing the brick body to be damaged by strong thermal shock; when the kiln is stopped, cold air quickly enters the kiln, causing the temperature of the brick body to drop sharply, making the brick surface original. The cracks expand rapidly causing bursts. Therefore, thermal shock caused by drastic temperature changes must be strictly controlled.
7) Summary: The mixing amount of garbage and pulverized coal should be uniform, so as to avoid high and low temperature, resulting in unstable airflow temperature in the kiln. When the temperature is controlled at 1450℃~1490℃, and C2AS is formed on the surface of the refractory brick, the kiln skin can be hung well, and it will not burst and peel off in frequent kiln shutdowns.