Phosphate-bonded high-alumina bricks are often used as lining materials in cement-coordinated waste incineration rotary kilns. Due to their good wear resistance, they are used 2 to 3 times longer in the transition zone and cooling zone of the kiln than ordinary high-alumina bricks. In use, the specific mechanism of phosphate-bonded high-alumina bricks hanging kiln skin is as follows:
part.1 Phosphate-bonded high-alumina bricks and phosphate wear-resistant bricks are used as kiln lining materials for waste incineration power generation cement rotary kiln. Under the appropriate combustion temperature of garbage and coal powder and the participation of molten coal ash, 15% to 20% of liquid phase is formed on the surface of refractory bricks, and at the same time, the amount of liquid phase produced by cement clinker is about 20% to 25%. 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. The reaction between the kiln skin and the brick surface, that is, between the garbage incineration ash powder and the clinker, coal ash and refractory bricks, also penetrates to a certain depth of the brick surface. The penetration depth mainly depends on the chemical composition of the refractory bricks and the garbage incineration ash powder, clinker and coal ash. When the phosphate combined with high alumina brick Al2O3≥80%, the first layer of kiln skin and the penetration layer generated are mainly C2AS.
part.2 The firmness and density of the kiln skin of the phosphate combined with high alumina brick mainly depends on the generated C2AS. The more C2AS and the less CAS2, the firmer the kiln skin is, and vice versa, the looser it is. The changes in the silicon and aluminum ratios of clinker also play a decisive role in whether the kiln lining can be firmly attached. The higher the content of Fe2O3 and K2O+N2O in the clinker, the more molten minerals are generated and the looser the kiln lining is. Therefore, the phosphate combined with high-alumina bricks as the lining material of the waste incineration power generation cement rotary kiln depends on the content and chemical composition of AI2O3 and Fe2O3 in the waste incineration ash, coal ash and cement materials. The supply of CaO in the material to the brick surface metamorphic layer and the depth of reaction penetration are also important factors that directly affect the firmness and density of the kiln lining.
part.3 Phosphate combined with high alumina bricks as kiln lining materials for waste incineration power generation cement rotary kiln. Practice has proved that when phosphate combined with high alumina bricks containing Al2O3 ≥ 80% are used as kiln lining materials, when the temperature is lower than 1450℃, the liquid phase is insufficient, and the kiln skin cannot be hung or cannot be hung firmly. When the temperature is higher than 1490℃, the liquid phase is too much and it is very easy to produce burning flow. Therefore, the normal kiln skin control temperature difference of waste incineration power generation cement rotary kiln is 20℃~30℃.
part.4 When the temperature is low, the kiln skin cannot be hung or cannot be hung firmly, so there is a lack of a kiln skin of sufficient thickness for protection between the brick surface and the ash powder and materials in the kiln. For machine-pressed phosphate combined with high alumina bricks, due to their high density and high thermal conductivity, if the kiln lining bricks are not thick and the kiln skin is hung too thin, it is very easy to cause the cylinder to red kiln.
part.5 When the staff is not careful in operation, there is insufficient material or coal is lost or the amount of garbage is too little, and the exhaust is not increased in time, the flame extends deep into the kiln to the position where the kiln skin is not thick enough. In addition, the accumulation of materials in the kiln will also cause the temperature in the kiln to rise locally, causing the kiln skin and kiln lining to melt rapidly. Therefore, when using phosphate combined with high-alumina bricks as the kiln lining materials for the decomposition zone and preheating zone, the accumulation and agglomeration of local materials in the kiln should be prevented.
part.6 Phosphate combined with high-alumina bricks as kiln lining materials for waste incineration power generation rotary kiln, it is often the case that the brick lining is heated too quickly when the kiln is opened, and the kiln skin is damaged by too rapid cooling when the kiln is stopped. When the kiln skin falls off, the temperature of the brick surface rises rapidly by 500℃~600℃, 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, causing the original cracks on the brick surface to expand rapidly and cause explosions. Therefore, the thermal shock caused by drastic temperature changes must be strictly controlled.
The amount of garbage and coal powder should be evenly mixed to avoid the temperature being high and low, which will cause the air flow temperature in the kiln to be unstable. When the temperature is controlled at 1450℃~1490℃ and C2AS is generated on the surface of the refractory bricks, the kiln skin can be hung well, and it will not crack or peel off during frequent kiln stops.
HOME