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The service life of the kiln head burner castable has always been unsatisfactory, ranging from 3 months to 6 months, which seriously affects the kiln operation rate and the quality of clinker. After a lot of production research, we found a way to extend its service life, so that the service life of the burner castable can reach one year, which is 3 times the original service life.
(1) Material of anchors. The temperature of the burner is very high, and the surface temperature of its lining is as high as 1500℃ or above. If the heat-resistant steel anchors have poor high temperature resistance, oxidation reaction will easily occur, reducing its strength and causing the castable to fall off. The thermal stress generated by the expansion of the anchors will also cause cracks and fissures in the castable, destroying the structure of the castable and reducing its strength.
(2) Welding of anchors. The burner surface was not cleaned and rusted before welding, which affected the welding quality of the anchors, causing the anchors to open and causing the refractory castable to fall off; the contact area between the anchors and the burner steel structure surface is too small, and the welding area is also too small, which reduces the welding firmness of the anchors and causes the anchors to open and fall off.
(3) The unreasonable selection of the diameter, size and arrangement of the anchors affects the construction quality and use effect of the castable.
(1) The material of refractory castables. Production practice shows that the material of refractory castables directly affects its service life. The short service life of castables is one of the main reasons for the inappropriate selection of its material.
(2) The thickness of refractory castables. Increasing the thickness of castables is equivalent to increasing its strength, which is beneficial to protecting the burner. However, too thick castables can easily cause the burner to deform, and too thin castables can directly affect the strength of castables. Both too thick and too thin castables can affect their service life.
(3) Construction of refractory castables. In order to make the castable have better fluidity, the manufacturer adds too much water when making the castable, which increases the porosity of the castable, reduces the density and strength; the pouring space between the mold and the burner is very small and is densely covered with many nails. It is extremely difficult to operate the vibrating rod during pouring and vibrating, which affects the density of the castable; the construction workers place the burner horizontally for the convenience of construction, which directly affects the pouring and vibration; the maintenance is not sufficient, the later strength of the castable has not been fully exerted before it is put into use, and the heating rate is not controlled, causing cracks in the castable and even explosion.
Harmful components such as potassium, sodium, sulfur, and chlorine from the raw fuel combine at high temperatures to form sulfates and hydrochlorides, which penetrate into the castable and cause expansion, resulting in cracking and peeling of the castable.
The high-temperature rotating gas from the grate cooler carrying a large amount of dust directly washes the refractory castable on the burner, especially the high temperature at the lower front end, which is more likely to cause cracks and fissures, and the castable is susceptible to destructive wear. After the castable at the end of the burner falls off, the end steel body is directly exposed to high temperature and deformed, affecting the flame and calcination.
When the rotary kiln is in continuous operation, its thermal system is relatively stable, and the thermal stress generated inside the castable is not very destructive. However, the thermal shock caused by sudden stop and rapid cooling is very harmful, which will cause the castable to crack and fall off. Especially at the lower front end of the burner, in severe cases, the castable with a thickness of about 10mm will fall off.
High-temperature clinker will accumulate on the upper part of the front end of the burner, and the alkaline compounds contained in the clinker will react with the castable to produce low-melting products, which will cause different degrees of chemical corrosion to the castable. At this time, the staff on duty often only use steel chisels to clean it, which will artificially damage the castable under the accumulation.
After careful analysis and comparison, it was decided to use corundum-mullite special refractory castable for coal injection pipe.
The spikes are made of 1Cr25Ni20Si2 heat-resistant steel with a diameter of Φ6 mm × 6 mm and a "V" shape. The bottom of the "V" shape needs to be processed to have a welding surface of about 20 mm. The spikes are treated with anti-oxidation and anti-expansion treatments, and a layer of about 2 mm asphalt is coated on the surface. A layer of plastic electrical tape is wrapped around the ends, and they are arranged in a "cross" shape vertically and horizontally, with a spacing of approximately 50 mm.
(1) Make an iron mold with accurate dimensions and easy installation according to the thickness of the castable material of 80 mm.
(2) Fix the burner vertically.
(3) Clean the accumulated material inside the mixer.
(1) The amount of water added to the castable should be controlled at about 5%.
(2) Start construction from the lower part of the burner. Pay special attention to the pouring and vibrating process during the operation, because the pouring space is small and there are many nails in between, which makes it extremely difficult to operate the vibrating rod. The vibration should be comprehensive and meticulous, and no vibration should be missed. It should be vibrated until the slurry is returned to ensure that the castable between the mold and the burner is vibrated and compacted.
(3) The castable should be poured and vibrated before it starts to set, otherwise it must be discarded to avoid affecting its performance.
(4) After the construction is completed, there should be sufficient curing time, and it can be demolded and used only after it is completely hardened.
In the first 2 hours of use, the temperature should be raised slowly, and the heating rate should be controlled to be less than 2 ℃/min.
Check the upper part of the front end of the burner frequently. If a small amount of high-temperature clinker is accumulated, it is necessary to use high-pressure air to blow it out. Try to avoid using a steel chisel to clean it, so as not to damage the castable under the accumulated material.
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