Due to the increase of air ducts and the addition of equipment quality, the multi duct pulverized coal burner, especially used in the new dry process kiln, has no cooling at all and its working environment is worse. However, there has been no major incident in the domestic use of multi-channel pulverized coal burners so far, because of the lack of experience in operation and problems in the structure itself, its superior functions have not been fully played, and the expected role has not been achieved. The following problems often occur in use. (1) Burner zigzag deformation Multi air burner, because of its high quality, extends into the kiln and the kiln hood for a long time. In order to extend the service life of the burner, the outer tube shall be provided with 50 ~ 100mm thick refractory castable to maintain it from being burnt. Because there is clinker dust in the kiln, especially in case of flying sand, they are simply stacked at the front end of the burner extending into the kiln. The burner is composed of multi-layer casing, which has certain rigidity and little influence when the powder accumulation is less. However, when there is a large amount of accumulation, combined with the effect of high temperature, the rigidity of burner steel decreases, so the whole burner twists and turns. The jet direction of the bent burner changes out of control. Once the attack twists and turns, can not come straight. At this time, it is necessary to replace the old ones with the new ones to form a larger loss. In order to deal with this problem, the simple method is to use a long pipe with compressed air to blow off the accumulated dust at a fixed time; or use a long steel pipe to extend from the investigation hole door or the burning hole door on the side of the kiln head cover to take the investigation hole frame as the fulcrum, gently move or vibrate to remove the accumulated dust. It is necessary to be skillful and careful in this operation, otherwise the refractory castable outside the burner will be damaged. At this time, the castable has softened due to the high temperature effect, and if it is not careful or skilled, it may be damaged. Once it is found that the castable is damaged, it is necessary to pull out and replace it immediately. There must be no fluke mentality, and it is mistakenly thought that it will not be a big problem if it is persisted for a while. Because the burner is burnt out in a very short time after the burning and injection materials are damaged. (2) Damage of refractory castable The refractory castables of many air duct burners of many manufacturers will fall off soon after being used. At this time, the burners will be exposed to high temperature gas, which will soon burn and deform, and burn out in severe cases. There are many reasons for the damage of refractory castable, some are due to the unsuitable function of castable, some are due to the unreasonable construction, some are due to the improper operation, some are due to the high secondary air temperature, some are due to the incorrect operation during the maintenance period, etc., which will damage the refractory castable. In particular, the previous description of cleaning the burner head accumulation of material is not appropriate, there may be damage to the castable immediately. The damage of refractory castable can be seen as follows: Burst. The maintenance layer of the refractory castable outside the burner is easy to be damaged by bursting, because the quality of the castable is not good, the nail picking and the thermal expansion of the outer tube of the burner are not considered during the construction, and the surface of the castable is too smooth. Fall. Because the temperature of the secondary air is too high, the distribution is uneven after entering the kiln, and too much air enters from the lower part of the burner, which makes the castable maintenance layer outside the burner unevenly heated, forming a drop. Due to the invasion of high temperature gas, the temperature on both sides of the crack is higher at the initial stage. Because of the effect of temperature difference stress and the unreliable welding of some raking nails, lots of land will fall. Before the construction of castable, the surface of raking nails and outer pipes is not well derusted, and the castable and metal are not reliably consolidated. When the temperature is applied, the embroidered skin is separated from the metal and then falls off. Due to the lack of experience, when driving castables, there is no anti thermal expansion measures such as applying a layer of asphalt or wrapping a layer of tape on the surface of raking nails and outer pipes. When raking nails and outer pipes are heated and expanded, the refractory castables will be expanded and then dropped. Ablation. The refractory castable is scoured by high temperature, chemical action and wind speed, which makes it drop from the surface, gradually thinning and burning, and then failure. This failure is chronic and should be replaced when the nail is exposed. Only need to replace in time, will not form any loss, after replacing, lay the castable again for standby. (3) Damage of castable at burner end The part of the castable that is slightly damaged is the lower part of the front end of the burner, which is mainly affected by the temperature, speed and flow direction of the secondary air. It is related to the way of the cooler and the rotary kiln. The multi barrel cooler is evenly distributed along the center of the rotary kiln, the secondary air enters from each discharge port to the center by virtue of the suction in the kiln, and then flows back more evenly along the kiln axis. Thus, for the refractory castables at the burner head, the temperature is relatively low, generally about 500 ℃, and the wind speed is not high; the heat is relatively uniform, and the refractory castables at the burner head generally do not appear It has a long service life. The secondary air from the bottom of the single barrel cooler enters the kiln through the kiln head cover no matter it is placed in the downstream or in the upstream direction. Although the effect of the secondary air on the castable at the burner head is uneven, the secondary air temperature is generally 300-800 ℃, mostly 500-600 ℃, and the wind speed is not high, although there is a phenomenon of partial loss, it is not very severe. The grate cooler is under the kiln, the secondary air flows from the bottom to the top, and enters the kiln by virtue of the suction in the kiln. Because the grate cooler has high thermal efficiency and high secondary air temperature, which is generally 800 ~ 1200 ℃. The secondary air volume is large. For the new dry cellar with multi air burner, the secondary air consumption is more and the air entering the kiln is more
——Author：ebico