What are the temperature distribution characteristics in the phenomenon of off ignition in lime vertical kilns
In the production process of lime shaft kiln, the phenomenon of partial fire often occurs, which not only affects the quality and efficiency of lime calcination, but also shortens the service life of lime kiln. When partial fire occurs, the temperature distribution in the kiln will have significant characteristics. Understanding these characteristics is very important for preventing and controlling partial fire.
The main characteristics of the partial fire of the lime shaft kiln are that the firing zone is inclined, the temperature of the exhaust gas and the ash temperature are high, and when it is serious, the local part of the furnace top is red, the ash is discharged and the red material is discharged. The temperature of each layer of the furnace body is uneven, and the temperature difference of each point on the same layer is large. When the partial burning is serious, a "channel" will be formed in the furnace, the quick burning and overburning in lime will increase significantly, and the temperature difference of lime block is large.
Under normal conditions, the temperature distribution in the lime shaft kiln should be relatively uniform. Limestone enters from the top of the kiln. As the material moves down, coke burns in the gap between raw materials, releasing heat, which gradually decomposes limestone into lime. During this process, the temperature increases gradually from the preheating zone to the calcination zone, and then decreases gradually in the cooling zone. However, when partial fire occurs, the uniform temperature distribution is broken.
Partial fire is usually caused by uneven mixing, uneven cloth distribution and uneven ash discharge. Uneven mixing and distribution will lead to large differences in local calcination temperature and decomposition rate of limestone in the shaft kiln. The quicklime has a large proportion and a fast sinking speed, forming a channel in one direction of the shaft kiln; The better calcined lime has a small proportion and a slow sinking speed, which will lead to over burning and nodulation of lime. Nodulation will hinder the uniform distribution and normal flow of air flow and further aggravate the phenomenon of partial fire.
When partial fire occurs, the temperature distribution in the kiln becomes extremely uneven. The firing belt will tilt, with high temperature on one side and low temperature on the other. The limestone at the high temperature side will decompose rapidly and overheat, and even bond with the kiln wall to form a sticky kiln. The limestone at the low temperature side may be burned due to insufficient temperature. This uneven temperature distribution will lead to serious deterioration of lime quality, and increase the proportion of raw and overburned lime.
In addition, partial fire will also lead to uneven kiln wall temperature. Because the limestone on the high temperature side is bonded to the kiln wall, the temperature of the kiln wall will increase significantly. The kiln wall temperature at the low temperature side is relatively low. This temperature difference will increase the thermal stress of the kiln wall and increase the risk of cracking and damage of the kiln wall.
In order to prevent and control the phenomenon of partial fire, it is necessary to carry out technical transformation and process improvement on the lime shaft kiln. For example, the limestone is evenly distributed in the kiln by optimizing the mixing and distribution process; Prevent the formation of sticking kiln and tumor block through regular operation of material lowering line; By improving the air supply system, the air permeability in the kiln is improved and the air flow is more uniform.
In addition, it is also necessary to strengthen the training of operators and improve their operation level. Operators need to pay close attention to the temperature distribution and material status in the kiln, and adjust the process parameters in time to ensure the stable operation of the lime shaft kiln.
The characteristics of temperature distribution in the partial fire phenomenon of lime shaft kiln are as follows: the firing zone is inclined, the temperature of each layer of the furnace is uneven, the temperature difference of each point in the same layer is large, and the temperature of the kiln wall is uneven. Understanding these characteristics is of great significance for preventing and controlling partial fire.
