Operation essentials of burning in the hottest sha

2022-09-22
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Operation essentials of machine shaft kiln calcination

whether the machine shaft kiln can achieve high-quality, high-yield and safe production depends largely on the calcination situation in the kiln. As for the calcination operation of mechanical shaft kiln, various factories have accumulated some effective experience for a long time. Through summary, the essentials of normal calcination operation of mechanical shaft kiln can be summarized as: first, stability, second, rationality, third balance, and fourth diligence. They are described as follows

I. stable primer

primer refers to that in the process of clinker calcination, the high-temperature material ball softens and deforms due to partial molten liquid phase, which has a certain adhesion, and binds other high-temperature softening material balls as a whole, forming a bonding material layer with a certain plasticity. Stable primer refers to that the depth, thickness, temperature and uniformity integrity of the original primer layer are stabilized when the machine shaft kiln is continuously fed or unloaded

if the primer layer is too deep, the wet material layer will be thick, the ventilation resistance will increase, and the pressure on high-temperature materials will increase, so it is easy to bond into large blocks, and it is easy to stick to the kiln wall and kiln frame; If the primer layer is too thin, the high-temperature zone will burn too fast, the clinker will not be calcined enough, it will be difficult to sinter, the primer layer will be loose, and the plasticity will be low. Seriously, the ball screw has almost no self-locking, while the trapezoidal screw has the primer collapse from the previous and current situation. If the temperature of the primer is too high, it is easy to form large blocks and circles; If the temperature is too low, the clinker cannot be burned at the required temperature. The rupture of the primer layer will produce serious partial fire. In addition, improper unloading and other factors will lead to the vicious accident of fire spraying

the change of the position depth, thickness and temperature of the primer layer is often referred to as the instability of the primer. The instability of the primer for primary medical supplies will cause the instability of the kiln condition (or kiln condition). The main factors of primer instability can be analyzed as follows:

1. Reasons for the variation of primer depth

① air volume. The wind causes the ball to warm up, the preheating process is shortened, the high-temperature zone is formed in advance, and the primer position is raised; On the contrary, the primer deepens when the wind blows. ② Unloading speed. The unloading speed is too fast, which makes the primer layer drop; On the contrary, the unloading speed is too slow, causing the primer layer to rise. ③ Feeding speed. The feeding speed is fast, the material layer is thick, the resistance is large, and the primer is deep; On the contrary, the primer becomes shallow. ④ Ball moisture. The ball has more moisture, the preheating time is long, and the primer position drops and deepens; On the contrary, the primer becomes shallow. ⑤ Coal quality. When the coal quality is good, the primer is shallow; On the contrary, the primer deepens

2. Reasons for the change of primer thickness

① coal material and coal quality. If the coal particle is coarse, the combustion time is long and the primer is thick; On the contrary, the primer is thin and concentrated. Low quality coal with high ash content and low calorific value will make the primer thinner; On the contrary, the primer becomes thicker. ② Air volume. Large air volume, sufficient oxygen and high primer temperature; On the contrary, the primer temperature is low. ③ Wind resistance. The pellet size is reasonable, the porosity is large, the combustion is sufficient, and the primer temperature is high; On the contrary, the primer temperature is low

II. Reasonable use of air and feeding

to stabilize the primer, it is necessary to use air and feed reasonably, and the following points should be achieved:

1. Sudden and 3D printing can shorten the production cycle, and the full air rate. "Full air" refers to the maximum blast air volume determined according to the best kiln conditions. Generally, about 8m 'air is required for LKG coal or about LM per kg clinker. Air, if the wind is small or the wind speed is low, the combustion slows down, the reduction atmosphere in the kiln increases, it is easy to form large blocks, the calcination belt lengthens, the temperature decreases, and the heat consumption increases. In addition, because the air volume in the kiln is proportional to the output, the insufficient air volume and the output decrease will also lead to the "reduction of energy consumption as much as possible", resulting in the deterioration of the kiln condition. In our investigation, we found that the output of some shaft kiln factories could not reach 60% of the design capacity, and the key problem was that they dared not use strong wind and full wind. Especially when there are many broken balls and the primer is shallow, if the wind increases, the broken balls are easy to be blown up, resulting in abnormal kiln conditions such as fire exposure, wind tunnel, etc., so they dare not use full wind, and the output has been unable to go up. The premise of fully opening full air is that the primer is complete and uniform, and trying to open full air can expose the weak links of primer, which can deal with the kiln surface in time and stabilize the primer

2. Insist on treating the kiln surface in full air operation. When dealing with abnormal kiln conditions, such as exposure fire, wind tunnel, partial fire, etc., many factories often operate with small wind, which blows with frequent ventilation, thus covering up the contradictions in the kiln and making the kiln air thermal system unstable. We should insist on gradually turning on strong wind and full wind, exposing the contradiction of primer in the kiln in the full wind, so as to take corresponding measures to solve many problems. Of course, to increase the total air rate is not to blindly use air regardless of the kiln conditions, but to appropriately increase the use of air according to the balance degree of primer in the kiln and the size of ventilation resistance. Blind or sudden high winds will cause serious exposure to fire or wind tunnel, and even puncture the primer layer, so that the primer is damaged, resulting in serious imbalance. Therefore, the total air is not always constant. Due to the fluctuation of raw materials and fuel composition, mechanical factors and process factors, the primer cannot always be stable. At this time, the air volume must be increased or decreased appropriately to make the primer tend to normal

3. Problems needing attention in rational wind use. We should be good at analyzing the reasons for the failure of full wind and take corresponding measures. Generally speaking, there are equipment reasons why the wind cannot go up, such as obstacles in the air inlet pipe of the kiln; There are reasons for the materials in the kiln, such as the powder in the kiln blocks the ventilation duct, reducing the porosity in the kiln and increasing the ventilation resistance; Or there are abnormal kiln conditions, mainly due to the imbalance of primer, such as refining edge, partial fire, deep fire in the middle, and even the collapse of the kiln with half of the fire column and half of the no primer. Because there are too many wet material layers in some parts, or too many underfired materials, there will be fire exposure, wind tunnel and so on when it is windward

4. Reasonable feeding. Reasonable feeding is a feeding operation that properly controls the feeding amount and keeps the kiln surface stable at an appropriate height. A relatively stable kiln surface height is a necessary condition and important measure to stabilize the primer. If the kiln surface is too deep or too full, it will have an adverse impact on the calcination. If the kiln surface is too full, the edge will burn slowly, easy to refine the edge, form rings, nodules, and even frame the kiln; If the kiln surface is too deep, the effective height of the kiln cannot be used, and the side wind is large, which is easy to show fire and fall holes. The height of the kiln surface should be based on the principle that the position of the primer should be controlled slightly above the lower part of the expansion port. The experience of many factories believes that if the kiln surface is stabilized at about 100mm below the kiln mouth and the primer is stabilized above the expansion mouth, it is easy to achieve full air

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