During the use of the rotary kiln, when abnormal firing conditions occur in the rotary kiln, various indicators in the kiln and the theoretical curve of product firing will change greatly, and are extremely unstable, and the quality of the fired products will also be affected. It won't be stable. Abnormal conditions in rotary kilns usually include: under-fire in the entire kiln, large temperature difference between the upper and lower sections of the kiln, mute bricks in the kiln, burnt bricks in the kiln, inaccurate control of the firing temperature, and preheating of the billet. Body resurgence, etc. Here we briefly introduce the causes and treatment methods of under-fire in the whole kiln.
When the entire rotary kiln is underfired, the stack of bricks in the kiln will be red or dark red, and the fired bricks will be underfired. The product quality will not meet the requirements and the strength will be low, producing what is often called "green bricks".
The reasons for the lack of fire in the whole kiln are:
① If the rotary kiln pyrotechnics are not precise enough in controlling the fire intensity, especially when there is a significant difference in light between night and day, small fires will often be misjudged as large fires. This kind of visual misleading leads to a large deviation in the fire temperature, which may affect the stability of the entire firing process and product quality.
② During the operation of the rotary kiln, the addition of external fuel is a crucial link. However, if the principle of "add frequently, add less, add small amounts many times" is not followed in this step, it may cause large fluctuations in the heat in the kiln. Specifically, if external fuel is not added diligently, in small amounts, and multiple times, the temperature in the kiln may rise suddenly due to the concentrated addition of fuel, and then drop rapidly due to exhaustion of fuel. This unstable change in heat will not only affect the operating efficiency of the rotary kiln, but may also adversely affect the quality of the product.
③ We must be extremely cautious when selecting fuel for the rotary kiln. If the ash content of the selected fuel is too large, the calorific value is low, and the overall quality is poor, and the coal amount is still put in according to the standards of better quality fuel, then this will lead to an obvious problem: the total heat in the kiln will be Unable to meet production needs. Specifically, this lack of heat will directly cause the temperature in the kiln to fail to rise to the level we expect and need. Temperature is a key factor in the operation of the rotary kiln, which directly affects product quality and production efficiency.
④ During the operation of the rotary kiln, the adjustment of the air damper is a link that requires fine control. If the air damper is used too high, it will cause excessive ventilation in the entire kiln. This excessive ventilation will cause a problem: a large amount of heat will be quickly removed from the kiln, making it difficult for the temperature in the kiln to rise to the level required by the firing process. We all know that temperature is a crucial factor in the firing process, which directly affects the quality and performance of the product.
⑤ In the operation of the rotary kiln, the adjustment of the air damper is a delicate and critical process. If the damper is used too low, the ventilation in the kiln will be too small. This lack of ventilation creates a significant problem: the fuel inside the kiln does not receive a sufficient amount of oxygen when burned. We all know that fuel combustion requires sufficient oxygen to support its combustion process and release sufficient heat. However, when the ventilation volume is too small, the combustion intensity of the fuel will be significantly inhibited, and the heat released per unit time will also be greatly reduced. The direct consequence of this situation is that the heat generated by the combustion of the fuel is not enough to raise the temperature in the kiln to the level we expect and need.
When encountering a lack of fire in the entire kiln, the following operating methods should be adopted. to change the roasting conditions in the kiln
① In the daily operation of the rotary kiln, it is crucial to detect the temperature in the kiln promptly and accurately. This not only helps us grasp the fire conditions in the kiln in real time, but also provides us with valuable data support. By carefully observing the changing trend of the temperature in the kiln, we can keenly judge whether the temperature is showing an upward or downward trend. This precise grasp of temperature dynamics is of crucial significance for subsequent external fuel addition decisions. It can provide us with a reliable basis to ensure that we add external fuel at the right time and in the right amount, thereby maintaining a stable temperature in the kiln and ensuring the firing quality of the product.
② In the process of adding external fuel, we must adhere to the principle of "watch the fire and add coal" and at the same time "add frequently and add less", that is, add small amounts and multiple times. This means that we need to accurately control the amount of fuel added based on the actual combustion rate of the fuel in the rotary kiln. This process requires us to avoid too little fuel, so as not to achieve the expected heating effect and affect production efficiency and product quality; we must also prevent too much fuel, because this will not only cause a waste of resources, but also cause fuel Incomplete combustion produces unnecessary smoke and pollutants, causing negative impacts on the environment and equipment.
③ During the operation of the rotary kiln, it is crucial to accurately grasp the calorific value of the fuel added to the kiln. We need to accurately add fuel according to the heat required in the kiln to ensure that the temperature in the kiln is stable and meets production requirements. If the calorific value of the new batch of fuel is higher than the calorific value of the original fuel, then we should reduce it accordingly when adding to avoid excessive heat causing excessive heat in the kiln. On the contrary, if the calorific value of this batch of fuel is low, we need to increase the addition amount appropriately to ensure that enough heat can be obtained in the kiln to maintain a stable temperature. Through such refined operations, we can better control the combustion process of the rotary kiln, improve production efficiency, and at the same time ensure product quality and stability.
④ When the ventilation volume of the whole kiln of the rotary kiln is too large, we need to take quick action to reduce the opening of each air damper to ensure that the entire firing zone can operate under positive pressure. This means that we need to allow backfire in each row of the burned zone to control the fire intensity. When necessary, we also need to strictly limit the air inlet volume at the bottom of the billet stack to reduce the impact of "back wind".
After completing the above adjustments, we should immediately start adding fuel frequently, especially dry fuels with lower moisture content, which can burn and release heat more efficiently. If the burning zone has been completely cleared, we need to add fuel with a higher calorific value to quickly increase the heat.
While waiting for the fire in the kiln to gradually return to normal, we must remain patient and continue to frequently add dry fuel with a lower moisture content to promote the development of the front fire. At the same time, we can gradually increase the opening of the air damper and ventilate the kiln to accelerate the fuel combustion process. Through such operations, we can ensure that the fire in the rotary kiln is stably controlled and the normal firing state can be restored smoothly.
⑤ When the ventilation volume of the rotary kiln is too small, in order to optimize the combustion environment, we should quickly adjust the strategy and increase the opening of each air damper. The purpose of this adjustment is to keep the entire firing belt in a suitable working state of positive and negative pressure. Specifically, the front part of the firing belt maintains negative pressure, while the rear part maintains positive pressure. This setting helps Achieve proper backflow of the flame, that is, backfire phenomenon, thereby improving the combustion effect.
In this state, in order to further improve combustion quality and heat exchange efficiency, we should focus on increasing the air intake volume of the thermal insulation zone and cold zone. In particular, ventilation at the base of the stack should also be significantly increased. This measure is crucial to promote the complete combustion of fuel and the effective transfer of heat. It helps ensure that the fire in the rotary kiln is stably controlled and provides a strong guarantee for the high-quality firing of products.
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