The 5000t/d rotary kiln of a clinker branch company of a cement company often has material leakage at the kiln end, which seriously affects the output and quality of the rotary kiln, causes unnecessary environmental pollution, increases the labor intensity of on-site employees, and severely restricts production. In response to this situation, the company organized technical personnel to conduct multiple analyses, and finally took measures to solve the problem.
Cause Analysis and Process Operation Adjustment
In the early stages of the leak, only the operation of the rotary kiln was analyzed as there was not enough time to inspect the kiln. Because the kiln speed is slow, the tertiary air is small, the ventilation in the kiln is too large, the material flow rate is slow, the filling rate in the kiln is too large, the auxiliary kiln skin and the back ring in the kiln. In addition, the effect of fluctuations in the composition of the raw materials caused the leakage.
Adjust the above analysis accordingly:
(1) Increase the kiln speed when the kiln bar allows, and use the thin-material fast-burning calcination method. The higher the kiln speed, the lower the material filling rate in the kiln, and the kiln tail is not easy to leak. At the same time, after the kiln speed is increased, the re-adhesion force of the material on the kiln skin is reduced, the thickness of the kiln skin is reduced, and the kiln skin is prevented from becoming thicker and thicker.
(2) Adjust the tertiary air valve to ensure the reasonable distribution of the air in the kiln and the tertiary air. Open the tertiary air valve to reduce the ventilation in the kiln, ensure that the material enters the kiln quickly, reduce the resistance of the material in the kiln, speed up the flow of material, and reduce the filling rate in the kiln. The adjusted parameters are shown in Table 2.
Table 2 Adjusted technical parameters
(3) Adjust the coal injection pipe at the kiln head, and adjust it alternately and repeatedly, so that the auxiliary kiln skin and the rear ring in the kiln collapse automatically due to the alternating changes of cold and heat.
(4) The limestone MgO content used by the company is generally high and fluctuates greatly, and the clinker content is about 4.2%~4.9%. When MgO is high, if the calciner continues to maintain the normal calcination temperature, it is easy to cause excessive liquid phase and ring formation, resulting in leakage at the kiln end. Therefore, when MgO is high, the combustion temperature should be appropriately reduced, the iron and aluminum content should be reduced, and the KH and SM values should be appropriately increased to alleviate the leakage at the kiln tail.
(5) During operation, the amount of coal should be adjusted in time according to the kiln conditions and the fluctuation of ingredients to avoid excessive coal amount at the kiln head, resulting in excessive deposition of coal ash in the kiln, uneven mixing of clinker, and ultimately abnormal working conditions (such as circles) . It is strictly forbidden to control the temperature at the outlet of the calciner to be too high to avoid the liquid phase appearing in advance.
After the above adjustments, the phenomenon of material leakage at the kiln tail has been improved, but it still occurs occasionally, and the problem has not been fundamentally solved.
Inspection and Treatment in Shutdown of Kiln for Maintenance
During the maintenance of the kiln, the company organized relevant personnel to conduct a careful inspection of the kiln. During the inspection process, it was found that most of the tongues at the end of the kiln were burnt and shortened, and in severe cases, only the roots were fixed by screws. According to this situation, this may be the main reason for the leakage of the kiln tail.
In view of the above situation, the blanking tongue was replaced during the overhaul, and the castables on both sides of the blanking tongue and the blanking slope were rebuilt. All the fish scales and locking wires sealed at the end of the kiln are replaced.
After the last targeted maintenance of the kiln tail leakage, there was no kiln tail leakage in the initial stage of normal production, but at the initial stage of the rotary kiln feeding, especially when the cylinder was running at the lower limit and low kiln speed, the kiln tail still remained. There is leakage. In this regard, the company inspected the situation in the kiln and found that the blanking tongue was not seriously damaged, the lifting plate was not seriously worn, and there was no similar leakage phenomenon in the previous production under the same circumstances. In response to this phenomenon, it was decided to transform on the basis of the original equipment to improve the ability of the kiln to transport materials. Refer to the relevant drawings for measurement, install a feeding plate between the blanking tongue and the kiln barrel, the installation length is 2/5 of the circumference of the kiln barrel, the installation welding position is the material side of the front end of the smoke chamber, and the width of the feeding plate is 130mm. Machined from 8mm thick heat-resistant steel. After adding the feeding plate, in the abnormal condition at the initial stage of feeding, when there is a lot of material at the kiln end, the material will not leak directly, and the material will be introduced into the lifting plate along the feeding plate, reducing the possibility of direct outflow.
After the above treatment, there is no kiln tail leakage phenomenon in the initial stage of normal production and feeding.
To sum up, reviewing the whole process of kiln tail leakage treatment, we analyzed that the root cause of kiln tail leakage is the accumulation of kiln tail materials, which exceeds the maximum amount of materials that can be transported under the kiln conditions at that time, resulting in kiln tail leakage. In order to solve the problem of leakage at the kiln tail, it is necessary to adjust the process parameters and ingredients, scientifically transform the process equipment, and improve the material transportation at the kiln tail as much as possible to avoid leakage at the kiln tail. In a word, there are many reasons for the leakage of the kiln tail. Various factors should be considered in the analysis and treatment. According to the actual situation, take the right medicine to stabilize the kiln working conditions and realize the stable and continuous operation of the rotary kiln.