What is the over burning rate of lime in a vertical kiln
Lime, as an important industrial raw material, has a wide range of applications in fields such as construction, metallurgy, and chemical engineering. Vertical lime kiln is one of the main equipment for producing lime, and the quality of lime produced directly affects the production efficiency and product quality of downstream industries. The raw firing rate is an important indicator for measuring the quality of lime, which reflects the degree of reaction of lime during the calcination process.
1、 Working principle of lime kiln vertical kiln
The vertical kiln of lime kiln is mainly composed of kiln body, feeding device, discharging device, combustion device, ventilation system, etc. Its working principle is to add raw materials such as limestone from the top of the kiln, and after high-temperature calcination in the kiln, the calcium carbonate in the limestone is decomposed into calcium oxide and carbon dioxide. After calcination, lime is discharged from the bottom of the kiln and cooled to obtain finished lime.
During the calcination process, factors such as temperature, time, and ventilation have a significant impact on the quality of lime. If the temperature is too high or the time is too long, it will cause lime to overheat, reducing the activity of lime; If the temperature is too low or the time is too short, it will cause lime to burn, causing the calcium carbonate in the lime to not completely decompose. Therefore, controlling the various parameters during the calcination process is the key to reducing the over firing rate and improving the quality of lime.
2、 The manufacturer's marked burn-in rate
Many lime kiln vertical kiln lime burning manufacturers will indicate in their product manuals or promotional materials that the over burning rate is less than 10%. This annotation is usually based on the manufacturer's production experience and technical level, as well as test results under ideal conditions. Manufacturers often consider the following factors when labeling the burn-in rate:
Raw material quality
High quality limestone raw materials are the foundation for producing high-quality lime. If the impurity content in limestone is low and the particle size is uniform, it is easier to control the temperature and time during the calcination process, thereby reducing the rate of overburning.
Equipment performance
Advanced lime kiln vertical kiln equipment has good temperature control, ventilation system, and discharge device, which can ensure the stability and uniformity of the calcination process, thereby reducing the rate of overburning.
Operational techniques
Skilled operators can adjust calcination parameters such as temperature, time, ventilation rate, etc. reasonably according to the characteristics of raw materials and production requirements, thereby reducing the rate of overburning.
However, the burnt out rate indicated by the manufacturer is only a reference value, and the actual burnt out rate in production may vary due to various factors.
3、 Burning rate in actual production
In the actual production process, the over firing rate of lime in vertical kilns is generally around 8%. This value was obtained through investigation and analysis of the actual production situation of multiple manufacturers. The main reasons why the actual production rate of over burning is lower than the manufacturer's label are as follows:
Changes in production conditions
The quality of raw materials, equipment performance, operational techniques, and other factors in actual production may differ from the conditions indicated by the manufacturer. For example, the impurity content in raw materials may increase, equipment may malfunction, and the technical level of operators may vary, all of which can lead to an increase in the rate of over burning.
The complexity of the production process
The production process of lime kiln vertical kiln is a complex physical and chemical change process, which is influenced by various factors. In actual production, it is difficult to fully control all factors, which can lead to fluctuations in the firing rate.
The strictness of quality control
In order to improve product quality and market competitiveness, many manufacturers adopt stricter quality control measures in actual production, such as strengthening raw material inspection, optimizing calcination parameters, and improving the technical level of operators. These measures can effectively reduce the over burning rate, making the actual over burning rate in production lower than the value indicated by the manufacturer.
4、 Factors affecting the rate of overheating
Raw material quality
(1) Chemical composition of limestone
The chemical composition such as calcium carbonate content and impurity content in limestone has a significant impact on the rate of overburning. If the content of calcium carbonate is high and the impurity content is low, it is easier to completely decompose during the calcination process, thereby reducing the rate of overburning.
(2) Particle size of limestone
The particle size of limestone also affects the rate of overburning. If the particle size is uniform and moderate, it is easier to transfer heat and react during the calcination process, thereby reducing the rate of overheating. If the particle size is too large or too small, it will lead to uneven heat transfer or insufficient reaction, thereby increasing the rate of overheating. Equipment performance
(1) Kiln body structure
The structural design of the kiln body has a significant impact on the firing rate. If the insulation performance of the kiln body is good and the ventilation is uniform, it will be easier to control the temperature and atmosphere during the calcination process, thereby reducing the rate of overburning.
(2) Combustion device
The performance of the combustion device can also affect the over burning rate. If the combustion efficiency of the combustion device is high and the temperature control is accurate, it will be easier to provide a stable high-temperature environment during the calcination process, thereby reducing the rate of overheating.
Operational techniques
(1) Calcination temperature and time
The calcination temperature and time are key factors affecting the firing rate. If the temperature is too high or the time is too long, it will cause the lime to overheat; If the temperature is too low or the time is too short, it will lead to lime burning. Therefore, operators need to adjust the calcination temperature and time reasonably according to the characteristics of the raw materials and production requirements, in order to reduce the rate of overburning.
(2) Ventilation rate
The size of ventilation also affects the rate of overheating. If the ventilation rate is too high, it will cause rapid heat loss, resulting in a decrease in temperature and an increase in the rate of overheating; If the ventilation rate is too low, it will lead to uneven atmosphere in the kiln, resulting in insufficient reaction and increasing the rate of overburning. Therefore, operators need to adjust the ventilation volume reasonably according to the actual situation inside the kiln to reduce the rate of overburning.
5、 Measures to reduce the rate of overheating
Optimize the quality of raw materials
(1) Strengthen raw material inspection
Strictly inspect raw materials such as limestone to ensure their chemical composition and particle size meet production requirements. For raw materials that do not meet the requirements, pre-treatment or supplier replacement can be carried out.
(2) Reasonably match raw materials
According to different production requirements, different qualities of raw materials can be reasonably matched to improve the overall quality of raw materials. For example, high calcium limestone and low calcium limestone can be combined to increase the calcium carbonate content of the raw materials.
Improve equipment performance
(1) Optimize kiln structure
Optimize the structure of the kiln body to improve its insulation performance and ventilation uniformity. New refractory and insulation materials can be used to reduce heat loss; It can increase the height and diameter of the kiln body, improve the volume and ventilation effect inside the kiln.
(2) Upgrade the combustion device
Upgrade and transform the combustion device to improve its combustion efficiency and temperature control accuracy. Advanced combustion technologies such as oxygen enriched combustion and heat storage combustion can be adopted to improve combustion efficiency; Temperature sensors and automatic control systems can be installed to achieve precise temperature control.
Improve operational skills
(1) Strengthen training
Regularly train and assess operators to improve their technical skills and operational abilities. The training content can include aspects such as raw material characteristics, equipment performance, calcination process, quality control, etc.
(2) Establish operating procedures
Develop detailed operating procedures to standardize the behavior of operators. The operating procedures should include methods for adjusting parameters such as calcination temperature, time, and ventilation rate, as well as maintenance and troubleshooting methods for the equipment.
(3) Strengthen quality monitoring
Establish a comprehensive quality monitoring system to monitor every aspect of the production process in real-time. Online detection devices such as temperature sensors and gas analyzers can be used to monitor real-time parameters such as temperature and atmosphere inside the kiln; Regular sampling and testing of products can be conducted to analyze their chemical composition and physical properties, identify problems in a timely manner, and take measures to make adjustments.
The over firing rate of lime in vertical kilns is an important indicator for measuring the quality of lime. The manufacturer's indicated burn-in rate is less than 10%, but in actual production, it is generally around 8%. The factors that affect the raw material burning rate mainly include raw material quality, equipment performance, and operating technology. In order to reduce the over burning rate and improve the quality of lime, measures such as optimizing raw material quality, improving equipment performance, and enhancing operational techniques can be taken. By implementing these measures, the production efficiency and product quality of lime kiln vertical kilns can be effectively improved, providing better support for the development of downstream industries.
