What is the temperature for calcining lime in a lime kiln
In the production process of lime, lime shaft kiln, as a common calcination equipment, plays a crucial role in controlling the calcination temperature for the quality and yield of lime. Understanding the temperature range for calcining lime in a lime kiln can help to better grasp the lime production process, improve production efficiency and product quality.
1、 Overview of Lime Kiln
Lime shaft kiln is a vertical kiln structure used to calcine raw materials such as limestone into lime. It usually consists of a kiln body, a feeding device, a combustion system, a discharge device, and a ventilation system. Lime shaft kiln has the advantages of simple structure, convenient operation, and low investment cost, and is widely used in small and medium-sized lime production.
2、 The temperature range for calcining lime in a lime kiln
The temperature for calcining lime in a lime kiln is generally between 800-1200 degrees Celsius. This temperature range is determined based on the decomposition characteristics of limestone and the quality requirements of lime.
Below 800 degrees
Below 800 degrees, the decomposition rate of limestone is very slow. Although a small amount of limestone may decompose at lower temperatures, the decomposition is incomplete, resulting in poor quality and low activity of the generated lime. In addition, low-temperature calcination can also slow down the airflow velocity inside the kiln, affecting the ventilation effect and increasing energy consumption.
800-1000 degrees
When the temperature reaches above 800 degrees, limestone begins to decompose rapidly. Within this temperature range, the decomposition reaction of limestone is more intense, resulting in high-quality and highly active lime. At the same time, the airflow velocity inside the kiln is moderate and the ventilation effect is good, which is conducive to heat transfer and limestone decomposition.
1000-1200 degrees
At high temperatures of 1000-1200 degrees, the decomposition rate of limestone further accelerates and can almost completely decompose. At this point, the quality of the generated lime is very good, with high activity and strength. However, excessively high temperatures can also cause some problems, such as increased wear of refractory materials in the kiln and increased energy consumption. Therefore, in actual production, it is necessary to choose the appropriate calcination temperature according to the specific situation.
3、 The influence of temperature on the quality of lime
activity
The activity of lime is one of the important indicators for measuring its quality. Generally speaking, the higher the calcination temperature, the higher the activity of the generated lime. This is because at high temperatures, the decomposition of limestone is more thorough, resulting in a looser crystal structure and a larger specific surface area, thus possessing higher activity.
strength
The calcination temperature also affects the strength of lime. Within an appropriate temperature range, as the temperature increases, the strength of lime will gradually increase. However, if the temperature is too high, lime will experience overburning, leading to densification of the crystal structure and a decrease in strength.
Impurity content
The calcination temperature also affects the impurity content in lime. At high temperatures, some impurities will react with limestone to produce compounds with low melting points, thereby reducing the purity of lime. Therefore, when choosing the calcination temperature, it is necessary to consider the influence of impurities and minimize the content of impurities as much as possible.
4、 Methods of temperature control
Fuel selection
Different fuels produce different temperatures during combustion, so choosing the appropriate fuel can effectively control the calcination temperature. For example, fuels such as natural gas and heavy oil generate high temperatures during combustion, making them suitable for high-temperature calcination; The temperature generated by the combustion of solid fuels such as coal is relatively low, making it suitable for medium to low temperature calcination.
Ventilation control
Good ventilation can ensure sufficient oxygen supply in the kiln, promote fuel combustion, and increase temperature. At the same time, ventilation can also take away the exhaust gas and heat inside the kiln, and regulate the temperature distribution inside the kiln. Therefore, by controlling the ventilation volume and method, the calcination temperature can be effectively controlled.
Kiln structure design
Reasonable kiln structure design can improve the heat transfer efficiency inside the kiln, evenly distribute temperature, and thus better control the calcination temperature. For example, adopting a multi-layer insulation structure and setting the burner position reasonably can improve the temperature stability inside the kiln and reduce temperature fluctuations.
The temperature for calcining lime in a lime kiln is generally between 800-1200 degrees Celsius. This temperature range is determined based on the decomposition characteristics of limestone and the quality requirements of lime. In actual production, it is necessary to choose the appropriate calcination temperature according to the specific situation, and effectively control the temperature through methods such as fuel selection, ventilation control, and kiln structure design. Only in this way can high-quality lime products be produced to meet market demand.
