What are the reasons for the shortage of lime kilns
As a key equipment for lime production, the stability and efficiency of lime kilns are crucial for the production efficiency of enterprises. However, in the actual production process, there are often situations where the output of lime kilns is insufficient. This article will conduct an in-depth analysis of the reasons for the low output of lime kilns.
1、 Reasons related to raw materials
（1） Limestone quality issues
Low purity of limestone
If the content of calcium carbonate (CaCO3) in limestone is lower than normal, and the content of impurities (such as magnesium, silicon, aluminum, and other compounds) is high, it will require more heat to decompose the impurities during the calcination process, and the impurities may hinder the decomposition reaction of calcium carbonate. For example, when the calcium carbonate content in limestone decreases from 90% to 80%, the yield of lime may decrease by 5% -10% under the same calcination conditions.
Impurities may also affect the permeability of materials in the lime kiln, resulting in uneven heat transfer and further affecting production.
Uneven particle size of limestone
The significant difference in particle size of limestone may result in over calcination of smaller limestone particles during kiln firing, while larger limestone particles may not have fully decomposed. For example, limestone with large fluctuations in particle size within the range of 10-100mm may reduce production by about 8% compared to limestone with uniformly distributed particle size between 40-60mm.
Uneven particle size will increase the ventilation resistance inside the kiln, affecting gas flow and heat exchange, and reducing calcination efficiency.
（2） Fuel quality issues
Low calorific value
The calorific value of fuel is one of the important factors affecting the output of lime kilns. If the calorific value of the fuel used (such as coal, natural gas, biomass, etc.) is lower than the design requirements, then under the same fuel supply, the heat provided to the kiln will be insufficient, resulting in insufficient calcination of limestone. For example, using coal with a calorific value of 4000 kcal/kg instead of coal with a design calorific value of 5000 kcal/kg may reduce the output of the lime kiln by 15% -20% under other constant conditions.
High moisture content
If the moisture content in the fuel is too high, additional heat will be consumed during the combustion process for water evaporation, thereby reducing the effective heat used for calcining limestone. For example, increasing the moisture content in fuel from 5% to 15% may result in a 5% -8% decrease in lime kiln production.
2、 Equipment related reasons
（1） Structural issues with lime kilns
Poor sealing of kiln body
If the sealing of the lime kiln body is not tight, it will cause heat loss and the temperature inside the kiln will be difficult to reach the ideal calcination temperature. For example, if there are gaps at the connection between the kiln roof, kiln door, or kiln body, the heat loss may reach 10% -15% of the total heat, which in turn affects the yield. External cold air entering the kiln can also disrupt the airflow and temperature field inside the kiln, affecting the calcination effect.
The ventilation system is unreasonable
Insufficient or uneven ventilation can result in insufficient oxygen supply and incomplete fuel combustion in the kiln, thereby reducing heat generation. For example, when the ventilation volume of the ventilation system design is 20% less than the actual demand, it may lead to a decrease of about 10% in production.
Unreasonable ventilation may also lead to localized high or low temperature areas inside the kiln, resulting in uneven calcination of limestone.
（2） Equipment aging and malfunction
Damage to combustion equipment
If combustion equipment such as burners and nozzles are damaged, blocked, or worn, it will affect the normal injection and combustion efficiency of fuel. For example, after the nozzle of the burner wears out, the atomization effect of the fuel deteriorates and the combustion efficiency decreases, which may lead to a 5% -10% decrease in production.
Damaged combustion equipment may cause irregular flame shapes and prevent uniform heating of limestone.
Transmission equipment malfunction
If the transmission device of the lime kiln (such as motor, reducer, gear, etc.) malfunctions, it will affect the normal rotation of the kiln body or the transportation of materials. For example, motor failure can cause unstable kiln speed, which may result in inconsistent calcination time and heating degree of limestone in the kiln, reducing production by 8% -12%.
3、 Reasons for operational processes
（1） Improper control of calcination temperature
Low temperature
If the calcination temperature is lower than the optimal temperature range for limestone decomposition (usually 900-1200 ° C), it will slow down the decomposition rate of limestone and result in incomplete calcination. For example, if the temperature is maintained at around 800 ° C for a long time, the yield of lime may only be 60% -70% of the normal yield.
Low temperature calcination may also lead to a decrease in the activity of lime, affecting product quality.
The temperature is too high
Although high temperatures can accelerate the decomposition rate of limestone, excessively high temperatures (over 1200 ° C) may cause lime to overheat, resulting in agglomeration and affecting the normal flow of materials in the kiln, thereby reducing production. For example, when the temperature exceeds 1300 ° C, it may cause nodules in the kiln and reduce production by 5% -8%.
（2） Unreasonable calcination time
The calcination time is too short
If the calcination time is not sufficient to completely decompose limestone, it will result in residual undecomposed calcium carbonate in the lime, reducing yield and quality. For example, if the calcination time is 2-3 hours less than normal, the yield may decrease by 10% -15%.
The calcination time is too long
Excessive calcination time not only wastes energy, but may also cause lime to overheat and reduce production. For example, if the calcination time exceeds the normal time by 3-4 hours, the yield may decrease by 5% -10% due to overburning.
4、 Other factors
（1） Environmental factors
climate change
The significant change in temperature will affect the heat dissipation of lime kilns. In winter, when the ambient temperature is low, the heat dissipation of the kiln body accelerates, requiring more fuel consumption to maintain the temperature inside the kiln; In summer, the ambient temperature is higher and the heat dissipation is relatively slower. For example, in winter in the north, temperatures may drop below minus 20 ° C. Compared to summer, maintaining the same kiln temperature may require an increase in fuel consumption of 10% -15%, otherwise production will be affected.
Changes in air pressure
The level of air pressure can affect the efficiency of the ventilation system. When the air pressure is low, the air density decreases, and the ventilation volume will correspondingly decrease, affecting fuel combustion and gas flow inside the kiln. For example, in areas with lower air pressure or weather conditions, ventilation may decrease by 5% -10% compared to normal air pressure, resulting in a decrease in production.
（2） Human factors
Low skill level of operators
Operators lack sufficient understanding and experience in the operating principles and process parameter adjustments of lime kilns, which may lead to operational errors. For example, the inability to adjust parameters such as fuel supply and ventilation in a timely manner based on the situation inside the kiln can affect production.
Operators have a weak awareness of equipment maintenance and upkeep, and are unable to promptly identify and address potential issues with the equipment, which can also affect the normal operation and output of the lime kiln.
In summary, the low output of lime kilns is the result of multiple factors working together. In the actual production process, it is necessary to conduct comprehensive inspections and analyses of raw materials, equipment, operating processes, environment, and personnel, identify problems, and take corresponding measures to improve and optimize, in order to increase the output and production efficiency of lime kilns.
