The calcination temperature range of environmentally friendly lime kiln
The calcination temperature of environmentally friendly lime kilns is a core parameter that affects the quality, energy consumption, and pollutant emissions of lime. According to industry practice and technical specifications, the calcination temperature is usually controlled within the dynamic range of 900-1250 ℃, which needs to be finely regulated based on kiln type, raw material characteristics, and environmental protection goals.
Lower temperature limit (900 ℃): This temperature can initiate the decomposition reaction of limestone (CaCO), but the decomposition rate is slow, which can easily lead to residual undecomposed calcium carbonate in the product and reduce the activity of quicklime. In actual production, the preheating section temperature is often set at 850-1050 ℃, and 30% of the raw materials are pre decomposed by waste gas heat, laying the foundation for subsequent efficient calcination.
The optimal range (1100-1200 ℃): This range is the golden window for complete decomposition of calcium carbonate. Taking a vertical kiln as an example, when the temperature in the calcination section is controlled at 1150-1250 ℃, the decomposition rate of CaCO3 can reach over 98%, the activity of quicklime is ≥ 320ml, and the overburning rate is ≤ 3%, meeting the needs of high-end fields such as metallurgy and chemical engineering. At the same time, by using oxygen enriched combustion technology to increase the oxygen content of the combustion air to 25%, the combustion efficiency can be improved by 15% and the amount of flue gas can be reduced by 20%.
Temperature upper limit (1250 ℃): Exceeding this value can easily cause the phenomenon of "overburning", leading to coarsening of quicklime grains, reduced specific surface area, and decreased hydration reaction activity. In addition, high temperatures will exacerbate the loss of refractory materials in the kiln body and increase heat dissipation losses. The modern environmental protection kiln reduces the heat loss of the kiln surface by 40% through the nano aerogel felt insulation layer, effectively alleviating the negative impact of high temperature.
Dynamic control strategy:
Partition temperature control: Adopting a five stage suspension preheater and forced air cooling, temperature gradient management is achieved in the preheating section, calcination section, and cooling section, with a comprehensive energy consumption of ≤ 115kgce/t, which is 25% lower than traditional processes.
Intelligent monitoring: Install 12 thermocouples inside the kiln to monitor the axial/radial temperature distribution in real time, automatically adjust the fuel quantity through PID algorithm, and achieve a temperature control accuracy of ± 20 ℃.
Waste heat utilization: Introduce the hot air from the outlet of the cooling machine into the combustion air pipeline, preheat the air temperature to 200-300 ℃, and reduce fuel consumption by 8-12%.
Environmental benefits: Precise temperature control can reduce NOx generation by more than 30%. Combined with a bag filter system, particulate matter emissions are ≤ 5mg/m ³ and SO ₂ is ≤ 20mg/m ³, meeting ultra-low emission standards. In the future, with the application of hydrogen calcination and carbon capture technology (CCUS), environmentally friendly lime kilns will further achieve zero carbon production and promote the green transformation of the industry.
