Dolomite Calcination Plant

• Rotary kiln temperature: An experiment once showed that the recovery rate of dolomite at 700°C in the rotary kiln was low, only 20%. This may be because the material is still in the heating zone. After all, the feed material enters the rotary kiln at room temperature. Therefore, at a rotary kiln temperature of 700°C, a part of the rotary kiln only heats the feed, and when calcination begins to occur, the feed material has begun to enter the outlet of the rotary kiln. At higher temperatures, such as 900°C, the material feed is preheated faster, resulting in a higher calcination recovery rate. The higher the temperature of the calcination reaction, the higher the conversion rate of the reaction. As the temperature increases, the reaction rate also increases, thereby increasing the conversion rate of calcination. Calcination temperature is one of the key factors affecting the calcination effect of dolomite. An appropriate calcination temperature can promote the release of CaO and MgO in dolomite from the dolomite structure, thereby increasing its activity. Studies have shown that the optimal calcination temperature is generally between 1000 and 1200°C, at which time the activity of dolomite reaches the best state. When determining the calcination temperature, it is necessary to comprehensively consider quality requirements and economic benefits, and conduct experimental verification to determine the optimal temperature range.‌

• Dolomite particle size: In the past, an experiment was conducted at a rotation frequency of 29.75 rpm, an inclination angle of 3°, and a temperature in the rotary kiln at 700°C, 800°C, and 900°C. It can be seen that as the particle size decreases, the conversion rate increases. This is consistent with the theory that a decrease in particle size of the same mass will increase the overall surface area of the dolomite particle. The increase in surface area leads to an increase in the heat transfer rate, resulting in a greater increase in heat for the same residence time. As the heat increases, more particles reach the required activation energy and are converted into calcium oxide and magnesium oxide. Compared with temperature, particle size has less effect on conversion rate because the rotation of the rotary kiln helps to evenly distribute the incoming heat to all particles in the kiln. However, it is undeniable that too large particle size of dolomite will lead to uneven calcination, while too small a particle size may increase the difficulty of calcination. The appropriate particle size can improve calcination efficiency while ensuring calcination uniformity. The recommended particle size range for the study is 15~30mm. The particle size within this range can not only ensure calcination uniformity but also improve calcination efficiency.

• Calcination time: Calcination time is also an important factor affecting the calcination effect of dolomite. Too long or too short calcination time will lead to a decrease in stone quality. Too short calcination time may lead to incomplete calcination, while too long calcination time may lead to over-calcination, the grain growth of oxides (CaO.MgO), and the surface will age and lose activity, affecting the quality of dolomite. The appropriate calcination time can fully release CaO and MgO while avoiding over-calcination. It is generally recommended to be between 1 and 4 hours. Therefore, in production, for the calcination of dolomite, whether it is a rotary kiln, a vertical kiln or other kilns, a slow heating and high-temperature rapid calcination method should be adopted. In addition, the calcination rate is also one of the factors affecting the calcination effect of dolomite. Too fast a calcination rate may cause uneven temperature inside the dolomite, resulting in cracking or other quality problems. Therefore, in order to ensure the quality and consistency of the stone, it is very important to control the calcination rate.

Finally, the factors affecting the calcination of dolomite also include the chemical composition, structural characteristics, initial state, etc. Dolomite of different types and regions has different chemical compositions and structural characteristics. Therefore, for different raw materials, the calcination process parameters may need to be adjusted. In addition, the initial state of dolomite (such as moisture content, particle size, etc.) will also affect the calcination effect.

The optimization of calcination process parameters is crucial to the quality and performance of the dolomite. By reasonably adjusting the calcination temperature, calcination time, and calcination rate, the color of dolomite can be changed, the hardness can be improved, and the durability can be increased. In practice, customers need to determine the best process parameter range according to their different needs. At the same time, it is also necessary to pay close attention to environmental protection and energy consumption issues during the calcination process to make the dolomite calcination process more sustainable and environmentally friendly.