The charm and application of active lime
Active lime, with its unique high reactivity, plays a vital role in many industrial fields. In the steel industry, it is an important desulfurization and dephosphorization agent in the steelmaking process; in chemical production, it is used as a catalyst and raw material; in the field of environmental protection, it is the key to wastewater treatment. The reason why active lime is so “active” is due to its high specific surface area, low grain size and high porosity, which enable it to show excellent performance in chemical reactions.
The production process of rotary kiln
The lime rotary kiln, also known as the rotary kiln, is a furnace that calcines limestone in a cyclic manner. Its structure is similar to a giant cylinder, consisting of a furnace body, a ramp, a transmission device, a support wheel, a burner, a preheater, etc. After the limestone raw material is input into the furnace body from the ramp, it is heated and calcined and then discharged at the top. After condensation and cooling, it becomes finished lime.
The process of the lime rotary kiln is “preheating-calcination-cooling-kiln discharge”, and it is carried out in this cycle. Due to the addition of burners and preheaters, the calcination temperature is greatly increased, thereby greatly shortening the calcination time and greatly improving production efficiency.
The vertical kiln is another way to produce lime, and its structure is similar to a high chimney. The vertical kiln is mainly composed of a combustion chamber at the bottom and a calcination chamber at the top. There are multiple layers of limestone, coal, slag and other materials in the calcination chamber. By burning the coal at the bottom to produce high-temperature gas, the limestone is calcined into lime and extracted in the vertical direction.
The process of the vertical kiln is “adding coal-calcining-negative pressure ash discharge”, and the temperature in the calcination chamber can reach more than 1200℃. The structure of the vertical kiln is simpler than that of the lime rotary kiln, but the production efficiency is lower.
Comparison of the advantages and disadvantages of the two furnaces
1. Structure and process: The lime rotary kiln has a complex structure and fine process, while the vertical kiln has a simple structure and direct process.
2. Energy consumption and production efficiency: The lime rotary kiln has high energy consumption, but high production efficiency and large output; the vertical kiln has low energy consumption, but low production efficiency and small output.
3. Lime quality: The lime rotary kiln has a higher control accuracy on lime quality than the vertical kiln.
4. Environmental protection and safety: The addition of burners and preheaters in the lime rotary kiln helps to reduce carbon dioxide emissions, while the vertical kiln has greater pollution emissions during the combustion of coal; the calcining chamber of the vertical kiln is a vertical structure, which is at risk of tipping and collapse.
Overall, the lime rotary kiln and the vertical kiln have their own advantages and disadvantages, and should be selected according to actual conditions.
Production process of vertical kiln
1. Mixing of raw materials and fuel: Limestone and fuel (such as coke) are mixed in proportion.
2. Calcination: The mixture moves from bottom to top in the vertical kiln and is calcined by hot air blown in from the bottom.
3. Cooling and discharging: The calcined active lime is cooled naturally or by forced ventilation and then discharged.
Selection of refractory materials
Refractory materials are essential to ensure the normal operation of rotary kilns and vertical kilns. They need to withstand high temperatures, chemical erosion and mechanical wear. The following are the types of refractory materials commonly used in the two processes:
Rotary kiln:
1. Magnesia-chrome bricks: suitable for high temperature areas, with excellent erosion resistance and high temperature stability.
2. High alumina bricks: used in preheating and cooling areas, able to resist thermal shock and wear.
Vertical kiln:
1. Magnesia-carbon bricks: used in the combustion chamber and kiln bottom, providing good thermal shock resistance and erosion resistance.
2. Alumina silicate fiber: used for insulation layer, reducing heat loss and improving energy efficiency.
The production process and application areas of active lime are constantly expanding, and the selection of refractory materials directly affects production efficiency and product quality. Understanding and optimizing these process flows and selecting suitable refractory materials are the cornerstones for achieving efficient production of active lime.